Question

When torque of the electromagnetic origin is in the opposite direction of rotation of armature, machine is said to be operating in which of the following mode?

(a) Depends on other parameters

(b) Generating

(c) Motoring

(d) Inducing

The question was posed to me by my school teacher while I was bunking the class.

This key question is from Electromagnetic Power and Circuit Models topic in portion Circuit Model, Emf and Torque of DC Machines

Answer 1

Right option is (b) Generating

The explanation is: In a generating mode, torque of the electromagnetic origin is in the opposite direction of rotation of armature, implying mechanical power is absorbed and a prime mover is needed to run the machine. Ea and Ia are in the same directions.