SRMP Electric Power Generation SRMP Generator Caterpillar

Illustration 1	g00613957
(1) Positive Rectifier Block (2) Negative Rectifier Block (3) Rectifier Terminal "AC1" (4) Rectifier Terminal "AC2" (5) Rectifier Terminal "AC3"

Note: Verify part number 9Y-0916 rectifier block date code as 0503 or greater. Refer to illustration 2. Rectifiers with a date code of 0503 and greater contain an internal varistor (CR7). Follow testing procedures with internal varistor (CR7).

Illustration 2	g01229622
(6) Date code

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Personal injury or death can result from improper troubleshooting and repair procedures. The following troubleshooting and repair procedures should only be performed by qualified personnel familiar with this equipment.

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Personal injury or death can result from high voltage. When power generation equipment must be in operation to make tests and/or adjustments, high voltage and current are present. Improper test equipment can fail and present a high voltage shock hazard to its user. Make sure the testing equipment is designed for and correctly operated for high voltage and current tests being made. When servicing or repairing electric power generation equipment: Make sure the unit is off-line (disconnected from utility and/or other generators power service), and either locked out or tagged DO NOT OPERATE. Make sure the generator engine is stopped. Make sure all batteries are disconnected. Make sure all capacitors are discharged.

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Shut off engine and remove key before performing maintenance or repair work. Failure to do so may result in personal injury due to inadvertant machine operation. Do not start the engine or move any of the controls if there is a “Do Not Operate” or similar warning tag attached to the start switch or controls.

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Do not connect generator to a utility electrical distribution system unless it is isolated from the system. Electrical feedback into the distribution system can occur and could cause personal injury or death. Open and secure main distribution system switch, or if the connection is permanent, install a double throw transfer switch to prevent electrical feedback. Some generators are specifically approved by a utility to run in parallel with the distribution system and isolation may not be required. Always check with your utility as to the applicable circumstances.

Procedure - Rectifier

The following procedure tests all six diodes within the block. If any meter reading does not fall within the given ranges, replace the rectifier block .

1. Set the digital multimeter on the diode range. Remove all leads from the rectifier block.

2. Place the black test lead on the positive "+" rectifier terminal. Place the red test lead on the following rectifier terminals: "AC1" (3), "AC2" (4) and "AC3" (5). All readings on the meter should be between 0.4 and 1.0.

3. Place the red test lead on the negative "-" rectifier terminal. Place the black test lead on the following rectifier terminals: "AC1" (3), "AC2" (4) and "AC3" (5). All readings on the meter should be between 0.4 and 1.0.

4. Place the red test lead on the positive "+" rectifier terminal. Place the black test lead on the following rectifier terminals: "AC1" (3), "AC2" (4) and "AC3" (5). In all cases, the meter should read "OL" (overload).

5. Place the black test lead on the negative "-" rectifier terminal. Place the red test lead on the following rectifier terminals: "AC1" (3), "AC2" (4) and "AC3" (5). In all cases, the meter should read "OL" (overload).

   Note: A shorted diode can damage the exciter rotor. If a diode is shorted, check the exciter rotor. Refer to the Testing and Adjusting, "Winding - Test" and Testing and Adjusting, "Insulation - Test". Perform these tests.

   Note: For a failed rectifier block, refer to the "Diode Block Troubleshooting Guide", Table 2. The "Diode Block Troubleshooting Guide" consists of a list of items to consider when troubleshooting a failed diode block and/or external varistor (CR7). The purpose of this list is to find a cause for the diode block and/or varistor (CR7) failure which may be external to the exciter system. The purpose of this list is NOT to troubleshoot "no voltage output" from the generator.

6. Install leads.

   • Terminal connections - 2.35 N·m (20.8 lb in) to 3.36 N·m (29.7 lb in)

   • 9Y-0916 Rectifier Assembly (mounting to heatsink) - 4.07 N·m (36 lb in) to 5.54 N·m (49 lb in)

Procedure - Internal Varistor (CR7)

Note: Verify rectifier block date code as 0503 or greater. Refer to illustration 2. Rectifiers with a date code of 0503 and greater contain an internal varistor (CR7).

The following procedure tests the ability of the normal state of the varistor (CR7). If any meter reading does not fall within the given ranges, replace the rectifier block.

1. Remove all leads from the rectifier block.

2. Place the megohmmeter test leads on the rectifier block as follows:

   • Place the BLACK test lead on the negative "-" terminal.

   • Place the RED test lead on the positive "+" terminal.

   Note: The rectifier block is polarity sensitive. Damage to equipment may result in reverse polarity testing.

3. If the megohmmeter is not capable of reading DC voltage, hook up a 1000 VDC voltmeter across the negative and positive terminals.

4. On the megohmmeter, select and apply 1000 VDC to the varistor (CR7).

   Note: Do not apply voltage to the varistor (CR7) for greater than 3 seconds.

5. Megohmmeter readings should be between 450 VDC and 600 VDC.

   • If the readings are greater than 600 VDC, the varistor (CR7) is OPEN.

   • If the readings are less than 450 VDC, the varistor (CR7) is SHORTED or DEGRADED.

   Note: Do not over torque. Applying torques greater than the listed torques may cause damage to the components.

6. Install leads. Apply the following torques.

• Terminal connections - 2.35 N·m (20.8 lb in) to 3.36 N·m (29.7 lb in)

Note: If the varistor (CR7) is found to be defective, the varistor (CR7) most likely failed due to a transient voltage surge on the main rotor winding. Varistor failure is not usually a component failure. Root causes of varistor (CR7) failure include:

• Incorrect paralleling or loss of synchronism

• Reverse VAR or reverse power event

• Loss of main rotor field due to voltage regulator failure, diode rectifier failure, or other events

• High ambient temperature (or other application error)

• Large sudden load application

3-Diode Rectifier Block

Illustration 3	g00610240
3-Diode Rectifier Block (two pieces)

Illustration 4	g00613971
3-Diode Rectifier Block (two pieces)

The following procedure tests all three diodes within a block. Check the positive rectifier block and the negative rectifier block. If any meter reading does not fall within the given ranges, replace the rectifier block.

1. Set the digital multimeter on the diode range. Remove all leads from the rectifier block.

2. To test the negative rectifier block, follow these steps:

   1. Place the red test lead on the negative "-" terminal. Place the black test lead on the following rectifier terminals: "AC1" (3), "AC2" (4) and "AC3" (5). All readings on the meter should be between 0.4 and 1.0.

   2. Place the black test lead on the negative "-" terminal. Place the red test lead on the following rectifier terminals: "AC1" (3), "AC2" (4) and "AC3" (5). In all cases, the meter should read "OL" (overload).

3. To test the positive rectifier block, follow these steps:

   1. Place the red test lead on the positive "+" rectifier terminal. Place the black test lead on the following rectifier terminals: "AC1" (3), "AC2" (4) and "AC3" (5). In all cases, the meter should read "OL" (overload).

   2. Place the black test lead on the positive "+" rectifier terminal. Place the red test lead on the following rectifier terminals: "AC1" (3), "AC2" (4) and "AC3" (5). All readings on the meter should be between 0.4 and 1.0.

Note: A shorted diode can damage the exciter rotor. If a diode is shorted, check the exciter rotor. Refer to the Testing and Adjusting, "Winding - Test" and Testing and Adjusting, "Insulation - Test". Perform these tests.

Note: For a failed rectifier block, refer to the "Diode Block Troubleshooting Guide", Table 2. The "Diode Block Troubleshooting Guide" consists of a list of items to consider when troubleshooting a failed diode block and/or external varistor (CR7). The purpose of this list is to find a cause for the diode block and/or varistor (CR7) failure which may be external to the exciter system. The purpose of this list is NOT to troubleshoot "no voltage output" from the generator.

Note: This configuration contains an externally mounted varistor (CR7) block. Refer to Testing and Adjusting, "Varistor - Test" section of this document. Perform the tests in the "Diode Block Troubleshooting Guide".