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

Flux-switching permanent magnet machine drive system for plug-in hybrid electrical vehicle

Plug-in hybrid electric vehicle (PHEV) depends mostly on the electric drive system where the internal combustion engine just acts as the auxiliary unit, which has strict constraints for the drive machine. According to the Toyota Prius configuration, one novel PHEV drive system in this paper has been brought forward which primarily includes one drive machine operating as both motor and generator, energy storage unit combining supercapacitor and battery. In the novel PHEV, the ideal tendency is to use the drive machine over the entire torque/speed range, including starting/acceleration, high speed cruising, regenerative braking, etc. The flux-switching permanent magnet machine (FSPMM) for the drive system has been studied in details. Firstly, the structure and operation principle are analyzed theoretically. In order to achieve higher torque/power density and lower torque ripple, FSPMM with 6/7 (stator/rotor) poles and 12/14 poles according to plenty of investigations are optimized based on our setting objective function decided by actual projects. Moreover, it analyzes several typical performance curves, such as cogging/rating torque, flux linkage, back-EMF, and self-/mutual-inductances. Finally the flux-weakening ability and efficiency are estimated by experience. The results indicate that FSPMM is one ideal candidate for our PHEV drive system for its strong thermal dissipation ability, good mechanical robustness, strong flux-weakening ability, etc

Design and Construction Modifications of Switched Reluctance Machines

Although the design principles of the Switched Reluctance Machines (SRMs) are available in different fragments in numerous bibliography positions, there no exists the complex design procedure of whole drive system taking into account the SR Machine, control system and supply device as well. The hybrid design method for SRM drives with application of new analytical calculation methods, finite element method and simulation models is proposed in this thesis. The calculation/design system is characterised by important effectivity and reliability. The new possibilities in analytical determination of saturation effects and core losses under various modes of control, including sensorless method, are also taken into account. The correctness of the proposed design algorithms are verified by laboratory tests made on three motor prototypes manufactured in industry for concrete application. This dissertation provides the elements indispensable for more accurate and complex analysis and design of drives with switch reluctance motors. The elements of electrical motor and control system design as well as the considerations on the choice of supply device and controller subsystems are jointed in the thesis for final receiving of the design tool for considered industrial drive system

A novel modular stator hybrid-excited doubly salient synchronous machine with stator slot permanent magnets

This paper presents a novel modular stator hybrid-excited synchronous machine with stator slot permanent magnets (PMs). By regulating the field current, the magnetic field, and consequently the back electromotive force, as well as the average torque can be controlled. The existence of stator slot PMs alleviates the magnetic saturation and improves the flux regulation ratio. The frozen permeability method is employed to investigate the torque contributions by different magnetic sources. Possible stator and rotor pole combinations are illustrated, and the corresponding electromagnetic performances are evaluated with the finite-element method. It is revealed that 12-stator pole machines with 11- and 13-rotor poles exhibit superior average torque and lower torque ripple due to even-order harmonics elimination. Finally, a prototype with modular stator segments is manufactured to validate the analyses and simulations

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

Investigation of novel multi-layer spoke-type ferrite interior permanent magnet machines

The permanent magnet synchronous machines have been attracting more and more attention due to the advantages of high torque density, outstanding efficiency and maturing technologies. Under the urges of mandatory energy efficiency requirements, they are considered as the most potential candidates to replace the comparatively low-efficient induction machines which dominate the industrial market. However, most of the high performance permanent magnet machines are based on high cost rare-earth materials. Thus, there will be huge demands for low-cost high-performance permanent magnet machines. Ferrite magnet is inexpensive and abundant in supply, and is considered as the most promising alternative to achieve the goal of low cost and high performance. In consideration of the low magnetic energy, this thesis explored the recent developments and possible ideas of ferrite machines, and proposed a novel multi-layer spoke-type interior permanent magnet configuration combining the advantages of flux focusing technique and multi-layer structure. With comparable material cost to induction machines, the proposed ferrite magnet design could deliver 27% higher power with 2-4% higher efficiency with exactly the same frame size. Based on the data base of International Energy Agency (IEA), electricity consumed by electric machines reached 7.1PWh in 2006 [1]. Considering that induction machines take up 90% of the overall industrial installation, the potential energy savings is enormous. This thesis contributes in five key aspects towards the investigation and design of low-cost high-performance ferrite permanent magnet machines. Firstly, accurate analytical models for the multi-layer configurations were developed with the consideration of spatial harmonics, and provided effective yet simple way for preliminary design. Secondly, the influence of key design parameters on performance of the multi-layer ferrite machines were comprehensively investigated, and optimal design could be carried out based on the insightful knowledge revealed. Thirdly, systematic investigation of the demagnetization mechanism was carried out, focusing on the three key factors: armature MMF, intrinsic coercivity and working temperature. Anti-demagnetization designs were presented accordingly to reduce the risk of performance degradation and guarantee the safe operation under various loading conditions. Then, comparative study was carried out with a commercial induction machine for verification of the superior performance of the proposed ferrite machine. Without loss of generality, the two machines had identical stator cores, same rotor diameter and stacking length. Under the operating condition of same stator copper loss, the results confirmed the superior performance of the ferrite machine in terms of torque density, power factor and efficiency. Lastly, mechanical design was discussed to reduce the cost of mass production, and the experimental effort on the prototype machine validates the advantageous performance as well as the analytical and FEA predictions

Design of a high speed high power switched reluctance motor

PhD ThesisAn increase in the price of rare earth materials in 2009 prompted research into alternative motor technologies without permanent magnets. The SRMs have become more of an attractive solution as they are relatively simpler to construct than other machines technologies hence cost effective. Furthermore, the rugged structure of the rotor makes it suitable for high speed operation, if appropriately designed. This thesis investigates the design, analysis and prototype manufacture of an SRM, that from electromagnetic point of view, meets the power output of the PM machine used in the Toyota Prius, although operating at a higher speed of 50,000 rpm. As a result, the required torque is considerably less than an equivalent motor with the same output power running at lower speed, hence this approach allows for much smaller frame sizes. To achieve the required torque, careful choice of stator/rotor tooth combination, coil number of turns and number of phases is needed. Running at high speed, increases the AC copper loss (consisting of skin effect and proximity effects) and iron loss. These shortcomings are extensively discussed and investigated. The mechanical design of this motor requires careful consideration in order to minimise the high mechanical stresses acting upon the rotor, which are due to the high radial forces caused by the centripetal force at high speed. In order to address the mechanical constraints caused by the hoop stress, a structure common to flywheels is applied to the rotor. In this approach, the shaft bore is removed and the laminations are sandwiched together using cheek plates, which are secured using tie rods. The cheek plates have their extending shafts, which consequently will transfer the torque to the rest of the system. The proposed model is analysed for both the electromagnetic and mechanical aspects, successfully demonstrating a promising rotor topology for the design speed. A high speed motor design needs to take into account shaft design, rotor design and bearing design. The high speed operation of the salient rotor gives dramatic rise to the windage loss. These factors are carefully considered in this work and the results are presented

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