1,721,099 research outputs found
Decoupled d-q Axes Current-Sharing Control of Multi-Three-Phase Induction Machines
Full text linkMulti three-phase drives are a particular case of multiphase systems, which are often used in high-power applications, such as wind-energy generation, naval and railway propulsion. In a multi three-phase system the electric machine is fed by more than one three-phase converter. A current sharing algorithm for multi three-phase drives allows setting unequal current references among the converters so that each of them differently contributes to the generation of the magnetic torque and flux. Suitable current sharing control systems already exist and have been presented for multi three-phase machines. This paper illustrates a current sharing technique where the contributions to the rotor flux for the three-phase inverters, related to the d-axis current, is decoupled from the contributions to the electromagnetic torque, which depends on the q-axis current. Also, the presented algorithm minimizes the Joule losses in the stator winding. Finally, the advantages of the proposed method are analyzed and confirmed by experimental tests. The effectiveness of the control strategy is validated on a scaled prototype of a quadruple three-phase starter/generator for more-electric-aircraft applications
Voltage feedback of an LLC resonant converter with a rotary transformer
No full textRotary assembly platforms are used in several automation applications, such as box-fill systems. In modern automatic machines, several actuators may be mounted on the rotating platform, but this architecture raises the problem of their feeding. The solution developed in this paper consists in adopting a LLC resonant converter that uses the leakage and magnetizing inductances of a rotary transformer as inductors of the resonant network. Furthermore, since the output voltage on the rotating platform cannot be directly measured, a sensorless control scheme has been developed to improve load regulation. Experimental results are provided to show the effectiveness of the converter and its control scheme
Optimal flux selection for multi three-phase machines in normal and fault conditions
No full textA general method for the optimal flux selection in multiphase induction machines is proposed in this paper. The multiphase machines are configured as multi three-phase units. The proposed algorithm allows computing the optimal flux for the Maximum Torque per Ampere (MTPA) operation in both normal and open-winding fault conditions. The results of the proposed method can be applied to many different types of control schemes, such as Field Oriented Control (FOC), Direct Torque Control (DTC), Direct Flux Vector Control (DFVC), thus assuming a general validity. The proposed method has been tested on a 12-phase asymmetrical induction machine in quadruple three-phase configuration (10kW, 6000rpm). The experimental validation has been carried out using a DFVC control scheme based on the multi-Three phase approach
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
Detection and localization of high resistance connections in quadruple three-phase induction motor drives
No full textOwing to its intrinsic redundant structure, a quadruple three-phase induction motor drive can be successfully employed for applications requiring a high degree of reliability. Furthermore, the flexible power flow control among the four dc-sources can be usefully exploited in electric vehicles fed by separate battery packs. In this paper, the behavior of a quadruple three-phase induction motor drive under an unbalance of the stator phases due to high resistance connections is analyzed. In particular, a control scheme that can detect the stator resistance dissymmetry and ensure an undisturbed behavior of the motor drive, is presented. The effectiveness of the presented control scheme is verified by means of numerical simulations
Sensorless speed observer based on third-order spatial field harmonic for multiphase induction motor drives
No full textThis paper presents an electric drive consisting of a multiphase induction motor fed by a multiphase inverter. The control system is similar to that of a traditional field-oriented control for three-phase motors, but the machine speed is estimated by a novel sensorless observer. Since multiphase motors with M phases (M is supposed odd) have the capability of controlling the odd spatial harmonics of the magnetic field up to the (M-2)th order, the developed observer excites the third-order spatial harmonic of the magnetic field to estimate the rotor speed. Simulation results are provided to assess the performance of the observer
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
Comparative performance evaluation of fullbridge, H5, and H6 topologies for transformerless solar converters
No full textNowadays, the use of transformer-less single-phase inverters is widespread for domestic photovoltaic applications due to the high efficiency that can be obtained. Here, three similar topologies of transformer-less inverters are compared to highlight their differences. They are the full-bridge, the H5, and H6 inverters. The analysis considers the efficiency, the leakage current, and the quality of the output current when different modulation techniques are adopted. The experimental tests are carried out in the same operating conditions and with the same experimental set-up, thus emphasising the advantages and drawbacks of each topology
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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