1,721,044 research outputs found
Design optimization of a PMSM stator for powertrain applications considering NVH behavior
No full textIn the current societal landscape, there is a notable inclination towards the acceptance and adoption of electric vehicles, prompting heightened attention from academia and literature towards research and technological advancements in all aspects of electric vehicle design. As the most crucial component of an electric vehicle, the motor holds particular significance. The primary aim of this article is to investigate the causes of noise and vibrations in electric motors, alongside conducting an analysis of Sound Pressure Level and order tracking to assess the motor's acoustic performance. Subsequently, employing the techniques outlined in this study, the objective is to propose a motor design that maintains motor performance while reducing noise and vibration production. This redesign of the base motor will entail the application of advanced motor design techniques, specifically focusing on the geometric design of internal motor components
An Angular Speed and Position FLL-Based Estimator Using Linear Hall-Effect Sensors
Get PDFThis paper proposes using a frequency-locked loop-based detector to estimate rotational speed and angle position for an electric machine rotor shaft. The measurement system consists of arrays of permanent magnets fixed to the rotor shaft together with linear Hall-effect sensors attached to a fixed frame. Parametric uncertainties on the sensor assembly lead to significantly noisy signals, exhibiting unbalance and harmonic distortion. To accurately estimate rotational speed and angle, it is proposed to use a frequency-locked loop scheme based on a fourth-order harmonic oscillator (FOHO) to allow the processing of the symmetric components, thus dealing with the unbalance. The scheme also includes an adaptive law to reconstruct the fundamental frequency. Moreover, a harmonic compensation mechanism comprising parallel FOHOs is included; each FOHO is tuned at the spectral component under concern for its cancellation. The proposed algorithm delivers a clean estimate of the positive sequence fundamental component despite the disturbances at the signals provided by the Hall-effect sensor, which is used to reconstruct the rotation angle. The described approach could enhance low-cost sensing solutions in applications where position feedback is mandatory and sensorless control is impossible, not requiring special installation considerations
A sequence impedance matrix approach to current unbalance detection for grid code fulfillment
No full textThis work presents a novel method to identify the source of current unbalance during the interaction between industrial consumers and the utility. Since such unbalance yields detrimental effects over the network operation and efficiency; it must be mitigated to avoid their propagation towards the whole grid. To prevent this situation, regulations about the maximum permissible limits of unbalance are recently incorporated in grid codes. Unfortunately, in the absence of an accurate method to identify the agent inducing the unbalance; the problem, responsibility, as well as the solution, is vulnerable to misinterpretation. This situation is quite relevant, for both the consumer and the utility since imputations are subject to penalties. Prompted by this issue, we devised a method based on the computation of sequence impedance matrices. Then the underlying elements of the sequence impedance matrix will expose the occurrence of an unbalance as well as its source, which leads to a theoretically derived metric. This method is tested using real measurements of actual industrial loads connected to different voltage levels (i.e. 230 kV, 161 kV and 115 kV). The results demonstrate accuracy in the detection and identification of the cause of unbalance, considering a wide range of power consumption.</p
Comparative Study of Interior Permanent-Magnet Synchronous Motor Topologies for Motorcycle Traction Application
No full textThe trend for vehicle electrification has gained importance worldwide as a solution to the pollution caused by internal combustion engines. In addition, electric vehicles have become a sustainable transportation solution over the years. Consequently, electric motors have gained significant prominence in the field of vehicle manufacturing. Interior Permanent Magnet motors have emerged as the preferred choice for three-phase motor production in electrified powertrain for passenger cars. However, other lightweight transportation systems, such as motorcycles and scooters, have received less attention from the scientific community. This study presents a comparative analysis of four rotor topologies used in interior permanent magnet motors for electric motorcycles. The evaluation of these motors is based on their performance and cost. Research findings indicate that the V-shape topology stands out as the most economically efficient among the four examined topologies. The selection of an optimal rotor topology depends on the specific application, which requires an understanding of the strengths and weaknesses associated with each motor topology
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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