Digital Voltage Regulator Caterpillar

1. Stop the generator set.

2. Check the wiring.

   Expected Result: The wiring is correct.

   Results:

   • OK: Go to Step 2.

   • NOT OK: CT polarity or PT polarity is incorrect. The incorrect polarity may generate erroneous faults. Reverse the polarity. See the proper wiring diagram for details. Refer to Testing And Adjusting, "Wiring Diagrams". STOP.

1. Start the generator set and load with 25% to 50% of rated load. Use 0.8 power factor inductive load, if at all possible.

2. Check value in parameters :04 and :05.

   Note: Parameter :52 (current) provides the measured value of the current in the B phase only.

3. Measure the ampere load on the B phase.

4. Measure the signal voltage level at regulator terminals 5 and 6.

5. Verify that it is in correct proportion to load amperes and agrees with the settings of parameters :04 and :05.

   Expected Result: Any parameters show negative numbers.

   Results:

   • OK: If any parameters show negative numbers, a CT or PT polarity is incorrect or the phase rotation is wrong. Verify the polarity and the rotation. STOP.

   • NOT OK: Go to Step 3.

1. Compare the value of parameter :52 to the actual generator current.

   Expected Result: Parameter :52 reads less than the actual generator current, which was measured by another meter.

   Results:

   • OK: Parameter :52 reads less than the actual generator current, which was measured by another meter. Slowly decrease parameter :05 until the currents match.

   • NOT OK: Parameter :52 reads more than the actual generator current which is measured by another meter. Slowly increase parameter :05 until the currents match.

Note: It is normal for the accuracy to be reduced at levels below 15% of rated load. In these cases, the digital voltage regulator may observe a 0.4 Per Unit leading KVAR due to unbalanced cross current compensation networks. The digital voltage regulator is sensitive to CT sizing. The droop current transformer should be sized to provide no more than 5 VAC (RMS) at full rated load but not less than 3.5 VAC either. Proper sizing will significantly aid the accuracy at lower power levels.

Note: If the digital voltage regulator is part number 155-xxxx or newer, check the value in parameter :20. If the value is very small, try increasing it until the problem is eliminated.