Generator and Excitation Circuit (cont.)
Trouble, Symptom & Condition
Test or Inspection
Corrective Action
No (or low) generator output
voltage in all phases.
Generator operating at 400 Hz
in AUTOMATIC mode.
(Continued)
f. Defective ballast resistor(s),
(See Fig. 5).
If output voltage was produced
when the generator set was
operated in MANUAL mode, the
resistors are good. If no voltage
was produced in MANUAL
mode, resistors could be
defective. Refer to Fig. 5 and
connect a jumper lead across
the ballast resistors. If an output
voltage is now produced,
replace resistor(s) as required.
g. Defective Amphenol
connector at voltage
regulator, or defective
wiring from regulator to
exciter field.
Disconnect voltage regulator
Amphenol connector (see 1-1;
Fig. 12). Using jumper leads
with clip and prod terminals,
connect ungrounded 12-V DC
to terminals “E” and “C” in loose
plug. Connect NEGATIVE to
terminal “E”. Connect
POSITIVE lead to “C” terminal
(See Fig. 6).
If the generator will NOT
produce a normal voltage,
replace or repair Amphenol
connector and wiring between
voltage regulator and exciter
field as required.
h. Defective voltage regulator.
All components in the excitation
circuit except the voltage
regulator have been tested in
steps (1) through (4) above.
This leaves only the regulator
as a cause of trouble. Replace
complete voltage regulator if the
magnetic amplifier regulator
430391C is used. If solid state
amplifier 489812A is used,
replace PC board.
OM-2040 / Operation and Maintenance Manual
90D20 / Generator Sets
Chapter 3-1
February 28/94 Revised
Page 18
Summary of Contents for 6921 Series
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