running a 3 phase motor using a 120V(1.5Hp max) or 220V(usually up to 3Hp) VFD is how most of us get variable speed. TECO/Westinghouse, Allen Bradley, Baldor, Leeson, and Siemens are trusted industrial suppliers and make VFDs that are designed to run 24/7 for years without failure. PM me what you are looking for and I can work you up a quote.