The Operating Principle of Electromagnetic Braking Systems

Electromagnetic clutches or brakes are braking systems that operate electrically but transmit torque mechanically, hence why they’re referred to as electro-mechanical. Over the years, they’ve become known as electromagnetic instead of electro-mechanical, highlighting their actuation method instead of physical operation. Since they started becoming popular over half a century ago, the variety of designs and applications has increased substantially, but their basic operation remains the same even today.

The electromagnetic braking system is very suitable for remote operation since there’s no mechanical lineage required to control its engagement, thus it provides a fast and smooth operation. However, since the energy dissipates as heat in the actuator when the clutch is engaged, there are risks of overheating. Moreover, the maximum operating temperature of the brake is limited by the temperature ratings of the insulation in the electromagnet. This is one of their limitations, the other disadvantage is their higher cost.

Common Appliances
Some common places where an electromagnetic braking system can find use are conveyor drives, printing machinery, factory automation and copier machines. Furthermore, they can be used in automobiles, where they replace the clutch pedal with a simple switch button. You can use smaller electromagnetic brakes to drive a compressor of an air conditioning system.

The Parts of the System
The main components of an electromagnetic brake are a rotor, a coil shell, armature and a hub. The armature plate is lined with friction protection. The rotor is in front of the coil. When the clutch activates, the electric circuit energizes the coil which generates a magnetic field. As a result, the rotor portion gets magnetized. When the magnetic field surpasses the air gap between the armature and rotor it pulls the armature towards the rotor. The friction force, which is generated as a result, transfers the torque. The engagement time depends on the air gap, inertia and the strength of the magnetic field. The contact is gone when the voltage is removed from the coil. In most designs, a spring is used to hold the armature back, providing an air gap when the current is removed.

Final Thoughts
Electromagnetic brake systems have been enjoying immense market success in the past couple of decades. They’re used in most areas of mechanical engineering when production sequences have to be synced. As the drive runs continuously with the clutch rotor, all the energy from the upstream drive can be used to accelerate the output. They can be switched alternately, and as a result, can accelerate or decelerate the output shaft. Torque transmissions are achieved through friction.