A coupled rotor dynamic simulation of an electric drive train to investigate the acoustic behavior
Résumé
In order to improve the acoustic behavior of an electric drive train a holistic simulation approach is presented, that consider the interactions of structural mechanics and electrodynamics. The electromagnetic forces in the motor influence both the rotor dynamics and the structural vibrations and thus the sound radiation. Even small variations of the air gap lead to changes in the electrodynamic field, which cause a change in the resulting loads and therefore vibration excitation. Additionally load- and operation-dependent deformations of the stator and rotor are problematic. These influence the electrodynamically excited structural vibrations as well as the rotor dynamic loads. Therefore, it is necessary to consider the electro- and structural-dynamic effects together. In this study, the finite element method (FEM) is used to determine both the deformation of the structure and the electromagnetic forces. The forces, for instance as a function of the current rotor eccentricity, are used as excitation in a multi-body simulation (MBS) and thus allow the description of the structural vibrations, whereby bearings such as ball bearings or hydrodynamic bearings can be taken into account. The resulting vibrations influence the electrodynamic forces by changing the air gap. In addition the sound radiation of the vibrating structures is studied. To validate the results, a prototype of the electric motor will be analysed on a test bench. Subsequently, design measures can be evaluated based on possible improvements by means of parameter studies, without the necessity of real prototypes. The presented methodology is usable in a wide range of applications and not limited to the investigated engine.
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