1,720,963 research outputs found
Determination of PM Flux Linkage Based on Minimum Saliency Tracking for PM-SyR Machines without Rotor Movement
Full text linkPermanent magnet assisted synchronous reluctance (PM-SyR) motors often present relevant magnetic saturation, especially if overload capability is exploited. The knowledge of current-to-flux relationship is mandatory for proper motor control, and it becomes even more critical in the case of sensorless applications. Reliable standstill self-commissioning tests have been recently developed for synchronous reluctance (SyR) motors without producing rotor movement. This procedure can be extended to PM-SyR motors, but being at standstill, it does not retrieve the flux contribution related to the permanent magnets (PMs). This article integrates the identification of the flux characteristics including a novel test for estimating the PM flux linkage, obtaining the complete magnetic characteristic of the PM-SyR motor. The identification session is performed at standstill and without a position transducer, independently of the mechanical load being connected or not. Such conditions are considered the most demanding for self-commissioning tests. The machine is first excited with a proper sequence of bipolar high voltage pulses to determine its current-dependent flux components. Then, the estimate of PM flux linkage is retrieved at standstill by evaluating the local saliency along the negative q-axis. The proposed method is supported by detailed finite element analysis and experimentally verified on two PM-SyR motor prototypes, confirming the accuracy of the PM flux linkage estimate
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
Isolated Semi Integrated On-board Charger for EVs Equipped with 6-phase Traction Drives
Full text linkThe recent trend in road transportation electrification pushes the development of reliable and compact solutions for the traction drives and charging infrastructures. This work proposes an innovative on-board battery charger partially integrated with the powertrain of a road electric vehicle equipped with a 6-phase traction motor drive. The integration permits to exploit the traction inverter and motor as power conversion unit and HF transformer respectively, with remarkable benefits in terms of e-axle compactness and cost of the components. Despite the integrated nature of the proposed system, galvanic isolation is provided, ensuring reliable and safe operation of the charger. Over to the traction drive, the proposed topology only requires a passive diode bridge and three grid inductors. A dedicated control strategy is developed to avoid torque production during charging. The proposal is validated by exhaustive simulations. A full experimental stage is currently ongoing, and promising preliminary results are reported
Isolated On-Board Battery Charger Integrated with 6-phase Traction Drive
Full text linkThis paper proposes an innovative topology of on-board battery charger (OBC) for electric vehicles integrated with the traction motor drive. The proposed single phase input OBC, applicable for 6-phase traction drives, is deeply integrated within the vehicle powertrain, to reduce cost and volume of the charger respect to conventional non-integrated solutions. The proposed structure provides galvanic insulation between the grid and the battery, not guaranteed by the other fully integrated chargers in the literature. A dedicated control strategy was developed for absorbing the AC grid current at unitary power factor and low harmonic distortion without torque production during the charging stage. The performance of the proposed OBC are tested by accurate simulation models
Active Flux Position Observer for Sensorless Direct-Flux-Vector-Control at Low Speed
No full textThis paper extends the Active Flux position observer in the low speed region, for sensorless Direct Flux Vector Control of permanent-magnet-synchronous and synchronous-reluctance motor drives. Active Flux observers are popular for back-emf based sensorless control in the medium and high-speed range of the electrical drive. In this paper, the High-Frequency Active Flux approach is used in the low and zero speed region with square wave voltage excitation. The proposed HFAF method allows to control the motor with no need for band-pass filtering nor de modulating the high-frequency signals. Experimental validation is carried out on 1.1 kW Synchronous Reluctance machine proving the effectiveness of the proposed method in speed control
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
State Variable Selection in dqθ Models of Saturated Synchronous Machines: Impact on Accuracy and Simulation Quality in PLECS
No full textThis work develops and compares custom models for 3-phase saturated Permanent-Magnet and Synchronous Reluctance Machines, capturing both space harmonic and saturation effects. Both Voltage-Behind-Reactance (VBR) and Rotor Reference-Frame (RRF) circuital models are extended using the dqθ mapping approach to fully include space harmonics. A central discovery of this study is that the presence of high frequency noise in simulation results is influenced by the choice of the state variables: models implemented with dq currents as state variables consistently deliver smooth and accurate waveforms, whereas those based on dq flux linkage integration and using the inverse flux maps suffer from high-frequency noise. Critically, this behavior is independent of the underlying circuital architecture, applying to both VBR and RRF formulations. The work establishes the use of current-based state variables as a key enabler for high-fidelity, harmonics-inclusive dqθ motor simulation and more in general in circuital simulators
Analysis of overload and sensorless control capability of PM-assisted synchronous reluctance machines
No full textSynchronous reluctance machines are a valid alternative to induction motors for industrial applications requiring variable speed regulation. To mitigate the well-known downside of their lower power factor, permanent-magnet-assisted topologies are adopted. Both high-strength rare-earth magnets and low cost ferrite magnets can be used in such machines. Their design and optimization procedures have been discussed in related literature. This paper compares synchronous reluctance machines assisted with NdFeB and ferrite magnets, focusing on torque overload capability and feasibility of saliency-based position estimation algorithms. Three prototypes were realized and tested. They all have the stator of a commercial induction motor, and three custom synchronous reluctance rotors with same laminations: one has no magnets, the other two have NdFeB and ferrite magnets respectively, designed to give the same torque at rated current. Results from simulations and experiments are presented, focusing on torque and demagnetization limits in the over-current loading range. Moreover, the feasibility of saliency-based sensorless methods is investigated, both at high and low current loads. The results of the paper suggest that the ferrite-assisted solution is the candidate solution for replacing induction motors in variable speed applications
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
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