Re: Big Primaries, Small Caps

["Malcolm Watts" <M.J.Watts-at-massey.ac.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Greg,
         Here's the basic idea:

On 3 Sep 00, at 12:08, Tesla list wrote:

> Original poster: "Gregory R. Hunter" <ghunter-at-accucomm-dot-net> 
> 
> Dear List,
> 
> I'm curious about Tesla coils with large primaries and small tank caps.
> John Freau and others have articulated numerous times over the years that
> coils so designed have lower gap losses and longer sparks relative to coils
> using big tank caps and few primary turns.  I'm curious as to why this is
> so.  It seems to me that the bigger bang size delivered by a larger cap
> would thump the secondary harder, yielding longer sparks.

Keep the "thump" large and at the same time, increase Lp. That 
reduces the thump current which reduces gap loss since gap 
loss is proportional to gap current. Since Lp has increased 
and Cp has remained the same, Fprim has dropped and to match 
this, Fsec must drop to maintain tune. If you are currently 
operating with a terminal which has a suitably sized minor 
radius such that it *just* breaks out at the peak of secondary 
ringup, you could usefully increase its major radius and/or 
increase Ls. Note that simply increasing Cs to drop Fsec 
causes Vsec to stay the same or go down since Ep doesn't 
change although there is a gain as the primary losses are 
decreased. 
      A comparison that would be *very* interesting to see: an 
improved primary with two secondaries, one of which has an 
increased Ctop with the same minor radius and the other which 
maintains the same Ctop and compensates with an increase in 
Lsec.

Regards,
malcolm

 
> Can someone in the know provide an explanation?  I'm not an engineer, but I
> am an experienced comm/nav technician, so I can grasp pretty deep concepts.
>  However, a side trip into Calculus land will lose me pretty quickly.
> 
> Best Regards,
> 
> Gregory R. Hunter
> 
> 
>