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# [FEMM] A little paradox with anti-periodic boundary condition and torque computation

- To: femm@list.foster-miller.net
- Subject: [FEMM] A little paradox with anti-periodic boundary condition and torque computation
- From: Tsarafidy RAMINOSOA <tsarafidy@yahoo.fr>
- Date: Fri, 17 Oct 2003 14:29:12 -0400
- Reply-to: Finite Element Method Magnetics mailing list <femm@list.foster-miller.net>
- User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.3.1) Gecko/20030425

    Hello all,

    I've attached two models of synchronous reluctance motor using anti-periodic boundary conditions
    in order to reduce the area to be computed. So only a half part of the motor is drawn.
    The second model is obtained from the first by rotating the rotor of 180 degree angle.
    Since the rotor is symmetric, for the two models, the Bn and Ht-plot along the airgap arcsegment
    in front of the rotor should be equal but with opposite sign.
    For Bn, it seems to be verified, but not for Ht.
    AJ integrals are the same for the two models but the Torques obtained from weighted stress tensor are not.
    These torques was computed in taking the whole group n°2 (in the models) as area of integration.
    So I'm wondering if there is any limitation in using anti-periodic boundary condition or if it's in
    the torque computation that I should take some care.

    I got the following result :
    Model_1
    AJ integral =  1.390088e+002 Henry Amp^2 / m
    Torque =  -3.040467e-002 N*m     /m
    Model_2
    AJ integral =  1.389757e+002 Henry Amp^2  /m
    Torque =  6.750423e+001 N*m  /m

    Could anyone explain me why Ht are not the same ?
    Any help would be appreciated.
    Best regards

    Tsarafidy

Attachment: `models.zip`
Description: Zip compressed data

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