[FEMM] Merry Christmas to David !!!

["Bruce G. Kang" <xiandaiwuxue@xxxxxxxxx>]

David:

Thank you! 

Merry Christmas and a Happy New Year!!!

Bruce

--- David Meeker <dmeeker@xxxxxxxxxxxxxxxxx> wrote:
> Bruce G. Kang wrote:
> 
> >Dear David:
> >
> >I need your help again. Please see attachment in
> >figures about the question:
> >
> >1. for ferrite, we want to know the leakage field
> at
> >one side region about 3~5 times the ferrite
> dimension.
> >basically it is a 3D problem. You suggested to use
> BEM
> >methods to solve it. But I found BEM is difficult
> to
> >pick up.
> >  
> >
> Your request was for a recommendation for a
> commercial program that 
> would be good for examining the distant leakage
> field.  Although this is 
> certainly possible to calculate this sort of thing
> with finite elements, 
> boundary element techniques are well-suited to this
> particular problem 
> since no outer boundary of the solution region need
> be defined.  One 
> example of such a commercial code would be IES
> Amperes, which is a good 
> and fairly intuitive program.  As far as freeware,
> there is Radia 
>
(http://www.esrf.fr/machine/groups/insertion_devices/Codes/Radia/Radia.html),
> 
> which is actually a volume integral code (rather
> than a boundary 
> integral code) but has the the same nice properties
> with respect to 
> evaluating the field at distant locations. However,
> you have to have 
> Mathematica installed to be able to run Radia.
> 
> >2. Is this a good idea? To change the vector
> problem
> >into a potential problem as in "Answer.bmp"? Due to
> >mu_r is much larger than 1, we can claim each side
> >have different potentials. The rest will be a
> >finite-difference problem to get all the potential
> >distribution of the region. B will be the gradient
> of
> >potential.
> >
> >Please comment and suggest.
> >
> >Best Wishes,
> >
> >Bruce
> >  
> >
> My original suggestion still stands--at a big enough
> distance, 
> everything looks like a dipole (or perhaps a
> collection of a small 
> number of dipoles).  You could use a 2D finite
> element solution to back 
> out a dipole moment for your device as seen from a
> distance, and then 
> shove that dipole moment into the equation for the
> field of a dipole in 
> 3D space. 
> 
> If one wanted to get more complicated, one could
> build up a 3D solution 
> for the leakage field from the contributions of the
> magnetization in 
> each element of the 2D mesh containing iron (where
> you'd use the 2D 
> solution to determine the magnetization), plus
> contributions from the 
> coils.  In this approach, the contribution from each
> element would be 
> represented as a point dipole located at the center
> of the element, and 
> the resulting field contribution would be that of a
> point dipole in 3D 
> space.  The Biot-Savart law would be used to account
> for the 
> contributions of the coil.
> 
> Dave.
> 
> -- 
> David Meeker
> Senior Engineer
> Foster-Miller, Inc.
> 350 Second Avenue
> Waltham, MA 02451-1196
> 781-684-4070
> 781-890-3489 (fax)
> dmeeker@xxxxxxxxxxxxxxxxx 
> http://femm.foster-miller.com
> 
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