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PIG TESTING

 * Original msg to: Esondrmn-at-aol-dot-com

Quoting Ed Sonderman:

 ES> Richard,

 ES> Thanks for your recent response.  

No problem, just trying to be helpful.

 ES> I did try various settings on the welder when I was testing  
 ES> the other night. I can control the current within a range.   
 ES> At the lowest setting, I get about 15 to 20 amps.  I wish I  
 ES> could turn it down some more.  Even at this low setting,     
 ES> when the gaps finally fire the power is higher than I would  
 ES> like to be starting out at.  

Yeah, I can relate. The only other suggestion I can make would be
to look around for an adjustable high wattage resistor. Maybe the
Nichrome strap from a heater element could be doubled up to cut
the resistance in half, and double the current. Even if you add 
just a tiny bit of resistance it will greatly smooth things out.

 ES> The discharges from the 14" toroid with the pole pig are     
 ES> extremely vicious.  Everything is happening much faster and  
 ES> with much more power than before.   This is only running at  
 ES> 6 or 7 kv now, I can't imagine what this thing will do when  
 ES> I raise the output voltage to 12 to 15 kv.  

About the same with spark four times longer than you are getting
now. 

 ES> I don't know if I want to be in the same room with it.

Someone is going to have to man the controls :-)

 ES> Regarding spark gaps:  What you say makes sense.  My gaps    
 ES> are acting like an almost dead short across the output of    
 ES> the pig - and not quenching.  I did try repositioning the    
 ES> spark gap and the capacitor so the capacitor is across the   
 ES> HV and the spark gap is in series with the primary and the   
 ES> performance seems to be identical.  My plan is to build
 ES> a spark gap similar to what I saw in your video.  I plan to  
 ES> build an enclosure and use 4 or 5 two inch dia. sections of  
 ES> copper pipe, gapped at .020 and sealed so all the air flow   
 ES> must be between the 4 or 5 small gaps.  I plan to use my big 
 ES> Craftsman shop vac to provide the vacuum. Do you think this  
 ES> will work? 

That is a good question. It will work better than what you have
got. However, my experience has been that when you are trying to
quench a pig without the benefit of a rotary, the best config-
uration is a single gap (two electrodes faced off), with an
airblast and/or tight magnetic field. What happens in the simple
two electrode gap is that directly opposing electrostatic forces
breaks the gap down at a much wider setting. We are talking
between 3/8 and 1/2 of an inch. This means that the arc in the
gap is already given a pretty decent stretch at breakdown. The
arc is then lengthened out even more (to the breaking point) by
the high speed airstream, or rent asunder by the magnetic field.

The vacuum gap works best with a neon power supply or in series
with a rotary gap. If you are planning on building a rotary gap
in the very near future, skip the airblast design and start
working on the vacuum quencher. But even the vacuum quencher will
be overwhelmed on a pole pig without a rotary break: when the 
series of closely spaced gaps breaks down, there is just not
enough width, or force, at any (or all) electrode sites to force
a quench. The copper electrodes will burn, blister, and ionize,
making quenching difficult, if not impossible. I have had the
copper electrodes blister, deform, and weld together into a
"solid mass" direct short when fired right off a pig. With a lot
of fiddling, the vacuum quencher can get good results, especially
in series with a rotary. But for stand alone quenching at high
power without overheating or perfomance degradation, the airblast
gap is superior despite the infernal noise.

 ES> BTW, the guy that I bought the big Powerstat variac from     
 ES> called me this morning and said he knows where I can get an  
 ES> X-Ray power supply. 100kv dc at 200 to 300 ma.  Do I want    
 ES> one?  If I don't we can probably find someone on the list    
 ES> here who does.  I will check it out.

I don't need one. The only toy I could think it would be good for
would be a Marx generator or HV Taser gun. Like you said later
though, the control circuits and HV cabling would probably find a
good use.

Richard Quick





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