Question

A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Speed of the rotor field w.r.t. rotor structure is?

(a) 157 rad/s

(b) 150 rad/s

(c) 6.28 rad/s

(d) 145 rad/s

I have been asked this question during an interview.

The query is from Rotor Frequency topic in chapter Induction Machines of Electrical Machines

Answer 1

Correct option is (c) 6.28 rad/s

The best I can explain: Speed of the rotor field w.r.t. rotor structure  = 120*rotor frequency/Poles = 120*2/4 = 60 rpm = 6.28 rad/s.