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electric currents model

Posted 18.12.2012, 03:31 GMT-5 Low-Frequency Electromagnetics Version 4.3a 3 Replies

traxer
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Hallo,

i have a question about the electric currents model. My simulation is 2D axisymmetric in frequency domain.
The geometry is a solenoid which has two turns. As you know, if the current flows through solenoid, the currents in each turn are not the same because of the parasitic capacitance between them. Now, i want to find the current which flows through that capacitance between the two turns (i think that current is displacement current, but i am not sure ). By using "Terminal-terminal type Voltage", i can get a result. But i can't find the current which flows through each turn(ec.Jphi=0). What i want to get is the relationship: ec.Jphi + ec.Jdz = ec.I0_1 Obviously, i am worng :( How is the Terminal current ec.I0_1 calculated? what is reacf(V) function? why can i get a induced current (in electric currents model, i think the equation rot(E)= -dB/dt is not used)?

Best regards

Hua
3 Replies Last Post 20.12.2012, 13:40 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 20.12.2012, 02:09 GMT-5
Hi

Why not set one GND and one Terminal then COMSOL aromatically calculates the Admittance for you too. You can keep the voltage difference of 1 V between the coils

Then I would add a small air-gap in between the two coils, and ensure you have at least 3 elements in this region, not that it changes a lot but you avoid a formal current flow in the point contact region

Finally you could compare EC and ES, in ES you have no current flow so the results are perhaps easier to interprete

--
Good luck
Ivar
Hi Why not set one GND and one Terminal then COMSOL aromatically calculates the Admittance for you too. You can keep the voltage difference of 1 V between the coils Then I would add a small air-gap in between the two coils, and ensure you have at least 3 elements in this region, not that it changes a lot but you avoid a formal current flow in the point contact region Finally you could compare EC and ES, in ES you have no current flow so the results are perhaps easier to interprete -- Good luck Ivar
traxer
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Posted: 1 decade ago 20.12.2012, 03:32 GMT-5
Hi Ivar,

thanks a lot for your suggestion, but i am still a little confused. In es model, i can get the capacitance between each turn, but no current flow appears. In ec model, in fact, i can get the displacement current between each turns but not the current which flows through each turn (i can only give the potential in 2D)... Ist it possible to give the excitation current in ec model (2D axisymmetric) directly? for example external current density in phi direction (Jephi)?

best regards

Hi Ivar, thanks a lot for your suggestion, but i am still a little confused. In es model, i can get the capacitance between each turn, but no current flow appears. In ec model, in fact, i can get the displacement current between each turns but not the current which flows through each turn (i can only give the potential in 2D)... Ist it possible to give the excitation current in ec model (2D axisymmetric) directly? for example external current density in phi direction (Jephi)? best regards
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 20.12.2012, 13:40 GMT-5
Hi

for the current looping around certainly you should use a Jphi.

ES is static, no current flow by "design" the opposite for EC with current flow (dynamics)

Normally 2D-axi you define the current along Jphi and say its constant around the loop (2D-axi hypothesis valid for all "phi")

But you actually is studying the current flow between coil loops, not exactly the same thing.

Check the physics (doc) of the ACDC multi-turn coil BC and their references, there you might get some answers too

--
Good luck
Ivar
Hi for the current looping around certainly you should use a Jphi. ES is static, no current flow by "design" the opposite for EC with current flow (dynamics) Normally 2D-axi you define the current along Jphi and say its constant around the loop (2D-axi hypothesis valid for all "phi") But you actually is studying the current flow between coil loops, not exactly the same thing. Check the physics (doc) of the ACDC multi-turn coil BC and their references, there you might get some answers too -- Good luck Ivar

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