Dear Ed
I at least think you should look at Pachen's Law which talks about
gas breakdown as function of pressure and E (is there something
else-another variable I forget?).

I did not know the long form till Bill advised here.

Books are important even if you don't have them, n'est pas?

Paul



Ed Huntress wrote:
"William J. Beaty" wrote in message
om...

"Tim Williams" wrote in message

...

"William J. Beaty" wrote in message
e.com...

I wonder where this 300V (or 1350V from Jim Lux' page) actually
comes from?

Nowhere. Tell me, how is stick welding performed?

Um... You don't know? And you just IGNORE the breakdown
equation without comment? OK, I'd like to hear your reasoning
for why that "Paschen rule" isn't important. We can send your
discovery to Jim Lux and he can add it to the High Voltage Handbook.




The rules and handbooks you're talking about are things with which I'm not
familiar, but it sounds like this is being made more complicated than it is.

The dielectric strength of air is around 3 x 10^6 V/m. That means that you
can create a spark with something like 90V at a gap of 0.0012 inches.

That's within the gap range of a typical EDM. Gaps run from perhaps 0.0002
in. for fine-finishing to maybe 0.005 in. or a little more for roughing.

It doesn't take a very high voltage to initiate a spark if you have a
sensitive servo mechanism to maintain a close gap.

Ed Huntress