3-Phase Induction Motor Braking
- Plugging/ Reverse voltage braking
- Regenerative induction motor braking
- Dynamic induction motor braking
1)Plugging Braking of Induction Motor :
Plugging braking of the three-phase induction motor is carried out by changing the phase sequence of the induction motor. this method is also called reverse voltage braking. Plugging braking is done by interchanging connections of any two leads of the motor with respect to supply terminals.
A three-phase induction motor develops torque in the same direction as the rotating magnetic field (RMF) generated by the stator winding of the induction motor also in any two stator winding leads that are reversed the rotating magnetic field also gets reversed. hence if stator leads reverse by any means while motor rotating, torque is suddenly produced opposite to the original direction of rotation.
Regenerative Braking of Induction Motor
![]() |
Regenerative braking |
Regenerating braking of induction motor takes place when the motor runs above the synchronous speed, when the rotor speed, becomes more than rotating field speed, the slip becomes negative. The negative slip means that the induction motor now operates as an induction generator in the second quadrant and fed back power to the supply line.
The power fed to supply is given by the product of regenerative braking torque and the corresponding rotor speed. Fig shows that the amount of power returned to the supply line depends upon how much rotor speed is above synchronous speed. When rotor speed falls to synchronous speed, the regenerating braking of an induction motor comes to an end.
Dynamic Braking of Induction Motor
Dynamic braking of the three-phase induction motor is the slowing down of the motor by converting the kinetic energy stored in the rotating mass to the heat energy in the rotor/stator windings.
To achieve dynamic braking, the motor is switched from the supply line to a braking circuit that causes the motor act as a generator with a connected load.
The load is the resistance of the rotor or stator windings. since the only source of energy are the rotating parts of the induction motor and the motor-driven equipment.
Dynamic braking of the 3-phase induction motor can be accomplished by DC voltage injection or capacitive braking.
Disadvantage of this type of braking is it does not provide holding torque at the end of the braking period. Hence, where it required a mechanical brake must be used to hold the shaft. e.g hoist application where rolling is not permitted after a stop.
See Also