Question

What is the purpose of performing retardation test after Swinburne’s test?

(a) To find stray load loss

(b) To find variable losses

(c) To separate out windage and friction losses

(d) To find shunt field losses

This question was posed to me during an interview.

The doubt is from Swinburne’s Test topic in chapter Efficiency and Testing of DC Machines

Answer 1

Correct answer is (c) To separate out windage and friction losses

The best explanation: While performing Swinburne’s test we get addition of all losses. So, if we want to treat each loss individually, one needs to separate them. Retardation test is thus used by disconnecting both armature and field of the running motor.