Page 713 - Basic Electrical Engineering

corresponding to this rotor speed must, therefore, be 1500 rpm Thus, N =
r
1440 rpm and N = 1500 rpm.
s

Slip,

Rotor frequency, f = S × f = 0.04 × 50 = 2Hz
r

Example 8.6 A six-pole, three-phase synchronous generator driven at 1000
rpm supplies power to an induction motor which runs at a speed of 1440 rpm

on full load. Calculate the percentage slip of the motor and the number of
poles of the motor.

Solution:
The synchronous generator is rotated at a synchronous speed of 1000 rpm by
a prime mover. The synchronous speed N is expressed as
s

where f is the frequency of the generated EMF

or,

This synchronous generator now supplies power to the induction motor at a
frequency of 50 Hz. The synchronous speed of the rotating magnetic field

produced in the motor is

and