How to calculate the speed of the motor from H.P rating/voltage (frequency=50Hz) explain me?

Question

How to calculate the speed of the motor from H.P rating/voltage (frequency=50Hz) explain me?

Answer 1

Since you listed frequency, I suppose that you are asking about an AC motor. The synchronous speed of an AC motor is given by RPM = 120 X f / p where RPM is speed in revolutions per minute, f is frequency (Hz) and p is the number of poles of the stator winding (2, 4, 6 etc.). The constant, 120 is 60 seconds per minute X 2 poles per pole pair. The synchronous speed is the speed with which the stator's magnetic field rotates.

If the motor is a synchronous motor, the normal operating speed (rotor speed) is equal to the synchronous speed. If the motor is an induction motor, the rotor speed is slightly less than the synchronous speed. The difference is called "slip." The slip at full load is usually about 1.5% to 5% of the synchronous speed depending on motor design details. The slip is proportional to load, so it is almost zero at no load and about half of the full load value at half load.

Common synchronous speeds for 50 Hz AC motors are 3000 RPM (2 poles), 1500 RPM (4 poles) and 1000 RPM, (6 poles)