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FEA 2D to 3D extrapolation

FEA 2D to 3D extrapolation

FEA 2D to 3D extrapolation

I've ran some 2D FEA simulations on some cylindrical permanent magnets and measured their magnitudes for increasing radii. After a certain distance away from the magnet the magnitudes are constant at a given radius regardless of rotation, and governed by the equation y=a/r^-b. 'b' is an integer equal or greater than 2, depending on the pole count (b=#poles/2+1).

However, by the time these equations become valid the magnet in question could be better approximated as a point source rather than an infinitely long cylinder as simulated. Perhaps an analogous situation is the point charge/line charge/sheet charge series of equations, where electric field strength is a function of r^2, r^1, and r^0 (i.e. constant) respectively. That analogy leads me to believe that I can better approximate reality by increasing the exponent 'b' by 1 (and adjusting 'a' as necessary).

So if the original equation is y=100/r^2, the new equation might be y'=200/r^3.

Does this seem like a valid approach?

RE: FEA 2D to 3D extrapolation

Yes. But it ignores the 3 dimensional lobe pattern of the field, and so it is a rough guide at best in th near field. In the far field then if it is a point source the answer is the pen and paper solution.


Greg Locock

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