What is Braking?
We know that brake is an equipment to reduce the speed of any moving or rotating equipment, like vehicles, locomotives. When a motor is in moving state, it has some kinetic energy stored in it. If you have to stop the motor, then you have to remove or dissipate this energy (commonly called brake energy).
Now there are 2 types to stop the motor :-
- Mechanical Braking
Convert this brake energy to heat energy by using mechanical brakes. They basically employ friction to the shaft to slow it down. This method has disadvantages like energy wasted, mechanical wear tear, etc.
- Electric Braking
Do some trick so that an electromagnetic torque is produced opposing the direction of motion of the motor, so that motor retards and finally halts down.
Types of Electric Braking
This braking methods can divide in to three parts mainly, which are applicable for almost every type of motors like DC motors, induction motors, synchronous motors, single phase motors etc.
Regenerative braking use whenever the speed of the motor exceeds the synchronous speed. This baking is called regenerative baking because here the motor works as generator and supply itself is given power from the load. Regenerative braking is that the rotor has to rotate at a higher than the synchronous speed of motor and power flow will be returned to the line.
The disadvantage of this type of braking is that the motor has to run at super synchronous speed which is may damage the motor mechanically and electrically, but regenerative braking can be done at sub synchronous speed if the variable frequency source is available.
Plugging or Reverse current braking.
In Plugging type braking method the terminals of supply are reversed, as a result of the generator torque also reverses which resists the normal rotation of the motor and hence the speed of motor decreases.
The main disadvantage of this method is that here power is wasted.
Rheostat or Dynamic braking
In this method, Armature is disconnected from the supply and a rheostat is connected across it. The field winding is left connected across the supply. So that armature is driven by the inertia and hence machine starts acting as a generator.
Thus the machine will now feed the current to the connected rheostat and heat will dissipate at the rate of losses. Braking effect is controlled by varying the resistance connected across the armature.
Advantages of Electric braking
- They can be manually adjusted at the controller to provide the correct braking capability for varying load conditions.
- They can be modulated to provide more or less braking force, thus easing the brake load on the motor.
If any query or suggestion about Electric braking please comment below or Email on Dipak@electricalidea.com.