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Re: SG - The anatomy of the spark?
Hi Bob, (comments intersperced)
> Original Poster: "Bob Berg" <berg_bob-at-hotmail-dot-com>
>
> It seems to me that some of the easiest ways to improve coil output
> performace can come from changes in the spark gap. I'm no expert and
would
> like to know more about what happens in a spark gap.
>
> In a perfect world how would we want the spark gap to act?
Opening and closing in 0.0 psec. when we want to, i presume. Closing behind
Umax, opening on the first notch.
> What is the resistance of a spark gap when it conducts? Can this
resistance
> be reduced?
In our application a couple of ohms. Can be reduced by overvoltage the spark
gap, by 60Hz or 50Hz resonance and at the same time the same gap length. The
bigger the current the lower the resistance (negative resistance from
breakdown point).
> What is the diameter of the arc in a spark gap, is it bigger with more
> current?
Yes, of course (i don't know HOW big, because i don't think this knowledge
would help)
> Quenching, From my understanding, quenching is act of "Blowing out a the
> spark in a spark gap. But I don't understand why is so important. If I
> "Blow Out" the spark won't I prevent the capacitor from dumping ALL of
its
> energy into the primary? Or is it the act of quicky turning off the
current
> in the primary for a sharp collapse in the feild in the primary that is so
> important?
There are other way's to quench than blowing holes in the plasma, for
instance 2 big flat conductors in opposit position or magnetic quenching or
combinations. But anyway, the time the tank cap needs to dump his energy is
normally a quarter of a period of the resonance frequency. This will start
the ringing and the co-operation of the two resonance circuits will result
in something like an interference frequency depending on the degree of
coupling.
(see: http://www.staff.ncl.ac.uk/r.e.burnett/operation.html#notches for
understanding notches)
With a coupling of 0.1 it takes normally about 5 periods to the first notch
and if the secondary capacitor has the right dimensions it would arc at that
moment. It is useless to put in energy after that moment, wouldn't it?
> Is it possible to over quench?
Yes, see the preceeding text. It would be very difficult however to quench
on another point then a notch (or too much current or too much potential).
> Also, can some one give me a simple understanding of "Ringing" in the
> primary. I get the feeling that Ringing is the oscillations that occur in
> the primary tank circuit when the Capacitor is discharging through the
gap.
> If I'm correct no explination is needed. However, what I confused about
is
> when the capacitor is discharging into the primary what is happening to
> power of my NST going into the cap?.
There is no 'ringing in the primary'. There is ringing period! The two
circuits are electro-magneticallly coupled, remember?
All the time that the gap is 'closed' the NST is shortened, but the energy
of the cap is so big comparable to the NST that this is not of much concern.
What is of concern however is the degree of RF power flowing back to NST.
That is the reason you need a RF filter between the gap and the NST.
>
> Thanks
> Bob
>
I hope this will help, but please visit Richie's place. Of course there are
a lot of good other Tesla sites, but in my humble opinion this is one of the
best. (Sorry guys)
Greetings from Holland,
Ruud de Graaf