VR6 Voltage Regulator Caterpillar

Low Voltage

Usage:

Test Step 1. PERFORM THE INITIAL CHECK

Shut down the generator set. Remove all power to the generator set.

Note: If the low voltage condition has been caused by the regulator over-excitation shutdown protection feature, removing regulator power will reset the over excitation protection feature.

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Illustration 1	g01021519

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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 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 CONNECTIONS FOR THE VAR/PF CONTROLLER

If the VAR/PF controller is used, verify whether there is no jumper between terminals 2 and 3.
If the VAR/PF controller is not used, place the jumper between terminals 2 and 3.

Expected Result:

The jumper has been placed accordingly.

Results:

YES - The jumper is installed when the VAR/PF controller is not used. There is no jumper between terminals 2 and 3 when the VAR/PF controller is used. Proceed to test step 3.
NO - The connections are not correct.
Repair: Place the jumper according to the wiring schematic.

STOP

Test Step 3. 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.

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Illustration 2	g01021519

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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.

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 4.
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 4. CHECK CONNECTIONS OF THE VOLTAGE ADJUST POTENTIOMETER

Turn off the genset.

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Illustration 3	g01021519

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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 6.
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 5.
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 5. CHECK THE RESISTANCE OF THE REMOTE VOLTAGE ADJUST POTENTIOMETER

Disconnect, float, and isolate the connecting wires from the VR6 voltage regulator terminals 6A and 7.
Measure the resistance of the remote voltage adjust circuit. Measure the resistance at the wire ends.

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 6.
NO - The resistance is not within the specified value of above zero ohms to 10K ohms. The resistance jumps to a high value when the potentiometer is adjusted or reads zero or infinity ohms.
Repair: If the value is erratic, replace the remote voltage adjust potentiometer. Inspect all of the wiring and wiring terminations, including the solder joints that are at the remote voltage adjust potentiometer terminals. Look for wires that may have become pinched or that have damaged wire insulation. Pinched or damaged wire insulation may create an open or short circuit. Replace the wiring and reheat any solder joints as necessary. Use care to avoid excessive heat exposure to the potentiometer terminals when soldering the connecting wires to the potentiometer.

STOP

Test Step 6. 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 may be installed or the jumper may not be installed, based on the phase sensing selection.

Results:

YES - The jumper is installed between terminals 6A and 9 for three-phase sensing. For single-phase sensing, the jumper is not installed between terminals 6A and 9. Proceed to test step 7.
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 7. CHECK CONNECTIONS FOR THE DROOP CURRENT TRANSFORMER (CT)

The genset remains off.
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. If a permanent magnet generator is used, proceed to test step 8. If a self-excited generator is used, proceed to test step 9.
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 CT lead connections.

STOP

Test Step 8. CHECK THE VOLTAGE INPUTS ON A PERMANENT MAGNET GENERATOR

Check the voltages between the following terminals:
- 26 and 28
- 26 and 30
- 28 and 30

Expected Result:

The voltages are between 90 VAC and 120 VAC.

Results:

YES - The voltage is between 90 VAC and 120 VAC. Proceed to test step 10.
NO - The voltage is below 90 VAC.
Repair: There is no power from the permanent magnet generator to the voltage regulator. Correct the wiring according to schematics. Refer to the Testing and Adjusting, "Wiring Diagrams". If the measured voltages are balanced, but the voltages are between 20 VAC and 89 VAC, replace the PM exciter rotor.

STOP

Test Step 9. CHECK THE VOLTAGE INPUTS ON A SELF-EXCITED GENERATOR

Check the voltages between the following terminals.
1. For input power that is single phase, check between terminals:
  - 28 and 30
2. Check between the following terminals for three phase input power applications.
  - 26 and 28
  - 26 and 30
  - 28 and 30
Measure the sensing voltages between the following terminals.
- 20 and 22
- 20 and 24 (if three phase sensing is used)
- 22 and 24 (if three phase sensing is used)

Expected Result:

The voltages match accordingly. The voltages are between 230 VAC and 250 VAC.

Results:

YES - For single phase power input, the voltage between terminals 28 and 30 matches the voltage between terminals 20 and 22. Proceed to test step 10.
YES - For input power that is three phase applications, all of the following are correct: The voltage between terminals 26 and 28 matches the voltage between terminals 20 and 24. The voltage between terminals 26 and 30 matches the voltage between terminals 22 and 24. The voltage between terminals 28 and 30 matches the voltage between terminals 20 and 22. Proceed to test step 10.
NO - The voltages do not match.
Repair: Check the jumpers between terminals 20 and 28. Check the jumpers between terminals 22 and 30. Also check the jumpers between terminals 24 and 26 if 3 phase sensing is used. Place the appropriate jumpers according to the wiring diagram. Refer to the Testing and Adjusting, "Wiring Diagrams".

STOP

Test Step 10. 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 11.
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 11. 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 lower than the nominal voltage. The generator voltage is steady.

Results:

YES - The generator voltage is still low but steady. Proceed to test step 12.
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, "Unstable Voltage". If the voltage is no longer low, the problem has been fixed.

STOP

Test Step 12. CHECK THE OPERATING FREQUENCY OF THE GENSET

Measure the generator frequency. Use the frequency meter on the control panel. You may use a multimeter with the frequency measuring function.

Expected Result:

The generator frequency is below 5% of the rated frequency.

Results:

YES - The frequency is below the rated frequency. In this case, the voltage will be lower 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 low voltage problem still exists. Proceed to test step 13.

Test Step 13. 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 low 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