Generac Power Systems 53187 - Manual (Page 37)

PARTI
THE REVOLVING FIELD AC GENERATOR
1 SECTION 1.6- TROUBLESHOOTING
(UNITS WITH 15 INCH STATOR)
Detailed Instructions (Continued)
The field boost resistor, field boost diode, W ire No.
9 and W ire No. 4 are part of the control panel w iring
harness. See Figure 9. The resistor and diode are
connected in series w ith W ires No. 9 and 4, and are
encased in heat shrink tubing.
Procedure: In the control panel, locate the voltage
regulator and the engine control circuit board. Test field
boost system operation as follow s:
1. Unplug the 6-pln connector from the voltage regula­
tor. Tnis w ill prevent you from reading regulated exci­
tation voitage during the test.
2. Set a VOM to read DC volts.
3. Field boost W ire No. 9 attaches to Term inal 8 of the
engine control circuit board.
a. Connect the positive (+) VOM test lead to Term inal
8 of the engine control circuit board.
b. Connect the VOM com m on (-) test lead to fram e
ground.
4. Crank the engine and note the DC voltage reading.
Meter should indicate approxim ately 12 volts DC w hile
the engine is cranking.
5. Now , connect the VOM positive (+) test lead to Pin
4 of the regulator connector plug; connect the com m on
test lead to a clean fram e ground. Crank the engine and
the m eter should indicate 7-10 volts DC.
Results:
1. If no voltage is indicated in Step 4, a problem exists
in the engine control circuit board, or in the engine DC
control circuits. See Part 5, "ENGINE ELECTRICAL
SYSTEM ".
2. If no voltage is indicated in Step 5, an open circuit
exists in W ire No. 9, the field boost diode, field boost
resistor, or W ire No. 4 to the Regulator.
NOTE: By rem oving the heat shrink tubing around the
diode and resistor, these two com ponents can be
tested individually. The defective part can then be
rem oved and replaced. The resistor (Part No. 51980)
is rated 5 watts, W ohm s. The diode (Part No. 49903)
is ra ted 600 volts, 6 am ps.
' - , , -
©■
PART OF CONTROL PANEL
WIRING HARNESS
ITEM DESCRIPTION
1 hea T shr I nk
2 BARREL LUG
3 DIODE- 60DV., 6 AMP
4 RESISTOR-5 WATT. 10 OHMS
TEST 15- TEST VOLTAGE AND FREQUENCY:
Discussion: The generator's AC output frequency
is directiy proportional to engine speed. Generator’s
having a 4-pole Rotor w ill produce a 60 Hertz frequency
at 1800 rpm . Voltage is also proportional to AC fre­
quency. The unit w ill supply 120 volts (line-to-neutral)
or 240 volts (line-to-line) at 60 hertz; if frequency should
drop to 30 Hertz, voltage output w ill decrease propor­
tionally to 60/120 volts. It is apparent that a low gov­
erned speed w ill result In a reduced AC frequency and
voltage. Conversely, a high governed speed w ill pro­
duce an increased frequency and voltage.
Procedure; See Test 1. Check AC output voltage
as outlined (at no-load). Use an accurate AC frequency
m eter to check frequency (at no-load). The no-load
frequency should be 62 Hertz. No-load AC output volt­
age should be 121-127 (line-to-neutral); or 242-254
volts (line-to-line).
Results:
1. If both frequency and voltage are low , go to Test 16.
2. If frequency is good, but voltage is low , go to Test
17.
3. If no-load voltage and frequency are both high, go to
Test 16.
4. If frequency is good, but voltage is high, go to Test
17.
TEST 16- ADJUST ENGINE GOVERNOR:
Discussion: Refer to "DISCUSSION' under Test
15.
Procedure: See Section 1.9, "OPERATIONAL
TESTS AND ADJUSTM ENTS'.
TEST 17- ADJUST VOLTAGE REGULATOR:
Discussion: Procedures for this test and adjust­
m ent are outlined in Section 1.9.
TEST 18- CHECK FOR OVERLOAD CONDITION:
Discussion: The rated m axim um w attage/am per-
age capacity of the generator should not be exceeded
for continuous operation. Overloading the unit w ill re­
sult in rpm , frequency and voltage droop. Excessive
overloading w ill cause the AC circuit breaker(s) to trip.
Procedure: If an optional rem ote gauge panel is
installed, load current can be checked by observing the
AC am m eter on that panel. If such a panel is not
available, a clam p-on am m eter can be used to check
am perage.
Results:
1. If unit is not overloaded, go to Test 16.
2. If the unit is overloaded, reduce the total electrical
load to the rated w attage/am perage capacity.
Figure 9. Field Boost Part of W iring Harness
PAGE 1.6-9