One of the key challenges for electric vehicle industry is to develop higher power density electric motors. Achieving higher power density requires efficient heat removal from inside the motor. Thus, electric motor thermal management has drawn particular attention in the past few years. In order to improve thermal management, a multi-physics modeling framework that is able to accurately predict the behavior of the motor, while being computationally efficient, is essential. This paper first presents a detailed validation of a Lumped Parameter Thermal Network (LPTN) model of an Internal Permanent Magnet (IPM) synchronous motor within the commercially available Motor-CAD modeling environment. The validation of the LPTN focuses on the stator, as the major thermal loss of an IPM motor occurs in this region. The IPM motor’s stator is studied at steady state and windings losses are generated by a constant DC current. The validation is based on temperature comparisons with experimental data provided by thermal testing of the studied IPM motor’s stator, as well as a comparison with a more detailed Finite Element Analysis (FEA) of the same IPM motor’s stator. All critical input parameters of the LPTN are considered in detail for each layer of the stator, especially the contact resistances between impregnation, liner, laminations and housing. Finally, a sensitivity analysis for each of the critical input parameters is provided. The temperature predictions from the LPTN are compared to the FEA model, as well as experimental data.  A maximum variation of 4% for the highest temperature in slot windings and end windings was found between the LPTN and the experimental data. Comparing the LPTN and the FEA model, the maximum variation was 2% for the highest temperature in slot windings and end windings. These close comparisons lead us to conclude that the LPTN can replace a FEA model for satisfactory thermal modeling of an IPM motor, allowing for faster iterations on the motor thermal design. As for the LTPN sensitivity analysis, the two main critical parameters which account for the highest sensitivity in the LTPN temperature outputs were found to be the stator lamination to housing contact resistance, and the liner to lamination contact resistance. The latter is often ignored in the literature, whereas its impact on temperature rise was found to be as significant as the stator to housing contact resistance.


Validation and Parametric Investigations Using a Lumped Thermal Parameter Model of an Internal Permanent Magnet Motor

Division / Sponsors: 
Electronic & Photonic Packaging Division (EPPD)

Paper Proceedings: https://asmedigitalcollection.asme.org/InterPACK/InterPACK2020/volume/84041

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