Question

Explain why the electromagnetic torque in the DC motor with separate excitation is negative in the case of countercurrent braking.

Answer 1

Answer:

n Dynamic Braking, a braking resistor Rb is connected across the armature as soon as the DC motor is disconnected from the supply mains. The motor now works as a generator, producing the braking torque. ... The connection diagram is shown below when braking with separate excitation is done.The armature terminals or supply polarity of a separately excited DC motor or shunt DC motor when running are reversed. Therefore, the supply voltage V and the induced voltage Eb i.e. back emf will act in the same direction. ... Thus, the armature current is reversed and a high braking torque is produced.