ENGINE MOUNTING SYSTEMS FOR ELECTRIC POWERTRAINS: MOUNTING LAYOUTS AND DESIGN PARAMETERS

The vibroacoustic characteristics of electric powertrains are well known to significantly differ from internal combustion engines. A relatively very high power-to-torque density makes a three-phase permanent-magnet synchronous motor (PMSM) very appealing for electric powertrains, but its electromagnetic characteristics typically result in high frequency noise and vibration. While the vibration response in internal combustion engines is generally evaluated up to 100 Hz, electric drive trains are known to exhibit a response ranging from 1 to 10 kHz. As a result, multiple studies in the recent literature have investigated several designs for engine mounting systems that could be used to address some of the specific issues such as internal resonances, wave effects, high frequency noise and vibration, etc. It has been widely reported in the literature that force transmissibility and noise radiation can be significantly underestimated at relatively higher frequencies without directly modeling the inertial properties of the engine mounting system. Some of the mounting system layouts that have been investigated in the literature include the three-point or four-point saddle mounting configurations, the cradle type pendulum mounting configuration, etc. This paper performs a comparative analysis for a few of the commonly used mounting system layouts to identify the pros and cons of the design strategies specifically aimed at vibration mitigation in electric powertrains. A spatial model that has been previously validated is used to compare three different mounting system layouts. Since viscoelastic properties are known to exhibit a strong influence from excitation frequencies, the spatial model that has been used in this study incorporates the properties that are associated with high frequency response of the engine mounting system. Force transmissibility plots are used to evaluate the mounting layouts and specific design parameters associated with the engine mounting system. Results indicate that the four-point saddle mounting configuration provides a good balance between transmissibility at low frequencies and high frequencies. Models presented in this study can be used to determine an optimal mounting configuration for an electric powertrain.