Generator Excitation Circuits
Trouble, Symptom
Test, Check, And/or
and Condition
Probable Cause
Remedy
1.
No (or low) generator output
voltage in all phases.
Generator operating at 400 Hz.
a.
Idle-excitation relay (K68)
(2, Fig 3), or the generator
control PC board itself,
could be defective. A
defect in this circuitry can
prevent power from
reaching voltage regulator
Replace relay K68, bring unit up
to rated speed. Proper voltage
should now be generated. If not,
replace generator control PC
board, and recheck voltage. If
this doesn’t correct the problem,
proceed to Step
b
b.
Defective generator or
excitation circuit.
Place REGULATED/
DIAGNOSTIC switch (29,Fig. 2)
in DIAGNOSTIC position. This
applies 12-V DC from battery
to exciter field, which should
produce an indicated output
voltage of 100 +/- 20- V AC
line-to-neutral. If voltage
produced is within this range,
generator is good, and trouble
is in voltage regulator circuit.
Proceed to step B.
c.
Defective voltage regulator
Disconnect rectangular plug
connector of regulator wiring
assembly from suspect PC
board, and connect a properly
working PC board to regulator
wiring assembly, while avoiding
short circuiting bottom of
properly working PC board to
installed PC board. Then start
generator set and perform
tests and adjustments
according to instructions in
Section 2-3.
If generator set works properly
with properly working PC board
temporarily connected, shut off
generator set and replace
defective PC board with one that
is properly working (preferably,
same PC board used for this
troubleshooting check).
d.
Defective REGULATED/
DIAGNOSTIC switch (29,
Fig. 2)
Check switch thoroughly. A
defective switch may prevent
current reaching and/or leaving
voltage regulator. Replace
switch if defective.
OM-2084 / Operation and Maintenance Manual
90CU24 / Series 500392 Generator Sets
November 27/1997
Chapter 2-4
Page 13
