Learning Forum

[bamdadslr]

Hi all, 

I am modeling a copper electrode inside the soil (Conductivity = 0.01 S/m) using ansys Maxwell. I want to apply a current to the electrode and find its resistance, but it seems that Maxwell can't close the conduction path through the soil. Is there anyway to model the current which goes through the soil?

[mgardner]

Maxwell has thresholds that determine whether an object is considered a perfect conductor, a perfect insulator, or an imperfect conductor.  Anything with a conductivity below the Insulator/Conductor threshold will be assumed to have no currents.  I believe the default conductivity threshold below which everything is considered to be a perfect insulator is 1 S/m.  You can change this by clicking on Maxwell 3D (or 2D) from the top menu options then selecting Design Settings.  Then, click the Material Thresholds tab and lower the threshold for Insulator/Conductor.

[bamdadslr]

Thank you so much for your help. I have one more question. What is the "The default number of maximum CG iterations at back substitution is too low for this project. The most likely reason is that the system matrix is badly conditioned" error?

[mgardner]

I am not familiar with that specific error.  However, I would guess that it is a result of having objects with really high and really low conductivities in the same model.  For example, if you are trying to compute the node voltages in a circuit using a matrix approach, and you have both really large resistances and really small resistances, the system matrix will have both really large values and really small values, which makes it difficult for a computer to invert accurately. 

You might try reducing the conductivity of the copper in your model by an order of magnitude or two since the voltage drop in the copper will still likely be negligible relative to the voltage drop through the soil.

[bamdadslr]

I really appreciate your help, thank you so much.