Discussion Forum

Hi Joao,

Seems like the B-H-curve is included in the model through the material library, provided you also have the AC/DC module. (I guess the model itself is also a part of the module, meaning you do have the module.) So, you can go to the model physics settings (subdomain) and find the material parameters, go browse the library and press "plot" at the B-H-curve properties. (Similarly I believe you can just plot the curve in post-processing, by inputting the proper variable names as x- and y-axis data.)

Here's a straight quote from the model documentation:

The material in the stator and the center part of the rotor has a nonlinear relation between the magnetic flux, B and the magnetic field, H, the so called B-H curve. In COMSOL Multiphysics, the B-H curve is introduced as an interpolation function; see Figure 2. The function can be used in the subdomain settings. Usually B-H curves are specified as | B | versus | H |, but the perpendicular waves application mode must have | H | versus | B |. It is therefore important that the H-data is entered as f(x)-data of the interpolation function and the B-data entered as x-data. This relationship for | H | is predefined for the material Soft Iron (without losses) in the materials library that is shipped with the AC/DC Module, acdc_lib.txt.

Hth,
Antti

Can anybody inform me how the achieve the B-H Curve shown in the generator 2D presented in the MODEL GALLERY?
www.comsol.com/showroom/documentation/model/2122/

tried to find this model, but it seems it has disappeared.

the new link style www.comsol.com/showroom/gallery/2122/ doesn't work either

Hi

if you try "B-H Curve" on the mainCOMSOL site you arrive among others to:

www.comsol.eu/support/knowledgebase/852/ a bit oldish but still valid for the methodology
www.comsol.eu/showroom/gallery/6063/

and these papers
www.comsol.eu/search/?s=+B-H+Curve+&subset=papers_presentations

and more depending on how you search ...

--
Good luck
Ivar

www.comsol.eu/showroom/gallery/6063/

In this model, (2D axisymmetric),

subdomain #2 uses the constitutive relation H = f(|B|)eB, with the

norm of the magnetic field |H| = HB(normB_emqa[1/T]) [A/m]

subdomain #3 uses the same constitutive relation, but the

norm of the magnetic field |H| = HBFe(normB_emqa[1/T]) [A/m]


Is this constitutive relation only available under 2D axisymmetric? I don't recall seeing it in 3D.

HBFe is user defined under Functions, but where is HB function defined?

images of settings in question:
sub2, img814.imageshack.us/img814/5880/sub2.jpg
sub3, img10.imageshack.us/img10/9688/sub3h.jpg