1 Introduction - Finite Element Method Magnetics

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Figure 5: Grid Properties dialog. The Grid Properties dialog has an edit box for the user to enter the desired grid sizing. When the box appears, the number in this edit box is the current grid size. The edit box also contains a drop list that allows the user to select between Cartesian and Polar coordinates. If Cartesian is selected, points are specified by their (x,y) coordinates for a planar problem, or by their (r,z) coordinates for an axisymmetric problem. If Polar is selected, points are specified by an angle and a radial distance from the origin. The default is Cartesian coordinates. 3.5 Edit Several useful tasks can be performed via the Edit menu off of the main menu. Perhaps the most frequently used is the Undo command. Choosing this selection undoes the last addition or deletion that the user has made to the model’s geometry. For selecting many objects quickly, the Select Group command is useful. This command allows the user to select objects of the current type located in an arbitrary rectangular box. When this command is selected, move the mouse pointer to one corner of the region that is to be selected. Press and hold the left mouse button. Then, drag the mouse pointer to the opposite diagonal corner of the region. A red box will appear, outlining the region to be selected. When the desired region has been specified, release the left mouse button. All objects of the current type completely contained within the box will become selected. Any objects that are currently selected can be moved, copied, or pasted. To move or copy selected objects, simply choose the corresponding selection off of the main menu’s Edit menu. A dialog will appear prompting for an amount of displacement or rotation. 3.6 Problem Definition The definition of problem type is specified by choosing the Problem selection off of the main menu. Selecting this option brings up the Problem Definition dialog, shown in Figure 6 The first selection is the Problem Type drop list. This drop box allows the user to choose from a 2-D planar problem (the Planar selection), or an axisymmetric problem (the Axisymmetric selection). Next is the Length Units drop list. This box identifies what unit is associated with the dimensions prescribed in the model’s geometry. Currently, the program supports inches, millimeters, centimeters, meters, mils, and µmeters. 14
Figure 6: Problem Definition dialog. The first edit box in the dialog is Frequency (Hz). For a magnetostatic problem, the user should choose a frequency of zero. If the frequency is non-zero, the program will perform a harmonic analysis, in which all field quantities are oscillating at this prescribed frequency. The default frequency is zero. The second edit box is the Depth specification. If a Planar problem is selected, this edit box becomes enabled. This value is the length of the geometry in the “into the page” direction. This value is used for scaling integral results in the post processor (e.g. force, inductance, etc.) to the appropriate length. The units of the Depth selection are the same as the selected length units. For files imported from version 3.2, the Depth is chosen so that the depth equals 1 meter, since in version 3.2, all results from planar problems ar e reported per meter. The third edit box is the Solver Precision edit box. The number in this edit box specifies the stopping criteria for the linear solver. The linear algebra problem could be represented by: Mx = b where M is a square matrix, b is a vector, and x is a vector of unknowns to be determined. The solver precision value determines the maximum allowable value for ||b − Mx||/||b||. The default value is 10 −8 . Lastly, there is an optional Comment edit box. The user can enter in a few lines of text that give a brief description of the problem that is being solved. This is useful if the user is running several small variations on a given geometry. The comment can then be used to identify the relevant features for a particular geometry. 15
Page 1 and 2: Finite Element Method Magnetics Ver
Page 3 and 4: Contents 1 Introduction 5 2 Overvie
Page 5 and 6: 1 Introduction FEMM is a suite of p
Page 7 and 8: For a linear isotropic material (an
Page 9 and 10: Figure 1: Triangulation of Massachu
Page 11 and 12: Point Mode Keys Key Function Space
Page 13: • The “page with magnifying gla
Page 17 and 18: 3.7.1 Point Properties If a new poi
Page 19 and 20: where the n denotes the direction o
Page 21 and 22: Figure 10: Block Property dialog. s
Page 23 and 24: Figure 12: Sample B-H curve plot. i
Page 25 and 26: Properties | Materials Library sele
Page 27 and 28: interest and contains all of the it
Page 29 and 30: might take up to a minute or two to
Page 31 and 32: 5.3 Keyboard Commands Figure 19: Gr
Page 33 and 34: Figure 21: Solution for an air-core
Page 35 and 36: Figure 24: When in doubt plots and
Page 37 and 38: • Magnetic field energy This sele
Page 39 and 40: 5.11.2 Weighted Stress Tensor Volum
Page 41 and 42: Figure 26: Example three-phase, six
Page 43 and 44: Figure 29: Circuit results dialog.
Page 45 and 46: 6 Lua Scripting Documentation 6.1 W
Page 47 and 48: 6.2.2 Geometry Selection Commands
Page 49 and 50: • openfemmfile("filename") opens
Page 51 and 52: 6.2.10 Object Properties • addmat
Page 53 and 54: propnum Symbol Description 0 BlockN
Page 55 and 56: get point values getpointvalues exi
Page 57 and 58: • getpointvalues(X,Y) Get the val
Page 59 and 60: 6.3.2 Selection Commands • setedi
Page 61 and 62: 6.3.5 Miscellaneous • savebitmap(
Page 63 and 64: y Freund allow one to operate direc
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References [1] M. Plonus, Applied e
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A Appendix Figure 30: Sample demagn
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Figure 33: Recoil in partially dema
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and another reluctance for flux tha
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A.3.1 Truncation of Outer Boundarie
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Figure 36: Air-cored coil with “o
Page 77 and 78:
Figure 37: Example input geometry.
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the Steinmetz |B| 1.6 form for the
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