File 460-230_VFD.JPG contains two schematic diagrams.

The first, labeled "460 volt 3¯", is a conventional 460 volt, three-phase VFD 
which drives a 460 volt, three-phase motor. The three-phase input is labeled 
R, S and T. The three-phase output is labeled U, V and W.

The second, labeled "230 volt 1¯", is the same VFD, but which has been 
modified to drive a 460 volt, three-phase motor from a 230 volt, single-
phase supply. The single-phase input is labeled L1 and L2. The three-phase 
output is labeled U, V and W.

The so-called "converter section" has been modified from a three-phase, full-
wave topology to a single-phase, voltage-doubler topology, as shown in the 
second diagram. The so-called "pre-charge" and "inverter" sections remain 
unchanged.

The presence of series electrolytic capacitors on the dc bus is probably not 
unique to the specific drive shown.

It is, however, quite convenient that series capacitors were available, as this 
significantly simplifies the "rework" required to convert the VFD from 460 
volts three-phase to 230 volts, single-phase input.

I do not claim that this method will work for all 460 volt three-phase VFDs. In 
fact, it is likely that most VFDs cannot be converted without additional 
modifications.

Also, I do not claim that a similarly modified VFD will work without derating.

Rather, derating is most likely required. Or, alternatively, the values of the 
"bulk storage" capacitors on the dc bus could be substantially increased.

If so, the rating of the diodes in the converter, and also, possibly, the "soft 
start" thermistor, would have to be changed.

To protect the guilty, the identity of the VFD is not disclosed.

Enjoy.]