Digital Voltage Regulator Caterpillar

1. Check the part number of the digital voltage regulator. Refer to the chart in Testing And Adjusting, "Troubleshooting". Check whether the digital voltage regulator is proper for the application.

   Expected Result: The digital voltage regulator is proper for the application.

   Results:

   • OK: Go to Step 2.

   • NOT OK: Install the proper digital voltage regulator. STOP.

1. Stop the generator set.

2. Observe the display on the digital voltage regulator.

   Expected Result: The display should contain a number.

   Results:

   • OK: Proceed to Step 4.

   • NOT OK: No number is present on the display. Proceed to Step 3.

1. Check for proper DC voltage from terminal "B+" to "B-". The acceptable voltage range is 18 VDC to 32 VDC.

   Expected Result: The sufficient DC voltage is present.

   Results:

   • OK: The sufficient DC voltage is present. Remove the DC power wires from terminals "B+" and "B-" for 30 seconds. Reconnect the DC power wires to the "B+" and "B-" terminals. If the display of the regulator is still blank, the regulator is faulty. Then, the regulator needs to be replaced. If this condition has occured, verify that the correct burden resistor or the rheostat is connected between the droop current transformer and the regulator. If no resistor is present, the regulator was destroyed because of high current on the CT input. Refer to Testing And Adjusting, "Wiring Diagrams". STOP.

   • NOT OK: The sufficient DC voltage is not present. Repair the supply voltage wiring, fuses and circuit breakers, if necessary. STOP.

Parameters :10 or :13 must not be set too high.

1. If the underfrequency point (parameter :10) is set too close to the nominal operating frequency, then the voltage may not build. Look for an undervoltage fault code. If the code is found, try the default value.

2. If the undervoltage trip point (parameter :13) is set too close to the nominal operating voltage, the voltage regulator may shutdown and report an undervoltage fault code. Try the default value.

3. Display the number in parameters :92, :93, and :95 (if present). A display of "0000" indicates no faults. If a fault code is present, see System Operation, "Parameters".

   Expected Result: The problem has been resolved.

   Results:

   • OK: The problem has been resolved. STOP.

   • NOT OK: The problem has not been resolved. Proceed to Step 5.

1. Turn the engine off.

2. Check that all of the digital voltage regulator connections are tight and properly made per the appropriate wiring diagram.

3. Check PM fuses (connecting to terminals 26 and 30 of the digital voltage regulator).

4. Restart the engine.

5. Check the PM inputs (26, 28, and 30) of the digital voltage regulator. Measure the AC voltage between terminals 26 to 28, 28 to 30, and 26 to 30.

6. If the digital voltage regulator is connected as a self-excited regulator, check if the power transformers are properly wired as an open delta configuration for the according wiring diagrams. Check if the power transformers are properly sized in order to provide a minimum of 1200 VA each.

   Expected Result: The proper voltage is approximately 95 VAC for 60 Hertz generator sets and 79 VAC for 50 Hertz generator sets. The voltage must be stable. Voltages up to 120 VAC, 60 HZ are acceptable.

   Results:

   • OK: The voltage is correct. Go to Step 6.

   • NOT OK: The voltage is incorrect or unstable. PM stator or PM rotor is damaged. Troubleshoot the PM unit. Replace the faulty component. STOP.

1. Check the sensing inputs between the digital voltage regulator terminals 20 to 22, 22 to 24, and 20 to 24.

   Expected Result: All 3 readings should be balanced and with proper PT ratio to the output voltage.

   Result:

   • OK: All three readings are balanced. Go to Step 7.

   • NOT OK: The readings are unbalanced. Check all connections to the regulator. Check all connections to the output terminals. Make sure that proper potential transformers are installed, if applicable. Check the neutral connection. Check for the correct phase rotation. STOP.

1. Turn the engine off.

2. Disconnect all accessory wiring from terminals 3, 5, 6, 7, 40, 41, 42, 43, 44, 45, and 50. Remove the serial data link, if installed.

3. Start the generator set and operate at "No Load".

   Expected Result: The generator set operates properly.

   Results:

   • OK: The generator set operates properly. There is a problem with an accessory which has been disconnected. Proceed to Step 8.

   • NOT OK: The generator set does not operate properly. Proceed to Step 9.

1. Reconnect one accessory. Operate the generator set again at "No Load". Continue this process of reconnecting one accessory at a time until the faulty accessory is found.

   Expected Result: The problem has been resolved.

   Results:

   • OK: The problem has been resolved. STOP.

   • NOT OK: The problem has not been resolved. Proceed to Step 9.

1. Start the generator set.

2. Measure the voltage from F1 to F2.

   Expected Result: The proper voltage is from 6 to 14 VDC at no load.

   Results:

   The 3 possible results are listed below.

   • The voltage is present for a short time, but trails off to or near zero. Shut the generator down. Megger the exciter stator and rotor. Check the rotating diodes.

   • The voltage between F1 and F2 is near zero immediately after the generator set starts. Stop the generator set. Remove the wires F1 and F2 from the digital voltage regulator. Restart the generator set. Measure the voltage from F1 to F2 on the digital voltage regulator.

   • The voltage between F1 and F2 is near zero immediately after the generator set starts and after Step 5 has been thoroughly completed. The digital voltage regulator is faulty. The digital voltage regulator needs to be replaced.