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| Illustration 1 | g01425620 |
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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. |
Ensure that the "Settings Group Support Level" parameter is set properly. If the parameter is not set correctly, the CDVR will disable and lockout excitation. Refer to the "Settings Groups" section of Specifications, Systems Operation, Testing and Adjusting, RENR7941, "Group Support Level".
The information in this section also applies to the earlier version of the CDVR. Refer to Specifications, Systems Operation, Testing and Adjusting, RENR7941, "Earlier CDVR Dissimilarities " for the part number information of the CDVR.
- Verify that all of the wiring is properly connected. Refer to Testing and Adjusting, "Wiring Diagrams".
OK - If the wiring connections are correct, go to step 2.
NOT OK - If the wiring is improperly connected or the wiring is loose, reconnect the wiring properly.
STOP.
- Verify that the generator is running at rated speed.
OK - If the generator is spinning at rated speed, go to step 3.
NOT OK - If the generator is not at rated speed, increase generator speed to the rated value.
STOP.
- The digital voltage regulator is PMG powered or is shunt powered.
PMG power - Proceed to step 4.
Shunt Powered - Proceed to step 5.
- Check for correct input power to the voltage regulator. Refer to Specification, RENR7941, "Electrical", for input power requirements.
OK - If voltage is present, go to step 5.
NOT OK - If PMG voltage is not present, refer to the generator manual for the repair procedures and check for an open circuit.
STOP.
- Verify that the residual voltage applied to the power input is at least 6 VAC.
OK - If the applied voltage is 6 VAC or greater, go to step 6.
NOT OK - If the applied voltage is less than 6 VAC, refer to the generator manual and flash the generator field. Install blocking diodes in series with the battery in order to prevent damage to the voltage regulator and/or the battery.
STOP.
- Verify that the fuse is not open.
OK - If no fuses are open, go to step 8.
NOT OK - Replace any fuses that are open.
STOP.
- Verify that the CDVR is connected to 24 VDC control power.
OK - If CDVR is connected to 24 VDC control power, go to step 8.
NOT OK - Connect CDVR to 24 VDC control power.
STOP.
- Verify that the common alarm/Shutdown LED indicator on the voltage regulator is not flashing.
OK - If no protective fault has caused the excitation to be turned off, go to step 15.
NOT OK - If the LED indicator is flashing, open communications with the voltage regulator. Determine if a protective shutdown fault has occurred. A protective shutdown fault would cause excitation to be turned off. If protective shutdown fault has occurred that would cause excitation to be turned off, go to step 9.
- If an "Exciter Diode Monitor" (EDM) fault has occurred, stop the machine. Insure that the power input to the voltage regulator is removed. Unplug "P6" on the voltage regulator.
- Refer to the generator manual for instructions on checking the rotating exciter diodes. Have the rotating exciter diode assembly checked for open or shorted diodes. Refer to the generator manual for rotating rectifier assembly replacement if an open or shorted diode is present in the rotating exciter diode assembly.
- After repairs are complete, reset the voltage regulator by momentarily closing the "Fault Reset" contact or by cycling 24 VDC control power.
- The generator may be restarted. If there is no problem with the rotating exciter diode assembly, the EDM trip value may be set too low. An EDM fault may occur with good rotating exciter diodes under varying loads if the trip level is set too low. Set the EDM trip level to a value greater than the RMS ripple current that is present in the exciter field under normal operating conditions. The adjustment will prevent a false trip.
- Reconnect "P6". Reset the voltage regulator by momentarily closing the "Fault Reset" contact or by cycling 24 VDC control power.
- The generator may be restarted. If an EDM fault has not occurred, go to step 10.
- If an over excitation fault has occurred, stop the machine. Check the generator and/or load conditions for a generator or load fault. A generator or load could cause excessive exciter field current to flow. Check the system for loose or open connections to the voltage regulator sensing inputs. Any faults must be repaired.
- After repairs are complete, reset the voltage regulator by momentarily closing the Fault Reset contact or by cycling 24 VDC control power.
- Start the generator. Verify that no generator or load fault has occurred and there are no loose or open connections to the sensing inputs of the voltage regulator. If a problem still exists, verify that the over excitation trip level and the delay settings are properly adjusted for the generator.
- Set the over excitation trip level slightly above the requirement of the application. Do not set the over excitation trip level so high as to render the protection ineffective or damage the system.
- Reset the voltage regulator by momentarily closing the fault reset contact or by cycling the 24 VDC control power.
- The generator may be restarted. If the over excitation fault still exists, the instantaneous trip value of 28 A may have been reached by a faulty diode. The EDM virtual fault LED will not indicate in this case since there is a 5 second delay associated with the EDM fault protection. Go to Step 9. If an over excitation fault has not occurred, go to step 11.
Note: SR4 and SR4B generators may require up to 12 A for full load excitation. A 10 second delay is needed in order to insure 300 percent short circuit current requirements.
- If a loss of sensing fault has occurred, stop the machine. Have the system checked for loose or open connections to the voltage sensing inputs of the voltage regulator.
- Have the generator and/or load conditions checked for a generator or load fault that could cause the sensed voltage to be low.
- If the generator is equipped with step-down transformers for necessary voltage levels for the voltage regulator, verify that the transformers are functional. Also, verify that any transformer fuses are not open.
- If transformer fuses are found to be open, replace the fuses.
- Any faults must be repaired. After repairs are complete, reset the voltage regulator by momentarily closing the Fault Reset contact or by cycling 24 VDC control power.
- The generator may be restarted. If a loss of sensing fault has not occurred, go to step 12.
- If a field over current fault has occurred, stop the machine. Check the generator and/or load conditions for a generator or load fault that could cause excessive exciter field current to flow. Also have the system checked for loose or open connections to the voltage regulator sensing inputs. A field over current fault is detected when output current from the voltage regulator exceeds approximately 28 A.
OK - If a field over current fault has not occurred, go to step 13.
NOT OK - Any fault must be repaired. After repairs are complete, reset the voltage regulator by momentarily closing the fault reset contact or by cycling the 24 VDC control power. The generator may be restarted.
STOP.
- If an internal memory failure fault has occurred, try resetting the voltage regulator. Reset the voltage regulator by momentarily closing the fault reset contact or by cycling 24 VDC control power.
STOP. - If an internal memory fault has not occurred, go to step 14.
NOT OK - If after resetting the voltage regulator another internal memory failure occurs, replace the voltage regulator.
STOP.
- If an internal watchdog failure fault has occurred, reset the voltage regulator by either of the following methods:
- Momentarily close the fault reset contact
- Cycle 24 V control power
OK - If an internal watchdog failure fault has not occurred, go to step 15.
NOT OK - If after resetting the voltage regulator another internal watchdog failure fault occurs, replace the voltage regulator.
STOP.
- Replace the voltage regulator unit. If replacing the voltage regulator unit does not correct the problem, go to step 16.
- There is a problem with the generator. Refer to the generator manual to troubleshoot the problem.