The VFD takes single phase 240, changes it to direct currant, chops that into variable frequency 3 phase and sends that to the motor.
You want a VFD with constant torque. I have a Teco VFD on a 1 hp motor that I turned down to barely moving and tried to stall it by grabbing the motor pulley. I could not stall it.
See: Transformers, Phase Converters and VFD - Practical Machinist - Largest Manufacturing Technology Forum on the Web
Variable-frequency drive - Wikipedia, the free encyclopedia
One day I bought a nice slightly used 1 HP 3 phase, and a new in crate 3 HP 3 phase motor at my local junk yard for 50 cents a pound. With some steel my bill was under $40.
I looked up the 3 HP in Granger catalog, it was $356.
A motor shop might have used checked out 3 phase motors.
The 1 HP Teco VFD was about $130 from an internet supplier.
So much timber, so little time.