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ANSYS Maxwell 3D Field Simulator v15 User’s Guide 7.1 Example (Transient) – Stranded Conductors 7.1-‹#› 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

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Page 1: Maxwell v15 7 - cadfamily.com · the Ansoft Maxwell 3D Design Environment. ... Maxwell v15 ANSYS Maxwell Design Environment ... ANSYS Maxwell 3D Field Simulator v15 User’s Guide

ANSYS Maxwell 3D Field Simulator v15 User’s Guide

7.1

Example (Transient) – Stranded Conductors

7.1-‹#›

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

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ANSYS Maxwell 3D Field Simulator v15 User’s Guide

7.1

Example (Transient) – Stranded Conductors

7.1-‹#›

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:

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Example (Transient) – Stranded Conductors

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Maxwell v15

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.

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7.1

Example (Transient) – Stranded Conductors

7.1-‹#›

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

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ANSYS Maxwell 3D Field Simulator v15 User’s Guide

7.1

Example (Transient) – Stranded Conductors

7.1-‹#›

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

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7.1

Example (Transient) – Stranded Conductors

7.1-‹#›

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

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7.1

Example (Transient) – Stranded Conductors

7.1-‹#›

Maxwell v15

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

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Example (Transient) – Stranded Conductors

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Maxwell v15

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

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7.1

Example (Transient) – Stranded Conductors

7.1-‹#›

Maxwell v15

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

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7.1

Example (Transient) – Stranded Conductors

7.1-‹#›

Maxwell v15

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

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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

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

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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

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ANSYS Maxwell 3D Field Simulator v15 User’s Guide

7.1

Example (Transient) – Stranded Conductors

7.1-‹#›

Maxwell v15

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

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7.1

Example (Transient) – Stranded Conductors

7.1-‹#›

Maxwell v15

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

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7.1

Example (Transient) – Stranded Conductors

7.1-‹#›

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

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7.1

Example (Transient) – Stranded Conductors

7.1-‹#›

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

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7.1

Example (Transient) – Stranded Conductors

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Maxwell v15

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

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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