Re: Directions for tesla coil research

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

Original poster: "rob by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rob-at-pythonemproject-dot-com>

Tesla list wrote:
> 
> Original poster: "Shaun Epp by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<scepp-at-mts-dot-net>
> 
> Question about increasing Q, See below,
> 
> ----- Original Message -----
> From: "Tesla list" <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Sunday, May 05, 2002 6:44 PM
> Subject: Re: Directions for tesla coil research
> 
> > Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <evp-at-pacbell-dot-net>
> >
> > Tesla list wrote:
> > >
> > > Original poster: "Malcolm Watts by way of Terry Fritz
> > <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>
> > >
> > > HI Paul, Jim,
> > >
> > > On 3 May 2002, at 10:41, Tesla list wrote:
> > >
> > > > Original poster: "Paul Nicholson by way of Terry Fritz
> > > <twftesla-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>
> > > >
> > > > Jim's comments cut to the heart of the matter:  The question is,
> > > > what is the relative significance of topload voltage and topload
> > > > charge in determining streamer performance?
> > >
> > > Absolutely agree. It's been a hobby horse of mine for quite a while
> > > now. For one of my coils, increasing Ctop by an effective 100% (Ctot
> > > increased from about 26pF to 33pF or so) resulted in a 25% increase
> > > in reach with the same primary energy and breakrate. However,
> > > unloaded primary Q was also increased by 50% as a result of retuning
> > > so the Ctop factor did not sit alone. Given half a chance (like a
> > > suitable test room), I'd like to boost Ctop further and check for
> > > further improvement. Maybe in the semester break in June.
> > >
> > > Regards,
> > > malcolm
> >
> > I've long suspected that the beneficial effect of big topload
> > capacitance is to reduce the L/C ratio of the secondary, thereby
> > lowering the resonant frequency and increasing the Q for the same
> > streamer loading.  Result is there should be more energy stored before
> > breakout, and coupling should be easier to adjust.
> >
> > Ed
> >
> 
> How does a bigger top load increase Q.    if Q = Xl / R      and     Xl  =
> 2 * pi * f * l.
> 
> from these equations, one would assume that if frequency goes down, due to a
> shift in resonant frequency, then Q decrease because Xl decrease.  I know
> I'm missing something important here, right?
> 
> Shaun Epp

Perhaps is a conservation of energy thing.  A bigger top cap can store
more energy without it leaking away in small streamers.  Then when the
energy builds up high enough, you get the big bang :)  It is definitely
true with my tiny 2Mhz test coil.  With no top cap on the pvc pipe, I
don't get much streaming out of it.  Plus it raises the freq up beyond
where my MosFET circuit can efficiently drive the coil. Rob.

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