- Turn off the genset.
- Check for loose terminals.
- Check for corroded terminals.
- Check for proper connections between the voltage regulator and the generator.
Expected Result:
All initial checks show no problems.
Results:
- OK - There are no loose terminals or corroded terminals. The connections are correct. Proceed to test step 2.
- Not OK - One or more of initial checks shows a problem.
Repair: Tighten loose terminals. Replace corroded terminals. If the connections are incorrect, connect the wiring properly according to the wiring diagram.
Stop.
Test Step 2. CHECK METERS
- Start the genset.
- Run the genset at no load.
- Ensure the accuracy of the voltmeter. If you are reading the voltage from the control panel, check that voltage with a multimeter.
Note: Take the voltage readings on terminals 20, 22 and 24 at the regulator.
Note: The step-down ratio of the potential transformers must be taken into consideration when these voltages are measured. The voltage that is measured will be different from the value on the meter. Multiply the measured value by the step-down ratio of the transformer. This value should be equal to the value that is shown on the meter.
Expected Result:
Meters are accurate.
Results:
- OK - Meters' readings are accurate. Proceed to test step 2.
- Not OK - The meters' readings do not match.
Repair: Troubleshoot the metering circuit. Verify the schematic for the metering circuit. Verify whether the meters are connected correctly.
Stop.
Test Step 3. CHECK ENGINE RPM
- Start the genset.
- Run the genset at no load.
- Monitor the engine speed.
Expected Result:
Engine speed is stable.
Results:
- OK - Engine speed is stable. Proceed to test step 4.
- Not OK - When the engine speed is unstable, the frequency will be also unstable. The unstable frequency causes the voltage to become unstable as well.
Repair: Troubleshoot the engine RPM. Refer to the appropriate engine service manual.
Stop.
Test Step 4. VERIFY THE STABILITY ADJUSTMENT SETTING
- Readjust the stability adjustment. Refer to the Testing and Adjusting, "Stability - Adjust".
Expected Result:
Voltage has stabilized.
Results:
- OK - The voltage is stable. Add the load to the generator. If the voltage remains stable, the problem has been resolved. Otherwise, proceed to test step 5.
- Not OK - Voltage is still unstable.
Repair: Check the voltage regulator.
Proceed to test step 6.
Test Step 5. CHECK HARMONICS
- Check the harmonic distortion. Use either an oscilloscope or a harmonic analyzer.
 |
Dangerous voltages are present at both the generator and the system bus. Under no circumstances should any attempt be made to connect instrumentation to these points until you are certain all power is off. All instruments must be connected to the generator and the system bus through potential transformers, which provide a maximum of 600 volts to the instruments. Failure to follow instructions will result in death or serious injury. |
Expected Result:
The distortion in load is above 20% or severe notching is present.
Results:
- OK - There is a harmonic distortion in load. Consult your Caterpillar dealer in order to reduce harmonic distortion. Stop.
- Not OK - There is no harmonic distortion in the load.
Repair: Check if there is a harmonic noise in the circuit from the attachments, which can cause voltage to become unstable. Disconnect the attachments one at a time in order to isolate the problem.
If the problem has not been resolved, proceed to test step 6.
Test Step 6. CHECK THE REGULATOR
- Adjust the operating voltage range by using the voltage adjustment. Refer to the Testing and Adjusting, "Voltage - Adjust".
Expected Result:
The voltage should be adjustable between 90 and 140 V.
Results:
- OK - If the voltage regulator performs the adjustment to operating voltage and the problem has not been eliminated, troubleshoot the attachments. Refer to the appropriate section within the Troubleshooting Section. Stop.
- Not OK - The regulator does not perform the adjustment to operating voltage, as described above.
Repair: Check the generator diodes. Refer to the appropriate Operations and Maintenance Manual for the particular generator. If the problem has not been eliminated, test the voltage regulator. Refer to the Testing and Adjusting, "Voltage Regulator - Test". Replace the voltage regulator, if necessary.
Stop.