In low-to medium-power-rated brushless machines, noise of electromagnetic origin is generally prevailing over mechanical and aerodynamic sources. The appropriate combination of pole and slot of a permanent magnet synchronous motor is one of the keys to its performances among which stands noise reduction. This paper investigates configurations regarding this aspect for distributed overlapping and single-layer concentrated nonoverlapping winding configurations. Chosen combinations are 8 poles 48 slots (8p48s), 8p72s, 46p48s and 50p48s. The air-gap flux density is obtained by 2-D finite element analysis (FEA), allowing to compute the electromagnetic pressure. It then serves as input of mechanical and acoustical 3-D FEA models of the stator with carter.Index Terms-Acoustic noise, electromagnetic forces, finite element analysis (FEA), permanent magnet machines, vibrations.

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Abstract-This paper deals with the computation of vibrations and noise of electromagnetic origin for 'U'-shaped stator core flux switching permanent magnet (FSPM) machines. The investigation concerns a family of FSPM stator/rotor configurations with 12 slots and 10, 11, 13, and 14 rotor poles. More precisely, the study focuses on the influence of different number of rotor poles on the sound power level of U-core FSPM machines. Electromagnetic forces acting on the stator frame inner surface are calculated with the Maxwell stress tensor thanks to 2-D finite element (FE) simulations. The local magnetic force density serves then as a boundary condition to the 3-D finite element vibrational simulations of the whole stator frame with housing. Finally, obtained displacements help the authors to conduct the acoustic computations using a dedicated 3-D FE analysis model. The obtained vibro-acoustic spectra help electric machines designers to make appropriate choice of stator/rotor pole combination with respect to specifications at early stages of the design process.

Φ Abstract --Flux-Switching machines (FSM) have been gaining attention during the last decade. Their electromagnetic behavior has been extensively studied for various topologies, i.e. U-core and E-core, simple (wound field or PM) and hybrid excitations FSM machines. Even though noise and vibrations of electromagnetic origins can be important drawbacks, depending on the application, only few studies are analyzing these aspects. As a result, this paper aims at understanding the sound power level of U-core flux-switching permanent magnet (FSPM) machines whose rotors have different number of poles. The stator of the extensively studied 12/10 stator/rotor pole FSPM machine (12s10rp) serves as a basis for investigating 12s11rp, 12s13rp and 12s14rp configurations. Electromagnetic pressure is calculated from the Maxwell stress tensor where the magnetic flux density is obtained with 2-D finite element analysis (FEA). It then serves as input of a mechanical and acoustical 3-D FEA model of the stator with carter.