Numerical Multi-Phase Thermal Analysis to Determine End-Winding Heat Transfer Coefficient of an Interior Permanent Magnet Motor

Permanent magnet synchronous motors (PMSMs) are widely used in electrified vehicles due to their high-power density, high torque capability, high energy efficiency over a wide range of speed within a compact design. Thermal analysis is of primary importance for the design of an electric machine. Cooling mechanisms influence the machine's electromagnetic performance, durability, and reliability. Computational Fluid Dynamics (CFD) and Lumped Parameter Thermal Network (LPTN) are the most common techniques for analyzing thermal performance. Lumped parameter thermal networks (LPTNs) have proven to reduce the simulation time compared to computational fluid dynamics (CFD). However, implementing CFD simulations to calculate the heat transfer coefficients improves the accuracy of LPTN results. In this paper, a multi-phase oil splash CFD modeling was performed to determine the end-winding heat transfer coefficient using Ansys CFX, considering the rotational effect of the motor. The volume of fluid (VOF) and multiple reference frame (MRF) techniques are implemented.