SHADED POLE MOTOR

A shaded-pole motor is one type of AC single-phase induction motor. It is basically a small squirrel cage motor in which the auxiliary winding is made of a copper ring surrounding a portion of each pole.This auxiliary winding is called a shading coil. Currents in this coil delay the phase of magnetic flux in that part of the pole enough to provide a rotating magnetic field. The direction of rotation is from the unshaded side to the shaded (ring) side of the pole.The effect produces only a low starting torque compared to other classes of single-phase motors.

These motors have only one winding, no capacitor nor starting switch, making them economical and reliable. Because their starting torque is low they are best suited to driving fans or other loads that are easily started. Moreover, they are compatible with triac based variable-speed controls, which often are used with fans. They are built in power sizes up to about 1/6 hp or 125 watts output. For larger motors, other designs offer better characteristics.