Electrical hysteresis units have an extremely high torque range. Since these units can be controlled remotely, they are ideal for testing applications where varying torque is required. Since drag torque is minimal, these units offer the widest available torque range of any electromagnetic product. Most applications involving powered hysteresis units are in test stand requirements. Since all torque is transmitted magnetically, there is no contact, so no wear occurs to any of the torque transfer components providing for extremely long life.
When the current is applied, it creates magnetic flux. This passes into the rotor portion of the field. The hysteresis disk physically passes through the rotor, without touching it. These disks have the ability to become magnetized depending upon the strength of the flux (this dissipates as flux is removed). This means, as the rotor rotates, magnetic drag between the rotor and the hysteresis disk takes 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% lockup.
When current 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.
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