1,720,958 research outputs found
Doubly Excitated Synchronous Machines for Traction Applications
Full text linkElectrical motor is the crucial component in the drivetrain of hybrid and electric vehicles. Over the last decades, most traction drive systems have been mainly equipped with induction machines, wound field synchronous machines, and permanent magnet machines. Among these three alternatives, permanent magnet is currently the most used topology for traction applications. This paper discusses alternative machine solutions reported in literature that combines advantages of both permanent magnet machines and wound field synchronous machines. These machine topologies, usually referred in literature as doubly excited synchronous machines, are classified on the basis of three criteria: excitation paths, excitation sources location, field direction. The paper reports feature and drawbacks for the considered machine structures and compares both performance and constructive complexity in the light of their perspective use in traction applications
Comparison of Superposition Equivalent Loading Methods for Induction Machine Temperature Tests
Full text linkThe superposition equivalent loading method proposed by international standards for testing induction machines allows to conduct temperature tests at reduced different conditions than rated and extrapolate the results to rated values. Much as this test is suitable for large machines that test facilities lack capacity to test, the principle is also applicable to small machines. However, its applicability to small machines has not been extensively studied yet. Furthermore, the three types of the method categorized in the standard IEEE 112-2017 have not been compared to establish their equivalence or otherwise. This paper reports an extensive test campaign on different small size induction motors to determine both the applicability of the method to small machines and to compare the equivalence of the three types of approach. Multiple reduced voltage and reduced current selections have also been investigated to assess the accuracy of the methods for different test conditions. Test results show that all the three alternative loading methods proposed by the standard seems to be practically equivalent, whit a goodness of fit of the obtained results that tends to improve as the machine rating increases
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
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
Magnetic Equivalent Circuit for Multi-Stage Axial Flux Surface Permanent Magnet Machines
No full textThis paper presents a magnetic equivalent circuit for the electromagnetic analysis of axial flux permanent magnet synchronous machines. The proposed methodology is based on a quasi-3D approach and incorporates the non-linear iron core behavior, the rotor motion, and magnetic leakage effects. A key strength of the proposed approach is its adaptability to different machine configurations, starting from a single-stage network and extended to multi-stage topologies with different stator-rotor arrangements. This article also provides a detailed guide to constructing the reluctance network, including simplifications to facilitate adoption by less experienced designers. Validation is performed against both 3D finite element analysis simulations and experimental tests, demonstrating good agreement in key performance metrics, such as magnetic flux density, back electromotive force, and torque. The results validate the performance of the proposed MEC in reducing computational time while maintaining satisfactory accuracy, positioning it as a valuable tool for preliminary design and optimization of studies
Fast Procedure for the Electromagnetic Sizing of Axial Flux PM Motors
No full textThis paper presents an algorithm for the preliminary design of three-phase surface mounted permanent magnet axial flux motors. The algorithm starts from a limited number of machine specifications, related to the rated performance, few geometrical specifications, and the main material properties. The sizing of the stator and rotor lamination is accomplished through self-consistent analytical formulations. Then, the parameters of the machine equivalent circuit are computed considering both distributed and fractional-slot concentrated winding arrangements. To assess the accuracy of the proposed algorithm, two study cases are presented. The validation is carried out comparing the performance predicted by the proposed procedure with 3D finite element analyses. The results show good agreement between the sizing algorithm and the numerical simulations
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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