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7.6 IR Compensation Trimpot (IR)
The IR Trimpot sets the amount of compensating voltage required to keep the motor speed constant
under varying loads. If the load does not vary substantially, the IR Trimpot may be set to a minimum
level (approximately 1/4 of full clockwise rotation). The IR Trimpot is factory set to provide 3 Volts of
compensation for controls with 90 Volt DC output and 6 Volts of compensation for controls with 180
Volt DC Output. To increase the amount of compensating voltage, rotate the IR Trimpot clockwise. To
decrease the amount of compensating voltage, rotate the IR Trimpot counterclockwise.
See Figure 7-6.
Note:
In order for the IR Compensation to operate properly, the correct Plug-In Horsepower Resistor
®
must be installed for the particular motor and input voltage being used, as described in Section
4. Calibration of the IR Trimpot is normally not required when the proper Plug-In Horsepower
Resistor
®
is installed. Excessive IR Compensation will cause the motor to become unstable,
which causes cogging (“hunting” or “zooming”).
Figure 7-6 IR Trimpot Range
