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Re: Mutual Inductance & K Factor



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

John H. Couture wrote:
> All the present mutual inductance and K Factor programs are
> based on empirical data.

ACMI and MandK both work by directly computing the inductance 
using the Neumann integral.  This involves integrating an
elliptic integral over the coil - in MandK by direct computation
of the elliptic integral, and in acmi by table lookup.
The computation converges to an exact solution for wires which are
small compared to the turn radius.

The familiar Wheeler and Lundin equations are derived as
approximations to the elliptic integrals.

There is no reliance on empirical data.

The results of both programs should closely match low frequency
empirical data, to circa 1% for closewound solenoids, and to within
5% for open tube spirals.  Neither program contains any tunable
fiddle factors and they compute directly from the geometry. 

A potential source of error may occur at high frequency, because
the inductance calculations of both programs assume a uniform
current distribution in the windings.
--
Paul Nicholson
--