C-Core switched reluctance generator : constructive and operational aspects

Orientadores: Ernesto Ruppert Filho, Tárcio André dos Santos BarrosTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: O gerador de relutância variável (GRV) é considerado uma alternativa competitiva às máquinas elétricas convencionais utilizadas para a produção de energia elétrica a partir da energia eólica em aplicações de pequeno e médio portes. Entre os tipos construtivos dessa máquina elétrica, destaca-se a de fluxo magnético axial com núcleo do tipo C (GRV-C) que é abordada nesta pesquisa. Esta tese apresenta uma proposta de metodologia para o projeto eletromagnético de geradores de relutância variável de fluxo magnético axial com núcleo do tipo C e realiza análises estáticas e dinâmicas da sua operação em modo autoexcitado. O GRV-C é um tipo de gerador de relutância variável não convencional sendo que a maioria das pesquisas realizadas com o GRV focam nas estruturas tradicionais (estruturas regulares e de fluxo radial). Desta forma, este trabalho complementa a literatura, apresentando considerações sobre os dimensionamentos elétrico e magnético do GRV-C de pequeno e médio portes. A metodologia proposta foca diferentes aspectos. Primeiramente, as dimensões de um projeto inicial do núcleo eletromagnético são calculadas por meio de equações analíticas e de considerações baseadas em projetos de máquinas de relutância convencionais. Na sequência, um modelo usando o método dos elementos finitos em duas dimensões (MEF-2D) é utilizado no processo de otimização dos projetos elétrico e magnético. Optou-se pelo MEF-2D no processo de otimização dos parâmetros construtivos a fim de reduzir o tempo de processamento, quando comparado ao método dos elementos finitos em três dimensões (MEF-3D). Foi necessário inserir fatores de correção no modelo em duas dimensões. A análise da operação do GRV-C realizada nesta pesquisa é distinta das encontradas na literatura. Ela apresenta estudos comparativos entre três projetos de geradores obtidos a partir da metodologia proposta. Simulações estáticas e dinâmicas foram realizadas por meio de dois modelos diferentes: um usando o método dos elementos finitos e o outro baseado nas curvas de magnetização do gerador que representam bem as não linearidades magnéticas do gerador elétrico. Seguindo a metodologia de projeto proposta, foram obtidas as dimensões de um quarto gerador (utilizando o material magnético o disponível na empresa responsável pela fabricação) e o protótipo de um dos núcleos C foi construído a fim determinar os resultados estáticos experimentais. Os resultados de simulação e experimentais obtidos atestam a viabilidade e eficiência da metodologia proposta para o projeto de um GRV-CAbstract: The switched reluctance generator (SRG) is considered a competitive alternative to traditional electric machines used in wind energy systems for electric power generation for small and medium power applications. Prominent among the topologies of these electric machines is the Axial-Flux Switched Reluctance Generator with C Core (C-SRG) that is addressed in this research. This thesis presents a methodology proposal for the electromagnetic design of the Axial-Flux Switched Reluctance Generator with C Core and performs statics and dynamics analysis in self-exciting operation mode. The C-SRG is a non-conventional type of the switched reluctance generator and most research focuses on traditional structures of SRG (regular with the radial flux). So, this research supplements the literature, addressing a comprehensive framework of the electric and magnetic design of the C-SRG for small and medium power requirement. The proposed methodology focuses on different aspects. First, the dimensions of one initial design are obtained from analytic equations and design considerations based on traditional switched reluctance machines. After, a two-dimensional finite element method (FEM-2D) model is used to optimize the constructive parameters. The FEM-2D was chosen due to the high processing time during the optimization process when compared to three-dimensional finite element method (FEM-3D) model. However, it was necessary to include correction factors to calculate the inductances of the C-SRG model. The thesis C-SRG operations analysis is distinct from similar studies. It presents the comparative of three C-SRGs designs that were obtained from the proposed methodology. The static and dynamic simulations use two different models: one based on finite element method and the other on the generator¿s magnetization curves that well represents the magnetic nonlinearities of the electric generator. From the proposed design methodology, the final dimensions of a fourth generator are obtained (using the magnetic material available in the company responsible of the manufacturing) and an C-core prototype of the generator was built in order to obtain its experimental static results. The simulated and experimental results attested the viability and efficiency of the proposed methodology on the C-SRG designDoutoradoEnergia EletricaDoutora em Engenharia Elétric

SRM drives for electric traction

"GAECE" -- PortadaDescripció del recurs: 11 maig 2020GAECE (Grup d’accionaments elèctrics amb commutació electrònica). The group of electronically commutated electrical drives is a research team of Universitat Politècnica de Catalunya (UPC BARCELONATECH), which conducts investigation in four areas: electrical drives, power electronics, mechanics and energy and sustainability. Regarding electrical drives, research focuses on the development of new reluctance, permanent magnet and hybrid electrical drives. The main goal of those electrical drives is the integration of the power converter/controller and the mechanical transmission, being specially intended for the traction of light electric vehicles. That research is carried out by using the analysis of finite elements, taking into account eco-design criteria, considering new materials and new control strategies.First editio

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

Similarity laws in low speed switched reluctance machines design

Trabalho apresentado no 52nd International Universities' Power Engineering Conference, 28-31 agosto de 2017, Heraklion, Creta, GréciaThis paper presents a set of similarity laws appropriate for low speed switched reluctance machines design. Design methodologies of switched reluctance machines for low speed applications are generally oriented towards the choice of suitable combinations of stator and rotor poles in regular topologies. The proposed similarity laws provide an easy-to-use and robust methodology to compare different magnetic topologies, regular or non-regular, and have the capability to incorporate thermal and magnetic saturation phenomena by introducing constraints. With the assistance of finite-element analysis the issues surrounding the design of low speed SR multimachines topologies are discussed, leading into consideration of modular non-regular topologies. Using similarity laws, the modular topology is compared with a regular switched reluctance machine. The comparison results point out the reduction of copper losses of the modular topology over the regular topology. This paper extends previous discussions of switched machine design into a more general context.N/

A Review of Transverse Flux Machines Topologies and Design

High torque and power density are unique merits of transverse flux machines (TFMs). TFMs are particularly suitable for use in direct-drive systems, that is, those power systems with no gearbox between the electric machine and the prime mover or load. Variable speed wind turbines and in-wheel traction seem to be great-potential applications for TFMs. Nevertheless, the cogging torque, efficiency, power factor and manufacturing of TFMs should still be improved. In this paper, a comprehensive review of TFMs topologies and design is made, dealing with TFM applications, topologies, operation, design and modeling

Design and Development of Low Torque Ripple Variable-Speed Drive System With Six-Phase Switched Reluctance Motors

Switched reluctance motor (SRM) drives conventionally use current control techniques at low speed and voltage control techniques at high speed. However, these conventional methods usually fail to restrain the torque ripple, which is normally associated with this type of machine. Compared with conventional three-phase SRMs, higher phase SRMs have the advantage of lower torque ripple: To further reduce their torque ripple, this paper presents a control method for torque ripple reduction in six-phase SRM drives. A constant instantaneous torque is obtained by regulating the rotational speed of the stator flux linkage. This torque control method is subsequently developed for a conventional converter and a proposed novel converter with fewer switching devices. Moreover, modeling and simulation of this six-phase SRM drive system has been conducted in detail and validated experimentally using a 4.0-kW six-phase SRM drive system. Test results demonstrate that the proposed torque control method has outstanding performance of restraining the torque ripple with both converters for the six-phase SRM, showing superior performance to the conventional control techniques

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

Magnetic Material Modelling of Electrical Machines

The need for electromechanical energy conversion that takes place in electric motors, generators, and actuators is an important aspect associated with current development. The efficiency and effectiveness of the conversion process depends on both the design of the devices and the materials used in those devices. In this context, this book addresses important aspects of electrical machines, namely their materials, design, and optimization. It is essential for the design process of electrical machines to be carried out through extensive numerical field computations. Thus, the reprint also focuses on the accuracy of these computations, as well as the quality of the material models that are adopted. Another aspect of interest is the modeling of properties such as hysteresis, alternating and rotating losses and demagnetization. In addition, the characterization of materials and their dependence on mechanical quantities such as stresses and temperature are also considered. The reprint also addresses another aspect that needs to be considered for the development of the optimal global system in some applications, which is the case of drives that are associated with electrical machines

Design of Outrunner Eectric Machines for Green Energy Applications

Interests in using rare-earth free motors such as switched reluctance motors (SRMs) for electric and hybrid electric vehicles (EV/HEVs) continue to gain popularity, owing to their low cost and robustness. Optimal design of an SRM, to meet specific characteristics for an application, should involve simultaneous optimization of the motor geometry and control in order to achieve the highest performance with the lowest cost. This dissertation firstly presents a constrained multi-objective optimization framework for design and control of a SRM based on a non-dominated sorting genetic algorithm II (NSGA-II). The proposed methodology optimizes SRM operation for high volume traction applications by considering multiple criteria including efficiency, average torque, and torque ripple. Several constraints are defined by the application considered, such as the motor stack length, minimum desired efficiency, etc. The outcome of this optimization includes an optimal geometry, outlining variables such as air gap length, rotor inner diameter, stator pole arc angle, etc as well as optimal turn-on and turn-off firing angles. Then the machine is manufactured according to the obtained optimal specifications. Finite element analysis (FEA) and experimental results are provided to validate the theoretical findings. A solution for exploring optimal firing angles of nonlinear current-controlled SRMs is proposed in order to minimize the torque ripple. Motor torque ripple for a certain electrical load requirement is minimized using a surrogate-based optimization of firing angles by adjusting the motor geometry, reference current, rotor speed and dc bus voltage. Surrogate-based optimization is facilitated via Neural Networks (NN) which are regression tools capable of learning complex multi-variate functions. Flux and torque of the nonlinear SRM is learned as a function of input parameters, and consequently the computation time of design, which is crucial in any micro controller unit, is expedited by replacing the look-up tables of flux and torque with the surrogate NN model. This dissertation then proposes a framework for the design and analysis of a coreless permanent magnet (PM) machine for a 100 kWh shaft-less high strength steel flywheel energy storage system (SHFES). The PM motor/generator is designed to meet the required specs in terms of torque-speed and power-speed characteristics given by the application. The design challenges of a motor/generator for this architecture include: the poor flux paths due to a large scale solid carbon steel rotor and zero-thermal convection of the airgap due to operation of the machine in vacuum. Magnetic flux in this architecture tends to be 3-D rather than constrained due to lack of core in the stator. In order to tackle these challenges, several other parameters such as a proper number of magnets and slots combination, number of turns in each coil, magnets with high saturated flux density and magnets size are carefully considered in the proposed design framework. Magnetic levitation allows the use of a coreless stator that is placed on a supporting structure. The proposed PM motor/generator comprehensive geometry, electromagnetic and mechanical dimensioning are followed by detailed 3-D FEA. The torque, power, and speed determined by the FEA electromagnetic analysis are met by the application design requirements and constraints for both the charging and discharging modes of operation. Finally, the motor/generator static thermal analysis is discussed in order to validate the proposed cooling system functionality