- 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:
- YES - There are no loose terminals or corroded terminals. The connections are correct. Proceed to test step 2.
- NO - 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
- If attached, disconnect any PF/VAR controller from the VR6 voltage regulator. Place a jumper across terminals 2 and 3 of the VR6 voltage regulator.
- 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 and 22 at the regulator. Also take voltage readings on terminal 24 if 3 phase sensing is used.
Expected Result:
Meters are accurate.
Results:
- YES - Meter readings are accurate. Proceed to test step 3.
- NO - The meter 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 CONNECTIONS OF THE VOLTAGE ADJUST POTENTIOMETER
- Turn off the genset.
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The Cat VR6 presents an electrical shock/electrocution hazard. This hazard will cause serious injury or death.
Service by trained personnel only.
The terminals and heat sinks are live at hazardous voltages when power is applied and for up to 8 minutes after power is removed.
- Check if there is the jumper between terminals 4 and 7.
Expected Result:
There is a jumper that is placed between terminals 4 and 7.
Results:
- YES - If a remote voltage adjust potentiometer is NOT used, the jumper is properly installed. Proceed to test step 5.
- YES - If a remote voltage adjust potentiometer is used, the jumper should be removed from terminals 4 and 7. In this case, the remote voltage adjust potentiometer should be connected to terminals 6A and 7. Proceed to test step 4.
- NO - There is no jumper between terminals 4 and 7. The regulator may go into the overexcitation shutoff.
Repair: Verify the wiring schematics. Install the jumper in accordance with the wiring schematic.
STOP
Test Step 4. CHECK THE RESISTANCE OF THE REMOTE VOLTAGE ADJUST POTENTIOMETER
- Disconnect the wires from terminals 6A and 7.
- Measure the resistance of the remote voltage adjust potentiometer while the potentiometer is being adjusted over the operating range.
Expected Result:
The resistance should be between 0 K Ohm and 10 ± 0.5 K Ohm.
Results:
- YES - The resistance increases smoothly within the specified range. Proceed to test step 5.
- NO - The resistance is not within the specified value. The resistance jumps to a high value when the potentiometer is adjusted.
Repair: Replace the remote voltage adjust potentiometer.
STOP
Test Step 5. CHECK THE SENSING CONNECTIONS
- Check if there is a jumper between terminals 6A and 9.
Note: If you are using three-phase sensing, terminals 6A and 9 should be jumpered. If you are using single-phase sensing, this jumper should be removed.
Expected Result:
The jumper is installed or the jumper is not installed, based on the phase sensing selection.
Results:
- YES - The jumper is installed between terminals 6A and 9 for three-phase sensing. The jumper is not installed between terminals 6A and 9 for single-phase sensing. Proceed to test step 6.
- NO - The jumper is not installed between terminals 6A and 9 for three-phase sensing. The jumper is installed between terminals 6A and 9 for single-phase sensing.
Repair: Connect the jumper in accordance with the phase sensing selection.
STOP
Test Step 6. CHECK CONNECTIONS FOR THE DROOP CURRENT TRANSFORMER (CT)
- Stop the genset.
- For a 1 A CT, verify that the connections are to terminals 5 and 6.
- For a 5 A CT, verify that the connections are to terminals 5A and 6.
Note: For troubleshooting purposes, the voltage regulator can be operated when the droop CT is disconnected. However, the droop CT secondary wires must be connected together.
- Verify that the polarity connection of the droop CT is connected to terminal 6.
Expected Result:
The connections are correct.
Results:
- YES - The connections are correct. Proceed to test step 7.
- NO - The connections are not correct or the connections are impossible to verify.
Repair: Run an individual genset with a reactive load. If the voltage increases as the reactive load increases, the CT secondary is not connected properly. Stop the genset and reverse the lead connections.
STOP
Test Step 7. VERIFY THE SENSING VOLTAGE
- Make sure that the generator set is off.
- If the generator uses Power Transformers (PT) to step down the generator output voltage to the sensing voltage, check the sensing voltage range. The sensing voltage range should lie between the following limits:
- 180 VAC to 280 VAC on 50/60 Hz gensets
- Verify that sensing wires 20 and 22 are connected correctly. If three phase sensing is used, verify that sensing wire 24 is connected correctly. Wire 20 should be connected to T3 phase. Wire 22 should be connected to T1 phase. Wire 24 should be connected to T2 phase.
Expected Result:
The sensing voltage is correct. The sensing wires are connected properly.
Results:
- YES - The sensing voltage is correct. The connections are correct. Proceed to test step 8.
- NO - The sensing voltage is NOT correct and/or the sensing wires are NOT connected properly.
Repair: Install a PT with correct ratios. Connect the sensing wires to correct terminals.
STOP
Test Step 8. CHECK THE OUTPUT VOLTAGE
- Start the genset.
- Run the genset at no load.
- Read the output voltage from the control panel.
Expected Result:
The generator voltage is higher than the nominal voltage. The generator voltage is steady.
Results:
- YES - The generator voltage is still high but steady. Proceed to test step 9.
- NO - The generator voltage oscillates. The voltage goes high. Then, the voltage goes low.
Repair: Add load to the genset. If the voltage still oscillates, turn off the genset in order to reset the voltage regulator. Start the genset again and run at no load. Add load to the generator. If the voltage oscillates again, go to the Troubleshooting, "Voltage Regulator". If the voltage is no longer high, the problem has been fixed.
STOP
Test Step 9. CHECK THE OPERATING FREQUENCY OF THE GENSET
- Measure the generator frequency. Use the frequency meter on the control panel or a multimeter with frequency measuring function.
Expected Result:
The generator frequency is above 5% of the rated frequency.
Results:
- YES - The frequency is above the rated frequency. In this case, the voltage will be higher than the rated voltage.
Repair: Adjust the generator frequency. Reset the knee frequency. Refer to the Testing and Adjusting, "Knee Frequency - Adjust".
STOP
- NO - The generator frequency is same as the rated frequency. The high voltage problem still exists. Proceed to test step 10.
Test Step 10. 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 180 VAC and 280 VAC for 50 to 60 Hz operation.
Results:
- YES - If the voltage regulator performs the adjustment to operating voltage range and the high voltage problem has not been eliminated, troubleshoot the attachments. Refer to the appropriate section within the "Troubleshooting" section.
STOP
- NO - 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". If necessary, replace the voltage regulator.
STOP