Abstract-Synchronous reluctance machines, including the permanent magnet assisted variants are competitive motor topologies if the application requires high efficiency and a cost effective solution with a high flux weakening capability. However, increasing operating speeds incur challenging design and development decisions, mainly in order to find design solutions that ensure the machines structural integrity without compromising the overall performance. In this paper, a comprehensive design procedure for high speed synchronous reluctance machines is presented. In order to validate the procedure, a 5 kW, 80000 rpm machine is considered. The proposed strategy consists of a two-step procedure in which the electromagnetic and structural designs have been properly decoupled dividing the design space in two subsets. Each subset mainly affects the electromagnetic or the structural performances. Several structural design optimizations have been then performed with the aim of finding the optimal trade-off between the rotor geometrical complexity (that defines the required computational resources) and the electromagnetic performance. The reported experimental tests of the prototyped machine validate the proposed design strategy which can be used as general guidelines on the structural design of synchronous reluctance machines.

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An important barrier to the adoption and acceptance of synchronous reluctance (SyR) machines in different applications lies in their non-standardized design procedure. The conflicting requirements incurring at high speeds among electromagnetic torque and structural and thermal limitations can significantly influence the machine performance, leading to a real design challenge. Analytical models used for design purpose lack in accuracy and force the designer to heavily rely on finite element analysis (FEA), at least during the design refinement stage. This becomes even more computationally expensive as the speed increases, as the evaluation of the rotor structural behaviour is required. This work presents a computationally efficient hybrid analytical-FE design process able to consider all the main limiting design aspects of SyR machine incurring at high speed, namely structural and thermal. As a vessel to investigate the proposed design routine accuracy, several high speed SyR machines have been designed for a wide range of operational speeds (up to 70krpm). The thermal and mechanical factors limiting the high speed operation are deeply analyzed aiming at maximize the mechanical output power. The proposed design approach is then validated by comparison against experimental measurements on a 5kW-50krpm SyR prototype. Index Terms-Analytical design, finite element analysis, high speed, iron bridges, iron losses, structural rotor design, synchronous reluctance machines.

In the last decade, the trend towards higher efficiency and higher torque density electrical machines without permanent magnets for industrial sector has rapidly increased. This work discusses the latest research and industrial advancements in Synchronous Reluctance machines (SynRM), being the emergent motor topology gaining wide acceptance by many industries. The paper 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 electrical machines 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 latest advancements with particular regards to the design methodology. This paper aims to provide a thorough overview to the research community and industry about SynRM. There is a clear potential for SynRM to take over significant portion of electrical machine market in the near future to meet efficiency standards in industrial applications without the use of rare-earth permanent magnet technology.