Re: [femm] Modelling loudspeaker magnets..

[Dave Squires <djsquires@xxxxxxxx>]

Send me your file and I will have a look.
It is really pretty simple once you know how to do it.
It should just take a minute to set up your case.
I have another one I built in the last few minutes.

Here it is. You should be able to just run it.

Dave Squires

emacoustics wrote:

> Hello folks,
>
> I'm kind of new to using FEMM, and am trying to model a loudspeaker
> coil/magnet assembly for my final year university project. I'm
> modelling to observe the effect the flux generated by the coil has on
> the permanent magnetic field. The model is really simple - one block
> of steel, one block of Neodinium, and one (and sometimes two) coils
> (which are represented by square blocks at present, though may get
> changed to circles) in the gap between them. My problem is in not
> understanding how to input data for magnets - I modelled the system
> with no current in the coil (and with no coil at all) expecting to
> see field lines between the neodinium and the steel, and saw
> nothing. When looking at material properties, there are lots of
> values for constants I don't understand, nor did I really understand
> the manual either. Can anybody point me in the right direction? The
> model is just to show that the coil affects the permanent field when
> a current runs through it, and by adding a seconc coil in antiphase
> this can reduce this problem.
>
> Many many thanks, I'm getting desperate!
>
> Best Wishes,
>
> Mike Wheeler
> Final Year Undergraduate, BEng Mechanical Engineering
> Imperial College, London
>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

[Format] = 3.0
[Frequency] = 0
[Precision] = 1e-008
[LengthUnits] = inches
[ProblemType] = planar
[Coordinates] = cartesian
[Comment] = "Add comments here."
[PointProps] = 0
[BdryProps] = 0
[BlockProps] = 5
<BeginBlock>
<BlockName> = "Air"
<Mu_x> = 1
<Mu_y> = 1
<H_c> = 0
<H_cAngle> = 0
<J_re> = 0
<J_im> = 0
<Sigma> = 0
<d_lam> = 0
<Phi_h> = 0
<LamType> = 0
<LamFill> = 1
<BHPoints> = 0
<EndBlock>
<BeginBlock>
<BlockName> = "NdFeB 40 MGOe"
<Mu_x> = 1.0489999999999999
<Mu_y> = 1.0489999999999999
<H_c> = 979000
<H_cAngle> = 0
<J_re> = 0
<J_im> = 0
<Sigma> = 0.66700000000000004
<d_lam> = 0
<Phi_h> = 0
<LamType> = 0
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<BHPoints> = 0
<EndBlock>
<BeginBlock>
<BlockName> = "M-19 Steel"
<Mu_x> = 4416
<Mu_y> = 4416
<H_c> = 0
<H_cAngle> = 0
<J_re> = 0
<J_im> = 0
<Sigma> = 0
<d_lam> = 0
<Phi_h> = 0
<LamType> = 0
<LamFill> = 1
<BHPoints> = 13
0	0
0.29999999999999999	39.78875
0.80000000000000004	79.577500000000001
1.1200000000000001	159.155
1.3200000000000001	318.31
1.46	795.77499999999998
1.54	1591.55
1.6187499999999999	3376.6669999999999
1.74	7957.75
1.8700000000000001	15915.5
1.99	31831
2.0459640000000001	55102.040000000001
2.0800000000000001	79577.5
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<BeginBlock>
<BlockName> = "coil-minus"
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<J_re> = -10
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<Phi_h> = 0
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