People use electromagnetic (EM) clutches and brakes every day and often don’t realize it. Anyone who switches on a lawn tractor, copy machine, or car air conditioner may be using an EM clutch — and EM brakes are just as common.
Electromagnetic clutches operate electrically but transmit torque mechanically. Engineers once referred to them as electromechanical clutches. Over the years EM came to stand for electromagnetic, referring to the way the units actuate, but their basic operation has not changed.
Electromagnetic clutches and brakes come in many forms, including tooth, multiple disc, hysteresis, and magnetic particle. However, the most widely used version is the single-face design.
Both EM clutches and brakes share basic structural components: a coil in a shell, also referred to as a field, a hub, and an armature. A clutch also has a rotor, which connects to the moving part of the machine, such as a driveshaft.