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Re: Sphere/Toroid Comparison Chart
Original poster: "Luc by way of Terry Fritz <twftesla-at-uswest-dot-net>" <ludev-at-videotron.ca>
Hi Matt, Kurt, all
Tx guy, both of your answer are logical, I know that
electrostatic equations are not particularly easy .... To have a
final word on that we probably need measurement and if Matt
theory is good; measurement at high voltage ( not sure about that
but I think the repulsive force could be higher at higher voltage
pushing the charge farther on the exterior ???).
P.S. I need to try to understand the electrostatic equations ;-)
Tesla list wrote:
> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> In a message dated 5/8/01 8:17:07 PM Eastern Daylight Time, tesla-at-pupman-dot-com
> > Original poster: "Luc by way of Terry Fritz <twftesla-at-uswest-dot-net>" <
> > ludev-at-videotron.ca>
> > Hi guy
> > I post again the same question: If you look at the chart you'll
> > see that until you hit 18" of exterior diameter the toroid with a
> > thickness of 4" have more capacity than one of 6" thickness.
> > Please could some of you explain to me how a toroid with an area
> > bigger could have a smaller capacity. I already know that the
> > surface facing the center ( the hole of the donut ) don't
> > participated as far as the exterior. But the exterior of a 6"
> > thick toroid is bigger than the area of a 4" one.
> > Tx
> Hi Luc, All!
> I was wrong about the C-C diameter. It is actually the exterior
> diameter. I believe the mystery of the smaller toroid can be explained like
> this: For a given major diameter, the toroid with the larger chord will have
> a smaller inner diameter, meaning the curvature around the donut hole is
> tighter. For the smaller inner diameter of the toroid with the larger chord,
> there is greater repulsive force between the charges on the inside curve
> which reduces the effective capacitance until that inner diameter becomes
> large enough that the effect is negligible. The smaller the inner diam., the
> more distorted the charge distribution. A 14" outer diameter toroid with a 4"
> chord (6" id) actually has more of its surface at a greater distance from the
> center than one with a 6" chord and 14" outer diameter (2" id).
> The formula, as an approximation, also allows for negative inner diameters to
> be computed, which is of course, silly.
> Matt D.
> Original poster: "Kurt Schraner by way of Terry Fritz
> Hi Luc, Bart,
> ...you are right Luc, of course! - I did an E-Tesla6 calculation for a
> small coil (2"/10" secondary), supposing a 12"/4" vs. a 12"/6" toroid,
> and got:
> Problem: Medhurst E-Tesla6 Diff=~
> d1 d2 C.bert.P. C.sec. C.total C.toro Fres
> (inches) pF pF pF pF kHz
> 12" 4" 13.262 4.153 15.116 10.963 522.27
> 12" 6" 11.585 4.153 16.350 12.197 502.17
> Up to now, I was very close to the measurements on my coils, with Bert
> Pools equation. But those were not in the same range of toroid data. So,
> reading your first poster, was not recognized well enough (by me). I
> guess, we are just outside of the validity limits for the (probably-; if
> Bert is reading, he might comment!) semi-empirical Bert Pool's equation.
> This equation may well be continued to use in "normal" TC-design
> procedures, but when it comes to somehow extreme toroids or toroid vs.
> secondary situations, not be the method of choice. The real things are
> something like the super-cool measurements of Bart Anderson, which
> obviously support the use of E-Tesla6. More of this kind of
> measurements, together with the outcome of the TSSP, will probably lead
> to design procedures, which are more precise, but, perhaps, more
> important: applicable to a broader range of TC-parameters.
> Kurt Schraner