1,721,324 research outputs found
DESIGN AND ANALYSIS OF HIGH-SPEED ELECTRICAL MACHINE CONSIDERING MAGNET EDDY CURRENT LOSS COMPUTATION
No full textNelle macchine a magneti permanenti (PM) ad alta velocità, una stima precisa e la riduzione delle perdite per correnti parassite nel rotore sono cruciali per ottenere migliori prestazioni e alta efficienza. Queste perdite aumentano significativamente con la velocità di rotazione crescente, influenzando considerevolmente la temperatura dei PM e incrementando il rischio di smagnetizzazione irreversibile. Il focus principale di questa tesi è la precisa computazione e mitigazione delle perdite per correnti parassite nei magneti, una questione critica aggravata dalle armoniche spaziali nelle operazioni ad alta velocità. Vengono proposte strategie progettuali innovative, inclusa l'incorporazione di cave ausiliarie nello statore e meccanismi di contenimento del rotore, per ridurre sostanzialmente le perdite per correnti parassite, mantenendo al contempo l'integrità meccanica alle alte velocità di rotazione. Inoltre, viene introdotto un metodo analitico per la computazione precisa e rapida delle perdite per correnti parassite nelle macchine a magneti permanenti superficiali (SPM). Questo metodo elimina la complessità degli approcci convenzionali basati su serie di Fourier, fornendo uno strumento efficiente e accurato per l'ottimizzazione della progettazione nelle fasi iniziali. Viene anche proposta una nuova metodologia di progettazione per generare avvolgimenti concentrati a slot frazionari simmetrici a multiphase (FSCW), che supera le limitazioni della tecnica convenzionale "star-of-slot".
I risultati di questa ricerca sono stati validati attraverso un'ampia analisi agli elementi finiti (FEA) e, ove applicabile, mediante verifiche sperimentali. I metodi e le soluzioni progettuali proposte forniscono una solida base per ulteriori avanzamenti in termini di prestazioni e affidabilità, facilitando l'evoluzione delle macchine elettriche ad alta velocità di prossima generazione, in grado di soddisfare le crescenti esigenze delle applicazioni ingegneristiche moderne.In high-speed PM machines, a precise estimation and reduction of rotor eddy current losses are crucial for achieving better performance and high efficiency. These losses significantly rise with the increasing rotational speed, which considerably affects PM temperature and increases the risk of irreversible demagnetization. The primary focus of this thesis is on the accurate computation and mitigation of magnet eddy current losses, a critical issue exacerbated by spatial harmonics in high-speed operations. Novel design strategies, including incorporating auxiliary stator slots and rotor retaining mechanisms, are proposed to substantially reduce eddy current losses while maintaining mechanical integrity at high rotational speeds. Furthermore, an analytical method for the precise and fast computation of eddy current losses in SPM machines is introduced. This method eliminates the complexity of conventional Fourier series-based approaches, providing an efficient and accurate tool for early-stage design optimization. Additionally, a novel design method is proposed for generating symmetrical multiphase fractional-slot concentrated windings (FSCWs), which overcomes the limitations of the conventional star-of-slot technique.
The findings of this research have been validated through extensive finite element analysis (FEA) and, where applicable, experimental verification. The proposed methods and design solutions provide a strong foundation for further advancements in performance and reliability, facilitating the evolution of next-generation high-speed electrical machines that meet the increasing demands of modern engineering applications
Analytical Computation of Permanent Magnet Eddy Current Loss in Surface Mounted Machines Considering Circumferential Segmentations
No full textAccurate computation of eddy current losses is very crucial for permanent magnet (PM) machines. These losses significantly affect the electromagnetic performance and temperature of the PM, which can cause irreversible demagnetization. In this paper, eddy current losses in the permanent magnet machine with fractional slots concentrated winding configuration is investigated analytically. A complete analytical method considering circumferential magnet segmentation is presented. The results computed by the proposed method are validated by finite element (FE) simulations with different slot/pole combinations of inner and outer rotor designs. The proposed analytical method is useful to predict eddy current loss in the magnet with acceptable accuracy but in a very computationally efficient way
مولانا حامد علی خانؒ کی دینی خدمات کا تجزیاتی مطالعہ: An Analytical Study of the Religious Services of Maulana Hamid Ali Khan
No full textIslamic teachings encapsulate fundamental principles and practices derived from Quran Hadith and Islamic Jurisprudence. Central to Islam is the belief in Monotheism (Tawhid), Prophethood (Risalat). Rooted in the Quranic Revelations and Prophetic traditions of Prophet Muhammad (SAW) Islamic Religious teachings encompass a comprehensive framework guiding believers in the matter of faith, morality and societal conduct. Maulana Hamid Ali khan is a revered figure in Islamic circles renowned for his profound intellect through an interdisciplinary lens. It examines Maulana Hamid Ali Khan illuminates his literary genius and analysis which offer insight into spirituality, morality and social issues. Beyond his literary pursuits, Maulana Hamid Ali Khan’s educational leadership and academic services are scrutinized, revealing his role as a beacon of knowledge and a unifying force within the Islamic community. Through his enlightening teachings Maulana Hamid Ali Khan not only imparts doctrinal knowledge but also foster moral development, social cohesion, and interfaith dialogue within Muslim communities and beyond. His exemplary leadership in addressing contemporary challenges underscores the transformative impact of religious services
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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