It looks like this Delon circuit might be useful for feeding 240DC to a
small VFD using 120VAC. 
http://en.wikipedia.org/wiki/File:Bridge_voltage_doubler.svg
http://en.wikipedia.org/wiki/Voltage_doubler 

The transformer in the schematic would be the pole transformer, so all
that would be needed is a couple of big diodes and capacitors. I suspect
one could run a 1HP three phase motor from a normal US wall outlet this
way. A breaker and/or overload protection would be good to add too.

There are three half bridges on a VFD three phase input, so feeding DC
to two inputs would have forward current on the same two VFD diodes full
time. Single phase 240VAC would have four diodes in play part time. I'm
not sure if this would be a problem.

Ahh, just found this:
http://www.practicalmachinist.com/vb/transformers-phase-converters-vfd/voltage-doublers-diode-based-vfd-front-ends-102923/
 
Short URL: http://alturl.com/pfqqb 

http://www.voltagemultipliers.com/html/multipliers.html 

Looks like a step up transformer feeding AC might be preferred if one
can find one cheap enough.

How do the Solar inverters get away with switching the the inverter
output load?
-- 
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/index.html
California, USA


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