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Why Use an Electromagnetic Brake with Your Electric DC Motor?

June 22, 2021

Electromagnetic brakes are used in industrial and medical equipment to consistently hold a load in position at a specific stopping point. The brake hollow shaft is mounted on an electric motor shaft for a compact integration.

In an electromagnetic brake, a fixed field coil acts as an electromagnet to control the position of an armature so that it either engages or disengages with a structure to generate holding/braking torque. Electromagnetic brakes are available in power-on and power-off designs.

  • In a power-on brake, the brake is only engaged when the current flows in the field coil.
  • In a power-off brake, the brake remains engaged at all times unless the current is flowing in the electromagnet. We can find two types of power-off brake:
    • Permanent Magnet Power-off Brakes: Permanent magnet brakes are designed to dynamically stop and hold a moving load and for high cycle rate stopping. Electric power to the coil nullifies the attraction of the permanent magnet, releasing the brake.
    • Spring-set brakes: Automatically stop and hold a load in the event of a power failure or other emergency stop situations. The braking force is applied by the use of a compression spring. Fully dynamic friction material allows for repeated braking cycles from the full motor speed with no torque fade. Usually, an optional manual release allows the brake to be released by hand.

Examples of using a brake in an application:

Automated Window Shades - Automated window shades can provide environmental comfort to users as well as providing the ease of adjusting the shade automatically versus manual operation. The power-off brake allows the motor to hold a shade position when power is removed. This ensures the shade user has the correct shade position, even in the case of power failure.

Robotic arm joints - A robotic arm is a type of mechanical arm, usually programmable, with similar functions to a human arm. One of the main risks of robotics is an uncontrolled motion by a robot. Robots need power-off brakes to apply to hold torque once the motor moving the joint has stopped and to provide dynamic stopping in the event of an emergency.

Seat actuator - In the seat actuation systems, all aspects of the seat, including footrest, leg rest, and recline axes, must be moved simultaneously to reach their desired position at the same time. The power-off brake allows the motors to hold the seat position when power is removed.

An electromagnetic brake in combination with a DC motor is a nice solution for holding a load or for safety in case of power failure. Portescap provides a fully compact motor+brake integrated solution. To learn more about what we can do for your business, please visit our website or call your regional representative.