TEST 7 – TEST BRUSHLESS DPE WINDING
DISCUSSION:
A DPE or Displaced Phase Excitation winding is used
to charge a capacitor, which discharges and charges,
releasing a voltage that is induced into the rotor. If
the DPE winding fails, only residual magnetism of the
rotor will be measured at the Main Breaker.
Note: The resistance of stator windings is very
low. Some meters will not read such a low resis-
tance, and will simply indicate CONTINUITY.
Recommended is a high quality, digital type meter
capable of reading very low resistances.
*
Danger: The capacitor may need to be dis-
charged before testing. A capacitor can be
discharged by crossing the terminals with
a metal insulated screw driver.
PROCEDURE:
1. Disconnect Wire 2 and Wire 6 from the capacitor.
2. Set VOM to measure resistance.
3. Connect one meter lead to Wire 2 and connect the other
meter lead to Wire 6.
a. Reading should be approximately 0.97 and 1.13
Ohms.
4. Connect one meter lead to Wire 2 and connect the other
meter lead to a clean frame ground, INFINITY should be
measured.
5. Isolate the stator wire so that the stator is disconnected
from the receptacle panel and the capacitor.
Note: Isolate all main stator leads before proceeding.
6. Connect one meter lead to Wire 2 and connect the other
meter lead to Wire 11. INFINITY should be measured.
7. Repeat Step 6 using Wire 2 and Wire 44.INFINITY
should be measured.
RESULTS:
1. Stator winding resistance values is a test of winding conti-
nuity and resistance. If a very high resistance or INFINITY
is indicated, the winding is open or partially open.
2. Testing for a “grounded” condition: Any resistance read-
ing indicates that the winding is grounded.
3. Testing for a “shorted” condition: Any resistance reading
indicates that the winding is shorted.
4. If stator tests good and wire continuity tests good, refer
back to flow chart.
TEST 8 – TEST BRUSHLESS STATOR WINDINGS
DISCUSSION:
The brushless stator has three internal windings,
two main power windings and a DPE winding. This
test will ensure that there are no shorts between the
power windings or shorts to ground.
A VOM meter can be used to test the stator windings
for the following faults:
• Anopencircuitcondition
• A“short-to-ground”condition
• Ashortcircuitbetweenwindings
Note: The resistance of stator windings is very
low. Some meters will not read such a low resis-
tance, and will simply indicate CONTINUITY.
Recommended is a high quality, digital type meter
capable of reading very low resistances.
Note: Refer to Figure 4 in Section 1.3 for illustra-
tion of Stator Configuration “A”. Some wire num-
bers will not be marked on the stator.
PROCEDURE:
1. Disconnect Wires 11, 22, 33, 44 from the receptacle
panel so that the stator is isolated.
2. Make sure all of the disconnected leads are isolated
from each other and are not touching the frame during
the test.
3. Set a VOM to measure resistance.
4. Connect one test lead to Stator Lead 11. Connect the
other test lead to Stator Lead 22. Stator resistance
should be between 0.12-0.14 Ohms.
5. Connect one test lead to Stator Lead 33. Connect the
other test lead to Stator Lead 44. Stator resistance
should be between 0.12-0.14 Ohms.
TEST WINDINGS FOR A SHORT TO GROUND:
1. Make sure all leads are isolated from each other and are
not touching the frame.
2. Connect one test lead to a clean frame ground. Connect
the other test lead to Stator Lead Wire 11.
a. The meter should read INFINITY.
b. Any reading other than INFINITY indicates a
“short to ground” condition.
3. Repeat Step 2 using Stator Lead 44
TEST FOR A SHORT CIRCUIT BETWEEN WINDINGS:
1. Connect one test lead to Stator Lead 11. Connect the
other test lead to Stator Lead 33.
a. The meter should read INFINITY.
b. Any reading other that INFINITY indicates a
short between windings.
Page 30
PART 2
AC GENERATORS
SECTION 2.3
AC DIAGNOSTIC TESTS
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