Question

When Ea>Vt machine is said to be operating in which of the following mode?

(a) Depends on the Shaft speed

(b) Generating

(c) Motoring

(d) Inducing

This question was posed to me in exam.

I want to ask this question from Electromagnetic Power and Circuit Models in section Circuit Model, Emf and Torque of DC Machines

Answer 1

Right choice is (b) Generating

To explain I would say: The machine operates in generating mode (puts out electrical power) when Ia is in the direction of induced emf Ea. For the given armature circuit Vt = armature terminal voltage= Ea – Ia * Ra; which implies Vt < Ea.