Re: Rotary Spark Gap Design

To: tesla-at-pupman-dot-com
Subject: Re: Rotary Spark Gap Design
From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
Date: Fri, 17 May 1996 17:00:01 +1200
Hi all,
         Jim I'm glad you wrote this...

> > "During the spark dwell time, the 
> >magnetic flux produced by the primary links the entire secondary.
> >Consequently the primary/secondary interplay of energy may be treated
> >by lumped circuit analysis". 
> 
> I have to disagree their statement for 3 reasons.
> 
>  Based on both yours and Richards prior post on Toroid coupling into
> the primary field, in which  you both stated that the coupling was
> nil. If the Toroid was NOT coupled into the primary field, then the
> top of the coil was not either (to any great extent)
> 
> Dr. Rzeszotarski's prior post on coupling indicated a decreasing
> coupling based on height above the primary. ( sorry, I seemed to have
> not saved that post:( so I can't quote exact numbers.
> 
> Finally, I you visualize a single turn secondary with a volt meter
> attached, and slowly raise it up from the bottom of your TC secondary
> to the top of your TC secondary, you will get a decreasing induced
> voltage: almost NIL at the toroid position.

I quite agree. I have found a number of contradictory and 
inconsistent statements in the material in question, and I think
the example they gave is less than convincing. This of course has
been a major source of headaches for me. It absolutely stands to 
reason that the coupling decreases as one looks up the coil, and
my earlier analysis showing the effects of reflected conjugate 
impedances on prim-sec matching support this. That kind of behaviour 
is definitely 1/4 wave line behaviour.
   BTW, I said earlier that the voltage gradient was sinusoidal. I
think that is true if there is no terminal present. Having a lump 
of capacitance tends to linearize the gradient as the circuit tends
to lumped L-C. BUT, that doesn't alter the way the primary couples
in.

Malcolm

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