Re: spark gap question...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "S & J Young by way of Terry Fritz <twftesla-at-qwest-dot-net>" <youngs-at-konnections-dot-net>

Triggered spark gap fans and potential fans,

I hope one of you will sometime try a really widely spaced (e.g. 1 to 3
inches) triggered gap and makes some performance measurements.   The trigger
source can be a small TC which throws an arc a few inches long, probably not
needing a toroid.  This little TC could in turn be driven via its own
triggered gap.  The little trigger TC should be wound with a thousand or so
turns of fine wire so its impedance is many times greater than the main tank
circuit.  This ensures most of the main bang will go into the big coil and
not the little trigger TC secondary.  Could this work well?  Just imagine
the quenching of a two inch gap!  Spark gap modelers - how much do gap
losses increase with gap spacing?

--Steve


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, July 02, 2001 8:00 AM
Subject: Re: spark gap question...


> Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<bert.hickman-at-aquila-dot-net>
>
> Marc, Gary and all,
>
> Interesting discussions! I actually suspect that Marc is correct, and his
> coil's performance seems to bear this out. The key difference between the
> triggered gap and others may lie in the gap's wider interelectrode
distance
> versus previously tested gaps. This prevents premature self triggering
even
> at maximum peak capacitor voltage - the hold off voltage may be 2-3X that
> of a normal gap. Once triggered, the "follow through" current from the
tank
> cap assures good conduction until the first primary current notch. The
> combination of wide gap spacing and high velocity air flow may be more
> effective in preventing retriggering than any gaps previously tested.
>
> Initially, the main gap must hold off the peak capacitor voltage before
> being triggered - typically tens of kilovolts. However, after we've
> triggered the gap and transferred most of the bang energy to the
secondary,
> we have a comparatively long period of low or zero current at each primary
> current notch. At (or near) the first current zero, the arc will self
> extinguish. At this stage we "only" need to prevent it from reigniting.
> However, really only need to hold off the voltage that's induced into the
> primary from the oscillating secondary via transformer action. This means
> we only need to hold off a few kV since (with the gap open) we will
prevent
> any transfer of secondary energy back into the primary tank cap. As long
as
> the gap can "hold off" a few KV, the gap will NOT reignite. This is tough
> for most gaps, so they reignite, leading to quenching at the 2nd or 3rd
> notch (or worse).
>
> However, all normal static or rotary gaps have much closer gap electrode
> spacing - this makes it very difficult to remove sufficient heat and
> conductive ions quickly enough to prevent reignition even at a reduced
> voltage. Since the triggered gap uses a much wider gap spacing, we'll end
> up with a larger voltage drop across the arc as we approach a current
> notch. When combined with high air flow, it may be sufficient to prevent
> reignition, or at least reduce the number of notches before quenching. We
> don't need to completely remove the plasma channel - we only need to
> disrupt it sufficiently to recover enough dielectric strength to hold off
a
> few kV - at a much wider gap spacing.
>
> I'm beginning to believe that the triggered gap has the potential to
quench
> BETTER than any previously seen gap... certainly better than a SRSG, since
> the rotary electrodes are actually coming CLOSER together once they've
> initially fired. And it's much simpler!
>
> Best regards,
>
> -- Bert --
> --
> Bert Hickman
> Stoneridge Engineering
> Email:    bert.hickman-at-aquila-dot-net
> Web Site: http://www.teslamania-dot-com
>