SSE JE Electrical Engineering 10-Dec-2020 Papers

The difference between the rotor speed (N) and the rotating magnetic flux speed (Ns) is called slip.
The induction motor slip is usually expressed as a percentage of synchronous speed (Ns) and is represented by symbol s.
Mathematically, Percentage slip, %s=[

Ns−N

Ns

]×100
Or fractional slip, s=

Ns−N

Ns

At start, N=0, therefore, Slip,s=

Ns−0

Ns

=1
At synchronous speed, Slip, S=

Ns−Ns

Ns

=0