Converting single-phase 120 V or 240 V into three-phase 4-wire 120/208 V
What is the best way to accomplish this?


Make a list of all the individual loads. Determine what voltage, current and number of phases is actually supplied to each. If you have VFDs and a DC motor controller that requires 3-phase input, you can get 240 V, single-phase alternatives for those. It seems like most of the loads may be 120 V, single-phase.

It is not a good idea to use a VFD to power something like that. There are likely loads that will not tolerate the VFD output waveform very well. There are also likely loads that the VFD will not tolerate very well.