Finite Element Method Magnetics

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2.3 <strong>Magnetics</strong> PostprocessorThe the magnetics postprocessing functionality of femm is used to view solutions generated by thefkern solver. A magnetics postprocessor window can be opened either by loading some previouslyrun analyses via File|Open on the main menu, or by pressing the “big magnifying glass” icon fromwithin a preprocessor window to view a newly generated solution. <strong>Magnetics</strong> postprocessor datafiles stored on disk have the .ans prefix.2.3.1 Postprocessor modesSimilar to the preprocessor, the postprocessor always operates in one of three modes, dependingupon the task to be performed. These modes are:• Point Values Mode In this mode, the user can click on various points in the solution region.Local field values are then listed in the FEMM Output window.• Contour Mode This mode allows the user to define arbitrary contours in the solution region.Once a contour is defined, plots of field quantities can be produced along the contour, andvarious line integrals can be evaluated along the contour.• Block Mode The Block Mode lets the user define a subdomain in the solution region. Oncethe block has been defined, a variety of area and volume integrals can be taken over thedefined subdomain. Integrals include stored energy (inductance), various kinds of losses,total current in the block, and so on.The current postprocessor mode is controlled via the Analysis Mode toolbar buttons, shownin Figure 2.16. The buttons denote, respectively, Point Values mode, Contour Mode, and BlockFigure 2.16: Analysis Mode toolbar buttonsMode. The depressed button denotes the current mode. The default mode when postprocessorstarts is Point Values mode.2.3.2 View and Grid ManipulationThe aspects of the current view and of the current grid are regulated via the use of toolbar buttons.The view is manipulated by the following toolbar buttons: and the grid settings are manipulated byFigure 2.17: View Manipulation toolbar buttons.these grid manipulation toolbar buttons: The grid and view manipulation work in exactly the samefashion as these same features in the preprocessor. Refer to Section 2.2.4 for a detailed descriptionof grid manipulation, and to Section 2.2.3 for view manipulation.32
2.3.3 Keyboard CommandsFigure 2.18: Grid Manipulation toolbar buttons.Unlike the preprocessor, postprocessor is not very dependent on keyboard commands.In the Point Values mode, there is only one relevant keypress. In this mode, the Tab key allowsthe user to enter the coordinates of a specific point. After the coordinates of a point are entered,the field values at that point are displayed in the FEMM Output window.In the Contours, there are four relevant keys. Pressing the Escape key wipes out any currentcontour or block definition. Pressing the Delete removes the last point added to the current contouror block edge. Pressing the Shift key allows the user to turn the last segment in the prescribedcontour from a straight line into an arc. A dialog pops up after the key is pressed that prompts forattributes of the the desired arc. Last, pressing the Tab keys allows the user to numerically enterthe coordinates of a point to be included in the current contour.In the Block mode, the Escape and Delete keys have the same definition as in Contours mode.In the Block mode, the Tab key does not do anything, since all points on the contour must also bePoints defining the model’s geometry.2.3.4 Mouse ActionsIn contrast, the operation of the postprocessor is very dependent upon input from the mouse.In the Point Values mode, a Left Button Click is used to display field values at the currentmouse location. If Snap to Grid is enabled, values are displayed at the closes grid point instead.In the Contours mode, mouse clicks are used to define the contour. A Left Button Click addsthe closest Point in the model’s geometry. Via a Right Button Click, the current mouse pointerlocation is added to the contour. A contour appears as a red line on the screen.Blocks are defined in Block mode in a fashion very similar to the way in which contours aredefined. A block is defined by by drawing a contour around the region of interest. The contourappears as a green line on the postprocessor screen. When the ends of the contour meet, the blockis defined. All elements enclosed by the contour (all elements that form the block) then turn greenin the postprocessor window.A Left Button Click attempts to add the nearest Point in the input geometry to the Block’s contour.However, a block can only be defined along line and arc segments from the input geometry.Each node on the boundary of the block must be selected in order to form the Block boundary. InBlock mode, the Right mouse button has no function.2.3.5 Contour PlotOne of the most useful ways to get a subjective feel for a magnetics finite element solution is byplotting the “flux lines.” These are the streamlines along which flux flows in the finite elementgeometry. Where flux lines are close together, the flux density is high. In FEMM’s vector potential33
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 18 and 19: 2.2.6 Problem DefinitionThe definit
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 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
Page 68 and 69: • mi setarcsegmentprop(maxsegdeg,
Page 70 and 71: 3.3.7 Zoom Commands• mi zoomnatur
Page 72 and 73: - For a “Strategic dual image”
Page 74: 3.3.10 Miscellaneous• mi savebitm
Page 78 and 79: 3.4.2 Selection Commands• mo sete
Page 80 and 81: - 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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