Electromagnetic brake

Since becoming popular in the mid-20th century, especially in trains and trams, the variety of applications and brake designs has increased dramatically, but the basic operation remains the same.

[1] A friction-plate brake uses a single plate friction surface to engage the input and output members of the clutch.

Instead of squeezing a friction disk, via springs, it uses permanent magnets to attract a single face armature.

Spring applied brakes do not require a constant current control, they can use a simple rectifier, but are larger in diameter or would need stacked friction disks to increase the torque.

Because of their fast response, they can also be used in high cycle applications, such as magnetic card readers, sorting machines and labeling equipment.

As the particles start to bind together, a resistant force is created on the rotor, slowing, and eventually stopping the output shaft.

Since these units can be controlled remotely, they are ideal for test stand applications where varying torque is required.

When electricity is removed from the brake, the hysteresis disk is free to turn, and no relative force is transmitted between either member.

Multiple disk brakes are used to deliver extremely high torque within a small space.

Electro-mechanical disk brakes operate via electrical actuation, but transmit torque mechanically.

When electricity is applied to the coil of an electromagnet, the magnetic flux attracts the armature to the face of the brake.

As the disks are squeezed, torque is transmitted from the hub into the machine frame, stopping and holding the shaft.