Transcript Please click here to general content of the workshops.

Course Outline
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Program Layout
Program Setup
Viewing
Geometry Modeling
Physical Aspects
Problem Discretization
Analysis
Output
Program Layout
Important Features
• Workspace:
Model is
displayed
• Message Area:
Program tells
user what it
wants
• User Input Area:
User gives
program data.
Program Setup
Units Setup
View Setup
Units Setup
• Unit Systems
• Individual settings
• User Units
View Setup
•Limits define
maximum extents
of the model
•Rotation Step
defines how finely
view rotation is
applied
•Grid and Snap
used in 2D
modeling mode
Viewing
Zooming
Panning
Rotating
Standard Views
Rendering Modes
Visibility
Zooming
• Zoom-In and Zoom-Out – Allow you to zoom
in and out on different features
• Previous - To go back to the previous view
• Scale view to limits – takes to to default
view
Panning
• Using the Scroll bars is easiest
• Pan command allows you to pan the
view within the Workspace
Rotating View Position
Change Look-at Point
• Select the rotate view icon
or use the
keyboard arrow keys while in a selection loop
• Change the “Look-at Point” to rotate about a
local feature
• Use the Rotate Step setting on the View
Setup to allow finer/slower or coarser/faster
rotation
Standard Views
Standard View buttons
• Use standard views to quickly view from top
or sides.
• Use isometric view to get back to the
default 3D view position
Rendering Modes
Rendering Mode buttons
• Change rendering modes to establish
perspective.
• Use Coarse shading density
except to generate images
for presentations.
Rendering Modes
Wire-frame Rendering
Solid Model Rendering
Hidden Line Removal
Translucent Rendering
Visibility
Visibility buttons
• Use visibility to reduce the amount of visual
data your brain needs to process.
• HINT: Create GROUPs of geometry to more
quickly and flexibly show and hide items
related to the same parts of the model.
Geometry Modeling
Fundamentals
Segments
Selection
Definition - Surfaces, Volumes, Groups
Extrusion
Importing Geometry – DXF, IGES, IES2D
Modification
Geometry Fundamentals
• Basic building block
is a segment
• Closed, simplyconnected groups of
segments form
surfaces
• Closed groups of
surfaces form
volumes
Geometry Primitive Segments
Segment creation buttons
• Segments can be lines, arcs, or splines.
• Real geometry is modeled, not piecewise
linear approximation.
Useful Keyboard Shortcuts
• Algebraic expressions
(e.g. X+A Y-B Z/C)
Useful when entering geometry points for
primitives or when extruding linear
• Increment values using function keys
F5-F10
Useful for defining the axis for rotation or
circular sweeps.
Geometry Primitive Volumes
Volume primitive buttons
• Cubes, Cylinders, Spheres can be
constructed with separate commands
• Surface and volume definitions are
created in addition to the segments
• Can also use these as a starting point for
other volumes.
Geometry - Selection
Selection Type
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Change selection to desired type.
Entity that mouse is over is highlighted in orange.
Click to select highlighted entity.
If desired entity is obscured use <Ctrl> + Click to
toggle between alternatives, then click when desired
entity is green.
• HINT: Use Solid Rendering Mode while selecting
surfaces and volumes to confirm selections.
Surfaces, Volumes and Groups
• Surfaces required for placement of surface
types of physical attributes (boundary
conditions) and as the basic unit of a volume.
• Volumes required for placement of surface
types of physical attributes (materials, volume
currents, permanent magnets)
• Groups are useful for selection of
combinations of volumes that make up a part
or which have some functional similarity.
Surface Definition
• Surfaces must be made of three or four sides.
Surface Definition
• Surfaces can be made of more than 4 segments by
grouping multiple segments into one side.
• Note the distinction between “segment” and “side”.
These four segments comprise one side
Surface Definition
• Segments grouped into sides should meet such that
their tangents are “nearly continuous” at the
connection point.
• Rule of thumb – interior angle greater than 135o but
not greater than 225.
Bottom side is OK
Bottom side is NOT OK
Solution:
Create two surfaces
Surface Definition
• Two sides should not meet with an interior angle of
180o or greater (for four-sided surfaces).
Bad four-sided surfaces
Surface is OK, group
bottom two segments into
one side
Solution: Create two
three-sided surfaces
Surface Definition
• Surfaces with severe aspect ratios (i.e. one segment
much shorter than the rest) should be avoided.
• Rule of thumb – Opposite sides should have length
ratios > 1/20
Bad aspect ratio
Solution 1:
Break down into
smaller surfaces
with better
aspect ratios
Solution 2:
Remove small
feature and turn
into three-sided
surface
Volume Definition
• Volume constructed from a closed set of surfaces
• Volumes can be made up of any number of surfaces,
to place volume currents, face oriented magnets, or
sub-volumes, must have 6 surfaces.
Group Definition
• Groups can be made up of segments, surfaces and
volumes.
• Use groups to make selection and visibility of
structures of the same part easier.
Geometry – Extrusion
Geometry extrusion buttons
Sweep path setting
• Use extrusion or “sweeps” to generate surfaces from
segments and volumes from surfaces.
• Use Linear sweep setting to give thickness to
surfaces.
• Use Circular sweep setting to create surfaces or
revolution.
• Use Path sweep setting to generate arbitrary shapes.
Geometry - Imports
• IGES and DXF
• Best to start with 2D drawing and
extrude into third dimension
Geometry - Modification
Displace
Rotate
Pull
Undo (one level)
Delete/Delete All
Mirror
Scale
Geometry Operation:
Copy Off
Copy On
Stretch
Repeat On/Off
Geometry - Modification
• Displace – shift geometry by some
vector distance
• Rotate – shift geometry around a user
defined axis by some angle
• Mirror – Reflect geometry across user
defined plane
• HINT: Use Copy On setting with Repeat
button set to create multiple copies.
Geometry - Reshaping
• Pull – used to change the position of
individual points
Geometry - Reshaping
• Stretch setting – used to maintain
connections while shifting geometry
Result of displacing top surface with Stretch setting
Geometry - Reshaping
• Stretch setting – can also be used to
maintain connections while scaling
Result of scaling top surface with Stretch setting
Geometry Construction Tools
• Finding tangent lines.
Tangent to two arcs
Tangent to an arc
from a point
Tangent to an arc at a
point along the arc
Geometry Construction Tools
• Rounding corner where two lines meet.
Rounding two lines of length 1 unit with radius 0.1 unit
Geometry Construction Tools
• Finding curves of intersection of
surfaces.
Want to find union of two volumes
First find curves of intersection
using Intersection of Volumes
command
Geometry Construction Tools
Break and reconnect surfaces
Reconstruct as one volume or
three separate volumes
Physical Aspects
Material Properties
• BH curves
Electrostatics
• Boundary Conditions
• Volume and Surface Charges
Magnetics
• Volume and Surface Currents
• Permanent Magnets
Material Properties
Material properties include
permittivity, conductivity
and permeability.
Permeability can be linear
(single number) or
nonlinear (BH curve) data.
Change material properties
in Material Table.
BH Curves
Edited using the
Autograph utility.
Note the curve
fitting, slope at
the end is 1.0
(saturation)
Right click on
curve data to edit.
Volume and Surface Currents
• Volume currents are the most common.
• If a physical coil has an extreme height:width
ratio, approximate the coil by a surface current.
Rule of thumb: h/w > 20 use surface current.
Aspect
ratios
OK for
volume
h/w > 20
convert
volume to
surface
Volume and Surface Currents
• Currents are applied by assigning the nI
value to the appropriate geometry.
• Must also select the surface where
current enters the volume.
Current enters
volume through
this surface
Permanent Magnets
• First must generate a second quadrant
BH curve (demagnetizing curve)
Permanent Magnets
• Direction is determined by assigning:
Unit vector for magnetization direction
or
Magnetization normal to a geometry
surface
Problem Discretization
BEM Fundamentals
Symmetry and Periodicity
Placement of Elements and Subvolumes
BEM Fundamentals
Consider the electric field from a point charge and the magnetic
field from a filamentary current.
Magnetic field lines
Electric field lines
Positive charge
Current “out of page”
BEM Fundamentals
Placing several charges, both positive and negative, around a
boundary will give a field pattern somewhat as follows:
+
+
+
-
+++++++++++++++ +
- - - - - - - - - - - - - - - - -
+
+
-
BEM Fundamentals
Similarly, placing several filamentary currents around a
boundary will result in a field pattern as below:
+
+
+
-
+ + + + + + + + + + + + + + ++
- - - - - - - - - - - - - - - - -
+
+
-
BEM Fundamentals
• Equivalence principle: Material interfaces can be
replaced by certain equivalent sources that will
sustain the same fields. The sources are computed
to satisfy fundamental boundary conditions:
n X (H1-H2)=Js
n . (B1-B2)=0
n X (E1-E2)=0
n . (D1-D2)=qs
n X (H1-H2)=Js
n . (B1-B2)=0
• Boundary elements are placed to geometrically
represent where equivalent sources are placed.
BEM Fundamentals
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i
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i
Volume Sources
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Equivalent Surface Sources
Volume Sources
BEM Fundamentals
Boundary Elements needed on surfaces where:
Electro-statics:
Permittivity Mode
• Permittivity changes
• Voltage, dV/dn, or Floating boundary condition is assigned
Conductivity Mode
• Conductivity changes
• Voltage or Current boundary condition is assigned
Permitivitty and Conductivity (Both) Mode
• Any of the above
BEM Fundamentals
Boundary Elements needed on surfaces where:
Magnetostatics:
• Permeability changes
• Surface current is assigned
• Direction of magnetization of permanent magnets change.
Time Harmonic Magnetics:
• Permeability Changes
• Conductivity Changes
• Permittivity Changes (when displacement currents are
considered)
• Surface Currents are defined
BEM Solution
• Boundary elements solved for at the nodes
• Linear basis function used between nodes as shown
in the 2D example below.
Boundary Element Approximation Example
0.3
0.25
Qua dra tic Function
Y-Axis
0.2
1 Ele me nt R e pre se nta tion
0.15
2 Ele me nt R e pre se nta tion
0.1
4 Ele me nt R e pre se nta tion
0.05
0
0
0.2
0.4
0.6
0.8
1
X-Axis
Example representing the approximation of a quadratic
function by a set of piece-wise linear functions
Element Density
There are two significant considerations with respect
to the density of elements that should be used:
Resolution in the Solution
Where do the fields change most rapidly in the
model?
Change in material properties over a surface (for
nonlinear models)
What is being calculated
Subvolumes
Volumetric effects such as volume currents and the effect of
inhomogeneity due to non-linear materials require the
placement of sub-volumes.
Sub-volumes are needed where:
Electro-statics:
Volume Charge is assigned.
Magnetostatics:
Volume Current is assigned.
In regions containing non-linear materials especially where the
material is partially saturated.
Time Harmonic Magnetics:
Volume current is assigned.
In regions containing non-linear materials especially where the
material is partially saturated
Subvolume Density
Regions where there is a uniform source applied
(volume currents and volume charges ) do not require
any special consideration with respect to subvolume
density. Because the source here is uniform, there is
no consideration for resolution in the solution.
Increase density:
In consideration for what is being calculated.
Forces, torques or flux linkage on a coil.
For non-linear problems:
Change in field and transition from non-saturated
to saturated material within a region
Symmetry
• Symmetry occurs when you have mirror
symmetry across one or more of the principal
geometry planes.
• If the real and equivalent current sources are
mirrored across the symmetry plane, this is
termed “Symmetry”, when they are mirrored
but with opposite polarity, this is termed
“Anti-Symmetry”.
Symmetry
• Image on left exhibits
“Symmetry” across the
X=0 plane and
“Anti-Symmetry” across
the Y=0 and Z=0
planes.
Symmetry
• When you have
permanent magnets,
the definition of
symmetry is opposite to
that of currents.
• The image on the right
shows “Anti-Symmetry”
across the Y=0 plane
and “Symmetry” across
the Z=0 plane for
permanent magnets.
Z
Y
X
Periodicity
• Periodicity occurs when the model exhibits a
repetitive pattern along one or the principal axes or
rotationally about one of the principal axes.
• When the sources repeat themselves with the same
polarity, this is termed “Periodic”. When the sources
repeat with every the polarity of every second source
reversed, this is termed “Anti-Periodic”.
• There is no difference in the definition of “Periodic”
and “Anti-Periodic” for permanent magnets.
Periodicity
• Image on right shows
magnetic coupling with
arrows denoting
direction of magnets
Periodicity
• Two possibilities are 5
sections with “Periodic”
setting or 10 sections
with “Anti-Periodic”
setting.
Symmetry and Periodicity
• Post-processing is performed by deriving the sources
in the image space from those in the modeled space.
• Solution time is saved by accumulating the solution
only in the modeled section.
Analysis
Solver Setup
Plot Types
Figures of Merit
Solution Verification
Batch Processing and Parametrics
Analysis – Solver Setup
Matrix Solver Type – Leave
as Auto
Accuracy Speed Factor
Most cases = 1
Very Thin models may
require increase.
Nonlinear Convergence
Criteria –
Most cases .03 is
adequate.
Very nonlinear  .01
Analysis – Plot Types
Analysis Viewer Dialog
Change quantity to
be displayed
Change vector
component
Change plot type
Analysis – Graphs
Options
Graph on Lines
Segments, or on a
Surface
Number of
evaluation points for
the graph
Analysis – Autograph Utility
Legend
Plot curve
with data
points
Analysis – Autograph Utility
• File menu to print graph or save data
• Graph menu to zoom or pan on the graph.
• Data menu to show or hide the graph data.
Analysis – Autograph Utility
• Right click on a curve or the legend
entry for a curve to display the Curve
Operations menu.
• Interesting features are Differentiation
and Integration operations on the
curve.
• Use Curve Attributes to change color
and data marker.
• Use Hide to hide curves, to clarify
plots with multiple curves.
Analysis – Contour Plots
Reference geometry
Plotting grid density
Color fill on/off
Number of Contours
or Bands to plot
Analysis – Contour Plots
Place a legend for the plot.
Integrate the value of the scalar plot over the
surface or plane.
Analysis – Arrow Plots
Reference geometry
Plotting grid density
Scale arrow size to
field magnitude
on/off
Number of Levels to
plot
Analysis – Arrow Plots
Place a legend for the plot
Analysis – Figures of Merit
Calculate:
Force/Torque on a real part of
the model.
Force/Torque on parts acting as
a test coil
Flux Linkage
Inductance
Analysis - Solution Verification
Simplest Kind:
Solve once
(Perform some “sanity checks”)

Perform calculation 
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Increase elements
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Solve again
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 
Until change in
calculated value
is less than
some criteria
Analysis - Solution Verification
“Reality Checks”
Electrostatics
Computed Voltage vs. Assigned Voltage.
Electric field inside closed conductors is zero.
E•dl = V for known separation of potentials.
Fundamental boundary conditions (Dn).
Magnetics
Force/torque balance.
Amperes Circuital Law (H•dl = I).
Gauss’ Law - total flux crossing a closed path is zero.
Fundamental boundary conditions (Ht).
Analysis - Solution Verification
“Reality Checks” (cont’d)
Eddy Current/Time Harmonic
Total current induced in plane = 0.
Fundamental boundary conditions (Ht and Et) .
Assigned current vs. integration of skin effect current
density.
Batch Processing
• Most useful to solve a set of distinctly different
models, or to perform several operations on one
model.
• Batch mode is set from Utilities menu, then all
commands and entries are recorded.
• Batch files can be edited in a text editor and rerun.
The usual method is to create the batch file in the
program and edit rather than start from scratch.
Parametric Solver
• Analyze a range of values for a particular aspect of
the design.
• Geometry, materials and currents can all be defined
as parameters to be varied during the analysis.
Output
Obtaining Numerical Data
Exporting Visualizations
Numerical Data
• Generate text files of figures of merit.
• Generating data from a graph or plot.
• Generating output from a file of (x,y,z)
coordinates.
Exporting Visualizations
Exporting Bitmap files:
Generate image
Add legends, text, etc.
Select Utilities > Export > Image …
Image saved as bitmap (.BMP) file
Exporting Visualizations
• Generating Animations
Create a set of images to include in the animation
using the method outlined for saving images.
Select Utilities > Export > Animation …
Add all of the bitmaps wanted in the animation.
Select Open from the file selection dialog.
You can then save the animation as a .avi file.
HINT: When generating animations from contour or
arrow plots, use the User Range setting on the dialog
to maintain a constant reference.