Good call on water, dust/swarf resistant VFDs, I use KB Electronics KBAC 27Ds in the shop, claim to be wash down resistant (IP-65). Run around $300-$350, will handle up to 2 HP.

When I built/installed the rotary phase converter in my shop it ran $600-$800, if VFDs were that cheap 15 + years ago, thats the route I would have gone.