Simulation Process for the Acoustical Excitation of DC-Link Film Capacitors in Highly Integrated Electrical Drivetrains

The advancing electrification of the powertrain is giving rise to new challenges in the field of acoustics. Film capacitors used in power electronics are a potential source of high-frequency interfering noise since they are exposed to voltage harmonics. These voltage harmonics are caused by semiconductor switching operations that are necessary to convert the DC voltage of the battery into three-phase alternating current for an electrical machine. In order to predict the acoustic characteristics of the DC-link capacitor at an early stage of development, a multiphysical chain of effects has to be addressed to consider electrical and mechanical influences. In this paper, a new method to evaluate the excitation amplitude of film capacitor windings is presented. The corresponding amplitudes are calculated via an analytical strain based on electromechanical couplings of the dielectric within film capacitors. These calculated deformation amplitudes can be used in an FE simulation by applying volumetric strains on capacitor windings. This allows the consideration of the structural dynamic properties of different capacitor geometries. In order to lower the computational costs, a substitute model based on substitute forces is also presented and validated. Thus, it is possible to adjust the operating strategy of the inverter to an optimal acoustic behavior by not having the resonance frequencies coincide with the PWM carrier frequency. In order to validate the excitation model, the result of the simulation is compared to vibrometer measurements. The proposed excitation model shows good agreement with the measurements and contributes to a better simulation quality of highly integrated power electronics, especially in the high-frequency range up to 14 kHz.