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Re: Low voltage sparkgaps for ignition coil driver...
Tesla List wrote:
> Original Poster: "Jim Lux" <jimlux-at-jpl.nasa.gov>
>
> ----------
> > From: Tesla List <tesla-at-pupman-dot-com>
> > To: tesla-at-pupman-dot-com
> > Subject: Re: Low voltage sparkgaps for ignition coil driver...
> > Date: Saturday, November 21, 1998 9:32 AM
> >
> > Original Poster: "James" <elgersmad-at-email.msn-dot-com>
> >
> > I'm surprized that you didn't think of using just a spark gap that
> was
> > rated, or just gapping a spark plug 20v/mil then run it through the
> primary.
> > Dielectric of air = 20volts to the millimeter.
>
> Air is 31 kV/millimeter in uniform field at usual pressures, etc. That's
> 3000 V/mm, not 20 volts millimeter as stated above. In Inch kind of units,
> figure 70 kV/inch (or 70 V/mil). I might add that a nominal .030 inch gap
> for automotive applications would break down at 2 kV in normal air, but in
> air at 10 times the normal density (that compression ratio thing, after
> all), it takes 20 kV+ to break it down.
>
> From: "Jim Lux" <jimlux-at-jpl.nasa.gov>
>
> <<<< I normally don't get involved with how accurate a post is. I assume
> we will all figure it out eventually. However, this thread seems to just
> get worse as time goes on! :-) I think Jim meant "Air is 3.1kV/mm" in the
> first line. Electrical breakdown in air, in short distances, is very
> non-linear and dependant on the shape of the electrodes. You will see all
> kinds of values. A number like 50kV/inch really doesn't have too much
> meaning without knowing if the electrodes are needle points, 1cm spheres,
> etc. and the real distance. There are good charts in older CRC books that
> list all this out. I will list needle point values here at Standard
> Temperature and Pressure from that book.
>
> Voltage Arc length in CM at STP for needle points.
>
> 0kV 0.00 :-)
> 5kV 0.42
> 10kV 0.85
> 15kV 1.30
> 20kV 1.75
> 25kV 2.20
> 30kV 2.69
> 35kV 3.20
> 40kV 3.81
> 45kV 4.49
> 50kV 5.20
>
> If you use electrodes of a different shape (like a spark plug) these
> numbers can change drastically!
>
> I hope this has been part of the solution and not part of the problem...
> :-)) - Terry >>>>
This is a wonderful list, I presume this is DC.
Anybody have the data for HF broken down by frequency or know what the
reference is. Do the CRC manuals have this? Which one? I don't seem to be
able to find it in the Handbook of chemistry and physics.
<<<< These are for DC only. AC gets strang. Perhaps someone else knows
about this? Only the OLD CRC books have this in them. The new ones droped
the chart out. - Terry >>>>
Bryan Kaufman