Two series motors are mechanically coupled. One machine is run as a motor and the other as a generator. The iron and friction losses of the machines will be identical when

Q. Two series motors are mechanically coupled. One machine is run as a motor and the other as a generator. The iron and friction losses of the machines will be identical when

A.            Their speeds are identical

B.            Their speeds and excitations are identical

C.            Their speeds are equal and back e.m.f.s are half the supply voltage.

D.            Their ratings and armature sizes are equal

Answer: Their speeds and excitations are identical