After cleaning, start the engine and accelerate the
engine to high idle rpm. This procedure will help in
the removal of debris and drying of the core. Stop the
engine. Use a light bulb behind the core in order to
inspect the core for cleanliness. Repeat the cleaning,
if necessary.
Inspect the fins for damage. Bent fins may be opened
with a “comb”. Inspect these items for good condition:
welds, mounting brackets, air lines, connections,
clamps and seals. Make repairs, if necessary.
i01880286
Rotating Rectifier - Check
SMCS Code: 4465-535
The high voltage that is produced by an operating
generator set can cause severe injury or death.
Before performing any maintenance or repairs,
ensure that the generator will not start.
Place the engine control switch in the ““OFF”” posi-
tion. Attach ““DO NOT OPERATE”” tags to all start-
ing controls. Disconnect the batteries or disable
the starting system. Lock out all switchgear and
automatic transfer switches that are associated
with the generator.
Check the exciter armature. Ensure that the rotating
rectifier is tight. If a failure of a rectifier is suspected,
refer to Maintenance Procedure, “Rotating Rectifier -
Test”.
i01601961
Rotating Rectifier - Test
SMCS Code: 4465-081
Testing A Brushless Exciter
Rotating Rectifier With An
Ohmmeter
Table 23
Tools Needed
Part Number Part Name Quantity
6V-7070 Digital Multimeter 1
9U-7330 Multimeter 1
146-4080 Digital Multimeter
(RS-232)
1
7X-1710 Multimeter Probe
Group
1
Illustration 121 g00555106
If the failure of a rectifier is suspected, use the
following procedure.
1. Remove the cover from the exciter.
2. Remove the nut that secures the rectifier to the
heat sink.
3. Remove the diode lead.
4. Lift the rectifier from the heat sink.
5. Refer to Illustration 121 . Connect the ohmmeter's
leads across the rectifier. Note the meter reading.
6. Reverse the ohmmeter leads. Note the meter
reading.
The ohmmeter should indicate a low resistance when
the ohmmeter leads are across the rectifier in one
direction. The ohmmeter should indicate a high
resistance when the leads are reversed.
If the ohmmeter indicates a low resistance in both
directions, the rectifier is shorted. A high resistance in
both directions indicates an open rectifier.
Replace any faulty rectifiers with rectifiers that have
comparable operating characteristics. Include the
following information when a rectifier is being ordered
for replacement:
• Part Number of the rectifier
• Model number of the exciter
• Type of the exciter
148
SEBU7125-13
Maintenance Section
Rotating Rectifier - Check
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