Working of Single –phase induction motor

Working : Construction of a single -phase motor is same to that of a three -phase induction motor except that the stator is given with a single- phase winding. Therefore, it has a stator with slots, and squirrel cage rotor with a small air-gap in among. When it is linked to single- phase ac supply, alternating current flows in its stator winding and the polarity of stator poles would alternately be N and S. The field so produced will be pulsating i.e. polarities will be alternating with the flux rising and falling in strength. The current induced in the rotor will tend to turn it in both directions alternately and therefore the rotor will be at standstill because of inertia. If rotor is given a push by hand or by another means in any direction, it will rotate in the similar direction developing operating torque. Therefore a single -phase induction is not self- starting and needs special starting means.