The no load speed of an induction motor depends on 

The synchronous speed is given by

\({N_s} = \frac{{120f}}{P}\)

Where,

f is the supply frequency in Hz or C/s

P is the number of poles

The induction motor rotates at a speed (Nr) close but less than the synchronous speed.

Slip of an induction motor is given by,

\(s = \frac{{{N_s} - {N_r}}}{{{N_s}}}\)

Where,

Ns is the synchronous speed

and Nr is the rotor speed

Application:

• At no load rotor speed is approximately equal to synchronous speed. 
• So that no load speed of an induction motor depends on supply frequency and number of its poles