Re: Rotary Spark Gap Design

To: tesla-at-pupman-dot-com
Subject: Re: Rotary Spark Gap Design
From: Skip Greiner <sgreiner-at-wwnet-dot-com>
Date: Wed, 15 May 1996 00:31:12 -0700
Tesla List wrote:
> 
> >From LEYH-at-slac.stanford.eduWed May 15 21:30:59 1996
> Date: Wed, 15 May 1996 14:00 -0800 (PST)
> From: LEYH-at-slac.stanford.edu
> To: tesla-at-pupman-dot-com
> Subject: Re: Rotary Spark Gap Design
> 
> In-Reply-To: tesla-at-pupman-dot-com -- 05/15/96 12:20
> 
> Hi all,
> 
> Regarding the xmsn line vs. lumped element methods of modeling the secondary,
> it seems that the most accurate model is a mixture of the two, but much closer
> to the lumped element side.  There are several reasons why a close-wound,
> single layer coil cannot be treated as an xmsn line:
> 1. Turn-to-turn coupling - If a xmsn line  is divided into segments, each
> segment has almost no 'lumped' coupling with the next.  Adjacent turns Big snip
> any wave that tries to propagate along the secondary wire.
> 2. Impedance - The highest line impedance possible without ferrite cores is
Big snip
> 3. Resonance - Secondary coils are highly resonant, as everyone here has
big snip
> the winding. (Looked a lot like a quarter-sinewave at first).
> I don't have high confidence in my model at this point, and will gladly trade
> info with other 'rainy-day modelers'.
> 
> -GL

GL and all

I like what you say as far as it goes. After spending about 2 years I 
have finally wound a secondary which free resonates at four times the 
quarter wave frequency of the wire it it wound with without any terminal 
capacitance. The interesting part of this winding is that any terminal 
capacitance seems to reduce the discharge length from the 5" standoff 
insulator I use on top. The discharges with no term cap approach 4 
feet. There is a lot of corona around the top of the winding.  At very 
low excitation (milivolts) you can actually sense the voltage buildup 
along the length of the secondary from the grounded end to the top where 
a maximum is achieved. I have not quantitatively measured the voltage 
change so I cannot say if it is square law. This thing looks very much 
closer to a transmission line than a lumped constant circuit. 
Would there be any application of lumped constant delay line theory to 
our problem? 

Skip