A magnetic particle clutch is a special type of electromagnetic clutch which does not use friction plates. Instead, it uses a fine powder of magnetically susceptible material (typically stainless steel) to mechanically link an otherwise free wheeling disc attached to one shaft, to a rotor attached to the other shaft.
This clutch is a form of powder clutch. Torque is transmitted mechanically, through a metal powder filling. In the magnetically controlled version, an applied magnetic field is used to lock the particles in place. Unlike a pure magnetic coupling though, this field takes no part in transmitting torque magnetically.
When a magnetic field is applied to the powder, it forms chains connecting the disc and rotor. The strength of the chains depends on the strength of the magnetic field.
Some advantages over a friction plate clutch include: