334

INVENTIONS OF NIKOLA TESLA.

for operating a certain class of alternating motors founded on theaction of currents of differing phase. In view of the presentstate of the art it is thought sufficient to describe these arrange-ments in a few words only. The diagram, Fig. 180 II., showsa primary coil p, connected with one of its ends to the line l lead-ing from a high tension transformer terminal T t . In inductiverelation to this primary p is a secondary s of coarse wire in thecircuit of which is a coil c. The currents indiiced in the second-ary energize the iron core i, which is preferably, but not neces-sarily, subdivided, and set the metal disc d in rotation. Such amotor m 2 as diagramatically shown in Fig. 180 II., has beencalled a “ magnetic lag motor,” but this expression may be ob-jected to by those who attribute the rotation of the disc to eddycurrents circulating in minute paths when the core i is finallysubdivided. In order to operate such a motor effectively on theplan indicated, the frequencies should not be too high, not morethan four or five thousand, though the rotation is produced evenwith ten thousand per second, or inoi-e.

In Fig. 180 I., a motor m ( having two energizing circuits, A andb, is diagrammatically indicated. The circuit a is connected tothe line l and in series with it is a primary p, which may have itsfree end connected to an insulated plate p t , such connectionbeing indicated by the dotted lines. The other motor circuit bis connected to the secondary s which is in inductive relation tothe primary p. When the transformer terminal t, is alternatelyelectrified, currents traverse the open line l and also circuit a andprimary p. The currents through the latter induce secondarycurrents in the circuit s, which pass through the energizing coilb of the motor. The currents through the secondary s and thosethrough the primary p differ in phase 90 degrees, or nearly so, andare capable of rotating an armature placed in inductive relationto the circuits a and b.

In Fig. 180 III., a similar motor m 3 with two energizing cir-cuits Ai and b x is illustrated. A primary p, connected with oneof its ends to the line l has a secondary s, wdiich is preferablywound for a tolerably high k. m. f., and to which the two ener-gizing circuits of the motor are connected, one directly to theends of the secondary and the other through a condenser c, by theaction of which the currents traversing the circuit A t and b, aremade to differ in phase.

In Fig. 180 IV., still, another arrangement is shown. In thiscase two primaries p, and p 8 are connected to the line l, one