Re: Three Phase Power

Hi Jon (et. al.),
I was concerned that I would get a large amount of ripple on the
capacitors that create the DC buss in the VFD (which 'wants' three
phase) if I only used single phase, isn't this true? Using three
phase would reduce the rectified ripple to almost nothing. Should I
just add some extra BIG caps to the DC buss on the VFD if I use
single phase (or is feeding single phase to the VFD really not as
much of a problem as I though it might be)?

Thanks,

Jeff

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
>
>
> jeffalanp wrote:
>
> >Hi All,
> > Has anyone ever used a single phase to three phase rotary phase
> >converter to power a variable frequency drive VFD(which itself
runs a
> >three phase motor)? Is it a good/bad idea?
> >
> >
> Far better is to use a slightly larger VFD, and run it directly
from the
> single phase!
> Most manufacturers will now admit that you can run a 5 Hp motor at
full
> power
> indefinitely from a 10 Hp VFD. For home shop use, you generally
can
> even run
> a 5 Hp motor from a 7.5 Hp VFD without much trouble. The VFDs are
rated
> for some pretty harsh conditions, such as only 208 V 3-phase, and
convection
> cooling only in a 45 C ambient temperature inside a cabinet. In 30
C
> room air,
> and with 240 V single phase power, the rectifiers are under less
stress,
> and everything
> else is about the same.
>
> What you propose is workable, but a huge waste of space and energy,
not
> to mention
> making a lot of noise in your shop. It is simply unnecessary. I
am
> using a 1 Hp
> Magnetek VFD to run a 1 Hp Bridgeport mill on single phase, and it
has
> no problem
> at all, although the manufacturer would have a cow. I also use the
same
> VFD to
> run a high speed spindle on 80 V @ 400 Hz. This draws more current
from the
> VFD, and I put a fan on it when I do this.
>
> Jon