Re: [TCML] Effect of doubling the input current

[bartb <bartb@xxxxxxxxxxxxxxxx>]

Hi Phil,

If current was linear, we would have expect maybe 50% increase in spark 
length. But double the spark length suggests a couple things. For one, 
the cap is taking advantage of resonant charging. Your 10/48 was about 
1.7 x Cres. With the 10/100 NST, your at 1.2 x Cres roughly. This is 
absolutely taking advantage of resonant charging. The closer you get to 
Cres, the higher the output current. I personally would not go any lower 
than this with NST's. I like to run about 1.3 to 1.4 x Cres, so your 
cutting it a little closer than I would feel comfortable doing. The coil 
will perform very well, but realize that a day may come when all goes 
quiet (but near enough that "maybe not").

The other obvious point is that the 10/48 original situation was on the 
edge of having difficulty in charging the cap. Unless there was some 
ferro resonance occurring (and probably some), the cap would have been 
in the 70 bps range (if a static gap). But running and rsg, simply a 
lower voltage and probably inconsistent voltages at break. This is why I 
say "on the edge". That NST size would have performed better with a 
smaller cap size (about 0.018uF).

But now, the high current is allowing full charge and also pumping in 
resonant charging current into the mix. Makes a big difference!

Bart

Phil Tuck wrote:
> Hello Group.
>
>  
>
> I have a query over charging currents following an exercise on my coil of
> doubling the input current.
>
> I was originally running my old 10k/48 into a 0.02143 uF cap. 
>
>  
>
> However I recently acquired two identical [new] 10K/50 's and tried these in
> parallel for 100 ma.
>
> My coil was already 'ball park' tuned for the 48m/a  NST, when I substituted
> the two new 50 ma NST's. 
>
>  
>
> I left all other settings on the coil alone (apart from making sure the
> safety gap was still appropriately gapped - voltage outputs can vary despite
> what the labels say)
>
>  
>
> I did not expect any really significant difference as it was only the
> current that had increased not the voltage, nor my cap size. 
>
> The 'Freau' formula of Spark length is 1.7 x SQRT(Bang Energy x BPS). Now
> the bang energy [or so I thought] depended on the value of the cap x the
> voltage at the gap squared.
>
>  
>
> As I was still using my original sized CD' MMC caps of  0.02143 uF and not
> the recommended size for 10/100 of 0.0477uF,  why did I get such a massive
> increase in performance. I would estimate the spark lengths are double to
> the 48 ma original NST.
>
>  
>
> If I had doubled the  current  and also doubled the cap size [necessary to
> have charged to them the same level] I could understand why.
>
>  
>
> Is it that my tuning was less than perfect originally and with the 100ma
> NST's it is nearer the mark ?
>
>  
>
> Phil
>
>  
>
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>   
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