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Operating Principles
The hysteresis effect in magnetism is applied to torque control
by the use of two basic components–a reticulated pole structure
and a specialty steel rotor/shaft assembly–fastened together
but not in physical contact. Until the field coil is energized,
the drag cup and shaft can spin freely on its bearings. When
a magnetizing force from either a field coil or magnet is applied
to the pole structure, the air gap becomes a flux field. The
rotor is magnetically restrained, providing a braking action
between the pole structure and rotor. Because torque is produced
strictly through a magnetic air gap, without the use of friction
or shear forces, Hysteresis Brakes provide operating characteristics
such as:
- Absolute Smoothness
- Torque Independent of Speed
- Total Adjustability
- Long, Maintenance-Free Life
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- Highest Degree of Repeatability
- Quiet Operation
- Stability
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Control
In an electrically operated Hysteresis Brake, adjustment and
control of torque is provided by a field coil. This allows for
complete control of torque by adjusting DC current to the field
coil. Adjustability from a minimum value (bearing drag) to a
maximum value of rated torque is possible. Additional torque
in the range of 15-25% above rated torque may be available on
some brakes.
The amount of braking torque transmitted by the brake is proportional
to the amount of current flowing through the brake coil. The
direction of current flow (polarity) is of no consequence to
the operation of the brake. For optimum torque stability, a
DC supply with current regulation is recommended. This will
help to minimize torque drift attributable to changes in coil
temperature and in-line voltage, which can result in changes
in coil current, and consequently, in torque. |
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| Magtrol Inc. (USA): +1-716-668-5555 • magtrol@magtrol.com | Magtrol SA (Switzerland): +41 (0)26 407 3000 • magtrol@magtrol.ch |
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| © 1995-2008 Magtrol, Inc. |
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