Forces and vibrations analysis in industrial PM motors having concentric windings

Industrial applications involving torque BLDC motors require high efficiency over a large speed range. In order to achieve such specifications, the flux weakening is necessary, which could lead to relative high mechanical vibrations and consequently to audible noise. Furthermore, to decrease cogging torque and to satisfy motor manufacturing constraints, concentric windings are usually considered. Such motor configurations lead to harmonics of the electromagnetic forces being the sources of mechanical vibrations. This paper focuses on the electromagnetic forces created in SMPM and IPM motors for two concentric windings: one and two coils per slot. These forces are determined using a lumped magnetic scheme and 2D FE simulations. 3D FE simulations permit to determine the mechanical modes and the acoustic power. The acoustic measurements confirm the analysis and the proposed improvement.