Original poster: David Speck <dave@xxxxxxxxxxxxxxxx> Christoph,Solid state VFDs have lots of protection circuits built into them that sense if anything is wrong with the motor circuit, and try to shut down the drive before letting the magic smoke out of the big power semiconductors. Just as using solid state NSTs to drive TCs doesn't work very well (if at all), then I would be very surprised if you could successfully drive a TC supply from a VFD. Building a rotary three phase converter would be much more likely to succeed. You can get big three phase motors from junkyards for little more than scrap metal value. Look for older, (pre 1990) low efficiency motors. The modern high efficiency motors are reported to overheat in rotary converter use. You will have to make some investment in a starting contactor and starting capacitors. Figure about 100 uF starting capacitance per HP of motor rating. You will also need some run capacitance of about 10 uF per HP to properly balance the output voltages, but with adjustment, you can probably get the outputs within 10% of each other. Be sure to use motor run caps, rather than motor start caps (start caps heat up quickly (and blow up) if run for more than a few seconds). Your net investment will still probably come out less than the cost of a decent sized solid state VFD, and the rotary arrangement will be much more robust in a TC arrangement.
Dave
The Idea was: Can I use one of the cheap medium sized VFD units you sometimes find on ebay to at least test drive a 3 Phase TC system.