Since having to repair my rotary converter this week (one of the run caps decided to release it's magic smoke), I just had a thought.

Most VFDs don't like switching loads, and I don't fancy paying the price for one that is designed for switching loads. (I could get real 3 phase installed for less than the quotes I got!)

However, what would happen if you coupled one to a big idler motor, ala Rotary Phase Converter, and then used that to drive switched loads?
It would remove the need for a step-up transformer, and all capacitors. The idler motor would help smooth the output, and with the surges from switching on other motors.
The only thing I'm not sure about is how it would handle any spikes caused by switching off big loads. The idler motor would certainly help, but I'm not sure if that would be enough?
I suppose a surge suppressor could be added, or filters to block spikes, but I wouldn't know what would be effective.

Given the cost of these VFDs, I am almost tempted to buy another one to try, before I start rebuilding my existing rotary converter (it is back working, but it really needs a refresh, and made a bit safer than an open steel box perched on a shelf )