Question

The desired voltage regulation for a single phase, 50 Hz transformer is zero. Its pu ohmic drop is 4% and pu reactive drop is 4%. The required power factor angle for the operation in degrees is?

(a) 45

(b) 90

(c) 30

(d) 60

I have been asked this question during a job interview.

This is a very interesting question from Machine Ratings topic in chapter Rating and Loss Dissipation of Electrical Machines

Answer 1

Correct option is (a) 45

The best I can explain: The power factor angle is, tan(phi)=pu resistive drop/pu reactive drop

                                                 = 4/4 = 1.