Although they make commercial products, there’s some interesting info at sites like
www.gwm4-3phase.com and
www.phaseconverter.com From a D-I-Y vantage point, usenet newsgroups rec.crafts.metalworking and rec.woodworking address the subject periodically in motor FAQs.
Because the output of virtually all converters is 3-wire, there is no wyepoint neutral to connect to or measure, so no 120°-wye service. They are closer to a 240V Δ system, or maybe 240/120V 3ø 4-wire open-Δ. This gives you the “original” 240V—L1 and L2, and a second approximately 240V that is shifted by roughly 60° for L1-L3; giving around 240V for L3-L1. Don’t expect very tight voltage balance—that is generally implied when reading converter-manufacturer literature.
Because converter phase-to-phase voltage can be fairly unbalanced, so significant motor-horsepower derating [about 57% in some cases] may be necessary. Rotary phase converters have to be started and up to speed before running any connected 3ø motors. Don’t plan on powering any controls from the phase converter—they are not generally stable/regulated enough for that.
Don’t forget NEC ARTICLE 455.
