[TCML] Modeling a compact ribbon primary

[Paul Nicholson <tcml87@xxxxxxxxxxx>]

Hi All,

Chris Swinson recently wrote:

> my primary will be 4 turns of 2" wide strap separated about
> 1mm apart.. the dia is about 22"

and asked whether turn-to-turn C needs to be accounted for.

My stock reply was 'no', because the overall effect of inter-
turn C has always been negligible in the coils we're used to
looking at.

But this is rather an extreme case and closer inspection reveals
that it does have a dramatic effect, at least on the bare coil
itself, although once the coil is connected to a primary cap
of say 3nF, the effect of inter-turn C is much less.

The inter-turn C, it turns out, alters the coil's effective
inductance, rather dramatically for the bare coil, and is
very significant.

I began a note to explain all this, but it got a bit long,
so I turned it into a web page.  In the end it turned into
something of an essay which delves into the concepts of self
capacitance and self inductance and explains how they're defined
and modelled.  I try to show how the coil's effective inductance
is altered by the internal capacitance of the coil and use a
spice model for illustration.  This effect is something which
occurs in all our coils but is particularly clearly demonstrated
in this extreme primary.

 http://abelian.org/tcml-notes/080728.html

Hopefully it will be an interesting read and will shed some
light on the distributed self reactances of coils in general.
--
Paul Nicholson
--

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