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Prescribing current density obtained from previous step.

Posted Nov 21, 2018, 11:52 a.m. EST Low-Frequency Electromagnetics 7 Replies

Sergey Kuznetsov
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Hello! I have a complex geometry and at Step 1 would like to prescribe total electric current entering this geometry and solve for current density distribution within this geometry. I believe I can use electric currents(ec) interface at this step.

At step 2 I would like to prescribe current distribution on the same geometry and solve for magnetic fields using MagneticFields(mf) interface.

I was wondering how can prescribe current distrubution at second Step, using results from the first step? How do I manage different interfaces (electric currents(ec) and Magnetic Fields(mf))? Is there a comsol model showing how to do such simulation?

Thank you!

7 Replies Last Post Nov 28, 2018, 1:42 p.m. EST
Sergei Yushanov Certified Consultant
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Posted: 5 years ago Nov 21, 2018, 1:05 p.m. EST

Sergey,

In mf physics, you can use External Current Density domain node with J={ec.Jx,ec.Jy,ec.Jz}, as shown in the attached mph file.

Regards, Sergei

Sergey, In mf physics, you can use External Current Density domain node with J={ec.Jx,ec.Jy,ec.Jz}, as shown in the attached mph file. Regards, Sergei

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Sergey Kuznetsov
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Posted: 5 years ago Nov 21, 2018, 2:32 p.m. EST
Updated: 5 years ago Nov 21, 2018, 2:37 p.m. EST

Sergei, thank you for your reply. Unfortunately I can't open your model, I have access to an older version of comsol, 5.2.

I believe that I already tried the approach you mention. However, i can do it only for simple geometries, where i know analytical expression for the current density components. For more complex shapes on the conducting region I don't know distribution of the current density and I need to find it.

I found that I might be able to use coil feature with coil geometry analysis step. And it seems to work for 3d setup. The coil geometry analysis gives me current density distribution within my conductor region. However, I can't propagate it the the next step where I'm finding magnetic field. Another problem with Coil geometry analysis step is that I can't used in my 2d axisymmetrical setting, since my current are in plane.

Sergei, thank you for your reply. Unfortunately I can't open your model, I have access to an older version of comsol, 5.2. I believe that I already tried the approach you mention. However, i can do it only for simple geometries, where i know analytical expression for the current density components. For more complex shapes on the conducting region I don't know distribution of the current density and I need to find it. I found that I might be able to use coil feature with coil geometry analysis step. And it seems to work for 3d setup. The coil geometry analysis gives me current density distribution within my conductor region. However, I can't propagate it the the next step where I'm finding magnetic field. Another problem with Coil geometry analysis step is that I can't used in my 2d axisymmetrical setting, since my current are in plane.
Sergei Yushanov Certified Consultant
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Posted: 5 years ago Nov 21, 2018, 3:18 p.m. EST

Sergey,

No, you don't need to know analytical expression for the current density. This approach works for any geometry. Hopefully, you will be able to open attached file this time.

Regards,

Sergei

Sergey, No, you don't need to know analytical expression for the current density. This approach works for any geometry. Hopefully, you will be able to open attached file this time. Regards, Sergei

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Sergey Kuznetsov
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Posted: 5 years ago Nov 21, 2018, 3:37 p.m. EST
Updated: 5 years ago Nov 21, 2018, 3:43 p.m. EST

Sergei, thank you so much! I can open it now. I see now, you're using Electric Current interface simultaneously with Magnetic Fields. Will try to do it with my geomtry.

Sergei, you're prescribing electric potential difference at the ends of your conductor. Is it possible to prescribe total current entering or leaving conductor? I couldn't do it in the Electric Current Interface.

Sergei, thank you so much! I can open it now. I see now, you're using Electric Current interface simultaneously with Magnetic Fields. Will try to do it with my geomtry. Sergei, you're prescribing electric potential difference at the ends of your conductor. Is it possible to prescribe total current entering or leaving conductor? I couldn't do it in the Electric Current Interface.
Sergei Yushanov Certified Consultant
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Posted: 5 years ago Nov 21, 2018, 3:45 p.m. EST

Sergey,

Well, I am specifying total current entering the electrode using Terminal boundary condition. Antother way to prescribe total current entering conductor is to use Normal Current Density node to obtain the same result.

Regards,

Sergei

Sergey, Well, I am specifying total current entering the electrode using Terminal boundary condition. Antother way to prescribe total current entering conductor is to use Normal Current Density node to obtain the same result. Regards, Sergei
Sergey Kuznetsov
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Posted: 5 years ago Nov 21, 2018, 6:48 p.m. EST

Sergei, great thanks for your help! It seems to work now!

Sergei, great thanks for your help! It seems to work now!
Sergey Kuznetsov
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Posted: 5 years ago Nov 28, 2018, 1:42 p.m. EST

Sergei I was able to do what I wanted by prescribing {ec.Jx,ec.Jy,ec.Jz} from ec node in my axisymmetric model(Figure 1), thanks to your suggestion.

However, then I realized that it is not exactly what I need to do. What I need to do is prescribing homogeneous current density across the conductor as it happens for Comsol's coil feature with homogenized multi-turn conductor model, as shown on Figure 3 for circular geometry of conductor. I can use coil feature with homogenized multi-turn conductor model in 3d, but can't do it in 2d axisymmetric setting, as coil feature works only for out-of-plane components of current density, while I'm interested in prescribing in-plane components Jz and Jr. I was wondering if you know if there is any way to prescribe homogeneous in-plane current density along the conductor 2d?

Thank you!

Sergei I was able to do what I wanted by prescribing {ec.Jx,ec.Jy,ec.Jz} from ec node in my axisymmetric model(Figure 1), thanks to your suggestion. However, then I realized that it is not exactly what I need to do. What I need to do is prescribing homogeneous current density across the conductor as it happens for Comsol's coil feature with homogenized multi-turn conductor model, as shown on Figure 3 for circular geometry of conductor. I can use coil feature with homogenized multi-turn conductor model in 3d, but can't do it in 2d axisymmetric setting, as coil feature works only for out-of-plane components of current density, while I'm interested in prescribing in-plane components Jz and Jr. I was wondering if you know if there is any way to prescribe homogeneous in-plane current density along the conductor 2d? Thank you!

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