OM-2228 / Operation and Maintenance Manual
120CU20 / Series 500120 / 400 Hz. Generator Set
October 15, 2013
Chapter 2-4
Page 17
Trouble, Symptom,
Condition.
Probable Cause.
Test, Check, and/or Remedy.
Protective Circuit (continued).
3.
Load contactor opens
during power delivery.
Over frequency fault
indicated.
a.
Frequency adjust
switch is enabled.
Set frequency adjust switch to DISABLE
b.
Defective REG board.
If over-frequency faults continue after engine’s
ECM is proven to be good, and an over-frequency
condition does not exist, replace REG board.
4.
Load contactor opens
during power delivery.
Under frequency fault
indicated.
a.
Frequency adjust
switch is enabled.
Set frequency adjust switch to DISABLE
b.
Defective REG board.
If under-frequency faults continue after engine’s
ECM is proven to be good, and an under-frequency
condition does not exist, replace REG board.
5.
Load contactor opens
during power delivery.
Overload fault
indicated.
a.
There may have been
an overload condition.
Observe ammeter. Check for abnormal overload
condition and correct. If overload device functions
to open load contactor when an overload does not
exist, proceed to step B.
b.
Defective CTL board.
Replace CTL board.
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