BRAKE AS- 3888463 - Caterpillar

the R438 Automatic Voltage Regulator (AVR) does not appear to operate correctly, first check that the AVR is set correctly. Check the jumpers, the jumper links and the potentiometer settings. Refer to the System Operation, KENR9009, "Voltage Regulation" for information in order to set the jumpers correctly. Some failures that occur in the exciter system for the generator can falsely appear as failure of the AVR. Test the insulation on the main stator or the rotor. Also test the insulation on the exciter stator or the rotor. Testing the insulation will ensure that the insulation has not deteriorated. Insulation that has deteriorated would result in poor performance and unsafe operating conditions for the generator. While severe deterioration may result in burned windings, less severe deterioration can result in an undervoltage, an overvoltage, or a shutdown of the AVR. These problems can occur after 10 seconds from start-up. These problems are more likely to occur when moisture or condensation affects the winding insulation. This may not be apparent as a cause of failure. The windings are not visible. Moisture may evaporate before a service technician is able to troubleshoot the generator. Perform an insulation test on the main stator windings. If the test results indicate that an insulation resistance is unacceptable then repair the windings. Measure the internal resistance of the stator windings of the exciter. The exciter stator may have an internal short. This will lower the resistance of the exciter stator. A lower resistance may cause a higher excitation current that may cause the AVR to trip intermittently. If the resistance is not within the allowable range then the exciter stator is faulty. The exciter stator must be repaired or replaced. If the system components are working properly, and the AVR is set up correctly, use the troubleshooting procedures in order to troubleshoot problems with the excitation system for the generator.