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FW: The Next Coil (best place for "C")




From: 	FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
Sent: 	Wednesday, July 30, 1997 3:44 AM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: The Next Coil (best place for "C")

<< I agree with your recent comment Greg of how stepped leader formation can
be
> enhanced through support of a large topload C where the energy is available

> without series inductance right there at the base of the ionization 
> channel.  I've written a comment about exactly that somewhere in the 
> recent past.  I also made a post a while ago rambling about how the local 
> air along the streamer which stays ionized after the streamer 
> extinguishes, acts more than like a momentarily persistent pathway 
> upon which the next TC output pulse will instantly fill and then 
> extend through stepped leader action (although I used the term dart 
> leader because I am old and confused), but I also went a step further 
> and postulated that this locally ionized pathway surrounding the 
> extinguished plasma channel might actually be storing energy which 
> becomes added to following Tesla coil streamers that go this route 
> instants in time later.  The streamers which follow this channel as 
> we know go well beyond the distance records made when the streamer 
> completely changes direction and starts new pathways.  I received 
> absolutely no comments on this idea. 

Robert,

I for one, enjoyed that post of yours about the energy being stored in 
the arc channel itself.  Lots o' creative thought in that one...it was one
I had to "mull" over in my mind.  Probably lots of folks were "mulling"
rather than responding.  I thought I had responded, but I guess not.
Your posts always make me think, and require a certain amount of 
mulling over in my mind  :^)  Thanks for the comments here, which 
support what Greg just posted also.
 
> The energy which is stored amongst the turns of the secondary in the 
> self-C is not available to the streamer the same way nor as 
> immediately.  The energy stored nearest the topload will be available 
> first, but not as soon as that from the topload itself.  Like a 
> stretched out pulse, the self-C energy will be communicated from 
> secondary coil regions progressively further down this helical delay 
> line to the top terminal when a low impedance ionization channel 
> calls for it.
 
> The way this slower current helps in streamer growth 
> and maintenance is another question.  Perhaps it does not aid in 
> streamer growth at all but in fact is responsible solely for channel 
> maintenance after it is laid out by the fast currents available from 
> the topload. 

Interesting question about which energy supports streamer growth and
which supports channel maintenance.  Nice "nitty gritty" questions 
that we need some nice experiments to verify.
 
> Also responsible for channel maintenance is the wave 
>which propagates up from the bottom of the secondary upon each firing 
>of the break, and successive beat envelopes if any.  This energy from 
> the source would be mingled and become one with the discharge pulse of the 
> self-C of the secondary coil (delay line), I would think, i.e.,  you would 
> not be able to distinguish the two as separate entities in the scoped 
> output waveform.
 
> With the hands-on experience I now have  I no 
> longer accept the statement handed me initially that self-C robs us of 
> output power.  The picture is much more complicated than that and I am
still 
> trying to piece it all together.  I have not yet had the advantage of 
> any form of coiling or CAD program from which to plug in variables 
> and watch the theoretical results.  So far, if I wanted to see what 
> increased secondary L, or a larger top C would do, I would wind a new 
> secondary or build a larger topload.  The nice part about this expensive 
> tedium is that I now have a good assortment of equipment which is 
> darned handy to have in a Tesla coil laboratory.  

Well, there's nothing like empirical results to support or disprove the
theorizing. 
 
> Malcolm recently commented that the self-C energy is entirely 
> reactive so there is no power loss.  I hope he's 100% right.

I hope so too! 

> I went to great effort about a year and a half ago to put a 15 inch 
> diameter, AWG #8, polythermalese magnet wire wound coil 48 inches long on a

> fiberglass form inside a large 200 gallon steel tank filled with 
> transformer oil.  The performance of this coil has yet to be gleaned. 
> It just doesn't seem to light up like much smaller coils in air that 
> I have built using the same input power.  In 'Fundamentals of Radio' by
Terman
> he mentions how coils may be installed inside metallic housings and that
eddy 
> current losses in the surrounding container will drop to an 
> acceptable level once the radial distance to the containment vessel from
the 
> coil matches the radius of the enclosed air core coil.  My enclosed coil
follows 
> these suggestions exactly.  I haven't had the opportunity to pump 
> enough input power into this resonator to overcome thermal inertia and 
> feel heat on the steel walls or anything, but I have driven it up to 
> about 4 kW CW and 900 VA disruptive style.  In disruptive mode , by 
> observing the discharge to a ground wand it is apparent that there is 
> *a lot* of C being discharged in the resonator's output.  Streamers, 
> although shortened as compared to a similarly powered normal air 
> cored Tesla coil are very much louder and visibly brighter indicating 
> discharge current from a proportionately large self-C.  I get a 
> similar effect when I place an external air-dielectric 100 pF cap 
> built from an aluminum spinning suspended within an empty, grounded 55
gallon
> steel drum on the output of a regular disruptive Tesla coil and retune to 
> compensate for the mucho extra topload C, except in this case I don't
appear to
> be losing nearly as much voltage at the same time.  We understand well that
> topload C foreshortens the 1/4 wave resonator in electrical degrees so that
a 
> lower Vmax is produced at resonance.

This work too supports the view that large toploads, not just large self-Cs 
are needed for strong and long sparks.  Interesting work.

John Freau
 
> Any comments and further opinions to my ramblings are welcomed.
 
> rwstephens
  >>