Question

A single phase transformer of 2200/220 V having rated l.v. current of 150 A has to undergo open circuit test on h.v. side. Which of the below instruments range should be used?

(a) 6A, 200V

(b) 150A, 22V

(c) 60A, 220V

(d) 6A, 20V

This question was addressed to me during a job interview.

This interesting question is from Open Circuit and Short Circuit Test in portion Transformers of Electrical Machines

Answer 1

Correct choice is (a) 6A, 200V

Easy explanation: Open circuit test is conducted on l.v. side, so the measuring instruments will be on the h.v. side.

            So the current in the h.v. side will be around 3-6% of the rated.