Welcome to ELECTRICAL ENCYCLOPEDIA. In this article we gonna study about SHADED-POLE MOTORS.
CONSTRUCTION OF SHADED POLE MOTORS.
A Shaded pole motor is a simple type of self-starting single phase induction motor. It consist of a stator and a cage type rotor.
Stator is made up of salient poles. Each pole is slotted on side and a small copper ring is fitted on the smaller part of the slotted pole. The part on which copper ring is placed , it is called shaded pole.
Copper ring is also called a shading coil.
Shaded pole motor
WORKING OF SHADED POLE MOTOR.
When an alternating current flows in the field winding, an alternating flux is produced in the field core. A portion of this flux links with the shading coil i.e. copper ring. An emf is induced in the shading coil and hence an current circulates in it. This induced current produces a flux called induced flux which opposes the main core flux. The flux in the shaded portion lags behind the flux in the unshaded portion of the pole. The main flux and shaded pole flux are displaced in the space and time which is less than 90 degree. Since there is a space and time displacement between the two fluxes and hence condition for the rotating magnetic field are produced.Under the action of the rotating flux a starting torque is developed in the cage rotor. The direction of the rotating flux is from unshaded portion to the shaded portion of the pole.
Hence , shaded pole motors can run only in one direction from unshaded portion to the shaded portion
Reversal of direction of rotation is not possible in shaded pole motors.
APPLICATION OF SHADED POLE MOTOR.
Shaded pole motors are very economical. But starting torque of the motor is also very low. Losses are high and power is low. As well as power is also low. For this reason , the shaded pole motors are build in small sizes of lower power rating. They are most suitable for small devices like relays , fans like table fan , exhaust fan , hair driers , fans for refrigerator. They are also used in record players , tape recorders , slide projectors , photo copying machine etc.Thanks for reading.
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