Adaptation.—If induction motors be connected to the same line with a synchronous motor that has a steady load, then the field of the synchronous motor can be over excited to produce a leading current, which will counteract the effect of the lagging currents induced by the induction motors. Owing to the weak starting torque, skilled attendance required, and the liability of the motor to stop under abnormal working conditions, the synchronous motor is not adapted to general power distribution, but rather to large units which operate under a steady load and do not require frequent starting and stopping.
Figs. 1,613 to 1,625.—Disassembled view of Western Electric three phase squirrel cage skeleton frame induction motor.
Induction (Asynchronous) Motors.—
An induction motor consists essentially of an armature and a field magnet, there being, in the simplest and most usual types, no electrical connection between these two parts.[2]
[2] NOTE.—The author prefers the terms armature and field magnet, instead of "primary," "secondary," "stator," "rotor," etc., as used by other writers, the armature being the part in which currents are induced and the field magnet (or magnets) that part furnishing the field in which the induction takes place.
According to the kind of current that an induction motor is designed to operate on, it may be classified as:
- 1. Single phase;
- 2. Polyphase.
The operation of an induction motor depends on the production of a magnetic field by passing an alternating current through field magnets.