How to calibrate the Motor-CAD thermal module with 2D-FEA?

It covers how to use the 2D FEA calibration mode, adjust cuboid settings, verify winding coverage, and fine-tune the effective radial K value. You’ll learn why the 2D model is used for validating radial and tangential heat transfer.

Motor-CAD offers a unique capability for electric motor thermal simulation, allowing users to evaluate various cooling methods within seconds. Using its template-based cooling models, Motor-CAD analytically calculates heat transfer coefficients, coolant flow rates, and pressure drops, which are then incorporated into the thermal circuit model. 

However, due to differences in motor geometries and custom cooling configurations, Motor-CAD may require calibration to ensure accurate results. To perform this, the built-in FEA model is used. 

To verify whether calibration is needed, navigate to the Thermal Calculation tab and change the Model Type to 2D Model (for FEA Calibration) under Steady-State Simulation. The 2D model is used because it excludes axial heat transfer, focusing instead on ensuring that the heat generation, as well as the radial and tangential heat transfer, are accurately represented and validated against the FEA model. Then, click “Solve Thermal Model” to compare and validate the FEA and circuit model results. 

Next, go to the FEA tab under the Temperature section and click “Solve Slot FEA” while the Stator area is selected. 

As shown in the figure above, the FEA and Model results differ significantly — 177°C for FEA and 322.9°C for the Model. Ideally, the Model results should be closely aligned with the FEA results, as the FEA provides a more accurate representation of the thermal behavior. 

Calibration Process 

To calibrate the model, there are three alternative steps you can follow: 

1. Cuboid Methods and Numbers

Based on your geometry, adjust the number of cuboids and the cuboid generation method to ensure that the cuboids fully cover the entire winding area in the following steps. 

Check whether the cuboids completely cover the winding area. If not, you can manually drag and expand the cuboids until the coverage is accurate. 

3.Manual Adjustment of Effective Radial K Value (Generally Not Required)

If a discrepancy between the FEA and Model results still exists after the previous steps, you can manually adjust the Effective Radial K value until both results align. 
This step is typically not required but can be used as a fine-tuning measure. 

Conclusion 

Run the 2D Model (FEA Calibration) and compare the results. Once the FEA and Model values closely match, you can switch back to the 3D Model and rely on the LPTN (Model) results for final thermal analysis.