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# Re: [femm] AC and DC currents in FEMM? Is this possible?

- To: femm@yahoogroups.com
- Subject: Re: [femm] AC and DC currents in FEMM? Is this possible?
- From: David Meeker <dmeeker@ieee.org>
- Date: Mon, 28 Apr 2003 17:31:15 -0400
- In-reply-to: <b8drsh+b1e0@eGroups.com>
- References: <b8drsh+b1e0@eGroups.com>
- User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.3; MultiZilla v1.4.0.3H) Gecko/20030312

`daniel_handloser wrote:`

> `Hello`

>     Can I simulate both, AC and DC currents in one model? I've only found
>     that I can describe the current with a phaser which turns with the
>     frequency specified in "problem".

>     We are three students and try to build a magnetic levitation vehicle
>     like the transrapid (.de) with a linear motor. For the levitation we
>     need DC-current in the rotor and for the propulsion we need a 3-phase-
>     ac-current in the long-stator.

> `thanks very much for answers, Dani`

`FEMM currently addresses only DC problems and AC problems in which the amplitude and phase of the fundamental only is considered.`
`In many maglev systems, the suspension and propulsion are meant to be separate magnetic circuits, so there may be no need to analyze both in the same finite element simulation (although dynamics of the two systems may interact in funny ways, because they are both pushing on the same body). Rather than trying to model everything all at the same time via finite elements, it is better to start with an analytical or circuit model that captures the operation of the suspension and propulsion and the interatction between them. The finite element analysis is then used both as a design verification/optimization tool and/or to determine parameters and so forth in the analytical model that are hard to estimate via circuit theory. This analytical model can then be used for the purposes of controller design and dynamic simulation.`
`Dave.`
`P.S. -- beware of transverse edge effects that aren't captured by 2D models when you are thinking about the design of your motor. These can have a significant effect on performance, especially for linear induction motors (i.e. secondary resistance is a lot higher than you'd expect from a 2D model, and there's extra associated leakage inductance).`

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

``

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- References:
  - AC and DC currents in FEMM? Is this possible?
    - From: "daniel_handloser" <daniel_handloser@yahoo.de>

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