Why Is My 3-Phase Generator Voltage Clipping and Distorting?

[cookan]

I have a 600v 3 phase generator that will not put out a stable voltage. When looking at the sine wave through a scope meter I see phase “B” and “C” are clipping at 690v, Phase A is still a sine wave but with some cross over distortion. Phase “A” peak is 840v. Any Ideas?

 

[NascentOxygen]

Welcome to PF! Is this a diesel powered 3 phase alternator?

 

[jim hardy]

is it connected to a load?

has it been recently worked on?

does it smell of hot insulation?