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# Re: [femm] motion-induced torque

- To: <femm@egroups.com>
- Subject: Re: [femm] motion-induced torque
- From: "Eckart Nipp" <eckart.nipp@m-v-l.de>
- Date: Thu, 25 May 2000 08:42:33 +0200
- Reply-to: "Eckart Nipp" <Eckart.Nipp@m-v-l.de>

    Hi,

    as far as I remember, a moving geometry is not required for this type
    of computation. It can be solved by DC and AC-steady state simulations,
    i.e. by what Femm offers. However, I don't remember the exact procedure.
    It should, however be possible to find the basics in the literature.
    This will however only work for steady state. Transient behaviour on
    the other hand is much more difficult, e.g. start-up of a mains
    connected motor, where speed and slip are not constant.

    >I was curious if there was anything miraculous about the ability to
    >compute motion-induced torques etc. using FEA, for example computing
    >the torque output of an induction motor at a steady-state slip.
    >Several commercial products do this with "rotating airgaps", etc.
    >Are these meshing and solution algorithms above and beyond the scope
    >of shareware, involving very new ideas, or has it just not been
    >gotten around to yet? As a novice I was just wondering.

    Dave wrote:
    >A related issue that actually is more difficult is the inclusion of
    >motion-induced eddy currents. Instead of just solving series of relatively
    >benign magnetostatic problems, motion-induced eddy currents mean that the
    >problem is governed by equations with strong convective terms, which can be
    >quite difficult to model accurately. I don't know of a commercial program
    >that does really well in eddy current problems with high-speed motion.

    I can imagine that that is a problem. What about Mega? Isn't that able to
    directly include motion induced currents?

    Greetings
    Eckart

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