A 1000 kVA, 3-phase, 11 kV, star-connected synchronous motor has negligible resistance and a synchronous reactance of 35 Ω per phase.
(a) What is the excitation emf of the motor if the power angle is 10º and the motor takes rated current at
(i) lagging power factor, and
(ii) leading power factor.
(b) What is the mechanical power developed and the power factor in part (a)?
(c) At what power angle will this motor operate if it develops an output of 500 kW at the rated line voltage and with an excitation emf of 10 kV (line)? What is the corresponding power factor?
(d) What is the minimum excitation at which the motor can deliver 500 kW at the rated line voltage without losing synchronism?