Nikola Tesla's Plan To Keep Wireless Thumb On Ship's At Sea

Sunday, November 9, 1913
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~ ." 36 THE ELECTRIC JOURNAL belts, it would be necessary to run alternators at a low speed for direct connection to engines. This made desirable a less number of poles than would be neces- sary for the high frequency, for instance, at too r.p.m. x60 poles would be necessary. Furthermore, the in- duction motor operated much more satisfactorily at a low frequency. V In the fall of 1890 Mr. Stillwell returned from a visit to Europe. He had seen alternators direct.con- nected to slow-speed engines. After carefully study- ing the American situation he prepared a report on which the subsequent engineering policy of the com- pany was based, in which a frequency of 60 cycles was proposed as a general standard for lighting ser- vice and 30 cycles for power service. The higher fre- quency met the requirements of engine speed; it per- mitted transformers to be made at reasonablevcost (the cost increased as the frequency was lowered) and it was high enough to permit the operation of arc lamps without Hicker, with American carbons. Abroad s XF; 7, //..,.»e=.3.x....r e¢.,,¢.:,, 4 '°£...,..& #W J; ¥‘;§“*/ M. Maw i 1. ., gt smears 4,\...,..,Z;._ l .r’ v .ra sauna. Yr Qui PP i=\i‘»"5#' uiit?w. -Q I //~ ¢ _'L /./ ;r'vf fr) j-..~4,t::.. . r ea;-I eggs yrs A#...1/.Ai-.Ann a J N( 1 ;... Juaar *VV @3234 a.4\»a1u-.J‘.» .rr.f1.a...4» 4' a.r=uL/L... :Fwd _ ma.. ».<. ,.2.tI __ °'" .» ..,.-.,.~; aauauf '#=/.1..r~; N j'~`l_`-.itf 4.-./...4.1;\. 1.5 > - . ' ' rfr'»=' YW - }`»~= ~ 17%-if" ` ' ’ ` ~`-‘fl `[ 3-' iv '~.'=-* W . v /__ 1) .~. _ . ‘J Z _:EJ Lv ji ,/.__ |_»_; ‘ ' 1 _ -~ - --»- = fr* ..m%`i+ ' l - ' * ' ' ' _-1 ` __ _ ,‘ ’ '- _"' 1' ,,§Y"§i;3‘ff{§,;--ey » V , ;___'- ` _ 'ii; . _,L_-f&_,,rl"i iiwiy' " 1»~. - /~..' ' ag ' " .'1‘”"~»- J *ij ‘” 9 as . 0). 3. J nd ., 4... H r S ils g Y ' ¥°‘<‘-»--=>-""f".` .` r if ‘J _.amass W. rro. I4_PllIC! usr, 1889 This list, torn from an ordinary note-book, included prices, not only on all types of apparatus manufactured by the company, but on all the ratings of each type. soft carbons permitted a slightly lower frequency. The lower frequency of 30 cycles seem a desirable one _from the standpoint of the induction motor and power work generally. In 1892 an exhibition of alternating apparatus was made at Pittsburgh which was viewed by Prof. George Forbes of England, Prof. Henry A. Rowland and Dr. Coleman Sellers members of the commission for determining the system to be adopted by the Niagara Falls Power Company. They were shown rotary converters operating at 30 cycles. The matter of frequency was discussed. The effect on in- candescent lamps was determined to be unobservable at 30 cycles, very pronounced at 20 cycles and some- what in question at 25. Prof. Rowland remarked that the way to make a test was to have some old woman read by the light and note whether or not her eyes be- came tired. This seemed a remarkable statement from the leading physicist of America with regard to what seemed to be a physical phenomenon, but after all it is hot physical condition but physiological effect that is of importance. The commission of American and foreign engineers which determined .the system to be used at Niagara was at first in favor of direct current by a considerable majority. The final decision in favor of alternating current was not made until the sum- mer of 1893 when polyphase alternating current was choosen and a little later 25 cycle alternators of 5 ooo horse-power, delivering two phase current were purchased from the Westinghouse Company. The de- sign of the alternators favored either a I2 pole or a I6 pole alternator. The water turbines had been pur- chased; they ran at 250 r.p.m. Hence the choice lay between 25 and 33 r/ 3 cycles and it was impossible to secure 30 cycles. The I2 pole machine giving 25 cycles was chosen. This was a notable event. The adoption' of polyphase alternating current and the use of 25 cycles by the largest power undertaking of the time set a precedent which is now almost universally followed. Frequencies of 40 and 50 and 66 cycles have been ad- vocated and used, but (with few exceptions) are now obsolete. 'rms IMPORTANCE or 'rRANsFoRMER AND 1=oLY1>HAsa system In the early days, say from 1880 to 1895, there were many systems and many types of apparatus. This is well illustrated by one station which had ma- chines for arc lighting at 6.6 amperes, for are light- ing at I0 amperes, for incandscent lighting by the three-wire system, for power by 500 volts direct cur- rent, and for incandescent lighting by alternating current. Each kind of service required its own in- dividual circuits_ and the are lighting required indi- vidual circuits from each machine. Subsequently current for all kinds of service was derived from al- ternators far greater in capacity than a score of the former machines. If we were to trace the electric development of the past twenty-Five years, we should Find the trans- former as the simple factor which has determined the whole course of that development. With few ex- ceptions in which direct current from relatively small plantsis used locally, practically all of the elec- tric energy now used for lighting and for power pur- poses passes through one or more transformers. A second-afactq in shaping the course of elec- trical development was the Tesla motor and the poly- phase system. To accommodate the motor with a proper supply of current, single-phase generators gave way to polyphase alternators, and high frequency was followed by low. The Tesla invention proved to be not merely a motor, as was first assumed, but a system. Polyphase apparatus is now prahtically uni- versal. All of the long distance systems of power transmission and practically all of the great central stations for street railway and lighting 'and power service produce polyphase alternating current, even when the consumption circuits require direct current. When the polyphase system was first introduced# the parallel operation of alternators was unusual, but it is now universal.

32 THE ELECTRIC JOURNAL 1888 were of Five sizes, viz., of 5, Io, zo, 30 and 40 lamps the largest size being two kilowatts though the term kilowatts was not applied to them for several years. The transformers were wound for a pri- rnary e.n1.f. of 1 ooo volts and 50 volts secondary in most cases while a few were wound for loo volts, usually with a tap at the middle point. The coils were separately wound and taped; they were ap- proximately square in cross-section, so that the open- PARALLEL COILS CONCENTRIC COILS FIG. 5-FORMS UF COILS IN EARLY TRANSFORMERS In parallel form the magnetic leakage between coils is considerable as there is a short wide path compared with that in the later concentric form, which therefore had much im- proved regulation. ing in the iron was approximately a double square. The accompanying illustration shows such a trans- former built up. Bare lead fuses, either wire or links, were placed between brass terminals on fibre bases in iron boxes on the case. Materials and con- struction of this sort would be w-holly inadmissable today, though they were fairly satisfactory with the lesser currents, the lower e.m.f.s and the smaller generators which were ‘then employed. One of the dithculties with these transformers was the large drop in secondary voltage between no load and full load. This drop was partly caused by the resistance of the windings and partly by some- thing else which was termed “drop due to iron.” The latter was hard to measure accurately, as it seemed to vary from time to time. This factor was of serious importance when incandescent lamps con- stituted the only load, and it rose to very disagree- able proportions when there was a lagging current or, in modern terms, when the power-factor was low. The fact that the square coils were placed side by side in parallel form permitted a considerable mag- netic leakage between the coils, the effect of which was very pronounced with the frequency of 133 cycles. The first modification in the transformer was to change the form of the coils, making them con- centric by winding each coil with approximately twice the number of turns per layer and half the number of layers. This changed the path for the magnetic leakage, making it about twice as long and of one-half the cross-section that it was in the former arrangement, thereby improving the regulation. The testing of transformers consisted of an in- sulation or a ground test and a running fest. If the insulation was sufficient to prevent enough current from flowing through the primary of another trans- former to light a lamp on its secondary, it was con- sidered adequate. In other words, the insulation test was really made at an of 1 ooo volts or less. The running test was made by coupling transformers in parallel to a large bank of lamps and running them for several -hours. AUXILIARY APPARATUS W-hile the generator and the transformer were the essential apparatus in -the alternating system, vari- ous auxiliaries were necessary to make the system operative, such as switches, fuses, measuring instru- ments and the like. Past experience was limited to low voltage, direct-current service and to arc light circuits. Auxiliaries for alternating current and for I ooo volt use had to be devised quickly. In the light of present knowledge they were simple _and almost rudimentary, On the other hand, when one considers the limited experience there was to guide and the necessity for producing these instruments quickly, one cannot but admire the results. To Mr. Shallen- berger and to Mr. Philip Lange, who was in charge of the construction of detail apparatus, belongs this credit in large measure. A number of points relating to this detail apparatus are of interest. The rheostats had wooden face plates back of which were mounted wooden frames holding spirals of German silver wire. The switches for the switchboards employed wooden bases and the contacts were open and ex- posed. Double-pole, double-throw switches were ordinarily employed for connecting a dynamo or an "`-‘““ , 1 .i | ' _»°~-f~~`9- _ ‘- t “i " "" ~. " 7. ;` is , VY i i ' ` 'Q , ; Z, ‘JT f~-‘~ -,;;- ~ 1 » » ._ i ,if- §;_ ' f =» ,_;,_ _ . i r<-ss.. .£'_f, f?"~< i 1 _ ` -» `f ‘< . L -` if l , at *- \<- 1 2 .511 .\ ‘Li i ,___ -_ - \, '|» 1 i, ;, 5 , ~-s.,;,.,»' , -__`__l ,- / ' -i. g 'pi ,;.._ M/ ,» Li? _ , 'i ; - , . “» . -av; ~» i i . A <1-»., _.sig ' .;:;-:;».-.‘r~».»Z§>"< V ..,af‘m-,L illéfi nc. 6-FIRST'SHALL`EN%J`tGD1 ALTERNATING-CURRENT Mari-:R "The current passes through the main coils, creating a Held through the coils at right angles to the back of the meter. Within the main coils is a secondary made of copper punchings which is placed at an angle of about 45 degrees with the main coils, thereby creating a magnetic field dis- placed by 45 degrees from that of the main coils, The sec- ondary current and its magnetic Field lag behind those ofélhe II1 and the the the the main coils. In the space occupied by both fields is a aluminum disc supporting a small iron ring. This ring disc revolve. The motion is retarded by fan blades at bottom of the meter. The torque is proportional to square of the current and the speed is proportional to gurlrept, and the number of revo utions is registered on ia s. outgoing feeder to either of two sets of bus-bars. The transfer was made by throwing the switch quickly, resulting in only a momentary interruption of the circuit.

76 THE ELECTRIC JOURNAL over the top of the armature tooth, as shown in Figs. 6 and 7. This made the coil considerably wider than the body of the armature tooth, so that, after slipping over the tooth top the coil had to be reduced in width by special clamping tools. Supporting wedges were then driven in between adjacent coils. Something may be said regarding the tempera- tures of these early alternators, both of the surface- wound and of the toothed types. In those days tem- perature measurements \vere very crude compared with present practice, which is admittedly still only approximate. In some of the surface-wound arma- tures excessively high temperatures must have beenen- countered in many instances, judging from the appear- ance of the insulation on the individual wires, after a year’s service, for instance. However, it was dith- cult to obtain reasonably correct temperature of the armature windings, for the 'actual temperature of the conductors was undoubtedly reduced very greatly be- fore the armature could be brought to a standstill. Even after this, temperature rises of 50 or 60 degrees C. were not considered as excessively high. Without doubt, some of these early machines, at times, attained actual internal temperatures of X20 to 130 degrees C., -or even higher, with insulation on the conductors con- ll. \ ~ _ .ul § ll \_ ,I If ‘ 1 FIG, 6-SKERIH SHOWING METHOD OF PUTTING MACHINE WOUND COILS ON THE POLES sisting of untreaded cotton fibre. No overloads were possible, for each size of machine was rated in as many "lights" as it could carry on a shop test without breaking down. The First few minutes, while starting up a new alternator in the testing room, were always anxious ones for the operators, especially so if any "improven1ents” had been made on the armature wind- ing. Any deiect in winding, or wrong connection usually resulted in a stripped armature and much 'flying copper. If nothing happened within the first few minutes after the machine was put on load, the :attendants all came out from behind posts and other 'protections and went on with their work. When the toothed armature came into use the above conditions were much alleviated. Defects in construction, or short-circuits, could not strip such armatures, and thus the danger and excitement were -removed However, it was found -that the first short run did not tell the story of excessive heating as promptly as in the case of the surface-wound type. Experience showed that the toothed construction ap- parently could stand a severe shop test and still go wrong under similar loading within a short time after being installed. It was found that a given size of con- ductor would not carry as much current in the con- centrated coils of the toothed construction as was the case in surface-wound coils. However, the method of testing the temperature did not show this, as the main part of .the toothed armature coil was so embedded and so covered with insulation that the thermometer readings did not indicate nearly the true temperatures. The size of wire and the amount of copper in the coils then had to be increased until tl1e machines did stand up in service. The true explanation of the dis- crepancies was not well understood at that time. In these toothed alternators, as in the surface-wound ma- chines, the Hrst machines were rated in "lights," but gradually the kilowatt rating came into use and be- came standard practice. INTRODUCTION or Ponvrnase A1.r|3RNA'ro11s In 1892 and 1893, polyphase alternators began to be considered seriously. In 1889 and 1890, a few such altematons had been built for the operation of Telsa induction motors. These early polyphase alternators \vere oi the surface-wound., rotating armature type. These machines were very special in construction, and, like the Telsa motors, did not find much oi a mar- ket. However, in 1892 and 1893, it began to be recog- nized that the best way to encourage the development of the induction motor would be by creating a demand _.ft ;~ --'wtf' ~'“<.~.= -f #nn '.s'~Zf»'7.».>"::5f-if ~:- ‘-';' 'rfi-' ft? i.i.r_aQ.¢;&;- , . ,_ , 12- "rifle p WI; \ V W5 T "<""' it ;§°.>l:1;‘.»" x_ _ _ _ u \-» > __, 6 W i' h = 5' I-.:Z7”" .4 . . . M -~ - ~ »-.M liter -4f= ~=="J‘»'2-," " it -T, ~"'f1-:;;‘ “*j?l~'Y;itJ=.?, f .=.:,i;.l ;1=tv»‘ " ~ s:,Q=x¢'~‘f§; _ ` rff I 1,' , `n‘ _J , _ ?` _ 5 " .t ._ ' ..... H _ FIG. 7-~VIE\V UF ARMATURE IN PROCESS OF PLACING CDILS AND CLAMPING THEM INTO SHAPE IN THE SLDTS for it, and it was decided that a good way to create a demand would be by encouraging the general adoption of polyphase alternators and supply circuits, with the idea that, when a suitable supply circuit was available, there was eventually bound to be a demand for motors to operate upon such circuits. With this general policy in view, there was great activity in the development of polyphase generators. This very quicky led to a very considerable departure in armature construction from the usual -toothed armature as used in single- phase machines. The polyphase winding, requiring two or more coils per pole, naturally tended toward the slotted armature construction with two or more slots per pole. It was soon recognized that, in gen- eral, the larger the number of slots per pole and the smaller the number of conductors per slqt, the better would be the general characteristics of the machine, so that the construction naturally tended toward the modern slotted type. Moreover, practically all the de- velopment in polyphase alternators was at' relatively low frequency, compared with former practice. It so happened that there had been a well-defined tend- ency toward lower frequency in the period from i899 to 1892. This tendency was largely independent.

38 the pu\\'|\r of the trnuslnittcr is dissi|mtcilili|-< I'--r 1-ln-1>l\'i<>»ll :\|\1~li\'nli1\|w. lli,f:l|-l`|'r‘~N~\\wy |»\||'i'c||ls 1>spvri:\l|y l|:\\1~ :i grl-nl flllure. 'l`lxc time will cuinxc when this forin ul' clcclricnl energy will be availaible in every private rcsidcncc. I consider MANUFACTURERS RECORD. it quite possible that through their surface actions we may do away with the customary hath, as the cleaning nf the body can he instantaneously effected simply by connecting it to 1| smlrcu of currents or electric energy of very high potential, \vhich results in the throwing olI of dust or any small particles adhering to the skin. Such a dry bath, besides being convenient and time-saw ing, would also be of benedcial therapeutic influence. New electric devices for use of the deaf and blind are coming and will he a blessing to the afflicted. In the prevention of crime electrical instruments will soon become an important factor. In court proceedings electric evidence will often be decisive. In a time not distant lt wlll be possible to flash any Image formed ln thought on a screen and render lt vlslble at any place desired. The perfection of this means of reading thought will create a revolution for the better in all' our social relations. Unfortunately, it is true, that cun- ning lawhreakers will avail themselves of such advan- tages to further their nefarious business. Telegraphic Photography and Other Advances. Great improvements are still possible in telegraphy and telephony. The use of a new receiving device which will be shortly described, and the sensitiveness of which can be increased almost without limit, will enable telephoning through aerial lines or cables how- ever long by reducing the necessary working current to an infinitesimal value. This invention will dispense with the necessity of resorting to expensive construe tions, which, however, are of circumscribed usefulness. It will also enormously extend the wireless transmission of intelligence in all its departments. The next art to he inaugurated is that of picture transmision by ordinary telcgraphic methods and exist- ing apparatus. This idea of telegraphing or telephon- ing pictures is old, but practical difficulties have ham- pered commercial realizations. A number of improve- ments of great promise have been made, and there is every reason to expect that success will soon be achieved. Another valuable novelty wlll be a typewriter eleotrlcally operated by the human volce. This sd- vance will fill n long-felt want, as it will do away with the operator and save a great deal of labor and time in oflices. A ne\v and extremely simple electric tnchometer isp being prepared for the market, and it is expected that it will prove useful in power plants and central sta- tions, on boats, locomotives and automobiles. Many municipal improvements based on the use of electricity are about to be introduced. We have soon to have everywhere smoke annlhllators, dust ab~ sorbers, ozonlzers, sterllizers of water, alr, food and clothing, and accident preventers on streets, elevated roads and ln subways. It wlll become next to Impossible to contract disease germe or get hurt In the clty, and country folk wlll go to town to rest and get well. Electric Inventions ln War. The present international conllict is n powerful stim- ulus to invention of devices and implements of warfare. An electric gun will soon be brought out. The wonder is that it was not produced long ago. Dirigihles and aeroplanes will be equipped with small electric gener- ators of high tension, from which the deadly currents will he conveyed through tin wires to the ground. Bat- tleships and submarines will bc provided with electric and magnctiefcelers so delicate that the approach of any body under water or in darkness will he detected. Torpcdoes and floating mines are almost in sight which will direct themselves automatically and without fail get in fatal contact with the object to he destroyed. The art of tclautomatics, or wireless control of auto- matic machines at a distance, will play n very impor- tant part in future wars and, possibly, in the next phases of the present one. Such contrivanccs \vhich nrt as if endowed with intelligence will be used in in- numcrnlmlc ways for attach as well as defense. They may lake ll\c shape of aeroplancs, balloons, automobiles, surluro or uudcr-water boats, or any other form accord- inc tn the |'rquircmcat in cnch special case, and will lic uf igrvnlvr range and dc-st|'\1ctiyencss than the imple- rncnls new ~“v\n»l~»ye

78 THE ELECTRIC JOURNAL tilating bells on each end. But :these Niagara ma- chines were designed primarily with a view to setting up an abnormal air circulation by means of special “scoops” or ventilators on the umbrella supports. Very much thought and discussion were given to this subject of artificial ventilation. The results of our tests led to the ‘arrangement of thte scoops so that they acted as exhaust pipes. Also, water cooling of the armature spider was tried on some of these early machines, but proved in- effective, due to the fact that the cooling medium was applied too far away from the point of development of the larger part of the armature iron and copper losses. INFLUENCE or Dinner-CURRENT DESIGN It must be kept in mind that the general trend of direot~curren.t development had a certain influence on alternaiting-current generator work. For example, there had been a slow, but positive tendency in direct- curren-t generators, 'toward the engine type construc- tion. Also, from 1890 to 1893, direct~current gen- erator armature construction had changed from the surface wound .to the slotted type. This doubt-less had some inliuence in changing alternator design toward the slotted type, especially when the polyphase type of windings came into use. Also, there was a pro- nounced tendency toward the engine type, slow speed alternator, accompanying direct-current practice. Practically all of these early engine type alterna/tors, except the inductor type, had rotating armatures. Meanwhile, an interesting develiopnient took place in the armature construction of some of these machines. In most of 'the smaller belted machines, open arma- ture slots were used with machine-wound anmature coils. However, many of the early larger machines, especially of the engine type, were built for relatively low voltage, such as 440 volts, ‘two or three phase. This adnlittcd in many cases of simple bar windings with one or two conductors per slot. T~his allowed partially closed armature slots with shoved-through straight conductors, and bolted-on end windings, giv- ing a very strong substantial type of winding for re- sisting the rotational stresses. The pantially closed slot became a sort of standard in Westinghouse ma- chines, and endured for a number of years, and was even carried into the stationary armature type of ma- chine when rotating fields came into general use. This partially closed slot arrangement was a very good one as long as the generator voltages were relatively low. The same may be said of the rotating ‘type of arma- ture as a whole. However, when high voltages came into more general use, a different construction was preferable. In reviewing the period of the rotating armature, slotted types of machines, the monocyclic system should be briefly described. Apparently this was gotten out with the idea that it avoided the patented features of the Tesla polyphase system. The armature circuits on this monocyclic system were so arranged that. when carrying load, one phase carried nearly all of the energy load, while both phases supplied magnetiz- ing current.for the operation of induction motors. During the period when this machine was in vogue, single-phase lighting work represented the principal service, while induction motor loads were relatively small. With increarsed use of polyphase loads, and with the elimination of the patent situation, the mono~ cyclic system gradually dropped out. It was early recognized that a stationary arma- ture winding would be an ideal one in some respects, but it was tlrought that any rotating field construction was bound to be a difhcult and expensive one. The inductor type construction was supposed by some engineers to overcome the objections to the rotating Held, but many others considered 'that' this type was not a final one, as it did not use the magnetic material in the machine to the best advantage. In the earlier alternators, with insufficient ventilation through the armature core, relatively low magnetic densities were' necessary to avoid excessive iron heating, and the in- ductor alternator, with its non-reversal of armature flux, was worked at almost double the induotion of the rotating armature type of machine, and thus the disadvantages of the non-reversal of flux of the. in- ductor type were masked. In other words, the in- ductor alternator was worked well up -toward satura- tion, \vhile the other types were worked at only about half saturation. However, with improvements in ventilation due to radial ventilating ducts, improve-‘ ments .in iron by better annealing and painting of the laminations, etc., the flux densities in the rotating armature machines were gradually increased until high densities, approaching saturation, were reached. A corresponding increase in flux densities in the in- ductor type was not possible, on account of satura- tion. Therefore the rotating armature type of ma- chine, in the later designs, was much more economical than the inductor type, although the latter had a very considerable advantage, especially at high uoltages, in its stationary armature construction. Due to the merits of the stationary armature construction, the present rotating tield type of machine was gradually evolved, which possesses the advantages of the sta- tionary armature of the inductor type machine and the reversing Hux of the rotating armature alternator. It \vas the development of this type of machine which sounded -the deattth~knell of the inductor type. How- ever, the \\/estinghouse Company, about 1897, de-~ cided to bring out a line of inductor type alternators to meet market conditions, although such decision was contrary to the recomnienclations of the designing' engineers of the company, whose recol)1mendation in particular was in favor of the rotating field construc- tion as a more permanent type. However, as, the ro- tating field type was not yet established,” except in a very minor way, and as the inductor type had been on the market for years, it was decided to build the inductor type, although the design adopted wasssome- what different from the Stanley type. Three siz_es of these machines were built, two belted and one engine

THE ELECTRI can deliver seven-tenths as much output as a single- phase machine as it can give two-phase with the same total copper loss per coil. It was partly for this rea- son that many of the early Westinghouse polyphase va ; hi 1, ;.:|§ asf; ‘ Q -1 I 1 ; \'l\\'\\‘lll ““"“m " i F .?=_II?§- E§§§§§iE§§§§- 5, i;;--c l s 1 FIC. I\*VARIOUS TYPES OF EAFLY STr\Tl0N.\RY ARAIATURE \VINUIN(iS machines had a single closed coil winding. Another reason for such winding was that there were no deh- nite phase groups and no high potential between phases. Furthermore, the arrangement of the end windings was such that the coils tended to interlock and support each other, thus assisting in resisting cen- trifugaliiorces. This winding was used mostly for t\vo-phase machines, but was also used to a. consider- able extent on three-phase armatures. \Vith the advent of the rotating held type of ma- chine, this closed coil type of armature \vinding \V3S not used -to any great extent, open-coil two-phase and star-connected three-phase taking its place. Delta-con- nectcd three-phase was used in very rare cases, as there was danger of circulating current \vith such windings. In the construction of amiature windings possibly more radical changes have taken place than in the types of windings. Many of the larger lo\v speed rotating armature alternators had bar windings with separate end connectors, 'soldered or bolted on. Many of the earlier stationary type armatures had either built-up bar or strap windings, or concen- tric type \vindings in which each phase winding \vas arranged in a concentric group, and the groups of the different phases overlapped each other. Some of these \vere made \vith partially closed slots and others with open slots. The built-up bar or strap windings were frequently of the partially closed slot type, while the concentric \vindings were more usually of the open slot type. Gradually, however, both these types of \vindings \vere superseded by the “duplicate coil" type of winding, similar in appearance to the usual direct-current sarmattmre and induction motor primary windings. This later type of alternator winding \vas arranged in two layers of coils at the ends, in either one or two layers in the slots. The two-layer, two- coil per slot arrangement is no\v practically the standard. These types are illustrated in Fig. tt. In the rotating field machines, partially closed slot construction \vas carried to comparatively high volt- C JOURNAL 121 ages. For instance, the 6 ooo kilowatt, 75 r.p.rn., II 000 volt, three-phase generators built for the Manhattan Elevated Railway in 1900 had three hars side by side, in each slot, with soldered-on end connectors. As the partially closed slot and the open slot Con- structions are radically ditterent from each other, something should he said regarding the reasons which prompted the use of either type. As already indicated, the partially closed slot type came in with the larger rotating-armature low-voltage alternators in which bar \\'il\(iiI1gS could be used. 'l`his construction gave good mechanical support for the bars in the slots, thus avoiding the use of bands. Moreover, \vith the very narro\v slot openings at the top of the slots, there \\'as very little "lmnching" of the magnetic tiux at the armature tooth tips with the consequent low pole face losses, even with very small air-gaps, and high gap Hux densities. The disadvantages of the partially closed slot is found largely in the type of windings required. In these early machines, it was not found prac- ticable, in general, to use completely formed and in- sulatcthcoils with such slots, and therefore, either hand \vindings or built-up types of windings \\'ere used. \\'hile these were possible and practicable in a manufacturing cstablislnncnt, yet such types of ly pd j_ __ " Sh.; §T_";_¥ \&_ Y ( ` wig RF, /" " - \ ;¢;.1 "1 Q§<‘_~"t _. _ ' _ \ -la 'nw .1 _ .~‘~i'.~;;;,i f .‘ / » _` ' \ my ' “Z ' ils “¥,L-§._- 5 _ '~ ~_; tt, sat. _sw _ ,L vp . &,§I:;::,_;_,V :E ymif . ,__ ,J/|:=&,.,._ t _ - ' _ ,‘." 1-J" t" -4 ,_ ‘-:.»?<5i , ~ t i i\\ <"Lii‘vf? '. 'af"T1"~!‘{i`* ' '_ ~ ` ’ i' ha. . .'.<‘== = e \ \ 1»;’¢»r ’ ~. fi '~ i , , i -t?">' Eit- ~_ -;_ r i f .mf s * .fi 2; U ., 'I ‘ _ L..".‘i'tL " i ; .l" ‘Ji _ _ . .~ an _ - 2 __ -L-~' ' 1 ‘1 ; _ ' ,. _' ~ -. ‘ 'e se as f ~ ~i‘@x~:-; iz 2 ‘Y » f- " € wt. »-- .Y _E _,T ¢ , _f Z p , _s __ _,l 4 .Zh , _ \ = _ . : ,tt ` ~\ _ _ _ l A i _ 1 Af);- I : i i'i ._ ii _' A .~-"T 4 1 .. ,, .N` ,r p vw, - _g _ ,H . FIG, I27T|AR AND END CDNNECTUR TYPE 0F WINDING WYHK PARTl:\l.LY CLUSED s1.uTs \vindings are usually difhcult to repair by the ordinary operator inexperienced in the refinements oi armature winding. \Vhen it comes to repairs, the usual ma- chine'-wound coil, \vhich is completely insulated before being placed on tl\e armature core, is very superior

34 THE ELECTRIC JOURNAL was normal the e.m.f. at the end of the feeder was normal also, When several feeders ran from the same bus-bars it was impossible to get the proper voltage for each one when the line losses were differ- ent, but a meanvvalue could be selected. Recogniz- ing this limitation, Mr. Stillwell devised, in the fall of 1888, the regulator which bore his name. A trans- former had its primary coil connected between the two wires of the outgoing circuit and its secondary coil in series with the circuit, thereby increasing (or decreasing) the e.m.f. delivered to the circuit by the telegraph circuits, but was utterly inadequate when current from a dynamo was ready to follow a spark. The researches and notable inventions of Wurts were the early chapters in the story of modern lightning protection. He began his work on the improvement of fuses and lightning arresters about 1888. Tihe change which has come about in measuring instruments is best indicated by a question which was recently asked by a young man who had spent a year or more in a large commercial testing room. He saw a Siemens electro-dynamometerin al college laboratory and inquired whether/ they W == 1 were put to any practical use. `He was tg; Pféljii. _ -'!_-! 2-2'- !’_-Qnég; ."~}21 j5%T!+_!. 5-3 Ehwv told that in earlv testing room and la- : . i i T-` »f'll1i315_ ,_ [1 sig boratory work the dynamometer was g 1 i_ I ’ 1 the only instrument for measuring cur- filfi , " 'Q -i~`,f', ,1ii`i.'{"' ji ffmf.i3 ir.-iii. of rent with the ex eption of station in- iiii ii ill uaiiéiig' ‘i’iiil‘i‘i struments and ag few small imported i` direct-current ammeters of doubtful , §i?Q ":.._; ,_ g Z: _ quality. ,Even after the’ \Veston di- iiil ffl.-,_ *_ Fsjl ‘QI-...ill .Ein rect-current ammeters came into gen- ___1§ Lil' . eral use in.the early nineties, it was if "iii jI`)f§§f‘¥}.;; Q; §_ Q32 some time before there was a substi- "l;=Q.| tute for the dynamometer for the meas- 'WF lF,,_"‘q Ef§_`l_‘b'l§_!§i‘fl;li’l& riflii; urement of alternating current., Dur- `"|; ing this early period practically the `~`f.‘il1',,‘53 'only voltmeter was the Cardew volt- .'°.:i’§1;~sf§>:2.§`~lT EF if.. his; zltéti f; a he wife insffumm in which `;5', ..`, l. the Fine wire was protected by a brass -` 'i ipgjjf §,\_ tube three or four feet long, the ex- fiif ll _ pansion of the wire being indicated by ~ a pointer on a circular dial._ This volt- Qi _El gif ‘gzip f meter was made for 60 volts and 120 if£..&;`_5iv.lf§-Qgfi ilii ,3;i_-V21 iii volts, the former requiring about one- l“li’mmmln-m,l;;llf;I>- I third of an ampere and the latter a Q' § -=l"> .,¥,I2_<, F, - 1f`€}f`;\% if somewhat less current at full detiec- Q I ` fbigi i I ,_ tié tion. For alternating-current Power ,g ‘ "" alll- _ _ "-"' measurements, a dynamometer was _ .=>2-{§°~‘:3;4§-;g,q-7-»-~~'~+-13'-ir{§4:4-f'I¥§

224 THE ELECTRIC JOURNAL and magnetic proportions of the rotors a feature of first importance in tl\e design, so’ that the radial slot type for t\vo-pole machines has become the standard construction, almost universally. This will be referred to again under the four-pole construction. While the two-pole parallel slot construction was being developed for larger capacities, the four- pole construction for 60 cycle machines has been FIG. 27fFIEI,D CONSTRUCTION \V1T1-1 'Iwo HA1.\'ES HELD TOGETHER BY 11EA\`Y BOLTS pushed up to capacities of about 12000 k.v.a. with the parallel slot, cast steel rotors. In order to do away with the through shaft construction, the rotor was made of two castings or discs, each of which \vas cast solid with the shaft, as shown in Fig. 27. The two discs, after machining, were bolted together by a number of very heavy bolts located near the pole tips and, in some cases, shrink links were placed in the pole face, connecting the two halves together. The parallel grooves were then machined in the steel core, just as in the through-shaft type. In this four- pole construction, the problem of armature ventilation was comparatively simple. Air-gap ventilation (that is, all air through the armature core supplied from air»gap) was easily accomplished, due to the open spaces between the poles, which could admit an ample air supply, However, the same construction tended to\vard high \vindage losses due to air “churning." This problem of ventilation has had much to do with the evolution of turbo-generator design* In the two-pole, parallel slot machine for 3600 r.p.m., in which the diameter of the rotor is relatively small, the amount of air which can be forced ‘into the air-gap from each end is rather limited. Assuming, for ex- ample, a rotor diameter of 24 inches, which is almost as large as we can go for a 3600 r.p,m. machine. then. with a11 air-gap (iron to iron) of M-inch, which is also a fairly large gap, the total cross-section of the air inlet at the air-gap at both ends of the rotor will be 112 sq. in. \Vith the very high air velocity of IO 000 ft. per minute, this means a total air supply of less than 8000 cu. ft. per minute. This may be suf- ficient for a moderate capacity turbo-generator, but for machines of high capacities, sucl1 as 3000 to 5000 k.v.a., this is not nearly enough cooling air. Obviously, either much larger inlets through the air- gap are required, or some additional method of cooling *A more complete exposition of the subject of “Turbo- Alternator Ventilation.” etc.. is contained in a paper by the author, read before American Institute of Electrical Engi- neers. Iannary. 1013. is necessary. Larger air-gaps usually mean either more expensive machines, or reduced output with a given machine, due to lower tlux densities. There- fore, the tendency, in machines of the very high capacities,- and very high speeds, has been toward a combination of air-gap with other methods of ventila- tion. In the 25 cycle, two-pole machine with a maxi- mum speed of 1 500 r.p.m., rotors of larger diameter are possible and, as a rule, much larger aiir-gaps are practicable than in 60 cycle machines. In consequence, air-gap ventilation comes nearer being practicable but, in the larger capacities, even this is insufhcient and auxiliary methods have been necessary in some cases. This need for auxiliary methods of ventilation led to the axial method of Ventilating armature cores in distinction from the radial method, in which the air was carried out through numenous radial air ducts or passages. In the axial method, a large num- ber of Ventilating holes are arranged in the amiature core parallel to the axis of the machine. These form veirtilating paths in parallel with the air-gap path With the s1na.ll diameter long cores necessary for 3 600 r,p.m., high capacity machines, the development of this method of ventilation was contemporaneous with 'the development of the h-igher capacities. The same has proven to be the case for the later types of \7Vestingh0use four-pole, 60 cycle, 1800 r.p.m. ma- chines, \vhich departed very considerably in rotor con- struction from the four-pole cast steel type alreadv described. As the capacities of the 3600 r.p.m., 60 cycle machines were gradually pushed up, a corresponding development occurred in the 1 Soo r.p.m. machines. At 10000 to 12000 k.v.a., the four-pole cast steel construction was apparently approaching its limits, For larger sizes, therefore, a different construction was adopted which allowed more suitable material to be obtained. For the largest diameters and highest ll ,.,, .s . -frm. =»= - 1 -. im. _Ja .- r ~ >_,.;;:‘::-1,___ - ""‘*‘ ‘f ~ ._V - , ,M-_ FIU. 28-MODERN RUTATING FIELD UN BALANCING WAYS speeds, a plate construction was adopted by the West- inghouse Company, in which the end discs and the shaft ends were forged as units, and the intermediate discs were made of rolled plate material, the whole construction being bolted together permanently to form a solid core. This core was then slotted with radial slots, and tl1e usual radial slot type of field Winding is used. A similar construction was adopted on the

THE ELECTRIC JOURNAL 33 The bus-bars for Iooo volts were usually bare copper rods held by wooden supports on the front of the board. On one occasion a young electrician whose experience had been with batteries, joined the bars by a wire to see if he could get a spark. He did, but fortunately was not seriously burned. The ~ - Iv 3, K€"?.iqr '. *' ,¢, i '\'*» ‘ ____ t.--.1 ' ‘ri = r. V "W r s .. _.ffl *' .3 ' »-t4:€;¥;“~f ‘ ` “‘ 1-/~\»l 1 * it ijt, ~ 'I ' £1 1 `=~a F 1 Q’ ir. 2, t g _ gi ‘s 3 ¢ _ l t a 4 »5 _ j i _ gr '_ ', i _I l K ~ _ if ` ff ` ff ‘ V ‘ * . _ f ~~ j :Q . -_ i 4 p V ‘t _t i , 1. 7* f l ' _ , 1 li 5 l 1 1 f 5 ._ .,_y,__ Z Q ‘ 2 i W ~ i A i J gy ` _ »..».,,_;,_,- L .4 i . ; :V ~ - V 4 ; _ ._ l ~ ~ T f Q ze i__,, i.f ,,,., _ 0:32 _ _ ' ‘ of no. 7~5TATl0N "A solenoid pulls a tached to one end of a voL1'Mr:'rEa AND AMMETER soft iron wire plunger which is at- lever which carries a weight at its other end. The e.m.f. necessary for causing the voltmeter pointer to come to the the fixed resistance in the arrow is determined by the setting on right hand side of the case." safety catch or fuse four inches square on was a wooden block about which were mounted two lead fuses, one or both of which could be used, depending on the arrangement of the plugs which completed the circuit. The switchboard transformers were placed in wooden boxes and were mounted at the top of the '~. ,' rjff - »» ,_ _ . 7 , ~~= _ ._, ‘r'r_ ' i;"'i "‘ ‘ ""‘“ Tarfiigifii.-L”¥%5 . »»s' F ge i -usze-;a.;dw=<:- tsyfddg ; '_ _ i ‘;‘wf3‘Li.‘5{I 1' "' *"!»f”-.4 Ti: ,t~ < 1 51 _ ..,,;,,.<7%2,_ ._ » _ ’~ if.~~€‘ -' cn. tj( .»_, ; ~ ~ ~ ;=;',,~_ ¢ ,_ a _ vsiie? fi l » j wail' L; | j ; ' iff l _ _ A s`f-- _ T; 1' -‘Lis _:_ »v ' S ‘ -J\_.i”; ' _ 'Q .`-_ ei is _ e¢\-' ; __ - "‘ ._ ‘ _ 5 if » W. 4. ’= *f?€7=~»» T ‘ ~=;1;'~. ,_ _~,, ,._,:k»._ . _, , _é-t._, _____,LE.-._. Pro. 8-voi.1'uc'ren couveusaron c number of turns through which the primary current passes is determined by the position ot' the plug near the top. The number of turns in the secondary winding which is in series with the voltmeter is adjusted by the switch near the bottom. In this manner the instrument can be adjusted to reduce the voltmeter reading by the same percentage as the line drop reduces the pressure at the lamps." “Th board. The board on which the apparatus \vas mounted was either of matched flooring or \vas an open wood framework. The early voltmeter had a lever on one end of which was a weight (adjustable by the number of shot in a brass cylinder), and on the other an iron wire plunger which extended into a solenoid. Incan- descent lamps were used as a resistance in series with the solenoid. \Vhen the applied e.m.f. was at normal value, the pull by the solenoid was just suf- ficient to cause the pointer attached to the lever to point vertically. There was no graduation on the scale. This voltmeter was soon superseded by another in which German silver resistance replaced the lamps. The ammeter needle traversed a circular dial under the action of a plunger in a solenoid \vhich car- ried the main current. In a later form the mechan- ism was simpler, the deflection being indicated on a scale near the bottom of the instrument. FIG. 9-srxcsr LAMP cou., 1888 "These coils are so wound that twenty oi them are placed in series when I0O(`| volts are used. A 50 volt incandescent lamp is connected in shunt across each coil. When the lamp is burning the coil is ‘not in ac\ion'; when it is broken the total current passes through the coil, which practically re- places the lamp. The brillianc of the remaining lamps is not appreciably affected until iilve or six lamps are broken and then it is dimmed. This result is accomplished without any of the magnets or fusible connections or any of the moving parts or contacts which are annoying and crude ac- companiments of many so-called series systems." On the feeders were voltmeter compensators. These were series transformers, the primary circuit being in series with the feeder, and the secondary in series with the voltmeter. Outgoing current caused the voltmeter to read low, and it was necessary to Q 'P 'Ta "Q fi? | _ pg- " if \ D i W ` "$' _ 1 ii éfflri », ‘ Kia, 1. ,_ '- 4~ > . at Iwo//..»»., I-`IG_ Io-ucnrumc Arzxzcsrerc, 1888 This arrester \vas installed on 1000 volt circuits. The middle section was grounded and the other t\vo \vere con- nected to the dynamo terminals. It worked \vell if there \vas no lightning; but a spark was apt to he followed by dynamo current which volatilizcd the spark points and short-circuited the dynamo. raise the bus-bar e.m.f. in order that the voltmeter might give normal indication. The compensator caused a drop in the voltmeter circuit proportional to that in the feeder, so that \vhen the voltmeter reading

74 THE ELECTRIC JOURNAL from the slotted type of armature \vith a number of slots per pole, which was a considerably later develop- ment. TOOTHED ARNIATURES The first commercial toothed type of armature appears to have been gotten out by the \Vestinghouse I7 FIG. I*SURFr\fE \VOUND ARMATURE \NlTl>l RAUIAL CLAMP5 (UPPER) AND wrrn Axim. cl,/\Mx=s (Lowes) Company. These first machines were radically differ- ent, in details of construction, from the later toothed armature types of machines which came into general use. The nrst toothed armatures were small air-gap machines. In the surface-wound armatures, the clear- ance between the armatnre surface and the field poles was comparatively small, although the total air-gap (iron to iron) was large on account of the surface winding. In constructing the new toothed armature, the actual clearance (iron to iron) -between armature and field was kept about the saine as in the surface- wound alternators (bands to iron), but this clearance actually represented the total air-gap in the toothed type. Moreover, in sinlcing the windings below the ix ii , \ /\ FIG. 2 surface, it was endeavored to maintain a practically uniform outside surface, so tha.t overhanging tooth tips were used with re\ative\y narrow s\ots ior putting in the windings. The general construction was similar to Fig. 2. On account of ‘the small clearance, and consequent higher magnetic conditions, it was found necessary to use laminated poles with these machines in order -to avoid excessive field heating. The self-induction of the armature windings on these machines was very high compared with the old surface-wound armatures and, therefore, in order to obtain passably good regulation, fewer armature turns had to be used, with correspondingly higher induc- tions, and this made the use of solid poles impractic- able on account of heating. Furthermore, on account of the overhangring tooth tips, the small air-gap and the high induction per pole, this early type of toothed armature \vas very noisy. In one instance, it was credibly reported that one of these machines could be heard t\vo miles away on a quiet night. However, several machines of this construction were put out by the Westinghouse Company, and operated for many years. Meanwhile, the possibilities of the toothed arma- tnre ccmstructsion in the old cast iron field were being given consideration. The writer made a special study of this matter, and finally decided fthat, in order to make this construction possible with solid cast iron poles, it would be necessary to work at relatively low "> ~`.. <\ inductions per pole, and with a very large air-gap. (fully as large as on the old surface-wound machines) and with a shape of 'tooth tip which did not have such great width_compared with the pole tip as shown in Fig. 2. This meant that a pole tip and air-gap as sho\vn in Fig. 3, should be used. \’Vith this arrange- ment, the armature self-induction would still be rela- tively high, and the regulation correspondingly bad, necessitatting some form of compounding for regulat- ing the voltage, similar to the compounding of a direct-current generator. This armature construction was worked out in detail for a 37.5 kilowatt field (that is, for the standard field of the 37.5 kw surface- wound type of machine). The armature teeth were similar to those in Fig. 3, in shape, and the air-gap or clearance from iron 'to iron, was made QQ inch on each side of the machine. The field was ~also com- pounded. VVhem this machine was put on test, it was iound at once that it eou\d be \oa¢\ed to Go \

222 TIIE ELECTRIC JOURNAL than the others in order to accommodate the grooves in which the rotor end windings lay. The discs were made of high grade forgings. After some of these machines had been in operation for a considerable period it was found that some of the discs in the field core were traveling axially, i.e., quite appreciable gaps FIG. 23-EARLY TWO-POLE ROTATING FIELD tb<'nmnaq:-:ysronw*:-yy; `,,,»\<:"._,_=/='.:‘»»_;_~»\mm,_.'°{:1.‘2.£§‘,§'E §5?\7Q‘F»?`°§5'i5"=,zg"§i'ic-°‘&’.:’<`§~Z‘<1=E.Z’,o "mg-m'l.`-»-»-».= -‘~»§5_>--"?==‘,:;e-‘E:§ ~\==Y`>0-"cu :‘0...O ~g:f°¢,r::-_mg " C ~r=:'o¢o**:..*-°-Z; =-img” ' oono-». .-,.._. _._.o .___ ,ou nr ..,.. .-¢¢___._m ¢,;_...O¢,,,m,,_.;;;»:<,,-»-. ==“=»'3,,,?,f‘<=’s'=s,_5=f>2=UQS”:'5‘°-:LQ =‘ “Q_=~?~f>=l§¥" °Q*”"'2.9raE'-=-f==9 €l.=-‘-=~§`§`§`<= .:§&’,3fw;~"’ “so” 25. :S':J -*mc*-* >- w or 5 3g<=F=’°°§,,=;-;=.§Q'_,§=9\'=9"t25`85"=5<:.'&<¢=1 -1 rn ,._ ,.. ...OO .--\,,,°"¢f\ ::»=-=`<=“o,,,f°fn,.._¢a°-‘;,n Q,.-»::..,,- §€S_-¢°f"=f-=»§3 ..U=f,=f=‘S,“°5‘ 2-Hg; mr: -\E~<"g€g-.:--_:OF-.5'=.-Eg;-mo, s==:‘°'€°8.-»2;g_.--{’°=‘»<'€,,2 ”U°£’.:-+50-w§ w Q, - -» ’“' _,-- --~m :_ em »-. »\:_____ =m£fDg.-.»§_.-,__n.. :-"?‘-?\;,'o"’=5.~"*<>"§r1=5"%c.=rQ.»»0=-"' -. _.»-». ru ="‘-r m-1 .__ Q, :D w UQ,_. nan; ,,:<. Q-in °'°»-»°E °= g3~;»as»es2s=Fa~»a°aesa #sie %“~e<»%r§s'5='°e~2§%»‘?==‘-=€;If~ _.. "N _ -‘f° r' : a¢Q2§a§.-’s ¢s~;g"' wm:r‘=-n»-r$'°u>_g='§g =“5:‘E~§"=‘§°-§==3‘53-‘”~‘4’~°‘5 2 "' 2-O-,5 °u|g_fh.-~§32-$2530 EOm~; agwog __ :_.. ::nqq._.1Q,,U-.,;r_,»-4 »=¢.»..w.;w.:»orr¢z=‘w*<-=.'|oruo= tilt H FIG. 247R0UND TYPE TWO-POLE ROTUR are concerned, for, of all the sizes and speeds of steel rotors which the WVestinghouse Company has put out, not a single cast steel disc has burst. Present speed and output requirements have now carried the con- struction up to a point \vhere special forged materials are the accepted practice. Soon after the two-pole, 400 kilowatt rotating held machine was put on the market, a four~pole, 750 kilowatt, 1 Soo revolution machine was built. The rotor of this machine had four salient poles bolted on. These poles were provided with overhanging pole tips, and the field winding consisted of four coils wound with strap-on-edge. In fact, this first construction was very similar to the present type of rotor tields now used for other than turbo work. This construction proved difficult and expensive, but was applied to a number of six-pole, 1 200 revolution machines. How- ever, the parallel slot construction used in the two-pole machines was so satisfactory that it was soon adopted for the four and six-pole machines, as shown in Fig. 25. In the six-pole machine it was not possible to make the poles integral with the central core, on account of the inability to machine the parallel slots in the sides of the poles, or put in the windings. Therefore, separate poles were constructed, with parallel slots, and these |||l|;]u|| i 11.* %,§i1Yx .,_/f, -~ \\\\\- ~n~ .qw we 4% "\\\\ /Zi `\\ / aa; FIG. 25-PARALLEL SLOT FOUR-POLE AND SIX-PDLE FIELD CONSTRUCTION \vere tirst wound and then bolted into place on the cen- tral core which, in this case, was made integral with the shaft. The four-pole machine was constructed for 750 and I ooo kilowatts capacity, and the six-pole con- struction was made for; 500 to 3 ooo kilowatts. Meanwhile, there had grown up some demand for moderate capacity 25 cycle machines at 1 500 revolu- tons. These \vere constructed along exactly the same lines as the two-pole, 3 600 revolution machines above described. In this early work one order for four 5500 kw, four-pole, I ooo revolution machines was taken. This was entirely beyond the constructions undertaken bel fore by the Westinghouse Company. The parallel slot type of rotor was adopted. An attempt was made to get forgings in a single piece large enough for these rotors, but they were found to be glass hard and brit- tle, except at the outer surface. As very large steel castings \vere frowned upo`n, it was decided to make

THE ELECTRIC JOURNAL 31 by the dripping of oil 'from large brass reservoirs. Excellent as this may be, if testimony be needed as to the superiority of self-oiling bearings over the kind which needed fairly constant inspection to see that the oil dripped properly, which had to be filled frequently v \ 4| -t ., . .na » v one 1 num -up-\ it-/in it »¢ . na ' rs ~|.. a-.init-a¢na| tu | 1-wma A - Aera 1'm| znmvars s somnoc .cm- l> - E I l iiiiai si.B§.!§ s§§ v... FIG, 3*CHRONOI.0GICAL CHART OF SDME IMPORTANT EVENTS IN ELECTRICAL ENGINEERING HISTORY and polished every night, the writer is prepared to testify from personal experience. \Vhat were some of the limitations of the alter~ nator which produced the current in hundreds of central statiions for many years? lt was heavy and expensive. Between the cylindrical surface of the iron core of the armature and the faces of the field poles must be space for insulation, for conductors, for insulation again and for band wires as well as free space between the band wires and the pole faces. Mechanically the space should be large; magnetically it should be small. If the armature got slightly out of center, it would strike the field poles, the band wires would give way and the “blowing up” of an armature was an exciting event. The life of the armature depended upon the integrity of a goodly fraction of a mile of steel band wire, wound under tension and subject to unknown stresses. The cop- per conductors could not be wound conveniently in more than zi single layer, and the large conductors necessary for heavy currents in large alternators were heated by eddy currents generated in their mo- tion through the magnetic field l)€l\VC€l1 the pole faces and the armature core. The band wires, being grouped together into bands in which the adjacent wires were 'soldered togther had heat producing currents induced in them in the same manner. Mag- netic fields are apt to cause trouble \vhen outside of their native element-iron. \Vinding in slots in modern armatures has replaced the old surface wind- ing, \\’ires lying on a smooth cylindrical surface in a magnetic field have a “side force" on short-circuit \vhich is hard to resist by any practical form of anchoring. Hence, a short~circuit used to cause me- chanical damage followed by internal electrical dis- tress and a season in the repair shop. In those days the skilled armature \vinder was the autocrat of the electrical industry. The slotted armature and the machine wound coil marked his doom. The armature which immediately succeeded the first form was the toothed armature, \vhich had a large tooth corresponding to each field pole, around which the armature coils \vere placed. The teeth fhad small projections at the circumference \vhich served as a mechanical support for the coils. An armature of this kind \vas made for the field of the smallest alternator and was turned over to the writer to test. The air~gap \vas very small and the wire \vas large compared with that for the old drum arm- ature; hence, a large output was anticipated. After obtaining the proper voltage and applying the load, the field current was increased as more and more lamps were added until presently there were a thousand lamps on \vl\at had been a 400 light machine. It was noted that the field current with the large load was three times \vhat it had been with no load. The question came as to \vhat \vould happen if all but a few lights \vere suddenly removed; would the voltage go to three times normal? This brought an appre~ ciation for the first time of the significance of in- herent regulation. Subsequently, the air-gap was made much larger and the regulation was very much improved. After a time the slotted armature con~ FIG, 4-THE CONVERTER OR TRANSFORMER _ “It is a device of the simplest possible construction, hav- ing no moving parts whatever, its functions being purely electrical. lt consists essentially of two coils, one of a great length of Hue wire, called the ‘primary coil’ and receiving the current from the dynamo; the other of a short length of large wire, in which is induced the secondary current for lamp service." struction, first finding favor in railway motors, \vas incorporated into generators and motors of all kinds. TRANSFORMERS The transformers (then called converters) \vhich \vere made by the \rV€Slll`lgllO\lS€ Company in

Electric Journal February 1914 The Engineering Evolution of Electrical Apparatus-II THE ALTERNATING-CURRENT GENERATOR IN AMERICA B. G. Lawn: Chief Engineer Westinghouse Electric & Mfg. Company FOREWORD~7`he following article contain.: a fairly camplrle brief history of the evolution of the alternating-current generator in so for as the Company with which the writer is connected is con- cerned, as drawn from the 'u/riter'.r memory prineipally. Reference is made incidentally to the work of other mamzfacturing campatties, but this cannot be very romplvle, as the 'lt/riter naturally does not have thc necessary material available for dturerilliug such dt'1/elo/11l»ent.r, exft'/wt in a 'L/ery general way. There- fore, the inadequacy ofghis history, outside of the lVt-stinglioure part, should be charged ta the lark of data rather than to lark of respect for lhe work of olhcrs. N the early days of the alternating-current gen- erator, it was constructed in almost as many types as there were designers. The principal en- deavor of each designer appeared to be toward the development of a new alternator which would bear his name. A few of these early types were of the rotat- ing field construction, while a much greater number were of the rotating armature type. Some had iron core armatures, while others had coreless armatures, and there were many discussions as to whether the core or the coreless type was superior and would sur- vive. Many of the early predictions would now form quite interesting reading, in view of the fact that pres- ent practice is so far removed from the early anticipa- tions. Here and there among the early machines was one whlich contained some of the important elements of recent apparatus, but in many cases such ma- chines disappeared in the general course of develop- ment, the meritorious features .being insufficient to save the type. SURFACE WOUND ARM ATURES In America, the principal early type of alternator had a rotating armature with surface windings and an external cast iron multipolar field. This type was used very considerably or, in fact, almost exclusively, from 1886 to ISQO. This was the type built by the Westinghouse and the Thomson-Houston Companies. There were only minor dilierences in the construction of the machines built by these two companies which, however, at that time, appeared to be very great. These differences consisted principally in the way the end windings of the armature coils were supported, in the construction of the end bells and ventilating open- ings in the armature core, in the method of attaching the armature core to the shaft, in the winding of the field coils in metal bobbins, etc. Both machines had surface \vindings \vith concentric coils, one layer deep in the radial direction. In the Westinghouse con- struction, the end windings were tumed down toward the shaft and were supported by radial wooden clamps, as rindicated in Fig. I. In the Thomson- Houston armature, fthe end windings were *arranged in an axial instead of a radial direction, and were supported by bands or external clamps; This con- struction is also iudicalted in Fig. 1. The Slattery machine, \vhich \vas also on tl1e market at that time, was of the same general type as the above machines. I"resum;|bly these two different methods of end wind- ing \vere used on account of the patent situation. At that time there \vas much discussion of the respective merits of the two constructions. These early machines \vere built principally for frequencies of I5 ooo and 16ooo alternations per minute (125 and 133 cycles per second). In those days, everything was rated in alternations per minute, as this represented the product of the number of poles hy the number of revolutions. Such high frequencies \vere selected, mainly, on account of transformer con- ditions, and not alternator design. Practically all al- ternating service consisted of house to house lighting, and in relatively small units, and the higher frequency was supposed to be of great advantage in transformer design and operation, which presumably \V3S the case \vith the very small amount of dam and experience available at that time. About the only commercial voltage for alternat- ing work at that time was 1 ooo or 1 loo volts. This was supposed to be excessively high and dangerous, and there \vas much question whether such an ex- cessive voltage shonld be permitted. This matter was actually taken before a number of the state legisla- tures for the purpose of obtaining laws prohibiting or limiting the use of such voltage. Another reason why no higher voltage was used \vas in the construction of the alternaltors and transformers. With the experi- ence and materials available at that time, together with the high speed rotating armature construction andthe surface \vindings, even 1 100 volts was a very serious problem in the generator. About 1889 or 1890, there appeared some slight demand for higher volt- ages, and a fe\v 2 ooo or 2 2oo volt surfaee~wound al- temators, of the then standard type, \vere built. How- ever, evcn then it \vas recognized that the surface- wound type of alternator was not well adapted for higher voltages, and there \vas much question whether a different type winding should not be developed for I 100 volts. This gradually led to the next big step, namely, the development of the “toothed” type of al- ternator with one big tooth per pole, in distinction

THE ELECTRIC JOURNAL 225 larger 25 cycle machines. For intermediate capacities, both 60 and 25 cycles, solid discs are used in some cases instead of the plate construction. This brings the larger turbo development up to the present date. In the comparatively small 60 cycle turbo-genera- tors, where the parallel slot construction with the bronze driving heads was relatively expensive, as al- ready described, the later development has been to- f`,?}§i"¥2{" -_ ~ ,\ ~~_ :eg _, \ _ g ,wagg , _ . _ /. .V ,. _A f.; ~,. - , .iii _ _ 6' 'I ' W/((( Mitts ,Mi _T g V1 . ~. »' ti I. ‘ . t },|, R as = is ~, ""' . \ 1- , I o me ,. , I .t liiiii' \ _,c 9 5; \/ §<`*i'°f~ 17: Q /L »f .n.»t.»..,,...t»...sai_»,ce use FIG. 30-SAME MACHINE AS SHOWN IN FIG. 29 BEI-‘DRI-1 WINDING the specilic constructions described, and a number of interesting types or constructiions have been brought out. The gradual increase in speed has undoubtedly had much to do with the evolution of their various types, just as in the case of the VVestinghouse evolu- tion. One of the most radical steps which the Gen- eral Electric Company has made in the past few years is in the change from the vertical to the honi-

226 TIIE ELECTRIC JOURN/lL zontal type of inachines. Presumably the very high speeds which later came into use have had much to do with this change. ln the earlier turbo-generator prac- tice, the speeds of the General Electric Compauy’s machines were relatively lower than the \Vesting- house, presumably on account of the type of ste'am turbine used. l\lany of tl1e early rotor constructions were of the 'salient pole type for four poles and higher. Gradually these were superseded by construc- tions leading up to a radial slot type in which the slots were formed by teeth inserted in dovetail grooves in the rim of the spider. This type \V2lS very similar in appearance to the later types, except that the slots had overhanging tooth tips, thus giving a partially closed slot construction. More recently, \vith greatly increased speeds, this construction has been super- seded by solid forged cores with shaft forged on, and with radial grooves milled in the surface for the field .= ,/ r- ~<. uf V ' m A ' _A t ff 1 ,L ~-_' , 5N\\\ t ~ _ _VA gg >&;.:~,\\,\w\~. wh., - _g . ' , _"~'fi%kl`¢` \T"""--\`_ v"" ' FIG. :§IfSTATOR OF LARGE BIODEFN TURBO-ALTERNATOR Showing end winding and method of bracing large ma- chines to withstand short circuits. winding. These latter rotors are used largely in the horizontal type high speed machines. In the Allis-Chalmers construction, in the larger machines having four or more poles, the earlier con- struction of the rotor consisted of forged discs with through shafts. These discs had radial slots for the windings very silnilar to the present construction of all manufacturers. The smaller machines generally had cores forged in a single piece with the shaft, and with radial windings. As regards methods of ventilation, both the General Electric and Allis-Chalmers Com- panies \vent through a course of development leading up to their present practices. As regards parallel operation, turbo-generators have been particularly free from this old time diffi- culty, due largely to the uniform rotative effort of the steam turbine, and partly to the high Hywlieel capacity of the turbo-generator and turbine rotors, which tends to limit any speed oscillations, due to the governors, to a relatively lo\v period, such as \vould not tend to accentuate the hunting action in the generators them- selves. Moreover, in those rotors which have been built with solid cores or of thick plates, the solid ma- terial tends to act as a damper circuit. As a conse- quence, hunting in turbo-generators, or difhculties in parallel running, have been extremely rare. rNoUc'r1oN Tukno-GENERATORS This type of turbo-generator has been proposed commercially 21 number of times during the past ten years, and a fe\v installations have been built. The nrst of any importance, consisting of a 1 250 kilowatt generator of 30 cycles, I Soo r.p.m., two poles, was in- stalled in the plant of the Baltimore Copper Smelting & Rolling Company. This generator was a true poly- phase induction rnotor, direct connected to a steam turbine. The construction of the generator was ex- actly the same as \vould have been used at that time in a twcrpole, 1 800 r.p.m. induction motor of the same capacity. The entire load of this machine con- sisted of a I 200 kilowatt rotary converter connected directly to the tenninals of thegenerator. The gen- erator and converter were brought up to speed sepa- rately and the rotary converter, with its field excited, \vas connected directly to the generator and furnished the excitation for the generator. There \vas no other synchronous apparatus in circuit except the converter. Several years ago, a number of much larger in- duction generators were built by the General Electric Company for the Interborough Rapid Transit Corn- pany of New York City. These machines are of 6000 k.v.a. nominal capacity and operate in parallel with the Itooo volt, three-phase, engine-type gen- erators previously installed in the same po\ver house. The engine-type generators furnish the excitation for the induction generators. The entire load of this station is represented by rotary converters. There have been no prominent -instances of the use of in- duction generators for other than steam turbine drive. Apparently this type of generator has no very \vide Held. CONCLUSION This history is admittedly far from complete, in that it has not mentioned the work of some of the earlier, and also some of the later manufacturing com- panies. The field is far too large to permit everything to be covered. Moreover, no attempt has been made to describe European constructions and developments in alternating-current generators. It may be stated, however, that in some very important features, Eu- .ropean engineers antedated the Americans, while in other equally important constructions American de- signers were tirst in the field. As a rule, the represen- tatives of the electrical manufacturing companies have been so wide awake and ready to adopt new principles when they contained any promise, that it is sometimes very difficult to give any company or individual proper and deserved credit for being first in any given devel- opment. Furthermore, no attempt has been made to give credit to the various engineers who have been closely identified with alternator development, for it would be impossible to do justice, or give deserved credit to all of them.

Electrical Journal March 1914 The Engineering Evolution of Electrical Apparatus-III THE ALTERNATING-CURRENT GENERATOR IN AMERICA (Cont.) B. G, L/trans URING the past iew years, some very interest- ing spider constructions for the rotating fields of large high speed alternators have been built to meet the severe speed requirements. Some of these have been made up of cast steel centers or spiders with cylindrical rimsbuilt up of overlapping laminated punchings, thoroughly bolted together and attached to the spider by dove tails. The outer peri- phery of the laminated ring carries dove-tail grooves for poles. In another construction, the entire spider consists of thick rolled iron plates, bolted together, and \vith dove-tail grooves on the outside for the poles. In still other constructions, the rim of the spider consists of a heavy steel ring in_ one or more sections to which the cast spider is bolted. Usually with this cast rim the poles are bolted to the spider. In some cases the rim forms an integral part of the spider itself, being cast with the spokes and hub. The- type of construction adopted in each case is, to a large extent, dependent upon the stresses to be taken care of, so that no one type seems to ht all cases to best advantage. "run Pnoncizitl or VENTILATION In the later rotating field alternators the problem of ventilation has received much consideration, espe- cially in the case of machines operating at abnormal speeds. In very high speed machines of very large output the arniature and field cores have a ratio of width to diameter which is relatively much greater than in ordinary machines, and this has necessitated abnormal conditions of ventilation. Something may be said here regarding the general problem of ventila- tion of alternators anti its influence on the evolution. llack in ISQI or 1392. radial ventilating ducts or pas- sages came into use commercially on certain direct-cur- rent machines. The results being quite satisfactory, it was natural that alternators should have the same method of ventilation. The use of such ducts was in reality one of the great steps forward in the evolution of dynamo~electric machinery, although but little rec- ognition has been given to this fact in electrical literature. The use of radial ventilating ducts has continued to the present time with little change except in the construction of the spacers them- selves. which have been many and varied in design and materials. \Vith the change from the rotating armature to the rotating tield construction of alterna- tors this feature was retained in full. In some of the earlier Westinghouse rotating field machines the field structure also had numerous ventilating ducts, princi- pally for the purpose of supplying ample air to the armature ducts. Also, about -ten years ago, special ventilating end bells and vanes began to be used on rotating fields, in order to set up an extra. air circu- lation through the armature end windings, etc., due largely to the iact that the slow»speed engine-type ma- chines of that period did not have much natural blow- ing action. Following this, and partly as an outgrowth of turbo-generator enclosing, came the semi-enclosed alternators, mostly for high-speed water-wheel driven units, and this practice is not uncommon at present. 'l`he proper ventilation of an alternator or, for that matter, of any dynamo-electric machine, is very much of a problem, for no two cases, in different sizes or types of machines, arciquite alike. The problem lies first, in furnishing the proper quantity of air to carry away the ‘heat developed, and in then distributing such air in proper proportion through the complex multiple paths in the machine. The proper distribu- tion oi the ventilating air is usually the most serious part of the problem. The present solutions of the problem are based largely upon past experience, and no really workable rules have yet been developed. In arriving at the present practice many disheartening experiences have been undergone by all designing en- gineers. The writer has known many cases Where totally unexpected results, both good and bad, have been developed and, in some of these cases,.no logical explanation \V35 forthcoming, so that the results could not be taken advantage of, with any assurance, in fu- ture work. This has been one of the most discourag- ing features inthe general problem of ventilation. ARMATURE wiND1Nos Something might be added here on the subject of armature windings. There have been probably as many types of armature windings developed as there have been types of alternators. The windings for the earliest smooth body and the toothed arniature con- structions have already been described. ' In the early Westinghouse polyphase alternators, two-phase was used mostly, due principally to the fact that single- phase lighting circuits formed the principal load, and, with two-phase machines, there were only -two circuits t'rom»a machine instead of three circuits with the three-phase winding. Moreover, .many Sf these very early polyphase alternators were used ~m~ reality as straight single-phase machines, taking current otf one phase only. For this purpose a closed coil arrnature winding, like »that of a direct-current generator or ro- tary converter, with four taps for taking off the two phases, gave about the most economical type of wind- ing, as far as armature copper losses were concefrled. When such an armature is used for single phase it

THE ELECTRIC JOURNAL 35 the coils were first positive and then negative. When current was passed through one circuit alone, alter- nate coils were energized, producing positive and negative poles. When the current through the first circuit decreased and t-hat in the second increased, there \vas produced a succession of positive and negative poles, shifting from the angular position of the first circuit to that of the second. This shifting magnetic field acted upon an internal secondary member or armature. In the early motors this consisted of a smooth cylindrical core with wires \vound in coils on »4=ut;~:if'_ = 5 'i`= fl 1 3 rf: ` , i. FIG, I2_SI\FETY C.\TC1{ HOLDER OF SWLTCHUOARD FUSE BLOCK "This is used on 1 ooo volt circuits. If the upper plug be removed, the right hand fuse alone is in circuit. If this fuse melts due to excessive current, a plug may be inserted in the upper position, thereby immediately placing the left hand fuse in service.” ln case of short-circuit, however, the whole block was apt to be enveloped in an arc which destroyed the metal terminals, as well as the wood base, the surface, these coils being short-circuited. There weiie usually as many windings as there were total field poles in the two primary circuits. Motors of this type would usually start fairly well and were able to carry a fair load. They took; however, a large magnetizing current due to the limited pole surface and to the relatively large air-gap between the iron of the stationary poles and the iron surface of the rotat- ing core. Furthermore, as the magnetic fields from the two primary circuits enter the secondary at definite inde- pendent positions, a coil on the rotating member in cer- tain positions would confront one field pole only and in other positions might confront one field pole of each circuit and receive induction from both. Hence there was lack of uniformity of action and dead points sometimes resulted. Furthermore, if the ro- tating member were made with definite poles, so that the air-gap might be reduced, the excellence of the magnetic circuit varied for different angular positions ofthe secondary. These difficulties were in large measure overcome by making the secondary core with a large number of small slots and small teeth. In the slots were placed the coils with windings so distrib- uted that the resultant action in the secondary was practically the same, whatever the angular position of the secondary. Later on the primary was also pro- vided with a large number of small slots in which the windings were so distributed that several primary cir- cuits produced a practically uniform rotating magnetic field. In such a field the secondary winding does not need to be specially distributed and the squirrel cage type can be employed in which each conductor is connected to a ring at each end of the secondary. The method of winding in small slots, instead of placing the windings on the surface of an armature or around large poles made a radical change in the design of alternators, induction motors and direct- current generators. The first important machine of this type \vhich was made in Pittsburgh was the No. 3 railway motor \vhich combined a large number of characteristic features, making it the prototype of the modern railway motor. This new type of \vinding ap- parently sacrificed some of the best features of the induction motor. The simplicity of the early machine was unique. The primary windings were in a few coils as simple as ordinary field coils, readily wound, easily put in place and replaced. To separate this \vinding into many small coils to be placed in small slots was unfortunate from the standpoint of sim- plicity and insulation. The early endeavor was to adapt the induction -motor to 133 cycles and by “split phase” or other me- thods to operate it on the existing single-phase cir- cuits. It is no \vonder that little headway was made in solving a problem which scarcely any one would attempt today. The motor could not be adapted to the frequency, and so the frequency was adapted to the motor. FREQUENCY The frequency of the early'apparatus \vas 133 cycles, or 16000 alternations per minute as it was then ordinarily designated. About the time the writer l L V “E” ""` I i TJ 9 ‘Am ff’ 1 =il' _ fi*"§*""""""a . =sl;-1 l _ __ :. ;_ "' Ig- , ' _ rio. 13»".x Monet. cexraar. srarrou" The station at East Liberty typihes the early alternating station. A turbo-generator having ten times the output of the whole station would not take the floor space occupied by one of the six belted units. went to Pittsburgh, tests \vere being carried on to de- termine the performance of transformers at lower frequencies. As adequate measuring instruments were not available, the method of test was to use a large ice calorimeter. The transformer was placed in the calorimeter for a number of hours and the weight of 'the melted ice was taken to indicate the loss in the transformer. Two of the important reasons making a lower frequency desirable were the generator and the Tesla motor. It \vas seen that in order to avoid

Electric Journal January 1914 The Engineering Evolution of Electrical Apparatus-I THE BEGINNINGS OF THE ALTERNATING-CURRENT SYSTEM _(Inns. F. Scorr One of the features of the JOURNAL for the year 1914 is to be a group af articles uutlining in remi- niscent style, the history of the electrical industry. They will review the important step: in the develop- ment of various type; of apparatus, indicating the important change: -which have taken place and painting out the engineering reasons 'why they were considered advisable. These articles, prepared by prominent engineer: 'wltv have been in the fore-front in electrical progresr, will naturally be, ta a certain extent, uf a perspnal nature and will thus have the feature af human interest as well as technical accuracy.-(Ed.) ISTORY may be abstract, or it may be con- crete and personal; it may record events simply as facts, or it may show a continuous sequence of cause and effect. Electrical history is high-speed history. Men still live who were boys when Faraday discovered the principles of electro- magnetic induction, the basis of nearly all that has followed. In the fifty years since the ring arma- tures of Gramme and Pacinnotti, and the drum arm- ature of Siemens were invented, have come our dy- nanios and motors and our electric light and ppwer systems. Nearly everything electrical that we have today has come from forms that were crude and ele- mentary a generation ago or from inventions then unknown. It is a wonderful pictilre-this mov- ing picture of some thirty years of electrical prog- ress., The successive types of generators and mo- tors, of transformers and meters and lamps, of cir- cuit breakers and lightning arresters, of insulators and transmission lines have not come haphazard; they are forward steps to overcome ditficulties or to meet new demands; there has been logical suc- cession and true evolution. Nothing can be more impressive and instructive than to trace this devel- opment and to bring into a few pages the story of the development of a. turbo~generator or a wattmeter, for example, from its prototype of a score of years ago. Electricity was demonstrating its commercial usefulness in the early eighties; an electric car thirty years earlier, and arc and incandescent lighting, shown by Davy seventy years earlier, had been operated by costly batteries and had lain commer- cially dormant awaiting cheap electric power. The dynamo was brought to usefulness in the preceding’ decade. Edison’s incandescent lamp with high re- sistance carbon filament came in 1879. A new prob- lem was pressing for solution-how to get the cur- rent from the dynamo to the lamp and how to sup- ply commercially a number of lamps from one dy- namo in such a way that some of them could be turned off without affecting others. Several lamps were at first connected in series; and operated by current of constant strength, as are street arc lamps today. The method of multiple connection was then proposed, requiring constant potential mains-the system by which over QQ per- cent of the electric power now generated is distrib- uted. Nothing shows more clearly how far from present practice were the electrical ideas of a gen- eration ago than the following quotation from a lec- ture in X878 by one off the most eminentelectrical 'engineers in England. Afteridescribing certain ex- periments in which the candle-power of larnps con- nected in multiple decreased very greatly as each lamp was added, he said, "Hence, a subeiiwasion of light is an absolute ignis fatuus." To maintain constant potential requires dyna- mos which produce constant potential and circuits causing small loss. Lamps of five or ten volts can be operated only a few feet from the source of power without large line loss unless the conductors be very heavy; the Edison lamp for loo volts in- creased the practical distance to five hundred or a thousand feet. This was increased by the three- wiresystem and the feeder-main system. But the permissible cost of conductors was reached well within a mile. Four-wire and tive-wire systems and various series systems which would enable loo volt lamps to be served by circuits carrying 300 or 400 volts or more were found to be unsafe or unsuccess- ful. Electrical distribution seemed limited to a mile or less, except by the series system. A large part of t-he early edition of Kapp’s “Electrical Transmission of Energy” is devoted to the charac- teristics of constant current series motors, the only method in,view by which the high pressures neces- sary for long distances could be secured. The cen- tral stations for incandescent lighting, therefore, seemed doomed to mere spot lighting-the maps of a large city would show spots a mile or so in diam- eter each with its own central station. About 1885 the attention of Mr. George West- called to the alternating~current an instrument by which current high voltage could then be trans- voltage for the operation of incan- He sent an investigator to England inghouse, was transformer as transmitted at formed to low descent lamps. and then acquired the Gaulard and Gibbs patents. These involved induction coils or “inductQriums,” which were open'magnetic circuit transformers.

The New York Press November 9, 1913 Nikola Tesla’s Plan to Keep “Wireless umb" on Ships at Sea Suggests Transmitters Powerful p , i Would DetermineVessel’s Latitude Enough to Cause the harth to , _ and Longitude by Measuring Vibrate at the Poles and Equator. ~ r t ’ t ‘ the Length oi Electric Waves 'Nik°l" Tfsla M’ ¢`°"" f‘”"""'d I” ff/“M , , , l l A revolutionary effect on the methods ol' war- A_ perfect mum* for dvtemrirting not OUT! the ddi!lJ o/ men who recently excited the sri- Tggla 3 Plan tg Learn », _ Y - f-"_ gut-h and qthgg- dn; impqntnt m the "avian", *alia “wid "Nh Hnnwntmmm of dumvny Pggifigng by A The results described are, however, not im- ‘*l'“dl: i5 ‘“'“1‘bl'¢v'b“t *L~U“Y-’°']‘-ll" yur! tg ‘ond .rmmtwn calculated to rrowd #lu bugbmr .i. or pouibte, It is quit; practicable to explode by |1PlJly lt. I refer wah, u,¢_°( ,ht ,mi "f~-‘5¢"¢ffC U’“'f'"C ildfli' W” ‘hf Pfimff (kill. STATIONARY waves discovered lsy A " ( . my, of Hgh! #mine-,at 3 dimnrc N by suing _waves, which were discovered by me ftnirtmx tmdato tafeguurd Ili: liver 0/ rra_larrr.t_ Frm I me fou|1'¢¢|-| yur! ISO an the gre., _V 4 Z # " _ ,q " , V on a mix'mn_ of cm0rim_ and h}_(h,w.n_ C", years hgtj). subject istou technical tobeq. if “P fl-"lf ‘{‘fi’°f<-l 0/ 15' fI""ff"_"~'fr"’f" f meam for determining longitude and ,if ~ __ jf ~ mn duh ny! ‘lm an IW (_"‘p]n),\_d U, l,,,,,h,(c plnined in detail, but the average reader em be rx/ in snvenltn rar? to rvnaligffi;/r ;;cnr-:nj i-Ii; I hmude by wirele“_ Bu! k mu’ be If . I: . ,W > dmnmi" cum.. IMI" bddi M IKM' I div made to understand the Reneril Principlb Liiétpged wi! .1-tier.: tate '45 :gnu Zo' y years before they will be successfully i. ‘ . - closed before the Sew York Aciulcniy of Sri- Tim ¢-at-th 1, R ¢¢|i¢{ug|,|» gf-,ts-"w,y_ ma _.c 1 E;/-na Zmajng ;,L;iLy‘,;‘;u ..];h;1;”`l‘ utilized, » ' , y " » ences the diaemery that tt~><~ntgen,‘0r x‘Y“}'li its such hu its own electrical perlod ot' i-ibn. gut dz 6" Kd Mgmbl _ _ ‘U bt' _mn bday" Notwithstanding its immcnae she, _ ' 'tif 3 ‘yi I projected frorn (`Cfl1\lll'l»\|llr* have the property tion. The time of one complete ilwlllg is ibm lf” M' an 1- §'f’. d ‘T d` th¢ earth responds to st [real number j ~ - _,}£"f » ~",, Q of ntmngly rhttrging an elrttritul rorttlr-nacr at nne-twelfth of one second. ln ottler\vorrl~,'$;| i~i1'"§"Z _fgixm _‘fix,;(;"p{;_;_:_Pff';u;:ff;;;;; of vibrations. When thru excited V _ M f _ ‘ A tlistuiwv. 'l`hr energy so i\ll`\Xll\Ul»\_lf‘lv\f"i"lll)' is the interval the current requires ln pagan! ;my3'€m uploké ,Ac Fwd" magnum G/0 wap i there are lorniid o_n ‘the surface sta- V; 1 % -, _A!%v~ £,:Y A melt, :lolmcairse the igiiitinii ul' ;?{can=r 5] 7 'V & lmgms md “num “Hume mc, 'smug' Whitt a great 'mmrber nf vibrations and can be rt- 1wur-utilized by the wiul¢.u. Bu! Mr. Tesla °f *Nd* WU* P\l°°d ll '_¢§l§`~'1§ff fj’,,fdff,;_ :` _ iii. '. the longer and more penetrativu writes ot' the sonalfdy “cmd Ju" lfkf “ Wi" "1 llflllffd dl' Bdllitr that in all probability there will rome a one of the poles. 'Haas the crests and _:¢ _f ‘_ "fx infnhmd nys "C dmmiwuy mum hw naive' menruons. V When this takes plnee there are Nm mimi iricnce har so harneucd and dev¢l~ hollow: of stationary waves woild ffl' -,i ' Thug 5, H., doubt in me mind that we soon f°"'“°‘l °“ *K* “‘"l“"- ‘fFf“°“"Y_P“'“u'¢l fifdsl 'vfsd the means at hand that .tuck result: may be in parallel circles, with their planes 1'"=>55-':,'if§*ii`,`§ffi-;'.% " ' . shell be able to project ericrgv at a distance not “I °‘|““l °1°°"““l “'*l"'“7’ “'l"d‘ “‘" bf* "~‘° b¢"¢b‘“i'*¢d- MV' Tub -"U /"Wh /0' "°dlT| ll ri|lal usyles to the axis of the earth, l .‘- onlv in small, but in large druountsjzrntl what "“]°d bl’ P'°P°fl}'- 3“““'fd i¢“5lmm¢f\|‘- of The Press his 1,-ie-ws on the two subject! GI and fmm rg”-Ln' F f` pm' 1 -$5i§:E- - ~_ h ' ff f h h'i‘ t _ill l .- . , /°’u°""" ated inatrmnent thsoelistanee ofllu vb- ':~-:- il lf;f53-iilA5.`1l"f'?f_;flii:'iiiiffl l if isdn; iiirlidititilris an el Trlnumner at one af um Polu' --- - 'l€i’{ii~\5'-". v "’l -5'5"-5'.'.',f’!’55551f?l’f55<~ iff - ` Ima ine that a transmitterca able t '~. “I °"7"°| lb' 'un' ffm” U” P°l“1 ‘-3‘ii‘ili‘l"1i"'i ’"""5':[:”`i:;i;"5?'l5:i:” ` As regards the determination ut' latitude and . E ‘ P O “CL . . ,2»g¢§§'¥‘;;;;;-'{, £;,;,v,5 r,;i5'gi?_,';’=§,E',5¢ !~;-§a="ft¢ » _ ' _ , th th ‘ l d I th I l BV- NIKQLA TESLA' °"““’ *’° '“".“ °°°1' ““"' ‘°'=“““°" ftitsiitiihr V f- . ~ louifudf of A == bv 'hm '= iii.” ii.§“1.¢,;°ili° iliioii 'ffftift aitiiiff, HE first and incomplete announcements the lahtuda. §isii.§;i¥ " ij' ' nothing in use as yet which would make such wav" www be in arénld drdm with th; ot" technical advances should always lnlie manner, ifllrlnlmitiewut __Eii;€;Z§l2§§§*Qf{;; gl 2 ` _ direct observation possible. Some suggestions, planes M right anglesm the axis éf [ht arg! - ‘ < - . , ._ ». -:ei 12+ > <:: t- 1 "1 » 1, r ', :::, :_ ._ at, . » . . ., , . be taken with rt grain oi salt. lt 15 pllveil A! I poml on Kiln ¢¢|llif0f,_|.& _if howet-cr, which l have since many years adio- and from rudings of 3 Properly gmdumed in: me that the newpaliers “_” genius more md |°“¢"“k °°‘ub° P'°°’¢l7"l*¢¢'“°°‘| .‘.li?§§"i " if ;ifii5iff?5'§‘i7€§il‘fi!' cated' ha" been “d°P&d` _They Ji? the ‘lashing strument the distance ot a vessel curving the mvireaicuumtesnd rehax an PUISIHS for-ih Teh by the some mans. The but plan QI? p Q oftime signals ‘over ri wide area and thecimi same from the Pole émld be I! (mee Yéld` Sip i$o:;i51e\;t&in1;e\'e e ess. e ne s re~ 'mu bc to Phe* mn. tnnnnin-_L“ i ploynrent of an instrument known as a. utr ess inyacmrmdy tht gmgmphkd lm. I _ ~ Fw,” cha,” ,ohh on Q.. 'o /ur -c»t,,>. 'rc st,/A V 0 compass. l-'or instance, not long ago reports were widely cinailated that powder had been es- ploded ardistanee by in-fre-red Oeeultra-vinlet nys, and that a ~British battleship had been Bed in af tat of this kind, which provedf me ce.\sluL The dispatchu gate great opportu- nity to sensational speculation, but the truth is that there was no novelty ujhateveriin what was done. as to “asian tm. m.aa.¢f¢»»1. -` systems oi stationary waves pt right anglais one smother. if Haiswen- donainnumrablaruulhofthegnat. eatpraeticalvalneeouldlvelvdllhbi A mine or rnsnzine mafhsvebem blown up, but this bras accomplishd in A well-known manner through the application ot a kind of electrical u."aves which are now generally adoptfd in the trrmsrnission of signals- arirlmut vtiires. Similar eiperimenn were performed in this country many years ago oy myself and oth~ ers, and quite recently john Hays Hammond, jr., his done creditable work inthis direction through the application of an art which has been named "'I`el|.utomstiu,"’ or wireless oun- trol of moving mechanism at a distance. By means of-such t¢l.|Luuanat.ic,ime!s, .mr- face, submarine or serial, s perfect system of 'coast' defense eur be Toqndeeo on this plus also can beonntrolled from butle- Ahips, and there is no doubt they sotnerxttflater will be adopted and their introductim willlnve -Plan for Finding Locations. These means enable an expert on a vessel to ascertain the exact hour at any sendinl sta- tion lwithin reach, and also, ihian imperfect .1ng_ng;1_Lhe direction in which it is situated, and from these data it is possible to get a rough idea of_the position of the ship relative to thc points of reference. Tn like manner, if a transmitter trereptarrd atapoinxou tln:liq,r.\Atnr.tl1:l9_t\H_tude could be precisely detennined by the same meant. But the best plan would be to place three tr-:na mltters'at properly chosen points on-the-globe; as to establish three non-rnterferable systems ut stationary tvaves at right angles to one another. If this- were done, innumerable results of the greatest practical value could be realized.

x26 THE ELECTRIC JOURNAL same instant, otherwise, the brushes on one cominula- tor would, at times, short-circuit the current from the other commutator. With the advent of larger belted machines, and of engine-type machines in particular, the compound- ing ot' polyphase machines was more or less unsatis- factory a.nd \vas practically abandoned. To compen- sate for the lack of compounding, better inherent regulations were aimed at in the designs. This meant. primarily, machines which \vould give comparatively large currents on steady short-circuit, three to four times full load being rather common, and even six times full load being attained in some machines. The momentary current rush at the instant of short-circuit must have been excessive on some of these machines, due to their very low armature self-induction. I‘Io\v- ever, due to the relatively small ampere-turns per pole, no very destructive distortions were found in practice. This characteristic of the short-circuit cur- rents was carried into the rotating field construction, and even into the early turbo-generator \vork. This practice of giving the alternators good in- herent regulation was expensive in a number of ways, as it usually meant higher iron losses and less output than \vas possible otherwise, \vith a given size nia- chine, or a given amount of material. Even at this early date, it \V3S recognized that some form of auto- matic tield current regulator which would maintain the terminal voltage constant, regardless of the in- herent regulation, \vould be a very useful piece of ap- paratus. Some form of regulation which would take care of change in po\ver-factor, as well as load, was the aim of many designers. Among the different schemes brought out, the Rice method of compound- ing, brought out by the General Electric Company, is of interest. This was used principally \vith rotating field alternators. In this scheme, the exciter was usually placed on the same shaft as the alternator field, and, in such case, had the same number of poles as the alternator. The leads from the alternator arniature were carried through the exciter winding in such a way that a lagging current, carried by the alternator, tended to strengthen the field of the exciter by shift- ing the armature reaction with respect to the exciter field poles. In this way a compounding action on the exciter was obtained which \vas practically in propor- tion to the demands of the alternator field with vary- ing power-factor. In the case of engine-type ma- chines of comparatively lowvspeed, the exciter was geared to the alternator shaft, so that it ran at a con- sidcrahly higher speed and the number of poles in the exciter was correspondingly reduced. This method of compounding was effective, but the whole combination \vas apparently unduly com- plicated and expensive. Furthermore, it did not give the desired compensation under all conditions of op- eration, as it would not correct for changes in speed. A later method of compensation for power-fac- tor \vas devised by Alexanderson, and was used on a limited number of General Electric machines. In this scheme a derived current from the alternator itself was commutated in sucli a manner that compensation, proportional to the power-factor, was obtained. This was a purely self-excited alternator scheme and, like all self-exciting schemes in such apparatus, it was sen- sitive to speed changes, probably to a 'much greater extent than the Rice arrangement above described. A fundamental defect in all- self-exciting compensated alternator schemes lies in the fact that stability of ex- citation is dependent upon having considerable satura- ton irrthe alternator magnetic current and, coincident- ly, if there is such saturation, the compound current has no direct relation to the load or power-factor. Thus such machines are either sensitive 'to speed changes, or their compounding is only approximate. Following these scheme came the use of auto- matic regulators of \vhich the Tirrill is best known. This regulator acts directly on the exciter field by short-circuiting a resistance ‘in series with the field winding, the range of exciter voltage being controlled by the length of time the rheostat is short-circuited. Instead of cutting the resistance out insteps, which tends to give sluggish action in the fields, the Tirrill regulator cuts the whole resistance out each time, and the length of time is varied. This results in quick action. As the regulator tends to hold constant volt- age at the alternator terminals, or on the line, change in power»factor or in speed does not modify the action. This type of regulator has proven very effective, espe- cially in the case of alternators subjected to sudden and violent changes in load, power-factor and speed. With the advent of larger alternator units, in pro- portion to the changes in load, the inherent regulation has been made relatively poorer, primarily because better machines otherwise are thus obtained. The short-circuit currents are reduced, and relatively lower iron losses, and lower temperatures or, higher out- puts with a given temperature, are obtained. This has been carried further in turbo-generator design than in any other class of alternators, due partly to funda- niental limitations in design. However, this poorer inherent regulation has proven to be of no practical im- portance, where suitable automatic regulators have been used with the machines. One fallacy \vhich was frequently found in the past, and which still persists to' some extent, is that alternators should have equal inherent regulation to parallel properly. This is based partly on the feeling that the field currents of the alternators should vary over equal range when carrying their proper propor- tion of load, together with the knowledge thiififhe vaé riations in field current are dependent, to some extent, upon the inherent regulation. However, the fact that the shape of the saturation curve, in a given alternator, mayhave much more influence on the excitation, es- pecially at high saturations, is usually overlooked. (Ta be continued)

THE ELECTRIC JOURNAL 75 ture copper to carry the current at the 60 kilowatt rating. This, therefore, represented a big step in the development of the American type alternator. It was found that all the other V\/estingliouse standard cast iron machines of the rotating armature type could readily be changed in line ment. with the above improve- COM POUNDING ALTERNATURS the 60 kilowatt machine The compounding of was not a ne\v feature, for already some of the lami- nated field toothed-arniature type of machine`s had been compounded, in orderto improve their regula- tion. Two different lIlCll`|O(IS“Df compounding alter- nators liad been developed by the Westinghouse and Thomson-Houston Companies, respectively. In the Westinghouse armature construction, the armature discs were punched in single pieces, with spokes, and were threaded directly on the armature shaft, no spider being used. This construction is illustrated in Fig. 4. In the assembled armature, the spokes were therefore of laminated material. These laminated spokes were utilized as the core of a compounding transformer. One lead from the armature winding \vas carried around the spokes of the armature before passing to the collector ring. This winding formed the primary of a series transformer. The secondary \Vi'lS also wound on the spokes, and -the two ends were carried to the bars of a rectifying commntator on the shaft. The number of commutator bars \vas eoual to the num- ber of poles. The alternating current from the sec- andary winding was by this means changed to a pul- sating direct current. In the Thomson-Ilonston method of compound- ing, the main arinature current \vas carried directly to a rectifying commutator, and, after being conimutated, was passed to the field-compound winding, and back to f if s QQM 0323* ‘ gy FIG. 4f5I\liTClI DF C0l\|I'ENS1\TI>lll TYPE OF WINDING the commulator, and then to a collector ring. The main armature current tliercfore passed directly through the field, while in the \Vestinghouse method the sec- ondary current from a series transformer \vas passed through the held. Both methods represented series compounding, and gave practically equal results, but there \vas much discussion as to the merits of the t\VO methods. Both of these methods delivered pulsating direct current to the field winding. There was consid- erable inductive e.m,f. set up in the field windings by this pulsation, and this tended to cause inductive dis- charges across the rectifying connnutators. In the '1`homson-Houston method this trouble \vas overcome to a considerable extent by the use of a non-inductive shunt in parallel \vith the rectifying commutator, i.e., f.,i= ' tk m=~ }f,_,g:..e _} , g s d ' ` ». ~ wg ` gy *H 1 `f'" :Brie F-s " Q ._ _/ 1, , _ " ,,. _ *' 'Q ; / ~ ~ :Il 1,-_,,.,, ._ =.» sh!-11-2 _e ~..', ~ ;, _ at t.. t~_.»w Fi; 4 . }; 1) 1 "I-‘.`ifI" flffri f ~ ` 'xi » `=`:° 7'4" »1 f, _ f ` .f'- 1' w..-.» , ,..~>,»,. ¢_{,.- Us _ , FIG. S*E1\|i|.\' WEST|NCIl0U§E 60 K|I.O\\'.\TT .\L'l'ERNf\'|`0R \VITI| (fl)l\II‘ENS_\TlNG “'INl|IXti across the compound \\'ll\(lll]g. In the \\'estinghouse method a similar result \vas accomplished by saturat- ing the series transformer (or armature spokes) to such a high point that the inductive kick from the field could readily discharge ‘through the secondary winding of the transformer without giving high enough voltage to fiash across the commutator. The details of this method of compounding have been gone into rather fully, as this compounding \vas, at that time, an important step in our progress. The fact that of all these machines were built for single phase, allowed us to use such compounding. \Vith the advent of polyphasc generators, such methods of coni- pounding soon disappeared, principally for the reason that a great majority of the early polyphase machines handled separate single-phase loads on the different phases, and it was not practicable to compound for these independently. The ahove toothed type generator came into use about 1890 and lasted for several years, or practically until polyphase generators actually came into fairly general use before true polyphase loads became com- mon. These toothed type generators allowed the use of relatively high voltages, as far as the armature winding \V1IS concerned, so that 2200 volts became comparatively common, and even 3 goo volts or higher \VIlS used in some cases, In fact, the limit in such machines :\ppe:\|'c

THE ELECTRIC JOURNAL 37 Without the transformer and the polyphase sys- tem there is no means at present known by which the extension of the use of electricity could have made one-tenth of the progress that it has made. It is easy to recognize this now, but it was not so easy to fore- see. In fact, there was criticism and condemnation of the alternating current by experts, and there was antagonism and opposition by commercial interests. The foresight, the courage and the wonderful con- structive ability, persistence and power of Mr. West- inghouse made him the great human factor in the recognition, introduction and development of the alter- nating system, and, thereiore,qn the electrical devel- opment of the past twenty-tive years. Those only who were associated with the com- pany before the writer went to Pittsburgh have been mentioned. Among the first of those who followed and who have had a great deal to do with the subse- quent development of apparatus, including some of the types to which reference has already been made, were ~Messrs, Lamme and Storer and Skinner and Davis. It is anticipated that further articles by various men will trace the engineering steps which have led up to the etiicient apparatus of to-day. Present practice is the outcome of the ettorts of many workers in many places. The particular thing which may bear the im- press of a particular inventor or may be put forward with energy by one company or another may flourish for a time, but merit determines its final disposition. Among the types of apparatus which are now in com- mon use and in many cases are manufactured by sev- eral companies it will be interesting to note that a considerable number had their origin Pittsburgh. In many cases the idea originated with a Pittsburgh in- ventor. In other cases an acute engineering instinct has selected, combined and put into operating form apparatus or methods which were previously unde- veloped or experimental.

Electrical Journal April 1914 The Engineering Evolution of Electrical Apparatus-IV THE ALTERNA'I‘ING»CURRENT GENERATOR IN AMERICA (Concl.) B. G. LAMME Tulum-cr;NaR.».roRs HE ADVENT of the turbo-generator has had a predominant influence on alternator design. After the tiirbo-alternator once became estab- lished commercially in this country, it quickly revolu- tionized conditions by driving the‘large'engine-type al- ternators out of the field. The evolution of all elec- trical apparatus has been comparatively rapid, but that of the turbo-alternator has possibly exceeded anything else in the electrical field. This evolution -therefore merits a fairly complete description. The first turbo-alternators, built by the Westing- house Company, \vere installed in the power plant of the \Vestinghouse Air Brake Company about 1898. There \vere three rotating armature machines of 300 kilowatts capacity, which ran at a speed of 3 600 r.p.m., ."_1‘ »- ~' , I .win iw. ir- ff! ' r ;- i ‘ ' L' l 'rl ` i -l l' T l 1 ,~ ~ - '1- ~ V ` If r- l ._ i ll - »' . V Q ~- i* L- il 1/ ‘ ~ ef.- ; *= _ ;f=~=' "`" ` , _,~ .»l , -V ». \°`;“f' ' rs :~ I ` __,, _ ?`I_;'§:?x;* FIG, 20»FlEI.D DF EARLY IKDTATING ARMATURE TURBO-GENERATDR giving 7 200 alternations per minute, or 60 cycles per second. They were coupled to Parsons turbines, built by_The.Westinghouse Machine Company. The Par- sons Company in England had been building rotating armature alternators for a number of years, and the Westinghouse Company simply followed the Parsons' precedent. These first machines were operated for several years, bitt it was obvious, soon after their in- stallation, that the rotating armature type of machine would not serve for general turbo-alternator purposes. It was evident that, for voltages even no higher than 2 200, the rotating arinature construction, at the neces- sary turbo-generator peripheral speeds, would 'become almost impracticable. Attention therefore was soon turned toward a 3600 revolution, two-pole, rotating Held type, and a very large number of possible con- structions were considered. Finally one like that shown in Fig. 23 was worked out and built in 1899. This had the field windings completely embedded in a number of parallel slots, \vith supporting metal wedges at the tops of the grooves or slots, One machine of this type was built and tested, It operated in a satisfactory man- ner, except as regards windage and noise. The ma- chine was not closed at the ends, like modern turbo- alternators, and thus any noise generated in the nia- " _;= _mu»~nsf.s».== __" \.. 773 J. ll _¢.~ , - _,, _ f . 4 , _,__ f f ‘ i .."`T; . »- ii /A 3 " 7' ‘\_l` FIC. 2l-:\RM.\TURE FDR '|`UR\1O'GENERAT(l|( OF TYPE SHO\\'N lN Flti. 2U chinc could he readily transmitted to the outside. The noise \vas caused largely by the two flat sides of the rotor. lt \vas so shrill and penetrating that it was very disagreeable to he around the machine, and \vas even painful to the ears after a short time. This con- struction was therefore abandoned temporarily, but after a few months it was taken up again and a new rotor was built which was entirely round, as shown In Fig. 24, but was otherwise very similar to that shown in Fig. 23. This new rotor, although noisy compared \vith modern machines, \V1\S so quiet, com- pared \vith the First construction, that it was iinme- diately adopted as a standard construction. This is the no\v well-known parallel slot construction which has been used very extensively by the Westinghouse Company, although many very radical changes have been made in the constructive features of the rotor it- self. This type of rotor \V3S used originally only for . :' i~-wyfném 'g " V.f.' A *HI "‘~'- he. satire iii ~~ -..z .-,V _, ,_ L I -ltlhe; .~, “ ‘ML gt .- \ 0, ' , Y -=. r' 1, i ‘_ _el 2; ,/ _` V f' I "dr 'i FIG, 22~l ooo KW OPEN T\'|'ii 'ruittxo-t;£Ni€H.\Tou the 400 kilowatt size at 60 cycles. A In the earlier machines of this type a number of very curious conditions developed, In the first ma- chines the rotors were built of a number of thick discs or “cheeses” side by sirle, which \vere put on the shaft at high pressure. The two end discs \vere thicker

I24 THE ELECTRIC JOURNAL and consequent low resistance. The earliest form of damper used in this country consisted of copper rings surrounding the poles and copper tips overhanging the beveled pole edges. This was the form most common- ly used on converters. On alternators, in some cases, the damper consisted simply of a lO\V resistance ring around each pole. In still other cases the damper con- é i ‘ J .. ,ttf i _,ri _. . 5" ~‘\ x . .j7~__,, _E%?, Fgffe I yi 3 i 7' ` ..ff, » ;` 1 ,a :ty bi \§4~_,:s“ L . oil ‘ 1 ‘ l` \\ ,_ `\_ ' `~~".< \ . " $1 ,>?z,e.aikx,.._ / _V “_& .‘ ' 4 - ni .4 FIG. 177GRlD DAMPERS ON FIELD POLES sisted of a heavy copper plate covering the pole face. This latter construction was only possible in machines with large air-gaps and very narro\v or partially closed armature slots. These crude forms of dampers were gradually superseded by the so-called “grid” damper which consisted of a copper grid surrounding the pole and with ribs which lay in slots in the pole face. These various types of dampers are shown in Fig. 16. In very few cases were these old types of dampers so interconnected as to form a complete cage \vinding around the field. Many tests were made at various times to deter- mine the effect of interconnecting the grids on the different poles to form one complete cage. As a rule, there was no appreciable gain, and it was then as- sumed that such interconnection had no material ad- vantages. HO\\'€V€f, it later developed that the rea- son why interconnectiion of the dampers did not im- prove the damping action very materially, was due largely to the very great amount of copper in those parts of the grid dampers lying between the poles. .-' ,ff--A , ...,.,,....,.»=,~»»..|.;~;“;|=' 1-#wiv f '. - - -. ' fl*a ' E ‘ . __ _' ~ ~»\=. Wi "-'P _ , _ 4 i FIG. 18-CAGE WINDING TYPE D1-` IIAMPI-Lk The grid damper was very effective, but was expen- sive in material, and was not easily applied on poles with overhanging pole tips. This type of damper was gradually superseded by one smilar to the usual cage winding on the secondaries of induction motors, and this is the type which is in most general use at the present tinie. This construction has practically the same effectiveness as the old grid type, but is much more economical in material and, being placed in par- tially closed slots, it does not as greatly affect the‘iron losses in the machine, as was liable to be the case with the open slots, generally used with the grid damper. With the gradual ‘introduction of dampers and improvements in angular rotation of the prime movers, hunting troubles in alternators practically disappeared, and parallel operation presented no difficulties, except under very abnormal conditions. Apparently these dampers or “amortisseurs,” as they are sometimes called, were first proposed by the French engineer, Maurice LeBlanc, about 1891. However, they were “rediscovered” in this country by engineers who were not familiar with -the above engiineer’s work. VOLTAGE WAVE FORM The e.m.f. wave form of alternatingfcurrent gen- erators has been a matter of much discussion since the early days of alternator design. The old surface- wound machines gave a very'-close approximation to a perfect sine shape, due to the arrangement of the winding and to the very large air-gap. The first toothed armatures, with their very small air-gaps, gave waves which departed very widely from a l_ll_| l_|l_l FIG. I9-VOLTAGE WAVE FORMS Of early toothed armature machines and of later toothed ar- matures with larger air gaps and beveled poles. true sine. In fact, this had about the worst wave form of any of the alternators which have been put out by the Westinghouse Company. Ita shape was some- what like that shown in Fig. 19, as ~would now be ex- pected when the configuration of the armature tooth tips is taken into account. The later toothed arma- tures with large air-gapss and beveled tooth tips gave much better wave shapes. With the advent of the true polyphase windings and the slotted armatures with several slots per phase per pole, fairly close approximation to sine shaped e.n1.f. waves became common. In the first Niagara Falls 5000 horse-power, two-phase alternators, the voltage wave was slightly Hattened on the top due to the fact that the pole face width was somewhat greater than the width of each phase group in the armature. .When very high voltages came into gen- eral use, and especially in machines with small pole pitch, the number of armature slots per phase per pole was reduced to a minimum in order to lessen the total insulation space. In extreme cases, but one slot per

THE ELECTRIC JOURNAL 79 type, but the inductor type, as a commercial proposi- tion, soon died out. I ' , One of :the interesting peculiarities of the in- ductor type alternator, as usually built, was in the enormous stray field appearing in the shaft, bearings, bedplate, and sometimes in the' engine-governing mechanism in engine type units, necessitating in at least one case, the use of brass governor balls. -In the usual construction of inductor alternator, there wa-s but one exciting winding. The magnetic circuit and the ficld winding were arranged as in Fig. 8, which show both the Stanley and the \/Vestinghouse constructions. The normal or useful path`pf the magnetic flux is in- dicated by the dotted lines a, a. " Obviously, the field coil w-hich set up flux through these paths could also send magnetic fluxes through the shaft, bearings and bedplate along the dotted lines b, b. Moreover, if the two bearings were not connected by a magnetic bedplate, as might be the case in engine type machines, then, in two-crank engines the engine cylinders ami other parts became opposite poles of a very powerful electro-magnet, when the field coil was excited. The mi n j ` 4 i in 'i Wi' - 1 '4‘l“_""l |||l|ill |-lui, i ll Illllllllll MWNI' 1 . ' __ __ " ' ' lllllllllfxllllflllll FIG. 8-SKETCH OF MAGNETIC CIRCUIT UF AN INDUCTUK ALTERNATOR stray magnetic field set up in engine type units was sometimes so strong as to interfere with the governing mechanism. Also,'ivith a strong undirectional fiux between the bearings and shaft, each bearing became part of a small unipolar generator, of \vhich the bear- ing surfaces formed the brushes. In some machines, quite 'heavy currents were generated in the bearings, sufficient to “eat away” the bearing surfaces or to pit them so that bad bearing operation resulted. As this was primarily a magnetic trouble, insulating the bear- ings from their pedestals would not stop the action. To overcome this trouble, the Stanley Company added a “bucking” coil placed around the shaft at one side of the generator, this coil being in series with the main field winding and magnetizing in the opposite direc- tion. The ampere-'turns of this bucking coil being made equal to those of the field coil, the resultant ampere-turns between the two bearings would he zero. Obviously, in an alternator with a bedplate and two bearings in which the armature frame rested directly on the bedplate, a single bucking coil at one side of the machine would not neutralize the stray field through both bearings. ROTATI NG FI ELD GEN ERATORS Considering next the rotating field type of ina- chines, possibly the earliest example was the Niagara type, mentioned before. This had an internal sta- tionary armature, with \vindings on its outer periphery like the ordinary rotating armature. Outside this was the rotating field, consisting of a heavy forged steel ring with inwardly projecting poles. However, this type of construction was relatively expensive, and was never adopted generally, The more modern rotating field type of alternator, \vith external sta- tionary armature, was a rather gradual development and, during this period, there \vas much heated dis- cussion as to the relative advantages -of the rotating field and rotating arma-ture types. The rotating field gradually superseded .the rotating armature construc- tion for a number of reasons, the principal one having to do with the armature windings and voltages. In the rotating armature, the end windings \vere more difficult to support than in the stationary armature, Also, with the gradual advent of higher voltages, the stationary winding proved to be far superior. Huw- ever, as a goodly proportion of the alternators built during_this transition period were of the engine type and for lo\v voltage, in \vhich heavy bar \vindings could be used, (such being conditions under which the rotating armature made its best showing,) this type persisted for several years after the rotating field type became commercial. Gradually increasing voltages, however, necessitated the use of stationary arniattire machines, for at least part of the business. The manufacture of two types of apparatus for the same general purpose could not persist, and eventually that type \vas adopted exclusively, which allowed both high and low voltages. By 1900, the rotating field alter- nator had come into very general use, and the rotating armature type \vas disappearing. This rotating field type has persisted until the present time, although many minor modihcations have been brought out from time to time, due largely to change in speed condi- tions, etc. i V In the rotating field development, the tendency for a mnnber of years \V3S strongly toward the engine type construction and relatively low speeds in many cases. The construction was carried to the extreme, in some cases, \vhere the usual flywheel capacity re- quired for the slo\v speed engines \vas incorporated in the field structure of the alternator itself. In some cases, this meant enormously large machines for the output. A prominent example of this is found in the seventeen 6000 kilowatt engine-type machines de- signed in 1899 and IQOI respectively, and installed in the Fifty~ninth and Seventy-fourth street power stations of the Intcrboro Rapid Transit Coni- pany of New York City. As an indication of the changes taking place in the electrical field, it may be stated here that arrangements have been made recently to take out a number of these machines and install in their place 30 000 l<\v turbo-generator units, '1`he exist-

122 THE ELECTRIC JOURNAL but, in general, this type ot' winding requires an open slot construction. However, \vhen the stationary armatnre construction came into general use, the ad- vantages of the overhanging tooth tips in supporting the coils largely disappeared. There remained there- I * ,y __ \ ,;.\ ft \ \ .\1¥` 'gc . - ~ 2 .-‘R ~ ~ /t _ . J ;~ . ¢ I ;¢, Q ;7<;. V,-f / ~ 1" 5 /f' ` : " -/ vv,,,/ .'...T-L _ _, iii' - Zil"::. ‘ -.f V1/, ' tlfr ' :» "1 ";,;:'1. _J" , . 1175* ‘ ‘: z Itnnv ts* .N ,,. .Qq\,_\ ~ FIGS I3-I1Ul'L1tu\TlE ColL 'IYPE OF WINDING, Two COILS YER swf fore thc disadvantages of the Flux bunching, against the advantage of coil construction, if open slots were used, However, thc use of laminated poles, and the judicious proportioning of the air-gaps and fiux den< sities, to a grcat extent eliminated the losses due to open slots, In consequence, the open slot construc- tion and the duplicate type of armature coil, have ap- parently conte to stay, in this country. Various attempts have been made to obtain the advantages of both the open and the partially closed slot arrangements. Probably all large manufacturers of alternators have tried some form of magnetic wedge, instead of the usual libre or wood wedges which serve to retain the coils in the slots. Another arrangement is the equivalent of combining two or more open slots in one, with an over-hanging tooth tip, which covers the slot with the exception oi the width of one coil. Two or more completely insulated coils are fed successively into the slot opening and arranged side by side; This does not give any nar~ rower slot opening than with theopen slot construc- tion, but the number of openings is reduced to one- halt', or one-third. This construction is used rather extensively in the rotors of large induction motors, but apparenty is but little used in generators. Bracing of the end windings against short~circuit shocks has been a comparatively recent practice. The necessity for such bracing has been dependent to a considerable extent upon the output per pole, and the old time machine seldom had such a large output per pole that the short-circuit current-rushes were sutii- cient to cause dangerous distortions of the end wind- ings. However, such bracing was used on the Niagara machines, previously described, and also on the Man- hattan generators above referred to. These, however, were very rare instances. However, with the recent high-speed, high-output water-wheel generators, the outputs per pole have become such that some form of end bracing has become rather common. Modern Westinghouse machines of this kind are braced to stand a dead short-circuit across the terminals without damage to tl1e windings. Under this condition, these large machines may give a momentary current rush of from ten to twenty times the rated full-load current. However, the bracing re- quired on the end windings of such machines is of relatively much less importance than on turbo-gener- ators oi corresponding capacity, due to the fact that, in the former class of machines, the end windings are relatively short compared with those of turbo- generators. The above description brings us practically up to date, as far as the ordinary synchronous alternator is concerned. No description of the development of the turbo-alternator has yet been given. This forms a rather distinct developmen_t_which should follow at this point presumably, but`it is thought advisable ‘tof interpolate here some description of the problems of parallel operation, wave form, regulation, etc., which came into prominence and were practically taken care of previous to the advent of the turbo? generator on a large scale. PARALLEL opaim-r1oN or ALTERNATDRS One of the great problems which developed in the- operation of alternators was that of the parallel run- ning of two or more units, At one time this was at very serious question, but in recent years, it is very' O. ... ,.,-, _., _ _ ._,».\ ‘ ,. ‘V \~ \ \`:` §‘.,,-" f /,/' ~. my-,?‘ .. ~ \\) `\"';= e' _ 7' ' 7: "ca - . ‘ t la ' th-2 ’ i v~‘ 1 ' _. ,_-' lqzjg .. _ .ca ,_ _ ' f e 1° ` ' 4. 1~=~.,__ /. , ~n_ ` 2 5Fi"' c _ ,if -4 ;_ _ 11: ` ‘_ . 7. .' I gg.; _ ~ 1 9' . I \` l' "’»` ‘_ ' \ ` f; I ` ._ .,5_i3¢_; , . ,_ A-wi-‘ , ;~`~ .» _ §""'f' ii: ,~~=\¥= t “"f" ‘*~..-'1Q§ ».[,-'.' ;jy$;;, _ _,,l§_' ' if FIG. l4~°-DETAIL VIEW OF THREE-PHASE CONCENTRIC WINDING seldom heard ot. Considering the almost universal practice of paralleling alternators, which holds at the present time, one might be led to wonder why there ever was any trouble. Far back, in the days of the high-frequency surface-wound alternators, parallelirig was attempted in many cases and, not infrequently,

THE ELECTRIC JOURNAL 29 They were connected with their.primary windings in series, while their secondary windings had the same number of turns as the primary and supplied independent circuits. The system employed con- stant current, and the lamps on the secondary cir- cuits were subject to serious changes in voltage when the number of lamps on a transformer sec- ondary circuit was varied. Mr. William Stanley, who was then engaged principally in the development of the incandescent lamp for Mr. Westinghouse in Pittsburgh, had been much interested in the alternating current. A con- tract arrangement was made by which Mr. Stanley should undertake the development and adoption of the alternating system for commercial service. In the fall of 1885 he set to work in an old rubber mill. at his home in Great Barrington, Mass., and con- structed a number of transformers, each wound to reduce the 500 volt main line potential to too volts in their secondary circuits. These transformers differed from the Gaulard “inductoriums" in having the primary wound for a relatively high potential and in having the primary terminals connected in parallel to a constant potential circuit. The coils were made with a closed magnetic circuit and the general proportions of the transformers were re- markably similar to those of the modern “shell type,” The idea of connecting a primary coil hav- ing a resistance of only one ohm between the mains of a 500 volt circuit was so palpable' a violation of Ohm’s Law as to shock the convictions and the ex- perience of those who were familiar only with di- rect-current phenomena. It was a bold idea of a daring inventor who first did that with which all are now so familiar. Regardless of popular ideas, however, the transformers gave good promise and a Siemens machine which had been imported from England for tests at Pittsburgh was employed as a generator. The transformers were erected in the spring of 1886 and properly connected, and supplied a number of stores in Great Barrington with cur- rent‘on a commercial basis. The plant continued in operation for several months until a screw driver was accidentally dropped into the dynamo and wrecked the coils. The success of the initial plant led to the commercial adoption of the alternating- current system by the Westinghouse Electric Com- pany. The misgivings o_f experts, the apprehen- sions of the dangers of high voltage, the antagonism of opposing commercial interests did not prevail and the little “twenty-five light” transformers opened the way for a new era in electric development. After the wrecking .of the Siemens machine, a new alternator, originating in plans made by Mr. Stanley, and worked out in detail designs by Mr. Shallenberger and Mr. Schmid, was built in Pitts- burgh. A full equipment of commercial apparatus was quickly designed and manufactured, and soon alternating-current central stationsappeared, first at Greensburg, then at Buiialo and elsewhere. Two years after the starting of the Great Barrington plant there were about a hundred alternating-cur- rent installations. THE ALTERNATING CURRENT IN 1888 Having been asked to write the First of a series of historical articles on “The Engineering Evolution of Electrical Apparatus,” it is but natural for me to go back to my own early experiences as a starting point. I have already given a preliminary survey of the electrical situation, and I shall now make a sort of an inventory of the kinds of apparatus which were being made when I took up electrical work in Pittsburgh about twenty-five years ago, and shall comment upon various points. ' In the early part of August, 1888, I went to Pittsburgh and happily found that a personal appli- cation was more effective than correspondence in securing a position with the Westinghouse Electric Company. I had a slight acquaintance with' Mr. L. B. Stillwell, then assistant electrician, as I had met him nearly a year before when he came to the Baldwin Locomotive VVOrks where an alter- nating-current lighting plant was being installed and where I was then employed as wireman. Mr. Stillwell showed me about the laboratory in Pittsburgh, poihting out particularly two new kinds of apparatus which had recently been invented. One of these was the Shallenberger meter, an induction meter for registering the current used by the con- sumers on alternating-current circuits. At that time the chemical meter was generally used on direct- current circuits, and there was no commercial alter- nating-current house meter. The Shallenberger meter (which was already in substantially the same form which it maintained for a dozen years, during which time enormous numbers of meters were made) was the outcome of the observation oi the peculiar motion of a spring lying upon an alternating-current arc lamp about four months earlier. Mr. O. B. Shal- lenberger, who was working with the lamp, investi- gated the motion of the little spring. He substi- tuted other things in place of the spring and de- termined that the motion was due to the joint action of the magnetic fields set up by two circuits, in one of which the current lagged slightly in time behind the current in the other. Close observation, careful ability analysis, intelligent experiment, remarkable in designing and proportioning the _new apparatus, which was to embody in commercial and useful form the principle exhibited by the moving spring, resulted in a few months in a meter which was the forerunner of the many types of induction meters which are now in general use. The other new invention was the Tesla motor. Nikola Tesla had secured his patents and 'had pre- sented a paper before the American Institute of Elec- trical Engineers, in the preceding May, describing the

30 THE ELECTRIC JOURNAL rotating magnetic tield produced by polyphase cur- rents and the means of employing -this in induction motors. The patents had been acquired by the West- inhonse Company and Mr. Tesla was then employed for a 1 500 light dynamo of the direct-current type would have an aggregate width of 20 inches. This ratio is fairly illustrative of the relative requirements of the two systems in all their transmitting parts. Mr"""-"-"~rf=='T'T1zf""::Tf**7r,;[email protected],. 1 " ' gi' _ . 3--o - 1,~. ,.¢, away, `:’ » ' " 53? '5 1?5» "'i~f"`f'*‘ii~‘ Q f'!5"lGT:~.‘f!`*=§,fftif ,. _ -- , _ ‘ -Mamas; . gg , ~ - 5- - \-\.;~“ V .5 .1 _ 1. ,_ , 5 ‘ A .- . fl, . _ .1 t_;\y:;; _ ` 1 ». 11 :V vt \_ t \ ` ,f;¢.§;;4 f ` ~ - i ' ' '<3_,...---Y vi The direct-current brushes of that day were of copper and were vastly more delicate and liable to injury by spark- ing and Bashing than the carbon brushes which are now used. The alternators were simple mechanically. To appreciate this fact one has to go back to some treatise on dynamos published twenty years ago- and observe the multitude of forms of machines. Each system and each inventor seemed to require a pe- culiar form. Now there are few types, -l . A . 3 » . -. ~.,. . _- \¢_,,.=»¢=-""? .\ 7 ‘~~-_ »~ iiii" fP:l" f* .-~f1`5-or, ~ . _ ,.|.,»... .,_,t,,w\,a}|., £_,¢~=v- _|¢r~,'____,,..-*` I ,<.’_,,. ,_.._f,.. ,pig _ _,..¢_...< .`- . ,. ,M .___.;_, .~....¢ ,__ , _-as ~ »» rw 4-- ,_ .ya ¢ , , ‘JY 1 many parts are common to machines of different kinds and the nameplate in- stead of tl1e form of the machine must B52 ‘t "' *-'v “yi il 1' , 1, r , 4 ¥ I 1- t, 1. . - ».’f close-» vm -=~¥‘1l-"2-~ "lil *'ii'¢ ia t1"~a'!' »r~1;1.;»11,: ,g°ftt=~sf>1E~\~"5 ‘ 1 . 1 f;_'1;¢..‘ Y , .,‘~7,g,.1.,.,, 3 11 ' ~r ‘ | \\ ~ 1 ¢ I ` v( J I ‘ \ ¢ \ \ 1 \ ul ' l U J A: * f 3 e~ v l ` Ll A \ \ A g 1 | Q, 1 ` 1 `f‘ 1, l' ` `§ 1 f " ai t ( 1 .- it SL 1 U' / \ I tt 1 ' \ » l \ ' . ~ ae-r" ' '11 ,_ tt; -"' M ’ g f.:-.fv1'l&:1.;1' .,. KY, Fic, 1-1 500 1.1r;nr 1\1.1ruN/\r1Nc-cuxzizenr nynmwo wrm EXCITER-[888 in the development of the apparatus i11to commercial form. The previous year had been fertile in the study of alternating~current phenomena. Patent liti- gation l1as since sl1ow\1 that the development of mo- tion by currents differing in phase was shared by Tesla and Ferraris and Shallenberger and Stanley, and the priority of Tesla to tl1e motor and Shallen- berger to the meter were matters involving differ- ences of only a fe\v months, or even less, EARLY ALTERN ATORS In the sunnner of 1S88'the \Vestinghouse Com- pany was making three sizes of alternators. To these a fourth and smaller size was soon added. These machines \vere belt driven and operated nominally at Iooo volts and 16000 alternations per minute, corresponding to 133 cycles per second. Further particulars are as follows :-- No. o- 4oo lights, 8 poles, zooo r. p. m. No. 14 700 lights, ID poles, l6OD r. p. ni. No. 2-I 350 lights, I4 poles, 1 150 r. p. rn. No. 3-2 500 lights, 16 poles, 1050 r. p. m. The machines \vere driven by high-speed belts, in many cases from \\'estinghouse automatic engines. The noise and whir of the great belts in stations where there \vere a number of generators inspired a kind of awe in the visitor, which is entirely lacking in the l`l`lOllCl`ll bcltlcss power house. These alternat- ing-current dynamos had cast iron field magnets and rotating drum armatures, as shown in the accompany- ing illustrations. The construction was simple in general and in detail. It \vas simple electrically, as compared with the direct-current ‘dynamo witl1 its in- tricate armature winding and commutator. An argu- ment then presented was that brushes for collecting the current for a 1 500 light alternating-current dynamo have a \vidth of Zf{; inch, whereas, the brushes ”‘ be consulted to discover the maker. But nowhere is found the general simplicity and rigidity and the grace of form of this early alternator of Albert Schmid. The little ex- citer 11ear the alternator in Fig. I looks peculiar while the alternator does not. The first was of an ephem- eral type, while the latter is the prototype of many machines of today. It is a wise man who can devise the types which will continue. The bearings were sup- ported directly by parts of the great casting which formed the base; they were large and amply lubricated :;@;~ .w.'.'_‘¥i;.;`1r12’. fri:-rv.,~~r; --Q t ~;1~.-,*¢;1§f1 ”` ` ` f lb "‘"f” . ‘Zi/3; ‘ ,~'.-.'.$¢"»z.=?.~.,~»;f}<¢¥ "R -v - 1; ty it a=»t<, » ‘~ ~ ;;=§.'#` af: - ,-J-_;.."¢' ti* ‘Q '13' 1 tv, of iff.€<‘fi¥f?* f*<~§_¢§ 1 I »‘i§3?§. r lx. p .guhr ‘,?___?_§;§ A;"_ -"1 ‘\ - 1 ‘ i _ __ _ _ _ ._,, _ _., p _3M,_,?..,.¢3,f, Q* ---~ 1=“""\ lixtiff l » ,\-11 '\~‘ .~~'E;£’ ‘ z ,¢ '_ V ‘ :n~._j_‘__ 3 3, f§"" 1.

THE ELECTRIC JOURNAL 123 with considerable success. However, a failure in an attempt to parallel, in those days, usually meant the destruction of the apparatus. '1`hose old time surface- wound alternators usually had very low self-induction, s vv\‘\ ng. ` W' .,»¢ ‘J Q " Q :E °- ¢ '~\~` /-; , _ . H.; 1, f ze A l i _ \’ »\ ». _ _,L I / / ~...,»;< .- .,. / _f ,of 1 . ..»- `/ ,V _ ' / /,f -' _;“-_tztzgtgj _ V _ _ ,__,_ ' _,. _ ~ ‘ ffl! ° . ., --EFL" ~ ."_ "~'<,.,;'~~.at41% .\= 2 ” ~1-"1 _ ' _ ‘t ,4¢,.~-¢.~s~=' i¢w t‘?3= I ~'a_ _ _ -- - _ tt qggewffi ,v-;~_- - . ,_ ,.~ I 3 “via _ . 2 , .sat ~ _ , » _g-'Y 4 . 5/ +7 _,,. . _ _ ~ - , ' ‘- ` 1Qi$~£ _ -1 . _, i /'/_~_» .1 l= ' ’ _a ' “ §fl'§’{.~ _ _ -;'-" ’ 'gl - .1§_ fr" ‘\;_ " . f __./‘7§ 'A »‘ gf If _. ,,-,_ - ` /~_,_¢_ 4 ,y ,gr _` _ V; ` ‘ U( /if /,, ap.,-.ff _ _ , /f .~ V, / f ’.r>~, 4 , v nc. I§~7§ 1c.v.A., 'ramen-rnass, 60 cvcce, 2 300 voL1‘, 150 man. norxrmc new ENGINE rvre .xtrcnn/non so that, in case of sudden short-circuit, an enormous current could flow, sufficient usually to strip the arm- ature winding from the core, by bursting the bands, or otherwise. A failure in an attempt to parallel two machines was practically equivalent to a short-circuit, and this usually meant destruction of the apparatus. However, if once paralleled successfully, the machines usually did not act badly. One favorable condition, not then appreciated,,was that all these early machines were belt-driven. It may be said, however, that in those days parallel operation, \vhile considered possi- ble, \vas also considered more or less risky. In the period immediately following the surface-wound al- ternator, parallel operation was very much the excep- tion, rather than the rule and, when engine-type alter- nators came into use, paralleling was considered for several years as very questionable. At this time the situation \V3S as follows:-Belted alternators could be paralleled in many cases. Direct-coupled alternators, if flexibly driven, could be paralleled almost as well as belted machines, \vhile direct-coupled or engine type generators, without flexible coupling or drive, could not be relied on to parallel without hunting. It tlms be- came recognized that some flexibility between the gen- erator and its prime mover \vas an important adjunct to parallel operation. This-led to the consideration that the engine might be back of the difficulty in many instances, and it was then assumed that inequalities in the regular rotation resulting from insufficient Hy- wheel or from hunting governors, tended to cause hunting in the generators. Investigation showed that such conditions did tend to produce hunting, but that the magnetic conditions in the machine itself would oftentimes maintain, or even accentuate, the hunting. Obviously, therefore, the trouble \vas both in the prime mover and in the generator. It was noted further that if the angular Hnctuations in the driving po\ver were relatively small, hunting usually would be very small, or would not be apparent at all. It was further recognized that, with belt or flexible drive, which tended to smooth out the speed fluctuations due to the prime mover, the hunting tendency tended to dis- appear. Attention was then turned to\vard improve- ment of the prime movers, especially in engine-type machines, in order to reduce fluctuations in angular velocity by means of heavy Flywheels, and by means of dampers of some sort, such as dashpots, on the gov- erning mechanism of the engine. Much improvement was accomplished in this \vay. The Introduction of Damper:-During this period many attempts were made to lessen the tendency of the alternator to maintain hunting. Investigation magnetic Flux in the sho\ved that, during hunting, the field poles shifted back and forth across the pole faces in time with the hunting, \vhile occur when there was no hunting. the theory that a lo\v resistance face , or imbedded in the poles, would prevent or op- pose this flux shift, and thus assist in overcoming hunting. However, about this time, rotary converters \vere coming into use, and it \vas found that, in such machines, hunting was usually more severe than in alternators, so that, in this country, the first true ap- plication of damping windings or devices to stop hunt- ing were applied on rotary converters. It \vas also noted at this time that solid pole generators and rotary converters did not hunt to the same extent as did lami- such action did not This at once led to winding on the pole FIG. 16--VARIQUS FDRMS OF DAMPERS nated pole machines, and it \vas correctly assumed that the solid pole faces gave an effect similar to that of lo\v resistance damping windings. However, as it was desirable to use laminated pole tips, copper dampers on the poles gradually came into use. Some of these early dampers were very crude in form and type corn- pared with present constructions. However, imperfec- tions in the construction of the dampers were balanced to some extent by the large section of copper used

THE ELECTRIC JOURNAL "5 phase was used, giving but two slots per pole for t\vo- phase and three slots per pole for three-phase. Such windings required special shaping of the field pole tips in order to approximate even roughly a smooth wave form of the sine shape. Later practice, however, has tended toward the equivalent of at least two slots per phase per pole, in order to obtain better results. Sometimes the desired result is obtained by the use of one extra idle or "hunting" tooth per phase. In the early days of parallel operation of engine type alternators which, as described before, repre- sented the most difficult conditions, great stress was laid upon the question of wave form in some of the discussions of parallel operzhion, and particularly, in the operation of rotary converters without hunting. Gradually, however, this question disappeared and it became recognized that all the cases of hunting en- countered could be explained in some other way than by the e.m.f. \V3V¢ forms, and it is now generally ac- cepted that about the only effect on parallel operation due to wave form lies in possible circulating currents of higher frequency than the fundamental. At the present time, a very close approximation to the sine shaped wave is considered preferable for general purposes, especially in transformation and transmission work. There have been some instances of telephone disturbances due to wave form but, as a rule, some local peculiarities of the distribution cir- cuits have been involved in this trouble, for, in other cases, similar or even \vorse shaped \vaves have given absolutely no telephone disturbances. REGULATION AND COMPOUNDING Something should be said on the subject of regu- lation of alternators, for this is a very important char- acteristic, and has had considerable influence on types and designs. The old surface-wound altemators had extremely good regulating characteristics due to their low armature self-induction and low armature reac- tion consequent upon tlieir large air-gaps. The writer does not know what value the current rose to, on steady short-circuit, compared with the normal rated current, but it \vas probably four or five times full load. The current rush on short-circuit \vas probably nve times as great as the steady value. It is not to be wondered at that such armatures not infrequently wrecked themselves in case of a dead short-circuit. In the later toothed armature types, the armature self- induction and reaction on the field were very much larger, proportionately, than in the surface-wound machines. This, however, spoiled the regulation and some method of compounding was used, as already described. This compounding \V35 common practice until larger capacity machines, especially the engine type, came into use. Even some of these latter were compounded by commutating the armature current_ (either directly or from a series transformer) and compounding 'the exciter field by means of the com- mutated current. A few of the smaller size alter- nators were both self-excited and compounded by commutating derived alternating-current circuits from the armature. This, however, was found to be very delicate, as the excitation and compounding were greatly affected by changes in the power-factor of the load, and by changes in speed. One early attempt \vas made to compound single- phase alteruators to correct for power-factor. In this case the commutated armature current was sent through the series or compound winding of the ex- citer. The brushes on the alternating-current com- mutator were so set that at too percent power-factor they were commutating about the middle of each voltage wave. In consequence, the current delivered to the brushes was not a true direct current but con- sisted of a double number of half waves, half of which were inverted, and the direct-current component of this conuuutated current \vas small and had but little COITI- pounding effec-t. Ilowever, with change in po\vcr- factor of the load, tl\e phase of the current shifted, so that at' some reduced power-factor, commutation oc- curred at the zero point of the current \vaves and the resultant current was all effective for magnetizing the exciter field. The total commutated voltage was very low and the conimutator bars were shunted by a re- sistance so that there was no bad sparking, even when commutating at the middle of the current ware. This method did actually compound fairly \vell for change in power-factor, but the field for such method proved to be very limited, for compounding of alternators fell into disuse shortly after this. The usual method of compounding on the early alternators \vas simple series current compounding, just as in direct-current apparatus. \\'here the com- mutated current was supplied directly to the field compound winding, voltages of about 30 to 60 volts were most common at rated full load. With much higher than 60 volts, there was a liability of short- circuiting the compounding by arcing between bars on the commutator. There was also a liability of arcing or flashing \vhen the phase of the current shifted due to change in power-factor. \’Vhen polyphase rotating armatures came into use, similar methods of compounding were resorted to. However, the secondary current was a resultant of the two, or three primary currents, for each of the pri- mary phases was carried around ,the compensating transformer (or spokes of the armature) and the sec- ondary winding carnied a current in phase with the resultant of the primary ampere-turns. In the case of three-phase windings, the direction of one 'lead was reversed around the compensating transformer. Some curious conditions arosefrom the phase relations of the secondary current \vhen parallel operation \V3S practiced. It \vas necessary, when parallelling the main winding, to parallel also the compound winding. As the compounding current from each machine pul- sated from zero to maximum value in each alterna- tion, it was necessary to so parallel the terminals that all the commutated currents had zero value at the

THE ELECTRIC JOURNAL 223 these rotors of discs turned out of very thick steel plates, somewhat like the ea1‘4ly 400 kw machines al- ready described. Parallel slots were used as in the smaller four-pole machines. This construction proved to be feasible but \vas very expensive, and shortly after this large cast steel discs were used, two discs side by side being used to form one rotor. This con- struction was satisfactory, and was used for many years. Shortly after turbo-generators came into general use, there \vas considerable complaint regarding the noise due to windage. All these machines were equipped with some form of vcntilating device, which fomied either part of the normal construction of the rotor or consisted of some special blowing device at the ends of the rotor. Both the high speed and the large quantity of cooling air required, tended to make a noise which was very objectionable. A series of 'Wa /n 1 A 1 FIG. 26_TWC|-POLE FIELD OF THE BOLTED ON CONSTRUCTION experiments with covers over various parts of the ma- chines, showed that, by completely enclosing the two ends of the machine and by enclosing the field frame except at the top and bottom, (in a horizontal ma- chine) the windage noise could be so deadened as to be practically unobjectionable. However, the tests also showed that artificial ventilation was necessary under this condition. This very quickly led to the practice of enclosing and artificially cooling turbo- generators,'which practice has been maintained to this day. The first Westinghouse enclosed machines were built about IQ03. The use of artiificial cooling marked a great step in advance in turbo-generator work, for the results indicated that, by supplying a sufficient quantity of air and properly distributing it through the machine, very marked increase in capacity was possible, and a point was soon reached where the possible capacities were beyond the mechanical limitations of the con- struction. This led to radical modifications in the type of rotor, \vith a view to taking advantage of the increased capacity. Apparently all manufacturers did more or less development work along such lines. in the Westinghouse constructions, the use of a through shaft was found to he one of the serious limitations, and this led to types of rotors without any through shaft. In the two-pole machines, this \V3S particularly important, and the problem was especially difficult \Vlll\ the parallel~slot construction, provided ample space \V3S allowed for the field winding. The old through shaft two-pole construction lost considerable winding space, due to the shaft space, as shown before in Fig. 24. Attempts to construct such a machine with the 'shaft forming part of the core, resulted in still less efficient use of the possible winding space. It was obvious that if the \vhole possible winding space \vere taken up with slots, then the capacity of the field winding \vould be greatly increased. In conse- quencc, a rotor construction, such as shown in Fig. 26, \vas designed and constructed. In this, bronze emi supports or "heads" \vere bolted to each end of the field core, and the shaft proper was attached to these bronze heads. Bronze, or a similar non-magnetic ma- terial, was ncccssary to prevent magnetic sl\ort-cir- cuiting of the field flux. This design \vas constructed and tested on a I 000 k.v.a., 3 600 revolution machine, and then was built successively for 1 500, zooo, 3000. 4000 and 5000 k.v.a. machines, all at 3600 r.p.m. The same construction was also applied 'to two-pole machines of 25 cycles, up to 12000 k.v.a. capacities. This construction of rotor has given an extremely good account of itself. However, it proved to be cx- pensive on small capacity machines, as the bronze heads formed an undue proportion of the cost of ma- terial. For higher capacities of 3 600 r.p.m. machines, increase in capacity is obtained largely by increasing the length of the rotor core, and thus #the bronze heads form a relatively lower percentage, and the construc- tion becomes more reasonable in cost. From the preceding, it may be seen that only two types of turbo-generators have been used very exten- sively, namely, the parallel-slot type and the radial slot. Each of these types has some very pronounced advantages. The principal advantage of the parallel- slot type is in the arrangement and support of the field coils. Each coil can be wound directly in place, with the conductor under tension, and the finished winding is completely encased, and is thoroughly pro- tected against dirt, movement of the conductors, etc. Against this, the radial slot machine allows more room for copper, and is magnetically more economical in material. However, the field windings are more diffi- cult to apply and must be supported at the ends by auxiliary means, such as separate external steel rings. The enormous increase in output of turbo-genera- tors, within very recent years, has made the electric

Sn THE ELECTRIC JOURNAL ing engine type machines are probably in as good con- dition now as when hrst installed, and are being re- placed simply because they occupy too much space in proportion to their output. The rotating held alternator of the early days was not radically different from the rotating field alter- - r .5 - i` | ` if '"'» li " » 74 ` '_ _ +1 ` 1 ” if ` " Q - \ , '<" -_ 4. \, 4 r A r; ~¢ ,.,\_ .__ ~ _ ~ c __,~> 5 I -> ` `i\ - ___ ,_ , 15,30 . 1" \ , . _ _.__ I I' ' _. , 5- t V’ 5" " \ I Q _i ‘gy ht. I " “ u l vii . A rr? ,Y-=~""\`t FIG. 9-SHOP VIEW OF 5000 HORSE-POWER Two-PHASE NIAGARA ALTERNATOR nator of today, the principal differences being in the type of :irmature windings, methods of ventilation, etc. FIELD FUNSTRIICTION In the types of held windings ‘there has been but little change, ln many of the old stationary held ina- chines of large capacity, the field windings consisted of strap wound on edge, one layer deep. For smaller machines, either square or round wire was commonly used In the later rotating tield machines, similar constructions are used. In the construction of the held itself, there have been some variations and modi- fications. ln many of the older machines the poles were laminated as at present. The method of attach- ing the poles varied in different constructions. In many of the earlier \Vestinghouse rotating fields the laminations were punched with two or more poles in one piece, the poles having no overhanging tips, and the Held coils being held in place by metal wedges be- tween pole tips, htted into notches or grooves at the pole tips. each pole being attached to the field ring or yoke by means of bolts or dove-tails, This latter con- struction possesses numerous advantages, in that cheap dies can be used, and the same pole punehings can be used for a number of different designs, in which either the diameter or the number of poles is varied. WATER WHEEL TYPE GENERATORS NVitl1 the advent of the turbo-generator on a large scale, the engine type rotating field alternator almost disappeared from the manufacturing field, except in the smaller size units. However, during this period there has been a gradual development in the use of water powers, and water-wheel driven generators have come into much greater prominence in the past few years. In this line of development, speeds and ca- pacities, unheard of in the earlier days, have become accepted practice with the development of both high- head and low-head \vater powers. In the former the tendency has been toward very high speeds for a given capacity such as the I7 ooo k.v.a., 375 r.p.m., Westing- house machines, built for the Pacific Light & Power Company, and the 10000 k.v.a., 600 r.p.m., Westing- house generators, built for the Sao Paulo plant in Brazil. Typical examples of low-head, slow-speed practice are found in the 60 cycle, 75 r.p.m., 96 pole, 2700 k.v.a. Westinghouse generators for the Stevens Creek development, and the 25 cycle, ~58 r.p.m., 52 pole, 9000 k.v.a. General Electric generators for the Keokuk plant. The former are abnormal in the very large number of poles required for moderate output, \vhile the latter are abnormal in the very low speed. Both of the above machines are of the vertical type, and are examples of a very pronounced tendency to- \vard vertical machines, which has been apparent in the later water wheel practice. W. _cn . -\_ _ _ , , mn ruv vlulhlt I 1| fm l muluilulllliIlllilstiiftl Ilnlllllll l llliliilliinllitnlrillil *ll l Illllllll 3,5 .. . . _rt .. ........{....L...... M fir" _,asf ;"“~_;:» f tr ~ ‘ . 'e ~ = 'r tr rw r , .` 'f Illf ` 3.4; »=~frInuimmlillltlilliliutyfrffllllllftte IQ'QA3nmmm||l|||||t|||||||m;#-¥§;25;!;,¢:,. at ig ft ji._!i{;§§\||i|1|azi¢|||ia|=i:ifti",frm 1, W \_ ; 5 " tw vm My Pg W, llllllllllllll pg or ,,,, ,gi ' " "~~ *‘ . #SE (V: ,_ ppl...t..,»........~_~i _ .57- f\fA '--.-r.,..............,..-»- t ~" ' ‘ ., "- 143] 1,5 ~ "1 » 3 !llUll!l§llt!l 1'l1¢ l r~§§l§:.., ' .. " ` 4 - » with., »- -:f$f;‘ ¢= t ""` ` ""“‘f .. , '_,__.__' ""f‘C'l'ii;; r FIG. I0-ST/\TOR OR ARMATURE DF NIAGARA ALTERNATOR On account of the high speeds of some of the modern stronger spiders have come into general use. Even in moderate speed units the usual high runaway over- speed of loo percent has necessitated the use of very substantial spiders. (Tu be continued) rotating field alternaitors, mechanically

THE ELECTRIC JOURNAL 77 of the induction motor problem for, at the time it be- came most pronounced, there was no true induction motor problem. It was becoming recognized that 125 to 133 cycles per second was too high for certain classes of work and for engine type generators, and that, in general, a very considerably lo\ver frequency must eventually be adopted. A great many lower frequencies were tried by the different manufacturing companies, ranging from 50 to 85 cycles. However, 60 cycles seemed -to have the preference at the time polyphase alternators began to come in. The early polyphase generators were mostly of the rotating armature type, and usually with a fairly large number of slots per pole. Gne notable exception was the “monocycle" machine which usually had only two slots per pole, one large slot for the main armature winding, and one smaller slot for the so-called “teaser” \vinding. Also, the early two-phase alternators of the “in-duct0r” type, built by the Stanley-Kelly Company, frequently had only two slots per pole. However, it may be said tha-t, from 1893 to about 1898, the great majority of the American built alternators were of the rotating armature type with distributed armature \vindings. The principal exceptions were the Stanley inductor type of machines and a few special “rotating fieldf' machines, as distinguished from the inductor type. The rotating armature machines were usually of 1 100 or 2200 volts, although a few of considerably higher voltage were constructed. A few cases may be cited where special constructions were used. For instance, the principal lighting plant at the Chicago \’Vorld's Fair in 1893, consisted of a large number of \\’estinghouse “t\vin” type generators. Each unit had t\VO single-phase, standard toothed type armatures side by side on the same shaft. The teeth of the two armatures were staggered 90 electrical degrees with respect to each other, so that the two together could deliver currents having 90 degrees relation to each other. The object of 'this construction was to obtain polyphase current with standard single-phase types of machines without any radically new development. This type of unit did not persist and, in fact, \vas simply an expedient for this particular occasion. TIIE FIRST NIAGARA GENERATORS Also, in 1892 and 1893, the first large Niagara electrical development was worked out. The advisory engineers of this plant proposed 5ooo horse-power generators, having stationary internal armatures and rotating exfternal fields to obtain large flywheel capac- ity. In fact, the construction was not unlike the usual rotating armature machine of that period, as far as general appearance of the armature and field cores and windings were concerned. However, the method of supporting and rotating the heavy external field at a speed which, at that time, was considered excessively high, required an "umbrella" type of field support, which gave these machines a distinctive appearance. This type of construction did not persist, although these early machines are still in operation. A further distinctive feature in these first Niagara machines \vas in .the frequency employed. A speed of 250 revolutions per minute was decided upon. The engineers of the power company proposed eight pole machines, giving 2000 alternations per minute or 16 2/3 cycles per second. The \Vestinghouse Com- pany proposed, as an alternative, 16 poles, giving 33 I/3 cycles, the advantages claimed for this fre- quency being that it \vas better suited for motors and rotary converters, \vhich were then promising to be- come of importance. One advantage claimed for the 16 2/3 cycle machine was that it would permit the use of commutator type alternating-current motors. After much discussion, and weighing and balancing of all the various arguments for and against these t\vo frequencies, it was finally decided to use I2 poles, giving 3 ooo alternations per minute, or 25 cycle poly- phase currcnt and, as far as the writer kno\vs, this \vas the origin of the present 25 cycle standard. Considering what a radical departureirom or- dinary construction was madc in =these first Niagara generators, it is selt'-evident that many curious and interesting conditions developed during their design, construction and tests. As far as the \vriter knows, these were the first large alternators which were de- liberately short-circuited at their terminals when run- ning at full speed and at normal field charge. There were no instruments available to measure the first current rush, but it was obvious that this current was far greater than the steady shont-circuit current of the machine undef similar field charge, for there were ample evidences of a terrible shock at the moment of short-circuit. It was suspected at that time that the Erst rush of current \vas only limited by the armature impedance, and not by the so-called synchronous im- pedance \vhich fixes the value of the steady short-- circuit current. This also \vas the earliest machine of which the \vriter predetermined the field form and \vave form by analysis of the flux distribution, Later, when mak- ing shop tests on one of these machines, the e.m.f. wave form was measured directly by rotating the field at normal field char,ge at such an extremely low speed that a voltmeter connected across the armature ter- minals sh0\ved such gradual variations .in e.m.f. that readings taken at regular intervals could be plotted to form the voltage \vave. Slow rotation was obtained by means of a steel cable wrapped about the outside of the external field and with one end of the cable alt- tached to a small diameter spindle around which it was wrapped at a very slow rate. This was a very crude method, but ‘the wave form thus abtained checked very accurately \vith tests made some years later. Also, the early Niagara machines embodied one of -the first distinct attempts to ventilate aliternators artificially. Early belted machines had had small ven-