Re: [femm] about magnetization of magnets

[Dave Squires <djsquires@xxxxxxxx>]

I have found the same thing, but there is not much you
can do about it. FEMM assumes that the magnetization
direction and/or angle specified applies to the entire
block. Therefore, if you want a changing angle of magnetization
you have to break the magnet up into sections with incremental
angle changes to mimic a changing angle of magnetization.
I have made up toroidal magnets with a circular magnetization
this way. The easiest way is to make up the geometry and
put in one property. Then you copy it radially and the
angle will change automatically. If you need alternating
polarities then copy two magnets radially at twice the
angle of one alone. It's actually very easy to do once
you know how.

Regards,
Dave Squires

Ramdane LATEB wrote:
> hello femm's members,
>
> My question is about magnetization of magnets, it seems
> that the magnetization in femm depends on the number of 
> subdivisions in magnets, I mean even if I put a radial 
> magnetization in the middle of a span magnet, this seems 
> true if the span is very small, but if the span is important 
> I have to split the magnet into sub-magnets. What (I think)
> I have understood is that it's rather a global magnetization,
> more largest the span is, more parallel the magnetization
> is, and less largest the span is, more radial the magnetization
> is, so to have a radial magnetization I have to split the 
> magnet into sub-magnets. I 'm wondering if someone else have 
> observed this phenomenon in femm (perhaps it has been discussed 
> before, if so , thank you to direct me to the corresponding 
> messages). or your own experience, trie with a span magnet 
> of 150° (electrical), with out splitting the magnet, and 
> look to the back fem (or magnetic flux) in one tooth and 
> the cogging torque (no load), and make the same when splitting 
> the magnet in four (I mean splitting ,by just adding radial 
> segments and adding a radial magnetization in each created 
> sub magnet, and use a same mesh to approach the number of 
> global nodes), the difference is rather observed in both 
> cogging an tooth magnetic flux.
>
> Any advice is welcome, thank you
>
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