Or, make a simple starting system for a 3-phase motor. Some people just use their foot on a sheave attached to the shaft. I use a capacitor with a voltage controlled relay to cut the starting capacitor out of the circuit once it is up to speed. Three-phase power can be taken from that "idling" motor to power other motors. It is called a rotary converter, which is similar to, but not exactly the same as a motor-generator set.
How clean a 3-phase do you need?
John