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Greetings again to the Tesla List-
After a 15-odd year hiatus encompassing several failed efforts and some
diverting family affairs, I'm attempting a (final!) resurrection of my
1-&-only SSSRTC. The List's emails seem to have been indicating a marked
decline in interest in SSSR designs but I persevere nonetheless. I like
to think (and I will stand corrected) that it's along the line of what
Tesla himself would have pursued if he'd had the technology. Aside from
PR purposes, Tesla would not have wanted sparks as they are totally
wasteful of radiated energy. Rather, he would have wanted a SR system
brought up to just before spark-breakout (from its "smooth" top
electrode), for maximum radiative efficiency. Altho, of course, the
whole idea was a cockamamie one but that's neither here nor there. From
my Dropbox, here's what the TC looked like originally:
(I'd labeled it as "not ...an artwork" since I've been doing art now &
again and have included it amongst those images). It was a time exposure
running, as I recall, atabout 10 bursts/second. It was hopelessly
complicated and I ended up in apique, long ago, throwing out the entire
primary apparatus.
Same 24"-sq. base-panel(swiss-cheese-like from prior attempts). One of
four new primary modules is at the left, current xfmr at center,
beginning of hand-held control box at right lower (which will have a 3'
neon tube projecting from it to charmingly attract the sparks). Three
l.v. power & control modules, left over from the previous attempt, are
at the 3 corners. Ultimately, the 4 primary modules are to be
daisy-chained, to deliver up to 5 ms bursts @ ~10/s max., of ~+/-100A @
~ +/-1 KVPKapplied, to a ~5-turn primary.
The big blue capacitor is a left-over 4mF, 450V beauty while the white
ones between the two ckt boards form a "snubber" for Vs-dovershoot
between primary-conduction events. The secondary (again, left-over)
just plops down over the 4 blue capacitors, which handily keep it
centered (and it will be kept upright using the same 4 nylon straps as
before). Relatively low secondary voltage along there, so I don't
anticipate a problem.
As I see it (will stand corrected again), it's only a "disruptive"
primary apparatus that can produce materially longer sparks from a given
top electrode; SR won't do it. That's because what's needed for that is
a 1st-quarter-cycle current-rate-of-rise that well-exceeds the rate of
propagation of a spark in air (as well as, of course, exceeding the
resonant rate-of-rise of the secondary itself). That's so that
much-more charge can get crammed onto the top electrode before the spark
has a chance to proceed very far. From my prior experience, a longer
burst-length, e.g. 5 ms, acts to make the spark "fuzzier" but not much
longer. If that's not a fair analysis of what happens, someone let me know.
Here's the simulation-waveforms of 1 module's primary-current and the
MOSFET Vs-d:
The sawtooth is a superimposition of the 2 primary-current waveforms;
the circuit sends 1-way current thru each of 2 coils. The blue wave is
the Vs-d of one of the power MOSFETs, showing ~600V max.
Here, 1/4 of the primary-pairs connects just back to the same module; in
the ultimate hardware, it will make 1 3/4 turns around ~12" diameter and
connect to the module just preceding it (in that direction). All 4 thus
end up daisy-chained, with the blue-capacitor voltages (of up to ~325
each) adding.
Q1 & Q4 are the power-MOSFETs while Q2 & Q3 are part of the
crossover-control circuit. D3, D6, C4 and R6 provide, from the drive
signal, current to the crossover circuit. That circuitacts to keep each
MOSFET off until the gate voltage of the other reaches close to 0. In
addition, since C4's voltage bleeds off rapidly after each pulse-burst,
both MOSFETs are kept off between bursts, through D3 & D6. C2 is the
4mF capacitor.
I add MOVs at the 3 places shown, as precautions. Also, L1, L2, R8 and
the "SIM GND" are included for simulation purposes.
The "SNUBBER" elements plus D1 and D8 act to soak up the (hefty!)
voltage-overshootbetween half-cycles. C3 & C5 do that job while R5
bleeds them off during burst intervals and subsequently.
The MOSFET drive comes from the l.v. processing circuits whose input is
derived from the secondary's return-current, creating the positive
feedback loopto sustain oscillation.
Hope the links get thru intact. Kindly wish me luck...
KCH
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