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

[Miles Mauldin <teslamiles@xxxxxxx>]

Hi Brandon,

From my research it doesn't seen to be really critical to get it exact, just get close.  Keep in mind that most caps have a tolerance of +/- 5 to 20% anyway so you could think you've got it right and still be 20% off the mark.  My plan is to use a few nF above the LTR for an initial static gap with a planned configuration to add a single string of same number caps to reach the LTR for an SRSG. (BTW, my tank will start with 2 strings 15 x .15uF/3kV, then adding a third string of same).

Cheers,
Miles



________________________________
From: Brandon Hendershot <brandonhendershot@xxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Tue, March 23, 2010 1:07:42 PM
Subject: Re: [TCML] How close is close enough? (Primary capacitance)

Hi Brandon,

As far as whether to go higher or lower than the recommended capacitance, If irc, you want to go higher than the desired capacitance because it's easier to take away some of the capacitance than adding some. I don't know exactly how you would fine tune the capacitance, but I assume it involves soldering on an extra smaller cap to decrease the capacitance a bit. Opposed to desoldering and removing a cap from your MMC. Hope that helps.

Brandon, AZ

On Mar 23, 2010, at 8:33 AM, Brandon Garretson <garretsontech@xxxxxxxxx> wrote:

> 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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