1,720,984 research outputs found
Advancements in Control, Design, and Parameter Identification of Permanent Magnet Synchronous Machines
Full text linkIn this work, advancements in control, design, and parameter identification of permanent magnet synchronous machines (PMSMs) are presented. These advancements take up opportunities and challenges offered by novel applications and technologies. In fact, PMSMs are increasingly adopted thanks to high efficiency and versatility, covering a wide range of applications. In particular, the use of PMSMs in the industry of small-scale wind turbines is becoming dominant. In this application, direct drive topologies coupled with variable speed and fixed pitch wind turbines are a promising solution because of their simplicity, efficiency, and reliability. In fact, this solution avoids the use of gearboxes and mechanical systems for the control of the pitch angle, reducing losses, costs, and failure risks. In this architecture, the aerodynamic power regulation is entirely entrusted to the control of the permanent magnet synchronous generator (PMSG). While several methods have been developed to achieve the maximum power point tracking, poor effort has been made to regulate the power for wind speeds above the rated one. In this work, this challenge
has been addressed by proposing an innovative control scheme in which an aerodynamic torque observer and a wind speed estimator are involved. The aim of the designed solution is to achieve the maximum power point tracking for wind speeds below the rated one and to extend the power generation in the high wind speed region. In this region, the respect of the safety mechanical limits of the system is the crucial issue. The proposed control scheme has been tested on an experimental setup in the laboratory of Electrical Machines and Drives of the Politecnico di Bari. The achieved results show that the reference power regulation characteristic has been tracked with a good accuracy covering the whole wind speed range of the system. In the context of the design of PMSMs, novel modular topologies are gaining increasing interest, especially in applications where large machines are employed. Thanks to this technology, several advantages in the manufacturing, transporting, and assembling over conventional PMSMs can be achieved. A drawback of PMSMs with modular stators is the presence of additional harmonic
components of the cogging torque, with higher amplitudes and lower frequencies than the ones of PMSMs with a one-piece stator. The minimization of these harmonics is essential to increase the control accuracy and reduce undesired noise and vibrations. Despite several methods have been developed for the cogging torque minimization, these mostly deal with conventional PMSMs. In this work, two novel methods to minimize the cogging torque of modular PMSMs are proposed and compared. Both analytical studies and heuristic procedures are adopted to solve the problem. Simulation results with the finite element method have been presented to validate the proposed methods. The results achieved exhibit a reduction of the cogging torque over 90% and show that conventional methods used for one-piece stator PMSMs are not effective against the additional harmonic components produced by modular stators. Also, the spread of the IoTs (Internet-of-Things), edge and cloud computing
technologies offers novel perspectives on the monitoring and maintenance of PMSMs. Although data-driven approaches can be considered dominant in this context thanks to the availability of big data, the potential of model-based approaches has not been considered and exploited in this novel scenario. Modelbased approaches are based on the parameter identification of the system. Many well-known solutions have been developed to identify the parameters of PMSMs, but these are not feasible in large-scale applications because these are not designed for straight-through processing where the human component is negligible and IoTs and edge-cloud computing can give their best. Therefore, in the present work, the problem of the automated parameter identification processing data produced by the PMSM drive without ad-hoc tests or control actions is considered. This problem has been addressed by means of the design of an innovative algorithm based on coupled Adaline Neural Networks. Data
produced by the PMSM during its ordinary operations are used to feed the Adaline Neural Networks. Moreover, an analytical study has been performed for the convergence and estimation errors analysis of the proposed algorithm. Finally, simulation and experimental investigations have been performed for verification purposes. The results achieved show a good accuracy of the parameter identification, with experimental estimation errors lower than 15% without any manual action
Development and testing aspects of high speed induction machines
No full textThis paper reviews the development and testing aspects of high speed induction machines, through a case study involving a 120 [kW], 25000 [rpm] Induction Machine for a power generation application. In the first part, developments in materials and components including electrical steels and copper alloys are discussed, and their impact on the machines' design and construction is investigated. In the second part of this paper, the testing aspects and test results of the prototyped Induction Machines are reported
A high-speed permanent-magnet machine for fault-tolerant drivetrains
Full text linkThis paper details the design considerations of a permanent magnet (PM), three phase, high speed, synchronous machine for fault tolerant operation. A multidisciplinary approach to the optimal design of the machine is adopted targeted at minimising the additional losses resulting from faulty operating conditions and accounting for the remedial control strategy implemented. The design of a closed slot, 6 slots, 4 pole machine is presented. The machine is prototyped and tested to validate the analytical-computational performances predicted in the design and analysis stage under healthy and faulty condition
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
High speed solid rotor induction machine: Analysis and performances
No full textThe paper presents the design, analysis and testing aspects of high speed induction machines equipped with solid rotor. At first the theoretical background and design aspects of solid rotor for induction machines is presented considering electromagnetic, thermal and mechanical aspects and focusing on the assessment of end-region factor effects. The techniques are benchmarked against a 120 kW solid rotor induction motor designed for power generation application
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A Holistic Electrical Machine Design Tool for More-Electric and Hybrid-Electric Aircraft
No full textThe power density of electrical machines required for more-electric and hybrid-electric aircraft has become a critical aspect and target of optimization. This paper looks at the development aspects of a multi-domain tool to aid for system-level optimization of electrical machines within next-generation high power-density aerospace applications. The electromagnetic, thermal and mechanical aspects are wholly integrated, thus enabling the optimization including the non-active mass. The implementation and overall architecture are described with the aim of investigating the impact of coolant flowrate, coolant medium as well as efficiency on the achievable power to mass ratio
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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