Question

The time period of rotor current of a 3-\(\phi\), 4-pole, 50 Hz, induction motor is 200 ms. Then slip speed of the motor is

• A. 1425 rpm
• B. 1350 rpm
• C. 75 rpm
• D. 150 rpm

Hint:

Slip frequency helps calculate the difference between synchronous and rotor speeds.

Answer 1

The Correct Option is D

Rotor current time period = \( \frac{1}{f_{slip}} = 0.2 \text{ s} \Rightarrow f_{slip} = 5 \text{ Hz} \) Synchronous speed \( N_s = \frac{120f}{P} = \frac{120 \times 50}{4} = 1500 \text{ rpm} \) Slip speed \( = \frac{f_{slip}}{f} \times N_s = \frac{5}{50} \times 1500 = 150 \text{ rpm} \)