Question

Why retardation test is carried on DC machine?

(a) To find stray losses

(b) To find eddy current losses

(c) To find field copper losses

(d) To find windage losses

The question was posed to me in class test.

The origin of the question is Efficiency of DC Machine- 2 in chapter Efficiency and Testing of DC Machines

Answer 1

The correct option is (a) To find stray losses

Easy explanation: This test is generally employed to shunt generators and shunt motors. From this method we can get stray losses of a machine. Thus, if armature and shunt copper losses at any given load current are known then efficiency of a DC machine can be easily estimated.