The induction motor is an electric motor classified under the asynchronous motors. Like these, this has an induction (squirrel-cage) motor, in which through a rotating field produced by the stator a torque is created.

However, unlike the asynchronous motors fed with three-phase current, the induction motor runs on single-phase alternating current.

Since the minimum of two phase-offset voltages necessary for generating a rotating field are not available from the alternating current mains, a so-called “split phase“ must be generated: one of the two stator windings is supplied direct from the AC mains, while a capacitor is switched in series with the second winding. This effects the desired phase-shift of the voltage in the second winding.

Induction motors are also suited to direction reversal using a single-pole reversing switch. This is one of their advantages compared with the shaded-pole motor.

There are also induction motors on which the “split phase“ is switched off after starting. We therefore differentiate between running capacitor and starting capacitor.

Its greater weight compared with a three-phase motor, its inferior starting torque and the capacitor additionally required effectively prevent its more widespread use. Its main advantage is the possibility of operating it efficiently with single-phase AC voltage. The smoothness in running which is typical of asynchronous motors, freedom from maintenance, a long service life and a greater efficiency than the shaded-pole motors which are also suitable for single-phase operation are all factors which have given it a wide field of application. 

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