Acoustic noise calculation for high-speed permanent-magnet motors

The magnetically excited acoustic noise is calculated for three high-speed permanent-magnet motors with identical stators, but with different rotors. An analytical approach is used for the calculation of the magnetic radial forces. The components of the radial magnetic flux density in the middle of the air gap are determined with the help of finite element method (FEM) static calculations, which allow a decomposition of the air gap field into a Fourier series of flux density waves. The natural bending frequency is calculated using an analytical and alternatively a numerical calculation of a simplified mechanic model. The radial deformation of the stator yoke is calculated and the sound intensity level is calculated for the first 13 tonal frequencies and compared for the three motor configurations.