Showing papers on "Electromagnetic compatibility published in 1997"

Comparison of electromagnetic absorber used in anechoic and semi-anechoic chambers for emissions and immunity testing of digital devices

Abstract: The absorber used in anechoic and semi-anechoic chambers employed for emissions and immunity testing of digital devices is examined. Using reflectivities obtained by the method of homogenization, the advantages and disadvantages of urethane pyramids, twisted-pyramids, wedges, as well as ferrite tiles, ferrite grids, and "hybrid" combinations of urethanes and ferrites, are determined. General reflectivity guidelines are also presented for comparing absorber used for the electromagnetic compatibility (EMC) testing of digital devices from 30 to 1000 MHz.

Frequency Dependent and Transient Characteristics of Substation Grounding Systems

Abstract: In spite of the existence of a number of analytical models aimed for transient analysis of large grounding systems, more detailed analysis of the influence of different parameters on the transient performance of large ground grids subjected to lightning current impulse is not available. This paper presents analysis of the influence of soil conductivity, location of feed point, grid size, depth, conductor separation, ground rods, and shape of the lightning current impulse, on the transient performance of ground grids with sizes ranging from 10/spl times/10 m/sup 2/ to 120/spl times/120 m/sup 2/ and with 4 to 124 meshes. Maximal transient ground potential rise and frequency dependent impedance are analyzed in time and frequency domain, respectively. Computations are made with computer model based on the electromagnetic field theory approach, taking accurately into account frequency dependent characteristics of large ground grids. Instead of usual simple approximations of the lightning current impulse, recorded channel base currents from triggered lightning are used for the time domain analysis.

Full-wave analysis of packaged microwave circuits with active and nonlinear devices: an FDTD approach

Abstract: This paper presents a comprehensive full-wave analysis of packaged nonlinear active microwave circuits by applying the extended finite-difference time-domain (FDTD) method. Based on the approach of using equivalent sources, the device-wave interaction is characterized and incorporated into the FDTD time-marching scheme. As a consequence, analysis of linear and nonlinear properties, including harmonic generation and intermodulation, can be accomplished by employing a large-signal device circuit model. The implementation is first validated by comparing results of FDTD and HP MDS simulation of the circuit without the packaging structure. The analysis then goes beyond the capability of the circuit simulator to include the packaging effect. This analysis is useful in circuit design involving electromagnetic compatibility/electromagnetic interference (EMC/EMI) problems.

EMC Analysis Methods And Computational Models

Abstract: Description: A comprehensive reference on state–of–the–art EMC modeling. The problems of electromagnetic interference are as old as radio wave communication. Only recently, however, has progress in numerical computation permitted the creation of models that help explain the physical phenomena of EM interference and predict and mitigate their effects. These models also invite an approach to solving EMC problems that furthers an understanding of underlying principles. EMC Analysis Methods and Computational Models provides detailed descriptions of the formulation, development, analysis, and use of EMC models. Departing from the rules–of–thumb approach for predicting electromagnetic interference, this book covers every step in the development of computational models––from the electromagnetic topology of the system to the development of coupling, penetration, and propagation models that describe the behavior of energy within the system. Supported by numerous illustrations, it * Covers circuit theory, low–frequency coupling, discrete source radiation, transmission line propagation, EM field penetration through apertures, diffusion, and shielding. * Discusses the approximations necessary in model development and contrasts approximate models with more rigorous models. * Includes exercises that elaborate the theory behind the models and indicate practical applications. * Provides computer programs based on models developed in the text. For practicing engineers, researchers, and graduate students, this book broadens the base of knowledge about the principles of EMC and lays the foundation for future research in the field.

Switching-behavior improvement of insulated gate-controlled devices

Abstract: MOSFETs and insulated gate bipolar transistor (IGBT) devices are increasingly used in electronic circuits due to both their easy driving and ability to handle high currents and voltages at high-switching frequencies. This paper deals with a new driver technique that allows optimization of the switching speed, reduction of the energy losses during the switching time, and limitation of the electromagnetic interference (EMI). First, an analysis of voltage- and current-switching waveforms of gate-insulated devices is performed. Then, a method of controlling voltage and current slopes independently is shown using the "one-cycle" method or a suitable adaptive-driving technique based on a phase-locked loop (PLL) approach. These techniques were adopted in order to allow correct generation of the gate signals regardless of the operating conditions. Finally, practical results of the proposed driving circuit obtained using a single IGBT switch chopper are presented.

Grounding System Analysis in Transients Programs Applying Electromagnetic Field Approach

Abstract: Lightning protection studies of substations and power systems require knowledge of the dynamic behavior of large grounding grids during electromagnetic transients. This paper presents strategies which allow incorporation of complex grounding structures computed using a rigorous electromagnetic model in a transients programs. A novel technique for rational function representation of frequency-dependent grounding system impedances in the EMTP is described. An arbitrary number of feeding points can be modeled as mutual coupling is taken into account. Overvoltages throughout electrical power systems and the transient ground potential rise in the surroundings of grounding structures can be computed.

Wide bandwidth, large AC current probe for power electronics and EMI measurements

Abstract: Current measurements in power electronics or in EMI domains require high-performance probes. These probes must have a very wide bandwidth, be insensitive to electromagnetic interferences, and be able to measure large direct and alternating currents (AC-DC) without distortion. This paper is limited to AC current probes. Various principles are reviewed, in particular those based on the current transformer (CT); their limitations are analyzed, and a solution based on a two-stage transformer are proposed to extend low- and high-frequency performance. It is shown that the use of new magnetic materials, such as the amorphous or the nanocrystalline, can improve large-current low-frequency operations, while preserving the smallest possible probe size. Various solutions are provided to improve high-frequency operations. Different developments are depleted; frequency and time-domain results are presented.

Frequency and transient behavior of grounding systems. I. Physical and methodological aspects

Abstract: In the paper, the author presents a soil electrical model, based on extensive measurements, from very low frequency to 1 MHz, and in a physical criterion to validate measurement results. A methodology and a computational procedure to determine the frequency and the transient behavior of grounding systems, and the effects of such behavior on safety of people and equipment are also presented. This procedure considers, in correct way, soil electrical characteristics and the treatment of electromagnetic behavior of grounding systems, including propagation and attenuation in dissipative media, as it is the case of soil.

Electric railway traction. VI. Electromagnetic compatibility disturbance-sources and equipment susceptibility

Abstract: The railway traction environment contains many noise sources and receivers, and is considered to be EMI unfriendly because of the mixing of power, information and communications signals in space, time and frequency. Railway EMC has received much attention for 30 years following the development of converter-fed traction drives and computerised signalling systems. This article covers systems issues including the fundamentals of electromagnetic coupling, disturbance noise sources and receiver susceptibility. The article discusses EM noise sources in traction systems including: rectifier and transformer substations; track and traction line; vehicles and drives; radiative emissions (RFI); and signalling equipment. The article then discusses track and equipment susceptibility to EMI including: track and traction line impedance; traction drive impedance; track signalling system impedance; and track circuit receivers.

Analytical approximations of interference spectra generated by power converters

Abstract: A detailed knowledge of the interference spectrum produced by power converters is the first step in EMC design. For this reason the amplitude spectrum of typical interference sources is analyzed and discussed. Simple approximations are given which dramatically improve the calculation time and the optimization process of filter designs. Theoretical analysis and measurement results are presented.

A general method for coupling static converters with electromagnetic structures

Abstract: A method allowing coupling of static converters with electromagnetic devices represented by finite elements analysis is presented Special attention is paid to the fact that the state-variable equations of the static converter are calculated automatically These equations are then solved simultaneously with those of the electromagnetic structure, step by step with respect to time

A circuital approach to estimate the magnetic field reduction of nonferrous metal shields

Abstract: The reduction of magnetic fields is a topic of concern to the electric utility industry and the electromagnetic compatibility community. One technique to reduce the magnetic fields is to use metal plates and enclosures for shielding, in addition, knowledge or the loading effect of a conducting structure in close proximity to power cables is needed for estimating power loss. Until now there has not been a simple and efficient method to calculate the low frequency magnetic shielding of, nor power loss caused by, two-dimensional shields. This paper presents a method for the rapid numerical estimation of the magnetic shielding efficiency and power loss of nonferrous metal structures. The method was validated analytically and experimentally.

Frequency and transient behavior of grounding systems. II. Practical application examples

Abstract: In this paper, the authors present the application of the methodology and computational procedures described in part I of this paper to basic practical problems of electromagnetic compatibility, including: the effects of lightning discharges in electrical grounding systems and the definition of risks for human safety; for equipment damage and of noncorrect operation of control and protection schemes; procedures to limit the consequences of lightning; interference, through ground systems, in sensitive circuits, considering frequency dependence of interaction of power equipment with sensitive elements and surge type phenomena; and procedures to limit interference.

Design Guidelines for Shielding Effectiveness, Current Carrying Capability, and the Enhancement of Conductivity of Composite Materials

Abstract: These guidelines address the electrical properties of composite materials which may have an effect on electromagnetic compatibility (EMC). The main topics of the guidelines include the electrical shielding, fault current return, and lightning protection capabilities of graphite reinforced polymers, since they are somewhat conductive but may require enhancement to be adequate for EMC purposes. Shielding effectiveness depends heavily upon the conductivity of the material. Graphite epoxy can provide useful shielding against RF signals, but it is approximately 1,000 times more resistive than good conductive metals. The reduced shielding effectiveness is significant but is still useful in many cases. The primary concern is with gaps and seams in the material just as it is with metal. Current carrying capability of graphite epoxy is adequate for dissipation static charges, but fault currents through graphite epoxy may cause fire at the shorting contact and at joints. The effect of lightning on selected graphite epoxy material and mating surfaces is described, and protection methods are reviewed.

Computing platform architectures for robust operation in the presence of lightning and other electromagnetic threats

Abstract: The electromagnetic environment (EME) produces (is a form of) electrical energy of the same type that is used by electrical/electronic equipment to process and transfer information. As such, this environment represents a fundamental threat to the proper operation of systems that depend on such equipment. For electrical/electronic systems providing functions that can affect the safe flight and landing of an aircraft (level A systems), the EME threat translates to a threat to the airplane itself. When protection against EME effects is being developed, architectural techniques should be applied, particularly to achieve the high margin of safety needed for level A electrical/electronic systems. The computing platform for the aircraft Information Management System (AIMS) used on the Boeing 777 aircraft and Versatile Integrated Avionics (VIA) technology is an example of the application of an architectural philosophy in the design of the digital engine for such aircraft systems. Another is a prototype computing platform for rapid recovery from "soft faults" (upset, momentary interference, etc.).

Investigation of low cost control schemes for a selected 3-level switched mode rectifier

Abstract: Two low-cost modulation schemes are presented for the control of a 3-level switched mode rectifier. One is based on a hysteresis controller and the other on a double ramp comparison. The latter control concept implemented by common PWM ICs yields preferable characteristics for the power interface to telecommunication equipment such as high power density, due to reduced volume for electromagnetic compatibility (EMC) and input current filtering, high control dynamics, low harmonic distortion (THD) and switching losses, which are comparable to those achieved by space vector control, but with less costs and complexity.

Some applications of chaos in power converters

Abstract: Applications are beginning to be found for chaotic power converters. Using the peak current controlled boost converter as an example throughout, the paper reviews the theory of chaos, shows how it may be employed to improve the electromagnetic compatibility (EMC) of power supplies, and presents a targeting scheme that can make a chaotic converter jump rapidly between two stabilised modes of operation.

Electromagnetic field shielding device

Abstract: An electromagnetic field shielding device which is constituted of an electromagnetic field detecting coil (21) which detects an AC leakage electromagnetic field and a parallel resonance circuit (22-24) having a circuit constant which is decided in advance so that the frequency of an electromotive force induced in the coil (21) can be selected as the resonance frequency of the circuit (22-24). When the resistor (24) of the circuit (22-24) consumes energy, the intensities of a magnetic field and an electromagnetic field interlinked with the coil (21) are suppressed.

Electric railway traction. VII. Electromagnetic interference in traction systems

Abstract: This article describes some classic problems of interference in electric railway traction systems together with mitigation and modelling techniques. This article describes some practical noise problems in traction systems, with emissions spanning the complete frequency spectrum. The production of low-frequency (LF) noise from conductive and inductive coupling of currents and fields flowing in the traction system is described in terms of simple circuit and field models. Radio frequency (RF) noise is usually assessed by practical measurement, for which the current state of the art is reviewed. The article is concluded by a summary of the effect of European Community EMI limits.

The measurement of fast transient electromagnetic interference within power system substations

Abstract: Substations are expected to transform and direct electrical power to customers with high reliability, even when exposed to transient electromagnetic interference (EMI) from high voltage (HV) events such as switching, faults and lightning strikes. It is well known that EMI arises from any operation that interrupts or changes an electrical current. During switching operations in substations, very fast, high field transients occur which can adversely affect, amongst other things, secondary equipment in control if it is adequately protected. With increase microprocessor based systems for the monitoring and protection of power equipment, the detection of equipment faults, before they lead to major outages, is possible. The placement of electronic equipment which is, by nature, highly susceptible to electromagnetic interference, within the switchyard EMI environment is becoming more common. This raises the level of concern for the electromagnetic compatibility of such equipment with the EMI environment in which it must operate. Therefore, the environment in which this equipment is placed needs to be fully characterised in terms of electromagnetic interference levels. With this knowledge it is possible to provide adequate protection for electronic equipment and design efficient, effective and reliable control systems. This paper looks at a variety of methods, and their suitability, to characterise the electromagnetic environments in substations.

ESD field penetration through slots into shielded enclosures: a time domain approach

Abstract: This paper presents a time domain approach for the analysis of the coupling between an electrostatic discharge (ESD) current and the internal region of a shielded enclosure with a slot. The application of the equivalence principle allows us to obtain an integro-differential equation for the unknown distribution of the aperture electric field. The numerical solution is obtained by an iterative procedure developed by the method of moments (MoM) in the time domain. The approach is also applied at the case of a transient incident field of a plane wave impinging on the enclosure. The use of proper impulse responses for the space and cavity regions make the model efficient from a computational point of view, without loss in accuracy. Theoretical results are validated by measurements.

Pulsed corona for gas and water treatment

Abstract: The successful introduction of pulsed corona for industrial processes very much depends on the reliability of high-voltage and pulsed power technology and on the efficiency of energy transfer In addition, it is crucial that adequate electromagnetic compatibility (EMC) is achieved between the high-voltage pulse source and surrounding equipment Pulsed corona (15 kW) is generated in a pilot unit that produces narrow 50 MW pulses at 1000 pps The pilot unit can run continuously for use in industrial applications: cleaning of gases (100 m/sup 3//h) or fluids (eg waste water) Various chemical processes, such as toluene removal from an air flow are tested To examine the processes in the reactor, the authors use current and voltage sensors and a fast CCD camera They also developed a model to analyze the VOC conversion Incorporated EMC techniques are based on the successful concept of constructing a low transfer impedance between common mode currents induced by pulsed power and differential mode voltages in signal lines and external mains AC

Near-field characterisation of power electronics circuits for radiation prediction

Abstract: Two methods of computation of the electromagnetic fields radiated by power converters are developed. They permit the calculation of the near field from the topographic implantation, which is necessary in order to verify the correct operation of the control unit. Finally, comparisons of measured and computed electromagnetic fields are reported.

Calibration and use of EMC antennas.

Abstract: The documentation addresses the calibration of electromagnetic compatibility (EMC) antennas in the frequency range 30 Hz to 40GHz. Guidance is given on the assessment of uncertainties in their use for EMC radiated emission measurement.

Design and evaluation of the power and data contactless transfer device

Abstract: The transmission of electrical power and data through rotating interfaces in spacecraft equipment is a common requirement which is frequently mission-critical. The use of slip-ring and roll-ring type units, especially for high rotational rates, presents many drawbacks such as friction torque, electrical noise, high contact resistance, wear, debris and criticality concerning reliability and lifetime. These difficulties may be eliminated by means of a Contactless Transfer Device (CTD). The design, development and testing of such a device is described. This space-compatible Breadboard Model (BM) is capable of transferring over 250 W and 5 Mbps bi-directional digital data. The design accommodates a central axle or pole of up to 55 mm diameter, and may be used in an in-side-in or an in-side-out configuration A modulated subcarrier capacitive technique is used for the transfer of multiplexed data, and a rotating transformer for power-transfer. A modular approach allows the design to be tailored to the needs of specific users, and to allow the option of a fully redundant implementation. The paper presents and discusses the results of an extensive evaluation program which covered functional, electromagnetic compatibility, thermal, torque and vibration testing.

Electromagnetic field in the sea due to an omnidirectional VLF antenna

Abstract: The physical and electrical properties of typical VLF transmitters are described, and new formulas are given for the electromagnetic field they generate on the surface of and at any depth in the sea. These apply to the spherical earth at frequencies in the range 14 ≤ ƒ ≤ 30 kHz. They are useful for distances up to 10,000 km. Special application is made to communication with submerged submarines equipped with horizontal antennas.

Including dielectric loss in printed circuit models for improved EMI/EMC predictions

Abstract: The properties of printed circuit boards (PCBs) pertinent to electromagnetic interference/compatibility (EMI/EMC) are commonly studied using circuit models. This paper describes a method for improving these models by including the effects of frequency-dependent dielectric loss. The approach can be applied to discrete capacitors, microstrips, striplines, power buses, and power planes. The loss terms, which are expressible as frequency-dependent conductances shunting capacitors in the models, can be closely approximated over a wide frequency range as the real part of the driving-point admittance of a resistor-capacitor network. The method is applied to the important case of shunt loss conductance proportional to frequency, but other dielectric classes are as easily treated. An example power bus is analyzed for typical electrical responses, demonstrating the application of this approach, and showing the effect that frequency-dependent dielectric losses can have on the responses.

Conducted and radiated EMI characterisation of power electronics converter

Abstract: With increasing use of switching power supplies in industrial applications and the necessity to respect standards, problems of electromagnetic compatibility have to be solved In order to reduce the number of prototypes, costs and delays, it is necessary to evaluate and to measure the characteristics of the structure For this, a modelling process has been developed to foresee the behaviour of the structure and evaluate its conducted and radiated emissions This process is presented through the study of a buck converter structure Results of the modelling are quite interesting since the wave forms of the structure can be predicted

Analysis and simulation of a high-speed two-phase AC drive for aerospace applications

Abstract: The majority of aerospace high-speed AC drives are high energy density electric motors that employ small diameter and long axial length. These motors are supplied from a three-phase, 400 Hz aircraft supply. Their construction is either a two-pole or a four-pole design using a three-phase stator winding. The paper suggests an alternative drive based on a novel form of two-phase inverter-fed induction motor with magnetic bearings providing the rotor support. The paper develops theoretical equations which model the performance of the two-phase drive and illustrates how the performance can be simulated using numerical methods. A comparison of simulated and experimental results is presented which demonstrates excellent correlation. The benefits of using the two-phase drive for aerospace high-speed applications are discussed and the added advantages of using magnetic bearings are also presented. Since electromagnetic compatibility (EMC) is an important requirement for aerospace drives the results achieved for the two-phase drive substantiate its suitability in this application area.

Design and construction of stripline for measuring electromagnetic immunity of vehicular electrical cables

Abstract: A stripline for radiated susceptibility testing of vehicular components is designed and constructed. The stripline has the field uniformity of /spl plusmn/3 dB in the frequency range from 100 kHz to 500 MHz, and its characteristic impedance is 90 /spl Omega/. It has a high power capability by reason of using a tapered coaxial line instead of the traditional lumped circuit elements as the impedance matching unit.