Electrical Oscillators

Tuesday, July 1, 1919
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July, l9|9 ELECTRICAL EXPERIMENTER 229 Electrical ®scilll@t© s ENV fields have heen opened up the exploration of which has proved as fruitful as that of high frequency currents. Their singular properties and the spectacular character of the phenomena they presented immediately commanded universal attention. Scientific :, ~ z f ,wtf If If , » ‘H ‘t- § t t l - = 9 ,i I ut, 1 l tw: t. 1, ,uf t ’° Q ,. 4 . F. A , t ‘1 < ll 0 -._ " 1 , t Q* . g. y tt FI . 13-Tesla omttswr with Msqnnteatty Somrottea, seated Mercury interrupt"-. men became interesterl in their investiga- tion, engineers were attracted hy their com- mercial possibilities, and physicians recog- nized in them a long-sought means for ef- fective treatment of bodily ills, Since the publ-ication of my lirst researches in 1B9l, hundreds of volumes have been written on the subject and many invaluable results ob- tained thru the medium of this new agency. Yet, the art is only in its infancy and the future has i\\cou\|mr;|hly bigger things in store. Front the very beginning I felt the neces- sity of producing efficient apparatus to meet a rapidly growing demand and during the eight years succeeding my original an- nouncements I developed not less than fifty types of these transformers or electrical oscillators, each complete in every detail and refined to such a degree that I could not materially improve any one of them today. llad I been guided hy practical considerations I might have huilt up an nn~ t' ‘T /Y, L_, 1 1 ;~' Y V \0 ry/ ‘ t /tai, C'L A tt, (2 _ ' R ,1 ' » 'V i. ‘t ll ` O ' V " /i>,.t - Y - _/ . .t ,.-» . -- _ ~- . ’ 3 4, Fi'--< ;r; ` 1 _ / / , ./ " X . _-t » ~~ W ‘t ]r_Li~l&¥'n`|V‘7l;" . Fltjl t, _ _. ; -tt' Flg. 14-Electrlcal Oscillator, Illus- trated In Flg. 13, Showing Detalls and Circuit Connections. By NHKULA 'll`lESlLA MR. TESL/1 makes a very important contribution to the electrical arts with this article. The pioneer of all high fre- quency apparatus rlivulgas much that is new anal start- ling in these pages. Few peo- ple realize the enormous value of Mr. 'l`esla’s macltinr-s anzl the many aligaront irn- portant uses to which they can be applied in our every- day lives. New anrl startling uses are being foznul every year _for these machines. It is characteristic of lllr. Tesla that lm ltas ¢lt~m»In/wt/ aml actually lrni/I an astnnnfl- ing variation of these ma- chines, and we regret that we can publish only a 'very few of the more important mmlels. lllost of the Tesla coils shown have never been pull- lisht before. -EDITOR. mense and profitable husiness, incidentally rendering important services to the \vorld. Hut the force of circumstances and the ever enlarging vista of ervatt‘r achieve- ments turned my efforts in other direc- tions. /\nd so it cutiies that iustruutenls will shortly be placed on the market \vhich, oddly enough, were perfected twenty years ago! These oscillators are expressly intended to operate ott direct and alternating light- ing circuits and to generate tlanipt-tl and uudamped oscillations or currents of any frequency, volume and tension \\‘i1hin thc widest limits. They are cou\pact_ >eli-con- tained, require no care for long pt-riods of time and will he found very convenient and useful for various purposes as, uireless telegraphy and telephony; conversion of electrical energy; formation ol' chemical compounds thru fusion and cotuhiua- tion; synthesis of gases; n\auuf:u'ltu'e of ozone; lighting; welding; municipal, hos- pital, and domestic sanitation and steriliza- tion, and numerous other ap|tlicatit>n> in scicntilic lalrorzttories and iu;1-salsa A”'\'7 l ..,,,.,.,.,, ..,. l EZ" ' , ,\\ / fs fy! /// I f R If I l, f \ L f _./ K s_ 6 ""'IS Flg, 15-Electrlcal Osclllatnr, Illus- trated ln Flg. 15, Showlng Detalls Df Motut' and Break Mechanism.

ELECTRICAL EXPERIMENTER nally I employed platinum and iridium tips but later replaced them hy some of meteorite and finally of tungsten. The last have given the best satisfaction, permitting working for hours and days without 'in- terruption. Fig. 2 illustrates a small nsrillator fle- signetl fur een-l:\in sperilic uses. 'l`l\e under- lying idea was to attain great activities dur- ing minute intervals of time each succeeded hy a comparatively long period of inaction. With this object a large self-induction and a qu-iek-acting break were employed owing to which arrangement the condenser was charged to a very high potential. Sudden secondary currents and sparks of great vol- ume were thus obtained, eminently suit- able for welding thin wires, flashing lamp filaments, igniting explosive mixtures and kindred applications. The instrument was also adapted for battery use and 'in this form was a ver effective igniter for gas engines on whiclii a patent bearing number 609,250 was granted to me August 16, 1898. Fig. 3 represents a large oscillator of the first class intended for wireless experi- inelils, p|'uilutrtiu\\ of ltiintgen rays and scientific research i|\ general. lt comprises a box containing two coudensers of the same capacity on which are supported the charging coil and transformer. The auto- matic circnit controller, hand switch and connecting posts are mounted on the front plate of the inductance spool as is also one of the Contact springs. The condenser box is equipt with three terminals, the two external ones serving merely for connection while the middle one carries a contact bar with a screw for regulating tl\e interval during which the circuit is closed. The vi- brating spring itself, the sole function of which is to cause periodic interruptions, can be adjusted in its strength as well as distance from the iron core in the center of the charging coil by four screws visible on the top plate so that any desired condi- tions of mechanical control might be se- cured. The primary coil of the transformer is of copper sheet and taps are made at suitable points for the purpose of varying. at will, the number of turns, As in Fig. 1 the inductance coil is wound in two sec- tions to adapt the instrument both to 110 and 220 volt circuits and several second- aries were provided to suit the various wave lengths of the primary. The output was approximately SU() watt with dainpetl waves of aliont 5(),tJU(t cycles per second. For short periods of time undamped oscil- lations were produced in screwing the vi- brating spring tight against the iron core and separating the contacts -by the adjust- ing scre\v which also fvrrfoniwd the func- lizm nf ri key. With tiis oscillator I made a number of important observations and it was one of the machines exhibited at a lecture before the New York Academy of Sciences in 1897. Fig. 4 is a photograph of a type of trans- former in every respect similar to the one illustrated in the May, 1919, issue of the EI.nc'rinc/ti. Exrmui\mN'rEn to which refer- ence has already been made. It contains the identical essential parts, cl-isposed in like manner, but was specially designed for use on supply circuits of higher tension, from 220 to S00 volts or more. The usual ad- justments are made in setting the Contact spring and shifting the iron core within the inductance coil up and down by means of two screws. ln order to prevent injury thru a short-circuit, fuses are inserted in the lines. The instrument was photo- graphed in action, generating undamped oscillations from a 220 volt lighting circuit. Fig. 5 shows a later form of transformer principally intended to replace Rhumkorf coils. ‘ln this instance a primary 'is em- ployed, having :i much greater nnmher of turns and the secondary is closely linked \vith the`same. The currents developed in the latter, having a tension of from 10,000 to 30,t)0tl volts, are used to charge con- (Cnnlinnrd nn page 276) july, 1919

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July, l9l9 ELECTRICAL EXPERIMENTER Electrical Oscillators By Nikola Tesla (Continued from page 229) Broadly, the instruments can be divided into two classes: one in which the circuit controller comprises solid contacts, and the other in which the make and break is ef- fected by mercury. Figures 1 to 8, inclu- sive, belong to the first, and the remaining ones to the second class. The former are capable of an appreciably higher efhciency on account of the fact that the losses in- volved in the make and break are reduced to the minimun\ and the resistance com- ponent of the damping factor is very small. The latter are preferable for purposes re- quiring larger output and a great number of breaks per second. The operation of the motor and circuit controller of course consumes a certain amount of energy which, however, is the less significant the larger the capacity of the machine. In Fig. 1 is shown one of the earliest forms of oscillator constructed for experi- mental purposes. The condenser 'is con- tained iu a square box of mahogany upon which is ulouutetl the self-induction or charging coil wound, as will be noted, in two sections connected in multiple or series according to whether the tension of the supply circuit is 110 or 220 volts. From the box protrude four brass columns carrying a plate with the spring contacts and ad|ust- ing screws as well as two massive terminals for the reception of the primary of the transformer. Two of the columns serve as condenser connections while the other pair is employed to join the binding posts of the switch in front to the self-mduct- ance and condenser. The primary coil con- sists of a few turns of copper ribbon to the ends of which are soldered short rods fit- ting into the terminals referred to. The secondary is made in two parts, wound in a manner to reduce as much as possible the distributed capacity and at the same time enable the coil to withstand a very high pressure between its terminals at the cen- ter, which are connected to binding posts on two rubber columns projecting from the primary. The circuit connections may be slightly varied but ordinarily they are as diagrammatically illustrated in the. ELEC- TRICAL Exrcalmcurea for May on page 89, relating to my oscillation transformer photograph of which appeared on page 16 of the same number. The operation is as follows: When the switch is thrown on, the current from the supply circuit rushes thru the self-induction coil, magnetizing the iron core within and separating the con- tacts of the controller. The high tension induced current then charges the condenser and upon closure of the contacts the ac- cumulated energy is released thru the primary, giving rise to a long series of os- cillations which excite the tuned secondary circuit. This device has proved highly serviceable in carrying on laboratory experiments of all kinds. For instance, in studying phe- nomena of impedance, the transformer was removed and a bent copper bar inserted in the terminals. The latter was often re- placed by a large circular loop to exhibit inductive ellects at a distance or to excite resultant circuits usctl in various investiga~ tions and measurements. A transformer suitable for any desired performance could be readily improvised and attached to the terminals and in this \vay much-time and labor was saved. Contrary to what might be naturally expected, little trouble was ex- perienced with the contacts, altho the cur- rents thru them were heavy, namely, proper conditions of resonance existing, the great flow occurs only when the circuit is closed nntl no destructive arcs can develop. Origi-

276 Eli dcusers and operate nu independent high frequency coil as customary. The contro|~ ling uicchanism is ol smucwlml xlillcrcut cmistriirtiuii but llu: core :uul cuulnvt spring :irc |»ull| :uljustzihlc :is Iwiurc. Fig. 6 is a small instrument of this type, particularly intended for oznne production or sterilization. lt is remarkably ellicieut for its size and can be connected either to a 110 or 220 volt circuit, direct or alter- nating, preferably the former. lu Fig. 7 is shown a photograph of a v, _ 4 ' _ _ »\. ., I .. ,» , v 4 _ - _ » _ H Flq. 17. Tesla Transformer Wllh Adjustable Mercury Controller. larger transformer of this kind. The con- struction and disposixiou of thc parts is as hcforc hut there :ire two condciiscrs in the box, one of which is connected in (he cir- cuit as in the previous cases, while the other is in shunt to the primary coil. In this manner currents of great volume are produced in the latter and l|\e secondary effects arc accordingly maguilied. The in- troduction of au additional tuned circuit secures also other advantages hut the :id- justmculs :irc rcmlcrcrl inure dillicull and for this reason it is dcsirzilvle to use such an inslrumcut in the production of currents uf a definite and uxlclxanging frequency. Fig, 8 illustrates a transformer with rotary break. There are two cuudeusers of the same cnpacily iu the box which can he councctml iu series or u1ul(~iple. The charging iuductauces are in the form of two long spools upon which are supported the secondary terminals. A small direct current motor, the speed of which can he varied within wide limits. is employed to drive a specially constructed make and break. In other features the oscillator -is like the one illustrated in Fig. 3 and its operation will be readily unrlersloud from the foregoing. This transformer was used in my wireless experiments and frequently also for lighting the laboratory hy my vac- uum tubes and was likewise cxhihiieil at my lecture before the New York Academy of Sciences above mentioned. Coming now to machines of the second class, Fig, 9 shows an oscillatory trans- former comprising :1 courleuscr :md charg- ing iuducl:\ucc cucloscd ill a lwox, :A trnus- former and a mercury circuit controller, the latter being of a construction described for the first time 'in my patent No. 609,251 of August 16, 1398, It consists of n nmlnr driven hulluw pulley cmimiuiug :\ small qu:\u|ily of mercury which is thrown out- wardly against the walls of the vessel by ELECTRICAL EXPERIMENTER july. |919 ectricall ©§cci}l]1ax&ors By Nikola Tesla (Crmlinurd from /vnge 260) ccutrifugul force and eulrains a contact wheel which pcrinrliczxlly closes nud opens thc cunrlcusc-r circuit. Hy menus uf adjust- ing <<~\~-ws :||~¢»\'\- uw |»ul|¢~\-, uw rl--|»||» 1-I inuiiucrsinm nl the vuucs :unl cu|\sc<|uc|\lly, also, the duration of each contact can he varied at desire and thus (he inleusity of the effects and their character controlled. This form of break has given lhoro satis- faction, working continuously with currents of from Z0 lo 25 ampcres. The uumbcr of interruptions is usually from 500 to 1,000 per second but higher frequencies are practicable. The space occiipicd is about 10" x 8” x 10" and the output approximate- ly M KW. In thc transformer just described the break is exposed to the atmosphere and a slow oxidation nf the mercury takes place. This disadmiitagc is overcome in the iu~ strument shown in Fig. 10, which consists of :\ perforated metal box containing the mmlm-usvr mul rlmrgixig imluclzilirc :md can-ryiug nn |l\c mp :\ motor driving the break, auml a transformer. The mercury break is of in kind to be described and operates on the principle of a jc! which establishes, iutcrniiltcntly, contact with a rotating wlwel in the interior of thc pulley. The stationary parts are supported in the vessel ou a bar passing thru the long hollow shaft of the motor and a mercury seal is employed to eflect hermetic closure of the chamber enclosing the circuit con- troller, The current is lcd into the iutcrior of the pulley thru two sliding rings on the top which arc in series with the con- dvuscr and |>ri\u:\ry_ The exclusion of the oxygen is :i decided improvement, the llc- terioration of thc metal :ind attendant trouble being eliminated and perfect work- ing conditions continuously maintained. Fig. ll is a photograph of a similar oscillator with hcriuchcally inclosed mer- cury l:rcak_ lu this machine thc stationary parts of thc interruptcr in the interior of the pulley were supported on a tube thru which was led an insulated wire connect- ing to one terminal of thc break \vhile the other was iu contact with \he vessel. The sliding rings were, iu this manner, avoided and the construction simplified. The in- strument was designed for oscillations of luwvr tc-mimi :ind fr<~<|urucy rr-quiring pri- mary currculs uf comparatively smaller zuupcrage and was used to excite other resonant circuits. Fig. 12 shows an improved form of oscil- lator of the kind described in Fig. 10, in \vl\ich the supporting bar thru the hol- lo\v motor shaft was done away with, the device pumping the mercury being kept in position by gravity, as will be more fully explained with reference to another figure. Both the capacity of the condenser and primary turns were made variable with the view of producing oscillations of several frequencies. Fig. 13 is a photographic view of another form of oscillatory transformer with her- metically scnled mercury iulerrupter, and Fig. 14 diagrams showing the circuit con~ nectious and arrangement of paris repro- duced from my atcnt, No, 609.245, of August 16, 1898, cliescribing this particular device. The condenser. inductance, trans- former and circuit controller are disposed as before, but the latter is of different con- struction. which will he clear from an inspection of Fig. 14. The hollow pulley a is secured to :\ shaft c which is mounted in a vertical bearing passing thru the stationary liclrl magnet d of the motor. In the interior of lhc vessel is sup ortcrl, on lriulismlrss lu':\riugs, :\ luuly l| nijlilsigliulic u\:itvri:il which is surruuiulccl by n dome b in the ccnlcr of a laminated iron ring, with pole pieces aa wound with energizing coils [». The ring is supported on four columns and, when maguctized, keeps the body ll in position \vhile the pulley is rotated. 'l`h<~ l:\l|cr is of stu-I, Inu Ihr dome is |»rcIcr:\hly made of German silver Iiurul black by acid or nickeled. The body lx carries a short tube k bent. as indicated, to catch the fluid as it is whirled arouud, and project it against the teeth of a wheel fastened to \|1e pulley. This wheel is insulated and Contact from it to the external circuit is established thru a mercury cup. As the pulley is rapidly rotated a jet of the fluid is thrown ,against the wheel, thu: making and brmk- gm ‘ ; = _F ' J" ‘ jif./fkgpéi 15; _.,_vw ";'__if"7 %..§f{ 1? *ff im `i`i;¥="f g .~ -, .V \,» _ ,QL q, .4 , ,,,fi_5:_7\ ,gi - .1 __ ~ _¢»»_f.-, ~ "°` av* ‘ V . ws If i ,Q-’\~ v» Bk is I, ` f\W'%‘*"§’ ‘ ’ jifi§l'¢ .- \ *A l A’ _;(;w5_. '_ E -Q'_'-» . 1' ~»» .-.~s=;Q