Re: [CAD_CAM_EDM_DRO] VFD's / Skates

>
> > rating is based upon 3 phase input and you derate the unit by 50% if you
> are
> > on 1 phase input.
>
> I hate English Literature but I managed an A*. When you say derate by 50% do
> you mean instead of the 2hp direct to the motor I need an inverter for 4hp,
> does that mean I actually feed it 4hp?
>
> John He.
>

No, but it keeps you from frying the bridge rectifiers.

The VFD converts 3 phase AC to DC, then synthesizes the output AC
waveform. With 3 phase input the input current is spread across the
3 phases and has (relatively speaking) less ripple for the power
supply caps to filter out.

On single phase, all of the input current is on two input lines and
there's more ripple in the output. By derating the VFD you're
staying within the operating parameters for best operation.

That's not to say you can't do it, but operation may get a little
eratic at high loads. And you'll void the warranty. For home
use, you might get away with it. I ran a 5hp lathe for a while with
a 5hp VFD. I wouldn't recommend doing that with one you bought new.

The bottom line is to see what the manufacturer says. I think you can
get smaller VFDs (~ 1hp) that can be run on either 1 or 3 phase without
derating.

Paul

--
Paul Amaranth | Rochester MI, USA
Aurora Group, Inc. | Systems & Software
paul@... | Unix / Windows / NT