Mechanical Engineering
NOTICE OF SEMINAR PRESENTATION
CANDIDATE: Arthur Zajac
DEGREE SOUGHT: MASc
DATE: 5/13/2025
TIME: 11:30am
PLACE: Room 1102 CEI
TITLE: On the Impact of Rotor Core Surface Notches on Heat Transfer and Windage Losses for Automotive Electric Motor Traction Applications
Abstract
As hybrid and electric vehicles continue to grow in popularity, driven by increasingly stringent global emissions regulations and government policies, electric traction motors are becoming more powerful. This rise in performance however, brings with it increased heat generation, leading to a significant thermal management challenge. Inadequate machine cooling can lead to performance and efficiency degradation, damage or even total failure of the motor. While many OEMs and suppliers have transitioned from traditional air and/or water-glycol cooling to oil cooling, leveraging the dielectric properties of oils like automatic transmission fluid or transformers oil to directly cool the stator assembly, cooling the rotor remains a challenge. Permanent magnet synchronous motors (PMSMs), which currently dominate the automotive market, typically exhibit lower rotor losses than induction machines, which tends to make dedicated rotor cooling unnecessary. As motor outputs continue to rise, passive rotor cooling from the stator through the air gap may not be able to keep up, yet the complexity of dedicated rotor cooling is costly and difficult to package. This study investigates the novel repurposing of rotor notches, a commonly used feature for electromagnetic benefits (to reduce torque ripple and cogging torque) as passive thermal management devices. A large parametric sweep of various notch geometries and locations is conducted to better study the effect of the notches on the Nusselt number in the air gap as well as the expected increase in windage losses. Structural integrity of the modified laminations is also assessed to ensure mechanical feasibility. The results are compared to a commercial reference machine and have been validated against published experimental correlations. Additionally, electromagnetic performance is analyzed to assess the trade offs between thermal improvement and motor performance. This works aims to establish a practical path towards improving rotor cooling without added system complexity or cost.