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Re: Sold state IGBT disruptive coil spark gap idea

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi John,

Tesla list wrote:

Original poster: FutureT@xxxxxxx
In a message dated 4/30/06 6:36:14 PM Eastern Daylight Time, tesla@xxxxxxxxxx writes:

From what the good Dr. has mentioned, he's building loosly coupled
coils, but they are also running closer to Cres by about 18% than the
standard 1.6 x Cres, so his cap voltage is getting to potential
sooner and bps is a little higher.


In that case then other folks who run at higher bps using pigs
or PT's, or NST systems with close-set gaps, should see this
same effect of being able to lower their secondary until the
streamers get shorter without getting racing sparks
(at least up to some power throughput level).  Has anyone
else noticed this?
I haven't noticed it, but again, I haven't specifically tested for it. I don't discount it, but I don't understand the mechanisms that would cause this. I believe D.C. rigs up his coils to adjust the sec vertical position while running, so he would definitely have the ability in that scenario to make the observation. Actually, that is probably something he observed after doing just that with his coils. I've also gathered his coils are high inductance. For example, my little 4.5" coil is only 895 turns with 24 awg. D.C. would likely add two or three hundred more turns and use a smaller gauge wire. This may be a phenomenon for high L coils. I guess only D.C. could say if he's done the same testing with lower turn coils.

I agree that coils which use a smaller bang size with higher
bps should be less likely to form racing sparks for a given
streamer length.  Also tighter coupling should be safely
achievable.  It should be possible to get longer sparks
from a given secondary coil and a given toroid size using
small bang/higher bps also.  This is because smaller
bang/higher bps systems develop spark length more via streamer
"growth due to fast repetition", than via bang size.  However
the spark length for a given input power tends to drop as the
bps rises past some rate.

Yes, when multiple breaks per half cycle are in process, gap losses in the form of heat I think are the main reason. Sparklength also drops when the cap is too large for the tranny to keep up. Large coils get to big sparks very fast due to the current available to the streamer to keep the streamer tip hot as it incinerates it's way through the surrounding atmosphere. (by "hot", I simply mean at required potential). Smaller coils are easier to physically see leader growth, but I don't know that coilers actually observe it. It occurs immediately, but there is also a heating gap which is stealing energy at the same time. Because of the gaps direct influence here, I suspect many coilers actually observe a decrease in sparklength (if they are simply turning the switch on and trying to observe leader growth).

Perhaps you could add a feature to your excellent JavaTC
program which would predict the k point where racing sparks
would occur for a given coil, power level, bang size, bps,
toroid size, etc.  It could get tricky, especially since racing
spark causes may not yet be fully understood.  Still some
empirical info might be able to be utilized with multi-dependent
factors, etc.  The study of such things might lead to new
insights or discoveries in that area.
Yes I could, but there is nothing to add.
We have a lot of theory and no real test data. Even empirically, I think we are shooting in the dark. Granted, there is window we already know of, but that window in the case of coupling is massive in my mind. Some 2-coil systems can run relatively high k (0.25) and others just can't for whatever reason (and maybe can't get beyond 0.1). I agree it would be fantastic to predict this, but I think it would take a TSSP type effort to accomplish and gentlemen like Paul, Gerry, etc. who have that special ability to coordinate such a task.