Numerical investigation of the sound power and of the structural intensity of a permanent magnet synchronus machine

Noise and vibrations of electrical machines are getting more and more important. They are mainly caused by the magnetomotive force (MMF). In this paper the equivalent radiated power (ERP) of a prototype permanent magnet synchronous machine (PMSM) is calculated. The structural intensity (STI), which describes the energy flow of structure-borne sound, of the housing of the PMSM is obtained at a frequency where the ERP due to MMF is maximal. Considering the flux density and the flux direction of the STI the housing of the PMSM is modified in order to reduce the ERP. It is found that the location of an additional geometry feature - called patch - is essential for the effect on the ERP.