.. being a simple ME sometimes I get confused when talking about things like “switching into an inductive load, and the end result is noise that exists in the high frequency/high voltage realm,” but I do know enuff of the EE stuff to be dangerous!
Okay, here's a mechanical translation:
Take a horizontal beam, free at one end, fixed at the other. Let's say it has a section modulus capacity of 600lbs. Put an elastically supported load off the free end that's 480lbs... and since it's a weight on spring, you have Simple Harmonic Motion. In electrical sense, the equivalent is capacitance (the elastic) and inductance (the inertia) for a 'tank circuit'.
Now, while that weight is bouncing up and down, take a hammer, and whack the beam a dozen times.
The SHM of the 480lb weight is equivalent to AC waveform of voltage and current.
The shock and harmonics of the ringing beam, from the strike of the hammer, is the equivalent of switching noise.
Sum and difference of waveforms of the bouncing weight, plus the shock of the hammer whack, PLUS the harmonic action of the ringing beam, will present a stress in excess of the beam's section modulus, and you'll soon see a failure...
You could drive the AC motor at constant speed... but doing it with a VFD... I wouldn't... if you had a VFD in hand, and you were in MY shop, you'd get a motor, belts, etc., and make up a complete working drive system, and do a full swap... it's not that involved. PM me an email address and I'll send you pictures of what I did, or if you're around Davenport, just stop by and give mine a test-drive.
I recommend that if you wanna keep the M/G, either fix up your rotary converter, or use Peter's conversion method to make the MG motor run on single phase. There's a bit more electrical challenge to doing that ('cause you'll hafta pick your way through old, dark wiring), but it works fine...