Hysteresis clutch is based on the hysteresis principle,and uses hysteresis to transmit torque. The excitation current and the transmitted torque are basically linear. In the case of no slip speed, it can transmit a certain torque, and has the advantages of fast response,simple structure, no pollution ,no noise,no impact vibration, and energy conservation. It is a multi-purpose,superior performance automatic control component. It can be widely used in the field,of tension control for buffer starting,overload protection,speed regulation,and winding in winding systems.