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Best Practices for Modifying the Airgap shape #638

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switch order in Best Practices section.
JackB-Ansys Nov 20, 2025
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207 changes: 148 additions & 59 deletions doc/source/user_guide/adaptive_templates.rst
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Expand Up @@ -426,8 +426,17 @@
Using a break point in an Adaptive Template script to investigate variables.

This is a useful tool when working on a Python script, such as an Adaptive Templates script. You can
look into the properties of the Region object, as well as those of the entities such as the start,
end and midpoint coordinates, the angles of Line objects, the radii of Arc objects.
look into the properties of the Region object or the properties of entities such as:

* the start coordinate,

* end coordinate,

* the midpoint coordinate,

* the angles of Line objects,

* the radii of Arc objects.

IDEs (for example PyCharm or VSCode) have a lot of useful features for editing Python scripts. It is
much easier and more efficient to use an IDE to develop Adaptive Templates scripts, rather than the
Expand Down Expand Up @@ -504,69 +513,14 @@
imported region then appears under **Template** in the Geometry tree shown in the
**Geometry -> Editor -> Geometry** tab in Motor-CAD.

Best practices for Adaptive Templates scripting

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[Google.Headings] 'Best practices for Adaptive Templates scripting' should use sentence-style capitalization.
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***********************************************

Adaptive Templates scripts in Motor-CAD can be used in many different ways to customise the electric
machine geometry. Some approaches are more challenging than others. For some types of geometry
customisation, there are some recommended approaches and best practices that should be followed.

Modifying stator slot openings
------------------------------

When using Adaptive Templates to modify the shape of the stator slot opening, there are some best
practices which may be followed to make the process simpler.

If the modifications reduce the available space for conductors, then the **Copper Depth [%]**
parameter in the **Winding -> Definition** tab should be adjusted to reflect the available space for
conductors in the updated slot.

.. figure:: ../images/adaptive_templates/user_guide_slots_1.png
:width: 600pt

A Motor-CAD stator geometry where the stator slot has been modified to be narrower at the slot
opening. The **Stator** region (red, shaded) intersects the **ArmatureSlot** regions (yellow)
and the **Wedge** region (grey). The **Copper Depth [%]** is still set to **100 %**, so the
**ArmatureSlot** regions are still being drawn based on the unmodified Standard Template
geometry.

.. figure:: ../images/adaptive_templates/user_guide_slots_2.png
:width: 500pt

The **Winding -> Definition** tab in Motor-CAD. Setting the **Copper Depth [%]** to **84 %**
means that the conductors, impregnation and slot liner now only fill 84 % of the slot. This
reflects the amount of space available in the modified slot.

.. figure:: ../images/adaptive_templates/user_guide_slots_3.png
:width: 600pt

With the updated **Copper Depth [%]**, the **Stator** region (red, shaded) no longer intersects
the **ArmatureSlot** regions, only the **Wedge** region (grey).

To modify the shape of the **Wedge** region based on a modified **Stator** slot geometry, subtract
the **Stator** region from the **Wedge**:

.. code:: python

wedge = mc.get_region("Wedge")
wedge.subtract(modified_stator)
mc.set_region(wedge)

.. figure:: ../images/adaptive_templates/user_guide_slots_4.png
:width: 600pt

When the **Wedge** region has been modified by subtracting the modified **Stator** region, the
custom stator slot geometry is complete.

.. figure:: ../images/adaptive_templates/user_guide_slots_5.png
:width: 500pt

The updated stator slot can also be visualised in the **Winding -> Definition** tab, now that
the wedge has been updated.



Rounding corners of geometry regions with Adaptive Templates

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------------------------------------------------------------

The Motor-CAD Standard Template geometry has options for automatic corner rounding of the rotor
Expand Down Expand Up @@ -599,8 +553,8 @@
A corner made up of two Line entities (entity 7 and 9) and an Arc (entity 8).

When customising a Motor-CAD geometry with Adaptive Templates, it is much simpler to modify the
geometry when corner rounding is **not selected**. This is because there will be fewer entities
forming the regions (such as the rotor pocket and magnet regions). It is recommended to set the
geometry when corner rounding is **not selected**. This is because fewer entities form the regions
(such as the rotor pocket and magnet regions). It is recommended to set the
**Corner Rounding (Rotor Lamination)** and **Corner Rounding (Magnets)** parameters on the
**Input Data -> Settings -> Geometry** tab to **None (default)**.

Expand Down Expand Up @@ -675,6 +629,141 @@
To apply different corner radii for each corner, you can use the ``Region.round_corner()`` method
and round corners individually.

Modifying the airgap shape
--------------------------

When using Adaptive Templates to modify the shape of the airgap, either by modifying the rotor
surface or the stator surface, there are some best practices which should be followed to avoid
problems with FEA meshing in Motor-CAD.

The airgap (space between the rotor and stator) itself should always be defined by a band of uniform
thickness in Motor-CAD. Take the default Surface Permanent Magnet motor topology as an example.

.. figure:: ../images/adaptive_templates/user_guide_airgap_1.png
:width: 600pt

The default Motor-CAD SPM motor topology, showing the distance between stator lamination
surface and rotor lamination surface and the distance between stator lamination surface and
magnet surface.

This motor has raised magnets that sit on top of the rotor lamination surface. There is a larger gap
between the stator lamination surface and that of the rotor lamination than there is between the
stator lamination surface and the magnet surface. The rotor geometry is defined by including the
**RotorAir** and **RotorAir_1** regions on either side of the magnet, so that the total group of
rotor regions has a continuous outer boundary of equal radius.

Similarly, the stator geometry includes a **StatorAir** region that fills the slot opening. The
total group of stator regions has a continuous inner boundary of equal radius.

.. figure:: ../images/adaptive_templates/user_guide_airgap_2.png
:width: 600pt

The default Motor-CAD SPM motor topology, showing the rotor outer boundary with constant radius
and the stator inner boundary with constant radius.

The outer boundary of the rotor regions and the inner boundary of the stator regions define the
airgap, and it is important that these boundaries remain arcs of continuous radius, despite any
Adaptive Templates modifications to the Motor-CAD model geometry. Any changes to the airgap shape
should be carried out by inserting new **Rotor Air** or **Stator Air** type regions (or by modifying
existing ones) and the original boundary arc shapes should be preserved. If the rotor outer or
stator inner boundaries are changed, so that they do not form an arc of specific radius, the
Motor-CAD model may fail to mesh, or FEA calculation results may be unreliable due to the mesh.

Another best practice to follow when modifying the airgap shape, is to ensure that the regions do
not have any very sharp corners or very narrow geometry features. For example, if the rotor is
modified by adding rotor notches, the edges of the notches can be rounded to form very narrow
**Rotor Air** regions at the rotor boundary.

.. figure:: ../images/adaptive_templates/user_guide_airgap_3.png
:width: 600pt

An IPM motor topology with rounded notches at the rotor boundary.

In this example, the notch region becomes vanishingly narrow at the rotor outer boundary. This
Motor-CAD model fails to mesh due to these geometry features and the FEA calculation cannot be
solved. This problem can be addressed by adding a band of air at the rotor outer boundary.

Motor-CAD uses this approach in the Standard Template geometry for SPM topologies with a non-zero
**Magnet Reduction** value. A **RotorAir** region is included in the geometry, forming the outer
boundary of the group of rotor regions. The minimum thickness of the air region is 0.1 mm.

.. figure:: ../images/adaptive_templates/user_guide_airgap_4.png
:width: 600pt

A SPM motor topology with **Magnet Reduction = 4**. A **RotorAir** region sits on top of the
magnet surface, forming the rotor outer boundary. The air region is 0.1 mm thick at
its narrowest point.

For the rounded rotor notches example, an air band of specified thickness (at least 0.1 mm) should
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@james-packer james-packer Nov 25, 2025

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It would be useful to mention that the user will need to manually change the 'airgap' template dimension, as the template value will need to be (in this example) 0.1 mm less than the actual airgap size, so the total 'airgap' plus 'rotor air' region matches the correct value.

be added at the rotor outer boundary. This air band can be united with the notch regions to form a
single **Rotor Air** region.

.. figure:: ../images/adaptive_templates/user_guide_airgap_5.png
:width: 600pt

An IPM motor topology with rounded notches and a band of air at the rotor boundary. The air
region is 0.1 mm thick at its narrowest point.

It is best practice to take this approach when modifying the shape of the airgap. If you ensure that
any new regions at the airgap boundary are at least 0.1 mm thick as a minimum, problems with the
the airgap mesh should be avoided.


Modifying stator slot openings
------------------------------

When using Adaptive Templates to modify the shape of the stator slot opening, there are some best
practices which may be followed to make the process simpler.

If the modifications reduce the available space for conductors, then the **Copper Depth [%]**
parameter in the **Winding -> Definition** tab should be adjusted to reflect the available space for
conductors in the updated slot.

.. figure:: ../images/adaptive_templates/user_guide_slots_1.png
:width: 600pt

A Motor-CAD stator geometry where the stator slot has been modified to be narrower at the slot
opening. The **Stator** region (red, shaded) intersects the **ArmatureSlot** regions (yellow)
and the **Wedge** region (grey). The **Copper Depth [%]** is still set to **100 %**, so the
**ArmatureSlot** regions are still being drawn based on the unmodified Standard Template
geometry.

.. figure:: ../images/adaptive_templates/user_guide_slots_2.png
:width: 500pt

The **Winding -> Definition** tab in Motor-CAD. Setting the **Copper Depth [%]** to **84 %**
means that the conductors, impregnation and slot liner now only fill 84 % of the slot. This
reflects the amount of space available in the modified slot.

.. figure:: ../images/adaptive_templates/user_guide_slots_3.png
:width: 600pt

With the updated **Copper Depth [%]**, the **Stator** region (red, shaded) no longer intersects
the **ArmatureSlot** regions, only the **Wedge** region (grey).

To modify the shape of the **Wedge** region based on a modified **Stator** slot geometry, subtract
the **Stator** region from the **Wedge**:

.. code:: python

wedge = mc.get_region("Wedge")
wedge.subtract(modified_stator)
mc.set_region(wedge)

.. figure:: ../images/adaptive_templates/user_guide_slots_4.png
:width: 600pt

When the **Wedge** region has been modified by subtracting the modified **Stator** region, the
custom stator slot geometry is complete.

.. figure:: ../images/adaptive_templates/user_guide_slots_5.png
:width: 500pt

The updated stator slot can also be visualised in the **Winding -> Definition** tab, now that
the wedge has been updated.






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