3,123 research outputs found
An Analytical-Numerical Approach to Model and Analyse Squirrel Cage Induction Motors
No full textNowadays, finite element analysis represents the most accurate tool to analyse electrical machines. However, the time domain resolution of electromagnetic problem, in some cases, requires long simulation time due to the induced nature of the currents. The computational burden increases when the machine features a skewed layout on the stator or rotor structures, since this requires 2D multi-slices approximated analysis or even a full 3D model. In this paper, a general analytical method to model electromagnetic devices is applied to a squirrel cage induction motor featuring a skewed rotor structure. The modelling approach is wisely implemented and adapted to pursue a fair balance between accuracy of the analysis and computational burden, taking advantage of all the symmetries existing in the rotor cage of the machine, aiming to minimize the model complexity. A comparative analysis in term of the inductances between analytical and finite element is proposed. The results provided by the model developed are compared with respect to the corresponding values provided by both finite element and experimental test performed on the reference machine. Such comparisons show that the proposed model is actually able to achieve a pretty good balance between accuracy and computational efficiency
Rotor Slot Design of Squirrel Cage Induction Motors with Improved Rated Efficiency and Starting Capability
No full textAmong the electro-mechanical devices transforming energy from electrical to mechanical, the squirrel cage induction motor can be surely considered a workhorse of the industry due to its robustness, low cost and good performance when directly fed by the a.c. grid. Being the most influencing motor topology in terms of energy consumption, optimizing the efficiency of squirrel cage induction motors could lead to a great impact towards the reduction of the human environmental footprint. The induction motor design aided by finite element analysis presents significant challenges because an accurate performance prediction requires a considerable computational burden. This paper makes use of an innovative fast and accurate performance evaluation method embedded into an automatic design procedure to optimize different rotor slot geometries. After introducing the performance estimation approach, its advantages and limits are discussed comparing its prediction with the experimental tests carried out on an off-the-shelf induction motor. Different rotor cage structures with increasing geometrical complexity are then optimized in terms of starting and rated performance adopting the same design optimization process, the same stator geometry and constituent materials. The analysis of the optimal solutions shows how it is possible to improve the rated efficiency without compromising other performance indexes. The presented results can be used as general design guidelines of squirrel cage induction motors for industrial applications
A imagem de Alessandro Baricco no Brasil
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão, Programa de Pós-Graduação em Estudos da Tradução, Florianópolis, 2013.Com a intenção de delinear o modo pelo qual o escritor italiano Alessandro Baricco se inseriu no sistema literário brasileiro e os caminhos percorridos pelos seus livros traduzidos, esta dissertação dá voz às experiências tradutórias de seus tradutores. A inserção de Bariccono Brasil tem seu início em 1997, através de uma proposição da Profa. Dra. Roberta Barni à editora Iluminuras da tradução de Oceano Mare. A partir daí, outras sete obras foram publicadas no Brasil, sendo três delas traduzidas por Roberta Barni e as outras quatro por quatro tradutores diferentes. De um lado, considera-se o tradutor como figura principal namediação entre culturas, e, de outro, se analisa a realidade desta figuradentro do sistema literário, sua invisibilidade, seus limites e o exercíciode sua profissão. A pesquisa conta, ainda, com críticas e resenhas referentes ao autor italiano publicadas em jornais consagrados no Brasil, considerando estas como parte constituinte da imagem de Baricco refletida em território nacional. Abstract : Intending to delineate the way the Italian writer Alessandro Baricco has been inserted in the Brazilian literary system and the paths his translated books have followed, this thesis gives voice to the translating experiences of his translators. Baricco's insertion in Brazil began in 1997, through a personal project of Dr. Roberta Barni, with her translation of Oceano Mare. Since then, seven other of his works have been published in Brazil, three of which were translated by Roberta Barni and the other four by four different translators. On the one hand,the translator is considered as the main figure in mediation betweencultures and, on the other, this figure's reality is analyzed within theliterary system: its invisibility, its limits and its professional practice. Criticisms and reviews of this Italian author published in well established Brazilian newspapers are also considered, with the understanding that they are part of Baricco's image reflected here
La maturità di Alessandro Fei del Barbiere, in bilico tra Maniera e Riforma
No full textThis article studies the mature career of the Florentine painter Alessandro Fei del Barbiere (1537-1592), beginning with the rediscovery of the 'Ascension' altarpiece formerly in the Albizi Chapel in the destroyed church of San Pier Maggiore, Florence. Studying this painting and others recorded in 1584 by the biographer Raffaello Borghini, such as the two altarpieces for Santa Maria delle Grazie and the Madonna dell'Umiltà in Pistoia, the author reconstructs a body of works showing how in the 1580s Fei gradually went beyond the archaic style of his apprenticeship - he had been trained by Ridolfo del Ghirlandaio and Pierfrancesco Foschi, but was also marked by the Maniera of Vasari - evolving towards naturalism in both mimesis and pictorial handling. In Florence, his development partly parallels that of Santi di Tito and his circle, but Fei was also influenced by a probable sojourn during the early part of that decade in Rome, where he could have been inspired by Girolamo Muziano and the painters working for Pope Gregory XIII. Among other proposals, the author suggests that the artist was responsible for decorating the chancel of Fiesole Cathedral (c. 1584-1589), which consisted of an altarpiece, only rarely discussed by scholars, and a cycle of frescoes hitherto attributed to Nicodemo Ferrucci
Rotor Design Optimization of Squirrel Cage Induction Motor - Part I: Problem Statement
No full textSquirrel cage induction motor is the most widely adopted electrical machine in applications directly fed by the main grid. The analysis, design and optimization of this machine topology has been addressed by a considerable amount of literature over the last century. Although its wide adoption, the induction motor design, especially when carried out in an automatic fashion, still presents significant challenges because the accurate prediction of the performance requires time-consuming finite element analysis. This work proposes a systematic approach to perform the design optimization of a squirrel cage induction motor focusing on the rotor slot geometry, being this the major player in defining the torque-speed characteristic. Structured as a two-parts companion papers, this first part presents an innovative performance evaluation methodology which allows a very fast estimation of the torque and efficiency behaviour preserving the results' accuracy. The proposed performance estimation technique is assessed against experimental tests carried out on an off-the-shelf induction motor. The selection of the performance indexes to be optimized is justified in detail along with the description of a generalized rotor parametrization which allows a comprehensive exploration of the research space
Rotor Design Optimization of Squirrel Cage Induction Motor - Part II: Results Discussion
No full textThe rotor slot geometry of a squirrel cage induction motor plays the most important role in defining the torque-speed characteristic when the power supply is directly provided by the main grid. In this article it is shown how the rotor slot geometry can be optimised to satisfy different electromechanical requirements, depending on specific applications. This work, the second of two companion papers, briefly recalls the novel systematic approach, proposed in Part I, to perform the optimization of squirrel cage induction motors. Here, the optimization results achieved satisfying a wide spectrum of requirements are analysed in depth. Furthermore, the trade-off among the several performance indexes, and their correlation with the geometrical parameters is discussed. The possible advantages, and disadvantages of adopting a copper cage is also quantified for all possible performance requirements. The influence of the motor thermal behaviour, and harmonic losses on the overall performance are also discussed allowing to validate the proposed design optimization procedure, and its results. The outcomes of this work are opening to new design approaches that enable to optimise the performance of one of the most popular electrical machines adopted in industry, the squirrel cage induction motor
High Speed Permanent Magnet Assisted Synchronous Reluctance Machines - Part I: A General Design Approach
No full textThe design of synchronous reluctance machines with and without permanent magnets assistance constitutes a challenging engineering task due to the numerous design variables and performance indexes to be considered. The design complexity increases even further when the application requires high speed operation, with consequent rotor structural constraints and and related effects on the electromagnetic performance. Structured as two-parts companion papers, this first part proposes a comprehensive design procedure able to consider all the non-linear aspects of the machine behaviour, greatly reducing the number of independent design variables, without worsening the computational burden. In particular, the non linear behaviour of the rotor iron ribs and the effect of the permanent magnets on the structural design are all taken into account with the proposed iterative design procedure targeting the achievement of a desired power factor. The proposed method will be then used to draw some preliminary design considerations highlighting the several trade-offs involved in the design of high speed permanent magnet assisted synchronous reluctance machine. Part I is setting the theoretical bricks that will be further expanded and experimentally validated in the companion paper Part II
Analytical-Numerical Model for Synchronous Homopolar Machines
No full textSynchronous homopolar machines represent a viable solution for applications requiring a robust electro-mechanical conversion system. Their diffusion is hindered by the low power density and by their complex three-dimensional magnetic behavior which requires time-consuming 3D finite element analysis for the performance prediction. This manuscript proposes a general analytical electromagnetic model able to evaluate the performance of both split and pass-through winding layouts addressing the existing methodological gap of the literature. The modelling approach - based on equivalent winding and permeance functions - reduces the resolution of the 3D electromagnetic problem to two axially coupled 2D problems considering all the mmf contributions, including the end-winding one, which cannot be neglected for the split winding configuration. The analytical model is numerically implemented and its predictions are compared with the 3D FE analysis. The comparison demonstrates the effectiveness of the proposed model in estimating the performance in different operating conditions and any rotor position. Several experimental tests are carried out on a laboratory-scale prototype to validate the analytical predictions in terms of inductances vs. rotor position and voltage waveforms. Although the experimental assessment shows the limitation of the proposed technique, i.e. the linear magnetic behaviour, this could potentially serve as a basis for the fast design optimization of this machine topolog
High Speed Permanent Magnet Assisted Synchronous Reluctance Machine - Part II: Performance Boundaries
No full textThe insertion of permanent magnets (PMs) within the rotor slots of Synchronous Reluctance Machines (SyRM) is the most common design strategy used to increase significantly their performance. In this paper it is shown how a permanent magnet assisted synchronous reluctance machine (PMaSyRM) can be optimized to satisfy all the electromagnetic and structural constraints arising as the maximum operating speed increases. This is done considering a variety PMs material. This work, the second of two companion papers, briefly recalls the novel systematic design approach proposed in Part I, and then describes the characteristics of the optimal machines achieved considering a maximum speed ranging from 1 to 140 krpm with and without the assistance of ferrite and neodymium based PMs. The reasons behind the performance deterioration as the speed increases are all investigated along with the geometrical variations of the optimal designs. The selection of the design solution to be manufactured is justified as well as the final structural and electromagnetic refinement stages leading to the final prototype. All the reported considerations are experimentally validated testing an 8.5kW at 80krpm PMaSyRM, comparing the measured and expected performance in terms of torque and internal power factor
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