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Re: BIG resonance! - thoughts...
-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Sunday, April 04, 1999 5:34 PM
Subject: Re: BIG resonance! - thoughts...
>Original Poster: Gary Lau 03-Apr-1999 2113 <lau-at-hdecad.ENET.dec-dot-com>
>
>>Original Poster: Jon Rosenstiel <jonr-at-pacbell-dot-net>
>>
>><big snip>
>>
>>Just after I had installed a brand new 6" secondary I got a couple of
>>strikes to the primary while fooling with a small toroid and "poof", there
>>went my 15kV 60mA NST. I tried to rebuilt the 15/60 but ruined one of the
>>secondaries trying to remove it from the core. I couldn't find any more
>>15/60's so I unpotted a couple of 15/30's, removed enough shunts to make
>>them 15/48's and threw them in a oil bath. With the 15/48's in parallel,
>>(96mA), I thought that my present .011 tank cap was too small and better
>>performance could be had by having the "proper" sized cap. (for 15kV -at-
96mA
>>that calculated out to .017uF).
>>
>>I spent quite a bit of time and effort constructing 4 extended foil rolled
>>caps that had a total series value of .006uF which when added to my
>>original .011uF cap gave me .017uF. Imagine my suprise when my coil's
output
>>dropped with the .017uF combination! Couldn't understand why! Then I read
>>your answer to Alex' questions and the light came on!
>>
>>I already had several .008uF-at-5kV caps lying around so I wired them in
>>various series / parallel combinations so that I could test the resonant
>>rise characteristics at various capacitances. It turns out that my 15/96
>>transformer(s) still work best with a .011 tank cap.
>>
>>I fed my transformers 2Vac, got out 250Vac with no capacitor attached. I
>>tested various capacitances and recorded the voltages, (made a nice graph
in
>>Excel).( I can send the graph if you want). All very, very interesting!
>>
>>I then hooked my Tesla tank caps to the transformers and got the
following:
>>
>> C Eout
>>.011uF 1650Vac, (original cap)
>>.017uF 606Vac, (original cap + new .006uF cap)
>>
>>No wonder my spark length dropped! 1650Vac is 6.6 times the 250Vac output
>>that I got with no cap! I hope that the 6.6 times doesn't scale up
linearly.
>>If it does I think that my coil would have self destructed long ago.
>>
>>Now on to that larger toroid and a way to increase the coupling in that
>>never-ending quest to achieve the longest possible spark!
>>
>>Regards,
>>
>>Jon
>
>It sounds like knocking out NST shunts doesn't alter what their
>mains-resonant capacitance wants to be. Perhaps the only way to be sure
>is to feed in a sine-wave function generator and sweep in the
>neighborhood about 60 Hz. I did this with my 15/60 NST and .01uF cap and
>found them to be resonant at 60.5 Hz. Not too far off the mark!
>
>Gary Lau
>Waltham, MA USA
>
This weekend I built a larger toroid and had trouble getting breakout, even
with a bump. I tried opening my gap, (0.280" to 0.336"), this helped
somewhat but still no breakout without the bump. Then I thought I might as
well try using my larger tank cap, (0.011uF to 0.017uF). Lo and behold,
Breakout! The cap, (0.017uF) that wouldn't work before now works! It seems
that even though the 0.017uF cap doesn't resonate as well with the
transformer as the 0.011uF cap the 0.017uF cap in concert with the wider gap
is able to drive more energy through the system. I'm getting larger
discharges that I ever have.
It seems like the new toroid, (6" x 28", 35.43pF), is about the maximum size
that my coil will support. I'm now getting some turn to turn arcs near the
top of the secondary.
Jon Rosenstiel