"PERMA-TORK",a magnetic torque control device

PERMA−TORK consists of twin magnets and one disc fixed on shaft.This shaft is supported by ball bearings.

Operating Principles.
As the hysteresis disk rotates through the field established by alternating poles, the magnetic state of the disk alternates. The resistance of the disk to change magnetic states, produces a retarding force. This retarding force is converted to a smooth consistent torque unaffected by speed.