User:Brian P. Josey/Notebook/2010/03/08

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FEMM

I'm starting to run through the FEMM program, and learning how to use it. I found some nice tutorials for them on the company's website. I'm going to run through the tutorials, starting with the magnetostatics one today. Later, Koch is going to work with me on it.

Magnetostatic Tutorial

The purpose of this one is to create a magnetic coil surrounded by air. I went through the whole process of the tutorial, and it is not that hard to do everything, so far. Essentially the steps for a magnetic problem are:

  1. Draw Boundaries and structure
  2. Place Block Labels
  3. Add Materials to Library
  4. Create Properties
  5. Associate Properties to Blocks
  6. Create Boundary Conditions
  7. Generate Mesh, and Run FEA (Finite Element Analysis)
  8. Analyze and do whatever you want

As long as I follow these steps, and don't skip out on anything, it should be easy to do. Two tricks that I need to remember are: press TAB to dialog box for inputting coordinates, and SPACE for properties.

Electrostatics Tutorial

This tutorial was very similar to the one for magnetostatics, and the steps are the same, except for a few points. While you have to specify materials, and the currents running through them for magnetic problems, you only have to specify the potential of different parts. The end results are measurements of the electric field.

This tutorial came in two parts, the first was creating a capacitor with four sides, surrounded by another capacitor. There is a potential difference between the inside and outside capacitor of 1V. Because of the symmetry of the geometry, the problem is cut up, and only a fourth of it is analyzed. This creates a bent region that looks like a chevron on a crest. The second project is to create a model of a capacitor made of two spheres set apart from each other with identical properties, but opposite voltages. The neat part about this one is that the problem is cut up into fourths again. One line bisects the spheres through their centers, and another separates the spheres from each other. While I know I am just touching the beginnings of what FEMM can do, I think the way they set up the problems is really unique and surprising, and I am paying close attention to them.

This above is an image from the second electrostatics tutorial that I did. In the problem, there are two identical spherical conductors that each have a radius of 25m. They are held away from each other so that there centers are 70m apart, and the surfaces are 20m apart. One sphere has a potential of +100V while the other has a potential of -100V. This is the potential density around one of the spheres, where reds and purples represent higher potentials, and blues represent lower potentials. They run from 0V to 100V.

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