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 2-4
Page 13
Trouble, Symptom,
Condition. Probable Cause. Test, Check, and/or Remedy.
Generator Excitation Circuits.
1. No (or low)
generator output
voltage in all
phases. Generator
operating at 400 Hz. a. Defective generator or
excitation circuit.
On REG place Regulated/ Diagnostic switch in
Diagnostic position. This applies 12 VDC from
battery to exciter field, which should produce an
indicated output voltage of 100 +/- 20 VAC line to
neutral. If voltage produced is within this range, the
generator is good, and trouble is in voltage regulator
circuit. Proceed to Step
b .
b. Defective voltage
regulator (REG).
Connect a properly working REG board to regulator
wiring assembly, avoid short circuiting bottom of
properly working REG board. Then start generator
set and perform tests and adjustments according to
instructions in Section 2-3. If generator set works
properly with a properly working REG board
temporarily connected, shut off generator set and
replace defective REG board with one that is
properly working (preferably, same REG board used
for this troubleshooting check).
c. Open fuse on REG. Check fuses thoroughly. Replace fuses if defective.
d. Defective connector at
voltage regulator, or
defective wiring from
regulator to exciter field.
Disconnect exciter wires at terminal strip. Using
jumper leads with clip terminals, connect 12 VDC to
wires. If generator will produce at least 80 VAC,
replace or repair connector and wiring between
voltage regulator and exciter field as required.