Re: ACMI bug fix

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

Original poster: "Peter Lawrence by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Peter.Lawrence-at-Sun-dot-com>

Paul,
     do you think ACMI is now debugged enough that someone could use it to
compute a the L of a number of TC primaries with different "conical angles"
and come up with an empirical formula for conical inductance as a function
of straight helical inductance, flat spiral inductance, and conical angle.

IE, it has been reported that the previously suggested formula
	SQRT( (sinA*L-helical)**2 * (cosA*L-spiral)**2 ) 
is incorrect, but there might be a workable formula to be found by a creative
mathematician.

Pete Lawrence.



>Original poster: "Paul Nicholson by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
<paul-at-abelian.demon.co.uk>
>
>Bart,
>
>> Out of curiousity, what was the bug?
>
>A mistake in the use of the radius when calculating M. This bug
>would not show up with a constant-radius coil, ie a solenoid. 
>I noticed it when running Dave's three trifilar strands - the 
>resulting k between strands was well short of unity - so I went
>hunting for the bug.  The mistake had crept in when I extended the
>code to do arbitrary coil profiles.  The mistake stayed in because
>I failed to test it properly with the data you and others have
>previously provided - I just used solenoid models, not the flats (:
>
>With the broken v0.6a, you might well have got different values of
>M if one of your coils was a flat spiral, and you change the order
>that they appear in the input file.  Bart - I think you noticed
>something odd?
>
>You'll find that there's an extra digit of precision in some of the
>inductance outputs.  This is usually a *bad thing* since it's a
>nonsense to report more digits than the accuracy of the calculation.
>In this case, the extra digit helps to give smooth convergence when
>you wrap a gradient descent optimisation around acmi - for seeking
>geometries which max the L.  Just something I'm playing with but will
>probably take out again. 
>--
>Paul Nicholson
>--
>
>
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