1,721,073 research outputs found
Design Optimization of a Synchronous Reluctance Motor Based on Operating Cycle
Full text linkSynchronous reluctance motors are becoming an interesting solution for drives applications requiring high efficiency. The design of those machines is normally based on the optimization of the motor performance at the rated working point in terms of torque production, torque ripple and efficiency, but in many applications the drive will operate for most of the time at partial load and frequent overload may be required, with a speed not necessarily equal to the rated value. In this work we propose an optimized machine design method to maximize the drive efficiency on the total operating cycle, considering a specific speed and torque profile. Four typical working points are selected, each of them maintained by the machine for a different time in the operating cycle. The obtained machine is compared with the one optimized based on the rated conditions only, showing slightly higher losses on a single working point but an improved efficiency on the global operating cycle
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
High Accuracy Real-Time Simulation of Synchronous Reluctance Motor Drive Using Parallel Processing
No full textThis paper presents a parallel processing approach to the real-time simulation of electrical drives. In a real-time simulation, the plant model runs on the same target controller and at the same control rate as the actual application. Hence, the plant model must be as accurate and the integration step of its solver as small as possible. The computing capabilities of the Texas Instruments Delfino F28379S microcontroller, specifically the availability of the Control Law Accelerator coprocessor, are explored using MATLAB/Simulink. A synchronous reluctance motor drive, challenging due to intrinsic nonlinearities and fast transients, is considered. The subdivision of control and plant modeling tasks between the Central Processing Units and the Control Law Accelerator and their synchronization issues are presented and discussed. For a better evaluation, different solver algorithms are analyzed. A detailed comparison between experimental tests and real-time simulations completes the work
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
Model Validation of Synchronous Motors With a New Standstill Measurement Technique
Full text linkPermanent magnet synchronous machines (PMSM), synchronous reluctance machines (SynRM), and electrically excited synchronous machines (EESM) are widely used in the industry and transportation sectors. Their rotors are often equipped with conducting parts like permanent magnets, thick rotor laminations, damper windings, or a conducting sleeve, or they even have a solid rotor core. Such conducting elements do not allow applying standard AC supply techniques for inductance measurements because of the alternating flux induced by eddy currents. We propose a new technique for inductance measurement at a standstill with a quasi-static voltage supply, which mitigates the eddy current phenomenon. The inductance is measured at several rotor positions over a complete electrical cycle, which allows to proceed with a harmonic spectrum analysis of the inductance variation. With this information, it is possible to estimate motor performance characteristics, such as optimum torque, voltage control, power factor, and torque ripple. The new technique is experimentally validated on a 12 kW axially laminated anisotropic solid-rotor high-speed SynRM. In principle, the method also suits PMSMs, EESMs, and other synchronous machines (not verified in this paper). Experimental validation with a solid-rotor SynRM shows a good correspondence with the simulation. Furthermore, the torque computed using the measured inductance is very similar to the experimental one confirming the effectiveness of the method
Adoption of the Synchronous Reluctance Motor in Electric Vehicles: a Focus on the Flux Weakening Capability
No full textThis article presents the definition of the performance that the electric motor should have in order to satisfy the requirements of the electric vehicle in terms of acceleration time and maximum speed, starting from a simplified vehicle model, considering the motor torque minimization and the input power minimization. In order to verify the effectiveness of the synchronous reluctance motor in traction applications, it has been evaluated in two case studies: a high-performance vehicle and a city car, where different flux weakening capabilities from the motor in function of the minimization strategies can be pursued to satisfy the requirements. If the car requires high performance in terms of acceleration time and maximum speed, the poor flux weakening capabilities of the synchronous reluctance motor induces a machine oversizing in terms of peak power; by assuming this, it is, however, possible to satisfy the requirements considering the maximum available encumbrance due to an advanced and innovative optimized design procedure. The motor of the city car is obtained only by modifying the stack length and the windings (scaled version), and on this last solution, a prototype has been realized and fully tested; the experimental tests confirm the results of the simulations
An Open-Loop Starting Procedure for Sensorless Control of Synchronous Reluctance Motors
No full textThis paper presents the development and test of an open-loop start-up procedure for synchronous reluctance motor drives, designed to match the polynomial torque-speed profile of a pump application. The integration of this procedure with a flux-observer allows for relatively easy sensorless operation in those applications that do not require steady-state operation at low or null speed. In particular, the paper focuses on the design of the open-loop control references in order to achieve the maximum acceleration performance and the concerns for a smooth and safe switching towards the closed-loop observer. Real-time simulation and experimental results are presented to prove for the effectiveness of the method
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