How is "Slip" defined in an induction motor?

The definition of "Slip" in an induction motor accurately describes the difference between the speed of the rotating magnetic field and the rotor shaft speed. In an induction motor, the rotating magnetic field created by the stator induces current in the rotor, which then generates torque. However, for this induction process to occur, the rotor must not be rotating at the same speed as the magnetic field; otherwise, no relative motion would exist to induce current.

Slip is expressed as a percentage and is given by the formula:

Slip = (Ns - Nr) / Ns

Where Ns is the synchronous speed of the magnetic field and Nr is the actual speed of the rotor. This characteristic is crucial because it allows the motor to produce torque and operate effectively. Understanding slip helps in evaluating motor performance, efficiency, and the design of motor control strategies.