Re: Capacitor Dilemma

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Henry, all,
                I've seen dozens of posts along similar lines over 
the years agonizing about primary turns. The truth is that primary 
turns matter not (except for V/turn considerations and hence turn-
turn spacing). What really matters is the *inductance* and hence 
*reactance* at the resonant frequency. You might be surprised at how 
significant the reactance of your small primary is at 770kHz. A nice 
figure to aim for is 100 Ohms or even higher but 10 Ohms still works.

Regards,
Malcolm

On 14 Aug 2001, at 15:50, Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Hhchicken1-at-aol-dot-com>
> 
> Hi list, 
> I am designing a small tabletop coil with a 9" by 1 3/8" secondary, wound 
> with approximately 32AWG (actually 0.2mm) magnet wire. 
> I will be using two stacked toroids, each 0.75" thick by 3.4"
edge-to-edge.   
> I'm estimating about 4.5pf for both of them together.  Wintesla gives a Fres 
> of 775 kHz. 
> For power I'm using a 6kV/35ma NST.  Line frequency is 50Hz. 
> I will use a small triggered gap with brass electrodes (I've found the earth 
> pins from UK plugs to be very effective) run from an ignition coil and a 
> dimmer/cap controller that i've used in the past. 
> Here's the problem:  If I use an LTR, or even resonant sized capacitor,  I 
> will have to use so few primary turns that it will be sure to kill my spark 
> gap!  For a decent number of primary turns, the capacitor would have to
be so 
> small that surely the coil would be very inefficient?  I do have about 150 
> MMCs, each 0.068uF 1.6kV so I can make up pretty much any capacitor size :) 
> 
> Thanks for any help, 
> Henry Hallam
> 
> 
>