CHAPTER XIX.

Another Type of Tesla Induction Motor.

It will have been gathered by all who are interested in theadvance of the electrical arts, and who follow carefully, step bystep, the work of pioneers, that Mr. Tesla has been foremost toutilize inductive effects in permanently closed circuits, in theoperation of alternating motors. In this chapter one simple typeof such a motor is described and illustrated, which will serve asan exemplification of the principle.

Let it be assumed that an ordinary alternating current genera-tor is connected up in a circuit of practically no self-induction,such, for example, as a circuit containing incandescent lampsonly. On the operation of the machine, alternating currents willbe developed in the circuit, and the phases of these currents willtheoretically coincide with the phases of the impressed electro-motive force. Such currents may be regarded and designated asthe “ unretarded currents.”

It will be understood, of course, that in practice there is al-ways more or less self-induction in the circuit, which modifies toa corresponding extent these conditions; but for conveniencethis may be disregarded in the consideration of the principle ofoperation, since the same laws apply. Assume next that a pathof currents be formed across any two points of the above cir-cuit, consisting, for example, of the primary of an induction de-vice. The phases of the currents passing through the primary,owing to the self-induction of the same, will not coincide withthe phases of the impressed electromotive force, but will lagbehind, such lag being directly proportional to the self-inductionand inversely proportional to the resistance of the said coil.The insertion of this coil will also cause a lagging or retardationof the currents traversing and delivered by the generator behindthe impressed electromotive force, such lag being the mean orresultant of the lag of the current through the primary alone andof the “ unretarded current ” in the entire working circuit. Next