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boundary conditions of applying an alternative current
Posted Apr 30, 2012, 8:07 a.m. EDT Low-Frequency Electromagnetics Version 3.5a 3 Replies
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i need to simulate a method which uses AC signal in a relative low frequency of 128 Hz. I have run the simulation of the same device (test Wenner) with DC giving not bad results, but now i need to simulate with AC, as it really is, hoping that it will give similar results to that of DC (since it works in low frequencies). So, i changed my module and i went to AC/DC module, on order to use the module Electric currents of quasi statics, Electrics as you have proposed to me in an earlier question. The thing is that i create points that they have to inject on to a block an alternative current, i.e. sinusoidal. However, when i go to the point boundaries i do not get the option for currents but only potentials.
If instead of the points i create surfaces i go to the surface boundaries and i write an expression for the inward current flow : 0.01sin(8t) for exemple, will it comsol understand automatically the form of the signal or should i also change the solver parameter to time dependent and adjust the time stepping etc? (on the same window i am using the time harmonic currents and not the transient electric currents, is that right?)
Thank you in advance!!!
Marilena
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if you want to study a transient ot time dependent model, then you must use the time stepping Study and solvers. this will define the variable "t" in [s] and allows you to give any BC input (such as a current or heat source or ...) with a time dependent function.
now if you have a steady state sinus type excitaion, you should also consider the harmonic (frequency domain) Study & solvers, as these are often faster but will give you only the rms or average values (no transient cases). You define amplitude and if required phase, then a frequency or frequency span by the solver.
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Good luck
Ivar
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thank you for your response. I am using comsol 3.5a quasi electrostatics, electric currents. In the solver parameters tab, i select the time harmonic current analysis, however in the solver list there is no frequency domain study and so i cannot see how i could define the frequency.
Thank you in advance
Marilena
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sorry I hadnt noticed you were in 3.5, that one is getting too old, I have forgotten where the freq is hidden, and I do not have it up online anymore.
But there should be a few other 3.5 users out here to help
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Good luck
Ivar