problems with "StatMagSolve"

[dak]

Hello
Recently, I have been doing some electromagnetic calculations. I was going to write an article. I used Elmer for heat computations. But when I tried to do some tests, Elmer gave me strange results.

I want to check if the joule heat is changing correctly with a depth. But to my surprise, it does not. For example, let's try this problem, which I have attached.

You will get this results:



and :



But if you use this equation:

d=sqrt(2/omega/mi/sigma) you will get different point coordinates for value of Joule Heat on the boundary divide by 2.716.

It seems that magnetic permeability is defined with a value, which should be multiple by 0,0404 to get correct results from Elmer.

Also, it is very interesting that the value of Permeability of Vacuum in Constants section cannot be changed. I have tried many values, without any progress. Elmer still uses a strange value (Permeability of Vacuum /0.404 ?)

For example: when I put in sif file :

Code: Select all

Magnetic Permeability = $1.2566370614359173e-6 * 100*0.0404

I get joule heat value for problem boundary = 10349030304. Then I found a coordinate with value = 10349030304/e. It is for x = 0.19601373541

then I found skin depth = 0.2 - x =0.00398626459. I try to check if angular frequency has correct value:

2/d**2/sigma/mi;

and I got = angular frequency from elmer's results = 5007 (should be 5120) so it's ok. But I have to multiple permeability by this strange value. Another problem is that Joule Heat and Magnetic Flux are not changing in the same way. Could you tell me what is wrong. Maybe there are some errors in StatMagSolve procedure.

Best Regards
Daniel

[raback]

Hi

Perhaps you used frequency instead of angular frequency in your formula. This results to a skin depth difference of 1/sqrt(2*pi)=0.399 which is rather close to the value 0.404 that you were looking for.

The "Permeability of Vacuum" was read from wrong field. It has now been changed in svn revision 5050. Thanx for reporting!

-Peter

[dak]

Hello,
Thanks for answer. I use the "angular frequency" statement in Solver section. The "Frequency" do not work for StatMagSolve.

I suppose that wrong value of permeability is the reason of wrong results. That value I have found is = 0,404.

When the newer version for windows could be realese?

Thank you for your help.

Regards
Daniel Kucharski

[raback]

Hi Daniel

I use the "angular frequency" statement in Solver section. The "Frequency" do not work for StatMagSolve.

Ok, I checked the code and there the "angular frequency" is used as it was "frequency" i.e. its internally multiplied by 2*pi.
Perhaps I have to alter this convention and particularly document it more clearly.

When the newer version for windows could be realese?

You don't need that. If you want to experiment with vacuum permeability just place it in the Simulation section for time being.

-Peter

[dak]

Hello
I have another question. Is there any possibility to compute current from StatMagSolve module results? Maybe I could use StatCurrentSolver? I would like to know what current density i have in my object.

Regards
DK