Re: CNC PLASMA

OCV (Open circuit voltage) on a plasma cutting power supply will in
the neighborhood of 300-325VDC. In operation this voltage will vary
as it is a constant current power supply. A cutting arc can be
initiated many diffrent ways, HF, Pilot Arc, HF+Pilot Arc. Some
pilot Arcs are started by HF some by an arc that is formed when parts
in the torch head are (physicaly and electrically) seperated by the
gas pressure. HyperTherm and Miller both use a non-hf power supply
(or used to, I've been out of the business a couple years), of course
Miller uses Hypertherm torches.

One of the biggest problems with plasma cutting is all the electrial
noise that is generated. It loves to find it's way into controls and
cause havoc. Even high$$$ comercial controls have this problem.
Your cutting table and power supply MUST be properly grounded.

The next probelm is maintaining the correct torch height during the
cut. Sheet metal will still warp as it is being cut and can cause
varing kerf or even snuff the torch out. Commercial systems most
often measure the arc voltage and attempt to vary the height of the
torch to keep the voltage constant. Some use a 'rollare ball' type
of cage that goes around the torch and push down the metal in front
of it.

FWIW,

Jeff

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
<davemucha@j...> wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, STAN MCDONALD

<smcdonal@k...>

> wrote:
> > Charles VanLeeuwen wrote:
> >
> > Why reinvent the wheel. You would still have to use a plasma

torch

> that
> > is comercial built because you need a supply of contact tips as
> well as
> > other consumable parts. That being said a plasma cutter is kind

of

> like
> > HF tig in the since that the HF is used to get the arc going. The
> hart
> > of the unit is a transformer that puts out 100 amps or less
> depending
> > upon how thick you want to cut. I think it is at around 600 Volts
> but I
> > may be wrong. This power is rectified and converted to DC and then
> > filtered via a RC time constant.
>
>
> I thought that the high frequency stuff used very low amps, like 5-
> 20 ? but due to the high frequency, the watts were huge ?
>
> Dave
>
> Speel checked kuz I got hart.