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Power developed by eddy currents
Posted 18 feb 2012, 00:51 GMT-5 Low-Frequency Electromagnetics 2 Replies
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Hi
I'm using the module AC / DC to perform the calculation of the power developed in [W] by eddy currents in a ferromagnetic cylinder. The spatial dimension is used to axial symetry (2D) and the boundary of the integration variable with Qsav_emqa compute surface integral. But the results are below the values of the analytical calculation.
Please someone help me.
Thank you.
I'm using the module AC / DC to perform the calculation of the power developed in [W] by eddy currents in a ferromagnetic cylinder. The spatial dimension is used to axial symetry (2D) and the boundary of the integration variable with Qsav_emqa compute surface integral. But the results are below the values of the analytical calculation.
Please someone help me.
Thank you.
2 Replies Last Post 18 feb 2012, 10:21 GMT-5
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Posted:
1 decade ago
Hi
have you checked the surface to volume integration tick, ? and/or do you use correctly the 2*pi*r multiplier in 2D-axi when required ? This is easily forgotten and produces hence wrong results. Normally you can track that by carefully checking the units COMSOL proposes.
If you are respecting correctly the point above, my suggestion is to study the mesh density behaviour of your results, AND check if you have any singularities, typically apearing at sharp corners. Then filleting of the geometry and or some numerical exclusions of these areas do help. Also using higher order shape unctions if you integrate higher order derivatives of the dependent variables
--
Good luck
Ivar
have you checked the surface to volume integration tick, ? and/or do you use correctly the 2*pi*r multiplier in 2D-axi when required ? This is easily forgotten and produces hence wrong results. Normally you can track that by carefully checking the units COMSOL proposes.
If you are respecting correctly the point above, my suggestion is to study the mesh density behaviour of your results, AND check if you have any singularities, typically apearing at sharp corners. Then filleting of the geometry and or some numerical exclusions of these areas do help. Also using higher order shape unctions if you integrate higher order derivatives of the dependent variables
--
Good luck
Ivar
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Posted:
1 decade ago
Ivar, thanks for the help.
The model I use is very simple. It consists of a cylinder with some turns around. The meshes were used in the convergence results. It seems that the mesh is OK. In the analytical model I'm using the equation Req = rho.pi.a.KR2.KS2.N^2/d.w Where "a" is outer diameter of the core, KR2 is the resistance factor that is related to the depth of penetration, KS2 is the size factor that is related to the physical dimensions of the coupling between the coil and core and "d.w" is the cross section seen by the eddy current. Factors KR2 and KS2 are from charts. The power developed in the cylinder is P = Req^2. I. I'm considering a model without losses in the winding. In the numerical model used analize "transient" and solver "time dependent". The physical dimensions and parameters are identical in both models. In the postprocessing used "Subdomain Integration". I chose the subdomain of the cylinder. Expression to integrate: "Qav_emqa." The full volume was selected because the mode is axisymmetric. But the value presented by COMSOL is different. To calculate the power developed in the cylinder should I use another expression to integrate? What else should I check?
Thank you.
The model I use is very simple. It consists of a cylinder with some turns around. The meshes were used in the convergence results. It seems that the mesh is OK. In the analytical model I'm using the equation Req = rho.pi.a.KR2.KS2.N^2/d.w Where "a" is outer diameter of the core, KR2 is the resistance factor that is related to the depth of penetration, KS2 is the size factor that is related to the physical dimensions of the coupling between the coil and core and "d.w" is the cross section seen by the eddy current. Factors KR2 and KS2 are from charts. The power developed in the cylinder is P = Req^2. I. I'm considering a model without losses in the winding. In the numerical model used analize "transient" and solver "time dependent". The physical dimensions and parameters are identical in both models. In the postprocessing used "Subdomain Integration". I chose the subdomain of the cylinder. Expression to integrate: "Qav_emqa." The full volume was selected because the mode is axisymmetric. But the value presented by COMSOL is different. To calculate the power developed in the cylinder should I use another expression to integrate? What else should I check?
Thank you.