FreeLists / si-list / [SI-LIST] Re: Internal Inductance

["Craig Clewell" <cclewell@xxxxxxxxx>]

Thank you Scott, and Doug for the helpful information.

Craig


-----Original Message-----
From: Scott McMorrow [mailto:scott@xxxxxxxxxxxxx] 
Sent: Thursday, August 05, 2004 12:23 PM
To: cclewell@xxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Internal Inductance

Craig,

I don't believe there is a straightforward analytical formula for 
non-round conductors.  When you start getting into internal inductance 
for trace geometries in the presence of a plane, then it will definitely

depend on the shape and proximity to the other conductors.  However, 
this problem is easily solved by several different field solvers.

Commercially, Ansoft Maxwell 2D does a very good job of extracting 
inductance at multiple frequency points.  You just have to be sure to 
use the impedance matrix.

Academic codes such as FastHenry from MIT and Simian from Dean Neikirk 
at the University of Texas can correctly solve for frequency dependent 
inductance and resistance of arbitrary shapes.  Links to these can be 
found at http://www.fastfieldsolvers.com/links.htm

Or, if you are dealing with stripline traces, you can use a boundary 
element method or method of moments field solver to run two problems.

Problem 1) your rectangular trace at the normal thickness centered 
between the planes.

Problem 2) a very very thin trace centered between the planes.



regards,

scott


Craig Clewell wrote:

> Greetings, 
>
>Does anybody out there have an equation handy to calculate the internal
>inductance of a square, rectangle, or any other object that is not
>round?  I already know that the internal L of a round wire is
(u*length)
>/ (8*pi), but I'm not looking at using a round wire.  I've read that it
>should be about 20% of the external inductance, however I want to dial
>it in better than that.  I'm so used to neglecting this, that I know
>find myself at a "loss".....ok...that wasn't funny :>)
>
>Thanks for sharing....
>
>Craig
>
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Scott McMorrow
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