C27 Generator Set Caterpillar

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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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DANGER: Shock/Electrocution Hazard-Do not operate this equipment or work on this equipment unless you have read and understand the instructions and warnings in the Operation and Maintenance Manual. Failure to follow the instructions or heed the warnings will result in serious injury or death.

The generator set functional test is a simplified test that can be performed in order to determine if the generator is functional. The generator set functional test should be performed on a generator set that is under load.

The generator set functional test determines if the following statements happen:

• A phase voltage is being generated.

• The phase voltages are balanced.

• The phase voltages change relative to engine speed.

The generator set functional test consists of the following steps:

1. Stop the generator. Connect the potential transformer's high voltage winding to the generator terminals (T1) and (T2). Connect the voltmeter to the low voltage winding. If two transformers are available, connect the high voltage winding of the second transformer to the generator terminals (T1) and (T3). Connect the secondary terminals that correspond to generator terminal (T2) of both transformers together.

2. Disconnect wires "F1+" and "F2-" from the voltage regulator. Disconnect the generator from the load.

3. Connect a 12 VDC automotive battery to wires "F1+" and "F2-".
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   NOTICE
   Do not operate the generator set at a speed that is higher than one-half of the rated speed. Higher speeds under these test conditions can cause damage to the system.

4. Operate the generator set at idle.

5. Measure the AC voltage across the low voltage terminals of the transformer that correspond to the following generator terminals: "T1" and "T2", "T2" and "T3" and "T3" and "T1". Record the voltages.

6. Monitor the voltage between any two of the locations in step 5. Decrease the generator set speed by 10 percent. Increase the generator set speed by 10 percent.

7. The voltages that were measured in Step 5 should be nearly equal. These voltages should measure a minimum of 85 VAC.

8. When the generator set speed is decreased by 10 percent, the voltages that were measured in Step 6 should decrease by 10 percent. When the generator set speed is increased by 10 percent, the voltages that were measured in Step 6 should increase by 10 percent.