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Non-linear material in frequency domain

Posted Aug 9, 2019, 9:44 a.m. EDT Electromagnetics, Low-Frequency Electromagnetics 4 Replies

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Hi, I want to apply a non linear material property (BH curve) for a material to be solved in magnetic and electric fields and frequency domain study. can anyone suggest how to impose the non-linear material property to the material properties. Thank you in advance.

4 Replies Last Post Jan 30, 2020, 10:13 a.m. EST
Dave Greve Certified Consultant
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Posted: 5 years ago Aug 9, 2019, 10:59 a.m. EDT
Updated: 5 years ago Aug 9, 2019, 10:58 a.m. EDT

Some COMSOL modules (including the mf, or magnetic fields module) have a small signal analysis, frequency domain option as one of the studies.

This is what you want.

D.W. Greve DWGreve Consulting

Some COMSOL modules (including the mf, or magnetic fields module) have a *small signal analysis, frequency domain* option as one of the studies. This is what you want. D.W. Greve DWGreve Consulting
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Posted: 5 years ago Aug 19, 2019, 9:28 a.m. EDT
Updated: 5 years ago Aug 20, 2019, 2:10 a.m. EDT

Hi, Firstly, I thank you for the reply. Actually I want to define the non-linear magnetic material by giving BH curve under the material section for a problem to be solved in frequency domain. But when i am running the solver it shows a error that "use effective BH curve in the frequency domain". (error is shown in the image) Then I tried to create a effective BH curve from the original BH curve by using " Effective Nonlinear Magnetic Curves Calculator App" . Now in the post processing, theoretically the results should be in accordance with the original BH curve. But the results are following effective BH curve. Can you give suggestions to this problem?

Hi, Firstly, I thank you for the reply. Actually I want to define the non-linear magnetic material by giving BH curve under the material section for a problem to be solved in frequency domain. But when i am running the solver it shows a error that "use effective BH curve in the frequency domain". (error is shown in the image) Then I tried to create a effective BH curve from the original BH curve by using " Effective Nonlinear Magnetic Curves Calculator App" . Now in the post processing, theoretically the results should be in accordance with the original BH curve. But the results are following effective BH curve. Can you give suggestions to this problem?

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Wael Elsaady
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Posted: 4 years ago Jan 24, 2020, 11:01 a.m. EST

Hi,

I have the same problem. I think there is something should be done in the study step. Have you sorted it out? I tried the information in the following link but it didn't work.

https://uk.comsol.com/model/download/684901/Effective_HB_or_BH_Curve_Comparison_55.pdf

Regards Wael

Hi, I have the same problem. I think there is something should be done in the study step. Have you sorted it out? I tried the information in the following link but it didn't work. https://uk.comsol.com/model/download/684901/Effective_HB_or_BH_Curve_Comparison_55.pdf Regards Wael
Lars Dammann COMSOL Employee

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Posted: 4 years ago Jan 30, 2020, 10:13 a.m. EST

Hi,

it is not really possible to compute nonlinear magnetic materials in the frequency domain. The frequency domain approach makes the assumption that the entire solution has the time dependence , but this is simply not true for nonlinear materials. If you put a nonlinear iron yoke in a coil, which is driven by a sinusoidal current, the resulting magnetic field will not be sinusoidal. The effective BH-curve tries to approximate the real fields in the nonlinear material by evening-out the error over the time period, but it is still a simplification.

If you need the exact fields at all times, you should perform a time-dependent simulation. See this model for an example: https://www.comsol.com/model/e-core-transformer-14123

Dave is right though, that you can perform a small signal analysis, if your harmonic excitation is so small, that the fields only covers a very small part of the BH-curve such that the problem can be linearized.

Hope this helps, Lars

Hi, it is not really possible to compute nonlinear magnetic materials in the frequency domain. The frequency domain approach makes the assumption that the entire solution has the time dependence A=\tilde{A}\cdot\exp(j\,\omega\,t), but this is simply not true for nonlinear materials. If you put a nonlinear iron yoke in a coil, which is driven by a sinusoidal current, the resulting magnetic field will not be sinusoidal. The effective BH-curve tries to approximate the real fields in the nonlinear material by evening-out the error over the time period, but it is still a simplification. If you need the exact fields at all times, you should perform a time-dependent simulation. See this model for an example: https://www.comsol.com/model/e-core-transformer-14123 Dave is right though, that you can perform a small signal analysis, if your harmonic excitation is so small, that the fields only covers a very small part of the BH-curve such that the problem can be linearized. Hope this helps, Lars

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