Generac Power Systems 10 kW LP, 13 kW NG, 7 kW NG Test 11 Resistance Check Rotor Circuit 12-20 kW

Section 2.4

Diagnostic tests

Part 2

AC generators

2.Testing for a “grounded” condition: Any resistance reading indicated the winding is grounded.

3.Testing for a “shorted” condition: Any resistance reading indicated the winding is shorted.

4.If stator tests good and wire continuity tests good, refer back to flow chart.

Test 11 – Resistance Check Of

Rotor Circuit (12-20 kW)

DISCUSSION:

To verify the zero current draw reading and measure the rotor circuit.

PROCEDURE:

1.Disconnect Wire 4 and Wire 0 from the voltage regulator, located third and fourth terminals from the top of the voltage regulator.

2.Set VOM to measure resistance.

3.Connect one test lead to Wire 4. Connect the other test lead to a clean frame ground. Note the resistance reading. Compare to specifications in the front of this manual.

RESULTS:

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

2.If INFINITY or a high reading is measured on the VOM, refer back to flow chart.

Test 12 – Check Brushes And Slip

Rings (12-20 kW)

DISCUSSION:

The function of the brushes and slip rings is to provide for passage of excitation current from stationary compo- nents to the rotating rotor. Brushes are made of a spe- cial 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 electric- ity. 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.

PROCEDURE:

1.See Figure 8. Carefully inspect brush wires; make sure they are properly and securely connected.

2.Wire 0 from the negative (-) brush terminal connects to Wire 0 at the voltage regulator. Test this wire for an open condition. Remove Wire 0 from the brush assem- bly. Connect one meter test lead to Wire 0. Connect the other test lead to Wire 0 at the voltage regulator.

CONTINUITY should be measured. If INFINITY is measured repair or replace Wire 0 between the brush assembly and the voltage regulator.

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Figure 8. Checking Brushes and Slip Rings

3.Wire 4 from the positive (+) brush terminal connects to Wire 4 at the voltage regulator. 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 Wire 4 at the voltage regula- tor. CONTINUITY should be measured. If INFINITY is measured repair or replace Wire 4 between the brush assembly and the voltage regulator.

4.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 voltage regulator.

5.If CONTINUITY was measured in Steps 5 and 6 proceed to Step 9.

6.Disconnect Wire 0 and Wire 4 from the brush assembly. Remove the brush assembly from the bearing carrier. Inspect the brushes for excessive wear, or damage.

7.Inspect the rotor slip rings. If they appear dull or tarnished, they may be polished with fine sandpaper. DO NOT USE METALLIC GRIT TO POLISH SLIP RINGS.

8.If brush assembly and slip rings look good proceed to Test 13 (Test Rotor Assembly)

9.Wire 0 connects from the voltage regulator in the control panel ground lug. Connect one meter test lead to Wire 0 at the voltage regulator. 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 voltage regulator and the ground terminal.

10.Remove Wire 4 from the voltage regulator.

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