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Hello, Motor Fans:

In this blog I discuss how to use the Thermal physics model in Ansys Motor-CAD to perform thermal analysis on an IPM motor. I show the various cooling systems that can be applied and demonstrate a few calculations including steady state, simple transient, and duty cycle.



Select the Thermal physics module which will reveal relevant geometry such as the motor housing used for cooling that is not shown in other physics modules. Below there are numerous settings in various tabs to configure for modelling cooling.



Thermal Model Setup

Setting up the thermal model involves applying the following:

  • Units: set the unit for the volume flow rate.
  • Cooling options: enable Cooling Systems.
  • Housing Water Jacket Flow Options: set Fan Definition, Fluid Volume Flow Rate.
  • Housing Water Jacket Fluid Flow: set Data, Properties, Duct Wall Roughness, Cooling Options, Channel Data.
  • Cooling Settings: set the spray cooling nozzle definition, and other settings. 
  • Spray Cooling Flow Options: select the Nozzle configurations.
  • Spray Cooling Fluid Flow: set Fluid Data, Properties, Nozzle Data.
  • Interfaces: set the Goodness of Adherence between surfaces.
  • Materials: update selections for the Impregnation and Slot Liner.
  • Model Settings: set the number of axial slices.
  • Losses Settings: select the AC Winding Losses calculation type and the Temperature Exponent.



The cooling systems that are selected will have corresponding tabs appear.


Choose the fan definition.


Define the housing water jacket fluid flow.


Apply the cooling settings.


Choose the nozzle configuration.


Define the Spray Cooling fluid flow.


Apply the Goodness of Adherence between surfaces for the Stator Lamination Housing and the Bearings.


Choose material for the Impregnation and the Slot Liner.


Choose the number of axial slices.


Choose the AC Winding Losses calculation type and the Temperature Exponent (defines how AC losses scale with temperature).



Select the LAB Model. Go to the Operating Point tab and apply settings for calculating the operating point. We will choose Maximum Temperature as the input definition, and specify the Speed and Maximum Temperatures for the Stator Winding and Magnet, and Motor-CAD will determine required operating point for these conditions.


Then go to the Thermal tab and choose Hotspot for the Maximum Winding Node. 


Next go back to the Operating Point and select Calculate Operating Point.


Go to the E-Magnetic model and see the operating point has been transferred to it from the LAB calculation. Enable the Coupling E-Magnetic Losses --> Thermal. Select Torque under On Load for the Performance Test. Run the analysis by selecting Solve E-magnetic Model.


Steady State Calculation

Go to the Thermal Model and navigate to Input Data >> Losses


The thermal circuit of the model will appear automatically when the calculation is completed. This circuit is a Lumped Parameter Thermal Network (LPTN). The definition of the symbols are shown below. More details of the circuit can be revealed by selecting the Detail tab.



Simple Transient Calculation

In the Thermal Model navigate to Calculation >> Calculation and select Transient for the calculation type.


Navigate to Calculation >> Transient and select Simple Transient for the transient calculation type.


Duty Cycle Transient Calculation







Coming Soon



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Post by David A. Giglio, PhD, PE
June 22, 2024