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Re: Sizing the toroid to the coil, was Effects of the size oftoroids
In a message dated 00-03-06 18:57:55 EST, you write:
<< Original Poster: "Barton B. Anderson" <tesla123-at-pacbell-dot-net>
> Original Poster: FutureT-at-aol-dot-com
> Hi John,
>snip
>2.8 x CSelf was the result of the best performing coils (performance is
> power in
> vs. spark length - as we both agree on) and the relationship of Ctop to
Cself.
> Yes, this was an average, but more importantly was how little the
relationship
> varied on these best performing coils. One can also see the relationship in
> inductance if we go the other route. The CSelf value is used in my spark
length
> equation as well as bang size and more importantly, the effective EPS
> ("effective" energy per second - which is based on the energy available at
the
> bps and cap size in relation to the input power). This equation takes into
> consideration the total capacitance and top capacitance as 2 seperate
entities.
> The top capacitance is a required value for spark length. I like it because
> at a
> glance, coilers with under-developed Ctop always post small spark lengths
> compared to what input power says they "should" acheive and my equation says
> "yes, it should only be this small". snip
Bart,
I think that Cself should be as small as possible compared with
Ctop within reasonable limits. If we didn't have to worry about coil
breakdown, we could make our secondaries even smaller, and put
more power into the topload and into the arcs. I see the Ctop/Cself
ratio as being simply a practical consideration of how small a coil
can be for a given power level. (we must consider the losses too.)
I agree that the ratio is important,
but rather than saying that a certain ratio is ideal, i would just say
the the ratio should be as large as possible without causing
breakdown of the coil, and without causing too much loss.
>I would like to take it a step further and create something that can't
become
> rediculous. This is harder than it looks. I guess if we had data on coils
built
> out of the realm of "normal size", we could get there. But your equation
> and mine
>are both based on real world coils and in the most part, the coils are
> similar in
> size. In most instances where coilers present their stats and arc lengths,
our
> equations are within only a couple inches of each other, but sometimes,
> there are
> situations where a coiler is having problems based on simple components,
toroid
> sizing, tuning, coupling, etc... CSelf is just one area that helps me
consider
> the top load portion of a coil. Of course, "experience" is always the
driving
> factor that says yes - this is the coilers problem or no - it's something
else.
My formula for spark length vs. power is only for optimally designed
(or at least pretty good) coils. In this sense my formula is not a complete
formula that takes into account the many variables in TC design. This
is at the same time both the weakness and the strength of the formula.
It is of course possible to create new formulas that take many other
factors into account such as the toroid size, losses, charging efficiency,
C ratios, Z matching, bps, etc. It would be interesting to create such
a complete formula.
> So, yes I agree about the importance of bang size and this is "most
definately"
> taken into account. But also, CSelf and Ctop are necessary because the
> capacitance of Ctop and the ability of the coil to charge Ctop is "all"
> imporant
> if we are talking spark lengths. I bascically use the total capacitance of
the
> entire system and then equate how Ctop "weights" the coil for spark length.
> Heck, it's almost like the variac post where there is a "sweet spot". I
think
> there is
> a "sweet spot" for Ctop and the total capacitance. My personal sweet spot
is a
> 2.8 factor, but this will vary from coil to coil by some degree - I just
wish I
> new what the variance actually is.
It's true that the C ratio is important, but I don't think there's a sweet
spot
except from a practical standpoint that a small coil will breakdown if too
much power is applied. If a small coil could be built using special types
of insulation that would prevent breakdown, then the Cself could be made
smaller, and the coil would benefit. I agree that a certain ratio may be
best from a practical standpoint, but does not derive from first principles,
except perhaps indirectly....for instance in a very small coil, the thin
wire may create extra losses. We are forced to compromise. In a
magnifier the resonator can be made extra small, and this may give
an extra benefit by permiting a much greater than normal C ratio as
suggested by Antonio.
In many ways I agree with what you are saying. It is likely that your
ratio of 2.8 is a good one for typical practical coils of today.
Cheers,
John Freau
> Bart
>>