Tesla Motors Operated From Single Phase Two-Wire Alternating Circuits

Sunday, January 1, 1893
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Auuluzv, x 893 ELECTRIC POWER. I7 TESLA MOTORS OPERATED FROM SIHNGLE PHASE TWO-WIRE ALTERNATING CIRCUITS. Those interested in Mr. Tesla’s investigations will recall that in 1888 he read a paper before the American Institute of Electrical Engineers laying down the principles of his new multiphase system of operating alternating current motors, of which they have since seen their practical application. The results are cov- ered in two patents which have recently been issued to him. ln this multiphase system it will be remembered, each motor has two or more independent energizing circuits through which are passed alternating currents, having in each circuit such a difference of phase that by their combined or resultant action they produce a rotary pro- gression ofthe poles or points of maximum magnetic effect of the motor and thereby maintain the rotation of the armature. To the successful operation of a system of this kind, in na FND. I. TESLA MOTOR WITH EN- FIG. 2. TESLA MOTOR WITH SELF- Ex<:lZlNG CIRKJUITS. INDUC'1'i0N COIL. at least three wires are necessary to convey the different currents, and Mr. Tesla has, therefore, devised means for operating phase motors from the ordinary single- phase alternating circuit, by creating the difference of phase locally at and in the motor, ln all the methods described below, the fundamental idea involved is to pass a single alternating current through both of the energizing circuits of the motor, and to retard the phase of the current in one circuit to a greater or less extent than in the other. The distri- bution of current between the two motor circuits is eFfected either by induction or by derivation. The diagram Fig. x shows a motor with two energiz' ing circuits, c and n, One of these circuits, C, is con- nccted directly with the line circuit, while the other set D, is connected up in the secondary circuit of a transformer T. The primary P of this transformer, is connected to the line circuit, 'I`he alternations of cur- rent in the line tend to establish in their passage through

i 8 ELECTRI the coils c, a polarity opposed to that set up in the coils n. and if the currents in the two sets of coils coincided |11 their phases, no rotary effect would be produced. But the secondary current developed in the coil P of the transformer, uill lag behind that in the primary, which lag may be increased to a suiiicient extent to practically obtain the same result as though two independent cur- rents were used to energize the motor. 2 ` A S j R‘ R C D FIG. TESLA MOTOR WITH TWO FIG. 4, TESLA MOTOR WITH SELF-IN~ DE/\I) RESISTANCHS. . DUCTION CQII. AND DEAD RESISTANCE. In another form, shown in Fig. 2. the arrangement of the parts is similar to that shown in Fig. 6, except that a self-induction coil s, is introduced into one energizing circuit of the motor. The effect of thus increasing the self-induction in one of the circuits is to retard the phases of the current ,passing therein to a greater extent than in the other circuit, and in this way to secure the neces» sary difference in phase between the two energizing currents to produce the rotation of the motor. In Fig. 3 there is shown a type of motor in which t\vo dead resistances R R are included respectively in the energizing coils of the motor. No rotary effect will be produced as long as the resistances are equal but by varying the resistance in one circuit the retarda- tion of the current in that circuit will be varied and corresponding effects produced. For example, a reduc- tion of the resistance in one circuit imparts to the motor rotation in one direction while a reduction of the resistance in the other circuit will produce a rota- tion in the opposite direction. By means of the two f \ C © » iii' I t . jig. . I I " fill C c ji? D ° 1 R f’ VW => _______'f.__i_ _ _ FIU. 'IIESLA MOTOR WITH TWO FIG. 6. TESLA I\I0'I`0II WITH ENER- SELF-INl)\YC'I`ION COILS. GIZING CIRCUITS IN MULTIPLE ARC. resistances, therefore, capable of variation or of being bodily withdrawn from or inserted in the circuits by simple means, rotation of the motor is secured. In Fig. 4 a self-induction coil s is included in one of the motor circuits and a dead resistance R in the other. The incre ased self-in duction in one circuit thus produced acts to increase the difference of phase between the cur- rent in that motor circuit and the unretarded currentin C POWER. Wai.. vr., No. ei, the line circuit. On the other hand, the introduction of the dead resistance in the other motor circuit reduces the retardation and brin s the phases of the current in it more closely in accom? with those of the unretarded current, thus producing a correspondingly greater dif- ference of phase between the two currents in the ener~ gizing circuits c and D. In Fig. 5, two self-induction coils are shown, one in each motor or energizing circuit. One of these coils is much smaller than the other and has less self-induction or counter-E. M. F. than the other, so that the phases of current will be retarded to a less extent than in the other. ` In Fig. 6 the two energizing circuits of the motor are shown connected in multiple arc to the line circuit and in one ot these circuits is a resistance R. Assuming the two motor circuits to have the same degree of self-induc- tion no rotary effect will be' produced by the passage through them of an alternating current from the line. But if one of the motor circuits, as c, be varied or modi- fied by the introduction of a dead resistance R, the self- induction of that circuit or branch is reduced, and the phases of current therein retarded to a correspondingly less extent. The relative degrees of retardation of the phases of the current in the two motor circuits with re- spect to those of the unretarded current in the circuit ia thus produced. will set up a rotation of the motor. There is finally another type in which one set of en- ergizing coils is of finer wire than the other or has a greater number of convolutions; or each circuit may contain the same number of convolutions, but be com- posed of different conductors, as, for instance, one of copper, and the other of German silver.