Exam Question

Q5 (a) List the factors that determine the starting torque of the three-phase induction motor. How does this torque generally compare with the value of the rated torque? (6) (b) A three phase, six pole, delta connected induction motor is supplied at 380 V, 60 Hz. It draws a current of 45 A at a power factor of 0.85 lag. The stator losses are 4 kW and the windage and friction losses total 3 kW. It runs at 19 rev/s. Calculate EACH of the following: (i) the rotor copper loss; (3) (ii) the shaft output power; (4) (iii) the shaft output torque. (3)