There is another more major manufacturer of VFDs for single phase motors, a company from the UK called
Invertek. They sold in the US mainly through two other companies here called Bardac and Anacon, both of whom most make DC drives, by brand-labeling the Invertek for AC. But more recently, Invertek has been setting up distribution in the US directly under their own name too.
The thing is, they (the single phase versions) ONLY work on PSC motors and Shaded Pole, but Shaded Poke can be used with simple dimmer type controllers anyway, so it’s really just PSC that makes any sense. Cap-Start and Cap-Start/Cap-Run motors that use centrifugal switches are the problems, and those account for most single phase motors that are not on fans and pumps. When you slow them down below the speed at which the centrifugal switches operates, the caps and aux winding comes back into the circuit and can take out the transistors in the drive, or the harmonics of the VFD output get absorbed by the caps and they over heat and blow.
My personal experience with both ATO and Gohz both is less than stellar and neither were listed by any NRTL last time I tried any. In both cases, they are using a 3 phase drive and telling people they work in single phase motors, without proper warnings that they don’t work on ALL types of single phase motors.