Analytical Prediction of Noise of Magnetic Origin Produced by Permanent Magnet Brushless Motors

Prediction of acoustic noise radiated by electric motors is nowadays important both for machine manufacturers and users. This paper describes an engineering approach to prediction of noise of magnetic origin produced by permanent magnet (PM) brushless motors. The sound power level (SWL) is calculated on the basis of magnetic field analysis in the air gap, radial forces, natural frequencies of the stator-frame system and radiation efficiency coefficient. Accuracy problems encountered in the analytical and numerical noise prediction have been discussed.