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Re: Arc Impedance Study - Computer Models



At 09:56 AM 10/12/98 +1200, you wrote:

snip

>Sorry, I didn't intend to be confusing. I was questioning the notion 
>that uniform secondary current could exist in a coil with no topload 
>*when the gap is firing* as is claimed in some quarters. I maintain 
>it cannot simply because there is virtually no loading on the top 
>turns. In fact, the top turns become the terminating capacitance in 
>my view if no other topload exists. Yes? 
>
snip
>
>Thanks,
>Malcolm
>
>

Hi Malcolm,

	I think the top current in a coil, without a top terminal, would be much
less than at the base of the secondary.  I think the current is absorbed
into the space around the coil in the form of Medhurst or self capacitance.
 However, I also think that current stays in phase along the secondary
since the Medhurst capacitance acts on the coil as a single lumped
capacitance not a distributed capacitance such as occurs along a
transmission line.  The Medhurst capacitance cannot support phase shift as
would occur in a transmission line.  When a top terminal is introduced it
is also bathed in the fields of the Medhurst capacitance and the overall
current around the coil stays in phase.  This effectively stops resonant
rise and VSWR effects.  Note that I didn't use the term "distributed
capacitance" to describe the self capacitance of the coil.  That term may
be misleading in the case described here.

	Terry Fritz