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Hysteresis Brake Dynamometers (HD series) are versatile and ideal for testing in the low to middle power range (max. 14 kW intermittent duty). Hysteresis Brakes do not require speed to create torque, and therefore can provide a full motor ramp from free-run to locked rotor. Brake cooling is provided by convection (no external source) or by air (compressed air or dedicated blower) depending on the model. Hysteresis Dynamometers have both continuous and intermittent power ratings where the dynamometer is capable of dissipating more power for shorter periods of time. All Hysteresis Dynamometers have accuracy ratings of ±0.25% to ±0.5% full scale, depending on size and system configuration. Also available are special designs for high-speed motor testing.
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Pure Hysteresis Brakes produce torque strictly through a magnetic air gap without the use of magnetic particles or friction components. This method of braking provides far superior operating characteristics (smoother torque, longer life, superior repeatability, high degree of controllability, and less maintenance and down time) which make them the preferred choice for precise tension control during the processing of nearly any material, web or strand.
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ZF Hysteresis brakes can accommodate power ratings from 0.05 to 040 Nm, with integrated planet gaer box up to 270 Nm.
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Advantages
The superior design of these hysteresis devices provide several inherent advantages over magnetic-particle and friction devices. They operate on a frictionless design principle with virtually nor wear. This provides such advantages as: longer expected life, superior torque repeatability, life cycle cost advantages, broad speed range, excellent environmental stability and superior operational smoothness.
Control
In an electrically operated hysteresis brake or clutch, 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 15 - 35% above rated torque is possible. In a permanent magnet device, the field coil is replaced by a magnet which provides the precise field strength necessary to produce rated torque without the need of electrical excitation. Since the field strength produced by a permanent magnet is a constant value, the resulting torque will also be constant. Physical realignment of the pole structure will result in limited (but predictable) changes in torque. Special designs utilizing this method are available and will allow for adjustments down to approximately 30 - 40% of rated torque.
Longer expected life
Hysteresis brakes and clutches produce torque strictly through a magnetic air gap, making them distinctly different from mechanical-friction and magnetic particle devices. Because hysteresis devices do not depend on friction or shear forces to produce torque, they do not suffer the problems of wear, particle aging and seal leakage. As a result, hysteresis devices typically have life expectancies many times that of friction and magnetic particle devices.
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Magnetic Technologies Ltd. offers a complete line of hysteresis brakes for tensioning and torque limiting.
• Torque range from 0.1 inch ounce to 140+ inch pounds.
• Hysteresis brakes have no break-away torque, no wearing parts, and use no electricity.
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