Finite Element Method Magnetics

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2.2.6 Problem DefinitionThe definition of problem type is specified by choosing the Problem selection off of the mainmenu. Selecting this option brings up the Problem Definition dialog, shown in Figure 2.5Figure 2.5: Problem Definition dialog.The first selection is the Problem Type drop list. This drop box allows the user to choose froma 2-D planar problem (the Planar selection), or an axisymmetric problem (the Axisymmetricselection).Next is the Length Units drop list. This box identifies what unit is associated with the dimensionsprescribed in the model’s geometry. Currently, the program supports inches, millimeters,centimeters, meters, mils, and µmeters.The first edit box in the dialog is Frequency (Hz). For a magnetostatic problem, the usershould choose a frequency of zero. If the frequency is non-zero, the program will perform aharmonic analysis, in which all field quantities are oscillating at this prescribed frequency. Thedefault frequency is zero.The second edit box is the Depth specification. If a Planar problem is selected, this edit boxbecomes enabled. This value is the length of the geometry in the “into the page” direction. Thisvalue is used for scaling integral results in the post processor (e.g. force, inductance, etc.) to theappropriate length. The units of the Depth selection are the same as the selected length units. Forfiles imported from version 3.2, the Depth is chosen so that the depth equals 1 meter, since inversion 3.2, all results from planar problems ar e reported per meter.18
The third edit box is the Solver Precision edit box. The number in this edit box specifiesthe stopping criteria for the linear solver. The linear algebra problem could be represented by:Mx = bwhere M is a square matrix, b is a vector, and x is a vector of unknowns to be determined. Thesolver precision value determines the maximum allowable value for ||b − Mx||/||b||. The defaultvalue is 10 −8 .The fourth edit box is labeled Min Angle. The entry in this box is used as a constraint inthe Triangle meshing program. Triangle adds points to the mesh to nsure that no angles smallerthan the specified angle occur. If the minimum angle is 20.7 degrees or smaller, the triangulationalgorithm is theoretically guaranteed to terminate (assuming infinite precision arithmetic – Trianglemay fail to terminate if you run out of precision). In practice, the algorithm often succeeds forminimum angles up to 33.8 degrees. For highly refined meshes, however, it may be necessaryto reduce the minimum angle to well below 20 to avoid problems associated with insufficientfloating-point precision. The edit box will accept values between 1 and 33.8 degrees.Lastly, there is an optional Comment edit box. The user can enter in a few lines of text that givea brief description of the problem that is being solved. This is useful if the user is running severalsmall variations on a given geometry. The comment can then be used to identify the relevantfeatures for a particular geometry.2.2.7 Definition of PropertiesTo make a solvable problem definition, the user must identify boundary conditions, block materialsproperties, and so on. The different types of properties defined for a given problem are defined viathe Properties selection off of the main menu.When the Properties selection is chosen, a drop menu appears that has selections for Materials,Boundary, Point, and Circuits. When any one of these selections is chosen, the dialogpictured in Figure 2.6 appears. This dialog is the manager for a particular type of properties. AllFigure 2.6: Property Definition dialog boxcurrently defined properties are displayed in the Property Name drop list at the top of the dialog.At the beginning of a new model definition, the box will be blank, since no properties have yet19
Page 6: Chapter 1IntroductionFEMM is a suit
Page 9 and 10: where J src represents the applied
Page 11: 1.4 Finite Element AnalysisFigure 1
Page 14 and 15: 2.2.2 Keyboard and Mouse CommandsAl
Page 16 and 17: ActionLeft Button ClickRight Button
Page 20 and 21: een defined. Pushing the Add Proper
Page 22 and 23: Figure 2.8: Boundary Property dialo
Page 24 and 25: Figure 2.9: Block Property dialog.r
Page 26 and 27: Figure 2.11: Sample B-H curve plot.
Page 28 and 29: Associated with the lamination thic
Page 30 and 31: Figure 2.14: Circuit Property dialo
Page 32 and 33: 2.3 Magnetics PostprocessorThe the
Page 34 and 35: Figure 2.19: Graph Mode toolbar but
Page 36 and 37: In all of these plots, the directio
Page 38 and 39: • A This integral, the evaluation
Page 40 and 41: To compute the force on a region or
Page 42 and 43: Figure 2.23: Properly defined conto
Page 44 and 45: • ToolBar Use this toggle to hide
Page 46 and 47: Point Mode KeysKey FunctionSpace Ed
Page 48 and 49: point, is the “snap to grid” bu
Page 50 and 51: Lastly, there is an optional Commen
Page 52 and 53: Figure 2.32: Boundary Property dial
Page 54 and 55: Figure 2.34: Materials Library dial
Page 56 and 57: 2.5.1 Postprocessor modesSimilar to
Page 58 and 59: 2.5.6 Density PlotDensity plots are
Page 60 and 61: In certain cases, the quantity to b
Page 62 and 63: Weighted Stress Tensor Volume Integ
Page 64 and 65: Probably the easiest way to get gra
Page 66 and 67: • pause() Waits for the ok button
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• mi setarcsegmentprop(maxsegdeg,
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3.3.7 Zoom Commands• mi zoomnatur
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- For a “Strategic dual image”
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3.3.10 Miscellaneous• mi savebitm
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3.4.2 Selection Commands• mo sete
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- upper_A Upper limit for A contour
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• ei setblockprop("blockname", au
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• ei movetranslate(dx,dy,(editact
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• ei deleteconductor("conductorna
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3.6.1 Data Extraction Commands• e
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• eo addcontour(x,y) Adds a conto
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3.6.5 Miscellaneous• eo close() c
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nection and manually transferring i
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Chapter 6Numerical MethodsFor those
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its Gauss Point). One desires a con
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[15] Q. Chen and A. Konrad, “A re
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Figure A.2: Magnet as an equivalent
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magnets are being handled prior to
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Figure A.6: Equivalent circuit for
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One could think of this solution as
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A quick note on computational effic
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Figure A.8: Example input geometry.
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Finite Element Method Magnetics

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