Re: toroid question

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Mddeming-at-aol-dot-com>

In a message dated 1/23/02 10:15:48 AM Eastern Standard Time, tesla-at-pupman-dot-com
writes:


>
> Hi Godfrey,
>
> in my opinion there is no need to deal with toroids, whose hole in the
> center is <=zero, or very small, relative to the outer diameter. The
> outer diameter is probably choosen in a relation to the size of the
> secondary or to sparklength, in order to get a nice "shielding effect"
> for corona (i remember John Freau proposing D.toroid=~"desired
> sparklength"/2.5), or considering the whole TC in a Pspice-simulation
> for output power and voltage. The diameter of the "cord" should be in a
> relation to the secondary outbreak-voltage (remembering again John:
> d.toroid = "desired sparklength"/10, as a start). But the ROC of the
> torus will never be really perfect, even if having a spun toroid. And as
> soon we get breakout, the toroid will no more be smooth anyway, 'cause
> the streamers and sparks are like "needles", and the jon-cloud may be
> adding capacitance. Personally i try to choose a ratio of diameters, -
> not at all scientifically - , which gives me a good feeling about
> proportions. And this is not one with zero inner hole radius, which
> might typically be not much less than the cord radius.
>
> Anyway i'm keen to see your approximation to the "true capacitance" of
> an isolated toroid, probably with an estimation of accuracy. This seems
> to me of great value, even, if after all, either we may find Bert Pool's
> formula just good for our purpose or utilizing a more elaborate formula
> in our calculations (i.e. spreadsheets).
>
> Cheers,
>          


Hi Godfrey, Kurt, All,
Capacitance is also affected to some degree by what's in the toroid's hole. A
toroid with a "pieplate" center will have somewhat different capacitance than
one with a "spoked wheel", which will be different from one with 3 plastic
"struts", etc.
Matt D.
G3-1085