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Re: Why does top capacitance work?




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<< 
 Hi John,
          You wrote in reply....
 
> > Different K's have to be used for the comparisons because the
> > magnifier will not work properly using the low K's of the classical
> > coil. The gap losses will be different and that will determine
> > which is the better system. The overall efficiency and not the
>> operational mode would be the main interest.
 
> I think it is obvious which is going to win under those conditions 
> isn't it?
 
> > I would like to see someone try all of the test combinations you
>> mentioned for critically coupled coils. If no one has ever built a
> > critically coupled Tesla coil it's about time this possibility be
>> researched in all its variations.
 
> I have scoped operation of running coils and under >90% of all 
> streamer conditions they were over-coupled. The beat envelope was 
> clearly present. A critically coupled circuit by definition loses as 
> much power in the primary resistance (gap) as it does in the 
> secondary (discharge). That can't be an ideal to aim for can it?
> In fact, the only time I was able to reduce the beat envelope to a 
> single transfer was with a discharge rod positioned at a rather 
> critical distance away from the secondary.
>     I once tried bringing a 2-coil system to critical coupling under 
> non-spark conditions in the secondary. I had to lift the secondary 3 
> feet+ clear of the primary to achieve this. It simply could not 
> produce a discharge under those conditions because the energy 
> transfer losses were so great.
 
> > For example, has anyone set up a Tesla coil with a single hump physical
> > coupling arrangement and determine if this gives Rp = Rs?  How did the
> > controlled spark length compare with the different combinations?
 
> Terman and others state that critical coupling is achieved when the 
> reflected resistance the primary sees is equal to its own resistance.
> Rs is never equal to Rp in a TC because of the transformation ratio. 
>In my experience it requires a 1:1 ratio for Rs = Rp under the 
> conditions you describe (e.g. an I.F. transformer in a radio set).
> Worth noting too that Rp is non-linear in a good coil (gap losses 
> dominate all others).
 
> > I believe there are many classical coil combinations (and magnifiers)
that
> > we have not explored that may offer advantages over what we are now
using.
> > 
> > John C.
 
> I'd agree wholeheartedly with that. I am working on some right now.
 
> Malcolm
  >>

John, Malcolm, All,

Yes, in general it seems that the looser the coupling the less spark is
produced, I don't see how very loose (critical) coupling could be "better".

John Freau

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