Hobart 6921 Series Operation And Maintenance Manual page 111

OM-2040 / Operation and Maintenance Manual
90D20 / Generator Sets
Generator and Excitation Circuit
Trouble, Symptom & Condition
2. No (or low) output voltage
when operating in MANUAL
mode.
3. Load contactor (K1) will not
close when control switch (20,
Fig. 1 is held in CLOSE
position. Generator running at
normal voltage. No fault lights
on.
February 28/94 Revised
Test or Inspection
a. Defective generator
manual control excitation
circuit.
b. Defect in manual voltage
control portion of excitation
circuit.
c. Defective AUTO-MANUAL
switch (33, Fig. 1).
d. Defective rectifier (CR3)
(Sect. 1-1; 14, Fig. 8).
e. Defective resistor (R11)
(See 1, Fig. 5).
f. Defective rheostat (R61)
(32, Fig. 1)
a. In addition to defective
wiring and connections in
the AC and DC load
contactor actuating circuits,
the load contactor may be
prevented from closing for
any of the following reasons:
b. Blown fuse (F1) )1-1; 16,
Fig. 9)
c. Defective (open) relay in
protective module (1-1; 4,
Fig. 9).
Corrective Action
Place AUTO-MANUAL control
switch (33, Fig. 1) in AUTO
position. If a normal voltage is
NOT produced, perform checks
as instructed in GENERATOR
AND EXCITATION CIRCUIT
TROUBLE 1, above. If a normal
voltage is produced, proceed to
step "B" below
Check as follows:
Check contacts and operation
of AUTO- MANUAL switch.
Replace if defective.
Check diodes (see 2-3, Para..
6). Replace rectifier if defective.
Jumper resistor (1, Fig. 5). If
normal voltage (depending on
rheostat) is produced, replace
resistor.
Connect a jumper across
rheostat. If maximum (manual
control) voltage is produced,
replace rheostat.
After checking fuse (F1) in step
(1) below, check all wiring and
connections in the load
contactor circuits on the engine
control panel, the protective
relay tray and power module.
Then check components as
follows:
Remove and inspect fuse.
Replace if blown.
Use a jumper with clip and prod
terminals to GROUND terminal
"H" in the test receptacle. If
contactor will now close,
replace module or complete
protective relay tray (12, Fig. 1)
Chapter 3-1
Page 19