Generac Power Systems 53187 - Manual (Page 33)

PARTI
THE REVOLVING FIELD AC GENERATOR
1 SECTION 1.6- TROUBLESHOOTING
(UNITS WITH 15 INCH STATOR)
Detailed Instructions
TEST 3- REPLACE REGULATOR, TEST/ADJUST;
Discussion: The Voltage Regulator lam ps (LED’s)
are norm ally ON. If the 'Regulator* lam p is OUT, the
Voltage Regulator has shut dow n or has failed. A
'Regulator
lam p ON condition indicates the
Regulator’s SCR’s (silicone controlled rectifiers) are
firing.
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VOCTAQE ADJUST
OAIN
In^
STABIUmr
Ine®
UNOERFREOUENCY
ADJUST
r«®
REGULATOR
SENSING
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EXCITATION
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Figure 2. The Part No. 67680 Voltage Regulator
Procedure: Unplug the voltage regulator connec­
tor plug. Rem ove the screw s, flatw ashers and
lockw asners that retain the regulator to the control
panel. Rem ove the regulator. Install the new regulator,
test and adjust as outlined in Section 1.9,
‘OPERA­
TIONAL TEST S AND ADJUSTM ENTS'.
NO TE: Before attem pting to adjust the voltage reg­
ulator, the engine governor m ust be properly ad­
justed to m aintain a no-load frequency of 60.5-63.5
Hertz (1815-1905 rpm ). Correct no-load AC output
voltage setting Is 121-127 volts AC (llne-to-neutral),
or 242-257 volts AC (llne-to-llne).
Results: If problem is corrected, discontinue tests.
If problem still exists, continue troubleshooting as indi­
cated in the 'Flow Charts".
TEST 4- TEST EXCITATION CIRCUIT BREAKER:
Discussion: See Figure 3. The excitation circuit
breaker is electrically connected in series w ith the
stator excitation w inding AC output to the voltage reg­
ulator. It is physically m ounted in the control panel
interior. Should the breaker fail open, loss of excitation
w inding output to the regulator w ill occur. W ithout exci­
tation current, the regulator w ill shut dow n and gener­
ator AC output w ill drop to a voltage com m ensurate w ith
Rotor residual m agnetism . The breaker cannot be reset
m anuaily (it is norm ally self-resetting). If it has failed
open, it m ust be replaced.
from excitation grinding
to voltage regulator
Figure 3. Excitation Circuit Breaker
Procedure: To prevent interaction, disconnect
W ires No. 2 and 162 from the circuit breaker term inals.
Set a VOM to its "Rxl' scale and zero the m eter.
Connect thè VOM test probes across the tw o circuit
breaker term inals. The m eter should read "continuity*.
Resuits: •
1. If the m eter displays any reading o(;her than "conti­
nuity", replace the excitation circuit breaker.
2. If the VOM reads "continuity", go on to Test 5.
NO TE: W hen reading resistance across the circuit
breaker contacts, a very sm all resistance reading
Is acceptable. An oxide film can build up on circuit
breaker contact surfaces, causing the sm all resis­
tance.
TEST 5- TEST STATOR EXCITATION W INDING:
Discussion: An open circuit in the stator excitation
(OPE) w inding w ill result in loss of excitation current to
the Voltage Regulator. An excitation w inding AC output
of approxim ately 4-8 volts AC is required to turn the
Voltage Regulator on. Thus, on loss of excitation w ind­
ing output, the Regulator w ill shut dow n and regulated
excitation current to the Rotor w ill term inate. Generator
AC ou^ut voltage w ill then drop to a value com m ensu­
rate w ith Rotor residual m agnetism plus field boost
current (about one-half norm al no-load AC output volt­
age). An open w inding w ill be Indicated by a VOM
reading of 'infinity* or a very high resistance reading. A
shorted excitation w inding w ill be Indicated by a veiy
low resistance reading. In the follow ing 'Procedure*^,
the excitation w inding w ill also be testedfor a grounded
condition.
Procedure: See Figure 4, next page. In the control
panel, locate unattached W ire No. 5. This is the therm al
protector bypass lead. Rem ove the w ire nut from end
of W ire No. 5. Also locate W ire No. 6, connected to Pin
6 of the voltage regulator plug. On som e units, a barrel
lug m ay be used to connect W ire No. 6 betw een the
voltage regulator and the stator excitation w inding. Test
the stator excitation w inding for an open, shorted or
grounded condition as follow s:
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