Hybrid Numerical & Analytical Thermal Modeling of an Electric Traction Interior Permanent Magnet (IPM) Motor

Abstract

Permanent Magnet Synchronous Motors (PMSMs) have garnered widespread adoption in electric vehicles owing to their exceptional characteristics, including high power density, robust torque capability, and superior efficiency compared to conventional electric motors. Implementing permanent magnets facilitates the absence of a heat source on the rotor side, contributing significantly to their exceptional performance. However, despite these advantages, the heightened vulnerability of permanent magnets necessitates rigorous thermal management and analysis for PMSMs, particularly during short-duration peak performances and steady-state continuous operations. Operating under such conditions can potentially adversely affect the permanent magnets, winding insulation, and overall motor performance. Therefore, addressing thermal concerns associated with PMSMs emerges as a critical endeavor. This research tackles these thermal challenges by employing a combined approach of Lumped Parameter Thermal Network (LPTN) and Computational Fluid Dynamics (CFD) for accurate and cost-effective thermal modeling. A CFD analysis is performed to analyze the effect of water jacket and oil splash cooling and to calculate the heat transfer coefficients resulting from these two methodologies. A conjugate heat transfer CFD model is used to analyze the water jacket with the aid of a multi-phase CFD model to simulate the effect of the oil splash on end-windings. CFD heat transfer coefficients are then integrated into an LPTN model to calculate the temperature distribution of the motor. Furthermore, a comparative analysis is used to show the difference between integrating CFD-derived heat transfer coefficients and the analytical heat transfer coefficients in the LPTN model. VI In summary, this research underscores the importance of effective thermal management in maximizing the performance and longevity of PMSMs in electric vehicles. By leveraging advanced modeling methodologies, it seeks to address the intricate thermal concerns associated with PMSMs, paving the way for significant advancements in electric vehicle technology and inspiring sustainable transportation solutions.