Acoustically Optimized Integration Concept Hybrid-Electric drive in Automotive Application

In this paper the noise of a gearbox integrated permanent magnet synchronous motor in hybrid application is investigated. Although electric drives tend to have low noise levels, the tonality and high frequency can lead to a low sound comfort level in premium passenger vehicles. In this paper, the electromagnetically excited radial structure modes are investigated and options for the decoupling of these modes evaluated. Using Maxwell stress in electro-magnetic FEM, the excitation forces acting in the air gap are calculated. These forces excite a linear structure model of the e-machine stator in mechanical FEM. The simulated integration of the e-machine into the gearbox housing is achieved via a stator frame. Improvements to the series configuration design are simulated and the most promising design is built up in hardware. Using this approach, the noise of the electric drive can be reduced significantly without changes in the electromagnetic design, control, performance and efficiency. Tests on an acoustic component test bench are used to validate the simulated level reduction in structure borne and airborne noise.