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Solid state t.c.'s

A few more comments/responses:

Alan Sharp:  The patent has been approved but not yet issued (it's
"pending").  As soon as it's issued I'll post its no. on the List.  As to
availability of my circuit:  As I have said, I'll want to first prove
out--more thoroughly, tho I've done this already with prior
manifestations of my scheme--the notion of incorporating more transistor
pairs/power sources into my 1-turn loop.  Then I'll clean up my
documentation & offer it as a package.  From the patent, of course, one
can understand the basic scheme--but, believe me, there's lot of sweat
involved in getting from what the patent describes to a finished article!
 I've blown my share & more of power MOSFETs.

"B2":  

I drive each 6 pair of MOSFETs in push-pull parallel with circuits of my
own devising.  For each 6 pair, a 6-transistor H-bridge is driven from a
2-phase logic-level pulse-burst signal from the single gated amplifier. 
That, in turn, drives a 2-transistor crossover-control circuit via an
isolation transformer.  The output of that circuit drives the 2x6 MOSFETs
in push-pull.  The gated amplifier also drives however-many other
H-bridges are in the circuit; my current design will incorporate 6,
total, driving two 1-turn current-loops arrayed in parallel in a flat
configuration at the bottom end of the secondary, with each loop
incorporating 3 pairs of MOSFET/power source circuit boards arrayed
around the loop.

I've tried to stay away from surplus in this project so as to make it
easier for others ultimately to follow my plans & get the parts.  Absent
surplus, those humongous MOSFETs are pretty expensive and not, perhaps,
readily available.  Also, they are somewhat slow: at 125 KHz one only has
a 4 us on-time for each half-cycle.  Out of that, it's not too good to be
taking 1 us or so to rise & fall.

I shouldn't have written 100/s as a max. spark rate.  10/s is more like
it, with a 6 ms on-time:  At 10/s, that's 100 ms between pulse-bursts. 
6/100 = a 6% duty cycle.  Multiplying the 250 A pulse-burst current I
presently see by that 6% yields 15 A line current from the (U.S.) 115 V
mains, to recharge the power-source capacitors between sparks.  That's
about all my circuit breakers will handle.

When I finally get to realizing the final configuration, I'll be pulsing
some 750 A of current.  So either I cut that maximum spark rate to 3/s or
so or I diminish the pulse width.  I like the 6 ms because it gives time
to fatten up the spark and cause it to branch.  I suspect that, all else
working out OK, I'll be happy with big, fat, loud sparks but at a mere
3/second.  Especially when I can just plug the machine into a wall
socket--and not worry about getting fried if I inadvertently contact the
primary.  I may not have made clear that at no time does any voltage on
any part of the primary apparatus, as measured to ground, exceed 160 VDC
or 320 VAC at 125 KHz--with the latter only occurring during each 6-ms
pulse-burst.

Were I of a sardonic turn of mind, I might have commented that my scheme,
while not perhaps employing 21st-century hardware, surely employs that of
the 20th--in contradistinction to most of you other coilers who are back
in the 19th.  But I would never say that.

As to trying this with another secondary, I have not done that.  I don't
have one, for one thing: I have just the pie-wound one.  There's no
reason at all why it wouldn't work fine, as long as its resonant
frequency was not too much higher than 125 KHz (so that the pulse's
on-time would not become too much shorter than the 4 us).

Someone else commented that perhaps my MOSFET scheme could be scaled up
for larger coils.  No reason why not.  One can pump X-number of amperes
through a 3' diameter current loop just as readily as through a 1' one. 
Since the loop impedance would go up, more hardware would be needed to
get the same current, of course.  And a larger secondary would exhibit
quite a bit lower resonant frequency, so pulse width would be longer, so
slower/cheaper MOSFETs could be employed--but more of them ("there's no
free lunch").  Such a coil would more efficiently be operated (in the
U.S.) from a 220 V split-phase mains, which most people have, I think. 
Each current loop, of a pair of them in parallel, would be powered from
one side of the line, keeping MOSFET and storage-capacitor voltage
ratings still at reasonable levels (500 V for the MOSFETs, 200 for the
capacitors).

Anyone hot to trot?  You'll have to wait a while, at least for my plans;
perhaps 6 months.

Ken Herrick
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