Exam Question

(a) Electric motors contain a stationary member as well as a rotating member. For each of the following machines, identify in which part of the motor three field winding and the armature winding are located: three phase induction motor, three phase synchronous motor, d.c. motor. (6)

(b) An 18.65-kW, 4-pole, 50-Hz, 3-phase induction motor has friction and windage losses of 2.5 percent of the output. The full-load slip is 4%. Compute for full load

(a) the rotor Cu loss

(b) the rotor input

(c) the shaft torque

(d) the gross electromagnetic torque.