Motor Braking Methods

By 11 August 2014

Motor braking is to stop a running motor.

Removal of the supply given to the motor will make it stop. However, due to inertia, the motor will tend to rotate for some time before coming to a complete halt.

To stop the motor quickly, a braking mechanism is required. This is called motor braking.

While operating electrical drives, it is often necessary to stop the motor quickly and to reverse it. Particularly, in electrical hoist or crane applications, it is required to control the torque of the drive motor so that the load does not have undesired acceleration. Some applications require accurate positioning of the motor shaft.

The speed and accuracy of stopping and reversing operations of motors improve the productivity of the system. For example, take rolling mill motor application.

In such applications, braking torque is required which may be either electrical or mechanical. Braking can be broadly classified as:

• Electrical braking
• Mechanical braking.

Electrical braking
In electrical braking, the winding of the motor is used to produce a braking torque. A braking torque is developed during the braking operation. This braking torque opposes the motion of the rotating member or shaft. This is achieved by suitably changing the electrical connections of the motor. The motor operates on a speed–torque characteristic, depending upon the method of braking employed.

Mechanical braking
In mechanical braking, the frictional force between the rotating parts and the brake drums produces the required braking. To achieve this, mechanical equipment, such as brake linings and brake drums, are required. Whether electrical or mechanical, the braking of the drive should stop the motor at the specified point of time and position.