The concept of Slip is very simple. But first we must understand Synchronous Speed of electric motor(Ns) and Rotating Speed (Rotor Speed). Slip is the difference between these 2 quantities. Ns: the speed of the revolution of the magnetic field in the stator winding of the motor. It is the speed at which the electromotive force is produced by the alternating machine. Given by the formula-

Ns= 120*f/P

Ns: Synchronous Speed in rpm

f: Supply frequency in Hz

P: No. of poles

Rotor Speed (Nr): Actual running speed of motor

Slip in Induction Motor is the relative speed between the rotating magnetic flux and rotor expressed in terms of per unit synchronous speed. It is a dimensionless quantity. The value of slip in Induction Motor can never be 0.

Thus, Slip(s)= (Ns-Nr)/Ns