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# [femm] lamination fill factor

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- Subject: [femm] lamination fill factor
- From: Tecnico <tecnico@sincro.it>
- Date: Fri, 10 Mar 2000 11:30:56 +0100
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    Hallo Dave,

    there is something that does not work as I expected in planar problems.
    Suppose that I have a square lamination with a central round hole. Through the hole there is a current.
    Lamination are angularly shifted of 45 degrees on the Z axis so as to obtain a star.
    Now, I set lamination fill factor to 1 for the octagon and 0.5 for the triangles, but it does not work:
    flux lines appear to be correct, but I expect that in triangular areas there is almost the same B as in the octagon since I have less iron.
    To bypass the problem I have two ways:
    1- create a new material with a different B-H characteristic (one half of the original) so as to preserve the geometry and saturation, but with the wrong B
    2- modify the geometry to preserve B and saturation

    Is this a bug or does fill factor work in a different way?

    Find attached the sample file.

    I also have another problem:
    As I told you, I have written my own class library to read, write, and workwith .fem and .ans files.
    My problem is that I can not get the correct result in calculation of torque from the stress tensor.
    The result that I get is wrong of 1e6 (probably due to some scale factor) plus 20-30% (it means that there is an error somewhere).
    I do the following:
    - find the edges over which the path lays
    - find the elements that share the edge and compute B as the mean of the B on the elements and H from permeability and B.
    - compute the torque on every edge of the path using the formula (26) of the manual
    - sum the results

    is there anything wrong on the above?

    Thank you.

    G.Bortolan

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