This conference paper was submitted for presentation at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

Meeting the sound quality requirements for an electric vehicle poses different challenges compared to vehicles with internal combustion engines. In an EV, the absence of engine noise does not allow to define a specific character to the vehicle. In addition, the reduced background noise at low speed may not mask the noise from accessories making them more noticeable. More importantly, the noise signature of an EV powertrain is completely different as the electric motor, the power control and the gearbox generate tonal noise and the tones are at high frequency and can then be perceived as more annoying. This paper investigates the electromagnetic performance, and NVH (Noise, Vibration, and Harshness) characteristics of a 48-slot/8-pole interior permanent magnet (IPM) motor specifically designed for automotive applications. Utilizing advanced virtual modelling and simulation techniques, the study conducts a comparative evaluation of rotor configurations with even and uneven magnetization under varying eccentricities '“ static, dynamic, and mixed. This methodology provides a comprehensive understanding of how magnetization variations affect motor behavior and force distribution within the motor. The forces are then used to load a structural finite-element model of the housing of the electric drivetrain unit supported on grounded mounts to predict the noise and vibration performance. The radial and tangential electromagnetic forces are applied on each stator tooth and the surface velocities of the housing are predicted to calculate the radiated noise at the fundamental and harmonic frequencies of the rotor angular velocity. The simulation process allows to optimize the design of the electric motor to balance the performance requirements and the noise radiation before building any prototype. In addition, the comparison of the radiated sound power for all the configurations simulated demonstrates the effect that uneven magnetization as well as rotor eccentricities can have on the noise and vibration performance of the electric drivetrain unit.