Re: Capacitor value not clear yet.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Bart Anderson <classi6-at-classictesla-dot-com> 

Hi Luke,

Tesla list wrote:

>Original poster: "Luke" <Bluu-at-cox-dot-net>
>Thank you very much for the replies on the toroid size question.  I will 
>have to digest more of that after I tackle a two fold question that was 
>brought up as a result of your replies.
>
>Question 1:
>I was planning on 36" arcs based on the formula I found somewhere
>[]
>where k is a value taken from a chart based on secondary dia.  in my case 
>was .85.
>1800 watts  (2 nst's 15KV 60mA ea. Totaling 1800 watts)
>is this figure way off?
>The formula given to me in the toroid replies was
>spark length (inches) = 1.7*sqrt input power (wallplug watts)
>
>Which is the correct formula to use for an approx.?

The 0.85 chart sounds like the chart Dr. R put out. It is based on John 
Freau's approximation of 1.7*sqrt(wallplug watts). The 0.85 factor is based 
on the diameter as far as the efficiency's of input watts to output 
sparklength which Dr. R. has found, and is probably a good approximation. 
Although the chart may be updated in the future, it is still a good 
approximation.

>If I was going to drop to a single 15Kv 60Ma NST could I expect to 
>generate 3 foot arcs?

Probably between 40 and 50 inch arcs depending on your system efficiency. 
Two NST's would get you about 60 to 70 inch arcs.

>Question 2:
>I would like to keep the discussion on cap selection limited to NST's 
>since that's what I intend to use and to keep from getting too much info 
>for my tiny little brain all at once.
>
>I understand the idea of resonant rise in the nst.  Or at least enough to 
>see what you mean.
>The question is will the LTR cap (lower reactance) draw more current from 
>my NST? Say a 15 60.
>I was under the impression they were current limited and no more than the 
>rated 60mA would be drawn.  Resonant rise plays a role in this?

They are internally current limited. If the cap is resonant with the NST, 
the reactances offset for maximum current. If the cap is LTR, the 
capacitive reactance dominates. In the case of an LTR cap, the cap voltage 
will be lower (about 70%) assuming 120 bps. The NST is limited and can only 
charge a given cap size so fast. Adding a larger cap will simply take 
longer charge to a given voltage (the charge slope over time).

>Someone said that the current in the primary circuit can be in the 
>hundreds of amps?  If so where in the -at-#$-at-#-at-~! Does it come from?

That's instantaneous amps, or the current at the very instant the cap 
voltage releases it's energy. Of course, as the cap voltage swings up along 
the first 1/2 cycle, the current swings down. The average current of course 
is much lower, but, you sure wouldn't want to grab ahold of a charged high 
voltage cap, would you. It would hurt! (it does hurt!!!!).

Take care,
Bart

>Ok maybe I opened a can of worms but id like to know what is happening and 
>why the current can be so high and still not hurt the nst and where all 
>this high current comes from.
>
>Thanx again
>
>Luke Galyan
>Bluu-at-cox-dot-net
>
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