RE: [TCML] High Power Static Gaps

["Lau, Gary" <Gary.Lau@xxxxxx>]

Hi Bart,

I agree that the higher pressure gap of the same geometry will have the higher breakdown voltage.  But if we move the electrodes closer together to achieve the same breakdown voltage as the low pressure gap, I think this will result in a lower gap resistance and lower gap losses.  This was the theory that motivated the design of my vortex gap.  The comparative measurements I made between the sucker gap and vortex gap, documented at http://www.laushaus.com/tesla/vortexgap.htm, show that the higher-pressure vortex gap has lower gap losses and resulted in a slower ring-down rate of the uncoupled primary.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of bartb
> Sent: Monday, September 08, 2008 11:04 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] High Power Static Gaps
>
> But consider this, high velocity air in a non-pressurized chamber across
> a gap versus high velocity air within a chamber across the same gap
> causing pressurization. How do these two gaps differ? It's the pressure.
> And that pressure will increase the breakdown voltage to arc the gap.
> With a gap set equally between these two gap types, the pressurized gap
> will perform better since it will require a higher voltage to arc the
> gap, summing to a higher energy bang. I think when all things are set
> "equal" (breakdown and air velocity), there may not be much of a
> difference. I don't see the mechanism for it. I'm not saying there is no
> difference, simply that I fail to see the what it is.
>
> Take care,
> Bart
>
> Quarkster wrote:
> > Bart -
> >
> > I'm not sure that I agree that the performance "will be the same".
> >
> > Certainly, you can increase the width of the non-pressurized gap so the
> breakdown voltage is the same as a pressurized gap. However, one of the largest
> benefits of of a correctly-designed "pressurized" gap is the extremely high air
> velocity through the gap. Quenching should be measurably better than a simple
> ventilated TCBOR gap, or even a vacuum gap where the maximum pressure
> differential across the gap can never exceed 14.7 PSI. However, I don't have
> comparative data at this point .....
> >
> > Regards,
> > Herr Zapp
> >
> > --- On Sun, 9/7/08, bartb <bartb@xxxxxxxxxxxxxxxx> wrote:
> >
> > From: bartb <bartb@xxxxxxxxxxxxxxxx>
> > Subject: Re: [TCML] High Power Static Gaps
> > To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> > Date: Sunday, September 7, 2008, 4:46 PM
> >
> > The static gap DC Cox has been discussing this last year in various
> > postings is just this. It's a simple pressure gap. Nothing special other
> > than the pressure is changed via forced air. A pressure gap changes the
> > air pressure. This increases the breakdown voltage for a given distance
> > and electrode geometry.
> >
> > With "all things equal", I don't realize longer sparks. All
> > things are
> > not equal. To equalize the gaps (pressure versus not), increase the gap
> > distance on the non-pressurized gap to equal the breakdown of the
> > pressurized gap. At that point, they will perform the same (and harder
> > on transformers because of the higher breakdown voltage).
> >
> > Regards,
> > Bart
> >
> > futuret@xxxxxxx wrote:
> >
> >> Another (at least theoretical) advantage of using pressure for
> >> the gap is that the gap spark length is shorter in higher pressure air
> >> than in lower pressure air for a given voltage.  Short sparks have
> >> lower losses so a stronger spark output streamer length should
> >> result.  I'm not sure how much difference it makes in the
> >> real world.  I think Gary Lau used this approach when he
> >> switched from his vacuum gap to his vortex gap.  It's interesting
> >> to note that whereas Gary obtained around 63" sparks from his
> >> vacuum and vortex static gaps, he obtained around 80" or 90"
> >> sparks using a sync rotary spark gap, using the same NST power supply
> >> transformer.
> >>
> >> I don't think all that much work and research has been done in
> >> this area (high powered air blast quenching for Tesla coils), so it's
> >> worth
> >> more experimentation.
> >>
> >> An useful approach might be to add an electronic trigger electrode
> >> for stable 120 bps operation.  This adds complexity, but not of
> >> the mechanical machining type.
> >>
> >> John
> >> ----------
> >>
> >>
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