Yes, and that PoCo check will fall in the "if you have to ask the price, you can't afford it" realm. And there are cases where the utility won't do it to residential addresses for any price.
For even the most serious hobby and even a lot of small commercial cabinetry shops, it is rare to see machinery with more than a 5hp motor, and even that is really pushing the envelope. I can easily build a small production woodworking shop with 5hp equipment. For metalworking, there's larger equipment used by hobbyists but still way under that 15hp rule of thumb.
No matter how I slice it, there's little reason to use 3-phase motors on single-phase power. For hobbyists there are multitudes of appropriate machines. And for commercial/industrial use, the location should have 3-phase power anyway.
It is always that "good deal" on used equipment where you run into such troubles. Even just installing phase conversion equipment sometimes gets the response - "that is more then I paid for the machine", to which you can usually reply "did you check how much a new machine designed to run on single phase costs?".
Most recent one I can recall though it has been maybe 3 years ago - a three phase rotary air compressor. Was only 10 hp, but was used and acquired "cheap" (I assume). They had someone else add static phase converter to it. It kept tripping motor overload and they asked me to look into it. My conclusion - it ran unbalanced as expected with that type of conversion, It ran at pretty low load level until pressure started to get closer to shutoff setpoint. We could tweak current balance to some extent by changing capacitor connections in the converter - but since load varied according to tank pressure could never have it balanced at all times.
Motor was an OEM motor and standard general purpose motor would not be a direct replacement without modifications -
My advice to them, we tweaked converter to have most balance at near cut off pressure, when the motor was loaded the most. Cranked overload protection level enough that it wouldn't trip at that load level though one leg was higher than nameplate FLA.
Since the thing didn't get constant use that helps some, but told them to just run it as is until it burns out the motor - which wasn't really predictable as to how soon that would be, and did depend on how much use it actually sees. Then replace with OEM single phase motor if one is available or get a general duty single phase motor and make any necessary modifications to make it fit.
Seems it had different shaft then a general purpose motor would have had from what I can recall was the biggest factor in not swapping the motor when they already had spent $$ on phase conversion equipiment, so might as well run it how ever long it will last and then assess the situation when that happens.
