Question: a 1000 kva 4160 v threephase fourpole 60 hz yconnected...
A 1000 kVA, 4160 V, three-phase, four-pole, 60 Hz, Y-connected synchronous motor has a synchronous reactance of 19.4 Ω and achieves rated open-circuit voltage at a field current of 142 A. It is operated from a stiff power system which maintains the motor terminal voltage at its rated value.
a. [2 marks] At what speed does the motor operate?
b. [4 marks] Draw the per-phase equivalent circuit for the motor.
c. [8 marks] The motor is initially operating at a load of 500kW with the field current adjusted to achieve unity power factor operation. Calculate the corresponding field current.
d. [7 marks] The load is suddenly increased to 800kW. Calculate the resultant terminal power factor if the field current remains unchanged from part (c).
e. [4 marks] What is the maximum torque the motor can produce if the field current remains unchanged from part (c)?