The noise you describe can be reduced to almost nil if you change the carrier frequency setting on your vfd. What brand of vfd are you using?...... Factory setting are usually around 5K HZ. That makes the sound within normal human hearing range. If you set it to above 12K HZ it will make the sound frequency at the high end of normal hearing. Some people can hear sounds up to 20K HZ but as we age our ability to hear high frequency sounds diminishes.
There are a couple of other vfd parameters you could look at that might improve smoothness. Check out the excellent YouTube video series by Clough42 where he installed a Teco vfd on his lathe.
I have a Teco L510 and a VFD Rated 2hp 220V 3ph motor. I've watched all the Clough42 videos on VFDs and a few dozen others. Also read the manual cover to cover. I agree that changing the carrier frequency might address some of the whine but I sort of doubt that is what I'm hearing. My carrier frequency is set to 4k. Trouble is that I know I can't hear above 2k at my age. I get my hearing checked regularly because I have significant hearing loss. I've had my ears checked again just a few months ago. I have hearing aides that are tuned to amplify sounds from 800hz up and no matter how much they amplify, they cannot make my ears hear what they cannot hear. Even when I was young I didn't hear above 8k or so. On the other hand, I do hear subsonic tones well below 60Hz that the vast majority of others don't hear. I'm sort of like an elephant in that way.
Anyway, according to my old audio frequency generator, I would say that the whine that bothers me is around 1600 Hz. Next time my wife goes out there, I'll ask her if she hears anything at higher frequencies.
The other point is that the whine is only there at certain motor speeds. If it were a carrier noise, I would think that it should be present across the whole speed range.
As
@Dabbler points out, there is also the possibility that I have some line noise. My current temporary wiring is just solid core unshielded Romex. So it is possible that my problem might be line noise instead that is broadcasting rf to my hearing aides, or perhaps creating audible resonance in the hardware somewhere. That what I meant previously when I mentioned adding CL filters.
I don't really have time to chase that down right now. But I do have a pretty complete set of instrumentation (100Mhz storage oscilloscope, waveform generators, frequency generators, signal injectors, etc) that I can use to chase the problem down with and it is an area in which I have experience. Hopefully it will help.
