Hobart 120CU20, Operation And Maintenance Manual With Illustrated Parts List

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OM-2228 / Operation and Maintenance Manual
120CU20 / Series 500120 / 400 Hz. Generator Set
October 15, 2013 Chapter 2-3
Page 8
b In any LINE-TO-LINE position, voltmeter reading should be 200 volts when the LED under
the voltmeter indicates two of the phases being checked.
(4) Check accuracy of frequency meter
a Connect a master frequency meter of known accuracy to the terminals of the frequency
meter.
b Compare meter readings. Error must not exceed 1% of full scale.
NOTE: Make all protective system tests with the unit operating under a load for the following steps.
Reference Chapter 2, Section 4, for all fault codes.
(5) Check operation of over-voltage circuit and fault code display.
a With the unit running at a normal load, adjust the coarse adjustment potentiometer (Figure 7)
on the voltage regulator clockwise to increase voltage until the over-voltage sensing circuit
actuates the protective monitor. After the protective monitor is activated, the load contactor
will open and the fault code display will display fault “
70.16 ”. At 125 volts, the circuit will trip
after a 1-second time delay. At higher values of voltage, time delays for over voltage trips are
as follow:
•
At 140 volts, the circuit will trip within 160 milliseconds.
•
At 180 volts, the circuit will trip within 50 milliseconds.
b If the load contactor does not open under the conditions described in step (a), refer to the
Troubleshooting Chart in Section 2-4.
c Return unit to normal operating conditions by adjusting coarse adjustment potentiometer
(turning it counterclockwise) and pressing “
TEST/RESET ” button switch to clear the fault
code.
(6) Check operation of under-voltage circuit and fault code display.
With the unit running at a normal load, adjust the coarse adjustment potentiometer on the voltage
regulator counterclockwise to decrease voltage until the under-voltage sensing circuit actuates
the protective monitor. After the protective monitor is activated, the load contactor will open and
the fault code display will display fault “
70.17 ”. Follow the following steps below to activate the
under-voltage protective monitor. A stopwatch is required for this check.
a With the unit running at normal load, use the output voltage coarse adjustment potentiometer
on the voltage regulator to reduce the voltage to 104 volts. The load contactor should NOT
open.
b Reduce voltage in increments of 1 volt, with a time delay of 7 seconds between steps. At a
setting of 100 volts, the load contactor will open and the under voltage light will glow after a 7-
second time delay.
c If the load contactor does not open under the conditions described, refer to the
Troubleshooting Chart in Section 2-4.