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External U vs. I
Posted 19.03.2013, 06:10 GMT-4 Low-Frequency Electromagnetics Version 4.3a, Version 5.2a 5 Replies
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I'm quite new to COMSOL. I generally have doubts where to use external U vs. I or external I vs. U when I want to insert my designed model into a circuit. I think in any of those cases I have to choose the excitation method accordingly, right? Is there a guideline for that?
What exactly is the difference? I tried to compute the model "inductor-in-circuit" in the model library once using the external U vs. I and the other time using external I vs. U. the computation of the model with external U vs. I takes a lot longer but converges and eventually finishes, however the resulting plots for the magnetic flux density norm are very different. So I don't understand how these choices affect the physical reality of the problem and why are the results different?
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check carefully the doc about U vs I and I vs U. Normally COMSOL will only allow you to connect a CIR "connector" if there is an appropriate Terminal or current source in the other physics
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Good luck
Ivar
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Could you please let me know what exactly this document on U vs I and I vs U is?
Thanks,
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I used only the "active help" to find quite some explanations, try a search on "U vs I"
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Good luck
Ivar
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the difference is:
U vs. I is typically measures a current in your PDE model and assigns a source of a prescribed voltage there.
I vs. U is typically measures a voltage in your PDE model and assigns a source of a prescribed current there.
For instance a lumped port in the magnetic fields interface can only be excited with a current, because
voltage is not a variable that is solved for nor contained in the model. Hence you would need to define an I vs. U because you need to assign a current. In many other interfaces, e.g. electrical currents, where you could assign both a driving voltage or a current on a "normal boundary condition", you can use either U vs. I or I vs. U.
Sven
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When it says arbitrary voltage value put in the External I vs U block. and then I try to excite my device model using a pulsed Voltage source from cir.. What is the impact of the value of voltage given in External I vs U block.
Why is that the model is not getting excited when I used pulsed voltage source values .
< PS : I am using frequency domain study>