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Magtrol Hysteresis Dynamometers
4.1.10
T
eMPeraTure
Temperature rise has a more complex effect on hysteresis brake load torque and is difficult to quantify.
As the temperature of the brake increases, differential expansions cause dimensional changes that
tend to increase torque. Conversely, electrical resistance in the rotor increases with temperature,
resulting in decreased Eddy current generation and torque, all in a variable frame.
Where current and speed remain fixed, there may be a gradual torque increase over a period of a few
moments. This will generally stabilize at 0.5% (for small dynamometers, up to HD-500) to 2% of
the starting torque value, per 1000 rpm of applied speed.
Note:
r
iSe
If highly accurate long-term torque stability is required, consider the
Magtrol DSP7000 Dynamometer Controller. This is a computer-
controlled closed loop system capable of maintaining either constant
torque or speed.
51
Chapter 4 – Testing
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