Electromagnetic Theory (in plain language)

[SparWeb]

I thought I would share this link with the forum:

http://info.ee.surrey.ac.uk/Workshop/advice/coils/index.html

The tutorial is geared toward people building transformers/inductors, but the principles involved in winding alternator coils and building generators are basically the same.

Something else I learned is the typical saturation flux for iron: about 1.6 Tesla.

Wow, I'm afraid I have saturated stator laminates in my induction motor conversion, then, because the FEMM model predicted over 2 Teslas.  The stator simply won't "conduct" that much flux.  (Saturation, by the way, is the term used where a material simply won't accept more lines of magnetic flux.)

Click on the screen-shot to see it full size.

(Actually I used rectangular bars, not the arc segments shown in this model - it's just a graphic I generated when comparing.  The blocks cause even more saturation!)

[dinges]

Thanks for the link Steven.

One question: what software is it you use for electro-magnetic FEM analysis ? I've tried in the past modeling with mech. eng. FEM packages and that wasn't succesful (though should be doable). I'd be interested in learning what software it is and whether the learning curve is steep (for someone already with FEM).

I had noticed it before in this link (http://www.powercroco.de/magnetkreis.html), which triggered my interest. Nothing beats a bit of quick on-screen analysis and playing around with parameters (size of magnets, airgap, etc.)

I'm a little surprized by your field strenghts (1.65-2 T); I recall Neo magnets having a field strength (at their surface) of about 1.2 T (varies with grade); is the tooth saturation a consequence of the 'focusing'/attraction of the magnetic field lines by the stator tooth ? I.e., half of the stator is iron, half is air, so field strength in the tooth is doubled ? (minus a little for airgap between the magnet and rotor)

I definitely need to brush up on this part of theory...

Regards,

Peter.

[dinges]

Peter needs to learn to google before asking...
It's FEMM (Finite Element Method Magnetics) (------------broken link removed-----------) and can be downloaded free here:
 (------------broken link removed-----------)

Peter.

 (------------Edit by Sparweb: old link was broken.  See current link below.-----------)

[WindyOne]

Peter needs to learn to google before asking...
It's FEMM (Finite Element Method Magnetics) ("wiki.4hv.org/index.php/FEMM") and can be downloaded free here:
"femm.foster-miller.net/wiki/HomePage"
Peter.

When I try to access the Foster Miler website my Anti-Virus program ( ESET NOD32 ) BLOCKS all access to that web page ...
Potentially unwanted content found
This web page is on our list of websites with uncertain reputation or potentially unwanted content and has been BLOCKED!

Can anyone confirm that the "femm.foster-miller.net" is a valid and virus-free website?
If OK, then I will add "Foster-Miller" to my Allowed List.
And I will notify ESET NOD32 that they are displaying a "False-Positive".

It is possible that the Foster-Miller website is no longer functional ...

[Scruff]

"Does this smell like chloroform?" 

Link not working for me, no virus flagged (Avast) but not a secure site either.

[SparWeb]

Hi WindyOne,
I checked up on the old link - thank you WindyOne for bringing the issue to my attention!
I sort-of recall using the foster-miller website to get FEMM  a long time ago.  It's an old dead link now.

Get FEMM here:  https://www.femm.info/wiki/HomePage

Still great software to use as a learning and/or design tool.