Generac Power Systems 53187 - Manual (Page 45)

PARTI
THE REVOLVING FIELD AC GENERATOR
1 SECTION 1.7- TROUBLESHOOTING
(UNITS WITH 10 INCH STATOR)
Diagnostic Tests (Continued)
Results:
1. If field boost voltage Is NOT indicated in Step 4, a
problem exists In the field boost w iring.
2. If field boost voltage Is NOT indicated in Step 3, but
IS indicated in Step 4, replace W ires 4,4A and the field
boost resistor.
3. If field boost voltage is indicated in Step 3, go to Test
9.
TEST 9- CHECK VOLTAGE REGULATOR:
Discussion: If you follow ed the troubleshooting
"Flow Chart* carefully, the only rem aining possible
cause of zero, residual, low or high voltage is the
voltage regulator.
Procedure: Try adjusting the voltage regulator as
outlined in Section 1.9, "OPERATIONAL TESTS AND
ADJUSTMENTS".
Results: If Regulator adjustm ent does not correct
the problem , rem ove and replace the Regulator. Then,
test the unit and adjust the Regulator.
TEST 10- TEST ROTOR ASSEMBLY:
Discussion: If fixed excitation voltage is applied to
the Rotor and the generator’s AC output voltage does
not read about half rated voltage, the Rotor side of the
voltage regulator circuit is suspect. This test w ill outline
the procedure for testing the Rotor w inding.
Procedure: To test the Rotor w indings for an open,
shorted or grounded condition, proceed as follow s:
1. To gain access to the -Rotor slip rings, rem ove the
rear bearing carrier cover and gasket.
2. Disconnect W ires No. 1 and 4 from the brushes, then
rem ove the brush holders w ith brushes to prevent
interaction during the test.
3. Set a VOM to its ’Rx1’ scale and zero the m eter.
4. Connect the positive (+) m eter test probe to the
positive (+) slip ring. This slip ring is the one nearest
the Rotor beanng.
5. Connect the com m on (•) VOM test probe to the
negative (•) slip ring. The m eter should indicate the
resistance of the Rotor w indings.
Rotor W inding Nom inal Resistance
Approxim ately 8.5 Ohm s
NO TE: A reading of 'Infinity' Indicates an open circuit.
A very high resistance Indicates a partial open. A low
reading Indicates shorted turns.
6. Now , set the VOM to a very high resistance scale,
such as "Rxl0,000* or "RxlK* and zero the m eter.
Then, check the Rotor for a grounded condition as
follow s:
a. Connect the positive (+) VOM test probe to the
E ositive (+) slip ring, nearest the Rotor bearing.
. Connect the com m on (-) VOM test probe to fram e
ground, such as the Rotor shaft,
c. The m eter should read *infinity*. Any reading other
than "infinity* indicates a grounded condition.
Results:
1. If the Rotor is good, go on to Test 11.
2. If Rotor is open, shorted or grounded, it m ust be
replaced.
TEST 11- CHECK BRUSHES AND SLIP RINGS:
Discussion: Refer to Test 12 in Section 1.6.
Procedure: See Test 12 in Section 1.6.
Results: Clean slip rings or replace brushes as
necessary. Brushes should be replaced in com pletes
sets. If brushes and slip rings are good but the problem
persists, go to Test 12 on the next page.
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