Q. A two-pole rotating machine with a singly excited magnetic field system as its stator and a rotor (that carries no coil) has a stator-coil inductance that can be approximated by L(θ) = (0.02 - 0.04 cos 2θ - 0.03 cos 4θ) H, where θ is the angle between the stator-pole axis and the rotor axis. A current of 5 A (rms) at 60 Hz is passed through the coil, and the rotor is driven ata speed,which can be controlled, ofωm rad/s.

(a) Find the values of ωm at which the machine can develop average torque.

(b) At each of the speeds obtained in part (a), determine the maximum value of the average torque and the maximum mechanical power output.