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# Re: [femm] Motion Induced Eddy Current Simulation

- To: femm@yahoogroups.com
- Subject: Re: [femm] Motion Induced Eddy Current Simulation
- From: David Meeker <dmeeker@ieee.org>
- Date: Thu, 03 Apr 2003 10:15:09 -0500
- In-reply-to: <571HDaueQ7472S22.1049227482@uwdvg022.cms.usa.net>
- References: <571HDaueQ7472S22.1049227482@uwdvg022.cms.usa.net>
- User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.3; MultiZilla v1.3.1.2) Gecko/20030312

`STEVE ABOAGYE wrote:`

>     Hi,
>     I need help on modeling a motion induced eddy current problem. The
>     setup invloves a reciprocatory motion of a stage that has permanent
>     magnet pole pieces that induce eddy current in adjacent material. I have
>     seen some messages on eddy currents but cannot glean anything to help me
>     yet. Thanks for the anticipated help.

> `Steve`

    This can be difficult to do in FEMM. If the amplitude of the motion is
    small, and if the geometry is amenable to a 2D or axisymmetric analysis,
    you can sometimes model this sort of situation via an AC model that
    models only the part of the field that is changing with motion. For
    example, if you had a cylindrical magnet that was moving axially in a
    sinusoidal manner at a frequency w and an amplitude d, you might replace
    the magnet by a point current of d*Hc and the upper corner of the magnet
    and a point current of -d*Hc at the lower corner of the magnet. You'd
    then perform the analysis, prescribing w as the frequency.

    Otherwise, you probably have two options. Either beat on the problem
    with a more elaborate finite element code, or do it the "old fashioned"
    way, by making some sort of a lumped parameter/magnetic circuit model of
    your geometry, possibly using a series of finite element analyses to
    help deduce parameters for your model if the geometry is complicated.
    It's often good to try a model like this first, because it can give you
    a sense of what mechanisms/geometric parameters are driving the behavior
    of interest (because they are clearly in evidence in the equations).

    Dave.
    --
    David Meeker
    email: dmeeker@ieee.org
    www: http://femm.berlios.de/dmeeker

- References:
  - Motion Induced Eddy Current Simulation
    - From: STEVE ABOAGYE <steve.aboagye@usa.net>

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