Test 6 - Check Capacitor; Test 7 - Test Brushless Dpe Windings - Generac Power Systems XT-EFI Series Manual

Test 6 – Check Capacitor
General Theory
The brushless rotor system relies on the charging and
discharging of a capacitor to induce voltage into the rotor.
The capacitor also maintains voltage once 240 VAC is
achieved. If the capacitor fails, only residual magnetism
of the rotor will be measured at the main breaker.
NOTE: The voltage of a brushless capacitive discharge
generator will start low and increase as load is applied.
IMPORTANT NOTE: The capacitor may need to be
discharged before testing. A capacitor can be discharged by
crossing the terminals with a metal insulated screw driver.
IMPORTANT NOTE: Use proper protective equipment
when dealing with a capacitor that has exploded.
Procedure
Consult the owner's manual of the meter being
1.
used for directions on measuring capacitance.
Figure 3-8 shows a typical meter and how to check
capacitance.
Connect meter leads directly across the terminals
2.
of capacitor. The rated µf (micro farad) of the
capacitor is marked on the side of the canister.
The meter should display the correct µf reading ±
3.
5µf. If anything other than the indicated rating is
displayed, replace the capacitor.
Figure 3-8. Capacitor Test Points (Alternator
Configuration "A")
Results
Refer to Troubleshooting
1.
Visually observe the capacitor. A capacitor is
2.
defective if:
• terminal connections are loose on the canister.
• capacitor wobbles while sitting on a flat surface.
If any of these traits are observed, replace capacitor.
Diagnostic Repair Manual
μf
59.0
004978
Flowcharts.
IMPORTANT NOTE: A capacitor that has gone bad has
a tendency to explode. Use caution when dealing with an
exploded capacitor. The gel from inside a capacitor can
cause skin irritation.
Test 7 – Test Brushless DPE Windings
General Theory
A Displaced Phase Excitation (DPE) winding is used to
charge a capacitor. It 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 resistance, and will
simply indicate CONTINUITY. Recommended is a high
quality, digital type meter capable of reading very low
resistances.
IMPORTANT NOTE: The capacitor may need to be
discharged before testing. A capacitor can be discharged by
crossing the terminals with a metal insulated screw driver.
Procedure
Disconnect Wire 2 and Wire 6 from capacitor.
1.
Set DMM to measure resistance.
2.
Connect one meter lead to Wire 2 and connect the
3.
other meter lead to Wire 6.
a. Reading should be approximately 0.97 and
1.13 Ohms.
Connect one meter lead to Wire 2 and connect the
4.
other meter lead to a clean frame ground,
INFINITY should be measured.
Isolate the stator wire so the stator is disconnected
5.
from the receptacle panel and the capacitor.
NOTE: Isolate all main stator leads before proceeding.
Connect one meter lead to Wire 2 and connect the
6.
other meter lead to Wire 11. INFINITY should be
measured.
Repeat Step 6 using Wire 2 and Wire 44. INFINITY
7.
should be measured.
Results
If INFINITY or a very high resistance is indicated,
1.
the winding is open or partially open.
Test for a "grounded" condition: Any resistance
2.
reading indicates the winding is grounded.
Test for a "shorted" condition: Any resistance
3.
reading indicates the winding is shorted.
If stator tests good and wire continuity tests good,
4.
refer to flow chart.
Section 1 AC Diagnostic Tests
13