Magnetic particle clutches and brakes

Steplessly variable torque – torque transmission using fine-grained iron powder

The characteristic feature of the magnetic particle clutch is that the torque can be varied steplessly and smoothly depending on the excitation current.

Magnetic particle clutches and brakes are electromagnetically operated friction clutches or brakes in which a special magnetic powder serves as the friction lining.  The loose magnetic powder (highly abrasion-resistant, specially alloyed iron powder) is located in the air gap between the outer rotor and the inner rotor. This fine-grained iron powder forms magnetic chains depending on the level of electromagnetic excitation, thus transmitting the torque. The level of excitation determines the rigidity of these powder chains and, therefore, also the amount of torque that can be transmitted.

When the set torque is exceeded, the clutch or brake will slip smoothly without jerking. Magnetic particle clutches and brakes are designed for continuous slip applications as long as the heat dissipation limit is not exceeded.

The magnetic powder is subject to slight wear when in the slip state. A drop in torque indicates that the powder is worn. When minimum limit values for the respective application can no longer be achieved, the worn powder can be replaced with new powder. The service life of the powder depends on the load during operation.

The main advantage of magnetic particle clutches and brakes is that the motion sequences are smooth and jerk-free.

Magnetic particle clutches and brakes are mainly used in conveyor belt technology and in processing machines for paper, plastic and textile tensioning, for torque and speed control, as torque limiters or for start-up control.

Suitable control equipment is required to control the magnetic particle clutches and brakes.