Capacitor-Start Induction Motor

By 3 August 2014

A single-phase induction motor with only a squirrel-cage rotor has no starting torque.

In this motor, a capacitor of suitable size is introduced in the starting winding circuit and a phase difference is created between the two windings.

In the capacitor-start single-phase motor, an auxiliary winding in the stator is connected in series with a capacitor and a centrifugal switch. During the starting and the accelerating period, the motor operates as a two-phase induction motor.

At about 67% of the full load speed, the switch disconnects the auxiliary circuit and the motor thereafter runs as a single-phase induction motor.