If it's one motor (or a couple that always run at the same speed at the same time), I'd use a VFD. Multiple motors that do not run at the same time, I'd use an RPC.
True, but to feed an open delta transformer bank, you still need a three phase supply, but the O/P desires to work a 3 phase motor from a single phase supply.
Open delta transformer banks have the advantage of requireing the purchase of only two transformers instead of three, but dont create 3 phase from single phase.