Cat® Digital Voltage Regulator Caterpillar

Illustration 1	g01425632

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The Cat Digital 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.

1. Verify that the chassis of the voltage regulator is properly grounded.

   OK - If the voltage regulator is properly grounded, go to step 2.

   NOT OK - If the voltage regulator is not properly grounded, connect a dedicated ground wire to terminal P6-6 on the voltage regulator.

   STOP.

2. Check for grounded field leads.

   OK - If the field leads are not grounded, go to step 3.

   NOT OK - If the field leads are grounded, isolate the field leads from ground.

   STOP.

3. Check for grounded PMG leads.

   OK - If the PMG leads are not grounded, go to step 4.

   NOT OK - If the PMG leads are grounded, isolate the PMG leads from ground.

   STOP.

4. Verify that the generator frequency is not dropping below the voltage regulator under frequency set point when load is applied to the generator.

   OK - If poor regulation is not related to voltage regulator under frequency operation, go to step 5.

   NOT OK - If the generator frequency is dropping below the under frequency set point, reduce the set point if possible. Also check the engine and generator for proper sizing in relation to the applied load.

   STOP.

   Note: Measure the PMG voltage from line to line.

5. Verify that regulation is not being affected by normal droop operation. If droop operation is not affecting regulation, go to step 6.

6. Verify that regulation is not being affected by normal line loss compensation. If line loss compensation is not affecting regulation, then replace the voltage regulator.

On new applications and when commissioning, check the PID value. If the voltage fluctuates at steady-state "No Load" or "Full Load", reduce Kg or if at 1.0 reduce Kp. Recalculate PID with the calculator.

Note: Self Excited (shunt powered) generators will have a greater input power voltage than PMG generators. Self Excited (shunt powered) generators will require lower gain settings. First, adjust Kg, then Kp if necessary on comparably sized machines. Adjust the Kg values first, then Kp values to reach acceptable steady-state and transient responses.