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How to plot the rms value of the electric field?

Posted 7 déc. 2012, 12:59 UTC−5 Low-Frequency Electromagnetics, Results & Visualization, Studies & Solvers Version 4.3 3 Replies

Rafael Rocha
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I am performing simulations of a three-phase cable in the interface electrostatic (es), and have an interest in obtaining the electric field distribution in the cable, as the simulation is time dependent, the COMSOL informs me the value of the electric field for each instant of time which I set, so I can plot various surfaces of the electric field, one for each time step.
However, my interest is the rms value of the electric field, and not in the instantaneous value, it is possible to plot a surface with the values rms ​​of the electric field, ie the root mean square ​​of instantaneous values?
3 Replies Last Post 9 déc. 2012, 04:41 UTC−5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 8 déc. 2012, 03:53 UTC−5
Hi

if you do power transmission at a fixed frequency, its much better to use the frequency domain solver in the "omega" mode. Then you gve the signal amplitudes and the responses are the amplitude (and phases if applicable, note that if an amplitude becomes complex, you will only get the real part displayed, so you must explicitely access real() and imag() parts separately for the postprocesing.

Time series is good for "transient" effects, and to see how long these take to die out, but are too long to solve for constant sinus type excitations

--
Good luck
Ivar
Hi if you do power transmission at a fixed frequency, its much better to use the frequency domain solver in the "omega" mode. Then you gve the signal amplitudes and the responses are the amplitude (and phases if applicable, note that if an amplitude becomes complex, you will only get the real part displayed, so you must explicitely access real() and imag() parts separately for the postprocesing. Time series is good for "transient" effects, and to see how long these take to die out, but are too long to solve for constant sinus type excitations -- Good luck Ivar
Rafael Rocha
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Posted: 1 decade ago 8 déc. 2012, 13:59 UTC−5
I do not understand how to represent the expression of voltage V = Vmax * sin (omega * t + fi), in the frequency domain. Would using the Fourier Transform?
I do not understand how to represent the expression of voltage V = Vmax * sin (omega * t + fi), in the frequency domain. Would using the Fourier Transform?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 9 déc. 2012, 04:41 UTC−5
Hi

Check the equations, its already in a harmonic development, you define the amplitudes (and phase if complex or in phasor expression) on the BC's the solver assumes the "sin()" and you define only the frequency in the solver tab. YOu can also define a series of frequencies, for a frequency span, as for any parametric sweep. But if you work at 50 Hz you define jsut freq=50[Hz].
Check the doc and the examples in the model library

Results values are amplitudes, so you need to use the sqrt(2) correction, or if more complex phase dependence, extract real and imag parts and combinethem accordingly
--
Good luck
Ivar
Hi Check the equations, its already in a harmonic development, you define the amplitudes (and phase if complex or in phasor expression) on the BC's the solver assumes the "sin()" and you define only the frequency in the solver tab. YOu can also define a series of frequencies, for a frequency span, as for any parametric sweep. But if you work at 50 Hz you define jsut freq=50[Hz]. Check the doc and the examples in the model library Results values are amplitudes, so you need to use the sqrt(2) correction, or if more complex phase dependence, extract real and imag parts and combinethem accordingly -- Good luck Ivar

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