You have a timid phase. It needs therapy, like Tony said. Best to call in an expert.

Let's just hope that the other two phases haven't been bullying it.

Maybe it's just going through a phase....

thanks for all. I think the exciter damaged, the resistor off if the high load becauce a high temperature. After generator off, the resistor normal again, because have a lower temperature. Is a possible? Now the generator low loaded.

It still is a high risk operation. What, if you short out something in the exciter? What will blow up? What will happen when the exciter start producing overvoltage?

The beginning of wisdom, is to know when to leave well enough alone.

Please open the generator set and check status of connections. The problem may be due to a loose connections or an overheated terminal.

Remember one thing dear

"SAFETY comes first"

Please at 450KVA and load more than 300 A, one phase disappears? Strange but call generator manufacture for help!!