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Re: Primary Qs

Tesla List wrote:
> 
> >> Subject: Re: Primary Qs
> >Subject: Re: Primary Qs
> >> Subject: Re: Primary Qs
> 
> >From dll-at-egg-rb-dot-comThu Oct  3 22:24:41 1996
> Date: Thu, 3 Oct 1996 08:57:52 -0400 (EDT)
> From: dll-at-egg-rb-dot-com
> To: tesla-at-pupman-dot-com
> Subject: Re: Primary Qs
> 
> On Wed, 2 Oct 1996, Tesla List <tesla-at-poodle.pupman-dot-com> wrote:
> >> Subject: Re: Primary Qs
> >
> >>From hullr-at-whitlock-dot-comWed Oct  2 22:43:19 1996
> >Date: Wed, 02 Oct 1996 12:10:31 -0700
> >From: Richard Hull <hullr-at-whitlock-dot-com>
> >To: tesla-at-pupman-dot-com
> >Subject: Re: Primary Qs
> >
> >Tesla List wrote:
> >>
> >> >From MALCOLM-at-directorate.wnp.ac.nzTue Oct  1 21:55:47 1996
> >> Date: Wed, 2 Oct 1996 09:03:02 +1200
> >> From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
> >> To: tesla-at-pupman-dot-com
> >> Subject: Re: Primary Qs
> >>
> >> Greg,
> >>       Thankyou for this info....
> >>
> >> > > Q does trend up with increased gap current showing a drop in gap
> >> > > resistance. It would be useful to get readings for much higher
> >> > > voltages but the supply and caps on hand wouldn't allow it.
> >> >
<SNIP>
> Since Paschen's law is basically a statement of continuity ( The number of
> electrons leaving the anode must equal the number injected into the gap at the
> cathode.) there is a time delay between the application of voltage and gap
> breakdown.   The breakdown voltage increases with the rate of rise of the
> applied voltage.  The ratio of the static to the dynamic breakdown voltage is
> called the Surge Ratio.
> 
> The Townsend breakdown theory from which Paschen's equation derives, assumes
> that the breakdown process starts with a single electron-ion pair.  When a high
> frequency voltage is applied to a gap as with Tesla coil operation, there is
> insufficient time for all of the charges in the gap to dissipate before the
> voltage is reapplied. The charge that lingers longest is on the insulating
> walls.  If the voltage across a gap is monitored, it is seen to decrease from
> the initial dynamic value to a lower steady state value, and as the frequency is
> increased a value will be reached where the gap conducts continuously.
> Fortunately this frequency is many megahertz for most gap designs.
> 
> I would like to see some data showing breakdown voltage at 100 to 300 kHz as a
> function of pressure for some spark gaps.


Thanks for posting the detailed info.  I noted in my post above that for 
small gaps of fixed pressure and set geometry, equations existed for 
accurately determining break down.  Paschen's is one of those that work 
in this narrow context.

I have come to learn that when science can't give a simple and direct 
explaination for a phenomena or the phenomena is just too variable, the 
degree of non-linearity and thus, the lack of control over the process, 
is directly related to the square of the physical constants (A and B) 
loaded into the precise equations to state the law.  These constants are 
derived from experiment and real life experiment.  Such constant are 
themselves often variable under non-laboratory conditions.  In a 
manufacturered gap, all the constants are pure and perfect, and remain so 
for the life of the gap.  We have a controlled and sealed environment 
manufacturered to the limit of scientific and engineering repeatability. 

With Tesla coil builders, we have a bunch of dorks dinkin' around with 
gaps with no controls and virtually no knowledge.  To give these folks 
Pachen's equation is a bit like inviting a biker mama to the opera.  She 
will expect to be entertained just as the coilers will stream out there 
and turn the handle on the equation.  She will most likely be bored to 
tears (there are exceptions) and the coiler will most likely not apply 
the equation corectly or wisely. (there are exceptions)  The unknowns are 
the biker mama's ability to adapt and enjoy new things, and the A and B 
constants to be derived or more often guessed at by the coiler.

Both the biker mama and the coiler have the right to go to the opera and 
know of and apply paschen's equation, respectively.  It is just that the 
vast majority of either set of beings will undoubtedly be disappointed in 
the results.

Remember folks, if you are out havin' fun and looking for sparks, use 
equations the least and the power switch the most.  You will develop a 
feel for the system and all the charcteristics which science seeks to pin 
down with precision.  You will ultimately acquire a general comprehension 
of materials and methods required through deed and artifice.  Most of 
your work will evolve through hunches and guess work.

If you are out to further the science of High voltage resonant 
systems, then be very mindful of the need for physical constants in 
formulating equations.  You will need to do a bit of lab work to define 
them in order to apply the mathematics which guides you hand.


I'm a little of both and a lot of neither.  Engineers rely on mathematics 
to design a lot of stuff.  Old engineers rely on experience to temper the 
rush to accept the math as something precise and use a lot of "fudge 
factors"  (formerly, physical constants) in creating real works.

Richard Hull, TCBOR