The supply frequency of a 4 pole induction motor having a synchronous speed of 1800 RPM is:
- 50 Hz
- 60 Hz
- 120 Hz
- 240 Hz
Correct answer: 2. 60 Hz.
Explanation: The basic formula for Synchronous Speed of machines is:
![synchronous-speed-formula](https://electricalengineeringmcq.com/wp-content/uploads/2020/04/synchronous-speed-formula-1024x568.jpg)
From this we obtain:
f = P * Speed / 120 = 4 * 1800 / 120 = 60 Hz