TP-6079 3/0020 Section 5 Generator Troubleshooting
5.4 Stator
The stator consists of a series of coils of wire laid in a
laminated steel frame. The stator leads supply voltage
to the AC load and exciter regulator. See Figure 5-7 for
coil lead description.
Stator Leads Description
1--2 Output coil
3--4 Output coil
33--44 Control wires from 3 and 4
55--33 Voltage regulator power source
B1--B2 Controller power source
Figure 5-7 Stator Coil Lead Description
Before testing the stator, inspect it for heat discoloration
and visible damage to the exposed coil windings and
varnished areas of the frame laminations. Be sure the
stator is securely fastened in the stator housing.
The stator produces electrical output (AC) as the
magnetized main field rotates within the stator windings.
Test the condition of the stator according to the following
procedure.
Leads 1, 2, 3, and 4 are the generator output leads.
Leads 33, 44, and 55 are the voltage regulator supply
and sensing leads. The output of leads B1 and B2 is the
control voltage for the controller.
Stator Test Procedure:
1. Place the generator start/stop switch in the STOP
position.
2. Disconnect the generator set engine starting
battery, negative (--) lead first.
3. Check the generator output lead connections. See
Section 8, Reconnection and Wiring Diagrams.
4. Disconnect all of the stator leads to isolate the
windings. To check the stator continuity, set the
ohmmeter on the R x 1 scale. Check the stator
continuity by connecting the meter leads to the
stator leads as shown in Figure 5-8. Perform the
stator tests on all of the stator windings.
Note: When taking an ohmmeter reading using
lead 55, make the connection prior to the
in-line fuse.
5. Check the cold resistance of the stator windings by
connecting the meter leads to the stator leads 1-4,
2-5, 3-6, etc. See Section 1, Specifications, for the
stator resistance values.
6. Perform a megohmmeter test on the stator as
described in step 7.
Note: Consider the stator functional if the
resistance reading (continuity) is low and
there is no evidence of shorted windings
(heat discoloration).
Note: The stator resistance varies directly with
increased temperature.
If the stator readings vary considerably during the
previous checks, repair or replace the stator.
7. Check the stator for a grounded condition using a
megohmmeter. Apply 500 volts DC to any stator
lead from each winding and the stator frame.
Follow the instructions of the megohmmeter
manufacturer when performing this test. Repeat
the test on the other leads until all of the stator
windings have been tested. A reading of
approximately 1.5 megohms and higher indicates
the stator is functional. A reading of less than
approximately 1.5 megohms indicates
deterioration of the winding insulation and possible
current flow to ground; if so, replace the stator.
Between Leads Continuity
1 and 2 Yes
3 and 4 Yes
55 and 66 Yes
B1 and B2 Yes
1 and 3, 4, 33, 44, 55 No
1 and 55, B1 and B2 No
4 and B1 and B2 No
55 and B1 and B2 No
Any stator lead and ground No
Figure 5-8 Stator Continuity
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