What is principal of shaded pole induction Motor?

The principle of a shunt-wound induction motor mainly involves its construction and working process. Here is a detailed explanation:

Construction

The stator of a shunt-wound induction motor has a salient pole that is formed by the magnetic poles of the magnet facing towards the armature of the motor. Each pole of the motor is energized by its field winding coil, and a copper ring acts as a shading coil. The motor's poles are stacked, which means that multiple layers of material are used to make the rod, thereby increasing the strength of the rod. Slots are constructed at a certain distance from the edge of the rod, and short-circuited copper coils are placed in these slots.

Working Principle

When power is connected to the rotor winding, an alternating flux is induced in the iron core of the rotor. A small portion of the flux is connected to the motor's shading coil because it is short-circuited. The change in flux induces a voltage within the ring, causing circulating current to be induced within the ring. The circulating current generates flux within the ring, which opposes the main flux of the motor. There is also a 90° spatial displacement between the main motor flux and the shading ring flux. Due to the time and spatial displacement between the two fluxes, a rotating field is induced within the coil. The rotating field generates starting torque within the motor. The field rotates from the uns shadowed portion of the motor to the shaded portion.

Simplified Work Process

• Magnetic Flux Induction: When the power supply is connected, the stator winding generates an alternating magnetic field.

• Magnetic Flux Lag: A portion of the magnetic flux is short-circuited through the copper ring (shunt coil), causing this part of the flux to lag behind the main magnetic flux.

• Rotor Field: Due to the phase difference between the main magnetic flux and the shunt pole magnetic flux, a rotating field is formed.

• Starting Torque: The rotating magnetic field interacts with the induced current in the rotor to produce starting torque, causing the rotor to begin rotating.

Features

• Unidirectional Rotation: A shaded pole motor can only rotate in one specific direction and cannot reverse.

• Low Starting Torque: Due to the design, shunt-wound motors have low starting torque.

• Simple Structure: No centrifugal switch or other complex components, resulting in a lower failure rate.

To sum up, the shunt-wound induction motor achieves simple single-phase AC motor functionality through its unique construction and operating principles, making it suitable for small household appliances and devices that do not require high starting torque.