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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
>>