You are correct. I didn't look carefully at what you were proposing. I do believe the 15hp motor will still draw more amperage than a 10 hp under the same load but that may work ok. I have bought a lot of stuff from Automation direct but never their drives. Have they been reliable?@BRT when I spec drives at the plant I oversize them as well, but you are limited when using it as a phase converter because they are severely downrated by the manufacturer for heat. You have to go up to a 60hp drive to get 15hp single phase. The one I linked is a 25hp drive and even the 50hp drive in that series is only rated for 10hp1p. The 60hp is way overkill IMO for that, certainly at 3x the cost.
He's trying to run 10hp, so running 2/3 the RPM will give him that with the same pulleys. It's not really ideal, but it is what it is when using the VFD's.
I'm sure there are some other 15hp1p vfd's out there if you go digging, that's just a decent series to find. General rule of thumb if using a generic VFD for single phase is to double the hp rating. Technically only have to go 1.73 (sqrt3) which in this case is 25hp, and you'll be fine since the amp draw is the same. I don't know why those are derated as far as they are. If concerned, just go to double the HP rating and you'll be fine.
Problem with a normal phase converter is you still need to add the soft starts in there and the costs get crazy.
Normally any VFD can run single phase at 66% of capacity. The limitation is the rectifier setup having to provide power through only 2 legs. Which makes me curious why that 25hp drive is rated 10hp 1 phase instead of 15hp???