Analysis of power factor in variable flux reluctance machines with MMF-permeance model

This study investigates the underlying mechanism of low-power factor issue of variable flux reluctance machines (VFRMs) from the perspective of magneto-motive force (MMF)-permeance model. On the basis of a simplified analytical model, the relationship between the design parameters and the power factor is identified and systematically summarised into three predictable ratios: the rotor permeance ratio, stator/rotor-pole ratio and DC/AC winding ampere turns ratio. Specifically, the smaller the rotor-pole arc, the air-gap length, the rotor-pole number and the AC/DC winding ampere turns ratio are, the higher the power factor will be. In addition, the weak coupling between the field and armature windings caused by the modulation effect of the salient rotor is responsible for the low-power factor issue of VFRMs, regardless of the control scheme, winding configuration or saturation effect. A 6-stator-pole/4-rotor-pole VFRM is prototyped and tested for verification

Flux-adjustable permanent magnet machines in traction applications

This paper overviews the recent advances in flux-adjustable permanent magnet (PM) machines for traction applications. The flux-adjustable PM machines benefit from the synergies of the high torque density and high efficiency in conventional PM machines as well as the controllable air-gap field in wound-field machines, which are attractive for the traction applications requiring enhanced capabilities of speed regulation and uncontrolled voltage mitigation. In general, three solutions have been presented, namely the hybrid excited (HE), the mechanically regulated (MR), and the variable flux memory (VFM) machines. Numerous innovations were proposed on these topics during the last two decades, while each machine topology has its own merits and demerits. The purpose of this paper is to review the development history and trend of the flux-adjustable PM machines, with particular reference to their topologies, working mechanism, and electromagnetic performance

Modern Hybrid Excited Electric Machines

The paper deals with the overview of different designs of hybrid excited electrical machines, i.e., those with conventional permanent magnets excitation and additional DC-powered electromagnetic systems in the excitation circuit. The paper presents the most common topologies for this type of machines found in the literature—they were divided according to their electrical, mechanical and thermal properties. Against this background, the designs of hybrid excited machines that were the subject of scientific research of the authors are presented. Document type: Articl

Optimisation de la Conception du Moteur Synchrone à Excitation Hybride pour Véhicules Électriques à Haut Performance

Since 1970, the ever-growing concerns of human community for the life-threatening environmental changes have pushed the policy makers to decarbonize those sectors with high energy demands, including the transportation industry. Optimal designs of Electric Vehicles (EVs) can contribute to today’s exigent car market, and take the leading role for future sustainable transportation of human and goods. At the heart of electromechanical energy conversion lays the electrical machines, which have attracted lots of interests and efforts for efficiency increase and cost reduction. In this thesis, a methodology is proposed and implemented to design and optimize the cost and efficiency of a Hybrid Excitation Synchronous Machine (HESM) for a given vehicle and a desired driving cycle. Hybridization in the excitation system can combine the favorable qualities of high-torque at low-speed with superior overloading capability, exceptional flux weakening and extended Constant Power Speed Range (CPSR), high efficiency, and flexible controllability in motoring and generation modes. With HESM technology, we can also shift from the rare-earth magnets towards the cheap ferrite magnets and guaranty the supply for motor industry. The designed HESM in this work responds to three requirements of the vehicle, namely, the maximum cruising speed, acceleration time, and gradeability, with the least or null overdesign in the drivetrain. At the same time, it will have the maximum global efficiency over the driving cycle, and the minimum cost for the material. The optimization is conducted at either of the component and system levels. The optimization at component-level is developed based on the Non-dominated Sorting Genetic Algorithm-II (NSGA-II). A new formulation for the objective functions is proposed, which deals with the design optimization and cost minimization, simultaneously. To maximize the efficiency, a system-level search is conducted to find the optimum HESM with the highest global efficiency over a given driving cycle. Due to the 3D direction of magnetic flux in the selected HESM topology, the Finite Element Analysis (FEA) was very time- and process-consuming. To be able to evaluate the objective functions during the optimization, a new model has been developed based on a 3D Magnetic Equivalent Circuit (MEC) network. This model predicts well the non-linearity of magnetic materials, as compared with the FEA simulations. At last, the final optimized HESM is evaluated by the virtue of FEA technique.Depuis 1970, les préoccupations de l’humanité envers les changements climatiques ont poussé les chercheurs à faire des études approfondies pour optimiser les machines électriques pour avoir des véhicules électriques plus performants et moins énergivores. La conception optimale de véhicules électriques (EV) peut contribuer pour un marché automobile plus exigeant et jouer un rôle principal pour le futur du transport durable des biens et des personnes. Les machines électriques se trouvent au cœur de la conversion d'énergie électromécanique, qui ont suscité beaucoup d'intérêts et d’efforts pour augmenter leur rendement et réduire leur coût. Cette thèse propose une méthodologie et une mise en œuvre pour minimiser le coût et maximiser l’efficacité d’une machine synchrone à excitation hybride (HESM) pour un véhicule donné et un cycle de conduite sélectionné. L'hybridation du système d’excitation peut combiner les qualités favorables comme un couple élevé à basse vitesse avec une capacité de surcharge supérieure, un défluxage exceptionnelle et une plage de vitesse prolongée de puissance constante (CPSR), une efficacité élevée et une contrôlabilité flexible dans les modes de traction et de freinage régénératif. Avec la technologie HESM, nous pouvons également passer des aimants de terres rares aux aimants en ferrite bon marché, et garantir l’approvisionnement pour l’industrie automobile. Le HESM conçu dans ce travail répond à trois exigences du véhicule : la vitesse de croisière maximale, le temps d’accélération et la capacité de monter une pente, avec un surdimensionnement minimal ou nulle de la chaîne de traction. Une optimisation multiniveau avec une interaction entre la vision composant et la vision système est proposée et validée. L’optimisation au niveau du composant est développée sur la base de l’algorithme génétique de tri non dominé (NSGA-II). Une nouvelle formulation pour les fonctions objectives est proposée pour l’optimisation simultanée de la conception de la machine et de la minimisation de son coût. Après avoir optimisés onze HESM au niveau du composant, pour maximiser l’efficacité, une optimisation au niveau du système est réalisée pour trouver le HESM optimal avec le plus haut rendement global sur le cycle de conduite donné. Une validation de la conception finale de la HESM présente un meilleur rendement global sur le cycle de conduite de 18,65% en relation à une machine synchrone à excitation séparée équivalente et 15,8% en relation à une à aiment permanent. En raison de la direction 3D du flux magnétique dans la topologie HESM sélectionnée, l’analyse par éléments finis (FEA) prenait beaucoup de temps et de ressources computationnelles. Afin d’évaluer les fonctions objectives lors de l’optimisation, un nouveau modèle a été développé basé sur un réseau de circuits magnétiques équivalents 3D (MEC). Ce modèle prédit bien la non-linéarité des matériaux magnétiques, par rapport aux simulations FEA. Enfin, le HESM optimisé final est évalué grâce à la technique FEA

Design and Application of Electrical Machines

Electrical machines are one of the most important components of the industrial world. They are at the heart of the new industrial revolution, brought forth by the development of electromobility and renewable energy systems. Electric motors must meet the most stringent requirements of reliability, availability, and high efficiency in order, among other things, to match the useful lifetime of power electronics in complex system applications and compete in the market under ever-increasing pressure to deliver the highest performance criteria. Today, thanks to the application of highly efficient numerical algorithms running on high-performance computers, it is possible to design electric machines and very complex drive systems faster and at a lower cost. At the same time, progress in the field of material science and technology enables the development of increasingly complex motor designs and topologies. The purpose of this Special Issue is to contribute to this development of electric machines. The publication of this collection of scientific articles, dedicated to the topic of electric machine design and application, contributes to the dissemination of the above information among professionals dealing with electrical machines