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Re: Torroid Formula (To Bart + All others)
Hi Tab,
As Antonio pointed out, Ct = Ctop + Cs. The fact that the toroid placed on top
of the coil does change slightly is not a big deal as far as tuning goes. The
change is usually not significant enough. However, when "designing" a coil, the
parameter I would look into is power processed. The higher the power, the
longer the streamers. Higher power allows for a larger Ctop to increase the
level of breakout and acheive longer streamers. If you design Ctop based on
"coil dimensions, inductances, capacitance distribution, etc.." without
involving how much power is to be pumped in, then anything goes - meaning Ctop
may be too small or too large. This is why I was curious as to your "method" of
designing the toroid. I started a design a year ago or so for Ctop based on
energy per second, but ran into a problem with it (I don't even remember what
the problem was) and ended up using an average value based on Cself derived
from emperical data. I've recently discovered this was not a good method. I
don't think the toroid should be so difficult to design on paper, but it has
been. I think to resolve the problem, many test should be carried out on
several coil sizes, several power levels, and several toroid sizes and
surfaces. Until then, I think if one wants to make the toroid "perfect" for the
coil being run, then one should just experiment.
Bart
>
> Original Poster: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br>
>
> Tesla List wrote:
> >
> > Original Poster: "Tabraze Malik" <tab-at-malik13.freeserve.co.uk>
>
> > Now coming to the problem...
> > If you have the secondary coil (which obviously has capacitance) and
> > connect the Torroid to it then basically what you have is 2 capacitors
> > connected in series. The formula for capacitors in series is
> > (1/CT)= (1/C1) + (1/C2).....
> > where CT = total capacitance and C1 , C2 are the capacitances of the
> > capacitors in series (for as many caps you have in series). If you look at
>
> > this formula it's not a big leap of maths to see that the total capacitance
>
> > will be less than the capacitance value of any capacitor in series. This
> > might explain why capacitance goes down when placed on the secondary.
>
> No... The terminal capacitance is in parallel with the self-capacitance.
> Both are distributed capacitances from the top of the coil to the
> vicinities. Ct=Ctop+Cself. There are small variations in Ctop and Cself
> due to the interconnection, but this can be ignored as a first
> approximation.
>
> Toroid please, not "torroid".
>
> Antonio Carlos M. de Queiroz