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Permanent magnet motors with rare earth magnets are amongst the best candidates for high performance applications such as automotive. However, due to their cost and risks relating to security of supply, alternative solutions such as ferrite magnets have recently become popular. In this paper the two major design challenges of using ferrite magnets for a high torque density and high speed application, namely their low remanent flux density and low coercivity, are addressed. It is shown that a spoke type design utilizing a distributed winding may overcome the torque density challenge due to a simultaneous flux concentration and reluctance torque possibility. Furthermore, the demagnetization challenge can be overcome through careful optimization of the rotor structure, with the inclusion of non-magnetic voids on the top and bottom of the magnets. To meet the challenges of the high speed operation an extensive rotor structural analysis has been undertaken, during which electro-magnetics as well as manufacturing tolerances are taken into account. The electromagnetic studies are validated through testing of a prototype, custom built for static torque and demagnetization evaluation. The disclosed motor design surpasses the state of the art performance and cost, merging the theories into a multi-disciplinary product.

This paper presents a comprehensive overview of the latest studies and analyses of the cooling technologies and computation methods for the automotive traction motors. Various cooling methods, including the natural, forced air, forced liquid and phase change types, are discussed with the pros and cons of each method being compared. The key factors for optimizing the heat transfer efficiency of each cooling system are highlighted here. Furthermore, the real life examples of these methods, applied in the latest automotive traction motor prototypes and products, have been set out and evaluated. Finally, the analytical and numerical techniques describing the nature and performance of different cooling schemes have been explained and addressed. This paper provides guidelines for selecting the appropriate cooling methods and estimating the performance of them in the early stages of their design. Index Terms-Automotive applications, cooling, traction motors, thermal analysis, numerical analysis. NOMENCLATURECross section area of heat path (m 2 ). , Linear current density (kA/m). , Inlet and outlet cross section areas (m 2 ). Specific heat capacity (J/kg). Diameter (m). , Friction loss factor (dimensionless). Gravitational attraction force (m/s 2 ). Grashof number (dimensionless). Fin extension (m). ℎHeat transfer coefficient (W/m 2 K). ℎLatent heat (kJ/kg). Loss coefficient (dimensionless).

Interior permanent magnet motors with ferrite magnets and distributed windings can be a cost effective alternative to rare-earth magnet based motors for demanding applications such as automotive traction. Among different rotor topologies, the spoke type may be preferred, due to its advantages for high flux concentration and resistance to demagnetization, when carefully designed. When high speed operation is required, to increase the power density of the motor, the spoke type rotor must comprise of two sections: a) the ferromagnetic rotor pole to provide the path for the magnetic flux, and b) the non-magnetic rotor support to provide the structural integrity. In this paper, the multiphysics and cost implications of the rotor support material, as part of a high performance ferrite magnet traction motor, are analyzed, and an optimal selection with respect to those criteria is proposed. The performance of the design based on the proposed rotor support material is validated by electromagnetic and structural testing of three sets of customized prototypes. Based on the analysis, the proposed rotor support material may, significantly, boost the cost competitiveness of a low cost ferrite motor for high volume production.

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Due to the volatility of the cost and sustainability concerns associated with the rare earth permanent magnets, alternative product designs using less or no rare earth contents have, recently, gained popularity. Another method to address this need is to apply a magnet recycling process, such as the novel HPMS (Hydrogen Processing of Magnetic Scrap) which can be applied to the end of life products such as Hard Drive Disks (HDDs). Despite the growing research on the background science of different recycling techniques, a practical make, use and evaluation of recycled magnets in a real life application, is rarely attended. To address this gap, in this paper and for the first time, the viability of the HPMS recycled magnets for use in a permanent magnet traction motor is investigated. On this basis, a detailed description and testing of the recycling process and the magnet production for a customized traction motor design is provided. Furthermore, the behavior of the motor using the final magnet product is analyzed using simulations and prototype testing. Based on the results, the proposed recycled magnets satisfy the overall requirements, while demonstrating similar or better electromagnetic performance compared to the alternative low cost ferrite magnets.

Permanent magnet motors with ferrite magnets may be applicable to demanding electric vehicle (EV) applications, provided that designs with high power density and efficiency, as well as high resistance to demagnetization are developed. One rotor topology that allows meeting those challenges is a design with a so-called spoke arrangement of the magnet poles. Although, a spoke type rotor topology is widely known, the influences of the rotor mechanical design on the electromagnetic performance has, largely, been overlooked, while a comparison of different feasible design solutions has not been provided to date. In this paper, a novel spoke type traction motor using ferrite magnets and based on a single piece rotor topology has been presented. The design is based on a coupled structuralelectromagnetic optimization, where the key design features, influencing the structural stress and the electromagnetic torque density have been explained. This design is, further, compared against a previously disclosed fir tree spoke type rotor solution, which has been designed for the same set of geometrical and output requirements. Through the comparisons, and for the first time, it is shown that the two alternative spoke type designs, show significant differences in performance, including torque density, efficiency, and demagnetization.

The Switched Reluctance Machine (SRM) offers advantages over other topologies, but low torque density, high torque ripple, and use of a non-standard power converter are limitations. This paper develops a drive configuration which facilitates the operation of a six-phase SRM using a standard three-phase inverter in order to address these limitations. The focus of the paper is an investigation of electromagnetic design aspects of two candidate SRM topologies in this six-phase context for a pure electric or hybrid electric vehicle type application. Advances are made in the understanding of the electromagnetic design of suitable SRMs, and the conventional SRM is demonstrated as the preferred topology through parametric and FEA design studies with reference to a given specification. Laboratory test results for a prototype machine are presented in verification of the machine design and demonstration of this drive concept as a high torque density candidate suitable for electric vehicle applications.