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Reference edge (current) direction in a multi-turn coil domain
Posted Aug 3, 2015, 9:24 a.m. EDT Low-Frequency Electromagnetics Version 5.0 3 Replies
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Hello,
I have designed a simple curved saddle coil pair in Comsol directly by using some blocks and boolean operators. After adding "Magnetic Fields" as physics to that component I created two domain multi-turn coils and switched the coil type to "circular" because I want the current flowing along the edge you can see in my attached image file. My problem is that I can not find a way to manipulate the current direction in this specific model because Comsol seems to choose the direction on each edge automatically. Like you can see in the screenshot (attached file) the resulting current direction is not circular anymore. The edge direction changes on the given path. I tried to solve this problem by using virtual operators but I could not find a solution until now. I hope anybody is able to help me.
Thank you in advance.
I have designed a simple curved saddle coil pair in Comsol directly by using some blocks and boolean operators. After adding "Magnetic Fields" as physics to that component I created two domain multi-turn coils and switched the coil type to "circular" because I want the current flowing along the edge you can see in my attached image file. My problem is that I can not find a way to manipulate the current direction in this specific model because Comsol seems to choose the direction on each edge automatically. Like you can see in the screenshot (attached file) the resulting current direction is not circular anymore. The edge direction changes on the given path. I tried to solve this problem by using virtual operators but I could not find a solution until now. I hope anybody is able to help me.
Thank you in advance.
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3 Replies Last Post Aug 21, 2015, 9:07 a.m. EDT
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Posted:
9 years ago
Hi
the "Coil Geometry" sub node has undergone a few changes over the last versions so you need to check your ACDC doc carefully.
Normally you should select a "rounded/fileted edge" shape giving the average length of the coil. In your case you have sharp edges and just the internal section, therefore your coil length calculations will be quite wrong, and the loop arrows look also wrong indeed. You could draw a loop (circular or a rectangle with fillets) in the middle of your volumes.
But it looks like you have a deformed coil wit a non planar shape, not sure how to correctly define that. Probably you should send the request directly to "Support".
--
Good luck
Ivar
the "Coil Geometry" sub node has undergone a few changes over the last versions so you need to check your ACDC doc carefully.
Normally you should select a "rounded/fileted edge" shape giving the average length of the coil. In your case you have sharp edges and just the internal section, therefore your coil length calculations will be quite wrong, and the loop arrows look also wrong indeed. You could draw a loop (circular or a rectangle with fillets) in the middle of your volumes.
But it looks like you have a deformed coil wit a non planar shape, not sure how to correctly define that. Probably you should send the request directly to "Support".
--
Good luck
Ivar
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Posted:
9 years ago
Hey Ivar,
thank you for your quick reply. Naturally I took a look at some other posts before I wrote down my request in this forum and I am very happy to have a contact person like you - what I want to say: you do a great job; thank you for that.
You are right. It is a deformed coil with a non-planar shape - a saddle coil. I solved the problem by using the multi-turn coil type "numeric" and added a work plane to cut my model for creating a cross section. It is required to select the input of the input subnode of the automatic current calculation subnode. An electric insulation subnode is also required in which I selected all boundary faces of that coil. Furthermore I added appropriate coil current calculation steps to my study.
[EDIT: I created a new request for the following question: "Measuring of induced voltages in externally excited coils"... ]
My next challenge consists of simulating a quasi-static problem of this model in frequency domain. I want some of my cylindrical coils generating an AC field (driven by an AC current) and measure the induced voltage in the saddle coils which are penetrated by the generated time-varying magnetic flux. Perhaps you could give me a hint how to do that, too? A stationary study step runs without any errors but simply adding a frequency domain study step seems not to be the solution of the problem since my simulation does not converge (the error in my convergence plot of the BiCGStab oscillates between 10^-3 and 3).
Thank you in advance again and have a nice day,
Sebastian
thank you for your quick reply. Naturally I took a look at some other posts before I wrote down my request in this forum and I am very happy to have a contact person like you - what I want to say: you do a great job; thank you for that.
You are right. It is a deformed coil with a non-planar shape - a saddle coil. I solved the problem by using the multi-turn coil type "numeric" and added a work plane to cut my model for creating a cross section. It is required to select the input of the input subnode of the automatic current calculation subnode. An electric insulation subnode is also required in which I selected all boundary faces of that coil. Furthermore I added appropriate coil current calculation steps to my study.
[EDIT: I created a new request for the following question: "Measuring of induced voltages in externally excited coils"... ]
My next challenge consists of simulating a quasi-static problem of this model in frequency domain. I want some of my cylindrical coils generating an AC field (driven by an AC current) and measure the induced voltage in the saddle coils which are penetrated by the generated time-varying magnetic flux. Perhaps you could give me a hint how to do that, too? A stationary study step runs without any errors but simply adding a frequency domain study step seems not to be the solution of the problem since my simulation does not converge (the error in my convergence plot of the BiCGStab oscillates between 10^-3 and 3).
Thank you in advance again and have a nice day,
Sebastian
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Posted:
9 years ago
Sebastain,
Kindly upgrade your COMSOL to 5.1 version, wherein you have the advantage to provide the coil current direction specifically which is presently not available in lower versions. (i guess you are doing a differential type of saddle coil).
Secondly, for frequency study analysis always try to solve your problem with FGMRES (Flexible Generalized minimal residual method) rather than BiCG (Biconjugate gradient method). FGMRES is more stable and unfortunately COMSOL has BiCG as the default solver for frequency domain analysis.
Do let me know if you find your way thru these tricks.
Regards,
Mahesh Raja
Kindly upgrade your COMSOL to 5.1 version, wherein you have the advantage to provide the coil current direction specifically which is presently not available in lower versions. (i guess you are doing a differential type of saddle coil).
Secondly, for frequency study analysis always try to solve your problem with FGMRES (Flexible Generalized minimal residual method) rather than BiCG (Biconjugate gradient method). FGMRES is more stable and unfortunately COMSOL has BiCG as the default solver for frequency domain analysis.
Do let me know if you find your way thru these tricks.
Regards,
Mahesh Raja