K65-12B Voltage Regulator Caterpillar

Low Voltage

Usage:

Test Step 1. PERFORM THE INITIAL CHECK

Turn off the genset.

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Illustration 1	g01021519

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The Cat K65-12B Voltage Regulator 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:

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.

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Illustration 2	g01021519

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The Cat K65-12B Voltage Regulator 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, 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 3.
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 CONNECTIONS OF THE VOLTAGE ADJUST RHEOSTAT

Turn off the genset.

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Illustration 3	g01021519

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The Cat K65-12B Voltage Regulator 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:

OK - If a remote voltage adjust rheostat is NOT used, the jumper is properly installed. Proceed to test step 5.
OK - If a remote voltage adjust rheostat is used, the jumper should be removed from terminals 4 and 7. In this case, the remote voltage adjust rheostat should be connected to terminals 6a and 7. Proceed to test step 4.
Not OK - 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 RHEOSTAT

Disconnect the wires from terminals 6a and 7.

Measure the resistance of the remote voltage adjust rheostat while the rheostat is being adjusted over the operating range.

Expected Result:

The resistance should be between 0 kOhm and 10 ± 0.5 kOhm.

Results:

OK - The resistance increases smoothly within the specified range. Proceed to test step 5.
Not OK - The resistance is not within the specified value. The resistance jumps to a high value when the rheostat is adjusted.
Repair: Replace the remote voltage adjust rheostat.
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 may be installed or the jumper may not be installed, based on the phase sensing selection.

Results:

OK - 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 6.
Not OK - 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 according to the sensing that is desired.
Stop.

Test Step 6. CHECK CONNECTIONS FOR THE VAR/PF CONTROLLER

Verify whether there is no jumper between terminals 2 and 3.
Note: If a VAR/PF CONTROLLER is not used, there should be a jumper between terminals 2 and 3. If a VAR/PF CONTROLLER is used, the jumper should not be in place.

Expected Result:

The jumper has been placed accordingly.

Results:

OK - 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 7.
Not OK - The connections are not correct.
Repair: Place the jumper according to the wiring schematic.
Stop.

Test Step 7. CHECK CONNECTIONS FOR THE DROOP CURRENT TRANSFORMER (CT)

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The secondary wires or terminals of the current transformer must be shorted together when they are disconnected from the equipment. If electrical current passes through the primary windings of a current transformer with the secondary wires or terminal disconnected, extremely high voltages may be generated on the secondary wires or terminals. Bodily contact with high voltage can result in serious injury or death.

Stop the genset.

For a 1 Amperes CT, verify that the connections are to terminals 5 and 6.

For a 5 Amperes CT, verify that the connections are to terminals 5a and 6.
Note: For troubleshooting purposes, it is possible to operate the voltage regulator when the droop current transformer is disconnected. However, the secondary wires of the droop current transformer must be connected together.

Verify that the polarity connection of the droop current transformer is connected to terminal 6.

Expected Result:

The connections are correct.

Results:

OK - The connections are correct. Proceed to test step 8.
Not OK - 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 THE VOLTAGE REGULATOR

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

Expected Result:

The voltages are between 63 VAC and 105 VAC.

Results:

OK - The voltage is between 63 VAC and 105 VAC. Proceed to test step 9.
Not OK - The voltage is below 63 VAC.
Repair: There is no power which is coming 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 62 VAC, replace the PM exciter rotor.
Stop.

Test Step 9. VERIFY THE SENSING VOLTAGE

Make sure that the generator set is off.

Check the range of the sensing voltage at the secondary windings of the potential transformers. The sensing voltage range should lie between the following limits:
- 90 V to 140 V

Verify that sensing wires 20, 22, and 24 are 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:

OK - The sensing voltage is correct. The connections are correct. Proceed to test step 10.
Not OK - 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 10. CHECK THE OUTPUT VOLTAGE

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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.

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:

OK - The generator voltage is still low but steady. Proceed to test step 11.
Not OK - The generator voltage oscillates. The voltage goes very high. Then, the voltage goes very low.
Repair: Add the 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 11. CHECK THE OPERATING FREQUENCY OF THE GENSET

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Failure to follow instructions will result in death or serious injury.

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:

OK - 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.
Not OK - The generator frequency is same as the rated frequency. The low voltage problem still exists. Proceed to test step 12.

Test Step 12. 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 range and the low voltage 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". If necessary, replace the voltage regulator.
Stop.