Question

The pole changing method of speed control is only applicable to which type of motor?

• A. Slip ring induction motor
• B. Squirrel cage induction motor
• C. Synchronous motor
• D. DC shunt motor

Hint:

Pole changing speed control is mainly used in squirrel cage induction motors.

Answer 1

The Correct Option is B

Concept: The synchronous speed of an induction motor is: \[ N_s=\frac{120f}{P} \] where \(f\) is frequency and \(P\) is number of poles.

Step 1: Speed can be changed by changing the number of poles.

Step 2: Pole changing is practically used in squirrel cage induction motors.

Step 3: Squirrel cage motors are robust and can be designed with pole-changing winding arrangements.

Step 4: Therefore, pole changing method is applicable to: \[ \boxed{\text{Squirrel cage induction motor}} \]