Question

The plugging gives the ___________
1. zero torque braking
2. smallest torque braking
3. highest torque braking
4. none of the above

Answer 1

Correct Answer - Option 3 : highest torque braking

Plugging:

• Plugging braking of induction motor is done by interchanging connections of any two phases of the stator with respect of supply terminals
• Plugging is used to reduce the speed of motors
• The supply voltage V and the induced voltage Eb (back emf) will act in the same direction
• The effective voltage across the armature will be (V + Eb) which is almost twice the supply voltage
• During plugging external resistance is also introduced into the circuit to limit the flowing current
• Thus, the armature current is reversed and high braking torque is produced
• It provides the highest braking torque in comparison to rheostatic and regenerative braking systems.