Performance Characteristic Summary

Performance Characteristics of a Magnetic Particle Clutch or Brake

A magnetic particle brake is a two element device, one rotating and one stationary (frame). When the coil is excited, the rotating member is connected to the frame by the slip-torque value until it stops. A magnetic particle clutch is a three element device, two rotating (input, output) and one stationary (frame). When the coil is excited, the two rotating members are connected by the slip-torque value until they are rotating as one.

Force Limted conducts dynamic tests of every unit before shipping and includes the performance curve measured during testing with the unit. The unit may be operated at any point on the performance curve or may be operated with varied excitation where dynamic control is needed. These units are ampere-turn devices, so current control is necessary for constant torque. The curve provided with each unit is a current-torque curve showing the characteristic on increasing current and decreasing current for both clockwise and counter-clockwise directions. Present commercial devices have some hysteresis, but this is kept low with sophisticated materials.

The following is a sample of a performance curve measured from a clutch-brake clutch assembly. It shows the output torque for any given input current, under increasing or decreasing current, and rotating clockwise and counter-clockwise.