Re: [femm] Why femm sometimes never finised the calculation ?

[David Meeker <dmeeker@xxxxxxxxxxxxxxxxx>]

matthewc_98 wrote:

> Hi All,
>
> I have used femm ver. 3.1 for one month. I would like to
> thank Dave, because this is a great sofware. There is one question
> needed to have your advice. I used femm to simulate the solenoids.
> In some types of solenoids, it works very well, but in other types
> of solenoids, it never ending the calculation.Even I used different
> mesh densities; it still didn't work. Can you help me to answer this
> question? Thank you so much.
>
> Best Regards,
>
> Matthew

Hmm--it's hard to say what's going on without seeing an example.

Sometimes bad things can happen if you have very small angles between lines
in your mesh (or a line tangent to a circle, for example)--triangle, the
meshing program, can break down in that case, or make a mesh that causes
things to hang. If this is the case, try redrawing the problem region in a
way that avoids the sharp angles.

It is also might be possible to make a nonlinear material that has
convergence problems--this might happen in some materials with a really
pronounced "initial permeability" region. The solver can then end up
bouncing around that section of the curve, never finishing the Newton
Iteration part of the solution. You can try substituting linear materials to
see if this is the problem. If so, you might have to "smooth out" the
initial permeability region to get things to converge.

Dave.

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