_______ method is called reverse current braking

_______ method is called reverse current braking

Right Answer is:

Plugging

SOLUTION

Plugging

  • Plugging is also called reverse current braking.
  • The connections of the motor are reversed, reversing the direction of torque, thereby bring it to a quick stop. For this, either the direction of field current or the direction of armature current is reversed.

  • The field circuit usually has a large time constant due to the high value of inductance, so the time taken to bring the field current to zero is large. Hence, it is usual to reverse the armature current.
  • On reversing the armature current the supply voltage to the armature and back emf developed in it are additive. So, this condition is worse than the starting condition as the applied voltage to the armature is approximately double (V+E = 2V) to the supply voltage.
  • Hence, an external resistance is inserted in the armature circuit simultaneously with the reversal of the armature current. Braking torque can be regulated by varying the magnitude of this resistance.

The disadvantages of this method are:

1. The kinetic energy of the motor is dissipated in the external resistance in the form of heat. So, this method of braking is inefficient.

2. The braking in this method fails in case of failure of the supply.

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