Slip in Induction Motor

The voltage induced in rotor bars of an induction motor depends on the speed of rotor with respect to the magnetic fields. The term slip in Induction motors is used for representing the relative speed of rotor with respect to magnetic fields.

Mathematically formula to calculate

Slip (s) = [ η_sync – η_m ] / η_sync

where

η_sync = Speed of magnetic fields

η_m = Speed of motor shaft

The factor on the right side is often multiplied with 100 to represent slip in terms of slip percentage.

Slip %age = {[ η_sync – η_m ] / η_sync  } * 100

Important points to remember

1. The rotor of an induction motor always turns slower than the synchronous speed, so the slip and slip percentage is smaller than 1 and 100 respectively
2. Slip is actually the difference between synchronous speed and actual speed