Re: More Coupling...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Paul,

I transposed something. I need to clarify -

I realized (2nd reading) that acmi predicted the ~0.205 K when the primary
was 4cm "above"
the base of the secondary (just as you stated). For some reason, I was
thinking 4cm below and
thought that my 1.5" agreed with acmi. So obvisously it did not as the
primary was 1.5"
"below" the base of the secondary. Also, a second look at your graph and
the coupling
direction was clear. Coupling decreases when the coils are at a further
proximity from one
another (just like it does in the real world). So, no need for you to
clarify anything - it's
going the direction it should. I'm just one of those people in the world
that needs to take a
second look more often than I normally do.

Take care, (hope the info was helpful to you).

Bart

Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<paul-at-abelian.demon.co.uk>
>
> Barton B. Anderson <tesla123-at-pacbell-dot-net> wrote:
>
> > Measured K on my flat primary for my 12.75" x 45" coil.
> > The flat primary is 16.5"ID, 0.375"wire, 0.625" spacing (c-c)
> > (or 0.375 edge to edge), and 11.6 turns in the case of using
> > my 0.06uF cap setup.
>
> > K = M / sqrt(Lp * Ls) = 627 / (107.13uH * 87.6mH) = 0.205 K
>
> Assuming this is your 1000 turn, 18awg secondary, acmi predicts
> you'll get that k-factor when the primary sits 4 cm above the
> base of the secondary winding. If the primary is level with the
> secondary base, the k is calculated to be 0.178.
>
> I've made up a graph of k against primary height relative to the
> secondary base
>
>  http://www.abelian.demon.co.uk/tmp/bart-k.gif
>
> A small change in primary height seems to give quite a large change in
> k as the primary starts to fall below the secondary.
>
> p-s
> (cm)    k
> -3     0.156
> -2     0.163
> -1     0.171
>  0     0.178
>  1     0.186
>  2     0.194
>  3     0.201
>  4     0.208
>  5     0.215
>
> Bart, I'd like to know the height of your primary wrt the secondary
> base (p-s) at which your measurement was made.
>
> Ed Phillips <evp-at-pacbell-dot-net> wrote:
>
> > Grover (and BS C74) have occupied honored places on my book shelf
> > for many years!  I'll look up Grover's tables at work tomorrow.
> > I never really studied that part; just copied his formulae and
> > tables for solenoids.
>
> I only recently came across Grover's work, thanks to Mark Rzeszotarski
> who drew my attention to it when I was struggling to map out the
> mutual inductance of the secondary. They've been really useful and
> (net of software errors!) quite accurate too.
>
> Regards,
> --
> Paul Nicholson,
> Manchester, UK.
> --