Re: Magnifier Driver coil design

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Steve Ward <steve.ward@xxxxxxxxx>

Hello Mr. Conner,

Yes, im looking at about 500 turns on my secondary winding now at a
nice diameter of 12" or so.  Insulation will be a real trick, but i
believe (at this point in time) that it is the only way i can achieve
my desired coupling of about .25 (thats with a K=.5 between the
primary and secondary).  Higher coupling generally works better in
DRSSTCs hands down!  Firstly, it reduces primary current considerably,
secondly, it increases spark length!  It looks like a K of .3 would be
about optimum i think, but thats quite difficult to achieve and still
produce long sparks.  I was hoping there would be a trick to using the
magnifer to increase the over all K, but from my few "on paper"
designs, i dont see that really happening.  Instinctively, i feel im
pushing the insulation boundaries just has hard trying to arrive at
the same K of .24 with my little magnifier.

And as to what mode im running the magnifier in?  Umm, if you can
explain (in a language i can understand) how i determine that, then i
will tell you.  Otherwise, im tuning the primary as low as it goes and
i get breakout at about 50%+ voltage input.  Pushing it so that it
just barely stablizes at full power seems to get the best spark
lengths (40" now).  At the lowest tuning, the currents seem
predictable and the coil is generally well-behaved.  At higher
tunings, i get sort of a "notched" primary waveform, where the current
peaks after maybe 15 cycle at a low current (about 100A) then dips
near zero, then rises about 4x as high in another 20 cycles or so!
And when the streamer connects to ground, this last big rise seems to
climb greatly (above 500A i recall).  With the very low tuning the
current rise is completely linear, and usually only falls off near the
end, and even with heavy ground strikes does it ever approach the
current level it should obtain if the end of the bang continued to
grow linearly.

Steve Ward

On 4/18/05, Tesla list <tesla@xxxxxxxxxx> wrote:
> Original poster: "Steve Conner" <steve.conner@xxxxxxxxxxx>
>
> Hi Steve
>
> Your DRSSTC magnifier stuff looks great! I like that bit of math you did
> that suggests you want a much higher inductance secondary coil than folk
> normally use (none of that hookup wire business)
>
> The magnifier with primary current feedback can end up at any of three
> possible resonant frequencies. One of them (afaik) will be at a frequency
> close to the secondary's own resonance and develop most of its voltage
> across the secondary coil. Do you know which of the three you're operating
> at? I guess tuning the primary low is helping to persuade it onto the lowest
> frequency (which I reckon is the best one)
>
> Steve Conner
>
>