Guardian Technologies 4456 TEST 9 - CHECK BRUSHES AND SLIP RINGS, Section, Part, Diagnostic Tests

AC GENERATORS

PART 2

SECTION 2.4

DIAGNOSTIC TESTS

RESULTS:

1.If the resistance reading is correct, check your VOM meters fuse and repeat Test 4.

2.If INFINITY is measured on your VOM meter, go to Test 9.

TEST 9 - CHECK BRUSHES

AND SLIP RINGS

DISCUSSION:

The function of the brushes and slip rings is to provide for passage of excitation current from stationary components to the rotating rotor. Brushes are made of a special long lasting material and seldom wear out or fail. However, slip rings can develop a tarnish or film that can inhibit or offer a resistance to the flow of electricity. Such a non-conducting film usually develops during non-operating periods. Broken or disconnected wiring can also cause loss of excitation current to the rotor.

Figure 7. Checking Brushes and Slip Rings

PROCEDURE:

1.Disconnect connector C2 (deutsch connector closest to the back panel). Refer to figure 5 and figure 6 on page 2.4-5.

2.Set a VOM to measure resistance.

3.Connect one meter test lead to Pin 9 (Wire 0) of the C2 connector (female side). Connect the other meter test lead to Pin 10 (Wire 4) of the C2 connector (female side). Rotor resistance should be measured see specifications on page 2. If rotor resistance is not measured proceed to step 4. If rotor resistance is measured proceed to step 12.

4.See figure 7. Carefully inspect brush wires; make sure they are properly and securely connected.

5.Wire 0 from the negative (-) brush terminal connects to Pin 9 of the C2 connector.

Test this wire for an open condition. Remove wire 0 from the brush assembly. Connect one meter test lead to wire 0. Connect the other test lead to Pin 9 (wire 0) of the C2 connector ( female side). CONTINUITY should be measured. If INFINITY is measured repair or replace wire 0 between the brush assembly and the C2 connector.

6.Wire 4 from the positive (+) brush terminal connects to Pin 10 of the C2 connector.Test this wire for an open condition. Remove wire 4 from the brush assembly. Connect one meter test lead to Wire 4. Connect the other meter test lead to Pin 10 (wire 0) of the C2 connector (female side). CONTINUITY should be measured. If INFINITY is measured repair or replace wire 4 between the brush assembly and the C2 connector.

7.Connect one meter test lead to wire 4 Connect the other meter test lead to frame ground. INFINITY should be measured. If CONTINUITY is measured a short to ground exists on wire 4 repair or replace wire 4 between the brush assembly and the C2 connector.

8.If continuity was measured in steps 5 and 6 proceed to step 9.

9.Disconnect wires 0 and 4 from the brush assembly. Remove the brush assembly from the bearing carrier. Inspect the brushes for excessive wear,damage.

10.Inspect the rotor slip rings. If they appear dull or tarnished, they may be polished with a fine sandpaper.

DO NOT USE METALLIC GRIT TO POLISH SLIP RINGS.

11.If brush assembly and slip rings look good proceed to Test 10 ( Test Rotor assembly)

12.Wire 0 connects from the C2 connector to the control panel ground lug. Connect one meter test lead to Pin 9 (Wire 0) of the C2 connector (male side). Connect the other meter test lead to the ground terminal in the control panel. CONTINUITY should be measured. If INFINITY is measured repair or replace wire 0 between the C2 connector and the ground terminal.

13.Remove wire 4 from the voltage regulator.

Page 2.4-7