Re: 5 Turn Primary?

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

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Mddeming-at-aol-dot-com>

In a message dated 3/21/01 10:30:33 AM Eastern Standard Time, 
tesla-at-pupman-dot-com writes: 



>
> Original poster: "Nathan Morris by way of Terry Fritz <twftesla-at-uswest-dot-net> 
> " <themfam-at-home-dot-com> 
>
> Question, 
>
> If the cap value can be changed so that the number of primary turns is 
> reduced, 
> then my question is, how do you know when to stop?  With the right cap value 
> the primary could be limited to just a few turns.  There has to be some 
> loss of 
> efficiency as some point.  What is a good rule of thumb for knowing where to 
> plan ones primary tap?  I currently have over twenty turns and I am 
> planning on 
> cutting that back to about 16 turns.  I have 40 good HV (10-30 KV ) caps on 
> the 
> way so I am  flexible with my cap configuration.  I would like to reduce the 
> physical size of my primary as much as possible without jeopardizing 
> performance.   
>
> --Nate 



Hi Nate! 
        Yes, there is a limit. As the primary inductance (turns) is 
decreased, the voltage drop across the rest of the stuff in your primary 
circuit (spark gap, wiring, etc) increases in proportion. This means more of 
the power is dissipated there as heat and light (I*I*R) and less is available 
for transfer to the secondary. Also, if you reach the point where R> 
=2sqrt(L/C) the circuit will not oscillate. In both cases, R is the 
frequency-sensitive AC resistance, which may be an order of magnitude higher 
than the DC resistance. Just where the optimal trade-off point is, has had 
much written about it here and elsewhere. 
Hope this helps, 
Matt D.