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Re: Spice simulation pictures
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Hi GL,
I have never tried to closely model a TC. I suspect the distributed
capacitance (self capacitance)
is probably overshadowed by the addition of a lumped capacitor at the end.
I wanted to try a 1/4
wavelength xmission line, but couldn't get it to simulate. (step size to
small)
A good question is; how much C becomes to much? I have heard of some very
large toroids on some fairly
small coils. I doubt if spice can answer this question, I will however play
with it to see what happens.
Dave (flaming stones as necessary)
----------
> From: Tesla List <tesla-at-poodle.pupman-dot-com>
> To: Tesla-list-subscribers-at-poodle.pupman-dot-com
> Subject: Re: Spice simulation pictures
> Date: Wednesday, October 09, 1996 11:58 PM
>
> >From lod-at-pacbell-dot-netWed Oct 9 22:54:10 1996
> Date: Mon, 09 Oct 1995 21:26:28 +0000
> From: GE Leyh <lod-at-pacbell-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: Re: Spice simulation pictures
>
> Dave Huffman wrote:
>
> If you visit ftp://d0huff.fnal.gov/ftp you should find the JPGs
> > along with the spice demo I used. The schematic/spice file is there
>
>
> Nice simulations! I was wondering if you have tried to more closely
> model the secondary coil, that is to represent the self-capacitance
> as distributed along the secondary rather than as lumped at the end.
>
> I've been playing around with PSPICE, and I think that I might have
> an explanation for why larger toroids yield better output. This
> effect has been observed empirically by many coilers, including the
> folks at the TCBOR, and has confounded me for quite some time, since
> if you add capacitance to the output the voltage there must decrease,
> if energy is to be conserved.
> As it turns out, a Tesla Coil will only act like a resonant xfmr if
> the sec capacitance is concentrated at the top, just like in your
> PSPICE model. By contrast, if you distribute the capacitance evenly
> over the sec coil then it starts to behave as a tapered transmission
> line, which produces less output. A tapered xmsn line is not as good
> because it always stores at least part of its energy in the magnetic
> field, and so never at any instant in time is all of its energy
> present solely in the electric field, where it would produce output
> voltage. So by adding more and more capacitance to the top, the
> currents at all points along the coil are brought into phase,
> yielding the best output voltage. More C past this point should
> start to degrade performance.
> How much C is optimum? Still working on that one, but it's probably
> more than an 'proportionally sized' toroid would provide.
>
> -GL