Shaded Pole Induction Motor

Shaded Pole Induction Motor

Definition: A self-starting single-phase induction motor with one of its poles shaded by a copper ring is what is meant by a “shaded pole induction motor.” The shaded ring is another name for the copper ring. This copper ring serves as the motor’s secondary winding. The shaded pole motor can only rotate in one direction; it cannot move in the opposite direction.

Why the Shaded Pole Induction Motor designs for low power rating?

The power losses in the shaded pole induction motor are very high, and the motor’s power factor is low. Induction motor’s starting torque is also incredibly low. The motor is inefficient for the reasons listed below. As a result, they maintain compact designs, and the motor has low power ratings.

Construction of Shaded Pole Induction Motor

Two or four poles may be present in the shaded pole motor. For the sake of simplicity, we use a two-pole motor in this article. The ratio of the motor’s pole count to its speed is inversely proportional.

Stator –

The shaded pole motor’s stator has a salient pole. The salient pole denotes that the magnet’s poles are directed towards the motor’s armature. The exciting coil of the motor excites each of its poles. The loops are shaded by the copper rings. The shading coil is the term for the loops.

The poles of the motor are laminated. So Lamination means multiple layers of material are used for making the poles. So, that the strength of the pole increases.

A distance between the slot’s construction and the poles’ edge. This slot is used to insert the shorted-circuit copper coil. The portion that a copper ring covers is referred to as the shaded portion, and the portion that is not covered by the rings is referred to as the unshaded portion.

Rotor –

The shaded pole motor uses the squirrel cage rotor. The bars of the rotor are skewed at an angle of 60º. The skew can be done for obtaining a better starting torque.

The lack of a commutator, brushes, collector rings, etc., makes the motor’s construction incredibly straightforward. The induction motor with shaded poles lacks a centrifugal switch. Therefore, there is a lower likelihood of the motor failing.

So The electrical switch known as a centrifugal switch begins to function by utilising the centrifugal force produced by the rotating shaft. Additionally, it is employed to regulate the shaft’s speed.

Shaded Pole Induction Motor Working

The supply induces an alternating flux in the rotor core when it is connected to the windings. Because the flux link is short-circuited, the small portion of it connects to the motor’s shaded coil. Because of the voltage that the fluctuating flux creates inside the ring, the circulating current creates it.

The circulating current creates a flux in the ring that is opposed to the motor’s primary flux. The flux causes the motor’s shaded area to: i.e.,

A. and the unshaded portion of the motor,

B. have a phase difference. The main motor flux and the shaded ring flux are also having a space displacement by an angle of 90°.

The connection diagram of the Shaded Pole Motor

The rotating magnetic field induces in the coil due to the time and space displacement between the two fluxes. The motor’s starting torque is produced by the rotating magnetic field. The field rotates from the motor’s shaded area to its unlit area.

Application of the Shaded Pole Induction Motor

The various applications of the shaded poles motors are as follows:

• Used in exhaust fans, hairdryers, and also table fans.
• They are suitable for small devices like relays and fans because of their low cost and easy starting.
• Record players, tape recorders, projectors, photocopying machines.
• Used in air conditioning and refrigeration equipment and cooling fans.
• Used for starting electronic clocks and single-phase synchronous timing motors.

Shaded Pole Induction Motor is used to power equipment with a low starting torque requirement.