Hello all,

three weeks after overhauling a Grasso S3 2500 compressor, the bearings of the driven rotor looked like there were small welding spots on the outer and inner ring, the balls were damaged.
It seems that the (also) overhauled electrical drive motor is generating current which is transported through the rotor of the compressor, and then throuhg the ball bearings to earth. That is the only explanation what I can think of.

Anyone faced this problem before, or has another explanation?

Thanks, Gerben