Thanks for all the input. The problem was finally identified as a bad resisitor in the control circuit. As the circuit heated up the resistance would increase to the point that the system could no longer regulate.
Here is more info to support all the input so far.
1. Problem occurs when the machine is parallel with Utility.
2. Voltage regulator (VR) has been swapped between a sister unit that is working properly. Symptoms remain the same.
3. VAR/PF controller was replaced.
4. Droop CT input to the VR was...
If you are familiar with a current boost generator exciter system. We have a 5MW, 4160 volt generator that will run at 2.5MW and 0.9 PF for about 8 minutes and then the field becomes over excited and the generator begins producing excessive VARS. After a breif restart process the machine will...
