This paper presents the potential contribution of segmented stator magnetic circuits of rotating permanent magnets electrical machines with concentric winding. Two magnetic materials are mixed, FeSi Non-Oriented Electrical Steel (NOES) and FeSi Grain Oriented Electrical Steel (GOES). The choice of using GOES is based on the high performance it offers in terms of permeability and iron losses compared to conventional NOES, particularly when GOES is magnetised in the Rolling Direction (RD). The goal is to analyse the contribution of the mixed magnetic circuit on the losses and electromagnetic torque, but also the drawbacks due to the cut process and to the assembly. The behaviour of the magnetic field at the junction between the segments is studied by comparing different geometrical connection shapes and compared to a reference magnetic circuit fully made with NOES sheets. This comparison is experimentally made with a model representative of the existing phenomena in an electrical machine. In addition, numerical calculations using finite elements software are carried out, by considering both the magnetic anisotropy and the saturation of the GOES.

Grain Oriented Electrical Steel (GOES) have better performance in terms of permeability and iron losses compared to conventional Fe-Si 3% Non-Oriented Grains Electrical Steel (NOES), particularly when it is magnetized in the rolling direction. This paper presents a concentrated winding radial flux permanent magnets synchronous machine (PMSM) equipped with teeth made of GOES sheet. The goal is to assess the suitability of the use of GOES sheets to improve the efficiency of electric motors. This work is based on the comparison of the performances (Joule losses, iron losses, losses in the permanent magnets and efficiency) of two iso-geometric motors: a reference motor made of NOES sheets and a motor with teeth made of GOES sheets, at iso-torque and over the operating range (at constant torque and flux weakening). The comparison is made using a finite element software application considering the magnetic anisotropy of the GOES sheets.

Purpose The purpose of this paper is to exploit the optimal performances of each magnetic material in terms of low iron losses and high saturation flux density to improve the efficiency and the power density of the selected motor. Design/methodology/approach This paper presents a study to improve the power density and efficiency of e-motors for electric traction applications with high operating speed. The studied machine is a yokeless-stator axial flux permanent magnet synchronous motor with a dual rotor. The methodology consists in using different magnetic materials for an optimal design of the stator and rotor magnetic circuits to improve the motor performance. The candidate magnetic materials, adapted to the constraints of e-mobility, are made of thin laminations of Si-Fe nonoriented grain electrical steel, Si-Fe grain-oriented electrical steel (GOES) and iron-cobalt Permendur electrical steel (Co-Fe). Findings The mixed GOES-Co-Fe structure allows to reach 10 kW/kg in rated power density and a high efficiency in city driving conditions. This structure allows to make the powertrain less energy consuming in the battery electric vehicles and to reduce CO2 emissions in hybrid electric vehicles. Originality/value The originality of this study lies in the improvement of both power density and efficiency of the electric motor in automotive application by using different magnetic materials through a multiobjective optimization.

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