Three Dimensional Electromagnetic and NVH Analyses of Electric Motor Eccentricity to Enhance NVH Robustness for Hybrid and Electric Vehicles 2020-01-0412
Electric motor whine is one of the main noise sources of hybrid and electric vehicles. Motor air gap eccentricity due to prolusion system deflection, part tolerances and manufacturing variation is typically ignored in motor NVH design and analysis. Such eccentricity can be a dominant noise source by amplifying critical motor whine orders up to 10 dB, leading to poor NVH robustness. However, this problem cannot be explained by conventional method based on symmetric 2D approach.
New 3D electromagnetic (EM) and NVH analyses are developed and validated to accurately predict air gap induced motor noise to enhance NVH robustness: First, a true 3D full 360 deg electric motor model is developed to model asymmetric air gap distribution along motor stack length. Predicted 3D EM forces are then mapped to mechanical finite-element domain over the cylindrical stator surface. Furthermore, an enhanced 2.5D method is also developed that captures EM force variation along rotor stack length, which offers reasonable accuracy and reduced computational costs. Statistical analysis is performed to predict probability of motor air gap distribution considering tolerance stack and manufacturing variation. Motor shaft bending and housing deformation induced air gap eccentricity can also be analyzed to select structure design that offers most NVH robustness. The integrated 3D EM and NVH analyses successfully root caused and resolved eccentricity induced noise issues in a production hybrid electric vehicle (2-mode hybrid) and are used to enhance NVH robustness of GM’s hybrid and electric vehicles.
Song He, Peng Zhang, Michael Gandham, Bill Omell, Timothy Grewe, John Miller, Gautam GSJ