1,720,961 research outputs found
Structural design optimization of a high speed synchronous reluctance machine
No full textSynchronous reluctance machines, including the permanent magnet assisted variants are competitive motor topologies if the application requires high efficiency and a cost effective solution with a high flux weakening capability. However, increasing speeds incur challenging design and development decisions, in order to find an optimal solution between the machine performance and its structural integrity. In this paper, a comprehensive design procedure for such machines is presented, where a 5kW, 80000 rpm synchronous reluctance machine is considered. The proposed strategy consists of a two-step procedure in which the electromagnetic and structural designs have been properly decoupled dividing the design space in two subsets. Each subset mainly affects the electromagnetic or the structural performances. Several structural design optimizations have been performed with the aim of finding the optimal trade-off between the rotor geometrical complexity (i.e. computational time) and the electromagnetic performance. The results shown in this paper validate the proposed design strategy which can be used as general guidelines on the structural design of synchronous reluctance machines
High speed drives review: Machines, converters and applications
No full textThe development of new power electronic device and high performance magnetic materials are the main technological factors that have led both industries and research community to focus their attention on high speed electrical drives. Several papers have already outlined the electrical machine and/or converter topology choice for certain high speed application. This choice obviously depends on the applications under study. This paper aims to identify the most important high speed applications. For each of them, the main design challenges are highlighted and an overview of the already available product on the market is presented
Performance evaluation of converter topologies for high speed Starter/Generator in aircraft applications
No full textThis paper deals with the performance assessment of different permanent magnet motor drives topologies for Starter/Generator systems in aircraft applications. The comparison focuses on power electronics topologies, evaluating, by means of simulations performed with Matlab/Simulink and Plexim Plecs, some relevant key points such as efficiency, losses and motor current harmonic distortion. For all the topologies, simulations have been carried out considering both 2-Levels and 3-Levels converter structures, and different machine arrangements. All the power electronics systems data are obtained from off Tthe -shelf power modules characteristics, both Silicon and Silicon Carbide technology based. © 2014 IEEE
Converter topologies comparison for more electric aircrafts high speed Starter/Generator application
No full textThis paper deals with the performance assessment of different permanent magnet motor drives topologies for Starter/Generator in More Electric Aircraft systems. The comparison is focused on the power electronics part of the system, assuming the possibility to adapt the machine structure to better fit the specific configuration. Simulations performed with Matlab/Simulink and Plexim Plecs will be used to evaluate some relevant key points such as efficiency, losses and motor current harmonic distortion. For all the topologies taken into account, simulations will be carried out considering both 2-Levels and 3-Levels converter structures, and different machine arrangements. All power electronics related data used for simulations are obtained from the datasheets of off-the-shelf power modules, both Silicon and Silicon Carbide technology based. The topology showing the best compromise between efficiency and current THD is then selected and a prototype built and tested to validate the models used for simulations. © 2015 IEEE
IGBT-SiC dual fed ground power unit
No full textThis paper presents the design and control of a three-phase ground power supply unit for aircraft servicing. A new mixed technology converter composed by a three-phase Silicon Carbide (SiC) full bridge unit and a three-phase full bridge IGBT unit connected across the same dc link is used instead of the conventional full bridge configuration. In order to satisfy the stringent requirements of the output voltage quality particular attention is given to the controller. The common dc link topology of the converter allows circulation of Zero Sequence Current (ZSC), therefore also a 0 axis regulator is necessary. The state space model of the system considering the LC output filter is presented and used in order to synthetize the controller parameters using the Optimal Control theory. © 2017 IEEE
Zero-Sequence Voltage Elimination for Dual-Fed Common DC-Link Open-End Winding PMSM High-Speed Starter-Generator - Part I: Modulation
Full text link© 1972-2012 IEEE. In this paper, a dual-fed (DF) common dc-link topology open-end winding permanent magnet synchronous motor for aircraft high-speed starter-generator application is considered. While on one hand the common dc bus configuration significantly simplifies and reduces the costs of the topology, on the other hand it allows the zero-sequence current (ZSC) to flow freely in the system. High-speed machines are characterized by low phase inductance, which implies low zero-sequence impedance. A small time constant of the zero-sequence circuit produces a high-frequency, high-intensity ZSC ripple with the risk of harming the switching devices. This paper presents a novel hybrid space vector pulsewidth modulation that allows to instantaneously eliminate the zero-sequence voltage (ZSV) produced by the two voltage source converters (VSCs) by square wave modulating one of the two VSCs. The non-sinusoidal machine back electromotive force (EMF) has been considered and the effect of the converters' dead time on the ZSV has been analyzed. The square-wave-modulated VSC uses insulated-gate bipolar transistor (IGBT) devices, whereas the other uses Silicon Carbide (SiC) technology. The proposed topology is tested through both simulations and experiments
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Zero-sequence voltage elimination for dual fed common dc-link open-end winding PMSM high speed starter-generator, part II: dead time hysteresis control of zero sequence current
Full text linkIn a common dc link dual-fed Open-End Winding Permanent Magnet Synchronous Motor (OEW-PMSM) topology it is well known how the additional flow of a Zero-Sequence Current (ZSC) is permitted. The low Zero-Sequence Impedance (ZSI) characteristic of high speed machines leads to high intensity and high frequency ripple of the ZSC. Therefore there is the necessity to eliminate the Zero-Sequence-Voltage (ZSV) produced by the two Voltage Source Converters (VSCs) that feed the machine. Furthermore the non-sinusoidal back Electro Magnetic Force (back EMF) causes the circulation of a third harmonic ZSC. An OEW-PMSM high speed starter-generator fed by a dual-inverter with single dc link is considered. Part I of this work proposes a modulation for the considered topology able to eliminate instantaneously the ZSV produced. In this paper a detailed analysis of the Dead Time (DT) effect on the ZSV has been carried out and a novel hysteresis control for the ZSC using the DT as a control action is presented. The DT produces a ZSV distortion on the zero axis that can be used to control the third harmonic ZSC flowing due to the non-sinusoidal machine back EMF
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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