Elliptical acoustic black hole applied to improve the NVH performance of permanent magnet motor

Abstract The permanent magnet motor offers high torque density, high stability and high energy conversion efficiency. However, the severe electromagnetic vibration generated during its operation can cause irreversible damage to its foundation. Therefore, it is necessary to reduce the vibrations transmitted to the foundation without affecting the motor’s operation, while also considering the limited available space on the motor and the weight constrains of the propulsion system. This paper proposes the application of an Elliptical Acoustic Black Hole (EABH) near the vibration isolator at the mounting foot to improve the noise vibration and harshness (NVH) performance of the permanent magnet motor. A numerical simulation of a permanent magnet motor was performed using finite element software to investigate the vibration level changes at the isolator under modal response and electromagnetic response, comparing the Original Vibration State (OVS) and the state with the Elliptical Acoustic Black Hole applied (ABHS). Above the cut-on frequency of 2.5 kHz, the EABH demonstrated broadband vibration damping capability. This was verified experimentally in the laboratory using the permanent magnet motor, where the vibration level at a single isolator was reduced by 2.7 dB under the action of three EABHs. Both simulation and experimental results demonstrate that the EABH structure employed in this study can effectively reduce the transmitted vibration level.