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Re: [TCML] High Power Static Gaps



Hi Gary,

Interesting test. I think the vortex gap has two causes for the higher bang energy. 1) higher pressure and 2) the radius put on the electrodes of the vortex (assuming the vacuum gap still had the sharper edges). Although the gaps are rather close (.031 and .034), the vortex likey had a significantly higher breakdown voltage and thus higher energy dump. The gaps are pretty close in distance, so I'm not sure where to contribute the gain. The biggest difference I can visualize is bang voltage, and this appears to be the reason for the lower losses.

It's difficult for me to compare these two types without ensuring the breakdown is as close to equal as possible so that the bang energy is relatively constant between the two (current in the arc and arc length).

What you state does make sense (I'm just not sure this particular test shows it) and I suspect if the vacuum gap was set to breakdown at the same value as the vortex gap, the arc length would be the defining loss factor. So yes, that would be a significant improvement.

Regards,
Bart


Lau, Gary wrote:
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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