Generac Power Systems 53187 - Manual (Page 46)

SECTION 1.7- TROUBLESHOOTING
(UNITS WITH 10 INCH STATOR)
1
PART 1
THE REVOLVING FIELD AC GENERATOR
Diagnostic Tests (Continued)
TEST 12- CHECK W IRES 1 AND 4;
Discussion: An open or shorted condition in W ires
1 and 4 w ill have the sam e result as an open or shorted
Rotor w inding.
Procedure: Carefully inspect W ires No. 1 and 4,
betw een the Voltage Regulator and the Brushes. Look
for im proper connections, dam aged insulation, condi­
tion of w ire term inal ends, etc. Use a VOM to check the
w ires for an open or shorted condition.
Results:
1. Reconnect, repair or replace defective w ire(s) as
necessary.
2. If w ires are good, go to Test 13.
TEST 13- TEST STATOR AC POW ER W INDINGS:
Discussion: During the fixed excitation test, the
generator’s AC output voltage should have been ap­
proxim ately one-half rated voltage. It voltage w as less
than one-half rated voltage, one possible cause m ight
be an open, shorted or grounded stator AC pow er
w inding. You m ay w ish to review 'STATOR AC CON­
NECTION SYSTEM ' on Page 1.5-2.
Procedure: To test the stator’s AC pow er w inding,
proceed as follow s:
1. Disconnect and isolate stator leads 11, 22, 33 and
44. See appropriate w iring diagram .
2. Set an accurate VOM to its "Rxl" scale and zero the
m eter.
3. Check for an open circuit condition or for "turn-to-
turn" shorts as follow s:
a. Connect the VOM test probes across stator leads
11 and 22. The resistance of the stator w inding
should be indicated, about 0.21 ohm .
b. Connect the VOM test probes across stator leads
33 and 44. Reading should be approxim ately 0.21
ohm .
c. A reading of "infinity" indicates an open circuit. A
very high reading, indicates a nearly open circuit. A
very low reading indicates "turn-to-turn" shorts.
4. Check for a short betw een parallel w indings as
follow s:
a. Set the VOM to a high resistance scale, such as
"Rxl 0,000" or "RxlK". Zero the m eter.
b. Connect one VOM test probe to stator lead 11, the
other to stator lead 33. The m eter should read "infin-
ity".
5. Check for a grounded condition as follow s:
a. Set the VOM to a high resistance scale, such as
"Rxl0,000" or "RxlK". zero the m eter.
b. Connect one VOM test probe to stator lead 11, the
other to a clean fram e ground on the stator. The VOM
should read "infinity".
c. Now , connect one VOM test probe to stator lead
33, the other to a clean fram e ground on the stator.
The m eter should read "infinity".
Results: Replace the stator if it is open, shorted or
grounded.
TEST 14- CHECK AC VOLTAGE & FREQUENCY:
Discussion:You m ay w ish to review 'ROTOR RO­
TATIONAL SPEECr, as w ell as 'VOLTAGEAND FRE-
QUENCV on Page 1.5-2.
Procedure: Refer to Test 1, "CHECK AC OUTPUT
VOLTAGE". Use an accurate AC frequency m eter to
check AC output frequency, as w ell. No-load voltage
and frequency readings should be as follow s:
LIne-to-Neutral Voltage = 121-127 volts AC
LIne-to-llne Voltage = 242-254 volts AC
AC Output Frequency = 60.5-63.5 Hertz
Results:
1. If voltage and frequency are both correspondingly
low or high, go to Test 15.
2. If frequency is good, but voltage is LOW , go to Test
3.
3. If frequency is good, but voltage Is HIGH, go to Test
9.
TEST 15- ADJUST ENGINE GOVERNOR:
Discussion: See "Discussion" under Test 14,
above.
Procedure: Check and adjust the engine governor
as outlined in Section 1.9, “OPERATIONAL TESTS
AND ADJUSTM ENTS'.
Results:
1. If voltage and frequency are now acceptable, stop
tests.
2. If frequency is now acceptable, but voltage is low , go
to Test 3.
TEST 16- CHECK W IRES 2, 2A, AND 6:
Discussion: Unregulated AC output voltage from
the stator excitation w indings is deiivered to the voltage
regulator via W ires 2, 2A and 6. An open condition in
any part of this circuit w ill prevent excitation current
from reaching the reguiator and the Rotor.
Procedure: Refer to appropriate w iring diagram .
Carefully inspect the w ires for dam age, incorrect con­
nections, burned insulation, etc. Use a VOM to test
each w ire for an open or shorted condition.
Results: Reconnect, repair or replace any dam ­
aged or defective w ire(s).
TEST 17- CHECK FOR OVERLOAD CONDITION:
Discussion: The generator should never be over­
loaded. That is, the total of all electrical loads con­
nected at one tim e should not be greater than the unit’s
rated w attage/am perage capacity. If the generator is
overloaded, rpm , frequency and voltage can drop
sharply. In addition, the stator w indings can heat up and
cause the therm al protector to trip (open). If frequency
and voltage drop excessively w hen electrical loads are
applied, m ake sure the unit is not overloaded.
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