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.