Re: [femm] Horse shoe magnet

[David Meeker <dmeeker@xxxxxxxx>]

Robert Strand wrote:

> Hi,
> eavogels wrote:
> > I need to make a femm model of a horse shoe magnet but I don't know
> > how to do it since the magnetic direction is ofcource different in
> > both ends. How should I solve this: creating a lot of small magnets
> > in the form of a horse shoe or does someone know a better way. If
> > someone has a sample he wants to share, please send it to
>
> I don't think it is possible with FEMM. FEMM only solves 2-D planar and
> axisymmetric magnetic problems. The horseshoe is a full 3-D problem, 
> and I
> can't see a way of transforming the problem even with it's lines of 
> symmetry.
>
> Regards
> Rob

Most horseshoe magnets that I've seen are not very deep in the 
into-the-page direction. I'd agree that you'd need a 3D approach to 
analyze that sort of geometry, because there would be a huge amount of 
fringing that would not be captured by a 2D model. However, it ought to 
be possible to make a model of a horseshoe that is long in the 
into-the-page direction. The results would then give a reasonable 
approximation of the fields that you'd observe towards the middle of the 
magnet. I've attached an example of this sort of magnet. As Eric had 
suggested, I built it up out of a bunch of sections that each have a 
slightly different direction. Just for overkill, I've used the "Kelvin 
Transformation" method to model the magnet sitting in an unbounded domain.

Dave.
--
David Meeker
email: dmeeker@xxxxxxxx
www: http://femm.berlios.de/dmeeker

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