Re: Capacitor value not clear yet.

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

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi Luke,

At 06:48 PM 1/11/2004, you wrote:
>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.?

Use spark length (inches) = 1.7*sqrt input power (wallplug watts).

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

Yes, pretty easily if you build things right.  If you did everything 
perfect and used a sync rotary gap, then 50 inches.

>
>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?

Just go by the charts to find the cap size to use:

http://hot-streamer-dot-com/temp/MMCcapSales.gif

These charts are generated by computer modeling:

http://hot-streamer-dot-com/TeslaCoils/Misc/NSTStudy/NSTStudy.htm

Very messy stuff, but the charts are easy ;-))


>
>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?

The NST "slowly" (for electrical things...) charges the cap over say 0.008 
seconds at 60mA so we can multiply those to get 0.000480 amp-seconds.  No 
we quickly discharge it in say 0.000002 seconds.  The current then has to 
be 240 amps.  It is just like slowly pulling back a rubber band and letting 
it go.  We use the capacitor to store the energy up over a long time and 
then fire it suddenly.

>
>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.

The high current never goes through the NST.  It goes through the primary 
cap, inductor, and gap circuit.  That is why that stuff has to be so big 
and beefy.  The NST just charges the cap at 60mA so that is no big deal at 
all as far as current goes.

Cheers,

         Terry

>
>Thanx again
>
>Luke Galyan
>Bluu-at-cox-dot-net
>
>