FEMM is a suite of programs for solving low frequency electromagnetic problems on two-dimensional planar and axisymmetric domains.
Overview
The goal of this section is to give the user a brief description of the problems that FEMM solves.
This information is not really crucial if you are not particularly interested in the approach that
FEMM takes to formulating the problems. You can skip most of Overview, but take a look at
Section 1.3. This section contains some important pointers about assigning enough boundary
conditions to get a solvable problem.
Relevant Partial Differential Equations
The preprocessor is used for drawing the problems geometry, defining materials, and defining
boundary conditions. A new instance of the preprocessor can be created by selecting File|New
off of the main menu and then selecting “Magnetics Problem” from the list of problem types which then appears.
Drawing a valid geometry usually consists of four (though not necessarily sequential) tasks:
• Drawing the endpoints of the lines and arc segments that make up a drawing.
• Connecting the endpoints with either line segments or arc segments
• Adding “Block Label” markers into each section of the model to define material properties
and mesh sizing for each section.
• Specifying boundary conditions on the outer edges of the geometry.
This section will describe exactly how one goes about performing these tasks
Preprocessor Drawing Modes
The key to using the preprocessor is that the preprocessor is always in one of five modes: the Point
mode, the Segment mode, Arc Segment mode, the Block mode, or the Group mode. The first four
of these modes correspond to the four types of entities that define the problems geometry: nodes
that define all corners in the solution geometry, line segments and arc segments that connect the
nodes to form boundaries and interfaces, and block labels that denote what material properties and
mesh size are associated with each solution region. When the preprocessor is in a one of the first
four drawing modes, editing operations take place only upon the selected type of entity. The fifth
mode, the group mode, is meant to glue different objects together into parts so that entire parts can
be manipulated more easily.
One can switch between drawing modes by clicking the appropriate button on the Drawing
Mode potion of the toolbar. This section of the toolbar is pictured in Figure 2.1. The buttons