StaticCurrentDensity + ideal resistor

Numerical methods and mathematical models of Elmer
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lorenzog7
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StaticCurrentDensity + ideal resistor

Post by lorenzog7 »

Hello,

I want to simulate how the current is split between a copper trace and a current sensor in parallel.
StaticCurrentDensity does the job with understanding the current, voltage drop etc.
I know that the sensor has 100uOhm resistance. How can I include that resistance in my simulation?
Ideally i would like to have like an ideal resistor between two boundaries.
Thank you.
Lorenzo
lorenzog7
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Re: StaticCurrentDensity + ideal resistor

Post by lorenzog7 »

I just wanted to add that I have downloaded Elmer 2 days ago and I am playing around with it, so I might miss something obvious.
lorenzog7
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Re: StaticCurrentDensity + ideal resistor

Post by lorenzog7 »

In the past days I have tried somethings.
CircuitsAndDynamics allows one to describe an external circuit and connect it to the model: this is exactly what I want.
The issue is that CircuitsAndDynamics uses MagnetoDynamics, which I cannot manage to make it work in my case. I have been working on the boundary conditions in order to se a potential and a current density but I am not able to replicate the results from StaticCurrentDensity.
I have a complex shape and I cannot simply use the Body Force Current density, because the current is not going simply along one axis.

So my questions to anyone passing by is:
- Can I add a resistor to StaticCurrentDensity?
- How can I use MagnetoDynamics to get the same results as StaticCurrentDensity? That is, I am interested one Boundary Condition with a known current and one with a Voltage (0V)

If you don't know the ansers, could you point me to somewhere/someone to ask about it?
Thank you :)
raback
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Re: StaticCurrentDensity + ideal resistor

Post by raback »

Hi

I just added a few lines that might enable this:
https://github.com/ElmerCSC/elmerfem/co ... 102aeef186

As a background this builds on a library functionality that enables to set an unknown field and a boundary such that is nevertheless is constant. If the primary variable is "Potential" this would be a BC like:

Code: Select all

Potential Constant = Logical True
If you want to have the total flux (the sum of Neumann conditions) to be defined you could additionally say:

Code: Select all

Potential Constant Flux = Real 1.23
So for StatCurrentSolver this would enable to define the total current on the boundary.

Now the thing I implemented is an additional term such that there is a multiplier for the unknown potential,

Code: Select all

Potential Constant Multiplier = Real 4.56
When you look at the equations a little bit you come up with (?)

\sum i + 1/R * U = I_tot

So if you define the multiplier to be the inverse of the resistance in series maybe this could work.

I did not test this...

-Peter
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Re: StaticCurrentDensity + ideal resistor

Post by raback »

To add, MagnetoDynamics is probably an overkill. There is no way to omit the computation of magnetic vector potential and in your case is probably not att all relevant. The equations should work also then but I don't think it is a road worth following. The CircuitsAndDynamics have been written that module in mind because the primary application field of Elmer has electrical machines and transformers where magnetism is highly relevant.
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