1,721,045 research outputs found
Shielding effectiveness of multilayered shields for magnetic field nonsinusoidal sources
No full textThe magnetic field generated by a nonsinusoidal periodic source is shielded by a planar infinite multilayered shield composed of high permeability and high conductivity materials. By means of a transform analytical approach the shielding effectiveness is calculated
A solution to the problem of determining X-points in magnetic induction fields
No full textA procedure which exploits a sufficient condition for determining X-points in quasi-static magnetic induction fields characterized by traditional or axisymmertical geometry is presented. The validity of the procedure and usefulness of the theorem are illustrated via a numerical example
Lumped circuit models of PCB lands in switching converters
No full textThis paper deals with circuit models that can be used to represents printed circuit lands of Switched-ModePower Supplies (SMPS). These circuit models are useful forthe prediction of the electromagnetic emissions radiatedfromsuch converters. Representations of SMPS built on printedcircuit board (PCB) in terms of lumped circuits and lumped-circuit iterative structures are considered and comparedunder different SMPS load conditions. These circuit modelsare also validated against measurements
Frequency dependence of shielding effectiveness of multilayered magnetic shields
No full textAn analysis of magnetic shielding effectiveness of multilayered structures versus frequency is presented. It is shown that the quasistatic field approximation is accurate until several MHz depending on the source-to-observation-point distance, characteristic dimensions of the source, and physical and geometrical properties of layers. The accuracy is assessed by means of comparisons with the solution of the wave equation in a wide frequency reange. This study can be useful for the shield design and also for predicting the shielding effectiveness of multilayered magnetic shields in a source of non sinusoidal periodic magnetic fields
Radiated emissions from switching converters
No full textThis paper presents an attempt to solve the problem of predicting radiated emissions from a Switched-Mode Power Supply (SMPS). The model for the emission is based on the assumption that each conductor (land) of the printed circuit board (PCB) of which the SMPS is composed can be considered as a Hertzian dipole. The currents in the lands are determined by means of approximate lumped circuits connected in different ways and using a circuit simulator like PSPICE
ESPRESSIONE IN FORMA CHIUSA DELL’IMPEDENZA EQUIVALENTE DI UN SISTEMA DI TRASMISSIONE DI ENERGIA ELETTRICA CHE IMPIEGA UN ARRAY DI RISONATORI MAGNETICAMENTE ACCOPPIATI
No full textSurvey of models and reference data for prediction of e.m. field emissions from electrical machinery
No full textThis paper addresses the problem of robust and accepted methods for the estimation of electromagnetic emissions from electrical machinery and more extensively, Adjustable Speed Drives. Machine emissions can also be considered for diagnostic purposes. In particular, the analysis of the electromagnetic signature of the machine is used for the detection of partial short-circuits inside windings or mechanical unbalancing faults. The focus is on consistent reference data and readily applicable models rather than on theoretical treatment, since the environment in which this apparatus operates is deemed by high levels of electromagnetic noise and propagation conditions far from ideal ones
Magnetic Shielding of Long Wires with Multilayered Cylinders
No full textAn efficient approach for evaluating the low-frequency magnetic shielding effectiveness of long cylindrical multilayered structures enclosing a system of straight wires is presented. No restriction is imposed on the number of both conductors and shielding layers and on the conductor locations inside the shell. The quasi-static shielded magnetic field is related to the unshielded one by means of a transmission matrix whose elements depend only on the geometry and material properties of each layer. the method is extremely flexible and the ruselts obtained are in good agreement with those derived from a finite element analysis
Analysis of design solutions for a GTEM cell
No full textGigahertz Transverse Electromagnetic (GTEM) cells are among the standard environments used for radiated emission and immunity tests on electrical and electronic equipment and systems at frequencies from DC up to over 1 GHz. In this paper, an analysis of different cross sections for a GTEM cel is presented. The aim of this work is to find possible new shapes for GTEM cells suitable to obtain a more uniform electric field distribution inside an unloaded cell
Investigation on the Shielding Effectiveness Properties of Electrically Conductive Textiles
No full textThe usage of electrical and electronic devices that operate at high frequencies has grown rapidly in recent years, as well as the increased perception and awareness of new possible electromagnetic interference threats to equipment and people. In addition, it is worthy of notice that in many countries there exist several mandatory regulations and standards that regulate emissions and immunity of equipment and exposition of personnel and people to electromagnetic fields. Therefore, there is an increasing need of materials capable to adequately shield incident electromagnetic fields. Traditional shielding materials such as homogeneous metals have indeed suitable properties as regards the shielding effectiveness (SE); however, their use is mainly limited by weight and cost. Alternative materials such as conductive polymer composites have been developed and proposed to replace metals in many applications, e.g., enclosures for the electrical and electronic industry, due to their rather good performances in terms of shielding effectiveness and electrostatic discharge. Nevertheless, other applications may be difficult because of their rigidity. Conductive textiles represent indeed an interesting development of what has been done with fabrics in the last two decades to convert them into electromagnetic shields. Due to their flexibility and conformability, fabrics with reasonable electrical and magnetic properties are attractive for various applications, from electromagnetic shielding to electrostatic discharge, and can be used in civil, commercial and military environments. As there is no precise method for calculating the SE of these materials, testing remains the preferable option. In particular, this paper is devoted to investigate which basic mechanisms are responsible for the major part of the shielding of conductive textiles by means of measurement of the shielding effectiveness. Both woven and nonwoven textiles are examined and the results for textiles of different thickness, nickel amount and fabric geometry are compared
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