A three-phase, 5 kVA, 208 V, four-pole, 60 Hz, wye-connected synchronous machine has negligible stator winding resistance and a synchronous reactance of 8 ohms per phase at rated terminal voltage. It is operated as a synchronous motor from a three-phase, 208-V, 60 Hz supply. The field excitation is adjusted so that the power factor is unity when the machine draws 3 kW from the supply. (a) Find the excitation voltage and the power angle. Draw the phasor diagram
(b) If the field excitation is held constant and the shaft load is slowly increased, determine the maximum torque (pull-out torque) the motor can deliver.
(c) If the load is NOT changed and is the same as in (a) but the field excitation is increased by 150%, find the stator current and the power factor