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# Re: Permanent magnet operating point

- To: femm@yahoogroups.com
- Subject: Re: Permanent magnet operating point
- From: "David Meeker" <dmeeker@ieee.org>
- Date: Mon, 12 May 2003 13:59:07 -0000
- In-reply-to: <b9goqu+uutb@eGroups.com>
- User-agent: eGroups-EW/0.82

    --- In femm@yahoogroups.com, "tano1938" <rgarritano@c...> wrote:
    > What,s the best way to get the permanent magnet operating point for a
    > magnetic circuit using femm. I've been using the integral of B over
    > the block (magnet), dividing this by the volume to get the average B
    > and then using this average B with the the magnet data curve and
    > coercivity to get H. Is there a better or an easier way.
    >
    > Thanks for your help

    The way that FEMM works, an operating point is really being determined
    for each individual element. If I understand correctly, what you want
    to do is get sort of a reduced-complexity circuit representation of
    your problem in which the magnet is represented as one single element
    in a magnetic circuit.

    The problem here is that in some geometries, different parts of the
    magnet might be operating at very different operating points. The
    "right" way to do the approximation probably depends on which
    particular device you are trying to model. If the field inside the
    magnet is fairly homogeneous, averaging the B in the magnet is
    probably an OK way to go. One sort of interesting reference that uses
    this approach, at least as a metric in comparing different ways of
    looking at the operating point of permanent magnets, is:
    http://www.consult-g2.com/papers/paper16/paper.html
    Another interesting document is:
    http://www.duramag.com/engmach/MMPA%20PMG-88.pdf
    On page 8, in the "Demagnetization factor and load lines and circuit
    concepts," different demagnetization factors are presented depending
    upon whether you are trying to determine the flux passing through the
    center cross-section of the magnet or the average flux in the magnet.

    Dave.
    --
    David Meeker
    http://femm.berlios.de/dmeeker

- References:
  - Permanent magnet operating point
    - From: "tano1938" <rgarritano@comcast.net>

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