Protective Circuit - Hobart 60CU20 Operation And Maintenance Manual With Illustrated Parts List

OM-2226 / Operation and Maintenance Manual
60CU20 / Series 500062 / 400 Hz. Generator Set

Protective Circuit

NOTE: Protective monitoring is not completely functional until the load contactor is CLOSED. Since it is not
advisable to vary voltages for test purposes while delivering power to an aircraft, the GPU should be
connected to a load bank for trouble shooting protective circuits. To avoid repetition, it will be assumed that
TEST/RESET push-button switch has been pressed and the load contactor has been closed before
commencing each test.
Trouble, Symptom,
Condition
1. Load contactor
opens during power
delivery. Over
voltage fault
indicated.
2. Load contactor
opens during power
delivery. Under
voltage fault
indicated.
May 2, 2013
Revision 2
Probable Cause
a. Over-voltage condition
may have been result of a
sudden drop in load, or
possible tampering with
REG potentiometer, and
may have been a normal
action.
b. Defective CTL board
a. Under-voltage condition
may have been result of
a sudden shock load, or
possible tampering with
REG potentiometer, and
may have been a normal
action.
b. Defective CTL board
Test, Check, and/or Remedy
Press TEST/RESET push-button switch and
resume power delivery. Observe voltmeter to be
certain voltage is normal 115 VAC. Adjust to
normal if necessary. If load contactor is opened
again and the fault code meter indicates an over-
voltage condition, proceed to step b.
Use REG potentiometer to reduce voltage to 110
VAC. Observe voltmeter and gradually increase
voltage with potentiometer. If sensing circuit CTL
board opens the load contactor at any value less
than 125 VAC, it is defective. Replace CTL board.
Press TEST/RESET push-button switch and
resume power delivery. Observe voltmeter to be
certain voltage is normal 115 VAC. Adjust to
normal if necessary. If load contactor is opened
again and the fault code meter indicates an under-
voltage condition, proceed to step b.
Use REG potentiometer to reduce voltage to 100
VAC. Observe voltmeter and gradually decrease
voltage with potentiometer. If sensing circuit CTL
board functions to open load contactor at any value
great than 100VAC, it is defective. Replace CTL
board.
Chapter 2-4
Page 16