Homogenized Multiturn causing tolerance issues

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Hello,

I am currently simulating my model using the Coil Geometry Analysis study in COMSOL. When I select the Single Conductor option for the coil, the analysis runs successfully.

However, I would like to proceed with a Time-Dependent study, which requires using the Homogenized Multiturn coil model. Since I have already modeled all the turns explicitly in the geometry, I set N = 1. But when I switch to the homogenized multiturn option and run the Coil Geometry Analysis, the solver returns the error “Failed to find a solution.”

Could you please suggest how to resolve this issue?

Thank you for your support.



7 Replies Last Post 16 mar 2026, 18:49 GMT-4
Edgar J. Kaiser Certified Consultant

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Posted: 1 week ago 9 mar 2026, 09:49 GMT-4

You can run a time-dependent study with the single conductor coil.

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
You can run a time-dependent study with the single conductor coil.

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Posted: 7 days ago 10 mar 2026, 01:36 GMT-4

I am working with a planar-type coil modeled as a solid conductor in COMSOL. The coil is excited using a sinusoidal voltage source through an external I–U coupling.

The Coil Geometry Analysis study runs successfully. However, when I attempt to run a Time Dependent study, COMSOL returns the error:

"Current excitation is not supported in single conductor coils in time dependent studies."

To troubleshoot, I also tried removing the external circuit and directly applying a current excitation in the coil, but the same issue persists.

I have attached the corresponding .mph file for reference.

Could you please help me understand how to correctly set up the coil excitation for a time dependent study in this case?

Thank you for your time and assistance.

Best regards, Anushka Mahajan

I am working with a planar-type coil modeled as a solid conductor in COMSOL. The coil is excited using a sinusoidal voltage source through an external I–U coupling. The Coil Geometry Analysis study runs successfully. However, when I attempt to run a Time Dependent study, COMSOL returns the error: **"Current excitation is not supported in single conductor coils in time dependent studies."** To troubleshoot, I also tried removing the external circuit and directly applying a current excitation in the coil, but the same issue persists. I have attached the corresponding .mph file for reference. Could you please help me understand how to correctly set up the coil excitation for a time dependent study in this case? Thank you for your time and assistance. Best regards, Anushka Mahajan


Edgar J. Kaiser Certified Consultant

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Posted: 7 days ago 10 mar 2026, 03:55 GMT-4
Updated: 6 days ago 10 mar 2026, 09:56 GMT-4

Anushka,

this coil geometry is not well suited for a multiturn coil. The coil geometry analysis has a very hard task to determine the current direction. The current excitation adds extra numerical complexity. Try the single conductor with voltage excitation. If possible make sure the time dependent voltage starts at zero and not at a non-zero value, to make convergence easier at the start of the time dependent step.

Cheers Edgar

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Anushka, this coil geometry is not well suited for a multiturn coil. The coil geometry analysis has a very hard task to determine the current direction. The current excitation adds extra numerical complexity. Try the single conductor with voltage excitation. If possible make sure the time dependent voltage starts at zero and not at a non-zero value, to make convergence easier at the start of the time dependent step. Cheers Edgar

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Posted: 5 days ago 12 mar 2026, 07:46 GMT-4

Dear Sir,

Thank you very much for your guidance.

Even after using the Solid Conductor settings with a sinusoidal voltage excitation, the convergence plot is becoming constant instead of converging. I am unsure why the solver is behaving this way.

Could you please guide me on how to resolve this issue?

Thank you very much for your time and support.

Kind regards, Anushka Mahajan

Dear Sir, Thank you very much for your guidance. Even after using the Solid Conductor settings with a sinusoidal voltage excitation, the convergence plot is becoming constant instead of converging. I am unsure why the solver is behaving this way. Could you please guide me on how to resolve this issue? Thank you very much for your time and support. Kind regards, Anushka Mahajan


Edgar J. Kaiser Certified Consultant

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Posted: 4 days ago 12 mar 2026, 12:34 GMT-4

Anushka,

the solver is performing as expected. You set a strict time step of 1e-7 s and the time stepping converges to an inverse time step of 1e7 and remains there. That is how it is to be expected. Now let it run for the 5e-5 s you set.

Cheers Edgar

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Anushka, the solver is performing as expected. You set a strict time step of 1e-7 s and the time stepping converges to an inverse time step of 1e7 and remains there. That is how it is to be expected. Now let it run for the 5e-5 s you set. Cheers Edgar

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Posted: 16 hours ago 16 mar 2026, 05:29 GMT-4

Dear Sir,

After proceeding with the complete 3D design and implementing the necessary changes as discussed, the study is now showing the following error:

"Failed to find a solution. Unable to read or write out-of-core file. Returned solution is not converged. Not all parameter steps returned."

Although sufficient system storage is available, I am still unable to successfully run the simulation.

Could you please guide me on how to resolve this issue?

Thank you.

Best regards, Anushka

Dear Sir, After proceeding with the complete 3D design and implementing the necessary changes as discussed, the study is now showing the following error: *"Failed to find a solution. Unable to read or write out-of-core file. Returned solution is not converged. Not all parameter steps returned."* Although sufficient system storage is available, I am still unable to successfully run the simulation. Could you please guide me on how to resolve this issue? Thank you. Best regards, Anushka


Edgar J. Kaiser Certified Consultant

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Posted: 3 hours ago 16 mar 2026, 18:49 GMT-4

Hi Anushka,

this has become much more complex now. I tried to run it and I don't get this error. It takes over 32 GB of RAM. Are you sure you have enough RAM in your machine? It should be 48 or 64 GB to be on the safe side.

However, the time dependent solver starts but isn't converging. Due to the iron core the model is now nonlinear which makes convergence more difficult.

Another issue is the pulse function you apply. The time stepping of the solver must resolve any time dependent loading. The pulse rise and fall times of 1e-12 s are much too fast. Also your device would never really follow such a pulse.

There may be more issues, e.g. in the mesh, that compromise convergence.

I am sorry having to tell you that this is getting far beyond the scope of a forum discussion. I am always happy to give hints, but I cannot do the bulk work in a modeling project.

This model will probably require a lot of time for fixing and optimization and I cannot afford to devote such a lot of time to that.

One advice I can give is to try to simplify the model geometry while keeping all essential aspects in it and try to get it to converge. Once you achieve that, increase the complexity while you try to maintain convergence. This time you changed a couple of aspects in one step. You included the nonlinear core, modified the geometry and changed excitation. Don't do it that way. Change one thing, get it to work, then change the next thing. Step by step.

Make sure your computer has sufficient RAM-memory.

Good luck

Edgar

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Hi Anushka, this has become much more complex now. I tried to run it and I don't get this error. It takes over 32 GB of RAM. Are you sure you have enough RAM in your machine? It should be 48 or 64 GB to be on the safe side. However, the time dependent solver starts but isn't converging. Due to the iron core the model is now nonlinear which makes convergence more difficult. Another issue is the pulse function you apply. The time stepping of the solver must resolve any time dependent loading. The pulse rise and fall times of 1e-12 s are much too fast. Also your device would never really follow such a pulse. There may be more issues, e.g. in the mesh, that compromise convergence. I am sorry having to tell you that this is getting far beyond the scope of a forum discussion. I am always happy to give hints, but I cannot do the bulk work in a modeling project. This model will probably require a lot of time for fixing and optimization and I cannot afford to devote such a lot of time to that. One advice I can give is to try to simplify the model geometry while keeping all essential aspects in it and try to get it to converge. Once you achieve that, increase the complexity while you try to maintain convergence. This time you changed a couple of aspects in one step. You included the nonlinear core, modified the geometry and changed excitation. Don't do it that way. Change one thing, get it to work, then change the next thing. Step by step. Make sure your computer has sufficient RAM-memory. Good luck Edgar

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