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Re: [TCML] How close is close enough? (Primary capacitance)

Hi Brandon,

Cap value isn't terribly critical.  A little too much cap is probably preferable to not quite enough, but that's more opinion than fact.  For my first two tesla coils (pre-TCML!) I didn't even know the value of my homemade foil & glass capacitors.  I just tuned the secondary for best sparks.  Almost any reasonable cap value can be made to work if your primary has sufficient tuning range.  Do try to avoid the mains resonant cap value if possible though.



--- On Tue, 3/23/10, Brandon Garretson <garretsontech@xxxxxxxxx> wrote:

> From: Brandon Garretson <garretsontech@xxxxxxxxx>
> Subject: [TCML] How close is close enough? (Primary capacitance)
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Date: Tuesday, March 23, 2010, 9:33 AM
> Greetings TCML,
> My question today is regarding primary capacitance and how
> much
> headroom we have to play with while still achieving close
> to maximum
> performance.
> Between being a bit of a noob and more than mildly
> math-tarded, I tend
> to rely on programs to do the math for me as well as
> searching this
> incredible forum for posts from people who have encountered
> similar
> problems. But what I have not been able to deduce thus far
> is this;
> How close is “close enough”?
> I feel that Telsamap and JavaTC are very helpful
> applications
> (although they don’t always seem to agree which makes
> things even more
> confusing). They give you very specific data as to what the
> primary
> capacitance should be in any given tank circuit, not a
> narrow range,
> but a seamingly dead-on set in stone number.
> In an ideal world, we could nail that number every time.
> But since we
> (I) live in a much less than ideal world (the real one),
> some of us
> (myself) are required to work with what we have.
> The core of my question is this, how many nf away from the
> ideal
> capacitance can one go before he can no longer compensate
> through
> tuning and still achieve good, if not excellent,
> performance?
> Im sure the amount of leeway would be different depending
> on the size
> and design of the apparatus so let us say we are talking
> about fairly
> conventional, medium sized, NST powered RSG devices.
> To give a specific example, lets say the design on paper
> demands 17nf
> but your cap is 20, same design with a different
> transformer, it wants
> 35nf and the cap you have is only 33.
> Are a few nf in either direction going to noticeably impede
> performance?
> If one had to choose a less than perfect capacitance is it
> better to
> go bigger or smaller?
> Is there a certain percentage, in general, of the ideal
> capacitance
> from which one can deviate were any slight decrease in
> performance
> would go unnoticed? Say +/- 10%, or would it be closer to
> +/- 1%?
> Thanks!
> Brandon, NJ
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