AC MACHINES-1 (66761) Theory
Completion requirements
15. Understand the principle of speed control of induction motor.
A three phase induction motor is basically a constant speed motor so it’s somewhat difficult to control its speed. The speed control of induction motor is done at the cost of decrease in efficiency and low electrical power factor. Before discussing the methods to control the speed of three phase induction motor one should know the basic formulas of speed and torque of three phase induction motor as the methods of speed control depends upon these formulas.
Synchronous Speed
Where, f = frequency and P is the number of poles
The speed of induction motor is given by,
Where,
N is the speed of the rotor of an induction motor,
Ns is the synchronous speed,
S is the slip.