Digital Voltage Regulator Caterpillar

Note: If you change a parameter, you must exit the parameter before the change of the parameter will take effect.

1. Check the wiring.

   1. Stop the generator set.

   2. Check the wiring.

      Expected Result: The wiring is correct.

      Results:

      • OK: Go to Step 2.

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

2. Check the parameter values.

   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 the values 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.

3. Check the value of the generator output current.

   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: If the generator set neutral is connected to ground or a neutral bus, then measure the neutral current. If a significant amount of circulating current is present, it may cause incorrect readings. A harmonic analysis is recommended in order to help determine the nature of the problem.

      Note: It is normal for the accuracy to be reduced at levels below 15% of rated load. The digital voltage regulator is sensitive to the size of CT. The droop current transformer should be sized in order 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.