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- Modelo da característica magnética do gerador eléctrico de relutância comutado aplicado a conversores de energia eólicaPublication . Lobato, Pedro; Rafael, Silviano; Pires, A. J.
- Multi-machine topology versus monolithic switched reluctance machine in low speed applicationsPublication . Lobato, Pedro; Dente, J. A.; Martins, J. F.; Pires, A. J.In regards to SR machines design, there are a multiplicity of feasible topologies, differentiated by the properties of the electrical and magnetic circuits, and their relative location. A feasible SRG topology for an energy converter can comprise a series of n-SR machines assembled on a common axis. Comparing with a monolithic SR machine, that mono-axial multi-machine topology shows a higher fault tolerance and a simpler maintenance. The proposed scale models methodology makes it easy to incorporate in comparison of SR topologies other physical phenomena such as thermal effect and magnetic saturation by introducing some constraints. With the comparison of topologies, the issues surrounding the design of low speed SR multi-machine topology are discussed, leading into consideration monolithic topologies. The monolithic topology can optimize the efficiency taking benefits from the gain of power per unit of copper mass and lower losses.
- Field-Based Model for Switched Reluctance Generators in Direct Drive Wind Energy ConvertersPublication . Lobato, Pedro; Dente, J. A.; Pires, A. J.This work is motivated by the application of Switched Reluctance Generator (SRG) to direct-drive wind turbines and other low speed renewable energy systems. Direct drive energy converters take important benefits from the elimination of the gearbox, which has traditionally been used to interface a slowly prime mover shaft with the generator shaft. Moreover, the actual trend of exploiting the offshore wind resources makes robustness and reliability vital to the economic operation of wind turbines in that specific environment. The proposed field-based model with a triangular approach of the characteristics of flux-linkage makes it easy to incorporate magnetic saturation by introducing some constraints. With a specific aid of finite element analysis, the triangular approach of magnetic characteristics is used to make the comparison of SRG topologies a less time-consuming task. This work underlines dimensional and similarity arguments to extend previous discussions about SRG modeling into a more general context.
- Scale Models Formulation of Switched Reluctance Generators for Low Speed Energy ConvertersPublication . Lobato, Pedro; Dente, J. A.; Martins, J.; Pires, A. J.
- Analysis of wind energy production offshore in a scenario of extreme droughPublication . Santos, P. J.; Moreira, Sandrina Berthault; Pires, A. J.; Lobato, Pedro
- Similarity laws in low speed switched reluctance machines designPublication . Lobato, Pedro; Dente, J. A.; Martins, J. F.; Pires, A. J.This 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.
- Field-based models for low speed switched reluctance machine designsPublication . Lobato, Pedro; Dente, J. A.; Martins, J.F.; Pires, A. J.This paper presents a design assistance methodology of low speed Switched Reluctance Machines (SRM) using field-based models. The magnetic properties of the iron, the number of rotor poles, and the number of poles per phase, all play a significant role in the machine design. The proposed comparison procedure uses field-based models along with scale models, based on similarity laws, to compare SRM designs. The field-based models are here applied in dimensional analysis of regular and non-regular topologies distinguished by different characteristics of electric and magnetic circuits. As an added value for this methodology, similarity laws take into account physical phenomena like thermal changes and magnetic saturation. Hypotheses introduced in the methodology formulation were verified by finite element analysis. This work is motivated by the application of SRM to direct drive wind converters and other low speed renewable energy systems. As an application example of this methodology, a non-regular topology with short flux-paths was compared with a regular prototype, 3-phase, 12/16, SRM, designed for a direct drive wind turbine: a gain of power per unit of mass is achieved with the former one.