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RE: [TCML] Effect of doubling the input current



Hello Bart.
Your reply worried me then I remembered I live in the UK @ 230 volts and 50
hz, so panic over.

Running my static on the two 10/50's to give 10/100 would have a Cres of
31.8 nF over here, so at 21.43nF I am around 60% on the low side. This is
STR to the point of being a bit too much of the 'S' I suspect.

It is obviously that the BPS (up from 90 to 281 in Javatc) has affected
things. As I am not [yet] running a rotary, things like BPS rates have not
been that much of an issue to me -so far. The increased break rate did not
even occur to me when I asked the original question, I was blindly
travelling down the increased 'bang size' road. Of course now it is obvious,
smaller cap  - quicker charge.

I have been archiving tonight to find out any pitfalls of having a much
higher BPS. At the 280 odd level I reckon it's safe for the CD caps and the
NST provided the safety is spot on, and keep run times sensible - only warm
caps acceptable etc.


Phil

PS: BE AWARE EVERYONE
Ran the coil in the workshop and blew the electronics card in the washing
machine it seems. The machine got caught with a streamer, and despite being
unplugged, it was zapped. Wife is ignorant of the real reason so far, just
thinks it is one of those things, best keep it that way.



-----Original Message-----
From: bartb [mailto:bartb@xxxxxxxxxxxxxxxx] 
Sent: 09 December 2008 04:49
To: Tesla Coil Mailing List
Subject: Re: [TCML] Effect of doubling the input current

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
>
>  
>
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
>   


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