You know Jon, that finally occurred to me. It is getting pretty close
to solving the whole thing, except I was planning on also running a
(2HP) lathe off of it (NOT hot switching them!). This may be sufficient;
the lathe motor is enclosed, so I bet it will be pretty hard to hear 12kHz.

Thanks,
Steve
whose head would be clearer if he wasn't bone tired from limping around
after falling on the stairs

Jon Elson wrote:

Steve Smith wrote:

It isn't the motor I'll be using the VFD on. I suppose what I should
do is get some hydraulic oil and fire up the forging press with it
(intended 3HP use).

Oh, heck, if you're going to be running a hydraulic pump with it, you
most likely won't hear the whine. I don't know of ANY hydraulic pump
that could possibly be called quiet.

But, if it still is a problem, an output reactor has a chance of
helping. It filters the very square output waveform of the VFD
to be much more rounded off. This should reduce the magnetic effects
that are causing the windings to sing.

Jon