Question about Calculating capacitance using Elmer Solver

[ajay0705]

Hello everyone,
I have made the required geometry consisting of 2 metal having a cuboid like structure, inside a stack of multiple dielectric boxes. I have attached a test.geo (GMSH file) file to view the entire geometry and get a clear view of it.

1. I wanted to know, whether I can carry out even and odd mode analysis to calculate coupling capacitance between the metals and the capacitance value for metal to ground? Even mode analysis is giving equal and in-phase voltage to both the metals and removing the coupling capacitance between the metals and get the value for metal to ground capacitance. On the other hand Odd mode analysis is giving equal and 180 degree out of phase voltage to calculate coupling capacitance using the formula -

Co = C11 + 2 * C12
where, Co - value obtained from the solver
C11- capacitance value obtained from the even mode analysis
C12- the coupling capacitance

2. Also, I found out that there are two ways to define boundary conditions to calculate capacitance -
- By defining the metals and ground as capacitance bodies.
- By using potential to define the metals and ground.
I wanted to know, what all parameters do I have to add to the 'sif' file in order to carry out capacitance calculation using the 'potential' method.

Thank you,
Ajay

[raback]

Hi

1) I guess you can freely set the BCs such that you get you desired symmetry. Elmer does not have any automated way of setting "even" and "odd" modes.

2) You can of course set the potential by hand. This works nicely if you have just one body and your capacitance matrix has one value. If you have 5 bodies your capacitance matrix has 15 unique values. The automatic system is intended to make life easier in such cases.

-Peter

[ajay0705]

Hi Peter,

Thanks a lot for the answers.
1) Do you mean to say I can set same potential for both the metals, and that would remove coupling capacitance from the picture (i.e. Ccoupling = 0) and the out put capacitance matrix would only have Metal to Ground capacitance values?

2) Yes I agree that the automatic system would make it easier for a case where I have more than 1 Capacitance bodies. So when I use the Capacitance Body method, how does it decide the voltage levels for the metals?

-Ajay