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problem of impendance for eddy current testing

Posted Nov 1, 2010, 9:48 p.m. EDT Low-Frequency Electromagnetics Version 4.3b 5 Replies

Noritaka Yusa
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Hi,

I am making a 2D axisymmetirc model for eddy current testing. There are three parts in my model. One is air, second is metal plane, last is multi-turn coil(number of turn is 140). How can I get the impendance(Z=R+wL in complex plane) of one coil? In the postproceeding, can I get the impendance of one coil directly by evaluate the coil inductance(mf.Lc_) and coil resistance(mf.Rcoil). I mean if the coil inductance(mf.Lc_) and coil resistance(mf.Rcoil) represent the impendance value in one coil. I also want to know what kind of equation is used for calculating the value.

Looking forward to the reply!

Thanks!
5 Replies Last Post Dec 30, 2013, 1:29 p.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Nov 2, 2010, 3:28 a.m. EDT
Hi

have you done the exercice around the power inductor example of the Model library, you should find most of the relies therein, no ?

--
Good luck
Ivar
Hi have you done the exercice around the power inductor example of the Model library, you should find most of the relies therein, no ? -- Good luck Ivar
Noritaka Yusa
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Posted: 1 decade ago Nov 4, 2010, 5:31 a.m. EDT
Hi,

Ivar, thank you for your information.

I have done the models. Now, I am making another simulation about eddy current testing. This is also a 2D axisymmetric model. Two multi-turn coils are used. One is used for exciting and another for detecting. They are both located at the inside of a tube. I got a error when I computed. The error is`division by zero`. I am confused about it.

Attached is my model and the error.

Looking forward the reply.

Best wishes.
Hi, Ivar, thank you for your information. I have done the models. Now, I am making another simulation about eddy current testing. This is also a 2D axisymmetric model. Two multi-turn coils are used. One is used for exciting and another for detecting. They are both located at the inside of a tube. I got a error when I computed. The error is`division by zero`. I am confused about it. Attached is my model and the error. Looking forward the reply. Best wishes.

Attachments:

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Nov 4, 2010, 9:17 a.m. EDT
Hi

not sure its linked but you have missed the "acoil" section value for coil "2", but as there is no current either it might not be it !?

now it generates a mass matrix = 0 error but it calculates partly, the mass error comes from a (probaby old leftover frequency solver seuqnce in your Study section)

In V4.0 and 4.0a you should carefully delete old solvers before making new ones, these early COMSOL versions are not fully capable of cleaning up "automatically.

So by correcting the coil section and adding a curent, and regenerating the solver it should work, but I canniot tell like thit if its "correct ;)

Always carefully validate and verify your models at least agains a simple analytical solution
--
Good luck
Ivar
Hi not sure its linked but you have missed the "acoil" section value for coil "2", but as there is no current either it might not be it !? now it generates a mass matrix = 0 error but it calculates partly, the mass error comes from a (probaby old leftover frequency solver seuqnce in your Study section) In V4.0 and 4.0a you should carefully delete old solvers before making new ones, these early COMSOL versions are not fully capable of cleaning up "automatically. So by correcting the coil section and adding a curent, and regenerating the solver it should work, but I canniot tell like thit if its "correct ;) Always carefully validate and verify your models at least agains a simple analytical solution -- Good luck Ivar
Noritaka Yusa
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Posted: 1 decade ago Nov 8, 2010, 12:22 a.m. EST
Hi,

Ivar, thank you for your advice. Now there is no error. I will more careful in the further simulations.

In this case, how can I get the induced voltage of the detecting coil. If I directly calculate by globle evaluation, I just can get the induced voltage of the exicting coil. How can I set a datas about the value of the detector?

Looking forward to your advice.

Best regards
Hi, Ivar, thank you for your advice. Now there is no error. I will more careful in the further simulations. In this case, how can I get the induced voltage of the detecting coil. If I directly calculate by globle evaluation, I just can get the induced voltage of the exicting coil. How can I set a datas about the value of the detector? Looking forward to your advice. Best regards
Mahesh MS by Research
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Posted: 1 decade ago Dec 30, 2013, 1:29 p.m. EST
Dear Yusa,
Hello,
Myself Mahesh doing my post graduation in Indian Institute of Technology, Madras. My research is on Eddy current NDE. I am trying to simulate a benchmark problem issued by WFNDE in 2010, i.e. Rectangular Slot in a thick plate. For this study i intend to use surface current boundary condition as excitation with J0 as a constant. The coil is moved over a notch at a frequency of 900 Hz and its resistance and reactance are calculated by integrating the resistive losses(Joule Heating) in the conducting domain and the magnetic energy in all the domain.
Variation of Resistance and reactance are plotted along the crack length.
Variation = (Resistance with notch - Resistance without notch).
But in my case the resistance is a constant as it is moved along the length.
I was going through some discussions in COMSOL support where i had a luck to oversee your discussions on Impedance. Also, I am hereby attaching the model for your reference.
Kindly let me know to solve the problem.
Thanks in advance.

Mahesh Raja P

Dear Yusa, Hello, Myself Mahesh doing my post graduation in Indian Institute of Technology, Madras. My research is on Eddy current NDE. I am trying to simulate a benchmark problem issued by WFNDE in 2010, i.e. Rectangular Slot in a thick plate. For this study i intend to use surface current boundary condition as excitation with J0 as a constant. The coil is moved over a notch at a frequency of 900 Hz and its resistance and reactance are calculated by integrating the resistive losses(Joule Heating) in the conducting domain and the magnetic energy in all the domain. Variation of Resistance and reactance are plotted along the crack length. Variation = (Resistance with notch - Resistance without notch). But in my case the resistance is a constant as it is moved along the length. I was going through some discussions in COMSOL support where i had a luck to oversee your discussions on Impedance. Also, I am hereby attaching the model for your reference. Kindly let me know to solve the problem. Thanks in advance. Mahesh Raja P

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