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time varying current

Posted 8 nov 2014, 18:45 GMT-5 Low-Frequency Electromagnetics, Materials, Structural Mechanics Version 4.3, Version 4.4 3 Replies

Sven Görnhardt
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Hi,

im new in COMSOL and would like to know at first:

How can i simulate a time dependent electrical current. I guess, at first i have to choose the " Study Type - time dependent".

I would like to simulate a shortcircuit between two phases (two parallel mounted busbars) and by the way the lorence force caused by the shortcircuit over a defined period of time.

Has anybody an Idea which model from the model library could be useful - or maybe someone has a model that describes a similar problem?!

Thanks in advance

Sven
3 Replies Last Post 18 nov 2014, 18:25 GMT-5
Tomasz Krupicz
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Posted: 1 decade ago 18 nov 2014, 04:59 GMT-5
Dear Sven,

you are right, in order to perform time dependent simulation you need to choose the "Time Dependent" study first.
Generally you can type in your own functions or use the build-in operators like “sin()” to define transient input signal (more build-in operators you can find in the documentation to the Software). Following this you can define a function “sin(2*Pi*50*t[1/s])*2[V]” and set it as a value of the voltage potential in the physics of the simulation. Another example can be to define a step function “Step1” under the “Definitions” node and use it in the physics by typing in the expression “step1(t[1/s])*2[V]”.

Moreover you can also use the “Electrical Circuit” Interface and couple your model to an external circuit. The example model where this procedures is used, you can find on our website: www.comsol.de/model/transient-modeling-of-a-capacitor-in-a-circuit-12695

Another example showing the current flow through both parallel wires placed close to each other you can find in the Model Libraries and also under the following link:www.comsol.de/model/electromagnetic-forces-on-parallel-current-carrying-wires-131

Kind regards,
Tomasz Krupicz
Comsol Multiphysics GmbH
Dear Sven, you are right, in order to perform time dependent simulation you need to choose the "Time Dependent" study first. Generally you can type in your own functions or use the build-in operators like “sin()” to define transient input signal (more build-in operators you can find in the documentation to the Software). Following this you can define a function “sin(2*Pi*50*t[1/s])*2[V]” and set it as a value of the voltage potential in the physics of the simulation. Another example can be to define a step function “Step1” under the “Definitions” node and use it in the physics by typing in the expression “step1(t[1/s])*2[V]”. Moreover you can also use the “Electrical Circuit” Interface and couple your model to an external circuit. The example model where this procedures is used, you can find on our website: http://www.comsol.de/model/transient-modeling-of-a-capacitor-in-a-circuit-12695 Another example showing the current flow through both parallel wires placed close to each other you can find in the Model Libraries and also under the following link:http://www.comsol.de/model/electromagnetic-forces-on-parallel-current-carrying-wires-131 Kind regards, Tomasz Krupicz Comsol Multiphysics GmbH
Sven Görnhardt
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Posted: 1 decade ago 18 nov 2014, 18:23 GMT-5
Dear Mr. Krupicz,

i have read the whole AC/DC Module User`s Guide, did some tutorials - but im still trying to apply an alternating current like attached / as equation in that form in the MF-Interface (not MEF, because i need the time depended solver)?

sqrt(2)*Ipeak*exp(-(t[1/s]/(0.3)))*sin(versch)+sqrt(2)*Ipeak*sin(2*pi*FR*t-versch)

FR=50[Hz]
Ipeak=40[kA]
versch=2/3*pi



I attached a plot of the magnetic flux density at a specific time (18[ms]), 1d plot of the output diagram of the current, which i inputted and last but not least a normal result plot ( why ever its totally green)

Shall i use the electric circuits or better the electric currents interface to get this running at a geometric configuration handled in "parallel wires" from the model library ( the parallel wire model match my theme exactly ) but i would like to do this in 3D?
Dear Mr. Krupicz, i have read the whole AC/DC Module User`s Guide, did some tutorials - but im still trying to apply an alternating current like attached / as equation in that form in the MF-Interface (not MEF, because i need the time depended solver)? sqrt(2)*Ipeak*exp(-(t[1/s]/(0.3)))*sin(versch)+sqrt(2)*Ipeak*sin(2*pi*FR*t-versch) FR=50[Hz] Ipeak=40[kA] versch=2/3*pi I attached a plot of the magnetic flux density at a specific time (18[ms]), 1d plot of the output diagram of the current, which i inputted and last but not least a normal result plot ( why ever its totally green) Shall i use the electric circuits or better the electric currents interface to get this running at a geometric configuration handled in "parallel wires" from the model library ( the parallel wire model match my theme exactly ) but i would like to do this in 3D?
Sven Görnhardt
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Posted: 1 decade ago 18 nov 2014, 18:25 GMT-5
Sorry Mr. Krupicz,

i had forgot to thank you very much for your detailed answere :).

Thanks in Advance for every new reaction for my second post.

Greetings
S. Görnhardt
Sorry Mr. Krupicz, i had forgot to thank you very much for your detailed answere :). Thanks in Advance for every new reaction for my second post. Greetings S. Görnhardt

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