This paper deals with the design of high-speed Synchronous Reluctance motors for electric vehicle applications. The need to enhance the power density and to lower the cost leads to research on high speed motors with a reduced amount of rare earth. Pure Synchronous Reluctance motors potentially operate at high speed and exhibit a cost-effective rotor compared to PM and induction motors. Nevertheless, they present reduced performances in deep flux weakening operations, in particular when the so-called radial ribs are introduced to increase the mechanical robustness of the rotor. In this paper the introduction of the radial ribs and the related design challenges are investigated and discussed. The adoption of the topology optimization tool that is able to optimize the amount, the positioning and the sizing of suitable structural ribs is presented. A design flow integrating the Topology Optimization is presented. The approach leads to an original positioning of the radial ribs able to preserve the performance of the motor at high operating speed enhancing the mechanical integrity of the rotor.

This article presents the definition of the performance that the electric motor should have in order to satisfy the requirements of the electric vehicle in terms of acceleration time and maximum speed, starting from a simplified vehicle model, considering the motor torque minimization and the input power minimization. In order to verify the effectiveness of the synchronous reluctance motor in traction applications, it has been evaluated in two case studies: a high-performance vehicle and a city car, where different flux weakening capabilities from the motor in function of the minimization strategies can be pursued to satisfy the requirements. If the car requires high performance in terms of acceleration time and maximum speed, the poor flux weakening capabilities of the synchronous reluctance motor induces a machine oversizing in terms of peak power; by assuming this, it is, however, possible to satisfy the requirements considering the maximum available encumbrance due to an advanced and innovative optimized design procedure. The motor of the city car is obtained only by modifying the stack length and the windings (scaled version), and on this last solution, a prototype has been realized and fully tested; the experimental tests confirm the results of the simulations.

This article deals with the design of a synchronous reluctance (SynRel) motor for full-electric vehicle applications. In particular, the design is focused on “premium” vehicles and aims at the development of rare-earth free electric motor technologies featuring low cost manufacturing. Different solutions are proposed and compared with focus on the rotor design; the investigated topologies employ asymmetric rotor structures with “fluid shaped” barriers without radial ribs to maximize the average torque and minimize the torque ripple. As this choice is very critical for the mechanical strength of the rotor core at high speed, it has been decided to fill the flux barriers with epoxy adhesive resin. The use of the resin requires accurate mechanical analysis in order to assess the rotor robustness at high speed. The article presents the performance of optimized designs without radial ribs and it is focused on the identification of the best properties for an epoxy resin able to enhance the mechanical integrity of the rotor. Moreover, experimental tests on resin cylinder samples have been carried out in order to verify the contact pressure between the resin and a laminated core. The results of this study could be a useful guideline for the designers interested in using this technology for high speed SynRel motors.

The Axial Flux Permanent Magnet (AFPM) motor represents a valid alternative to the traditional radial flux motor due to its compact structure; it is suitable for in-wheel applications so that the transmission gear can be suppressed. The modeling of the motor is a purely Three-Dimensional (3D) problem and the use of 3D finite element tools allows the attainment of accurate results taking also into account the effects of the end-windings. Moreover, a 3D multiphysics analysis is essential to evaluate not only the motor performance and its thermal behavior, but also the electromagnetic forces acting on the surfaces of the stator teeth and of the magnets that face the air gap. Moreover, as the vehicle’s motors often work in variable-speed conditions, the prediction of vibrations and noise for electric motors over a wide speed range is usually necessary. The paper presents a double-sided AFPM motor for a small pure electric vehicle; the basic drive architecture includes four axial flux motors installed directly inside the vehicle’s wheels. The aim is to propose advanced and integrated electromagnetic, vibroacoustic and thermal analyses that allow the investigation of the axial flux motor behavior in a detailed and exhaustive way.

The effects of manufacturing stresses on the overall magnetic properties of electrical steel core applied in the stator and transversally-laminated rotor of Synchronous Reluctance motors are studied. In addition, it is investigated how the -manufacturing-degraded electrical steel core affects the electromagnetic performance of two different Synchronous Reluctance motors. The traditional transversally-laminated rotor of this kind of a machine requires the adoption of mechanical elements (inner and tangential ribs) to maintain its mechanical integrity. Especially, for high-speed applications, the number of rotor ribs must be increased to make the rotor withstand higher centrifugal forces. Lamination manufacturing typically affects the magnetic properties of electrical steel by reducing its permeability at the machined edge. This machining effect is greater when the overall core layer area surrounded by the machined edges is small i.e. the machined surface area ratio to the total core area is high. Considering this, the degradation of the core magnetic properties in the ribs could improve the performance of the machine, and this effect would be more visible when the machine is designed with a higher number of narrow ribs with the adoption of Topology Optimization. The paper aims to propose some guidelines for the simulation of these effects starting from the measurements on defined core samples and then based on the measured results the simulation model should be updated accordingly. The samples are manufactured from several assembled sheets in order to modify the width of the cut area while maintaining the same external geometry.

The improvement of the robustness of the performance of electrical machines in presence of neglected features, such as manufacturing tolerances and deviations in material properties and parameters, is increasingly demanded. The available optimization procedures do not account for manufacturing tolerances, leaving the decision process incomplete. The paper proposes a methodology for the selection of the more robust design towards manufacturing tolerances among the best candidates, detected by an optimization procedure. Statistical tools for tolerance analysis and worst case analysis are discussed and adopted for the scope. The proposed methodology is used to select a robust design with respect to torque ripple deviations due to geometric tolerances in the laminations of a Synchronous Reluctance Motor with fluid shaped barriers. The statistical performance analysis and the worst-case analysis provide an estimation of the performance deterioration in the presence of the tolerances in the manufacturing process.