Shaded-pole motor
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A shaded pole motor is a type of AC single phase induction motor. As in other induction motors the rotating part is a squirrel cage rotor. All single-phase motors require a means of producing a rotating magnetic field for starting. In the shaded-pole type, a part of the face of each field pole carries a copper ring 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 field. The effect produces only a low starting torque compared to other classes of single-phase motors.
these motors are compatible with triac-based variable speed controls, often of use 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.
The first photo is of a common C-frame motor. With the shading coils positioned as shown this motor will start in a clockwise direction as viewed from the shaft end. The second photo shows detail of the shading coils.
