Re: Where am I going askew ?

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

Original poster: Esondrmn-at-aol-dot-com 

In a message dated 10/14/03 8:22:39 PM Pacific Daylight Time, 
tesla-at-pupman-dot-com writes:


>Original poster: "Christopher \"CajunCoiler\" Mayeux" <cajuncoiler-at-cox-dot-net>
>
>Ok, I'm getting widely varying results between calculation
>methods, and so I'm hoping I can list what I have to work
>with, and someone here can tell me what would be right for
>the primary and secondary coil paramiters.
>
>To work with...
>
>   * 15kv/30ma NST (with "terry filter")
>     http://msbdatasystems-dot-com/cajuncoiler/Images/nst.jpg
>     http://msbdatasystems-dot-com/cajuncoiler/Images/filter0001.jpg
>   * .00536 uF MMC (1 string of .15uF x 28)
>     http://msbdatasystems-dot-com/cajuncoiler/Images/mmc_big.jpg
>   * 5-gap RQ style spark gap
>     http://msbdatasystems-dot-com/cajuncoiler/Images/newrqgap001.jpg
>   * 8 primary supports for .25" tubing with .25" spacing
>   * choice of 4.5" or 3.5" PVC for secondary
>   * dryer-duct toroid 20"x4"
>
>Query...
>
>* primary coil should have at least ____ turns with
>    a ____ inside diameter.
>
>* secondary coil should use the ____" pvc, and have
>    ____ turns of AWG____ magnet wire.
>
>---
>Christopher 'CajunCoiler' Mayeux
>http://www.cajuncoiler.tk


Christopher,

I read Bart's reply on your questions.  I also ran some calculations on 
your coil but for some reason, came up with different numbers than Bart did.

(Bart, the primary difference seems to be in the resonant frequency of the 
secondary.  I used 49.75 turns / inch and at a 97% winding factor - i.e. we 
don't usually achieve a turns per inch as tight as in the wire tables.  I 
get 1,086 turns total.  Using a 4.5" secondary with 22.5" winding length, 
and a 4 x 20" toroid, I get a loaded frequency of 184 khz.  Much lower than 
your calculations.  I am sure my program is not nearly as accurate as 
Javatc, but it usually works good for me.)

With a 6.5" I.D. on the primary, I calculate 19.2 turns needed on the 
primary.  Even if it is only 16.4 as Bart calculates, that is getting to be 
a good sized primary.  For this reason, and that .005 ufd is just about 
resonant with your transformer, I would suggest going to a larger 
capacitor, like .01ufd.  The primary would then tune when tapped at 14.6 
turns - according to my calculations.  I do agree with Bart on the 
selection and design of the secondary.

Ed Sonderman