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# Re: [femm] motion-induced torque

- To: femm@egroups.com
- Subject: Re: [femm] motion-induced torque
- From: "rrezarte krasniqi" <rrezarta_k@hotmail.com>
- Date: Mon, 29 May 2000 11:28:46 GMT

`
honured mr.david meekes i'm very thankful for the wonderfull information you interduced to me but i really don't underestand all the things you said and i'm very sorry that i can't be perfect to replay the questions and the meaning of this field as well asw you do i hopeyou understand me because first of all i'm very young(17 year old) but i would like to know about all this field becausei like it because it's worthy to knowledge something that it's interested.thankyou very much forbeing so goodand honest with me i wish the best to you and to your group too.
best regards from rrezarta.`

>     From: dcm3c@aol.com
>     Reply-To: femm@egroups.com
>     To: femm@egroups.com
>     Subject: Re: [femm] motion-induced torque
>     Date: Wed, 24 May 2000 19:59:02 EDT

>     In a message dated 5/24/00 4:18:29 PM Eastern Daylight Time,
>     phenning@americancooling.com writes:

>     > 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.

> `Well, the techniques that one would use to include this sort of transient
> analysis with motion aren't that mysterious. It would just take quite a bit
> of time do (i.e., nobody has gotten around to it yet in a freely available
> program, that I know of). The trick is that you have to end up doing a
> spice-like simulation of the motor and the electronics that drive it (or at
> least, some simplified representation of the electronics). The sort of
> analysis that femm does would be just one step in that analysis--determining
> the magnetic couplings at each time step. Anyhow, the above comments are
> considering a problem that is basically magnetostatic, but with a geometry
> that changes due to motion. That is, the currents in the finite element
> model that can change over time have dynamics that are part of externally
> modeled circuits--the magnetic analysis at each time step is basically a
> magnetostatic analysis.`

>     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.

> `Anyhow, femm often can be used as an aid to transient simulations. I often
> use it to obtain estimates of parameters for analytical transient machine
> models. The analytical model then can be used to answer questions about
> transient performance. However, this is not always simple to do--it requires
> a pretty good understanding to the analytical models and the relationships
> between the model's parameters and the results of finite element solutions
> (i.e. hard for beginners).`

>     Dave.
>     --
>     http://members.aol.com/dcm3c

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