Re: Toroid Modeling One Last Time

["Tesla list" <tesla-at-pupman-dot-com>]

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

Hi Ralph,
Comments below:

Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Parpp807-at-aol-dot-com>
>
> In a message dated 9/3/01 1:44:40 PM Central Daylight Time, tesla-at-pupman-dot-com
> writes:
>
> <<  http://www.classictesla-dot-com/topc/CTOR-1.gif >>
>
> Hi Bart,

> As the zero line is the x-over point for the isolated free-space capacitance
> of the toroid, how did you determine this value?

For each and every toroid size, I calculate the isolated free-space
capacitance.
There are many equations, but the one I use is
Ctoroid (pF): (1 + (0.2781 - cd / od)) * 2.8 * sqrt(((pi) * (od-cs) *
(cs/2)) / (2))
where cs is cord diamter and od is outer diameter. Typically, we can get
real close
with calculations for the secondary. But as soon as we add a top load, all
bets are
off. The best we can do is measure or look at the few coils in the past
which have
been measured and try to compare. However, if E-Tesla6 can accurately predict
frequency (which I think it can and has on my own coils and others), then
we can
easily model many different coils to get a decent idea of how the toroid
effects the
resonator. It's a matter of comparison between an accurate model and our
typical
(not so accurate) resonator calculations. In JavaTC, I have an input box
which the
user can use to reduce the top load capacitance to more accurately model
the coil
design, but the user has no way to know what to put into this box. That's
part of
the reason for this. I think we have the tools to take step forward in our
designs,
but it will take a lot of work and models to get reliable information.

> You label the y-axis as the Percentage of Top Capacitance. What is that
> value?
> Ctop = ---pF.

Ctop is typically pF, but there are no capacitance values in the graph.
These are
percent values. The table data below the graph is simply plotted.

> You write: "Percentage of toroid capacitance from isolated free-space
> capacitance
> is what is being graphed." Is that the same property as what you have labeled
> on the graph?

Yes.

> And isn't the percentage of deviation the same property as
> shown on the y-axis
> of the first graph?

Yes.

> Would you please indicate the plotted points.

The plotted points are the same points in the table data below the graph. I
just
replied to John F. with an example of how to view this data and I'll refer
you to
that email. But also, I see the need to plot capacitance values in place of the
percent the toroid capacitance is reduced or increased. I think this will
help clear
up the understandable confusion.

> I find this topic very interesting. Lots of learning but too slow.  :-))
>
> Ralph Zekelman

Take care,
Bart