Re: More Coupling...

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

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-uswest-dot-net>" <evp-at-pacbell-dot-net>

> acmi computes self and mutual inductances for concentric air cored
> coupled coils by representing the windings as a large number of
> circular current filaments and summing their contributions. This
> approach allows arbitrary winding cross section profiles to be modeled
> and also gives the mutual coupling in distributed form if required.
> 
> The approximation taking place here is likely to be weakest when large
> conductors are used. Consequently we expect the worst results to occur
> with primary self inductance and the best to be achieved with
> secondary self inductance. Error on mutual inductance is expected to
> lie between these extremes and the coupling coefficient k is at the
> mercy of all three sources of error.
> 
> On the whole the program seems to over-estimate primary and mutual
> inductances, and the error in mutual inductance is worse at closer
> coupling, as expected in view of the primary conductor subtending a
> larger angle as seen from a secondary conductor.
> 
> Attempts will be made to reduce the program error by seeking a better
> representation of the thick primary conductor.
> 
> If this program finds a use in the tesla community it will be largely
> due to the efforts of Bart Anderson, Terry Fritz, and others, whose
> continuing work to gather measurements and improve techniques involves
> far more man-hours than is required to code and maintain the program.
> 
> --
> Paul Nicholson,
> Manchester, UK.
> -

	Note to all concerned.  Some of us get our kicks out of precise
calculations and measurements and are enjoying this continuing
discussion.  However, acmi in any form is completely adequate for use of
anyone designing or analyzing a real TC, where errors of several percent
are insignificant.  I haven't used any of the other mutual inductance
programs which have been mentioned here, but they are probably equally
suitable.

	One note on estimating secondary turns if you are too lazy to sit and
count them one by one, without making a single error.  If you have a
good ohmmeter you can measure the secondary resistance, and then measure
the resistance of a known length of the same wire and calculate the
length required to give the same resistance, and from that compute the
number of turns.  Of course, for this to be really accurate you need to
know the effective diameter of the turns to at least the same precision
as your desired answer.  The counting method is better, of course, but
tedius.

Ed