Re: Racing arc clues...

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Robin,

You coil is interesting!  At one point it seems to resist racing arcs:

http://www.geocities-dot-com/rcopini/2ndlighti-1.jpg

But at another is seems to race well:

http://www.geocities-dot-com/rcopini/2ndlightl-1.jpg

From:
http://www.geocities-dot-com/rcopini/2ndlight.html

We think that higher order harmonics set up on the secondary may create
local high voltage gradient areas that promote these arcs.   However, the
same effect may also cause relatively dead areas along the secondary.
These great photos would seem to show both.  Still much to be learned in
this area but we are getting there.

High coupling tends to make higher order harmonics worse.  Raising your
secondary a little may reduce or eliminate the problem if it is bad enough
to worry about.  Since it is a high voltage breakdown phenomena, air
temperature, humidity, etc. will all have an effect.

Cheers,

	Terry

At 02:18 PM 6/2/2001 +0930, you wrote:
>Hi Justin.
>
> I am grateful for the number of people who are interested in my problem 
>with racing
>arcs. However, it is not as common as my post my alludes. Some specs just for
>interest sakes.
>
>Secondary : 10inch form 40 inches close wound with 18g double insulated
copper.
>Primary : half inch copper pipe, tap point, I don't recall, but suffice to 
>say in
>tune.
>Cap : CD 942C16P33K - 0.33 MFD 1600VDC, 630VAC, 33 in series, 7 panels for 
>0.07mfd.
>power source : Pole pig, rated 220in/33Kv out , 15 KVA. Overdriven to 
>280Vin, 20Kva.
>Top Load : 12inch X 36inch, (if I recall correctly), spun aluminum 'psuedo' 
>toroid,
>Fres Sec 92Khz.
>
>If you want to look, go to
>
> http://www.geocities-dot-com/rcopini/
>
>I run my coil about 1 time per month, or more depending on spectators. My 
>experience
>is high heat levels definitely have a deleterious effect as far as racing 
>arcs are
>concerned. In good conditions, and at full power the coil has produced arcs 
>in excess
>of 4.5 metres. In bad conditions, I can't power up to more than half input 
>power
>without having racing arcs. I would be almost certain it has nothing to do 
>with my
>cap, The longest run at high power levels, (within 10% of full power), was 
>for almost
>7 minutes, (we were trying to destroy a laptop :-)  ), the coil never 
>altered it's
>performance levels so a cap variation is fairly remote. I find this problem 
>very
>interesting because the coil itself is never changed, just the running 
>conditions, so
>there, I believe, lies the root of the problem.
>
>Best Regards
>
> Robin Copini
>
>P.S. Chris, tell CD the caps are great!
>
>
>
>Tesla list wrote:
>
>> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
><Pyrotrons-at-aol-dot-com>
>>
>> Hi All.
>>
>> My 2 small copper coins as far as Robin's racing arcs go.
>>
>> To John Freau:
>>
>> I respect your knowledge, especially your past (present?) work with coil
>> efficiency. Although I agree with most if not all the things you mention, I
>> would rule out some of your "tossed around ideas" in your previous post.
>>
>> The line voltage powering Robin's coil *might* could vary enough to cause
>> racing arcs along the secondary, but I doubt it. If it is, then it's
possible
>> that the voltage is just under the threshold (for racing arcs) when the line
>> voltage is on the downside. (Robin, stick a voltmeter in the wall before you
>> run and write the voltage down. Also note whether there were racing arcs at
>> the time)
>>
>> I also doubt that humidity or wind is the problem. Aron and I once ran a 12"
>> TC system at 10kVA in the *thick* fog and *hard, driving* rain when it was
>> *really* windy. (winter storm, of the kind where bad weather lasts for days)
>> Water was dripping down the coil like mad, yet the coil performed nearly as
>> well as it did on a still Autumn night. There have been times though, on
Aron
>> and my 6" NST powered system that humidity *completely* killed the output.
>> Zip from the topload. Arcs were awesome when it was dry w/ same setup. This
>> was done over and over.
>>
>> We need line voltage measurements, but I suspect one other thing that hasn't
>> been mentioned before.
>>
>> Tank capacitor value has been known to change during coil runs. This changes
>> Fr of the tank circuit relative to the secondary circuit, throws things out
>> of tune, and in turn causes the racing arcs. Our MMC capacitor for our 4"
>> coil used to do that at the end of it's lifetime - the primary would have to
>> be tapped a WHOLE TURN IN at the end of a 30 - minute "play" period to get
>> much out of the thing.
>>
>> I theorize that some of the individual Philips cap's were shorting out (it
>> had a lot of hard runtime on it at the time), therefore lowering the number
>> of cap's per string, raising the capacitance, lowering tank Fr, and
requiring
>> that inductance be knocked off the primary to stay resonant with the
>> secondary circuit.
>>
>> I am sorry I missed seeing the cap type before - Robin, what kind of
>> capacitor ARE you using? I've seen this effect (to some degree) with other
>> capacitor types also. Mail me your cap type off list please.
>>
>> Take care Robin, John, All.
>>
>> Justin Hays
>> KC5PNP
>> Email: pyrotrons-at-aol-dot-com
>> Webpage: www.hvguy-dot-com
>