Electrical question

[f350ca]

I've only started trying to figure these out so I know enough to be dangerous. But i'd go for the one behind door two. It states it uses sensorless vector technology, I think you want that, from what i understand the processor measures the phase angle between the current and voltage on the load, essentially power factor, to determine if the motor is lugging down below its synchronous speed. It then boosts the voltage or current or frequency, not sure which to give the motor essentially constant torque below 60 hz. Better more expensive systems put an encoder on the motor and feed that back to the vfd to do the same thing.
The first one says it will work on single or three phase input, (no real specs) but Id expect that to be one you would need to under rate with single phase input and only run a 2 hp motor with it.
I want to use one on a bowl lathe so I've been trying to learn what I can. My buddy that owned an electrical company that specialized in factory automation was my go to guy for stuff like this. He left the country or something? One of his employees is running the show now. Have stopped by a couple of times but he hasn't been around. If I catch him in the office we should be able to get the real story, not opinions off the net, like mine of course. It was him that leaned me to the Phase Perfect solid state 3 phase converter I have now. He was right on that one.