Question

A 12 pole, 3-phase alternator drives at a speed of 500 r.p.m supplies power to an 8 pole, three-phase induction motor. If the slip of the motor at full load speed is 4 %, calculate the full load of the motor. 

Answer 1

 $N_s=\dfrac{120f}{p}\\ 500=\dfrac{120f}{12}\\ f=50Hz\\ Speed\ of\ induction\ motor\\ N_s=\dfrac{120\times {50}}{8}=750rpm\\ N_r=N_s(1-s)\\ N_r=750(1-0.04)=720rpm\\$