Generac Power Systems 55, 75, 65 TEST 9- CHECK BRUSH LEADS, TEST 10 - CHECK BRUSHES & SLIP RINGS

Section 7

DIAGNOSTIC TESTS

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.

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