Hello Ken,
I've devised a spark model, which might be able to reproduce
qualitatively, what Steve has posted.
http://4hv.org/e107_plugins/forum/forum_viewtopic.php?156391
It is as yet in an alpha stage, especially the arc capacitances probably should be
reduced by maybe a factor of 2. Also the model is based on measurements,
which used a breakout point. In your case, where you have a large toroid
without one, breakout will be considerably delayed and you must expect
quite a different behaviour of your coil before and after breakout has happened.
HTH, Udo
----- Original Message -----
From: "Steve Ward" <steve.ward@xxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Sunday, November 10, 2013 2:24 AM
Subject: Re: [TCML] SRSS anyone? Anymore?...
> Hi Ken,
>
> I think Single Resonance SSTC is still a viable option for big sparks, but
> a very important consideration is the secondary "impedance". Lowering the
> secondary impedance will raise the system power capability (when faced with
> a plasma load), which many folks find counter-intuitive. Yes, dropping
> Lsec and raising Csec will both help deliver more power to those sparks,
> assuming a constant coupling and primary inductance and drive voltage.
> Simulations suggest that going to Csec of hundreds of pF (much bigger than
> any toroid might provide) can make a *very* powerful SSTC, provided you can
> drive it. The reason this works is because the secondary "loaded Q" is
> increased, so the result is more voltage gain, because there is simply more
> energy stored in the secondary. This effect will not make sense in
> simulation unless you include some sort of spark load (series R and C to
> ground).
>
> I'll be interested to see the results of your setup, its got a nice big
> toroid so that should help.
>
> Steve
>
>
> On Fri, Nov 8, 2013 at 1:04 PM, Ken Herrick <kchdlh@xxxxxxxxx> wrote:
>
>> Greetings-
>>
>> Single resonance still holds an appeal for me--in part since Tesla
>> himself, with the benefit of solid-state technology, would surely have
>> favored it. He didn't, after all, want sparks: he wanted to transmit
>> power, not into wasteful sparks but out to the populace at large.
>> Cockamamie idea, of course, and he and his investors lost a bundle, but he
>> was still a genius.
>>
>> So here's what I'm working on--after some years' hiatus. To produce
>> sparks, of course, not radiate power.
>>
>> Based upon my original notion, which worked but in hardware I made
>> hopelessly complicated: 8, 1000 uF/450V capacitors arrayed together with 8
>> power MOSFETs in a ~12" diameter "ring" arrangement incorporating the
>> equivalent of a 6-turn primary coil. The capacitors to be charged to
>> full-wave-rectified and doubled mains voltage. This I've built and,
>> driving it temporarily with 2 signal generators (to provide for
>> pulse-bursts) and so far only at ~40 V charge, I find that it appears to
>> work as simulated. The scheme is for the MOSFETs to connect 4 of the
>> capacitors in series with the coil during each 1/2 cycle, at the
>> secondary's Fr. That yields, in simulation, ~240A p-p primary current at
>> full capacitor voltage of ~300. I've devised also a simple
>> constant-current capacitor-charge circuit so that I won't pop a circuit
>> breaker trying to charge 8000 uF (plus another 2000 for the doubler) right
>> off the mains from a cold start.
>>
>> The 12" x ~39" secondary coil I'll use is left over from my prior
>> attempts, along with its 6 x 24" Landergren toroid. I have another,
>> taller, coil as well.
>>
>> But in simulation I also found much that I wish I'd found out before: 1.
>> All capacitors may be charged directly in parallel, with the inclusion
>> only of a single 10 mH isolation inductor between the groups of 4. 2. All
>> MOSFET sources may be (and are) tied together. 3. Each 4 drains may be
>> (and are) tied together. And 4. All 8 MOSFETs may be (and are) driven from
>> a single (D44H8/D45H8 H-bridge) source. I've built the H-bridge and it
>> seems to do the job. Now I have to build the l.v. signal-processing part,
>> which takes secondary-return current and amplifies and gates it to provide
>> the MOSFET drive. I've so far simulated that successfully; it requires
>> only 3-4 CMOS DIP ICs + the usual small parts--plus a l.v. power supply, of
>> course, which I also have left-over.
>>
>> So circumstances allowing (I'm 85), I'll be making sparks again before too
>> long. Since I won't use a breakout-point, the sparks very charmingly will
>> dance all around the toroid (as they did before at 20/second or so), making
>> lots of noise and ozone.
>>
>> Ken Herrick
>> _______________________________________________
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>> Tesla@xxxxxxxxxx
>> http://www.pupman.com/mailman/listinfo/tesla
>>
>
>
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