Hobart 100D20 Operation And Maintenance Manual With Illustrated Parts List page 114

OM-2032 / Operation and Maintenance Manual
100D20 / Generator Sets
Generator and Excitation Circuit
Trouble, Symptom & Condition
1. No (or low) generator output
voltage in all phases.
Generator operating at 400 Hz
in AUTOMATIC mode.
Chapter 3-1
Page 18
Probable Cause
a. Defective generator or
excitation circuit.
b. Defective generator.
CAUTION: DO NOT use
battery on unit to flash field
with generator turning
voltage regulator. Damage
results from the introduced
ground
c. Defect in VOLTAGE REG.
excitation circuit.
d. Defective AUTO-MANUAL
switch (31, Fig. 1)
e. Defective excitation
deenergization relay (K16)
(1-1; 3, Fig. 8).
Corrective Action
The first check is an easy one
which will allow the mechanic to
reach some definite conclusions
about where the trouble is. Place
the AUTO-MAN switch (31, Fig. 1)
in MANUAL position. If a normal
voltage (for the rheostat setting) is
now produced, the generator is
good, and the trouble is in the
voltage regulator
circuit. Proceed to step C. If
switching to MANUAL control did
not affect generator output, the
trouble is likely in the generator,
but to prove the generator is
defective, proceed to step B.
Use the test receptacle (31, Fig.
6) to connect ungrounded 12-V
DC to the exciter field. Using
leads with alligator clips and test
prods, connect 12-V DC
NEGATIVE lead to terminal "D".
Terminal identifying letters are
plainly visible on the face of the
test receptacle. Connect
POSITIVE lead to terminal "F". If
no output voltage change is
indicated when the exciter field is
energized, the generator is
defective.
Stop operations and see 2-3,
Para. 4 for further generator
testing. If the generator produces
approximately 140-V AC when the
exciter field is energized, the
trouble is in the voltage
regulator-excitation circuit.
Proceed to step C.
Check as follows:
Check the switch thoroughly. A
defective switch may prevent
current reaching and/or leaving
the voltage regulator. Replace
switch if defective.
Check EDR contacts. A faulty
EDR can prevent power from
reaching the voltage regulator.
Replace relay if defective.
March 31/94 Revised