Re: Triggered gaps vs Sync rotary

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 7/26/02 5:54:36 PM Eastern Daylight Time, tesla-at-pupman-dot-com
writes:

Jim,

Good idea, maybe someone will try that.  At least it doesn't have to
be a sealed unit.  A compressor can inject ambient air into the gap 
vessel at a high volume to cool and quench the gap, and a small 
outlet hole can release the compressed air (and heat) while maintaining
a 45-60 psi back-pressure.  The air input volume vs. output flow rate 
can be adjusted to maintain the proper internal air pressure, while 
removing the heat at a sufficient rate (hopefully).  The gap vessel
can be made of metal with fins on the outside to assist the cooling 
if needed, perhaps with an external fan if needed, or even an
external water jacket.

John


>
> On the other hand.. if you keep the primary voltage low (to keep the gap
> short, while still not breaking down), the currents will be high (which
> also reduces the voltage drop across the gap).. And, of course, a typical
> pig powered coil probably could tolerate a little lower efficiency (who
> cares if you draw 10 kW or 10.5 kW, as long as the sparks are big).
>
> A pressurized triggered gap might be the way to go.. Run it at, say 45 psi,
> and the gap can be 1/4 the length.  Now, of course, you've got all the
> problems associated with pumping the gas around to keep it cool, etc.
> Hmmm.. can conduction cooling work for this? Can you run a muffin fan in a
> tank pressurized up to 45-60 psi? (Don't see why not?)  I do know that it
> is devilishly hard to get heat out of a sealed box full of air.  A tiny fan
> in open air will keep something reasonably cool, because you've got an
> infinite sink and source to work with.
>
> A Marx type blast gap doesn't need a huge flow in a CFM sense because the
> orifice is small, and the air velocity is high for good quenching, so maybe
> a small air compressor would work (like those used for dental equipment or
> airbrushing.)
>
>
> Say you build the gap for a self breakdown of 20 kV, running the coil at 10
> kV RMS.. Normally you'd need a gap of around 0.30 inches for this.. You
> pressurize to 60 psi, giving yourself a 5:1 increase in breakdown voltage
> for a given gap, now the gap only needs to be 0.06 inches. With a gap that
> small, you'll probably get significant cooling by conduction.
>
> Not only that, but because the gas density is 5 times higher, there are 5
> times as many ions to carry the current, reducing the resistive voltage
> drop along the spark.  Not only is the spark shorter, but it's also less
> loss per meter... you might get a N^2 improvement! (N for the density, N
> for the shorter gap)