Electromagnetic modeling Research Papers - Academia.edu (original) (raw)

This paper describes some investigations into establishing primary standards of loss for waveguide Vector Network Analyzers (VNAs) operating at millimeter-and submillimeter-wave frequencies. The standards comprise straight sections of waveguide, where the waveguide line is orientated such that the waveguide aperture is at right-angles to the waveguide apertures on the VNA test ports. This 'crossconnected' waveguide forms a section of waveguide that is effectively below cutoff. The mechanical discontinuity between the cross-connected waveguide and the VNA test ports also generates significant reflection. The combined effect due to these two loss mechanisms-cutoff attenuation and discontinuity reflection loss-can be predicted from electromagnetic theory and so can be used to establish sections of cross-connected waveguide, of various lengths, as primary standards of loss. The paper describes these standards in detail and compares experimental results, obtained using a VNA operating in the 50 GHz to 75 GHz band, with values predicted by electromagnetic modeling software.

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- Reflection, Electromagnetic modeling, Attenuation, Apertures

Volume conductor models influence TMS electric field estimates. Present TMS navigation systems use computationally simple spherical conductor models. Anatomically realistic boundary-element models can improve TMS targeting especially at... more

- by Aapo Nummenmaa and +1
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- Engineering, Psychophysiology, Magnetoencephalography, Magnetic Resonance Imaging
- by Diego Caratelli
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- Engineering, Electromagnetism, Electromagnetic Compatibility, RFIC

This paper develops a simple sensorless control algorithm for an induction motor. An observerless controller is proposed, which guarantees local asymptotic speed tracking-flux regulation under condition of constant load torque. The controller development is based on the decomposition of the induction machine model in two coupled subsystems: electromechanical and electromagnetic, achieved by means of indirect field-oriented transformation. The experimental results demonstrate the steady-state and dynamic performance suitable for general industrial applications.

Metamaterials (MTM) have become a major electromagnetic research topic. Initial studies have focused on understanding their electromagnetic properties and interactions. This paper presents a novel virtual tool, MTM-FDTD, for the visualization of electromagnetic wave interacting with different metamaterials. Snapshots from characteristic examples during these interactions are presented. Scenarios with normal and oblique incidences, demonstrating focusing beams in planar metamaterials and

- by Levent Sevgi
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- Visualization, Antennas & Radio Wave Propagation, Metamaterials, Dispersion

Computational studies of the head utilizing finite element models (FEMs) have been used to investigate a wide variety of brain-electromagnetic (EM) field interaction phenomena including magnetic stimulation of the head using transcranial magnetic stimulation (TMS), direct electric stimulation of the brain for electroconvulsive therapy, and electroencephalography source localization. However, no human head model of sufficient complexity for studying the biophysics under these circumstances has been developed which utilizes structures at both the regional and cellular levels and provides well-defined smooth boundaries between tissues of different conductivities and orientations. The main barrier for building such accurate head models is the complex modeling procedures that include 3D object reconstruction and optimized meshing. In this study, a structurally detailed finite element model of the human head was generated that includes details to the level of cerebral gyri and sulci by combining computed tomography and magnetic resonance images. Furthermore, cortical columns that contain conductive processes of pyramidal neurons traversing the neocortical layers were included in the head model thus providing structure at or near the cellular level. These refinements provide a much more realistic model to investigate the effects of TMS on brain electrophysiology in the neocortex.

- by David Mogul
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- Cognitive Science, Finite Element Methods, Biomagnetism, Magnetic Resonance Imaging

A general circuit-oriented, full-wave, finite-element method (FEM) is proposed to analyze the coupled problem between circuits and fields both in frequency and in time domains. The electromagnetic field problem is modeled by an equivalent electrical network obtained by the Whitney finite-element equations. The presence of circuit components in the field domain is easily taken into account introducing the lumped circuit components directly in the field equivalent electrical network. Simple test configurations are analyzed by a CAD circuit simulator to show the performances of the proposed circuit-oriented method.

- by Mauro Feliziani
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- Engineering, Finite Element Methods, Electrostatics, Finite element method

The physical basis for breast tumor detection with microwave imaging is the contrast in dielectric properties of normal and malignant breast tissues. Confocal microwave imaging involves illuminating the breast with an ultra-wideband pulse from a number of antenna locations, then synthetically focusing reflections from the breast. The detection of malignant tumors is achieved by the coherent addition of returns from these strongly scattering objects. In this paper, we demonstrate the feasibility of detecting and localizing small ( 1 cm) tumors in three dimensions with numerical models of two system configurations involving synthetic cylindrical and planar antenna arrays. Image formation algorithms are developed to enhance tumor responses and reduce early-and late-time clutter. The early-time clutter consists of the incident pulse and reflections from the skin, while the late-time clutter is primarily due to the heterogeneity of breast tissue. Successful detection of 6-mm-diameter spherical tumors is achieved with both planar and cylindrical systems, and similar performance measures are obtained. The influences of the synthetic array size and position relative to the tumor are also explored.

- by Nguyen Thang
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- Algorithms, Gynaecology, Biomedical Engineering, Computational Modeling
- by Pushkin Kachroo
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- Automatic Control, Robust control, Electromagnetic modeling, Sliding mode control

This paper investigates the problem of simulation of realistic soils for electromagnetic 3-D computational models. The major difficulty is to take into account the heterogeneous nature of real-life soils, which is an aggregate of random and regular structures, due to environmental (climatic conditions, etc.) or human (soil tillage) processes. The developed methodology uses 3-D measurements of pertinent soil parameters, able to describe the heterogeneity of real-life soils. It can be broken down into four main tasks: (a) 3-D measurement of soil parameter(s); (b) characterization of the 3-D spatial distribution of soil parameter(s); (c) simulation of 3-D volumes with the same spatial distribution; and (d) simulation of 3-D soil permittivity maps using electromagnetic mixing model. This methodology is illustrated with the example of soil density measurement, which is evaluated with the use of a motor-driven penetrometer.

- by Claude Bacconnet
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- Computational Modeling, Agriculture, Electromagnetic modeling, Moisture

_ This paper deals with the evaluation of electromagnetic transients in a lightning protection system (LPS). A field-approach is used, based on the numerical solution of a modified version of the thin-wire electric field integral equation in frequency domain. Time profiles of electromagnetic interesting quantities are computed by using a discrete fast Fourier transform algorithm. The model takes into account coupling effects among aerial parts and ground electrodes in order to correctly estimate the quantities which can determine electromagnetic hazard inside the LPS; transient touch and step voltages can be easily evaluated also taking into account the human body presence on the soil surface. To this purpose, a crucial point is the accurate evaluation of the currents distribution among the earthed branches of the LPS and this needs to correctly consider mutual electromagnetic interference among the aerial parts and the earth-termination system of a same LPS. A suitable approach to consider the lossy soil is employed. Validation of the proposed model is performed by comparing the results with those measured and computed available in technical literature. Simulation examples related to realistic LPS structures are presented and discussed to show the flexibility and the accuracy of the model in the range of practical applications inside the volume to be protected.

- by Guido Ala and +1
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- Electromagnetic Compatibility, Electromagnetic Interference, Integral Equations, Comparative Study

In this paper we outline a new scheme for parameterizing polarimetric scattering problems, which has application in the quantitative analysis of polarimetric SAR data. The method relies on an eigenvalue analysis of the coherency matrix and employs a three-level Bernoulli statistical model to generate estimates of the average target scattering matrix parameters from the data. The scattering entropy is a key parameter is determining the randomness in this model and is seen as a fundamental parameter in assessing the importance of polarimetry in remote sensing problems. We show application of the method to some important classical random media scattering problems and apply it to POLSAR data from the NASA/JPL AIRSAR data base.

- by bala krishna
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- Geophysics, Remote Sensing, Data Mining, Polarimetry

Grid interface of renewable energy based distributed generation requires satisfying the interconnection requirements stipulated by the local distribution utility. Detailed testing of protection and control systems is required to ensure conformity to wide ranging interconnection requirements such as fault ride through capability, protection against islanding, harmonics and voltage flicker limits. Electromagnetic transient simulation is a powerful tool for performing such studies with very detailed models of power electronics converters, controllers and protection systems. Furthermore, the simulated transient waveforms can be recorded and played back into actual hardware using real time signal playback equipment to verify correct operation.

- by Athula Rajapakse
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- Power Electronics, Renewable Energy, Renewable energy resources, Control Systems

This paper defines and applies a novel computerised electromagnetic modelling methodology, which evades the difficulty of establishing the equilibrium field in a space crammed with a varied mix of materials and electronics. Instead the rate of electromagnetic energy ingress to the cavity through slots and apertures in its casing becomes the focus. An upper limit on the quantity of energy that can be available to affect or damage sensitive devices and components is inferred by calculation of the total energy seeping into the space within their reaction times. An example case focusses on the applicability of this methodology to safety analyses.

- by Andrew Chugg
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- Electromagnetism, Electromagnetics, Electromagnetic modeling

This paper deals with the characterization, as well as the modeling, of the susceptibility of integrated circuits (ICs) to conducted electromagnetic disturbances such as a continuouswave disturbance. Based on accurate measurement results, a robust mathematical model to predict the susceptibility of a CMOS inverter is developed. This model is based on a neural network approach and is validated up to 1 GHz for different test criteria. A good agreement between measurements and simulated results is reported. The mathematical model is implemented in a software tool such as Advanced Design System in order to facilitate its operation in the evaluation of the susceptibility of ICs.

It is well established that all-dielectric self-supporting cables on high-voltage overhead power lines can suffer from damage through the mechanism of dry-band arcing. A number of heuristics have evolved over the past 20 years and these are used to determine whether such cables are capable of reliable performance. A key element to planning is modeling the installation conditions. In addition to the geometry of the high-voltage line, such a model needs to consider the climatic environment and potential pollutants on the cable. In this paper, a model is built based on the commercial software current distribution, electromagnetic fields, grounding and soil structure analysis which is widely used in the power industry. The model developed is shown to be consistent with a number of previously published models. It is demonstrated that the relative sags of all-dielectric self-supporting cable and conductors are key to the severity of the installed situation. It is also shown that the towers do not need to be modeled for the most severe cases of high pollution, but are required for accuracy in medium and low pollution cases.

- by Konstantinos Kopsidas
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- Modeling, Structural Analysis, Planning, High Voltage

The injection of CO 2 in saline aquifers and depleted hydrocarbon wells is one solution to avoid the emission of that greenhouse gas to the atmosphere. Carbon taxes can be avoided if geological sequestration can efficiently be performed from technical and economic perspectives. For this purpose, we present a combined rock-physics methodology of electromagnetic (EM) and seismic wave propagation for the detection and monitoring of CO 2 in crosswell experiments.

- by D. Gei
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- Electromagnetic modeling, Petroleum Science and Engineering

A comparison is made between two coupling models frequently used to estimate the lightning-induced overvoltages in power lines. The first model was introduced by Rusck [l] and the second model by Agrawal, Price, and Gurbaxani [2]. In the nomenclature adopted in this paper, the first model is referred to as the "Rusck model" and the second as the "Wave Antenna Model." The transmission l i e equations of the Rusck model can be written in such a way that the forcing term in the equations is the horizontal electric field. The results show that the Rusck model is incomplete. It takes into account the portion of the horizontal electric field generated by the gradient of the scalar potential but neglects the contribution from the vector potential. This defect in the Rusck model makes it source-dependent. That is, the Rusck model can give accurate results only when the spatial location of the source that generates the electromagnetic field is such that the contribution of the vector potential to the horizontal field is either zero or can be neglected. Under such circumstances the Rusck model and the Wave AnteMa Model are described by the same transmission l i e equations, and the results predicted by the two models are identical.

- by vernon cooray
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- Power System Protection, Antenna Theory, Power Generation, Electromagnetic modeling

In this paper we present some results on detection and classification of low metal content anti personnel (AP) landmines using a modified version of the Auto Regressive (AR) modeling algorithm presented in. A statistical distance is computed between the AR coefficients of the measured GPR time signal and the AR coefficients of a reference database (containing the AR models of the mines of interest) and a detection is declared if this distance is below a given threshold.

- by Daniela Deiana
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- Ground Penetrating Radar, Databases, Electromagnetic modeling, Gpr

This paper proposes the use of the dynamic phasor approach for studying the behavior of doubly-fed induction generators during faults and unbalanced conditions. The dynamic phasor approach provides more accurate models than the quasistationary ones and, at the same time, is computationally more efficient than detailed EMTP models. Two contingencies are taken as examples to study the wind turbine behavior: balanced and unbalanced voltage sags. Results are compared with standard electromechanical and electromagnetical models.

- by Federico Milano
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- Induction Generators, Wind turbine, Electromagnetic modeling, Voltage sag
- by Samir El-Masri
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- Bioacoustics, Computational Modeling, Speech Production, Numerical Analysis

The validity and applicability of a high-level sim-6 ulation approach of radio-frequency microelectromechanical-7 system (RF-MEMS) devices, based on a library of analytical 8 compact models of elementary MEMS components, are investi-9 gated through an extensive comparison between simulation re-10 sults and measurements of some representative devices (variable 11 capacitors and series ohmic switches). The in-house developed 12 simulation tool is implemented in a standard IC simulation envi-13 ronment supporting behavioral description capabilities. The de-14 vices are built in a silicon substrate technology with suspended 15 gold membranes. We analyze the mechanical, electrical, and RF 16 response of the devices. The RF behavior is modeled by extracting 17 a lumped element network from measured S-parameters (scatter-18 ing-parameters) to account for parasitic effects and by wrapping 19 this network around the intrinsic MEMS device simulated with the 20 compact models. We show that an accuracy within 5% is obtained 21 in all considered physical domains and conditions, provided that 22 some effective parameters (including the residual air gap in the 23 actuated state and the RF parasitic elements) are properly ex-24 tracted from measurements and accounted for in the simulations. 25 The main factors limiting the model's predictive capability are 26 due to process nonidealities, such as plate bending due to residual 27 stress gradient, oxide charging, surface roughness, and suspended 28 membrane thickness variations, rather than for instance in-plane 29 geometric process variations. [2009-0266] 30

- by Roberto Gaddi
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- Electromagnetism, Modeling, Microelectromechanical systems, Surface Roughness

This paper presents a technique for modeling of asymmetric domain rotation in magnetic materials. The technique uses a variable pinning strength, instead of a constant, to model the asymmetry. This allows modeling of quasi-static... more

- by D. Ribbenfjard
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- Engineering, Modeling, Magnetic Materials, Hysteresis

Calculating leakage inductances between windings of multi-winding Traction transformers is one of the most important schemes in design procedure. In this paper, analytical and finite element methods (FEM) have been introduced for electromagnetic modeling of traction transformers with four pancake split windings. Using these models, the leakage inductances between the split windings are calculated and the models have been validated with the help of experimental data gathered from a typical 4000 kVA cast-resin dry-type transformer. Some reformations are employed to improve the FEM results and effects of these reformations on accuracy of the model are studied. Employing the validated models, the effects of middle yoke on the leakage inductances of split winding traction transformers are discussed in this paper.

- by davood Azizian
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- Finite Element Methods, Finite element method, FEM, Finite Element Analysis

In this paper an efficient method for detection of inrush current in distribution transformer based on wavelet transform is presented. This method uses Wavelet Transform (WT) and Probabilistic Neural Network (PNN) to discriminate inrush current from other transients such as capacitor switching, load switching and single phase to ground fault. WT is used for decomposition of signals and PNN for classification. Inrush current data and other transients are obtained by simulation using EMTP program. Results show that the proposed procedure is efficient in identifying inrush current from other events.

- by Pierluigi Siano
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- Neural Networks, Wavelet Transform, Wavelet Transforms, Electromagnetic modeling

The paper summarizes a new modeling procedure for 3D virtual design of EMI filter circuits. The proposed method, based on the coupling of the Partial Element Equivalent Circuit (PEEC) and Boundary Integral Method (BIM) methods, extends the standard PEEC approach for modeling in the presence of magnetic materials, hence allowing the PEEC-based modeling of toroidal EMI filter inductors. The PEEC-BIM

In this paper, a new approach for the development of planar metamaterial structures is developed. For this purpose, split-ring resonators (SRRs) and complementary split-ring resonators (CSRRs) coupled to planar transmission lines are investigated. The electromagnetic behavior of these elements, as well as their coupling to the host transmission line, are studied, and analytical equivalent-circuit models are proposed for the isolated and coupled SRRs/CSRRs. From these models, the stopband/passband characteristics of the analyzed SRR/CSRR loaded transmission lines are derived. It is shown that, in the long wavelength limit, these stopbands/passbands can be interpreted as due to the presence of negative/positive values for the effective and of the line. The proposed analysis is of interest in the design of compact microwave devices based on the metamaterial concept.

- by Francisco Falcone
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- Metamaterials, Resonators, Electromagnetic modeling, Equivalent Circuit

Today, self-excited synchronous machines are the object of increasing interest because they use neither brushes nor permanent magnets. In fact, the price of rare earth metals is considerably high and still raising. This is the main reason why researchers are looking for suitable alternatives to permanent magnets in the construction of rotating electrical machinery. This paper deals with the design and laboratory testing of a synchronous machine with an efficient layout and an economic construction. The proposed self-excited machine exploits the space harmonics of the magneto-motive force to produce the excitation field. The model analysis is based on the computation of the back EMFs that are associated to the magneto motive force components. The mathematical model suggests an easy way to decouple the rotor windings. The machine has been built and experimental tests have been performed in order to validate the electrical behavior.

- by Guido Rubino and +1
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- Electromagnetic modeling

The spatial distribution of electrical potential and current in a suspension of spherical cells under an applied electric field was numerically obtained using the equivalent circuit method (ECM). The effect of the proximity of the cells was studied in a set of simulations where the volumetric fraction varied from 0.24 to 0.66. The results show that the transmembrane potential for cells in the suspension is lower than the theoretically predicted value for a single dielectric membrane under a uniform electric field. It was also observed that as the volumetric fraction is increased, the transmembrane potential on the pole of the cells decreases linearly. Furthermore, the conductivity of the suspension was also observed to be a function of the volumetric fraction and this result is in a good agreement with the Maxwell's model for spherical particles suspended in a volume conductor.

The presence of chloride ions in steel-reinforced strucfures leads to the corrosion of Qe reinforcement thus compromising the inrepi@' and strength of the strucfure. Thus, it is of great importance to be able to non-destructively detect and evaluate the free chloride content in concrete% To that end, an investigation was initiuted where two morIar cubes were soaked in distiUed water and saltwater solutions, respectively. Their Iemporal microwave refle&'on properries were measured using open-ended rectangular waveguides on a daily basis for three cycles, each rusting 35 days. A semi-empirical electromagnetic model was then deveroped IO simulate the reflection properties of the cubes. The oufcome of the model describes the water and saltwater distribution within the cubes. In addition, the distribution curves ako depict the manner in which the water and salmater contents vary within the cubes from day to day. This paper presents a comparison benveen the water and saltwafer d...

- by shanup peer
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- Water, Nondestructive testing, Electromagnetic modeling, Frequency

In order to design on-chip interconnect structures in a flexible way, a computer-aided design approach is advocated in three dimensions, describing high-frequency effects such as current redistribution due to the skin effect or eddy currents and the occurrence of slow-wave modes. The electromagnetic environment is described by a scalar electric potential and a magnetic vector potential. These potentials are not uniquely defined and in order to obtain a consistent discretization scheme, a gauge transformation field is introduced. The displacement current is taken into account to describe current redistribution and a small-signal analysis solution scheme is proposed based upon existing techniques for fields in semiconductors.

- by Wim Schoenmaker
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- Computer Aided Design, Computer Hardware, Signal Analysis, High Frequency
- by Gonul Turhan-sayan
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- Metamaterials, Resonators, Electromagnetic modeling, Equivalent Circuit

- by Vernon Cooray
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- Power System Protection, Antenna Theory, Power Generation, Electromagnetic modeling

The ionosphere is an important source of errors for the GPS signals that travel through the ionosphere on their way to the ground-based receivers by introducing a frequency dependent path delay proportional to the total electron content (TEC) along the signal path. For dual-frequency GPS receivers, the ionospheric effects can be accounted for by taking advantage of the dispersive nature of the ionosphere in the microwave region of the electromagnetic spectrum, while for the single frequency GPS receivers the ionospheric effects can be minimized by modeling them using, for example, empirical or physics-based ionospheric models. On the other hand, the errors imposed by the ionosphere on the GPS signals can provide important temporal and spatial information about the electron density distribution in the ionosphere. Besides the ionospheric errors, there are some other sources of errors that can affect the GPS signals, such as the satellite and receiver instrumental biases, multipath effects, clock errors, orbital errors, tropospheric errors, but which can be compensated for, estimated, or neglected depending on the particular application. In this paper, we only concern ourselves with the ionospheric effects on the GPS signals, and describe a Kalman filter-based algorithm for near real-time estimation of the line-of-sight and vertical ionospheric TEC and of the combined satellite-receiver instrumental biases using data from dual-frequency GPS receivers.

- by Tiberiu Letia
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- Global Positioning System, Kalman Filter, Dispersion, Ionosphere

A genetic algorithm is used for design of infrared filters and in the understanding of the material structure of a resonant tunneling diode. These two components are examples of microdevices and nanodevices that can be numerically simulated using fundamental mathematical and physical models. Because the number of parameters that can be used in the design of one of these devices is large, and because experimental exploration of the design space is unfeasible, reliable software models integrated with global optimization methods are examined. The genetic algorithm and engineering design codes have been implements on massively parallel computers to exploit their high performance. Design results are presented for the infrared filter and a resonant tunneling diode

- by tom cwik
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- Microelectronics, Genetic Algorithms, Engineering Design, Mesh generation

We investigate in this paper a numerical method to control the temperature of an induction heating process through electric current parameters such as frequency and current voltage imposed to the terminals of the inductor. We seek a sinusoidal voltage function whose amplitude varies in time. For this, we use a two-dimensional induction heating model that involves a phase transition in which the magnetic field has only one nonvanishing component. The procedure can be extended to more sophisticated models without major modification of the optimal control problem. We present a numerical control algorithm and discuss numerical experiments that prove the efficiency of the procedure.

- by Rachid Touzani
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- Engineering, Optimal Control, Process Control, Numerical Method

This paper addresses the development of macromodels for input and output ports of a digital device. The proposed macromodels consist of parametric representations that can be obtained from port transient waveforms at the device ports via a well established procedure. The models are implementable as SPICE subcircuits and their accuracy and efficiency are verified by applying the approach to the characterization of transistor-level models of commercial devices. I. S. STIEVANO, I. A. MAIO, F. G. CANAVERO, PARAMETRIC MACROMODELS. . . 2 the estimation of model parameters is best performed by virtual measurements carried on transistor-level models of the IC, and the effects taken into account by the model are decided a priori, when the equivalent circuit is selected.

- by Jacques Sombrin
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- Electromagnetic modeling, Multiplexer, Filtering, Structural Response

Impedance and associated electromagnetic (EM) fields of an EM return-stroke model are investigated with the help of NEC-2. The impedance of a cylindrical vertical conductor increases with time. The impedance of a vertical conductor having additional distributed inductance is initially 700 to 1000 for the current propagation velocity ranging from 170 to 130 m s. This is in good agreement with the apparent impedance of a lightning channel, estimated from lightning-current waveforms measured at the top and bottom of tall towers. A model considering a horizontally bent channel in a thundercloud succeeds in reproducing all of the established features of measured field waveforms except the hump of close magnetic field, while a vertically straight conductor fails to reproduce two of the features. Index Terms-LEMP, numerical electromagnetic (EM) field analysis, return stroke.

- by Masaru Ishii
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- Electromagnetic Compatibility, Modeling, Magnetic field, Channel Estimation

A system-level electromagnetic (EM) modeling tool combining a three-dimensional (3-D) full-wave finite-element EMfield analysis tool and a time-domain electric-circuit simulator is developed and applied to various geometries such as multilayer printed circuit boards (PCB's), signal lines embedded in a PCB or package, and split power-distribution network. Since the signal integrity is a primary concern of high-speed digital circuits, the noise distributions on various circuit planes are evaluated from the analysis. These noise distributions, often called noice maps, are utilized to identify the location of the major source of simultaneous switching noise (SSN). This information can eventually be adapted for optimum placement of decoupling capacitors to minimize the noise fluctuations on the various circuit planes on an entire PCB. area of EM design and characterization of microwave/millimeter-wave circuits and components and VLSI and MMIC interconnects using the FEM, and development of numerical techniques for analysis and design of high-speed high-frequency circuits with emphasis on parallel/super computing.

- by Linda Katehi
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- Finite Element Methods, Signal Integrity, Digital Circuits, Finite Element

The problem of electromagnetic wave propagation in almost periodic media is investigated, and a solution is obtained directly from Maxwell's equations. The evaluation of this solution involves a generalization to almost periodic media of the Brillouin diagram of periodic media. The Brillouin diagram is used to place in evidence similarities and differences of wave propagation in periodic and almost periodic

An attempt is made to expand the spectral approach, implemented only for the M-type devices yet, onto O-type devices such as one-beam klystrons and travellingwave tubes. The general features of the new spectral models are described. The... more

The authors present a novel nonlinear homogenization technique for laminated iron cores in three-dimensional (3-D) finite-element (FE) models of electromagnetic devices. The technique takes into account the eddy current effects in the stacked core without the need of modeling all laminations separately. A nonlinear constitutive magnetic law is considered. The system of nonlinear algebraic equations obtained after time discretization is solved by means of the Newton-Raphson scheme. By way of validation, the method is applied to a 3-D FE model of a laminated ring core with toroidal coil.

- by Ruth Sabariego
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- Engineering, Finite Element Methods, Finite element method, Finite Element

This is an introductory paper on -transform-based methods for electromagnetic transient simulations of power systems. Since the theory of the -transform was originally developed for the analysis of time series data defined at equidistant time steps, simulation models developed using -transforms can readily be used in electromagnetic transient simulations based on the same time step. First, this paper briefly introduces the basics of the -transform, and then applications to electromagnetic transient simulations of power systems are reviewed.

- by Abner Martínez
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- Power Systems, Signal Processing, Time Series, Power System

This paper expands on a hybrid numerical method coupling the finite element method (FEM) and boundary integral equation method (BIEM), developed to calculate magnetic fields in a switched reluctance motor (SRM). This hybrid approach is a solution to the issues stemming from the small size and odd shape of the SRM airgap, where meshing an FEM grid is difficult. In the past, the stator and rotor FEM domains kept their actual shapes, which resulted in problems with the definition of the unit outward normal vectorñ at the corner points of the SRM poles. Therefore, the normal derivative of the magnetic vector potential, i.e., the tangential component of the flux density, was undefined at these points. In this paper, a new approach with new definitions of the stator and rotor FEM domains is presented. The new concept defines the SRM airgap as a ring in which circular boundaries permit the correct definition of the normal derivative quantities and exploit the natural Neumann condition. The electromagnetic parameters of a 7.5-kW SRM prototype machine were calculated using this new approach. They compare favorably with test data. Phase magnetization characteristics also have good precision and smoothness. These electromagnetic parameters were then used to assess and compare two different SRM models for the calculation of the torque on the motor shaft, the linear trapezoidal model and the nonlinear model. The comparison between the measured torque and the torque as calculated with the two different models shows that the more simple trapezoidal model should be satisfactory in many cases and could, in particular, be used in automated SRM designs.

- by michel renglet
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- Engineering, Finite Element Methods, Finite element method, Integral Equations

A tunable backward wave oscillator (BWO) for terahertz applications is proposed. The use of a corrugated rectangular waveguide as the slow-wave structure permits relevant performance together with full compatibility with microfabrication technologies. The design, done using an analytical electromagnetic model, is fully verified by 3-D particle-in-cell simulations. A 20% tuning bandwidth is obtained at a central frequency of 1 THz, demonstrating more than 100-mW output power.

- by Claudio Paoloni
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- Terahertz Waves, Microfabrication, Electromagnetic modeling, Terahertz