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Re: Toroid Modeling One Last Time



Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi John,
Comments below:

Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<FutureT-at-aol-dot-com>
>
> In a message dated 9/3/01 2:44:39 PM Eastern Daylight Time, tesla-at-pupman-dot-com
> writes:
>
> > Hi All, (for those interested)
> >
> >  I put up another graph to show the change in capacitance since I've
> >  corrected the positive values while back calculating the toroid
> >  capacitance. Detailed specs are at the bottom of the graph.
>
> Bart,
>
> Your chart shows the percentage C reaching about -100% as
> the toroid gets quite large in certain cases.  Does - 100% mean
> that it has no capacitance left at all?  Also, the chart shows that
> percentage C gets less and less as the toroid gets larger, I
> would think the percentage would get larger as
> the toroid gets larger, because the secondary would then have
> a relatively small effect.  I may be misunderstanding something.
>
> John Freau

C reaching -100% is a negative value and indicates the capacitance doubles
at -100%
(because this is a graph of the percentage of top capacitance reduction).

For example, for the 1" minor 16.5H row, the first value logged is 70%. This
indicates the toroid capacitance not seen by the resonator is 70% of the
isolated
toroid capacitance. As the major diameter is increased, this percentage
decreases
and top capacitance therefore increases with diameter. At 0%, the top
capacitance
equals the free-space isolated capacitance of the toroid. As the diameter
continues
to grow, the capacitance continues to increase and this percentage goes
negative
because it is directly used to back calc top capacitance from frequency values
modeled.

I can see that this will be difficult for others to visualize the way I do. The
reason I started this modeling was to look at how much change the toroid
size and
proximity varied top C (thus I've been thinking in terms of percent
capacitance),
but I think maybe I should plot top capacitance the next time I post data. This
will probably clear up and confusion.

Take care,
Bart