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Chapter 5 – Operating Principles
5.5
DAMPER CYLINDER
Hysteresis brakes, machined from (solid bar) magnetic material, represent a heavy mass. The load
cell behaves somewhat like a spring. A mass, supported by a spring, will resonate at the system's
natural frequency. For this reason, the dynamometer brake assembly must be dampened to filter
out torque data and to avoid stress and fatigue. The damper cylinder arm, attached to the brake,
connects to a piston within the hydraulic cylinder. When the load cell shipping/ restraining bolt was
removed (see Section 3.1 – Removal of the Load Cell Shipping/Restraining Bolt), the brake/load cell
assembly was centered and the damper became functional.
5.6
BRAKE CONTROL POWER
Any Magtrol Dynamometer Controller is universal in that it must operate all dynamometers. Due to
the higher level of current required by Magtrol's larger dynamometers, a booster power amplifier is
used to increase the control current. These supplies, contained within the dynamometer enclosures,
are in operation when the cooling fans are on.
5.6.1
HD-800/815
A booster power amplifier is used to increase control current by a factor of 2 with the HD-800 and
810 and a factor of 4 with the HD-805, 815 and ED-815 dynamometers. The schematic in Section
B.4 – HD-800-815 Brake Control Supply details the HD-800, 805, 810 and 815 brake power amplifier.
5.6.2
HD-825
An HD-825 uses a 5241 power amplifier to increase the control current. For the schematic, see
Section B.5 – HD-825 Brake Control Supply.
eD-815
anD
54
Magtrol Hysteresis Dynamometers
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