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ANSYS Maxwell 3D Field Simulator v15 User’s Guide
12.1
Multiphysics Coupling - IGBT
12.1-‹#›
Maxwell v15
Insulated Gate Bipolar Transistor (IGBT) Insulated Gate Bipolar Transistor is power semiconductor device used for high
efficiency and fast switching in modern appliances such as electric cars, trains,
variable speed refrigerators, air-conditioners, etc.
These devices are designed for carrying high currents and many times lead to
failures in Bondwires due to high thermal stresses.
In this example, we will be modeling an IGBT device using Maxwell to get Heat
losses and Lorentz forces in Bondwires and then transfer this data to ANSYS
Mechanical to calculate Stresses on the wires and determine regions prone to
failure.
In addition, thermal conductivity of all components will be set as function of
temperature. Temperature data from ANSYS Mechanical will be transferred back
to Maxwell to calculate exact heat losses.
Total geometry is a six leg IGBT system. To simplify the tutorial, we will be
modeling only one leg in the example.
Maxwell
Steady State Thermal
Static Structural
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
ANSYS Maxwell Design Environment The following features of the ANSYS Maxwell Design Environment are used to
create the models covered in this topic
Boundaries/Excitations
Current: Stranded
Analysis
Magnetostatic
Steady State Thermal (ANSYS Mechanical)
Static Structural (ANSYS Mechanical)
Results
Force
Field Overlays:
J Field
Temperature
Equivalent Stress
Deformation
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
12.1-‹#›
Maxwell v15
Prerequisites To Run this Tutorial
ANSYS Workbench R13/R14 needs to be installed for performing this
tutorial
ANSYS Mechanical licenses are needed
Maxwell needs to be integrated with ANSYS Workbench while installation
Launching ANSYS Workbench To launch Workbench:
1. Click the Microsoft Start button, select Programs, and select ANSYS 14.0
> Workbench
Open Maxwell Project To Open Maxwell File
In ANSYS Workbench Project window, select the menu item File > Import
Set file type to Maxwell Project File (.mxwl)
Locate the file Ex_5_9_IGBT_One_Leg.mxwl and Open it
Maxwell Analysis System will be automatically created as shown in below
image
Launch Maxwell To Launch Maxwell
Right click on Geometry tab of Maxwell 3D Analysis system and select
Edit
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
12.1
Multiphysics Coupling - IGBT
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Maxwell v15
Description of Geometry Six Leg IGBT Device
Below shown is the image of a six leg IGBT device.
The device has three phase supply, Positive and Negative terminals as
shown in image
There are 12 IGBT chips and 12 diodes, six on each side of terminal wires
Diodes and IGBT chips are connected with each other using Aluminum
Bondwires
In this tutorial, we will be considering only one leg of geometry which is
shown in rectangle in below image.
Negative
Terminal
Positive
Terminal
Phase A Phase B Phase C
One Leg
Diodes
12 in Total
IGBTs
12 in Total
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
12.1
Multiphysics Coupling - IGBT
12.1-‹#›
Maxwell v15
Input File Description One Leg IGBT Geometry
Input file contains the geometry of one leg separated out of Six leg IGBT
system. Names and Material definition to all parts is already done. Model
tree should look as shown in the image.
A_Bar, A_Out, A_Upper corresponds to Phase A of Supply. N_Bar
corresponds to Negative terminal while P_Bar corresponds to the positive
terminal.
Diodes A1_B, A2_B and IGBT A2_B are in “OFF” conditions. They have
been assigned with material as “vacuum” as they do not contribute to the
field.
Bondwires G1, G2, G3 and G4 will be the focus of this simulation as these
thin wires carry very high currents and more likely to fail due to thermal
stresses.
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
12.1-‹#›
Maxwell v15
Set Solution Type To set the Solution Type:
Select the menu item Maxwell 3D > Solution Type
Solution Type Window:
1. Choose Magnetostatic
2. Click the OK button
Assign Excitations To Assign Phase Current
Select the menu item Edit > Select > Faces or press F from the keyboard to
change selection to faces
Select the face of A_Out as shown in image
Select the menu item Maxwell 3D > Excitations > Assign >Current
In Current Excitation window,
1. Name: PhaseA
2. Value: 40 A
3. Type: Solid
4. Direction: Positive Z
5. Press OK
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
12.1-‹#›
Maxwell v15
To Assign Terminal Current to P_Bar
Select the face of P_Bar as shown in image
Select the menu item Maxwell 3D > Excitations > Assign >Current
In Current Excitation window,
1. Name: PTerm
2. Value: 20 A
3. Type: Solid
4. Direction: Negative X
5. Press OK
To Assign Terminal Current to A_Upper
Select the face of A_Upper as shown in image
Select the menu item Maxwell 3D > Excitations > Assign >Current
In Current Excitation window,
1. Name: PTerm2
2. Value: 20 A
3. Type: Solid
4. Direction: Negative X
5. Press OK
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
Set Temperature Dependent Material Properties Note: In this step, thermal conductivity of Copper and Aluminum will be set as
function of temperature. At the start, temperature of all objects is considered to
be at 22 ̊C. After Solving for Temperature in ANSYS Mechanical, temperature
data will be transferred back to Maxwell and solution will recalculated with new
temperatures applied through ANSYS Mechanical.
To Set Thermal Modifier for Copper
Right click on copper material tab from the history tree and select
properties
In Select Definition window,
1. Select option View/Edit Material
2. In View/Edit Material window
1. Thermal Modifier: Checked
2. Bulk Conductivity:
Thermal Modifier: Select Edit
In Edit Thermal Modifier window,
Modifier: Set to
if(Temp > 1000, 0.2, if(Temp < 0, 1, 1/(1+0.004*Temp)))
Press OK
3. Press OK
3. Press OK
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
To Set Thermal Modifier for Aluminum
Right click on aluminum material tab from the history tree and select
properties
In Select Definition window,
1. Select option View/Edit Material
2. In View/Edit Material window
1. Thermal Modifier: Checked
2. Bulk Conductivity:
Thermal Modifier: Select Edit
In Edit Thermal Modifier window,
Modifier: Set to
if(Temp > 1000, 0.2, if(Temp < 0, 1, 1/(1+0.004*Temp)))
Press OK
3. Press OK
3. Press OK
Set Object Temperature To Set Object Temperature
Select the menu item Maxwell 3D > Set Object Temperature
In Temperature of Objects window,
1. Include Temperature Dependence: Checked
2. Enable Feedback: Checked
3. Ensure all objects are set to 22 cel
4. Press OK
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
Define Region Create Simulation Region
Select the menu item Draw > Region
In Region window,
1. Pad individual directions: Checked
2. +X = 0
3. -X = 100
4. +Y = 100
5. -Y = 100
6. +Z = 0
7. -Z = 100
8. Press OK
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
Analysis Setup To create an analysis setup:
Select the menu item Maxwell 3D > Analysis Setup > Add Solution Setup
Solution Setup Window:
1. General Tab
Percentage Error: 0.2
2. ConvergenceTab
Refinement Per Pass: 50
3. Click the OK button
Model Validation To validate the model:
Select the menu item Maxwell 3D > Validation Check
Click the Close button
Note: To view any errors or warning messages, use the Message Manager.
Analyze To start the solution process:
1. Select the menu item Maxwell 3D > Analyze All
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
Solution Data To view the Solution Data:
Select the menu item Maxwell 3D > Results > Solution Data
To view the Profile:
1. Click the Profile Tab.
To view the Convergence:
1. Click the Convergence Tab
Note: The default view is for convergence is Table. Select
the Plot radio button to view a graphical representations of
the convergence data.
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
Mag_J Plot Hide Region
Select the menu item Edit > Select > Objects or press O from the keyboard
to change selection to Objects
Select Region from the history tree
Select the menu item View > Visibility> Hide Selection > Active View
Create Field Plot
Select the menu item Edit > Select All Visible
Select menu item Maxwell 3D > Fields > Fields > J > Mag_J
In Create Field Plot window
1. Plot on surface only: Checked
2. Select Done
Modify Plot Attributes
Double click on the legend to change plot properties
In the window
1. Scale tab
Num. Division: 50
User Limits: Checked
1. Min: 1000
2. Max: 5e+7
Log: Checked
2. Press Apply and Close
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
12.1
Multiphysics Coupling - IGBT
12.1-‹#›
Maxwell v15
The plot of the Mag_J will be as below:
Volume current density is high in thin sections of Bondwire_G1 and
Bondwire_G2
Exit Maxwell To Close Maxwell
Select the menu item File > Close Desktop
Save Project Save Workbench Project
To save the project, goto the Workbench project window and select menu
item File > Save As
Save the file with the name Ex_12_1_IGBT_One_Leg
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
12.1
Multiphysics Coupling - IGBT
12.1-‹#›
Maxwell v15
Create Steady State Thermal System To Create a Steady State Thermal Analysis System
Select Steady State Thermal system from the Analysis Systems list
Drag and drop it on the Solution tab of Maxwell 3D Analysis System
Drag and drop the geometry tab of Maxwell analysis system on the
Geometry tab of the Steady State Thermal system
Note: By Dropping Steady State Thermal Analysis System onto Solution
tab of Maxwell System we are establishing a link between Solution tab of
Maxwell and Setup tab of Steady State thermal Analysis System. This will
enable the data transfer from Maxwell to ANSYS Mechanical
Update Maxwell Cell To Update Maxwell Solution
Right click on Solution tab of Maxwell 3D Analysis System and select
update
A tick mark will appear adjacent to Solution tab of Maxwell
Right click on Geometry tab of Steady-State Thermal system and select
Refresh
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
Define Material Database To Specify Material Data
Right click on Engineering Data tab and select Edit
In Engineering Data window,
1. Select the icon Engineering Data Sources
2. From Engineering Data Sources, select the tab General Materials
3. Press Ctrl and select materials Aluminum Alloy, Copper Alloy and
Silicon Anisotropic, right click and select Add
4. Select Return to Project to exit Engineering Data
Launch ANSYS Mechanical To Launch ANSYS Mechanical
Right click on Model tab of Steady State Thermal Analysis System and
select Edit
In ANSYS Mechanical window, a tab corresponding to Maxwell link will be
automatically added
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
12.1-‹#›
Maxwell v15
Set Units To Set Unit System
Select the menu item Units > Metric (mm, kg, N, s, mV, mA)
Rest of the tutorial will be done in this unit system
Define Materials To Define Copper Material
Expand the Geometry tab from the History tree
Press Ctrl and select the objects A_Bar, P_Bar, AA_Plate, AP_Plate,
AN_Plate, N_Bar, A_Out and A_Upper
In Details View Window:
1. Material:
Assignment: Set to Copper Alloy
To Define Aluminum Material
Press Ctrl and select the objects Bonwire_G1, Bondwire_G2, Bondwire_3
and Bondwire_G4
In Details View Window:
1. Definition:
Assignment: Set to Aluminum Alloy
To Define Silicon Material
Press Ctrl and select the objects Diode_A1_T, Diode_A1_B, Diode_A2_T,
Diode_A2_B, IGBT_A1_T, IGBT_A1_B, IGBT_A2_T and IGBT_A2_B
In Details View Window:
1. Material:
Assignment: Set to Silicon Anisotropic
Non-linear Effects: No
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
12.1
Multiphysics Coupling - IGBT
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Maxwell v15
Assign Mesh Parameters Note: Mesh size variation from bondwires to the bodies attached with it can not
be too large. In order to avoid this, we need to specify smaller mesh sizes to
these bodies.
To Assign Mesh Parameters for Bondwires
Right click on Mesh tab from the tree and select Insert > Sizing
In Details of Sizing window,
1. Geometry:
Change the selection filter to “Bodies”
Press Ctrl and select all Bondwires from Graphic window
Press Apply
2. Element Size: 0.1mm
To Assign Mesh Parameters for Bondwires
Right click on Mesh tab from the tree and select Insert > Sizing
In Details of Sizing window,
1. Geometry:
Press Ctrl and select the bodies AA_Plate, Diode_A1_T,
Diode_A2_T, IGBT_A1_T and IGBT_A2_T from Graphic
window
Press Apply
2. Element Size: 0.25mm
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
Generate Mesh To Launch Meshing
Right click on Mesh tab and select Generate Mesh
Mesh will be generated and displayed on the Graphic Window
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
Import Data from Maxwell To Import Heat Generation from Maxwell
Right click on the tab Imported Load (Maxwell3DSolution) and select Insert > Heat Generation
In Details of Imported Heat Generation window,
1. Geometry
Right click in graphic window and select “Select All”
Press Apply
Right click on the tab Imported Load (Maxwell3DSolution) and select Import
Load
Note: An Import Load transfer summery will be created below “Imported
Heat Generation”. This lists error in data transfer due to variation of mesh
in Maxwell and ANSYS Mechanical. The value of scale should be close to
1 in important regions.
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
12.1-‹#›
Maxwell v15
Specify Convective Boundary To Assign Convective Boundary
Right click on Steady State Thermal tab from the tree and select Insert > Convection
In Details of Convection window,
1. Geometry:
Change the selection filter to “Faces”
Right click in graphic window and select “Select All”
Press Ctrl and select bottom faces as shown in below image
to remove them from selection
Press Apply
2. Film Coefficient: 1e-4 W/mm2 .° C
Create Temperature Field Plot To Create Temperature Contours
Right click on Solution tab from the tree and select Insert > Thermal > Temperature
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
Solve Thermal Setup To Run the Solution
Right click on Solution tab and select Solve
Solution progress will be shown as below
Temperature Contours Maximum Temperature is in Bondwires which is around 81 ̊C
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
Transfer Object Temperatures to Maxwell To Transfer Temperature Data to Maxwell
Right click on the tab Imported Load (Maxwell3DSolution) and select
Export Results
Temperatures calculated by Steady State Thermal will be transferred back
to Maxwell
Exit Steady State Thermal To Close ANSYS Mechanical
Select the menu item File > Close Mechanical
Solve Maxwell with Imported Temperatures To Launch Maxwell
Right click on Solution tab of Maxwell 3D analysis system and select Edit
To start the solution process:
Select the menu item Maxwell 3D > Analyze All
Maxwell will read imported temperatures from ANSYS Mechanical and
solve using imported temperature data
Note: Maxwell will now calculate heat losses based on imported
temperatures which can be again applied back to Steady State Thermal
Solver to get refined temperature distribution. These temperatures in turn
can be applied to Maxwell. The process can be repeated until there is no
significant change in Temperature results obtained
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
Temperature Distribution in Maxwell
Temperature Filed plot can be can be created in Maxwell which will show
imported temperatures
Select the menu item Edit > Select All Visible
Select menu item Maxwell 3D > Fields > Fields > Other > Temperature
In Create Field Plot window
1. Plot on surface only: Checked
2. Select Done
Note: As we applied temperature based properties only for Copper and
Aluminum, plot is for the objects having those materials.
Close Maxwell
Select the menu item File > Close Desktop
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
Create Static Structural System To Create Static Structural Analysis System
Select Static Structural system from the Analysis Systems list
Drag and drop it on the Solution tab of Steady State Thermal Analysis
System
Select Solution tab of Maxwell 3D Analysis system, drag and drop it on
Setup tab of Static Structural Analysis System
Note: By dropping Solution tab of Maxwell onto Setup tab of Static
Structural System, a link will be created between them. This will ensure
transfer of Lorentz Forces from Maxwell to ANSYS Mechanical
Update Steady State Thermal Cell To Update Thermal Cell
Right click on Results tab of Steady State Analysis System and select
update
New temperature plot can be seem by opening Steady State Thermal
window
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
12.1
Multiphysics Coupling - IGBT
12.1-‹#›
Maxwell v15
Launch ANSYS Mechanical To Launch ANSYS Mechanical
Right click on Setup tab of Static Structural Analysis System and select
Edit
Import Forces from Maxwell To Import Lorentz Forces from Maxwell
Right click on the tab Imported Load (Maxwell3DSolution) and select Insert > Body Force Density
In Details of Body Force Density window,
1. Geometry:
Change the selection filter to “Bodies”
Press Ctrl and select all bondwires from the graphic window
Press Apply
Right click on the tab Imported Load (Maxwell3DSolution) and select Import
Load
Specify Support To Specify Supports
Right click on Static Structural tab of tree and select Insert > Frictionless Support
In Details of Frictionless Support window
1. Geometry:
Select bottom faces of geometry as shown in image
Press Apply
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
Create Field Plots To Stress Field Plots for Bondwires
Right click on Solution tab and select Insert > Stress > Equivalent (von-Mise
In Details of Equivalent Stress window
1. Geometry:
Change the selection filter to “Bodies”
Select all bondwires
Press Apply
To Deformation Field Plots for Bondwires
Right click on Solution tab and select Insert > Deformation > Total
In Details of Total Deformation window
1. Geometry:
Select all bondwires
Press Apply
Solve Structural Setup To Run the Solution
Right click on Solution tab and select Solve
Solution progress will be shown as below
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Multiphysics Coupling - IGBT
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Maxwell v15
Field Plots Equivalent Stress
Maximum stress resulting in wires can be compared with the material
properties to predict the failure region.
Deformation
Note: Deformation images are magnified. To view results to the scale
Change the Result to True Scale
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
12.1
Multiphysics Coupling - IGBT
12.1-‹#›
Maxwell v15
Close ANSYS Mechanical To Close ANSYS Mechanical
Select the menu item File > Close Mechanical
Save Workbench project To Save Project
Select the menu item File > Save