主题：关于FEMM 4.0

FEMM感觉挺好的,主要的还是免费!

 
The inductance of an air core solenoid coil can be calculated with Wheeler's formula:

L (microhenries) =	0.8 * N^2 * R^2          6*R + 9*L + 10*B
N = total number of turns R = average radius = (inner radius + outer radius)/2 L = coil length (along the axis) B = thickness of the winding = outer radius - inner radius Refer to Figure 1 below. (all dimensions in inches)
Alternatively, for dimensions in millimeters:
L (microhenries) =	0.0315 * N^2 * R^2         6*R + 9*L + 10*B

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Figure 1

For the analysis of magnetic fields, I highly recommend a finite element analysis program called "FEMM" (Finite Element Methods Magnetics). This very useful program was written by Dr. David Meeker and version 3.1 is available free at his web site. Be sure to get the tutorial by Ian Stokes-Rees. This tutorial has very detailed step-by-step examples using FEMM. If you have been using version 2, version 3 has some new features that you'll fine useful and the data files are formated to make them easier to read, in case you want to change a parameter with a text editor. The .fem files are plain text, so you can view and edit them with any text editor, such as Notepad. It also includes a very powerful scripting capability.

The project editor incorporated in FEMM is good, however, if you make changes to an existing project file, you may want to save it with a different name before running the analysis in case you decide to revert back to the original design. FEMM as the peculiarity of writing the source file to disk with the original file name before it does an analysis.

The FEMM message board is an excellent source of additional information about magnetic problems.

Here is another example using FEMM, with graphical and numerical results.