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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