how to calculate synchronous speed
Synchronous Speed When Alternating current (AC) is applied to the stator of a three phase motor, a rotating magnetic field is setup. This rotating magnetic field moves with a speed called synchronous speed. The Synchronous speed can be calculated as follows: 120 times the frequency (F), divided by the number of poles (P): The synchronous speed decreases as the number of poles increases. The table below shows the synchronous speed associated with various numbers of poles at supply frequencies of 50Hz and 60Hz: Rated Speed. The speed of operation of an AC motor when fully loaded at rated voltage is called the rated speed.