1,720,956 research outputs found
A Sensor Fusion Based Temperature Estimation Model for Oil-Cooled Windings
No full textThis article introduces an innovative method to monitor the average winding temperature in real-time during the operation of an oil-cooled electric motor, particularly suitable for high-performance automotive applications. It is based on the sensor fusion of two distinct dynamic models: one considering the measurement of local temperature through a thermal sensor positioned on the end-winding of the motor, and the other utilizing a first-order model to predict the average winding temperature. The integration of these models significantly enhances the accuracy in estimating the average winding temperature, particularly for short-duty and high current densities
A New Hybrid Control Strategy in Flux-Weakening Region for High Performance Traction IPMSM
No full textThis paper investigates a novel hybrid flux weakening (FW) control scheme for interior permanent magnet synchronous motor (IPMSM) drives operating in a wide DC-link voltage range. Due to possible fluctuations in the motor parameters or considering dc-link voltage variation, the available voltage margin can be really too small and therefore the dynamic performance is degraded. One of the main objectives of the proposed FW regulator is to maintain the modulation index within a certain range, in order to exploit most of the battery voltage and minimize the losses and total harmonic distortion (THD) of the power converter. To control the motor in the FW region the proposed method exploits a hybrid control strategy based on a feed-back voltage controller feeding a virtual DC voltage variation into a DC-voltage, torque, and speed dependent look-up table (LUT) which sets the optimal current references also considering variable motor inductances
A two-phase HVAC-integrated cooling system for traction motors: modelling and performance analysis
No full textTwo-phase fluid flows have been regarded as a candidate cooling method for electric motors in order to boost torque density. Low-temperature, two-phase refrigerant is inherently available in vapour-compression Heat Ventilation Air Conditioning (HVAC) systems which are typically on-board vehicles. This paper explores the potential of bleeding a refrigerant fraction from the HVAC vapour-compression “core” cycle and feed it into the traction motor windings to achieve a radical cooling. In order to evaluate the features and performance of this integrated two-phase motor cooling concept, the paper proposes a simplified modelling technique that integrates the HVAC vapour compression cycle with the motor cooling sub-models. The objective is to assess the reduction in losses and the associated benefits in mitigating the extra burden on the motor and the oversizing requirements of the HVAC compressor
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
Avvolgimenti multi-conduttore per motori elettrici operanti a frequenza elevata
Full text linkLAUREA MAGISTRALEQuesta tesi affronta il tema della riduzione delle perdite AC negli avvolgimenti ad alte frequenze (500 Hz – 2.0 kHz) delle macchine elettriche. L'obiettivo principale è progettare motori che operino a frequenze elevate, al fine di ottenere una maggiore densità di potenza attraverso l'aumento della velocità nominale e del numero di poli, riducendo così la massa complessiva del motore. Questo aspetto riveste particolare importanza nei settori automobilistico e aerospaziale, dove le dimensioni ridotte e l'alta densità di potenza sono fattori chiave.
Il lavoro di ricerca si concentra sulla progettazione di avvolgimenti adeguati alle alte frequenze, in modo da soddisfare i requisiti richiesti e limitare le perdite aggiuntive. In particolare, vengono analizzate diverse tipologie di avvolgimenti, con particolare attenzione ai conduttori in barra di tipo Hairpin. L'idea di suddividere questi conduttori viene introdotta con l'obiettivo di determinare la disposizione ottimale per limitare le perdite AC.This thesis addresses the topic of reducing AC losses in high-frequency (500 Hz – 2.0 kHz) windings of electric machines. The main objective is to design motors that operate at high frequencies in order to achieve higher power density by increasing the rated speed and the number of poles, thus reducing the overall mass of the motor. This aspect is particularly important in the automotive and aerospace sectors, where compact size and high-power density are key factors.
The research work focuses on the design of windings suitable for high frequencies, aiming to meet the required specifications and limit additional losses. Various types of windings are analyzed, with particular attention given to Hairpin-type bar conductors. The idea of replacing solid conductors with subdivided/transposed ones is introduced with the goal of determining the optimal arrangement to limit winding AC losses
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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