Re: [CAD_CAM_EDM_DRO] EDM power supply

Joel Jacobs wrote:

> Hi Jon,
> I only mentioned it because an electrician once showed me how 'dangerous'
> they were - he took the wire from the ballast, struck an arc to the sheet
> metal fixture and proceeded to burn a hole through it. He was demonstrating
> how you could short it out and it would not blow the breaker. Of course it
> didn't because the ballast was power limiting the arc as it was designed to
> do. I don't know what the current was but it seemed like quite a bit more
> than 40ma. It was the ballast in an outdoor sign that had two 8' 80W tubes
> in it.
> There are also higher power ones used in mercury vapor, sodium and halide
> lamps. If I were going to experiment with EDM I would probably play around
> with these a bit. A full wave rectifier would give 120 sparks/sec.

Yup, this is kind of like an arc welder. AC and a lot of inductance to keep
the
arc going. EDM is exactly the opposite. You DON'T want the arc to stay in
one spot, you want it to hop around and evenly remove metal all around the
electrode. That's why the arc is interrupted, either by the discharge of small

capacitors or the pulsing system.

Oh, yes, the 8' tubes run on higher current that the 48" tubes. I think the
48" tubes come in 32, 35 and 40 mA ratings.

Jon