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Re: Spice simulation pictures
Tesla List wrote:
>
> >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
Greg
This discussion seems to infer that the length of the TC when using the
transmission line analogy is something other than 1/4 wave long. My
understanding of transmission lines is that he energy transmitted down
the line continously transfers between the magnetic field and the e
field. If the TC secondary is indeed 1/4 wave long then it appears to me
that it would certainly be possible to have all of the energy in the
transmission line concentrated at the top of the secondary in the
e-field without the need for a large toroidal capacitance. A previous
discussion has touched on the need for a physically large discharge
discharge electrode to prevent premature breakout so I won't go into
that here, but if a way could be found to make a true 1/4 wave secondary
without the need of a toroid to tune it AND a way to prevent premature
breakout without a large electrode our TCs might end up looking entirely
different.
Comments and flames, please
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