Magnetically Excited Acoustic Noise of Flux Switching Machines

The magnetically excited acoustic noise of high utilized Flux Switching Machines is already at no-load big due to the high radial air gap flux density amplitudes of up to 1.8 T. These amplitudes are necessary for a big torque/volume. They are generated by the magnet flux concentration arrangement. For a built 45 kW prototype with 430 Nm the measured no-load sound pressure level reached 95 dBA, which is 20 dBA above typical water-jacket cooled AC motors of this size. The exciting magnetic force wave orders and frequencies and the measured stator bending vibration modes are investigated to explain the resonant acoustic noise generation, also with inverter feeding and at motor load.