On Fri, 18 Jul 2008 07:51:27 -0500, Ignoramus31221
wrote:

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.

Dropping the drive's carrier frequency should also help, and is free.
You may notice more audible noise. Some drives also have a setting
that softens the corners of the chopped output and that will also
help. I assume this lowers the efficiency of the drive, but that's
presumably of little concern here unless the drive is not well
ventilated.

--
Ned Simmons