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ACDC: Failed to simulate when using BH/HB/MuR curves

Posted 16.01.2011, 19:45 GMT-5 Low-Frequency Electromagnetics Version 4.1 5 Replies

Mohammed Darwish
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Hello,

I've been trying to simulate a magnetic field using a table for the BH, HB and MuR curves. I've defined an interpolation function for the BH curve, HB Curve and for the relative permeability, yet it cannot simulate. I get the following errors:

"Failed to evaluate variable.
- Variable: normB
- Geometry: 1
- Domain: 3 4
Failed to evaluate variable.
- Variable: mod1.mf.murzz
- Defined as: mod1.mat3.def.MUR_B((normB/unit_T_cf))
Failed to evaluate variable.
- Variable: mod1.mf.murinvzz
- Defined as: (1/mod1.mf.murzz)
Failed to evaluate variable.
- Variable: mod1.mf.Hz
- Defined as: ((mod1.mf.murinvzz*mod1.mf.Bz)/mu0_const)
Failed to evaluate expression.
- Expression: d((2*(mod1.mf.Hr*test(mod1.Aphiz)-mod1.mf.Hz*(test(mod1.Aphir)+if(abs(r)<0.0010*h,d(test(mod1.Aphi),r),test(mod1.Aphi)/r)))*pi*r)*(dvol),{test@2})
"

Attached is the model for your reference. All your help is much appreciated.

Regards,
Mohammed

Attachments:

5 Replies Last Post 13.07.2011, 16:34 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 17.01.2011, 00:57 GMT-5
Hi

you define the material properties in the "ampere law" sub-node. But if you have different materials with different properties you must add a second, third etc node and set up the physics accordingly (B-H depedent).

Note too, in v4.1 you have the advanceds , single and multi-turn coil BC, check the doc for the subtilities

--
Good luck
Ivar
Hi you define the material properties in the "ampere law" sub-node. But if you have different materials with different properties you must add a second, third etc node and set up the physics accordingly (B-H depedent). Note too, in v4.1 you have the advanceds , single and multi-turn coil BC, check the doc for the subtilities -- Good luck Ivar
Mohammed Darwish
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Posted: 1 decade ago 17.01.2011, 08:30 GMT-5
Hello Ivar,

Thanks for your reply. I've did what you said and it worked out, there is still a problem with the results nonetheless; While using a material with relative permeability of 600, the field is increased only 2 times!

I've tried a material I defined my self (Steel 1010) and tried the material library provided (Soft iron without losses) but in vain. Is there a problem in my definition of the BH curve?

Attached is my model after the corrections you cited earlier.

Another note about the multi-turn coil condition; what does the number of turns mean if have many coils a top of each other? Does just work as a current multiplier?

Regards,
Mohammed
Hello Ivar, Thanks for your reply. I've did what you said and it worked out, there is still a problem with the results nonetheless; While using a material with relative permeability of 600, the field is increased only 2 times! I've tried a material I defined my self (Steel 1010) and tried the material library provided (Soft iron without losses) but in vain. Is there a problem in my definition of the BH curve? Attached is my model after the corrections you cited earlier. Another note about the multi-turn coil condition; what does the number of turns mean if have many coils a top of each other? Does just work as a current multiplier? Regards, Mohammed

Attachments:

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 18.01.2011, 16:14 GMT-5
Hi

first of all in our steel example, you have choosen (by default "Constant" for the BH extrapolation. I believe you should rather use linear.

Then you need to ramp up the curent to some 4000 to 10000[A] to see some effect, but I'm afraid your coil wire will melt before you arrive at those levels, in real life, no ? no danger in COMSOL ;)

One thing that puzzles me, the built in soft iron has both BH and HB curves, you only HB, but then the builtin has both normH and normB defined, and COSMOL selects two properties for the built soft iron with losses "HB and normH", but only 1 properties (HB) for your steel (the green check marks) that puzze me. But as both define normH and probably the material selection decides which one, it is probably normal.


--
Good luck
Ivar
Hi first of all in our steel example, you have choosen (by default "Constant" for the BH extrapolation. I believe you should rather use linear. Then you need to ramp up the curent to some 4000 to 10000[A] to see some effect, but I'm afraid your coil wire will melt before you arrive at those levels, in real life, no ? no danger in COMSOL ;) One thing that puzzles me, the built in soft iron has both BH and HB curves, you only HB, but then the builtin has both normH and normB defined, and COSMOL selects two properties for the built soft iron with losses "HB and normH", but only 1 properties (HB) for your steel (the green check marks) that puzze me. But as both define normH and probably the material selection decides which one, it is probably normal. -- Good luck Ivar
Attila Felföldi
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Posted: 1 decade ago 07.06.2011, 08:37 GMT-4

Hello Ivar,

Thanks for your reply. I've did what you said and it worked out, there is still a problem with the results nonetheless; While using a material with relative permeability of 600, the field is increased only 2 times!

I've tried a material I defined my self (Steel 1010) and tried the material library provided (Soft iron without losses) but in vain. Is there a problem in my definition of the BH curve?

Attached is my model after the corrections you cited earlier.

Another note about the multi-turn coil condition; what does the number of turns mean if have many coils a top of each other? Does just work as a current multiplier?

Regards,
Mohammed


Hi Mohammed,

did you resolve your problem? I have a same problem in simulating a synchronous motor...

Thank you in advance,
Attila
[QUOTE] Hello Ivar, Thanks for your reply. I've did what you said and it worked out, there is still a problem with the results nonetheless; While using a material with relative permeability of 600, the field is increased only 2 times! I've tried a material I defined my self (Steel 1010) and tried the material library provided (Soft iron without losses) but in vain. Is there a problem in my definition of the BH curve? Attached is my model after the corrections you cited earlier. Another note about the multi-turn coil condition; what does the number of turns mean if have many coils a top of each other? Does just work as a current multiplier? Regards, Mohammed [/QUOTE] Hi Mohammed, did you resolve your problem? I have a same problem in simulating a synchronous motor... Thank you in advance, Attila
Felix Vega
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Posted: 1 decade ago 13.07.2011, 16:34 GMT-4
Hi, any progress on this issue?
Thanks
Hi, any progress on this issue? Thanks

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