Brief Idea of Induction Motor

Brief Idea of Induction Motor

Induction motor: is an energy conversion device that converts electrical energy into useful rotational kinetic energy, it is an application of the Faraday's law of induction.

Sectional View

3-ph Induction Motor

 

Drawing of Induction Motor

Induction motor are the most commonly used motors in many applications. These are also called as Asynchronous Motors, because an Induction motor always runs at a speed lower than synchronous speed. Synchronous speed means the speed of the rotating magnetic field in the stator.

An Induction motor has basically two parts – Stator and Rotor

The Stator is made up of a number of stamping with slots to carry three phase winding. It is wound for a definite number of poles. The winding are geometrically spaced 120 degrees apart. Two types of rotors are used in Induction motors - Squirrel-cage rotor and Wound rotor. 

 

A squirrel-cage rotor consists of thick conducting bars embedded in parallel slots. These bars are short-circuited at both ends by means of short-circuiting rings.

A wound rotor has three-phase, double-layer, distributed winding. It is wound for as many poles as the stator. The three phases are wyed internally and the other ends are connected to slip-rings mounted on shaft with brushes resting on them. The brushes are connected to an external resistance that does not rotate with the rotor and can be varied to change the N-T characteristics. 

In fact an Induction motor can be compared with a transformer because of the fact that just like a transformer it is a singly energized device which involves changing flux linkages with respect to a primary(stator) winding and secondary(rotor) winding.