1,720,962 research outputs found
Prediction of EMI Filter Attenuation in Power-Electronic Converters via Circuit Simulation
Full text linkThis article investigates the conducted-emission (CE) suppression characteristics of electromagnetic interference (EMI) filters used in power-electronic equipment by time-domain circuit simulation. An operational definition of insertion attenuation is introduced by comparing the CE in the absence and in the presence of the EMI filter. For the sake of exemplification, the analysis focuses on switched-mode dc-dc converters. It is shown that the EMI-filter attenuation behaves differently from the standard insertion loss (IL) and exhibits peculiar properties in these circuits. Namely, its response is known at discrete frequencies where the converter generates CE and may strongly depend on the harmonic index so to jump between quite different levels from a harmonic component to the next one, with a pseudoperiodic behavior, which can be related to the duty cycle. This effect is caused by circuit nonlinearity and is partially mitigated if the simulation accounts for two practically relevant aspects: random instability of the duty cycle and resolution bandwidth of the EMI receiver. The dependence of the common-mode (CM) and differential-mode attenuations on the loading conditions and duty cycle is analyzed, and it is shown that linear IL models provide reasonable predictions of CM attenuation only. Finally, experimental evidence of the unveiled phenomena is presented
Approximate Transmission-Line Model for Field-to-Wire Coupling in Arbitrarily Routed Wiring Structures Above Ground
Full text linkIn this article, a comprehensive method for parametric representation of wire trajectories, allowing accurate geometric description of complex and arbitrarily oriented wire bundles, is introduced. This is the starting point to develop a computationally efficient numerical transmission-line (TL) model for predicting the radiated susceptibility of arbitrarily oriented bundles of wires, illuminated by (possibly) nonuniform electromagnetic fields. The proposed method foresees solution of the field-to-wire coupling problem through suitable discretization and sampling of the bundle geometry and the incident electromagnetic field. Differently from previous models, where bundles parallel to ground were assumed, the proposed model allows for arbitrary bundle orientation by exploiting, first, exact projection of the external field onto the bundle direction, and second, evaluation of the actual wire length (instead of the longitudinal one) of each TL section. Accuracy and computational efficiency of the proposed method are assessed versus full-wave simulation for two application examples, involving parabola-shaped and trefoil knot-shaped wiring structures above ground. Although the strong nonuniformity affecting these structures forces TL theory to work very close to its limits, the achieved agreement is satisfactory and the significant reduction of computational times makes the proposed method suitable for approximate yet efficient prediction of radiated susceptibility characteristics of complex wire bundles
Radiated Wideband IEMI: Coupling Model and Worst-Case Analysis for Smart Grid Wiring Harness
No full textThe fast transition from the conventional electrical-energy infrastructures to the Smart Grid demands for an in-depth analysis of risks associated to Intentional Electromagnetic Interference (IEMI). In line with this aim, this work presents an approach for the prediction of the effects of wideband radiated IEMI in wire harness, based on a worst-case criterion. For a specified bandwidth and energy density, the waveform of the electromagnetic (EM) field is optimized so to maximize the peak value of the common-mode voltage induced at cable terminals. This solution depends on the unknown direction of incidence and polarization angle of the EM field. The worst-case rationale is therefore extended to the search for the extreme value of the induced peak voltage, which is reached in specific, unfavorable conditions of incidence and polarization, here investigated. Moreover, the impact of the main geometrical/electrical parameters of the wiring structure (length, height, impedances) is assessed
Review of Clayton R. Paul studies on multiconductor transmission lines
No full textThis paper describes the main scientific contributions of the Prof. C. R. Paul on multiconductor transmission lines in frequency and time domains. Some innovative contributions are also presented stemming from Prof. Paul's work
A New Method Exploiting Partial Image Expansion to Include Substrate and Ground in Dipole-Based Near-Field Models
Full text linkThis work introduces a novel method to include the passive structure of a printed circuit board into an infinitesimal dipole model that is reconstructed from near-field measurement data. Specifically, the proposed approach enables the construction of equivalent models that include dipole sources, substrate, and perfect electric conductor plane. The electromagnetic near-fields of the infinitesimal dipoles in this configuration are estimated through an adaptation of the partial image expansion technique. The proposed method has the capability to provide accurate results for a wide variety of configurations. Furthermore, it can be easily incorporated into existing dipole array optimization workflows with minimal added computational complexity
Enhanced Impedance Measurement to Predict Electromagnetic Interference Attenuation Provided by EMI Filters in Systems with AC/DC Converters
Full text linkDue to the widespread integration of renewable energy sources connected to AC and DC power systems by means of power electronics converters, electromagnetic noise propagates along lines, and metallic earth-return structures. EMI filters are commonly used to mitigate the common mode and differential mode noise at the interface of distribution lines, and their suppression characteristics are usually assessed in standard test setups, the impedances of which are, however, scarcely representative of real-world applications. In this paper, an online, inductively coupled impedance measurement method is proposed. A sensitivity analysis to highlight the benefits of the proposed setup and experimental verification is performed. The proposed method enables non-intrusive impedance measurement in energized systems, including power converters. These measures, in turn, allow the evaluation of modal insertion losses of EMI filters in real-world operating conditions. The three-phase example considered in this study shows significant deviations from manufacturer specifications, thus justifying the need for more advanced estimation techniques
Experimental Proof of Concept for the Correlation of Bulk Current Injection and Radiated Susceptibility Tests for Aerospace Equipment up to 1 GHz
No full textThis work presents the results of an experimental campaign aimed at validating a recently developed alternative radiated susceptibility (RS) procedure based on the use of bulk current injection (BCI). The rationale of such a procedure consists in the injection of common-mode (CM) conducted disturbances in a certain excess over RS, which is quantified by an engineering margin called overtesting (OT). From the standpoint of the test operator, owing to lack of knowledge about the frequency response of the CM impedance of terminal equipment, OT results to be a random variable. However, its statistics was shown to be predictable through theoretical analysis based on circuit modeling. Unlike previous works, where experimental validations relied on simple cables and basic terminal units, a realistic test setup mimicking typical aerospace harness and equipment is here exploited. An extensive test campaign was carried out to collect data sets for the estimation of the cumulative distribution function of OT. Results corroborate the validity of the proposed approach up to 1 GHz
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
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