In the last decade, the trend toward higher efficiency and higher torque density electrical machines (EMs) without permanent magnets (PMs) for the industrial sector has rapidly increased. This work discusses the latest research and industrial advancements in synchronous reluctance machines (SynRMs), being the emergent motor topology gaining wide acceptance by many industries. This article presents an extensive literature review covering the background and evolvement of SynRM, including the most recent developments. Nowadays, SynRM has found its niche in the EM market, and the reasons for that are highlighted in this work together with its advantages and disadvantages. The key journal publications in SynRM topics are discussed presenting the biggest challenges and the latest advancements with particular regards to the design methodology. This article aims to provide a thorough overview to the research community and industry about SynRM. There is a clear potential for SynRM to take over a significant portion of the EM market in the near future to meet efficiency standards in industrial applications without the use of rare-Earth PM technology.

Synchronous reluctance machines are becoming a widespread solution in many engineering areas thanks to their simple rotor structure, the absence of rare-earth permanent magnets and high efficiency. The design of such machines is a widely investigated research topic, given the challenge of analytically estimating their electromagnetic performance, especially when a high-speed scenario is considered. The design choices and assumptions, which include the selection of the magnetic load and the stator and rotor lamination materials, play an important role in the machine performance. Consequently, it is of paramount importance to assess their validity. This paper, after a brief re-call of a general design methodology able to consider all the magnetic non-linearities and structural and thermal limitations occurring at high-speed, presents a sensitivity analysis against the magnetic load when a Cobalt-based alloy is adopted for both stator and rotor laminations. The analysis is carried out for different speeds up to 90 krpm, in order to draw general design guidelines for a given outer envelope and cooling system.

Synchronous reluctance machines (SynRel) are becoming very attractive for different applications because of their reluctance nature, easy manufacturability and low cost. Their design still represents a challange because of the many degrees of freedom that their rotor structure presents. Furthermore, in order to obtain a design with defined electromagnetic characteristics and low torque ripple machine geometry is needed to be optimised. In this paper, three different optimisations are performed on 6 poles SynRel motor with three flux barriers per pole. The aim of the work is to show the effect of the objective selection on the optimization process. An automatic procedure has been applied coupling finite element analysis with an optimization algorithm that is working towards the competitive targets of maximazing the torque, while minimizing the torque ripple and losses. The effects of these objectives on the geometrical variables are investigated in detail. The outcome of the analysis show how the problem definition heavily affects the obtained results. This gives useful insights on how to approach SynRel rotor design.

The development of new power electronic device and high performance magnetic materials are the main technological factors that have led both industries and research community to focus their attention on high speed electrical drives. Several papers have already outlined the electrical machine and/or converter topology choice for certain high speed application. This choice obviously depends on the applications under study. This paper aims to identify the most important high speed applications. For each of them, the main design challenges are highlighted and an overview of the already available product on the market is presented.

This paper presents an extensive study on the electromagnetic and structural influences of the end barrier shape of a Synchronous Reluctance Machine (SynRel). One of the most challenging tasks in designing these machines is to achieve a smooth torque and a mechanically robust structure, especially when high operating speed range is required. Several papers have already addressed the electromagnetic design problem related to the choice of the flux barriers thicknesses and positions. However a comprehensive work on the influence of the end part of the flux barrier on the electromagnetic and structural performance has not been yet presented. In this work two end barrier shapes are considered and optimized using the same methodology. Then the optimized machines have been deeply analyzed in terms of torque, torque ripple and rotor von Mises stress distribution. Furthermore, with the aim to further investigate the influence of such end barrier shape, a detailed sensitivity analysis is presented. In conclusion, general guidelines for the structural and electromagnetic design of such end barrier shape are drawn.

This paper is focused on the electromagnetic and structural design of high-speed synchronous reluctance (HS-SyR) machines. Both design aspects are equally taken into account due to high speed requirements. Two design procedures, both based on multi-objectives stochastic optimization algorithms (OA) and Finite Element Analysis (FEA), are presented and compared in terms of computational time and quality of the final result. The first design procedure combines an electromagnetic FEA with an analytical rotor structural design. The second procedure evaluates both electromagnetic and structural performance using FEA simulations within the optimization. The former approach needs a structural refinement stage of the rotor geometry. The latter gives rotor designs ready for manufacturing at the cost of increased computational resources. The two approaches have been investigated considering the rotor design of an 80.000 rpm SyR motor for aeronautical applications. Finally, a sensitivity analysis has been performed to identify which variables most affect structural performance and which parameters need tighter manufacturing tolerances.