1,720,958 research outputs found
The Impact of the Control Strategy in Flux Observer Based Sensorless Control of Synchronous Reluctance Motors
Full text linkThis paper compares different control strategies of the synchronous reluctance motor to outline their impact on the accuracy of flux-observer based sensorless operation. Maximum torque per ampere, maximum efficiency, and maximum power factor controls, usually referred to optimize the operating performance of synchronous reluctance motors are considered. Alternative solutions not usual in literature but specifically investigated for supporting the estimation are also considered, namely constant direct-axis-current and constant direct-axis-flux controls. The flux-observer detects the flux components in the two-phase stationary reference frame by a non-linear model achieved by finite-elements computations. An auxiliary mechanical observer who accounts for the finite-elements mapping of the torque is adjusted by the flux estimation error and provides the rotor position and speed needed for sensorless control. An extended set of experimental tests is presented where the different control methods are compared in terms of position and speed estimation errors and overall control quality. A four poles, three kW synchronous reluctance prototype designed for general industry application is used for testing
Optimum wave energy conversion of a point absorber with direct electrical power take-off
No full textThis paper refers to the passive and reactive control of power-take-off (PTO) systems involved in wave energy conversion. A point-absorber device (buoy) is considered. After a brief introduction of the principles of marine wave-buoy interaction, the passive and reactive controls of the PTO systems are recalled. For each control strategy, the analytical relations for maximizing the power extracted by the wave and the electrical power provided by an active-controlled electrical PTO are defined and verified by simulation. Then, an experimental set-up of a small-scale laboratory simulator of the wave energy conversion system is also implemented. Two vector-controlled PM synchronous machines joined without mechanical backlash are used, one to simulate the wave excitation force and the other the PTO engine. The experimental tests confirm the possibility to extract maximum power by proper setting of the control parameters
Comparison of Synchronous Reluctance Motors and Permanent Magnet Synchronous Motors with Direct Liquid Cooling Arrangement
No full textA comparison of Synchronous Reluctance Motors and Permanent Magnet Synchronous Motors with a Direct Liquid Cooling system is given. Both solutions have been analyzed, designed, and optimized considering the same constraints in terms of geometrical volume, current density, and phase voltage, for more equitable comparison. In addition, Direct Liquid Cooling introduces challenges in the selection of the number of conductors per slot and the number of slots because the slot dimensions need to satisfy an aspect ratio close to one and the adoption of a bigger conductor size. The preferred winding configuration is the concentrated one that simplifies the manufacturing process and, therefore, the cost; however, it was not possible to optimize the Synchronous Reluctance Motor with a concentrated winding arrangement achieving a competitive performance. Based on the results it is clear that mostly Permanent Magnet Synchronous Motors can exploit all the advantages of Direct Liquid Cooling, guaranteeing higher performance than Synchronous Reluctance Motors, especially the torque capability in flux weakening operation
Line-Start Synchronous Reluctance Motor: A Reduced Manufacturing Cost Avenue to Achieve IE4 Efficiency Class
Full text linkThe paper presents the Line Start Synchronous Reluctance Motor (LSSynRM) technology as a promising avenue to bring IE3 motor portfolios to the IE4 efficiency class at contained manufacturing costs. Indeed, the achieving of IE4 efficiency class is concerning many motor manufacturers, where the small-medium manufacturers seem to face the higher efforts in converting their product portfolio. To this extent, a methodology to improve the IE3 Induction Motor (IM) efficiency by introducing the Line Start Synchronous Reluctance motor technology in the IM motor is presented. The new motor design guidelines and constraints are figured out to reduce the impact on the manufacturing process. The paper presents a detailed experimental validation of the realized prototype in steady-state and transient operation referring to a target IE3 IM. The prototype proved to be a cost-effective, mass production-ready solution for super-premium efficiency IE4 motors. The LSSynRM technology demonstrated to be an effective high-efficiency avenue at reduced manufacturing costs in a broad panorama of low-inertia industrial applications
Transient Modeling of Induction Motors considering Space Harmonics
No full textThis paper presents a transient mathematical model for induction motors based on space harmonics and its validation by finite-elements method comparison. The model is based on the computation of the magnetomotive force-wave for squirrel cage induction motors, and accounts for the geometry and physical dimensions of the stator and rotor windings. The harmonic components of the airgap field are calculated at each time-step considering the currents in the stator windings and in the rotor bars, the latter modeled as overlap of contiguous coils, as well as the rotor position. The proposed model is compared with finite elements calculations to outline differences and effects of simplifications and harmonic order. A 200kW induction motor designed for a premium electric vehicle is assumed as case-study
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
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