Search

The relation between ageing and space charge is a hot area, but there is little direct evidence. In this paper, oil-paper samples were exposed to 20-kV/mm DC electrical field, 130°C temperature or both 20-kV/mm DC electrical field and 130°C temperature separately. Charge transport through them was analyzed at intervals by the pulsed electroacoustic (PEA) method. We find that the quantity of trapped charge increases with stressing durations, no matter what kind of stress oil-paper is exposed to. That indicates that energy release through space charge movement, such as charge trapping/detrapping and recombination, is another reason for traps generation besides deterioration caused by thermal ageing. However, because the difference in cellulose degradation mechanism among them, charge transport dynamics are thereby different under different stressing conditions. Space charge accumulates faster inner electrothermally stressed oil-paper than that inner another two kinds of oil-paper, and the sign of trapped charge is positive if oil-paper is electrically or electro-thermally stressed. The latter behavior is discussed in terms of electromagnetic dynamics due to cavity within oil-paper once there is external electric field. [ABSTRACT FROM PUBLISHER]

The objective of this special issue is to publish papers related to the basic physics of Electromagnetism in thecontext of radio wave propagation, see editorial of Part I. [ABSTRACT FROM AUTHOR]

Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers. [ABSTRACT FROM AUTHOR]

Presents the recipients of the Harold A. Wheeler Applications Prize Paper Award. [ABSTRACT FROM PUBLISHER]

The latest of a series of classified lists of power system relaying references, begun in 1927, is presented. This bibliography is in continuation to the bibliographies of relay literature, which were published previously and are contained in the following volumes of the IEEE Transactions: [ABSTRACT FROM AUTHOR]

This paper analyses the inherent difficulties in measuring the horizontal electric field from lightning and proposes some solutions to mitigate the contamination effect of the overwhelming vertical electric field. The analysis is carried out with a set of time-domain equations for the calculation of the electromagnetic fields from lightning. As these equations are scattered in several publications, in this paper they are compiled and presented in a harmonized form. Moreover, one new expression for the vertical electric field slightly below the ground surface is presented. It is shown that the horizontal electric field at the surface of lossy ground can be measured with minimum disturbance caused by the vertical electric field if the field sensor is placed slightly below the ground surface. This paper also shows that the horizontal electric field above the ground surface could be measured with the help of a pair of field sensors conveniently arranged so that the influence of the vertical electric field on the measurement is cancelled. [ABSTRACT FROM AUTHOR]

In this paper, we derive formulas that calculate the impedance parameters (Z-parameters) of multiple antennas near objects to analyze wireless power transfer. Furthermore, we propose a method to calculate the impedance parameters of antennas, the maximum power transfer efficiency, and the optimum load impedance of a wireless power transfer system using equivalent current that generate the same electromagnetic field as that generated by an antenna in transmitting mode. [ABSTRACT FROM AUTHOR]

This paper proposes a way to represent the anisotropic nonlinear superconducting properties using a discrete model for magnetization with the corresponding critical parameters, equivalent to the Power Law model for currents. This simplified model makes it possible to analyze magnetic systems with superconducting elements in a stationary mode, which reduces the calculation time. Using of proposed model is demonstrated by the calculation of force interactions between high-temperature superconducting (HTS) samples and permanent magnet in zero-field-cooling (ZFC) and field-cooling (FC) modes. HTS bulks in the form of a prism and stack made of HTS tape are considered. The calculation of the electromagnetic field was carried out using the method of integral equations for field sources. The data of calculations are compared with the results of experimental studies. [ABSTRACT FROM AUTHOR]

The topology and breakpoints of the grounding grid will directly affect its working performance. This paper proposed a resistivity reconstruction method based on magnetic detection electrical impedance tomography (MDEIT) to measure the topology and breakpoints of the grounding grid. First, this paper describes the forward problem of grounding grid detection in MDEIT, and calculates the magnetic-field distribution above the grounding grid. Then, the resistivity reconstruction method based on the least squares method is proposed. Finally, this paper verifies the feasibility of the proposed method by a numerical example, which shows that the proposed method can be applied to measure the topology and breakpoints of the grounding grid. [ABSTRACT FROM AUTHOR]

This paper presents a research work on the electromagnetic loss modeling and demagnetization analysis for a high-speed permanent magnet machine (HSPMM). The iron loss is estimated by improved modeling considering harmonics and rotational magnetic field effects to achieve high precision; rotor eddy current loss is researched and comprehensively investigated using finite-element method (FEM). The auxiliary slot and PM beveling are also proposed to reduce the rotor eddy current loss for machine at high-speed operation. Temperature-dependent PM demagnetization modeling is utilized in HSPMM FEM analysis to investigate machine performance due to temperature variation, while optimized rotor structures are proposed and comparatively researched by FEM to improve the machine anti-demagnetization capability in harsh conditions. The HSPMM temperature is estimated based on the calculated loss results and machine computational fluid dynamic modeling. Experimental measurements on the prototype machine verify the effectiveness of the machine electromagnetic and thermal modeling in the paper. [ABSTRACT FROM AUTHOR]

This paper proposes an electromagnetic field computation method using an interpolation method with sigmoid functions. This method is useful for approximating and developing a 3-D electromagnetic field model. Particularly, the authors have been researching a spherical motor for a robotic eye. The spherical motor has a spherical air-gap unlike the radial air-gap motor or the axial air-gap motor. The spherical motor proposed in this paper realizes three degrees-of-freedom movements with only one motor. As the spherical motor has a complicated coil structure, the 3-D FEM would be essential for calculating torque while the rotor is tilted. However, 3-D FEM requires much computation time and a huge memory capacity to store the results. The electromagnetic field is rapidly calculated using an interpolation torque function proposed in this paper. The improvement of the spherical motor due to our method is verified through experiment, the results of which are compared with simulation data. [ABSTRACT FROM AUTHOR]

The article calls for papers related to microwave theory for the periodical.

In this paper, a novel switched reluctance motor with two magnetically dependent stator and rotor sets (TMDSRM) is proposed and tested. The novelty of the TMDSRM is that there is an assistant exciting winding (short for exciting winding), which is placed between the two-stator sets and can be energized by controllable dc current to boost the air-gap flux density and to improve the output torque and torque density. What deserves to be mentioned the most is that the air-gap flux density is compensated when armature winding is in commutation because of the exciting winding carrying dc current and being permanently energized, and thus, the torque ripple is reduced. This paper describes the magnetic structure and the principle of the proposed motor in detail. Moreover, finite-element analysis has been carried out to investigate the influence of exciting field on electromagnetic torque of the motor. A prototype TMDSRM is manufactured, and the experimental results are presented. [ABSTRACT FROM AUTHOR]

Pulsed alternator (PA) is a kind of high-power pulsed supplies widely applied in the field of electromagnetic (EM) launch. Over the past decades, the self-excited air-core PA is widely studied, but it has the disadvantages of poor heat transfer and high electric field loss. The hybrid excitation PA combined with the advantages of electric excitation and permanent magnet excitation PA, and the output voltage of armature winding can be adjusted by the electric field current. This paper presents double-electric-excitation hybrid excitation compensated PA (DEE-HECPA). In order to improve the adjustable performance for the output voltage of HECPA, the rotor structure is changed and double excitation coils are used in PA. In this paper, the equivalent magnetic circuit model for hybrid excitation region is established and the air-gap flux density is calculated. The dimensional parameters are calculated by the special EM design method for PA, the characteristics of electric excitation are verified by finite-element analysis, and the characteristics of output current for DEE-HECPA are analyzed. The research results demonstrate that DEE-HECPA is a feasible topology for PA. [ABSTRACT FROM AUTHOR]

Electromagnetic pulse forming (EMPF) is an attractive manufacturing method using pulse power techniques. Temperature rise of the work piece is usually neglected in previous studies because the forming process is regarded as a cold process. Nevertheless, the temperature rise (if not high) also has influence on the forming process. It is important to study the temperature rise for exploring the related law in the process of EMPF. In this paper, the thermal effect in the process of EMPF, caused by the joule heating generated by the high current and the plastic work produced by the plastic deformation of the work piece in the forming process, is discussed though simulations and experiments. A finite-element simulation coupled with the electromagnetic field, plastic mechanics, deformed geometry, heat transfer, and thermal expansion based on COMSOL multiphysics is established to show the detailed thermal effect in this process. The relationship between parameters of work piece and the thermal effect has been analyzed by comparing different materials and thicknesses of work pieces. The simulation results show that the temperature of work piece has changed because of the thermal effect. A high-current pulse generator has been developed for the experiment of EMPF to verify the results of simulations. This paper describes the forming experiments of different materials and thicknesses. And the experimental results verify that the materials and thickness of work piece affect thermal effect during the process of EMPF. Compared with the Joule heating, the plastic work is the main cause of the thermal effect. Moreover, the thermal expansion caused by temperature rise could affect the forming results and material property. [ABSTRACT FROM AUTHOR]

This paper presents a new spiral inductor based on substrate integrated suspended line (SISL) technology. SISL is a new type of transmission line, which has many merits, such as low loss, low dispersion, and self-packaging. New series of spiral inductors based on this advanced SISL platform is proposed and modeled in this paper. SISL to microstrip transition is designed for the measurement of the SISL inductor, and an open-short deembedding method is introduced for the accurate extraction of inductor network parameters. A $\pi$ equivalent circuit model is applied for modeling of the SISL inductor and new double-sided SISL (DSISL) inductor, and the accurate empirical expression of inductance L$ , peak quality factor Q_{\mathrm {max}} , and self-resonance frequency are given. The typical relative error of each expression is less than 8%. Finally, a new DSISL inductor with patterned substrate is proposed, which can significantly improve the quality factor up to 40%. Simulation and measurement results show good agreement. [ABSTRACT FROM PUBLISHER]

Water is damaging for power transformers since it accelerates aging processes, reduces dielectric margin, decreases partial-discharge inception voltage, and, therefore, increases the probability of unexpected failures. Taking into account that power transformers are the most expensive equipment in an electrical plant and that the electrical supply guarantee is closely related to their reliability, it seems clear that transformer water content is a variable that must be kept under control. Since water is a byproduct of aging reactions in cellulosic insulation, the amount of water contained in a transformer usually increases from levels below 0.5% in weight, after its manufacturing, to levels of 6% in weight at the end of its life. However, it is not unusual to find high humidity levels in not so-old transformers, for example, in those that have been subjected to repairs in field. These days, some techniques are available to dry transformers in the field. Most of these methods achieve proper drying of transformer oil, but a great amount of water usually remains in cellulosic insulation and water in oil rises slowly some months after finishing the process. In these cases, drying treatments, which are very expensive; would have limited effectiveness. In this paper, a finite-element study is presented that analyzes different field-drying methods that are currently widely used. The efficiency of these methods will be studied and compared, and recommendations about drying parameters will be given. [ABSTRACT FROM AUTHOR]

Introduces a series of articles on nonthermal medical/biological treatments using electromagnetic fields and ionized gases.

With the growing interest in polarization diversity in communications and radar systems, the use of Ludwig’s second and third definitions has become controversial among scientists and antenna engineers. Therefore, this paper is an attempt to clarify some of the ambiguity and confusion caused by these definitions. A detailed comparison of Ludwig’s second and thirrd definitions of cross polarization, as applied to linearly polarized antennas, was performed. The results show that, in the diagonal plane, Ludwig’s second definition leads to a lower cross-polarization level than the third definition for $x$ - or $y$ -polarized current sources. For a Huygens source, by Ludwig’s third definition, the radiation pattern has a lower cross-polarization level than that obtained by Ludwig’s second definition. For some applications, the antenna is usually placed in the $y{z}$ plane. Therefore, new polarization bases are proposed according to which the source is used as a reference, and also on how this source is oriented in the $y{z}$ plane. To complement the theoretical framework demonstrated in this contribution and to provide readers with a better and simpler understanding of the cross-polarization definition, the analysis of several practical antennas for diverse applications was presented. Numerical and measured radiation patterns of wire and printed dipoles, rectangular patch, pyramidal horn, and open-ended rectangular waveguide (OEWG) antennas were investigated according to the polarization formulations presented in this paper. In addition, a dual-polarized element and a dual-polarized active phased array at broadside were utilized to generalize the application. [ABSTRACT FROM AUTHOR]

Space charge distribution is a valuable indicator of ion flow field and is widely utilized to assess electromagnetic environment for transmission line. The finite-element method (FEM) is widely used to solve this problem. However, Kaptzov assumption in FEM assumes that onset voltage is unchangeable after corona occurs, which does not tally with the actual situation. This paper adopted the finite-element iteration method (FEIM), which uses empirical formula instead of assumptions to calculate the charge density. The surface field intensity is not constant in the empirical formula because the empirical formula takes the effects of space charge on surface field into consideration. So this is more consistent with actual situation. In order to verify the accuracy of the algorithm, sound pulse method is applied to measure the charge density around the conductor in the laboratory. Simulation results show that the charge density obtained in this paper agrees with the data in the experiment, which verifies the validity of the empirical formula for calculation of space charge density. Compared with a method considering Kaptzov assumption, FEIM is closer to the experiment in area around conductor line and near the ground. This indicates that empirical formula in FEIM is more effective than Kaptzov assumption in these two domains. [ABSTRACT FROM AUTHOR]

Accurate and simple magnetic material behavior law is necessary to correctly model complete electromagnetic systems. In this paper, a new formulation based on the scalar quasi-static hysteresis Preisach model extended to dynamic behavior using fractional derivation dynamic contribution is proposed. The fractional contribution is solved using convolution which highly reduces the numerical issues. The order of the fractional derivation provides a new degree of freedom and allows to correctly obtain simulation results on a very large frequency bandwidth. By using such formulation, space discretization techniques (finite differences, finite elements) are avoided which are highly space and time consuming while keeping the global simulation results precise. The numerical implementation of the problem and some experimental validations are shown in this paper. [ABSTRACT FROM AUTHOR]

This paper proposes an improved figure-of-eight coil for transcranial magnetic stimulation (TMS) by using the magnetic resonant coupling (MRC) effect, aiming to improve the treatment effect for psychiatric disorders. The proposed MRC-based figure-of-eight coil consists of two reverse-winding resonance coils, which embraces two series-connected source coils, respectively. Different from conventional figure-of-eight coils, the proposed topology can produce the resonant electromagnetic field to accumulate the stimulation energy. In such ways, the improved TMS system can effectively enhance the stimulation focality and depth while significantly reducing the requirement of the power supply, thus improving the safety as well as facilitating the miniaturization and portability. Last, this paper gives the simulated and experimental results to verify the theoretical analysis, which can further illustrate the feasibility of the proposed MRC-based figure-of-eight coil for TMS systems. [ABSTRACT FROM AUTHOR]

The densification of wireless infrastructure to meet ever-increasing quality of service (QoS) demands, and the ever-growing number of wireless devices may lead to higher levels of electromagnetic field (EMF) exposure in the environment, in the 5G era. The possible long term health effects related to the EMF radiation are still an open debate and requires attention. Therefore, in this paper, we propose a novel EMF-aware resource allocation scheme based on the power domain non-orthogonal multiple access (PD-NOMA) and machine learning (ML) technologies for reducing the EMF exposure in the uplink of cellular systems. More specifically, we use the K-means approach (an unsupervised ML approach) to create clusters of users to be allocated together and to then strategically group and assign them on the subcarriers, based on their associated channel properties. Finding the best number of clusters in the PD-NOMA environment is a key challenge, and in this paper, we have used the elbow method in conjunction with the F-test method to effectively control the maximum number of users to be allocated at the same time per subcarrier. We have also derived an EMF-aware power allocation by formulating and solving a convex optimization problem. Based on the simulation results, our proposed ML-based strategy effectively reduces the EMF exposure, in comparison with the state-of-the-art techniques. [ABSTRACT FROM AUTHOR]

Wind turbines (WTs) can beseriously damaged by lightning strikes and they can be struck by a significant number of flashes. This should be taken into account when the WT lightning protection system is designed. Moreover, WTs represent a path for the lightning current that can modify the well-known effects of the lightning discharge in terms of radiated electromagnetic fields, which are a source of damage and interference for nearby structures and systems. In this paper, a WT struck by a lightning discharge is analyzed with a full-wave modelling approach, taking into account the details of the WT and its interactions with the lightning channel. The effects of first and subsequent return strokes are analyzed as well as that of the rotation angle of the struck blade. Results show that the lightning current along the WT is mainly affected by the ground reflection and by the reflection between the struck blade and the channel. The computed electromagnetic fields show that, for subsequent return strokes, the presence of a WT almost doubles their magnitude with respect to a lightning striking the ground. Such enhancement is emphasized when the inclined struck blade is considered. [ABSTRACT FROM AUTHOR]

This paper presents a new theory for analyzing the leaky-wave (LW) mechanism supported by planar metasurfaces (MTSs) described by continuous, anisotropic, nonuniform, locally periodic boundary conditions (BCs), and excited by a vertical dipole at the interface. These BCs well represent a dense distribution of subwavelength metal patches of infinitesimal thickness, printed on a grounded slab. We denote succinctly this theoretical formulation as flat optics for LWs. This formulation is based on an adiabatic, asymptotic form of the Floquet theorem, introduced here for the first time. The adiabatic Floquet-wave analysis allows for: 1) describing the mechanism of global interaction between the cylindrical surface wave (SW) launched by the dipole and the modulated MTS; 2) introducing a generalized curvilinear-wavefront LW field that can be used for controlling the radiation-pattern shaping; 3) describing the local and global transfer of energy from SW to LW; 4) establishing an analytical relationship between the aperture field polarization and the anisotropic parameters of the MTS and 5) between the leakage parameter $\alpha $ and the MTS modulation index. Concerning the latter point, a closed-form formula for $\alpha $ is introduced, which allows for unprecedented control of the aperture field amplitude. The theoretical results are successfully validated by comparison with a full-wave analysis, showing impressive accuracy. In a companion paper published in this Journal issue, the present theory is used for the synthesis of a large class of planar aperture antennas. [ABSTRACT FROM AUTHOR]

Three-phase nonoverlapping stator wound-field synchronous (NSWFS) machines employing salient pole rotors are proposed in this paper. Based on the optimized design, the influence of rotor pole number on the proposed machine is investigated. According to 2-D finite-element analysis (FEA), it is found that the proposed machine shows higher torque density and lower torque ripple compared with the existing NSWFS machines. The operation principles of the proposed machine under different pole numbers are presented and compared in this paper. The FEA-predicted back electromotive force, cogging torque, and static torque of NSWFS machines are validated by experiments made on the prototypes. [ABSTRACT FROM AUTHOR]

Self-integrating Rogowski coil has been widely used for measurements of pulsed currents from nanosecond timescale to microsecond timescale in pulsed power systems. Appropriate designs of coil’s structure are vital to high-frequency response. This paper proposed a new structure of Rogowski coil so as to provide a better response to fast pulsed current. Four Rogowski coils with different structures were tested in three different platforms. Experimental results showed that the hybrid Printed Circuit Board Rogowski coil had the best performance in this paper, which could respond to square waves with fronts of $\sim 2$ ns and had a sensitivity of 0.585 V/kA. The designed maximal peak current was 100 kA. [ABSTRACT FROM PUBLISHER]

Soil conductivity and permittivity have a substantial influence on lightning-electromagnetic transients in power system. In this paper, lightning-induced voltages are computed on a multi-conductor overhead line due to nearby first and subsequent return strokes. Besides, this study considers the longitudinal complex inductance of the line due to the penetration depth of electromagnetic fields through finitely conducting ground as well as the frequency dependent soil parameters using the finite-difference time-domain method. Various case studies in light of variations of return stroke velocity, line height, and soil conductivity are explored for thoughtful investigations. The obtained results reveal that the influence of this complex inductance on peak values of lightning induced voltages changes with varying the return stroke velocity. Also, the frequency dependence of soil parameters markedly impacts the computed lightning-induced voltages particularly for poor soil conductivity. [ABSTRACT FROM AUTHOR]

In this paper, two novel double-sided hybrid-excitation flux-reversal linear motors (DSHEFRLM) with the surface (S-) and interior (I-) permanent-magnet(PM) arrangements are proposed and comparatively investigated. The proposed motors feature an asymmetrical double-sided primary configuration which enables the armature and field excitations to be placed separately. Through 2-D finite-element method (FEM), two motor structures with different slot/pole combinations are optimized, and then, the magnetic fields and electromagnetic performances are calculated, including inductances, no-load flux linkage, thrust characteristics, and PM demagnetization capability. By comparison, it is found that S-DSHEFRLMs show larger thrust density while I-DSHEFRLMs exhibit superior flux-adjusting capability. Finally, these predicted results are validated by 3-D FEM. [ABSTRACT FROM AUTHOR]

On-wafer probing with ground–signal–ground (GSG) probes contributes a variety of side effects, which are related to the measured line type, the carrier material, the layout with the neighboring structures, and the probe. Thus, the size and shape of the probe together with the measured line type and the neighboring circuits influence the quality of the calibrated measured result. This paper presents corresponding results when using the multiline-thru-reflect-line (mTRL) calibration, which is commonly accepted as one of the most accurate calibration algorithms, and concentrates on the impact of the probe construction together with neighboring elements, for the most common planar transmission lines, coplanar waveguides (CPWs), and thin-film microstrip lines (TFMSLs). For the first time, design guidelines with regard to the layout, the measurement environment, and the construction of the probes are given. [ABSTRACT FROM AUTHOR]

This paper proposes a novel single-stage double-layer saddle multipole field electromagnetic launcher (SSDFEL), which combines the characteristics of reconnection gun to achieve simultaneous linear acceleration and gyroscopic stabilization of the projectile. Since the saddle driving coils are divided into two layers, the magnetic field density inside the launcher is enhanced. The eddy current induced on the inner and outer surfaces of the projectile is greatly changed by the hollow cylindrical projectile with six symmetrical vertical slots twisted at a certain angle, and the projectile is simultaneously propelled to perform rotation motion and linear motion. In this paper, the electromagnetic field finite-element software is used to simulate and calculate this model. The simulation results indicated that the double-layer driving coil distribution has larger axial acceleration force and bigger circumferential torque than that of the single-layer driving coil distribution, the energy conversion efficiency has also been obviously increased, and there is an optimal initial twisted angle, which accelerates the projectile to the peak of rotation. To verify the results, an SSDFEL was established and tested. The experiment results confirm that the rotation performance can be affected by the initial twisted angle and a better launching effect is achieved than a single-layer distribution. In general, the experimental results are in agreement with the simulation results. [ABSTRACT FROM AUTHOR]

The air circuit breaker (ACB) is required to switch off the short current at various frequencies in the permanent magnet wind power generation system. The movable contact of ACB consists of multiple parallel contacts, and the arc will be ignited when the short-circuit current appears. This paper focuses on the effect of frequency on arc motion in multiple parallel contacts’ system. A 3-D magnetohydrodynamic (MHD) model of a multiple parallel contacts’ structure is built. In this model, the anode consists of five parallel contacts. The difference in voltage between the near-anode layer and the near-cathode layer is considered. The nonlinear B–H curve of the splitter plate is taken into account. The time-varying electromagnetic field induced by the current loop including electrodes and arc column is calculated. The arc evolution process and effect of frequency on arc motion in multiple parallel contacts’ system are analyzed by the arc voltage and the current density distribution. This paper is expected to provide the theoretical references for the optimal design of arc quenching chamber of ACBs. [ABSTRACT FROM AUTHOR]

This paper addresses the question of how much information can be transmitted reliably over a wireless channel. It is shown that the limit of this mode of transmission is dictated by the amount of information that an electromagnetic field is capable of carrying. The methodology for the analysis of this problem is along the theory developed by Kolmogorov. This allows one to quantify the amount of information that can be transmitted by a wireless communication system taking into account the physical limitations governed by the laws of electromagnetism. Starting from the results related to the amount of information carried by an electromagnetic field, a novel antenna synthesis technique that simultaneously takes into account the requirements of information and antenna theory is introduced and applied to the synthesis of multiantenna systems. [ABSTRACT FROM AUTHOR]

In this paper, a novel type of dynamically tunable attenuator based on graphene is proposed. This type of attenuator is composed of one or two graphene sandwich structures (GSSs) and a microstrip line. The GSSs are spread on the substrate of microstrip line near the signal strip along the direction of propagation to dissipate electromagnetic field. By the application of biased voltage, the surface impedance of graphene can be tuned, and consequently, the insertion loss of microstrip line can also be adjusted while the return loss maintains relatively low level. A transverse equivalent network and a closed form of attenuation of each attenuator are also proposed, which can be utilized to analyze the performance of attenuator with different critical parameters of graphene in detail. According to the analysis, there is a maximum value of the attenuation as the surface impedance of graphene rises from 0 to $3000~\Omega /\Box $. As an example, a prototype of each tunable microstrip line attenuator operating at gigahertz frequencies is fabricated and measured. The fabricated attenuator present favorable attenuation ranges from 3 to 15 dB, at the operating frequency from 9 to 40 GHz, and with a stable wideband attenuation corresponding to bias voltage changing from 0 to 4.0 V. [ABSTRACT FROM AUTHOR]

In the process of electromagnetic launch, the melting on the armature surface tends to change the state of the armature/rail (AR) contact. Once the contact state is damaged, transition will appear easily. For this reason, it is necessary to analyze the factors affecting the melting characteristics of the armature surface. According to the Reynolds equation listed for the liquid metal film (LMF) on the AR contact interface, and by coupling the temperature, stress, and electromagnetic fields, this paper presents a thermoelastic magnetohydrodynamic model, which is used to analyze effects of the current waveform, and the length and angle of the armature tail on the surface melting rate and LMF thickness. The results show that for the same armature, if we want to achieve the same velocity within the same time range, the smoother the current waveform, the slower the surface melting rate and the thinner the minimum LMF thickness, and that for armatures of different key dimensions, in a certain range, the longer the armature tail, the slower the surface melting rate, but the larger the total melting amount and the thicker the minimum LMF thickness, and that the angle of armature tail has little effect on melting characteristics of the armature surface. What has been done in this paper is of great importance to improving the AR contact state and optimizing the performance of the electromagnetic launcher. [ABSTRACT FROM AUTHOR]

This paper presents a study of the multipactor effect in a partially dielectric-loaded rectangular waveguide. To obtain the simulations presented in this paper, a detailed analysis of the dynamics of the electron inside this waveguide has been performed, taking into account the radio frequency electromagnetic fields propagating in the waveguide and the dc electric field that appears because of the charging of the dielectric layer. This electrostatic field is obtained by computing the electric potential produced by an arbitrary charge distribution on the dielectric layer in a dielectric-loaded waveguide. The electron trajectory is then found by numerically solving the equations of motion. The results obtained show that multipactor discharges do turn off by themselves under certain circumstances when they occur in such dielectric-loaded waveguide. [ABSTRACT FROM AUTHOR]

The article presents the authors' views on issues discussed at the 2005 Conference on the Computation of Electromagnetic Fields, which was held on June 26-30, 2005. The conference was important for the scientific community working in computational electromagnetics. It mainly dealt with numerical computation of electric fields. A total of 680 two-page papers were submitted for the conference. The authors tried to maintain a fair and uniform evaluation scale among reviewers, whose nationality differed from that of the authors.

This paper presents a detailed modeling and analysis regarding the dispersion characteristics of multilayered open coaxial waveguides or cables. The electromagnetic model is based on a layer recursive computation of axial-symmetric fields in connection with a magnetic frill generator excitation that can be calibrated to the current measured at the input of the cable. The layer recursive formulation enables a stable and efficient numerical computation of the related dispersion functions, as well as a detailed analysis regarding the analytic and asymptotic properties of the associated determinants. Modal contributions as well as the contribution from the associated branch-cut (nondiscrete radiating modes) are defined and analyzed. Measurements and modeling of pulse propagation on an 82-km-long HVDC power cable are presented as a concrete example. In this example, it is concluded that the contribution from the dominating axial-symmetric transverse magnetic mode is sufficient, and that the contribution from the branch-cut is negligible for all practical purposes, and in particular if the exterior domain is lossy. The main contribution of this paper is to provide the necessary modeling and analysis tools for a quantitative study of these phenomena. [ABSTRACT FROM PUBLISHER]

In this paper, a unique meshless method using the radial point interpolation method (RPIM) for the analysis of electromagnetic fields is proposed. In electromagnetic field analysis, treatment of the interfaces between different mediums is important. In this paper, a unique approach is proposed, which is to consider the material constants to be functions of space. Based on this condition, the governing equation of the electromagnetic field is derived and the equations are discretized using the RPIM. The proposed method is applied to eddy current problems, and the results are discussed. [ABSTRACT FROM PUBLISHER]

In recent years, microgrid technologies have gained considerable interest, where a common dc-bus is generally used to interconnect multiple power sources. The existing technology of common dc bus-based direct integration of multiple sources has some critical problems, such as isolation and the requirement of additional control circuit for voltage imbalance and common mode. A common high-frequency magnetic bus (instead of the common dc bus) is proposed in this paper to overcome the limitations and complications of the existing technology of dc bus-based direct integration of multiple sources. In this paper, an extensive investigation on electromagnetic performance of advanced magnetic materials (amorphous and nanocrystalline alloys) is presented. The design process of an efficient and compact high-frequency common magnetic bus for integration of multiple power sources is also discussed. The new technology will be a fundamental component for the future grids to interconnect various sources magnetically, providing an inherent solution to voltage imbalance and isolation problems. [ABSTRACT FROM AUTHOR]

This paper presents a novel nonintrusive protection scheme for fault classification of power transmission networks in a wide-area measurement system using fault information for decision making. The protection scheme is a noncommunication without global positioning system as it depends completely on locally measured currents for the nonintrusive fault monitoring (NIFM) using the power-spectrum-based hyperbolic S-transform (PS-HST). In this work, the HST is used to extract the high-frequency components of the current signals generated by an electric fault. To effectively select the HST coefficients (HSTCs) representing fault transient signals with increasing performance, a power spectrum of the HSTCs in different scales calculated by Parseval's theorem is proposed in this paper. Finally, back-propagation artificial neural networks and PS-HST are used to identify fault classes in power transmission networks. The proposed method is tested for different breaker on/off conditions by simulations using electromagnetic transients program software. The results obtained have proved that the proposed method is promising and demonstrate a high success rates and reliability for considering different fault resistances and inception times in NIFM applications. [ABSTRACT FROM AUTHOR]

Dynamic operational behavior (DOB) of electrical machines can cause effects that are difficult to describe and understand. The short-circuit behavior (SCB) in particular is a dangerous DOB for machine and human. It could destroy the machine itself and cause heavy damage to the power supply unit and mechanical coupling components. Analytical calculation of the SCB is simplified and thus not highly accurate. Therefore, the finite element method simulation of the SCB is an important tool for understanding these effects without the danger of damaging the machine by experiments. In this paper, a suitable field formulation, modeling details, and simulation methods for dynamic analysis of synchronous machines are presented in detail. In particular, the accuracy of 2-D and 3-D transient electromagnetic simulations is analyzed by comparison against the available measurements performed on a chosen testing salient pole synchronous machine under the conditions of three-phase, two-phase, and single-phase short circuit. [ABSTRACT FROM AUTHOR]

The 3-D modeling technique presented in this paper, predicts, with high accuracy, electromagnetic fields and corresponding dynamic effects in conducting regions for rotating machines with slotless windings, e.g., self-supporting windings. The presented modeling approach can be applied to a wide variety of slotless winding configurations, including skewing and/or different winding shapes. It is capable to account for induced eddy currents in the conductive rotor parts, e.g., permanent-magnet (PM) eddy-current losses, albeit not iron, and winding ac losses. The specific focus of this paper is to provide the reader with the complete implementation and assumptions details of such a 3-D semianalytical approach, which allows model validations with relatively short calculation times. This model can be used to improve future design optimizations for machines with 3-D slotless windings. It has been applied, in this paper, to calculate fixed parameter Faulhaber, rhombic, and diamond slotless PM machines to illustrate accuracy and applicability. [ABSTRACT FROM PUBLISHER]

Complex scattering targets are often made by structures constituted by wedges and penetrable substrates which may interact at near field. In this paper, we describe a complete procedure to study this problem with possible developments in radar technologies (like GPR), antenna development, or electromagnetic compatibility (tips near substrates). The diffraction of an incident plane wave by a perfectly conducting (PEC) wedge over a dielectric half-space is studied using generalized Wiener–Hopf equations (GWHEs), and the solution is obtained using analytical and numerical–analytical approaches that reduce the Wiener-Hopf (WH) factorization to integral equations (IEs). The mathematical aspects are described in a unified and consistent theory for angular and layered region problems. The proposed procedure is valid for the general case and the paper focuses on E-polarization at normal incidence. The solutions are given in terms of geometrical/uniform theory of diffraction (GTD/UTD) diffraction coefficients and total far fields for engineering applications. This paper presents several numerical test cases that show the validity of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a robust frequency-domain method to tune the d–q decoupled control system used in Modular Multilevel Converter-type Voltage Source Converter (MMC-VSC) systems. A linearized state-space model of the MMC-VSC system is developed and used to calculate the stability-related frequency-domain attributes. The controller design problem is formulated as an optimization problem. In this paper, the simulated annealing optimization technique is applied to find the proportional-integral (PI) controller parameters that give desired damping for the oscillatory modes and desired values for decaying exponential modes. The efficacy of this method is tested on the electromagnetic transient model of a two-terminal MMC-VSC system on the real-time digital simulators, and the results are provided in this paper. Finally, tuned controller parameters for different ac system strengths are discussed and it is shown that this mathematical model is suitable to tune the PI-controller parameters for MMC-VSC systems connected to strong as well as weak ac networks. [ABSTRACT FROM AUTHOR]

The vibration of permanent magnet synchronous motor (PMSM) cores is related to the rotation speed. This paper presents a generalized magnetoelastic 3-D finite-element model, which can be used to calculate the magnetic field and structural vibration of laminated cores, including magnetostrictive effect. Magnetostriction (MS) is a property of electrical steel and causes the vibration of motor cores, the primary cause being electromagnetic forces. To implement the model, the vibration of a PMSM core was numerically analyzed under excitation with different frequencies. The speed and vibration were measured simultaneously by pulse and accelerometer sensors, and the variation of speed and vibration features was analyzed by Fast Fourier Transformation (FFT) versus Revolutions per minute (RPM). The numerically analyzed results showed that the vibration due to MS is important, and the magnitude of vibration is related to the operating speed. Vibration and speeds of the motor were tested and analyzed. The results showed that there is a vibration peak in the range of 600–2000 r/min (30–100 Hz), which is acceptable in calculation. [ABSTRACT FROM AUTHOR]

The multiple multipole program (MMP) is a boundary method for computing electromagnetic fields, which is well established in high-frequency electromagnetics and computational optics due to its flexibility in terms of accuracy control, field excitation, and fast convergence. As any other boundary method, MMP cannot efficiently solve nonlinear problems. The purpose of this paper is to show a novel numerical method for treating local nonlinear regions within a large linear MMP model. The main idea of this approach is to apply the well-known discretization scheme of the domain finite-element method (FEM) within the nonlinear region and to couple it over a special numerical interface with the linear MMP model surrounding it. The theoretical details of this FEM-MMP coupling and practical examples are presented in this paper. [ABSTRACT FROM AUTHOR]

In this paper, a detailed lumped model of the shield is developed, and an optimization method is proposed to minimize the shield loss while suppressing the emission within the standard limit. The electromagnetic emission in a wireless charging system (WCS) is a serious concern for health and safety, especially for medium- and high-power applications, where strong magnetic field propagates through a large air gap. Usually, a flat aluminum plate is used as a shield to suppress the emission outside the charging area. This field emission increases proportionally with the coil ampere turn; therefore, a much higher shield current is required to suppress the additional emission under the limit set by the International Commission on Non-Ionizing Radiation Protection. In this paper, a novel hybrid shield structure is proposed to limit the electromagnetic field (EMF) emission, as well as to minimize the shield loss. The proposed shielding is evaluated on a laboratory prototype of 7-kW WCS designed for electric vehicle application. The experimental result shows that, while suppressing the EMF under the limit, the shield loss has been reduced by 21% compared to the commonly used aluminum shield. [ABSTRACT FROM AUTHOR]

During the design process of the asymmetric-paths winding, the optimization between the asymmetric degree and the tidiness of end connections is still a difficulty for the existing methods. In this paper, the connection indices are proposed for the connection evaluation. In addition, a novel directed graph approach is provided for the connection optimization. It turns the connection design into the route optimization of the directed graph, including the modeling of the winding directed graph, the searching rules for a parallel path, and the matching rules between parallel paths. The winding design of a hydrogenerator is presented for the validation. The results show that the optimized scheme presents a tidy end connection, shorter circumferential busses, and a good performance in the electromagnetic field. This approach provides a new idea for the modeling of ac windings and the optimization design of the asymmetric-paths winding. [ABSTRACT FROM AUTHOR]

Nonlinear inductors have wide applications in dc/dc converters. The multiwindow multipermeability nonlinear inductor based on low-temperature co-fired ceramic (LTCC) technology has been proven to have a gradually changing wide-range inductance value curve while requiring no extra dc bias, which makes them suitable in various high-efficiency dc/dc converters. This paper focuses on the design of such a multiwindow multipermeability inductor based on an innovative module. Currently, the design of the LTCC inductors requires complicated simulation when coupling matrices among all the windows are taken into consideration. A simplified model for calculating the inductance value is proposed in this paper to reduce complexity. In the proposed model, the complicated inductance simulation is simplified to calculating inductance of three basic units in a nine-window inductor. By simulating the nine-window inductor, inductance of a rectangle-shaped inductor with any number of evenly distributed windows on it can be calculated. Based on the proposed model, the design guideline of the nonlinear inductor is also summarized. A 16-window two-permeability prototype is presented to demonstrate the design process according to the new model. The complete simulation and the test results are also provided to verify the model. The proposed model correlates with the simulation results very well. [ABSTRACT FROM PUBLISHER]