[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

# [femm] Re: No Subject / Materials....

- To: femm@egroups.com
- Subject: [femm] Re: No Subject / Materials....
- From: Dcm3c@aol.com
- Date: Tue, 14 Mar 2000 23:08:19 EST
- Delivered-to: listsaver-of-femm@egroups.com
- Delivered-to: listsaver-egroups-femm@egroups.com
- List-archive: <http://www.egroups.com/group/femm/>
- List-help: <http://www.egroups.com/group/femm/info.html>, <mailto:femm-help@egroups.com>
- List-unsubscribe: <mailto:femm-unsubscribe@egroups.com>
- Mailing-list: contact femm-owner@egroups.com
- Reply-to: femm@egroups.com

    In a message dated 3/14/00 1:09:48 PM Eastern Standard Time,
    jvilla@posta.unizar.es writes:

    > Hi,everybody
    > First let me introduce my self. I'm Juan Luis Villa From University of
    > Zaragoza (Spain);I'm developing my PHd THesis on the modelization of Lineal
    > Induction Motors and your program is very usefull for me. But I have a
    > problem with the modelization of induction current. I'm trying to
    > modelizate induction current on an aluminium's sheet.
    >
    > Does anybody Know how to do it?; is it posible to modelizate with femm?

    femm could be somewhat useful in analyzing LIMs. One way to go about it is
    to model your machine and then run analyses at various frequencies. Since
    the model is static in the sense that the plate isn't moving, the frequency
    that you are specifying is the slip frequency of the machine. You can get
    some possibly useful results about the relationship between current, slip,
    and force at zero speed in this way.

    However, you have to be careful in interpreting 2-D LIM models. Edge effects
    and higher harmonics aren't adequately represented in a 2-D model without
    motion, and these phenomena can have important implications on machine
    performance. I'd suggest using femm as a check on the magnetostatic fields
    predicted by analytical models (current sheet models, for example) and as a
    method of obtaining parameters for use in analytical models that include
    these extra 3-D effects.

    If you just want to look at the effects of some current distribution in the
    plate, you can break the plate into a number of sections and apply volume
    currents so that a sinusoidal current distribution is approximated.

    In a message dated 3/14/00 6:11:17 PM Eastern Standard Time,
    scott_norton@surromed.com writes:

    > Like others, let me first claim my ignorance about magnetics...
    > (Why do the equations have to seem so much more complicated than
    > electrostatics!?!?)

    Well, for your sort of problem, you can at least gain some intuition from
    electrostatics. It is possible to formulate a problem with just magnets as
    scalar potential problems, just like electrostatics. The ends of your
    magnets are like surfaces with a distributed charge, the surface of any iron
    object is (ideally) at a constant potential, and so on.

    > My mission: To increase the B field gradient in a very small
    > localized volume. I have a couple nice fairly large magnets and I
    > want to introduce some strips of metal material around my small volume
    > to cause large field gradients. I'd like to explore my options
    > using FEMM.

    If you can idealize your configuration as a 2-D or axisymmetric problem, femm
    ought to be able to do the trick.

    > First of all, what type of material am I looking for that enhances
    > magnetic field gradients? What's the material specification that tells
    > one this? For instance, I've seen nickel strips introduced into a uniform
    > magnetic field that was used to create gradients. Why was
    > it chosen? What's better? If I was to model nickel in FEMM, do I need
    > the BH curves or is magnetic permeability enough?

    Rather than just pure nickel, the strips that you have seen are probably a
    high nickel alloy like mumetal, permalloy, or supermalloy. Mumetal and
    supermalloy are in the femm materials library. These materials have an
    extremely high permeability, but a fairly low saturation flux density.

    Depending on what you are doing, these materials might be overkill--plain
    iron or some low carbon alloy might be adequate. The permeability of these
    materials isn't anywhere near as high as the nickel alloys, but it's still 3
    or 4 orders of magnitude more permeable than air (i.e. looks almost
    infinitely permeable with respect to air).

    At any rate, without a knowing more about the application, it's hard to say
    too much more. For example, it's possible to think up configurations of just
    permanent magnets that have really steep field gradients--what is an
    acceptable material / geometry depends upon what you are trying to do.

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

- Prev by Date: [femm] Materials....
- Next by Date: [femm] torque calculation
- Previous by thread: [femm] Materials....
- Next by thread: [femm] torque calculation
- Index(es):
  - Date
  - Thread