In any case, the answer is to get a variable speed motor controller.
Those are oversized inverters that produce adjustable frequency 3
phase AC from either single or 3 phase inputs. The primary purpose is
to feed variable frequency power to 3 phase motors, which will change
their speed -- much handier than gear boxes. But as a bonus, they
will also serve to produce 3 phase power for those of us stuck in the
back country.
In my previous life as an industrial electrical-instrumentation
contractor, I have used VFD's to drive 3 phase loads from a single phase
supply. The main thing you have to remember, is to derate your drive.
As an example, drive a 2.5hp load from a 7.5hp drive. The VFD's will
provide a smooth sine output and will protect your load device. Look
around at some industrial surplus sellers. With the current trend of
offshoring manufacturing plants, there seems to be a lot of equipment
showing up on the surplus market. We had a lot of luck using the
Allen-Bradley 1336 series of drives. They were Mitsubishi under the
skin and seemed to be very forgiving. We also used a lot of Hitachi's
and Toshiba's too.. No complaints with those either.
James
http://www.allenbradley.com/drives/1336PlusII/index.html