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ANSYS Maxwell 3D Field Simulator v15 User’s Guide
7.1
Example (Transient) – Stranded Conductors
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Maxwell v15
Stranded Conductors This example is intended to show you how to create and analyze a transient
problem on a Switched Reluctance Motor geometry using the Transient solver in
the Ansoft Maxwell 3D Design Environment.
Within the Maxwell 3D Design Environment, solid coils can be modeled as
Stranded Conductors. There are many advantages to using Stranded
Conductors when modeling coils that have multiple turns. The first obvious
advantage is that a coil with multiple wires, say 2500, can be modeled as a single
object as opposed to modeling each wire which would be impracticable. Defining
a Stranded Conductor means that the current density will be uniform throughout
the cross section of the conductor.
The example that will be used to demonstrate how Stranded Conductors are
implemented is a switched Reluctance Motor. This switched reluctance motor
will have four phases and two coils per phase, thus we can show how
independent coils can be grouped to create windings.
Note: This tutorial shows how to setup a stranded conductor using Transient
Solver and does not involve details regarding geometry creation. To see
geometry creation details, please refer the example 5.3
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
7.1
Example (Transient) – Stranded Conductors
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Maxwell v15
Theory – Transient Solver When creating Windings in the Transient solver, it is assumed that all of the coils
used to make up that winding are connected in series.
When creating a Winding and using voltage sources, the Winding Panel asks for
the Initial Current, Resistance, Inductance, and Voltage.
Initial Current: This is an initial condition used by the solver
Resistance: This is the DC resistance of the total winding; for the Phase_A
winding, this is the resistance of Coil_A1 and Coil_A2 in series.
Inductance: This is any extra inductance that is not modeled that needs to
be added. For example, and additional line inductance or source
inductance.
Voltage: This is the source voltage which can be a constant, function, or
piecewise linear curve.
A sketch of the Phase_A Winding circuit is:
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
7.1
Example (Transient) – Stranded Conductors
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Theory – Transient Solver (Continued) If the Winding was defined as a Current Source instead of a Voltage Source, the
only additional field to modify is the initial current. The circuit would look like this:
The DC Resistance and Extra Inductance is not needed since this is a
current source and its value is guaranteed regardless of any value for the
DC Resistance or Extra Inductance.
The third option for the Winding setup is External. This means that there is an
external circuit that is made up of arbitrary components. Please refer to the
Topic paper on External Circuits for the details on how this is implemented.
Please note that if the two coils that make up the Phase_A winding were
connected in parallel instead of series, then two separate Windings would need
to be created.
In regards to the current density, the Transient solver treats stranded conductors
the same as in the Magnetostatic solver; that is, the current density is uniform
across the terminal and the solver calculates the magnetic field intensity H
directly and the current density vector J indirectly.
There are two options when defining the type of winding: Solid or Stranded. This
write up is for Stranded Windings only. For a full description of how Solid
windings are implemented, please refer to the Topic paper Solid Conductors.
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
7.1
Example (Transient) – Stranded Conductors
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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
3D Solid Modeling
Boolean Operations: Split
Boundaries/Excitations
Current: Stranded
Analysis
Transient
Results
Field Calculator
Field Overlays:
Magnitude B
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
7.1
Example (Transient) – Stranded Conductors
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Maxwell v15
Launching Maxwell To access Maxwell:
1. Click the Microsoft Start button, select Programs, and select Ansoft >
Maxwell 15.0 and select Maxwell 15.0
Setting Tool Options To set the tool options:
Note: In order to follow the steps outlined in this example, verify that the
following tool options are set :
1. Select the menu item Tools > Options > Maxwell 3D Options
Maxwell Options Window:
1. Click the General Options tab
Use Wizards for data input when creating new
boundaries: Checked
Duplicate boundaries/mesh operations with geometry:
Checked
2. Click the OK button
2. Select the menu item Tools > Options > Modeler Options.
Modeler Options Window:
1. Click the Operation tab
Automatically cover closed polylines: Checked
2. Click the Display tab
Default transparency = 0.8
3. Click the Drawing tab
Edit property of new primitives: Checked
4. Click the OK button
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
7.1
Example (Transient) – Stranded Conductors
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Maxwell v15
Open Existing File To Open a File
Select the menu item File > Open
Locate the file Ex_5_3_Stranded_Conductors.mxwl and Open it
Set Solution Type To set the Solution Type:
Select the menu item Maxwell 3D > Solution Type
Solution Type Window:
1. Choose Magnetic > Transient
2. Click the OK button
Save File To Save File
Select the menu item File > Save
Save the file with a name Ex_7_1_Transient_Reluctance_Motor
Delete Excitations Delete Specified Excitations
As we have opened the file from a Magnetostatic setup, the excitation are
already existing in the file
Delete all excitations from Project Manager tree as new excitations will be
specified according to Transient Solver
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Example (Transient) – Stranded Conductors
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Specify Coil Terminals To Specify Coil terminals
Expand the history tree for Sheets
Press Ctrl and select the all sheet objects
Select the menu item Maxwell 3D > Excitations > Assign > Coil Terminal
In Coil Terminal Excitation window,
1. Base Name: CoilTerminal
2. Number of Conductors: 150
3. Press OK
Specify Windings To Add Winding
Select the menu item Maxwell 3D > Excitations > Add Winding
In Winding window,
1. Name: Winding1
2. Type: Voltage
3. Stranded: Checked
4. Initial Current: 0 A
5. Resistance: 2.3 ohm
6. Inductance: 0 mH
7. Voltage: 120 V
8. Press OK
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Example (Transient) – Stranded Conductors
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Add Terminals to Winding
Expand the Project tree to display terminals
Right click on the Winding1 from the Project tree and select Add Terminals
In Add Terminals window,
1. Press Ctrl and select the terminals CoilTerminal_1 and
CoilTerminal_2
2. Press OK
Repeat the same steps to three more windings
Winding2
CoilTerminal_3
CoilTerminal_4
Winding3
CoilTerminal_5
CoilTerminal_6
Winding4
CoilTerminal_7
CoilTerminal_8
Assign Mesh Operations Note: The transient solver does not use automatic adaptive meshing.
Assign Mesh Operations for Coils
Press Ctrl and select all the object corresponding to coils from history tree
Select the menu item Maxwell 3D > Mesh Operations > Assign > Inside Selection > Length Based
In Element Length Based Refinement window,
1. Restrict Length of Elements: Unchecked
2. Restrict the Number of Elements: Checked
3. Maximum Number of Elements: 16000 (2000/tets per coil)
4. Click the OK button
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Example (Transient) – Stranded Conductors
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Assign Mesh Operations for Stator and Rotor
Press Ctrl and select the objects Stator and Rotor from the history tree
Select the menu item Maxwell 3D > Mesh Operations > Assign > Inside Selection > Length Based
In Element Length Based Refinement window,
1. Restrict Length of Elements: Unchecked
2. Restrict the Number of Elements: Checked
3. Maximum Number of Elements: 4000 (2000/tets per object)
4. Click the OK button
Analysis Setup To create an analysis setup:
Select the menu item Maxwell 3D > Analysis Setup > Add Solution Setup
Solution Setup Window:
1. Click the General tab:
Stop time: 0.02s
Time step: 0.002s
2. 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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Example (Transient) – Stranded Conductors
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Create Quick Report To Create a Report
Select the menu item Maxwell 3D > Results > Create Transient Reports > Rectangular Plot
In Report Window,
1. Category: Winding
2. Quantity: Press Ctrl and select Current(Winding1),
Current(Winding2), Current(Winding3), Current(Winding4)
3. Select the button New Report
4. Press Close
Right Click on the plot and select Trace Characteristics > Add
In Add Trace Characteristics window,
Category: Math
Function: Max
Select Add and Done
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Example (Transient) – Stranded Conductors
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Calculate Current To Calculate Current
Select the menu item Maxwell 3D > Fields > Calculator
In Fields Calculator window,
1. Select Input > Quantity > J
2. Select Vector: Scal? > Scalar Z
3. Select Input > Geometry
Set the radio button to Surface
From the list select Terminal_A1
Press OK
4. Select Scalar > (Integrate)
5. Select Input > Number
Type: Scalar
Value: 150 (Number of Conductors)
Press OK
6. Select General > /
7. Select Output > Eval
8. Press Done to close the calculator
Note that the value reported in calculator is same as the value shown in
plot in the last step
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Example (Transient) – Stranded Conductors
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Maxwell v15
Create Quarter Symmetry Geometry So far we have been working with full geometry. Often it is useful to use
symmetry in order to reduce the problem size and thus decrease the solution
time. In this section, we’ll show how to create the symmetric model and its
impact on stranded conductors.
Create Symmetry Design Copy Design
Select the design Maxwell3DDesign1 in Project Manager window, right
click and select Copy
Select project Ex_7_1_transient_reluctance_motor in Project Manager
window and select Paste
Rotate the Geometry to Create Quarter Symmetry Before splitting the model to create a ¼ model, all of the objects need to be
rotated.
To Rotate Model
Select the menu item Edit > Select All
Select the menu item Edit > Arrange > Rotate
In Rotate Window,
1. Axis: Z
2. Angle: 22.5 deg
3. Press OK
To Rotate the object Rotor
Select the object Rotor from the history tree
Select the menu item Edit > Arrange > Rotate
In Rotate Window,
1. Axis: Z
2. Angle: 7.5 deg
3. Press OK
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Example (Transient) – Stranded Conductors
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Split Model Divide by XY Plane
Select the menu item Edit > Select All
Select the menu item Modeler > Boolean >Split
In Split window
1. Split plane: XY
2. Keep fragments: Positive side
3. Split objects: Split entire selection
4. Press OK
Divide by YZ Plane
Select the menu item Edit > Select All
Select the menu item Modeler > Boolean >Split
In Split window
1. Split plane: YZ
2. Keep fragments: Negative side
3. Split objects: Split entire selection
4. Press OK
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Example (Transient) – Stranded Conductors
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Redefining the Terminals
When the entire coil is not being modeled and the coil cuts the surface of the
solution boundary (called Region in this example), terminals need to be defined
that are coincident with the Coil and the Region.
To Redefine Terminals
Press Ctrl and select the objects Region, Stator and Rotor
Select the menu item View > Visibility > Hide Selection > Active View
Select the menu item Edit > Select > Faces
Select the face of Coil_A2 that coincides with region as shown in below
image
Select the menu item Maxwell 3D > Excitations > Assign > Coil Terminal
In Coil Terminal Excitation window,
1. Name: Terminal_A2_1
2. Number of Conductors: 150
3. Press OK
Select the other face of the object Coil_A2 that touches with region
Select the menu item Maxwell 3D > Excitations > Assign > Coil Terminal
In Coil Terminal Excitation window,
1. Name: Terminal_A2_2
2. Number of Conductors: 150
3. Press the button Swap Direction to invert current direction
4. Press OK
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Example (Transient) – Stranded Conductors
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Maxwell v15
Redefine coil terminals as specified in below image for other objects
Ensure the direction of current is consistent in all coils.
Add Terminals to Windings To Add Terminals
Right click on Winding1 which exists from previous settings and select Add
Terminals
In Add Terminals window,
1. Press Ctrl and select the terminals Terminal_A2_1 and
Terminal_A2_2
2. Press OK
Repeat the same steps to three more windings
Winding2
Terminal_B1_1, Terminal_B1_2, Terminal_B2_1, Terminal_B2_2
Winding3
Terminal_C1_1, Terminal_C1_2
Winding4
Terminal_D1_1, Terminal_D1_2
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
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Example (Transient) – Stranded Conductors
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Maxwell v15
Modify Mesh Operations To Modify Mesh Operations
Expand the Project Manager tree to view Mesh Operations
Double click on the mesh operation Length1 that corresponds to Coils
In Element Length Based Refinement window,
1. Change Maximum Number of Elements to 4000 (1/4th of the value
used for Full Model
2. Press OK
Double click on Length2 that corresponds to Stator and Rotor
In Element Length Based Refinement window,
1. Change Maximum Number of Elements to 1000 (1/4th of the value
used for Full Model
2. Press OK
Set Symmetry Multiplier To Set Symmetry Multiplier
Select the menu item Maxwell 3D > Model > Set Symmetry Multiplier
Set Symmetry Multiplier value of 4 in the window
Press OK
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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Example (Transient) – Stranded Conductors
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Results To View Results
Expand the Project Manager tree to view XY Plot 1 under Results
Create Sheet Object for Current Calculation
Select any of the end faces of Coil_A2
Select the menu item Modeler > List > Create > Face List
To Calculate Current
Select the menu item Maxwell 3D > Fields > Calculator
In Fields Calculator window,
1. Select Input > Quantity > J
2. Select Vector: Scal? > Scalar Z
3. Select Input > Geometry
Set the radio button to Surface
From the list select Facelist1
Press OK
4. Select Scalar > (Integrate)
5. Select Input > Number
Type: Scalar
Value: 150 (Number of Conductors)
Press OK
6. Select General > /
7. Select Output > Eval
8. Press Done to close the calculator
The value of current is around 52 A which is save as previous
ANSYS Maxwell 3D Field Simulator v15 User’s Guide
7.1
Example (Transient) – Stranded Conductors
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Maxwell v15
Half Coils
Note: If the cross section of the coil is cut in half, then the number of conductors
is half. An example for a simple coil is shown below:
H = 20mm H = 10mm
Modeling the Full Coil:
Conductor Number = 150
Symmetry Multiplier = 1
Cut the Full Coil in half and use an
Odd Symmetry Boundary:
Conductor Number = 75