Re: [TCML] Secondary Coil: Wire Gauge and Number of Turns

[Scott Bogard <sdbogard@xxxxxxxxx>]

Hi Brandon,
     I think that design looks great for your power level, nicely fitted.
 A note of interest, to "make use of all available primary" another thing
you might be able to do is increase your top load capacitance, this
necessitates using more primary.  Naturally it only works to the point your
wattage can support it, but the top load is one of those areas where a
little variance won't hurt as bad.  As I may have mentioned before I use
the approach (top load pF) <= (0.9*SQRT(WATTS)) to size my top loads, any
bigger than that and your coil can be unreliable, but it gives you some
room for play.  For biggest sparks the closest you can get to that number
is generally best.  Personally I wouldn't worry about it, you can always
size the primary optimally the old fashioned way and then cut off the
excess...  Anyway as I said design looks good, let us know how it turns out!

Scott Bogard.
P.S.  Also, as far as maximizing inductance to increase V out I have two
points.  Vout actually only marginally has to do with spark length, that is
mostly determined by the available spark current, which is dictated greatly
by the top load; and secondly increasing inductance SEC will naturally
require more inductance Pri (or more capacitance Pri) which defeats the
whole purpose.  A System designed for absolute maximum voltage would be a
poor spark producer, as there would be virtually 0 current carrying
capability.  Tis better to design for optimal current carrying capability
and let voltage take care of itself in my opinion.


On Tue, Jul 2, 2013 at 6:48 PM, Brandon Hendershot <
brandonhendershot@xxxxxxxxx> wrote:

> Phil,
>
> >Not too sure what you meant by "(... while keeping the required primary
> >inductance to about 90% of the primary coil's capacity.)".
>
> Basically I was wanting to design the secondary to require almost all of
> the available primary coil when tuned properly.
>
> >It's all about having a balance, that's why using an aspect ratio that has
> >been determined as sensible by countless coilers over the years (4 / 5:1),
> >combined with a turns ratio centred around 1200  (900 - 1500), means the
> >both the secondary inductance and inter-turn capacitance should work out
> ok.
>
> Based on this (and other advice) I'm thinking of making it like this:
> 1237 Turns of 24 AWG, 28" x 6.6" (4.25:1) yielding 54.5 mH Inductance and
> 12.0pF Capacitance.
> Based on popular opinion I believe we can all agree on this being somewhat
> optimal, right?
>
>
> Scott,
>
> >I'm curious where you heard that a higher inductance is better?
>
> The logic behind that was to maximize Vout (before accounting for losses to
> resistance) and minimize losses in the Spark Gap. But now I know that that
> "blatantly isn't" the case when taking into account the consequential
> losses.
>
> >With that said, to answer your question,
> >what do you hope to achieve out of this coil?  Big sparks?
> >Power handling capability?  Highest possible voltage?
> >Aesthetically pleasing?  Wireless power?
>
> I'm a simple man: I just want to throw the longest, brightest arcs I can ;)
>
> >Given you are still in the design phase let me tell you how I would
> >approach it, assuming you were going for maximum spark length and
> >aesthetically pleasing as primary design motivators.  You know you will be
> >using 1,825 watts, so we back calc for spark length and get 72 inches, so
> >we pick our secondary length at 72/2.5= 28 in (a good size from a power
> >handling standpoint, but optimally nice and compact (pretty) and easy to
> >build.)  From there plug into Tesla map and find your wire gauge for 1200
> >turns, try not to fall in love with a gauge before hand, it is just
> >arbitrary, one is not better than the other except that it fits your
> >design.
>
> I've been loosely following this same advice since you gave it in another
> topic of mine a few months back. Turns out I should've been following it a
> bit more closely, that's increasingly similar to where my designs are
> heading!
>
>
> To summarize, what do you all think of the revised design mentioned above?
> Are there any more factors to consider before I commit and start buying
> parts??
>
> Thanks as always everyone,
>
> -Brandon H.
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