SR5 Electric Power Generation Caterpillar

Discrete Diode Test

Check the Bridge Diodes for the 1400 Frame and 1600 Frame Generator

Show/hide table

Illustration 1	g01327476

1. To perform this diode check, the diodes must be isolated. Refer to Illustration 1.
   Show/hide table

   Illustration 2	g01327478

2. Attach a battery and a light to each diode in both directions to test the diode. Refer to Illustration 2.

3. Replace the diodes that illuminate the light bulb when wired in both directions.

Check the Windings and Rotating Diodes by use of Separate Excitation

1. Stop the unit, disconnect, and isolate the CDVR wires.
   Show/hide table

   Illustration 3	g01327528

   Show/hide table

   Illustration 4	g01327530

2. There are two ways of creating an assembly with separate excitation. Assemble one of the following test circuits.

   Note: The voltage from a 12 V or a 24 V battery is too high regarding the required excitation voltage when running at rated engine speed. A rheostat must be used to adjust the required excitation current for the nominal voltage at no load. Refer to Illustration 3. Refer also to Illustration 4.

   As an alternative, a 12 V battery that is directly connected may be used if running the engine at low idle speed. Refer to "Dynamic" flashing.

   Both these systems should have characteristics which are compatible with the machine field excitation power. Refer to the nameplate.

3. Run the generator at the recommended speed that is used during normal operations.

4. Gradually increase the exciter field current by adjusting the rheostat and measure the output voltages on "L1- L2 - L3". Checking the excitation voltage and current at no load and on load. Refer to the machine nameplate or ask for the factory test report.

5. When the output voltage is at rated value and is balanced within 1% for the rated excitation level, the machine is in working order. The fault therefore comes from the CDVR or associated wiring (that is sensing or auxiliary windings).

Full Wave Rectifier and Rectifier/Varistor Rotating Heat Sink Assembly

Refer to the "Varistor - Test" section of this document for information about testing procedures.

1800 Generators Only

The full wave rectifier module including internal varistor and the external varistor module should be inspected and should be tested according to the following guidelines:

All leads, terminals, and connections should be inspected for damage and correct torque.

All test measurements should be documented to establish trending data.

Rectifier Diode Test

The following procedure tests each of the six diodes within the rectifier diode module. If any meter reading does not fall within the given ranges, replace the heat sink assembly. Refer to the "Removal/Installation" instructions.

Show/hide table

High voltage may be present. The power source must be disconnected before working on the equipment. Failure to disconnect the power source could result in injury or death. Verify that the equipment is not energized before performing any maintenance. This work must be performed by trained personnel with correct tools and procedures. Bodily contact with electrical potential will cause personal injury or death.

1. Remove all leads from the rectifier diode module.

2. Set the digital multimeter to the diode range.

3. Place the black test lead of the multimeter on the positive "+" rectifier diode module terminal.

4. Place the red test lead of the multimeter on each of the following rectifier diode module terminals. Begin with "AC1", then "AC2", and finally "AC3".

   Note: All the meter readings must be between 0.4 VDC and 1.0 VDC.

5. Place the red test lead on the negative "-" rectifier diode module terminal.

6. Place the black test lead of the multimeter on each of the following rectifier diode module terminals. Begin with "AC1", then "AC2", and finally "AC3".

   Note: All the meter readings should be between 0.4 VDC and 1.0 VDC.

7. Place the red test lead of the multimeter on the positive "+" rectifier diode module terminal.

8. Place the black test lead of the multimeter on each of the following rectifier diode module terminals. Begin with "AC1", then "AC2", and finally "AC3".

   Note: In all cases, the meter should read "OL"(overload).

9. Place the black test lead of the multimeter on the negative "-" rectifier diode module terminal.

10. Place the red test lead of the multimeter on each of the following rectifier diode module terminals. Begin with "AC1", then "AC2", and finally "AC3".

    Note: In all cases, the meter should read "OL" (overload).

    Note: A shorted diode can damage the exciter rotor. If a diode is shorted, then check the exciter rotor. Refer to the Testing and Adjusting, KENR5284, "Winding - Test" and the Testing and Adjusting, "Insulation - Test" sections for more testing information. Perform the tests that are shown in "KENR5284".

11. Install all the leads to the rectifier diode module. Torque the screws. The torque for the connections can range from 2.35 N·m (20.8 lb in) to 3.35 N·m (29.7 lb in).

Rotating Heat Sink Assembly Removal/Installation Instructions - 1800 Frame Generators Only

Use the following instructions to remove and to replace the rotating heat sink assembly. DO NOT attempt to replace any individual component on the rotating heat sink assembly.

1. Label the wires to ensure correct wiring upon installation.

2. Remove wires from terminals.

3. Remove mounting bolts.

4. Remove heat sink assembly.

5. Replace heat sink assembly.

6. Apply 9S-3263 Thread Lock to bolts. Install the bolts. Torque the bolts according to Table 1.

   Table

   Show/hide table

   Table 1

   Bolt Size	Torque
   5/16 inch	35.4 N·m (26 lb ft)
   3/8 inch	55.8 N·m (41 lb ft)

7. Inspect the exciter rotor lead insulation and the main rotor lead insulation for damage. Correct as necessary.

8. Install the exciter rotor leads and the main rotor leads on the rectifier diode module.

9. Install new star washers on the varistor module terminal posts. The star washer shall be placed between the terminal post and the lead terminal.

10. Install the leads to the varistor module.

11. Avoid introducing sharp bends in any lead or at any connection. Torque all the lead terminal connections according to Table 2.
    Show/hide table

    Table 2

    Terminal	Torque
    Terminal Torque Rectifier Diode Module	2.35 N·m (20.8) - 3.35 N·m (30 lb in)
    Varistor Module	1.4 N·m (12.3910 lb in) - 2 N·m (17.7 lb in)

12. Install new wire ties as necessary to secure all the lead wires.

13. Install all the sheet metal that was removed to gain access to rotating the heat sink assembly.

Rectifier Assembly Troubleshooting Checklist