Electrical hysteresis units have an extremely wide torque range. Since these units can be controlled remotely, they are ideal for test stand applications where varying torque is required. Since drag torque is minimal, these units offer the widest available torque range of any of the hysteresis products. Most applications involving powered hysteresis units are in test stand requirements.
Fast response: Torque is independent of slip speed. It is also directly proportional to coil current, making response time extremely quick.
Repeatability: Under identical operating conditions, the unit will be able to duplicate it's performance. This makes it ideal for many testing applications.
Smooth operation: Since the unit transmits torque via magnetic flux, the torque is smooth throughout its operating rpm range.
Long life: Since torque is transmitted via an electromagnetic field, there are no wearing parts involved in the normal operation of the unit (except for bearings and seals). This means extremely long life. Hysteresis units will outlast any other type of electromechanical unit.
How It Works
Engagement: When the current/voltage is applied to the field, it creates magnetic flux. This flux passes into the rotor portion of the field. The hysteresis disk physically passes through the rotor without touching. These disks have the ability to become magnetized depending upon the strength of the flux (this dissipates when flux is removed). This means, as the rotor rotates, magnetic drag between the rotor and the hysteresis disk take place causing rotation. In a sense, the hysteresis disk is pulled after the rotor. Depending upon the output torque required, this pull eventually can match the input speed giving a 100% lock up.
Disengagement: When current/voltage is removed from the clutch, the armature is free to turn, and no relative force is transmitted between either member; therefore, the only torque seen between the input and the output is bearing drag.
Cycling: Cycling is achieved by turning the voltage/current to the coil on and off. Slippage should occur only during acceleration. When the clutch is running, there is no relative slip (if the clutch is sized properly), unless slippage is desired. Torque transfer is 100% efficient.