Re: Inductance calculations

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

Original poster: "Paul Nicholson by way of Terry Fritz <teslalist-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>

Hi All,

I didn't recognise the recipe used by Moshier, but I would expect
Inca (great name!) to give better answers for very low turns than
fantc/acmi, because it uses a more direct method which doesn't
rely on circular filament approximations.

As the wire becomes more stretched out, mutual inductance between
remote part of the coil gets smaller, so that the overall self
inductance drops, and the minimum is reached with a straight line.
Can Inca follow this trend all the way, I wonder?

This whole matter of low inductance structures is quite challenging
both for calculation and measurement, and it remains to be seen just
how far these programs can go.  We can clearly see the limits of the
circular filament approximation, and I think that direct Neumann
integration of small linear elements ought to do much better here.
But there remains the thorny question of what to do about structures
made from fractional turns of wide sheets and thick tubes.

I'm still pondering k factors following Antonio's post of several
days ago.  Some of the math in pn1401 section 6 is wrong and I can't
extract the k just using determinants in the way proposed. I'm in
rewrite mode and rethink mode, but for now the only way I can
predict an operational k is to continue with just computing the two
mode frequencies and using these to calculate the k.  However I feel
that there ought to be a more direct method which doesn't involve
computing the modes first, only I haven't seen it yet.
--
Paul Nicholson
--