What is mean by slip in an induction motor?

Slip (S): It is defined as the difference between the synchronous Speed [Ns] of the rotating stator field and the actual rotor speed [N] .

Mathematically,

%Slip (s) = [(Ns - N)/N] *100

where

Ns - N : Slip Speed.

To note:

When

( i) Rotor is stationary ( i . e .) s=1

At this condition Voltage induced in rotor conductors is maximum.

(ii) rotor rotates @ Synchronous Speed ( i e ) Ns = N

At this condition Voltage induced in rotor conductors is zero.

In an induction motor

0.1% < s < 3% an essential need for a constant speed motor.

Rotor resistance is independent of slip [S].