Enhancing interior noise of electric vehicles by design analyses and refinements of traction motors

Without thorough acoustic consideration, traction motorsâ–”the core of electric powertrainsâ–”may emit annoying whining noise during operation and deteriorate the interior noise of electric vehicles (EVs). To minimize such whining noise from traction motors, this article presents the interior noise developments of EVs which include the overview of acoustic sources, noise benchmark, noise paths investigation, multi-physics coupled analyses, design refinement and acoustic validation. Based on a developing EV, this study investigated on crucial mechatronic design of the traction motor in detail. By benchmarking, general interior noise levels of EVs were obtained and the target for acoustic refinement of the EV studied was defined. Noise and vibration measurements of the original EV and its associated traction motor identified the harmonics of electromagnetic forces from original traction motor were the root cause of whining noise concern. Noise paths assessment further identified the right mount of original traction motor being a critical structureborne path. Through refining the motor structure, simulated natural frequencies of the modified motor were 16â–“33% higher than those of original motor for the first four modes, and the vibration of modified motor was reduced accordingly. The mechatronic analysis further concluded the inappropriate pole and slot combination of original traction motor caused high electromagnetic forces. By optimizing mechatronic design for the modified traction motor, the interior noise level of modified EV was reduced dramatically with a maximum noise reduction of 16 dB. In addition, the modified EV achieved a 9.6 dB legislative pass-by noise reduction against that of original EV. By providing the comprehensive interior noise developments of EVs and illustrating the details of the acoustic design analyses and refinements of traction motors, this article can serve as a reference of acoustic design and development for other EVs and electric powertrains.