Check Brush Leads; Test; Check Brushes & Slip Rings - Guardian Quietpact 55 Repair Manual

9. Connect the meter test leads across Stator lead 11P and frame
ground. "Infinity" should be read.
10. Connect the meter test leads across Stator lead 33 and frame
ground. The reading should be "Infinity".
11. Connect the meter test leads across Stator leads Wire 11P
and Wire 33. The reading should be "Infinity".
12. Connect the meter test leads across Stator leads Wire 11P
and Wire 66. The reading should be "Infinity".
13. Connect the meter test leads across Stator leads Wire 33 and
Wire 66. The reading should be "Infinity".
14. Connect the meter test leads across Stator leads Wire 11P
and Wire 2. The reading should be "Infinity".
15. Connect the meter test leads across Stator leads Wire 33 and
Wire 2. The reading should be "Infinity".
RESULTS:
1. If the Stator passes all steps except Step 7, repair, re-connect
or replace Sensing leads 11S and 22S.
2. Replace the Stator if it's power windings fail the test. (Note
Result No. 1).
3. If the Power Windings test good, perform the "Insulation
Resistance Test" on Page 13.
Figure 7-6. – Stator Power Winding Leads
TEST 9- CHECK BRUSH LEADS
DISCUSSION:
In Test 4, if application of battery voltage to the Rotor
did NOT result in an output of about one-half rated
voltage, the brush leads could be one possible cause
of the problem. This test will check Wires 4 and OK
for an open circuit condition.
PROCEDURE:
1. Set a VOM to its "Rx1" scale and zero the meter.
2. Disconnect Wire 4 from the Voltage Regulator and from the
Rotor brush terminal.
3. Connect the VOM test leads across each end of the wire. The
meter should read "Continuity".
4. Disconnect Wire OF from the Rotor Brush Terminal. Connect
one meter test lead to Wire OF. Connect the other test lead to
a clean frame ground. The meter should read "Continuity".
RESULTS:
1. Repair, reconnect or replace any defective wire(s).
2. If wires check good, go to Test 10.
Figure 7-7. – Brush Leads
TEST 10 - CHECK BRUSHES & SLIP RINGS
DISCUSSION:
Brushes and slip rings are made of special materials
that will provide hundreds of hours of service with little
wear. However, when the generator has been idle for
some time, an oxide film can develop on the slip
rings. This film acts as an insulator and impedes the
flow of excitation current to the Rotor.
If Test 4 resulted in less than one-half rated output
voltage, it is possible that the brushes and slip rings
are at fault.
PROCEDURE:
1. Gain access to the brushes and slip rings.
2. Remove Wire 4 from the positive (+) brush terminal.
3. Remove the ground wire (0F) from the negative (-) brush.
4. Remove the brush holder, with brushes.
5. Inspect the brushes for excessive wear, damage, cracks, chip-
ping, etc.
6. Inspect the brush holder, replace if damaged.
S S e e c c t t i i o o n n 7 7
D D I I A A G G N N O O S S T T I I C C T T E E S S T T S S
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