[TCML] High Power Static Gaps
bartb at classictesla.com
Tue Sep 9 19:46:48 MDT 2008
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.
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 at pupman.com [mailto:tesla-bounces at pupman.com] 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,
>> 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 .....
>>> Herr Zapp
>>> --- On Sun, 9/7/08, bartb <bartb at classictesla.com> wrote:
>>> From: bartb <bartb at classictesla.com>
>>> Subject: Re: [TCML] High Power Static Gaps
>>> To: "Tesla Coil Mailing List" <tesla at pupman.com>
>>> 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).
>>> futuret at aol.com 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
>>>> 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
>>>> 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.
>>>> Tesla mailing list
>>>> Tesla at www.pupman.com
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