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