Browsing by Author "Costa, A.F."
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- An axial flux permanent magnet synchronous generator for a gearless wind energy systemPublication . Ferreira, Ângela P.; Silva, Amândio M.; Costa, A.F.In low speed applications such as wind energy conversion systems, the use of direct driven generators, instead of geared machines, reduces the number of drive components, which offers the opportunity to reduce costs and increases system reliability and efficiency. The Axial Flux Permanent Magnet (AFPM) generator is particularly suited for such application, since it can be designed with a large pole number and a high torque density. This paper presents the design, construction and experimental validation of a double-sided AFPM synchronous generator prototype, with internal rotor and slotted stators. Design objectives embrace achieving a good compromise between performance characteristics and feasibility of construction, which results in a cost competitive machine.
- Comprehensive analysis and evaluation of cogging torque in Axial Flux Permanent Magnet machinesPublication . Ferreira, Ângela P.; Leite, Vicente; Costa, A.F.Evaluation and minimization of cogging torque in Axial Flux Permanent Magnet (AFPM) machines become essential specially in direct drives for low speed applications. This paper presents a comprehensive analysis of the cogging torque in AFPM machines designed for low speed applications and mitigation methods are proposed. Evaluation methodologies of the cogging torque based on Finite Element Analysis (FEA) computations are discussed and applied to a double-sided, internal rotor, AFPM reference machine. From the performance comparison of Maxwell stress tensor and virtual work methods on the evaluation of cogging torque, it is possible to conclude that the latter overestimates the amplitude of the cogging torque into a considerable extent.
- Direct driven axial flux permanent magnet generator for small-scale wind power applicationsPublication . Ferreira, Ângela P.; Costa, A.F.The use of direct driven generators in small-scale wind power conversion systems, instead of geared machines, reduces the number of drive components, which offers the opportunity to reduce costs and increases system reliability and efficiency. For such applications, characterized by low speed of rotation, the axial flux permanent magnet generator is particularly suited, since it can be designed with a large pole number and high torque density.
- Direct driven axial flux permanent magnet generator for small-scale wind power applicationsPublication . Ferreira, Ângela P.; Costa, A.F.Small-scale wind power applications require a cost effective and mechanically simple generator in order to be a reliable energy source. The use of direct driven generators, instead of geared machines, reduces the number of drive components, which offers the opportunity to reduce costs and increases system reliability and efficiency. For such applications, characterized by low speed of rotation, the axial flux permanent magnet generator is particularly suited, since it can be designed with a large pole number and high torque density. This paper presents an axial flux permanent magnet synchronous generator, double sided with internal rotor and slotted stators. Such a structure gives a good compromise between performance characteristics and feasibility of construction. The design process of the machine is described and validated by test experiments.
- Efficient pole-arc coefficients for maximum no load flux linkage in axial flux permanent magnet machinesPublication . Ferreira, Ângela P.; Costa, A.F.This paper presents a comprehensive study towards the determination of efficient pole-arc coefficients for axial flux permanent magnet (PM) machines, through investigation of the contribution of volume elements of PMs to the no load flux linkage. The proposed methodology involves the evaluation of flux linkage using a mathematical expression which integrates a function over the volume of PMs instead of the classical integration of the magnetic flux density over the coil surface. The process is implemented using 2D finite element (FE) analysis, and the results shows the pole-arc coefficients that maximize the ratio of the flux linkage over the PM volume is between 0.5 and 0.6.
- Electromagnetic finite element design of axial flux permanent magnet machines for low speed applicationsPublication . Ferreira, Ângela P.; Costa, A.F.© 2014 IEEE. The higher torque to volume ratio of Axial Flux Permanent Magnet (AFPM) machines, when compared with their radial flux counterparts, is enhanced in multi pole design, making them suitable for low speed applications. This paper presents a comprehensive approach to the finite element-aided electromagnetic design of a double-sided AFPM machine with internal rotor. The Finite Element (FE) model is included in a coupled electromagnetic-thermal design procedure. Special attention is given to leakage fluxes, synchronous and armature reaction inductances and no-load electromotive force computation. The evaluation of the FE model routine of the design procedure is performed through experimental validation of a prototype machine.
- Materiais magnéticos permanentesPublication . Ferreira, Ângela P.; Costa, A.F.Os materiais magnéticos permanentes desempenham um papel preponderante numa vasta gama de produtos industriais e de consumo. O recente desenvolvimento dos ímanes de terras raras e a sua vulgarização introduziram alterações profundas nos dispositivos electromagnéticos e electrónicos com consequências no desempenho, tamanho e configuração, assim como na redução do custo dos produtos finais de uma forma que não era previsível há apenas 30 anos. A proliferação destes materiais tem ainda estimulado o desenvolvimento de novos produtos e mercados. Este trabalho constitui uma sinopse dos principais aspectos relacionados com os materiais magnéticos permanentes: é apresentada uma perspectiva histórica da sua evolução e uma compreensão básica da teoria do magnetismo. As tecnologias de fabrico e as principais classes de ímanes permanentes comerciais encerram a discussão.
- Projeto e seleção de materiais magnéticos permanentesPublication . Ferreira, Ângela P.; Costa, A.F.Os materiais magnéticos permanentes têm sido utilizados em dispositivos eletromagnéticos há mais de 100 anos mas, devido aos rogressos recentes das suas características magnéticas e a disponibilidade a custos acessíveis, a sua aplicação é atualmente transversal a uma vasta gama de áreas tecnológicas. A introdução dos ímanes de terras raras nos finais da década de 60 do século passado revolucionou a engenharia de projeto, conduzindo a uma reconfiguração dos dispositivos com fatores de escala anteriormente impraticáveis, elevando ainda o rendimento daqueles, ao eliminar as perdas associadas à criação de campos magnéticos baseados em densidades de correntes. Este trabalho descreve as principais classes dos materiais magnéticos permanentes com relevância comercial e fornece as linhas gerais do projeto magnético, com especial relevo para os materiais baseados em terras raras.
- Prototype of an axial flux permanent magnet generator for wind energy systems applicationsPublication . Ferreira, Ângela P.; Silva, Amândio M.; Costa, A.F.Small scale wind power applications require a cost effective and mechanically simple generator in order to be a reliable energy source. The use of direct driven generators, instead of geared machines, reduces the number of drive components, which offers the opportunity to reduce costs and increases system reliability and efficiency. For such applications, characterized by low speed of rotation, the axial flux permanent magnet generator is particularly suited, since it can be designed with a large pole number and high torque density. This paper presents a double-sided axial flux permanent magnet low-speed generator, with internal rotor and slotted stators. Such a structure gives a good compromise between performance characteristics and feasibility of construction. Test results obtained from the prototype are reported.
- Thermal analysis of an axial flux permanent magnet machinePublication . Ferreira, Ângela P.; Costa, A.F.Analytical lumped parameter circuits based on thermal resistances have been used extensively for calculation of the temperature rise in electrical machines. This work presents an analytical thermal equivalent circuit of an Axial Flux Permanent Magnet (AFPM) machine for steady state condition, used recursively with the electromagnetic design. From their interaction, the electrical loading has been adjusted, resulting in an increase of the output power compared to the initial pursued value.