I had some bad news last night.

As the drive was running the motor, the motor leaks a lot of current
through its insulation. (like Joe Gwinn story) Not good. Phase
converter does not create this effect, so it is due to voltage spikes
from the drive that this old insulation cannot handle. I do not want
to ignore this issue by grounding, as I feel that it can ruin the
motor.

I may try to locate a line reactor to dampen this, and shorten some
cables, but for now I will go back to the phase converter.

i