Question

A 0.5 hp, 6-pole induction motor is excited by a 3 –phase, 60 Hz source. If the full-load speed is 

1140 rpm, calculate the slip.

Answer 1

$Ns=\frac{120 \times f}{P} \\ = \frac{120 \times 60}{6}=1200 \\ slip=\frac{N_s-N_r}{N_s} \\ =\frac{1200-1140}{1200} \\ =0.05$