[Prev][Next][Index][Thread]

Re: Why does top capacitance work?



-- BEGIN included message





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






-- END included message