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GENERATOR TESTING
VISUAL INSPECTION
Whenever testing and troubleshooting a
generator set, it is always a good practice to
make a thorough visual inspection. Remove
covers and look for any obvious problems.
Burnt windings, broken connectors, leads,
mounting brackets, etc., can usually be
identified. Look for any loose or frayed
insulation, loose or dirty connections,
broken wires. Be sure all wiring is clear of
rotating parts.
Verify that the generator is connected for the
voltage required this is especially important
on new installations.
Check for any foreign objects, loose nuts,
bolts, and electrical connectors. Clear paper,
leaves, building materials, etc., that could be
sucked into the generator. (Generators are
air-cooled. Air enters the lower portion of
the conduit box.) Check the air gap for
clearance or obstructions (main generator
and exciter).
If possible, rotate the generator rotor by
hand to be sure it turns freely.
If serious problems can be identified before
attempting to operate the machine,
additional damage can be avoided.
CONSTANT EXCITATION
(12V BATTERY) TEST
THEORY: The generator output voltage is
dependent on generator speed, generator
design, load, and exciter input current. If the
generator speed and exciter input are known,
the output voltage at no load can be
measured and compared to the design value.
Problems can be isolated to either the gen-
erator or regulator system by using this test.
TEST PROCEDURE:
1. Shut the generator set down.
2. Connect a voltmeter to the generator
output.
3. Disconnect the Fl and F2 leads at the
regulator.
4. Connect a 12-volt battery capable of
supplying 1 amp to the Fl and F2 leads. Fl is
plus (+), F2 is minus (—).
CAUTION: Beware of arcing when
connecting leads. Stay clear of battery vents.
Escaping hydrogen gas can explode. If
hazardous conditions exist - use a suitable
switch to connect or disconnect the battery.
5. With no load on the generator, (main
breakers open) run generator at rated speed.
6. Measure the generator output voltage.
7. Shut generator down.
8. Disconnect battery (see Caution - Step 3).
9. Compare voltage reading with value
shown in section 12.
Conclusion: If voltage readings are normal,
the main generator and exciter are operating
properly. Troubleshooting should continue
with the regulator. If readings are not normal
the problem is in the generator. Continue
testing diodes, surge suppressor, windings.
55
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