Alpha Technologies AlphaGen 3.5_5.0kW Kohler COM5 - Manual (Page 53)

TP-6482 8/06 53 Section 5 Component Testing and Adjustment
6. Check the cold resistance of the stator windings by
connecting the meter leads to stator leads 1 and 2,
1 and 3, and 2 and 3. See Figure 5-28 for stator
winding resistance values. Replace the stator if
any of the resistance checks reveal an open
winding. If the resistance test is not conclusive,
perform a megohmmeter test on the stator as
described in step 7.
Note: Most ohmmeters do not measure very small
resistance values accurately. Check for
continuity of the windings with no shorts to
ground.
The stator is functional if the
resistance reading (continuity) is low and
there is no evidence (heat discoloration) of
shorted windings.
Generator Set Voltage
Rating, VDC Stator Resistance, Ohms
36 0.014
48 0.024
Figure 5-28 Stator Resistance
7. If the resistance test in the previous step is not
conclusive, perform a megohmmeter test to
determine whether the stator is shorted to ground.
a. Use a megohmmeter to apply 500 volts DC to
any stator lead and the stator’s frame. Follow
the
instructions of the megohmmeter’s
manufacturer when performing this test. A
reading of approximately 500 kOhms
(1/2 MOhm) or higher indicates that the stator
is in good condition. A reading of less than
approximately
500 kOhms (1/2 MOhm)
indicates deterioration of the winding insulation
and possible current flow to ground.
b. If the megohmmeter reading is less than
500 kOhms, replace the stator.
5.8.2 Rotor
The rotor uses permanent magnets. There are no tests
or field adjustments for the rotor.
5.9 Fault Shutdown Switches
Check the continuity of the high engine temperature
(HET) and low oil pressure (LOP) switches. Check for
loose connections and open or short circuits in the
connecting wires before replacing the switches.
High Engine Temperature (HET) Switch
The HET switch is normally open. Shut down the
generator set and allow the engine to cool. Use an
ohmmeter to measure the resistance from pin P4-12 to
ground. The ohmmeter should indicate an open circuit.
Any other reading indicates a short; replace the HET
switch.
Low Oil Pressure (LOP) Switch
The normally closed LOP switch opens when the engine
oil pressure reaches the normal operating level and
closes if the oil pressure drops below a preset minimum.
Use an ohmmeter to check the continuity between pin
P4-13 and ground. Verify that the switch is closed while
the engine is stopped. Start the generator set and check
that the switch opens approximately 5 seconds later. If
the switch does not open after the engine reaches
normal operating speed, check the oil level and test for
leaks in the lubrication system before replacing the LOP
switch.