______braking is used where the load on the motor has very high inertia (e.g. in electric trains)?

• A. Rheostatic
• B. Coasting
• C. Plugging
• D. Regenerative

Answer: (D)

Regenerative Braking
Regenerative braking occurs whenever the speed of the motor is more than that of the synchronous speed. In this method, the motor runs as a generator, and the load is used to provide the required power to the supply. The main criterion for regenerative braking is that the speed of the motor becomes greater than the synchronous speed. This condition will lead to the motor acting as a generator and the direction of both the current and torque reversing. This method can be utilized where the load on the motor has very high inertia.
When the applied voltage to the motor is less than the back electromotive force (EMF), then both the armature current as well as armature torque reverses and the speed reduces. As generated EMF exceeds the applied voltage, the power transport takes place from the load to the supply.