Re: [CAD_CAM_EDM_DRO] Re: VFD's / Skates, Tim & JohnS.

> Problem, I am unable to find anywhere selling single phase 460volt input
> VFD's. All the 460volt ones I've found want three phase input. Why is it
> difficult to step up the voltage after it's been VFD'ed? Is it something to
> do with the way the transformer responds to the difficult frequencies? Any
> ideas who might sell a 460volt single phase input VFD if not? I feel the
> appeal of the midget machines returning. Probably find out the motor has
> been replaced with a single phase 230volt now.... sod's law! : )

A single phase input VFD differs from a three phase input VFD in that
it has at least one set of diodes capable of handling the full current
requirement and capacitors big enough to fill in the longer gaps
between 60 (50) hz peaks as opposed ot the 180 (150) hz peaks seen
when you combine 3 phases each with its own set of diodes. Often
people simply buy 3 phase input VFD's that are rated for substantially
larger motors than they plan to use and simply leave the third input
leg unconnected.

Trying to follow the VFD with a transformer won't work because the VFD
is designed to interact directly with the motor. Good ones can sense
quite a bit about what the motor is doing and compensate. Putting a
transformer in will at minimum really mess up the sensing, and
probably blow components or worse.

Any chance you can rewire the motor for 230v? I know my 230v 3-phase
motors can all be rewired for 460...

Or find a 3-phase input VFD that you can derate for single phase input.

Chris