Generac 86640 - Manual (Page 25)

NOTE: Before attempting to test the Stator excitation
winding, be sure the thermal protector has not failed
open. See Teat 13.
PR^OCEDURE:
1. Disconnect Wire 2 from the excitation circuit breaker (CB4).
2. Disconnect Wire 6 from the Voltage Regulator.
3. Use a VOM to test the resistance of the excitation windings.
Connect the VOM test leads across leads 2 and 6. The VOM
should indicate the resistance of the excitation windings.
a. For 8 kW units, reading should be approximately 1.00
ohm (plus or minus 10%).
b. For 10 kW units, resistance should be approximately
0.73 ohm (plus or minus 10%).
4. Now, set the VOM to a high resistance scale such as
"Rxl 0,000’ or *Rx1 K’. Zero the meter. Connect one VOM test
lead to Wire 6, the other test iead to a clean frame ground on
the Stator. The meter should read 'Infinity'.
RESULTS:
1. If stator excitation windings fall the test, replace the Stator
assembly.
2. If excitation windings check good, go to Test 15.
Test 15- Test Stator AC Power Windings
DISCUSSION:
An open or shorted condition in the Stator will adversely
affect generator AC voltage output. This test will check the
AC power windings for (a) open condition, (b) grounded
condition, and (c) short between parallel windings.
PR^OCEDURE:
1. Disconnect and isolate Stator leads 11,22,33 and 44. Also
disconnect and isolate Stator leads 5 and 6.
2. Set a VOM to Its 'Rxl' scale and zero the meter.
3. Connect the VOM test leads across stator leads 11 and
22
.
a. For 8 kW units, the meter should read approximately
0.21 ohm.
b. For 10 kW units, the VOM should indicate approximately
0.14 ohm.
NOTE: The actual realatance will vary slightly with tem­
perature, with a nominal variation as much as plus or
mlnua 10 percent.
4. Connect the VOM test leads across stator leads 33 and 44.
Resistance readings should be the same as In Step 3(a) and
3(b).
5. Now, set the VOM to a high resistance scale, such as
’Rx10,000' or 'RxlK'. Zero the meter. Connect one meter
test lead to stator lead 11, the other test lead to stator lead
33.
a. The meter should read 'infinity'.
b. Any reading other than 'infinity' Indicates a short be­
tween parallel windings.
6. With VOM still set for a high resistance, connect one VOM
test lead to stator lead 11, the other test lead to a clean frame
ground on the stator. Repeat the test with one test lead
attached to stator lead 33 and the other connected to a clean
frame ground on the stator.
a. The VOM should read '1011011/.
b. Any reading other than 'Infinity' Indicates a grounded
condition.
7. With the VOM still set for a high resistance, connect one
VOM test lead to stator lead 11, the other to stator lead 5.
Repeat the test with one VOM test lead connected to stator
lead 33, the other to stator lead 5.
a. In both cases, the meter should read 'Infinity'.
b. Any reading other than 'infinity' Indicates a short be­
tween windings.
RESULTS:
1. If any reading is bad, replace the stator assembly.
2. If stator checks good, go to Test 16.
Test 16- Check Sensing Leads
DISCUSSION:
The Voltage Regulator must sense ACTUAL AC power
winding voltage. Itr must then electronically 'compare' the
ACTUAL voltage to a REFERENCE voltage that is preset In
the Regulator. The Regulator acts to maintain an actual
voltage that is the same as the reference voltage by regulat­
ing excitation current flow to the Rotor.
If ACTUAL voltage sensing signals to the Regulator
become lost for any reason, the normal reaction of most
Regulators would be to think' that ACTUAL voltage Is too
low. The Regulator would then Increase excitation current
flow to the Rotor in an attempt to increase the ACTUAL
voltage. That is, the Regulator and Rotor would go to a 'Full
Field''^ condition and the generator’s AC output vdtage would
go to a very high maximum value.
However, the Voltage Regulator used on RV/IM models
is equipped with a 'sensing loss cutout' feature. That is, when
loss of sensing signals occurs, the Voltage Regulator will shut
down. When the Regulator shuts down, a complete loss of
excitation current flow to the Rotor will occur. The actual AC
output voltage will then drop dramatically to a value commen­
surate with Rotor residual magnetism (about 2 to 7 volts AC).
PROCEDURE:
1. With the generator running, observe the red LED (light
emitting diode) on the AC voltage regulator. If sensing voltage
is available to the regulator, the light should be ON.
a. if the light is OUT, complete Step 2 below.
b. If the light is ON, go to Test 17.
2. Connect an accurate AC voltmeter across the Voltage
Regulator sensing terminals (leads 11 and 22). The meter
should Indicate line-to-neutrai voltage. If not, complete the
following:
a. Carefully Inspect sensina leads 11 and 22, between the
engine control circuit board and the Voltage Regulator.
b. Inspect leads 11 and 22 between the engine control
circuit board and the AC connection panel.
c. Use a VOM to check sensing leads 11 and 22 for an
open or shorted condition.
RESULTS:
1. Reconnect, repair or replace any damaged, open, shorted
or defective sensing leads.
2. If sensing leads are good, go to Test 17.
Test 17- Check Voltage Regulator
DISCUSSION:
The Voltage Regulator Is discussed under Test 16 above, as
well as on Page 1.1-4. The Regulator Is equipped with two
safety features, as follows:
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