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Re:

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Chris,
The value of cap is determined by your transformer and type of spark gap and is based on the value of cap (Cres) that resonates with your transformer at the line frequency. The following formula determins the Cres: 

Cres (nf) = 10^9 / (2*pi*line_freq*Zxfrm)

Zxfrm = Vs_oc / Is_ss    (impedance viewed from the secondary side)
For a static spark gap, we recommend a larger than resonant (LTR) value of 1.6*Cres. 
For a 120BPS SRSG, we recommend a LTR value of 2.8*Cres

These ratios (1.6 or 2.8) are based on computer simulations.
You will need the parameters of your transformer (name plate data is OK, measured is better). A 15KV 30ma NST would have a Zxfrm of 15000v/0.03a = 500000Kohms which is mostly inductive reactance due to the current limiting shunts of the core. 

Gerry R.





Original poster: "Breneman, Chris" <brenemanc@xxxxxxxxxxxxxx>
How do you arrive at the conclusion that .01uF is almost exactly right for a static spark gap? Is there some way of mathematically calculating this or is it purely experimental? And is this dependent on voltage or other factors? 

Thanks,
Chris


-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Fri 1/5/2007 12:53 AM
To: tesla@xxxxxxxxxx
Subject: [BULK][Spam]Re:

Original poster: "Drake Schutt" <drake89@xxxxxxxxx>




Hey well tomorrow im going to buy a capacitor of ebay i think .. and
well i had already bought one a 20kv cap at .1microF... my 12kv 30 ma


First off 0.1 uF is wayyyyyy too big for a 12/30 NST with a static
gap.  If I remember correctly, the correct (LTR) value (static spark
gap) should be almost exactly 0.01uF.  Regardless of the voltage
rating, thats just too big for your coil.  period.  I might try and
sell it on ebay if you havent fried it, as that is a fairly
substantial capacitor.

nst cuts out via the current limitter i think, only when i try and
use it in parrelle and well i think thats cuz it may be a dc cap and
the dieletric is to weak to be across the leads but when its in
series it works great!... has any one else ever had this problem


Not familiar with what your talking  about. do you have an  MMC?

??... the one im going to by tomrorow is 0.03 uf at 33kv i think that


0.03uF is still too big....33KV should be good regardless of AC or
DC.  DC-you should get one about 3xvoltage of xfrmr

it may be ac for sure but i dont know and well is it worth my time if
im already having trouble... i have been having a hard time with
the cap would either of the ones i may have be ok or am i better of
making my own if so what one is the best to make?


I recommend  looking at  the program wintesla or going to
<http://deepfriedneon.com>deepfriedneon.com and look at the MMC
calculator.  use Cornell-Dublier 942 series capacitors.  search on
<http://digikey.com>digikey.com, ask the list, or go to ebay....

good luck,
Drake Schutt

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