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AC current densities
Posted 22.06.2012, 08:29 GMT-4 Low-Frequency Electromagnetics Version 4.2a 3 Replies
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Hello experts
I am simulating a pulsed magnet in a strip-line design using the AC/DC module. In the process I need to impose well defined alternating surface currents to copper plates.
The physics I load is "Magnetic fields (mf)".
I first tried the "Single-Turn Coil Domain", which indeed yield AC currents, but they differ significantly from plate to plate and rise as the frequency rises in a "Frequency Domain" study.
I also tried "External Current Density" Domains, which do yield the correct current densities after the simulation, but are not alternating (and so not useful).
What am I doing wrong?
Looking forward to your advice
Martin
I am simulating a pulsed magnet in a strip-line design using the AC/DC module. In the process I need to impose well defined alternating surface currents to copper plates.
The physics I load is "Magnetic fields (mf)".
I first tried the "Single-Turn Coil Domain", which indeed yield AC currents, but they differ significantly from plate to plate and rise as the frequency rises in a "Frequency Domain" study.
I also tried "External Current Density" Domains, which do yield the correct current densities after the simulation, but are not alternating (and so not useful).
What am I doing wrong?
Looking forward to your advice
Martin
3 Replies Last Post 22.06.2012, 10:05 GMT-4
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Posted:
1 decade ago
Hi
how are you defining your AC currents ? and which solver do you consider (frequency domain harmonic type I would expect)
Get your model running on a simple example 2D-axi air + 1 coil loop then change the coil type current density coil advanced models etc, until you master all models then go head with a more complex model
Do not be afraid to reread your doc 2-3 times and to do all ACDC exercises in the model library
--
Good luck
Ivar
how are you defining your AC currents ? and which solver do you consider (frequency domain harmonic type I would expect)
Get your model running on a simple example 2D-axi air + 1 coil loop then change the coil type current density coil advanced models etc, until you master all models then go head with a more complex model
Do not be afraid to reread your doc 2-3 times and to do all ACDC exercises in the model library
--
Good luck
Ivar
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Posted:
1 decade ago
Hello Ivar
Thank you for your quick response.
It is a 2D model and consists only of two copper plates, which are then copied and mirrored four times.
This is basically what I would like to get explained. I tried so by the two methods described in my first post.
(I also tried connecting the domains to an electric circuit, but that returned the same result as the "Single-Coil Domain".)
I already had a look at the Model Library. It lead me to trying the Coil domains. I guess that COMSOL superimposes the induced currents to the external ones, but I would like to fix the currents (as would be the case when operating the magnet.)
Please excuse my basic question. COMSOL is the first professional simulation program I am using and I am the only one at the institute doing so. But I need the results to understand measurements in my thesis.
Best regards
Martin
PS: I forgot to answer about the solver. It is the predefined Frequency Domain Study from the Magnetic Field module.
Thank you for your quick response.
It is a 2D model and consists only of two copper plates, which are then copied and mirrored four times.
how are you defining your AC currents ?
This is basically what I would like to get explained. I tried so by the two methods described in my first post.
(I also tried connecting the domains to an electric circuit, but that returned the same result as the "Single-Coil Domain".)
I already had a look at the Model Library. It lead me to trying the Coil domains. I guess that COMSOL superimposes the induced currents to the external ones, but I would like to fix the currents (as would be the case when operating the magnet.)
Please excuse my basic question. COMSOL is the first professional simulation program I am using and I am the only one at the institute doing so. But I need the results to understand measurements in my thesis.
Best regards
Martin
PS: I forgot to answer about the solver. It is the predefined Frequency Domain Study from the Magnetic Field module.
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Posted:
1 decade ago
Hi
the CIR is nice to use if you have a full circuit behind to have full impedances of the electronics that might influence your model.
But do not use CIR for simple sinus loading, its a waist of time and increased complexity.
You can as well use the lumped parameter entries in the main physics and imply either a time series with a
"sin(2*pi*freq[Hz][*t[1/s])"
type excitation good for transient analysis but not really steady state sinus or AC response. For AC response in steady state sinus excitation use a harmonic (frequency domain) approach, you give the voltage at the terminal (read the peak voltage) and you define the frequency in the frequency domain solver setting and COMSOL mixes both on a harmonic developed PDE equations (see the equation view of the physics nodes)
You might also add a phase then use a "phasor" expression on your terminal voltage
Note that some physics do not have the frequency domain harmonic development implemented, and if you select several physics you will have proposed only the solvers that are valid for all physics, but later you might add new solver cases for a specific physics
--
Good luck
Ivar
the CIR is nice to use if you have a full circuit behind to have full impedances of the electronics that might influence your model.
But do not use CIR for simple sinus loading, its a waist of time and increased complexity.
You can as well use the lumped parameter entries in the main physics and imply either a time series with a
"sin(2*pi*freq[Hz][*t[1/s])"
type excitation good for transient analysis but not really steady state sinus or AC response. For AC response in steady state sinus excitation use a harmonic (frequency domain) approach, you give the voltage at the terminal (read the peak voltage) and you define the frequency in the frequency domain solver setting and COMSOL mixes both on a harmonic developed PDE equations (see the equation view of the physics nodes)
You might also add a phase then use a "phasor" expression on your terminal voltage
Note that some physics do not have the frequency domain harmonic development implemented, and if you select several physics you will have proposed only the solvers that are valid for all physics, but later you might add new solver cases for a specific physics
--
Good luck
Ivar