Temperature Overload Protection; Silicon Diodes; Control Interlock Kit; Adjusting The Transformer-Rectifier - Hobart 120CU20 Operation And Maintenance Manual With Illustrated Parts List

OM-2228 / Operation and Maintenance Manual
120CU20 / Series 500120 / 400 Hz. Generator Set
g The contactor should open in 10 seconds. The fault code meter will read "70.30"
h Discontinue power delivery and let the cables cool for 2-3 minutes.

(7) Temperature Overload Protection

a Press "DC OUTPUT" push button to close the DC output contactor. The blue "DC OUTPUT"
lamp will glow indicating that DC power is being delivered to the load bank.
b Remove one wire from the thermostat switch located on the right side of the T-R heat sink.
This will open the switch, thus simulating an over temperature fault. The fault code meter will
read "70.44"

(8) Silicon Diodes

a Shut the GPU completely down removing all power from the system.
b Disconnect diode leads.
c Use a good quality ohmmeter, place one ohmmeter lead on the threaded end of the diode
and the other lead on the diode lead and the record value.
d Reverse the ohmmeter leads and record the value.
e The diode may generally be considered good if one reading is infinite or very high and the
other reading is extremely low.
(9) Control Interlock Kit (Optional)
a With the output cable sitting in the cable tray, start the GPU and bring the engine to rated
speed.
b Close the output contactor by pressing the "DC OUTPUT" push button. The output contactor
should open immediately with an "EF3" warning displayed on the fault code meter.
c Using a 28 VDC power source, apply a 28 VDC signal to the control socket of the output
cable (small socket).
d Close the output contactor by pressing the "DC OUTPUT" push button. The output contactor
should stay closed.
e Remove the 28 VDC power source and the contactor should open with an "EF3" warning.
7) Adjusting the Transformer-Rectifier (for units with DC option).
The T-R is design to be adjustment free. No adjustments required, other than periodically checking the
output voltage and adjusting the TRB PC board potentiometer as necessary.
October 15, 2013 Chapter 2-3
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