OK heres my question as a story problem.

I currently have a 3 phase rotary converter in my shop. 10HP works great for general machining, and the two CNCs I have both VMC's. Of course I did have to make sure L1 L2 were wirred to control phase of transformer. I'm getting a wire EDM machine this Friday and as far as i can tell there is a +/- 5% voltage rating between phases as a requirement. What I would like to know is if I can use a VFD after the rotary to help balance the phase voltages to supply the new EDM?

Also what does the AMP rating on a VFD mean AMP/Line or total AMP draw? Is a VFD more efficient when supplied with 3 phase than single?

Regards,
Heli