Re: Triggered gaps vs Sync rotary

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>



Tesla list wrote:
> 
> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<FutureT-at-aol-dot-com>
> 
> In a message dated 7/24/02 1:48:47 PM Eastern Daylight Time, tesla-at-pupman-dot-com
> writes:
> 
> Jim,
> 
> Good point about the soaring losses at higher powers.  I hadn't
> thought of that, and I don't think anyone mentioned it in the past
> during the triggered gap discussions.  Perhaps a triggered
> gap may never be very efficient for large coils, unless some radical
> improvement can be thought of.
> 
> Cheers,
> 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)