Question

A synchronous motor is operated at a bus voltage of 1.5 pu and drawing 1.0 pu at zpf leading current. Its synchronous reactance is 0.4 pu. What is the excitation emf of the motor?

(a) 2.0 pu

(b) 1.5 pu

(c) 1.0 pu

(d) 1.1 pu

The question was posed to me in unit test.

This intriguing question comes from Measurement of Xd and Xq in chapter Synchronous Machines of Electrical Machines

Answer 1

Right choice is (d) 1.1 pu

To explain I would say: E = V-I*X = 1-0.5=0.5 pu.