Speed Control of an Induction Motor

There is a various method of speed control of an Induction Motor. The rotor speed of an induction motor is given by the equation shown below. From equation (1) it is clear that the motor speed can be changed by a change in frequency f, a number of poles P, and slip s. Any one or combinations of the below methods listed can be used to change the motor speed. All the methods of speed control of an induction motor are used in actual practice.

They are as follows:-

• Pole changing

The pole changing method is further divided into three types. They are named as:

1. Method of consequent poles
2. Multiple stator windings
3. Pole amplitude modulation

The other methods are as follows:-

• Stator voltage control
• Supply frequency control
• Rotor resistance control
• Slip energy recovery

The detailed description of each method of speed control is explained in the various methods individually.