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# Re: Circuits on femm

- To: jrcamacho@ufu.br
- Subject: Re: Circuits on femm
- From: dcm3c@aol.com
- Date: Tue, 28 Aug 2001 23:48:26 EDT
- Cc: femm@yahoogroups.com

In a message dated Mon, 27 Aug 2001 08:37:03 -0300, jrcamacho@ufu.br writes:

> Dear Dave,
> I would like to ask you a few questions on behalf of some students
> here. They saw the mention of circuits in the pre-processing stage
> of femm. They are trying to incorporate results from dynamic
> simulation on femm. Is this possible at this moment? If yes, is out
> there any manual, or anything written in the subject? In the femm
> pdf manual they didn't find a word on how to use this feature. so,
> they asked me to make this enquire.

I've been doing some work on updating the manual, and some of the updating
includes an explanation of the "circuit" properties. The updated manual in
the "rough draft" 3.1 version at http://groups.yahoo.com/group/femm/files/
Anyhow, the "circuit" properties are really just constraints on
current--calling them circuits might be a misnomer. For example, you might
make a "circuit property" where the total current is defined to be zero and
then apply that to the plate conductor in a linear induction motor to enforce
conservation of current on the conductor. You can also apply a "circuit
property" with a nonzero current to a conductor or to a bunch of conductors
driven in parallel, instead of applying a bulk current density to the
conductor. The program then automatically adjusts the applied voltage so
that the desired total current is obtained. In the post-processor, it is
then possible to look at the circuit results and see the impedance that is
associated with the circuit.
I have not yet done any transient simulations with femm, but I think that
with the addition of the Lua scripting language to the program that transient
simulations are probably now possible. To actually do this, the simulation
itself would be written as a Lua script that runs in the preprocessor,
calling the solver and post-processor to get flux linkages corresponding to
various currents and positions. I still have to do a little head-scratching
with respect to this one, though. Perhaps one of your students (or at least
someone who has more time right now than me) would be curious to try and
figure out how to put together a simple example of a transient simulation
using the Lua scripting.
T

> he femm program is helping us a lot here and I would like to thank
> you to make it available for educators.

I'm glad that the program is useful to you. Yours is just the sort of
application that I had in mind when I decided to release the program for free.
Dave.

> Note: Feel free to post this enquire in the femm discussion list.
> With our regards and thanks in advance for your attention.
> Sincerely,
> Dr. J.R. Camacho - IEEE Member:01981539 - ATP-EMTP-CLAUE-08
> Rural Electricity and Alternative Energy Sources Lab.
> UFU - School of Electrical Engineering - P.O.Box: 593
> Phone:+55.34.3239.4165/Ext.:250 - Fax:+55.34.3239.4166
> 38400.902 - Uberlandia - MG - Brazil

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