Re: Directions for tesla coil research

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Shaun,

On 5 May 2002, at 18:55, 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

I'd tend to agree with you. However, the unloaded secondary Q 
probably doesn't change a great deal anyway because as the frequency 
goes down, the current is spread more evenly throughout the wire. In 
any event, secondary Q's are so high relative to the primary that it 
isn't the most important factor anyway.

Regards,
malcolm