New Publications are available for Electric and magnetic fields
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New Publications are available now online for this publication.
Please follow the links to view the publication.Detailed analysis of contact resistance of fretting corrosion track for the tin plated contacts
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0652
Tin plated terminals are widely used for automotive connectors due to low cost and higher reliability. But it is observed that contact resistance of tin plated terminal increased due to fretting corrosion, which is originated from heat cycle or vibration. In order to clarify the degradation of terminal, it is necessary to obtain the contact resistance distribution on fretting corrosion wear of tin plated contact in detail, because the terminal has more than two point of conduction point at least. Thus, the detail measurement of resistance distribution in fretting corrosion wear is performed to estimate contact resistance at mating terminal. As the result, in the region of higher concentration of oxygen measured by EDX analysis, the resistance is tended to be measured higher. And the contact resistance of whole contact wear is estimated by static electric field analysis based on film resistance distribution at contact wear. These analysis results are approximately agreement with the contact resistance on fretting corrosion experimentally. That means the degraded resistance of terminal mating would be estimated using by this technique.Experimental study on arc duration under external transverse magnetic fields in a DC 580V circuit
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0617
Using transverse magnetic field (TMF) is one of the most important ways to improve the electric life and the breaking capacity of DC relays. In order to better understand the influence of transverse magnetic field on arc duration, a series of experiments were conducted under external transverse magnetic field with 4 relay contacts in a DC 580V/60A circuit. Using permanent magnets, the transverse magnetic field is obtained and the magnetic flux density at center magnet can be varied from 80 to 320 mT. The results show that the making arc duration is independent of magnetic flux density, but the breaking arc duration is decreased monotonically with the increase of the magnetic flux density. In addition, the gradient |Δt/ΔB| of the breaking arc duration is decreased with the increase of the magnetic flux density, which means the curve of tB tends to be flat.Interpolation of magnetic and electric fields using spherical elementary current systems
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0396
A physics-based technique for interpolating magnetic and electric field disturbances of external origin across large spatial areas can be achieved by employing the Spherical Elementary Current System (SECS) method using data from ground-based magnetic observatories. The SECS method represents complex electrical current systems as a simple set of equivalent currents placed at a specific height in the ionosphere. The magnetic field recorded at observatories can be used to invert for the electrical currents and subsequently employed to interpolate or extrapolate the electric and magnetic field across a large area at midto high geomagnetic latitudes. Here we show that the magnetic field interpolation can be improved, even over very large distances (> 1000 km), by the addition of further observatory data into the SECS inversion. (5 pages)Anomalous ground wave tilt measured over wet ground
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0397
The nominally vertical E-field of a ground wave is classically predicted to tilt forward in the direction of wave travel. Past measurements confirming this have been made at four spot frequencies between 5.25 and 28MHz by NTIA in Boulder, Colorado, USA reported in 1984. The ellipticity of the wave motion was also measured. A novel tuned loop based wave tilt equipment has been devised to make measurements of both tilt and wave ellipticity over wet clay soil at any frequency down to 2MHz. Below about 5.3MHz the direction of wave tilt has been found to reverse to a backward tilt and become `anomalous'. New EM theory is presented to explain this fundamentally new discovery. (5 pages)Computations of electromagnetic forces and fields in double sided linear induction motor (DLIM) using finite element method
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0058
This paper aims to present the material aspects of Linear Motion Induction Motor. The Electromagnetic Characteristics of Linear Induction Motor (LIM) are more complex than other rotating type induction motors[1]. It is very significant to evaluate Magnetic Field parameters for the design of an optimized model for various applications. In this present work. Double Sided Linear Induction Motor (DLIM) has been analyzed to compute Magnetic Field Density, Magnetic Vector Potential and other force components by using one of the latest Finite Element Method (FEM) software i.e. Maxwell The simulation results of DLIM are also validated with experimental setup of DLIM.Electromagnetic source reconstruction by reversed-TLM method
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0020
Classical methods for source synthesis are iterative, time consuming and not always adapted to the desired problem. In this paper we present a new method of electromagnetic source synthesis based on the time reversal technique. This approach employs the Reversed-TLM method and permits the reconstruction of an unknown source distribution, from its electromagnetic far-field radiation. Point-like source reconstruction results show that by using this method, the "classical" half-wavelength resolution limit is overcome.Magnetic stresses analysis of a two speed, large power, synchronous motor in abnormal working conditions
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0044
This paper deals with the electromagnetic calculations of the stator magnetic stresses in the two-speed, large power, silent pole, synchronous motor. Prediction of such stresses is very important in understanding vibration phenomena of these special electrical machines. Because of non-symmetrical armature (stator) and field (rotor) winding the only one way of investigation is Finite Element Modelling. The simulations results for nominal load, for two different rotational rotor speeds: n=500 rpm (p=6) and n=600 rpm (p=5) are presented.A two-level solver for nonlinear magnetic field problems using the p-version of the FEM
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0018
In this work we present an approach for solving non linear magnetostatic fields by utilizing the p-version of the FEM. The hierarchical H(curl)-conforming elements enable a natural splitting in lower order Nedelec-type shape functions and higher order ones. We develop a two-level solver analogous to the multigrid method, where the initial solution of the nonlinear problem on the lower order space is inserted into the higher order one, thus reducing the computational effort. Due to the explicit representation of gradients in the shape functions, the higher order space can be solved robustly using a simple Schwarz type preconditioned Krylov method. The efficiency of the proposed method is demonstrated by TEAM benchmark problems.Review of low and high frequency methods for computational electromagnetics
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0001
Practical applications create requirements on different methods for Computational Electromagnetics. A couple of these methods are compared in this paper and their suitability for low and high frequencies is particularly highlighted.Implications of Galilean electromagnetism in numerical modeling
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0062
The purpose of this article is to present a wider frame to treat the quasi-static limit of Maxwell's equations. We discuss the fact that there exists not one but indeed two dual Galilean limits, the electric and the magnetic one. We start by a re-examination of the gauge conditions and their compatibility with Lorentz and Galilean covariance. By means of a dimensional analysis on fields and potentials we first emphasize the correct scaling yielding the equations in the two limits. With this particular point of view, the gauge conditions of classical electromagnetism are continuity equations whose range of validity depend on the relativistic or Galilean nature of the underlying phenomenon and have little to do with mathematical closure assumptions taken without physical motivations.Review of HF and coupled problems
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0004
Summary form only given. We will present a hybrid software system combining three blocks: a full-wave 3D EM solver, a set of thermal analysis modules, and temperature-dependent material data obtained via measurements. Considerations of load movement during the heating will also be given. The entire presentation will be illustrated with practical examples in the following areas of applications: transmission lines and their junctions, antennas, resonators, microwave domestic ovens, industrial microwave power applications, quasi-optical problems in nano-scale. We hope that the presentation will provide a focused starting point for discussions between HF practitioners, at the same time giving LF researchers a quick introduction to the specific challenges in HF. We will shortly outline the scope of application of the Finite Element Method (FEM), the Method of Moments (MoM), and the Transmission Line Matrix (TLM) Method but will mostly concentrate on the Finite Difference Time Domain (FDTD) Method, which has been recently established as the most frequently used by HF engineers.Comparative analysis of A-V and A-T-T<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0</sub> calculations of induced currents in multiply connected regions
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0013
The paper offers a comparative analysis of two methods, both using potentials, for electromagnetic field computation in multiply connected regions, including a conventional A-V approach and a fairly new and much less popular A-T-T<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0</sub> formulation. The relevant finite element equations are provided. To facilitate comparisons the TEAM Workshop Problem No. 7 has been solved and the results of both methods verified by measurements. Computational times have been considered and the A-T-T<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0</sub> approach found to be much more efficient.Comparison of automatic planar mesh generation schemes facilitating edge meshing
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0086
In this paper, a comparison of two automatic surface mesh generation schemes is presented. One is available in a commercial application (Zeland IE3D™), and the other is a scheme proposed and implemented by one of the authors (CGSM). Each scheme uses rectangular and triangular cells and facilitates edge meshing. The comparison consists in using each scheme with the same meshing parameters to discretize several structures. Subsequently, the quality of resulting meshes is compared in terms of: their shape, the number of cells, the number of internal edges, sizes and shapes of the cells as well as the computation times.Coupling field analysis and non-deterministic optimization by means of multiprocessor parallel computation for characterizing magnetic anisotropy
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0093
The paper proposes an automated procedure for linking an identification algorithm implemented in a general purpose environment (MatLab™) with a commercial Finite-Element code for magnetic field analysis (VF Opera™). This procedure is applied to identify automatically the B-H curve of anisotropic magnetic laminations in the direction normal to the sheet surface. A multiprocessor computer made it possible to perform parallel computations. An identification procedure based on a non-deterministic algorithm allows finding the whole B-H curve for sheet samples.Application of the finite element method for the analysis of the grounding grid implying the finite line elements
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0015
In this paper, the new numerical model is presented to analyze the electromagnetic field around the grounding grid. In contrast to recently existent procedure based on the "classical" finite element method (FEM), in this new methodology the soil and the air domain of the problem are discretized by the 3-D finite elements and the conductors of the grounding grid are discretized by 1-D finite line elements. The results of calculations have been verified by comparison with the results of measurements found in the literature.On hybrid methods for modeling complex electromagnetic problems
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1368
This paper presents a review of selected hybrid numerical methods for efficient solution to complex electromagnetic problems. First, recent developments in computational electromagnetics are briefly reviewed and several remaining challenges are addressed. Second, advantages of hybrid numerical methods are highlighted and hybridization strategies are described. Recent developments in hybrid numerical methods are then introduced and numerical examples are shown to demonstrate advantages of hybrid numerical methods. Future studies of hybrid techniques are finally suggested.New directions in computational electromagnetics
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1376
Computational EM (CEM) is a very active field, as is evident from a quick glance at the literature, comprising of journal papers as well as proceedings of symposia in the areas of Antennas, Propagation, Microwave Circuits, and Metamaterials, just to name a few. A variety of CEM tools that are based on the Integral Equation techniques, e.g., the MoM and TDIE, and Finite Methods such as the FEM and FDTD, are available to us for solving a wide range of EM problems. The above CEM methods have recently been embellished by combining them with innovative techniques such as the FMM for MoM-based algorithms, Discontinuous Galerkin approach for FEM, and extensive Parallelization for the FDTD. This development has, in turn, enlarged the scope of the type and size of currently solvable problems that would have been totally unthinkable even just 10 years ago. So, we can rest assured that CEM is not a dead field after all, as some self-appointed pundits would have us believe.Study and evaluation of induced currents in human body from exposure to electromagnetic fields at low frequencies
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.0528
Extremely low frequency (ELF) electromagnetic fields due to low and medium voltages are normally low. But with the wide spread and increase in the use of electrical energy, the potential for exposure has increased considerably. The current research has focused on potential health effects of magnetic fields because some epidemiological studies have suggested an increased cancer risk associated with estimated time of magnetic field exposure. Since the wavelength of ELF electric and magnetic field is sufficiently greater than the dimensions of the biological object, so the electric and magnetic fields can be independently treated. Our main topic in this research is to investigate the effect of magnetic field at power frequency and analyse of the interaction between these fields and the living organisms. We used the measured results and the applied the three techniques of simulating the induced currents in the human body by using a Matlab program. The obtained results can demonstrate the degree of danger due to the induced currents from both magnetic and electric fields. Comparing these results by the values given by International Committee on non-ionizing radiation protection (ICNIRP) guidelines can tell the degree of danger. (4 pages)Influence of dielectric materials on in-vehicle electromagnetic fields
http://dl-live.theiet.org/content/conferences/10.1049/ic.2008.0731
Numerical simulations and analytical models have been used to investigate the possible impact of various dielectric components of vehicles on internal electromagnetic field distributions. It is found that, apart from the window glazing, the dielectrics investigated have little impact on the internal field populations and average field levels, although there are localized field differences that become more pronounced at higher frequencies. Above 1 GHz typical vehicle glazing panels may increase average field levels for internal sources. However, the windscreen may also reduce the field coupled into the interior under horizontal plane wave illumination from the front of the vehicle at lower frequencies. (6 pages)Whither computational electromagnetics? A practitioner's look at the crystal ball
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080252
The paper gives a brief review of the existing CEM solvers in the context of parallel processing, which is the way forward to the future. Next, it would go on to describe three parallel algorithms, based on MOM, FEM, and FDTD, respectively, that may play major roles in the development of parallel CEM solvers.Rogowski Coil performance characteristics for advanced relay protection
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080072
This paper presents Rogowski coil current sensor performance characteristics for advanced relay protection systems. Rogowski coils are specially designed to be immune to external electromagnetic fields. They are accurate and do not saturate. Principles of applications for phasor-based and traveling wave-based relaying schemes are presented. A companion paper [Kojovic, 2008] describes advanced protection schemes that incorporate Rogowski coils and multifunction relays.Experimental tests of an air-cored PM tubular generator for direct drive wave energy converters
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080621
Direct drive power take off eliminates the need for a mechanical interface to match the low speed reciprocating motion of a wave device to high speed rotational motion of conventional electrical generators. However, direct drive generators are physically large and heavy due to the low velocities encountered. Iron cored PM machines suffer from magnetic attraction forces which is challenging for the structural and bearing design. An air-cored machine solves the issue of magnetic attraction forces, which will benefit the mechanical design. The performance of an air-cored PM tubular machine is investigated in this paper under displacements typical of a wave energy device.Application of meshless Petrov Galerkin (MLPG) method in electromagnetic using radial basis functions
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080602
In this work, the meshless local Petrov Galerkin MLPG method is applied to electromagnetic field problems. The method is implemented using radial basis functions (RBF) for interpolation of trial functions instead of the traditional moving least square (MLS) interpolations. Once of the main advantages of this method is that essential boundary conditions are satisfied as in FEM which eliminates the need for additional methods to impose boundary conditions: both globally and compactly supported radial basis functions are considered. The method is evaluated through numerical examples in electrostatic and magnetostatic domains in 1D and 2D, the main objective of these applications is: - to study the effect of RBF on the accuracy by comparing results to those obtained by the traditional MLPG (with lower order polynomial basis), the FEM or exact solutions. - To study the effect of different factors existing in the formulations and calculate optimised factors. Compactly supported radial basis functions provide a promising approach.Electrical Craft Principles, Volume 1
http://dl-live.theiet.org/content/books/el/pbns033e
<p xmlns="http://pub2web.metastore.ingenta.com/ns/">The two volumes of Whitfield's Electrical Craft Principles have been substantially revised and updated in 2008, reflecting changes in practice and legislation (e.g. BS 7671/Requirements for Electrical Installations). The volumes are presented in a new format, are highly illustrated and contain full problems and solutions.</p>3D analytical models for geometry and vector transformations for defects analysis in NDT systems
http://dl-live.theiet.org/content/conferences/10.1049/ic_20070035
The present work deals with the use of 3D analytical transformations in order to establish geometry and vector transformations models for eddy current problems in 3D nondestructive testing systems. The interest of such a transformation is the generation of electromagnetic field for cylindrical problem from only the field distribution known in simpler 3D (x-y-z) geometry. The transformation technique is applied to both geometry and electromagnetic field distribution for objects without defects and those containing an arbitrary volume defect. In order to obtain the validity for the field transformation a comparison with finite elements solution was carried out. (5 pages)Estimation of electric field distribution in wireless office LANS using the FDTD method
http://dl-live.theiet.org/content/conferences/10.1049/ic.2007.1347
The purpose of this study is to examine the Electric Field distribution in wireless office LAN environments. The model used for this study is a common office environment which has objects of varying physical and electrical properties such as desks, chairs and bookshelves, among others. (6 pages)Field estimation and assessing accuracy using Kriging
http://dl-live.theiet.org/content/conferences/10.1049/ic.2007.1346
A novel technique for estimating the spatial electromagnetic field distribution and its covariance error is presented based on variogram analysis and the statistical interpolation technique known as Kriging. The spatial structure of some field measurements are characterised by variogram analyses and their propagation properties identified. The physical implications of the Kriging interpolator functional fit to measured data is considered and illustrated. It is concluded that with specialist interpretation this new technique can be used as a valuable checking tool, or to reduce the number of field measurement, in a measurement programme, particularly when the costs of the latter are considered. (4 pages)Frequency domain surface integral equations of picard's extended Maxwell system
http://dl-live.theiet.org/content/conferences/10.1049/ic.2007.1174
Electromagnetic frequency domain surface integral equations are derived for Picard's extended Maxwell system, a first order partial differential equation system combining linear acoustics and Maxwell's equations into a unified system with correct static behavior. The surface integral equations of the Picard system do not suffer from the low frequency problems of the traditional equations. Three basic types of the equations, similar to the traditional EFIE, MFIE and CFIE formulations, are derived and applied. The numerical behaviors of the equations are studied by comparing the condition numbers, convergences of the iterative solutions, and convergences of the accuracies. (6 pages)Efficient 2D interpolation technique for evaluation of equivalence-principle sources in MoM-FDTD method
http://dl-live.theiet.org/content/conferences/10.1049/ic.2007.1205
In this paper, we demonstrate a possibility of increasing computational efficiency of the MoM-FDTD hybrid method by employing spatial interpolation combined with adaptive sampling in calculating the electric and magnetic field components and equivalent sources on the Huygens' surfaces. Along with the direct spatial interpolation of the electromagnetic field components on the Huygens' surface we also examined the improved interpolation and adaptive sampling scheme employing the non-uniform sampling intervals and well known spatial dependence of the field to smooth it before interpolation. (5 pages)Meeting the requirements in industry
http://dl-live.theiet.org/content/conferences/10.1049/ic_20060010
For industry to meet the challenge of continuous compliance with the EMF Directive, a variety of business disciplines needs to be employed. In general, no new disciplines are required but only extensions and additions to the existing business framework such as codes of practice and quality assurance systems being applied at all stages of design, development, approval, procurement and production.The EMF directive: relevant standards and processes
http://dl-live.theiet.org/content/conferences/10.1049/ic_20060009
This paper discusses the different standards that are relevant in ensuring that industry is able to comply with the Physical Agents (EMF) Directive. These include the CENELEC standards, IEC product standards for mobile phones, base stations, RFID and low-power devices, and new standards covering industrial heating, welding, trains, broadcast and effects on active implanted medical devices. The paper also outlines the assessment process for the different technologies affected by the EMF standards.Power generation industry considerations
http://dl-live.theiet.org/content/conferences/10.1049/ic_20060012
Because of its commitment to the principle of following relevant exposure limits set by government, the electricity industry makes certain it has representation whenever exposure limits are being formulated. Once the guideline or limit is set, however, the industry's policy is that of compliance. This paper systematically identifies and characterizes all compliance issues to enable the electricity industry to supply the information to the HSE to assist them in negotiating the Physical Agents Directive. [Includes 9 Powerpoint slides.]Effective controls in the mobile phone industry
http://dl-live.theiet.org/content/conferences/10.1049/ic_20060011
The UK mobile phone network operators have worked together to develop a methodology for compliance with ICNIRP exposure guidelines. The operators also use an agreed set of RF safety signs and design policy at their base station sites. These policies in conjunction with other good practice support compliance with the Physical Agents (EMF) Directive.Study of discharge process and characteristics of discrete water droplets on the RTV hydrophobic surface in the non-uniform electric field
http://dl-live.theiet.org/content/conferences/10.1049/cp_20061698
According to simulating test on the model sample by using high speed digital camera (10000fps) and combining with ANSYS finite elements analysis software, this paper studies the discharge process of discrete water droplets on the hydrophobic surface in the non-uniform electric field (needle-board electrodes) and computes electric field intensity along hydrophobic surface. The results show that the development trend of the arc is stretching from the double ends to the intermediate on the RTV surface and obvious extinguishing and restriking phenomena can be observed. Furthermore, the paper compares electric field intensity along the RTV hydrophobic surface with no-droplet, one droplet and multi-droplets, and computes the maximum value of electric field intensity. It can be found that the maximum value of electric field intensity with the existence of droplets on the sample surface is 1.22 - 1.44 times as it without the existence of them in the non-uniform electric field. (8 pages)Validation of numerical codes for the simulation of microwave heating and associated gas discharge phenomena
http://dl-live.theiet.org/content/conferences/10.1049/ic_20040107
A number of examples are presented, which validate finite element numerical algorithms developed for the accurate and efficient prediction of the electric field in materials placed within microwave heating applicators and for the characterisation of gas discharges potentially occurring during the operation of industrial systems. The results presented are a successful culmination of numerical simulations coupled with experimental work in order to confirm the validity of the developed algorithms.Accuracy assessment of electromagnetic modelling of a stress measurement instrument
http://dl-live.theiet.org/content/conferences/10.1049/ic_20040111
In the design, manufacture and maintenance of many structures, knowledge of stress is of great importance in assuring integrity. AEA Technology, through its National NDT Centre, has developed a stress measurement technique that is nondestructive and capable of use in-situ. The technique, named 'MAPS', is based on magnetic measurements and is thus restricted to ferromagnetic materials. The processing algorithms are based on analytic models derived by AEA Technology. During the development programme, electromagnetic finite element modelling has made important contributions to improving performance. Recently, such modelling work has been used to gain further insight into the interaction of the MAPS probe with structures, with a view to enhancing the underlying approximate models and consequently extending the capabilities of the MAPS technology. This has involved detailed comparisons of finite element and MAPS instrument data, and a by-product has been the validation of various aspects of finite element modelling. As well as discussing this validation, the paper describes approaches adopted in modelling the MAPS probe and the degree of validation obtained. All the modelling represents the B-H properties nonlinearly and some of the approaches involve anisotropic permeabilities and approximate representation of hysteresis.Implementation of a parallel distributed TLM solver
http://dl-live.theiet.org/content/conferences/10.1049/cp_20040431
This paper describes the design issues in creating a transmission line matrix solver for a distributed network of heterogeneous machines with variable availability. A solution to this problem is discussed, explaining how considerations of performance and security have influenced the implementation of the system.Finite element analysis and experimental test of an axial flux toroidal generator
http://dl-live.theiet.org/content/conferences/10.1049/cp_20040321
This paper describes the development of finite-element models of axial flux toroidal generators. These machines are essentially synchronous generators with flux arising due to permanent magnet excitation and armature reaction currents. 3D magnetostatic FEA of these two cases has facilitated representation of the field MMF by excitation voltage E<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">f</sub>, and the armature reaction by synchronous reactance X<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">s</sub>. Two generators, rated at 20kW and 40kW, have been modelled and the results compared with those obtained from experimental work. The FEA results for Ef lie within 2% of the experimental results, and those for inductance lie within 7.5%. The analysis has then been extended to slotted stator machines. 2D dynamic models have been used to evaluate the excitation voltage and investigate the effects of incorporating rotor skew for the reduction of slot harmonics. (6 pages)Statistical modelling for surrogate functions applied to optimisation process
http://dl-live.theiet.org/content/conferences/10.1049/cp_20040461
This paper deals with two statistical models, kriging and cokriging, to replace the objective function during an optimisation process. Kriging models deal only with function values. A cokriging model is able to deal with function values and their gradients. This ability could improve the quality of the surrogate function and, as a consequence, the optimisation results. The robustness of both approaches is verified on analytical functions and on the TEAM workshop problem 25.Instantaneous power control of induction machines using a novel filtering approach on the back-EMF estimates
http://dl-live.theiet.org/content/conferences/10.1049/cp_20040305
The instantaneous power control algorithm (IPC) has been presented recently as an alternative to field oriented control (FOC) and direct torque control (DTC) for induction machine drive systems. However, implementation issues have prevented experimental results from achieving the results obtained in simulation. This paper addresses the main issue that causes a disparity between the simulation and experimental results - the quality of the back-emf estimates used in the IPC algorithm. In addition, a sensorless control strategy that naturally arises from measurements available in IPC will be briefly discussed. (6 pages)Finite Element Analysis of a novel axial flux PM synchronous machine with excitation control
http://dl-live.theiet.org/content/conferences/10.1049/cp_20040324
The paper presents the benchmarking work of a novel PM synchronous machine using a commercially available 3D FEA package for modelling. The novel synchronous machine uses permanent magnets in combination with a field winding incorporated within the main machine, allowing the field to be adjusted. Firstly, the machine hardware is described with the help of a few FEA plots and the machine operation explained for better understanding of the 3D model. The test results acquired by subjecting a prototype machine to a programme of intense and varied tests, are compared to quantities obtained through running the 3D model. Furthermore, some suggestions are presented in order to improve the software model and the paper ends with conclusions. (6 pages)Analytical analysis and dimensioning of a low-leakage linear transverse-flux machine
http://dl-live.theiet.org/content/conferences/10.1049/cp_20040323
This paper presents a two-dimensional analytical analysis and dimensioning procedure of a novel low-leakage linear transverse-flux machine (TFM). The two-dimensional analytical models approximate the complex three-dimensional fluxes of the TFM. The analysis is based upon how the different airgap permeances and the nonlinear iron reluctances in the different machine sections vary, as the translator is traversed through the airgap. The reluctance networks for the magnetomotive force (MMF) of the magnets and for the current dependent armature-MMF are solved simultaneously. A 5-kW proof-of-concept machine is dimensioned and its performance predicted using the described procedure. The different performance defining parameters are derived as continuous functions of the translator position. The dependence of the machine power factor and the force capability upon the current loading, which is quite interesting when analysing TFMs, is also investigated. (6 pages)Miniature antennas with low proximity effects and filter response characteristics for Bluetooth and 3G applications
http://dl-live.theiet.org/content/conferences/10.1049/cp_20030412
This paper describes an antenna topology (Sarantel) which maintains a high cross-polar gain, is very small and is power efficient. The antenna exhibits an alignment of electric and magnetic minima as well as a far field minimum directed towards the user's head together with balanced electric-field loading across a dielectric core. These attributes minimise the near-field electromagnetic energy that is offered to and dissipated in the user. The high dielectric core stores much of the near field including the potentially frequency changing reactive near field. Together with a balanced feed system that isolates the antenna from the handset, the proposed topology maintains its far field pattern even when the handset is held by energy absorbing human tissue. As the user absorbs little energy, the antenna is power efficient, lowering power consumption of the handset and therefore extending battery life.Wide angle antenna pattern measurements using a poly-planar near field technique
http://dl-live.theiet.org/content/conferences/10.1049/cp_20030028
For planar near-field methodology, if the forward hemisphere is to be determined exactly, the propagating field must be sampled either in the aperture of the antenna or over a plane of infinite extent. In practice, due to the finite extent of the scan plane, any conventional planar near-field measurements inevitably represent a truncated data set, and, as such, any predicted far-field pattern includes errors associated with this truncation. We investigate the possibility of constructing bespoke polyhedral measurement surfaces that enclose the antenna under test and that are suitable for the derivation of the wide-angle antenna performance from measurements made using existing, possibly smaller, planar near-field measurement facilities. The paper shows, through numerical simulation and experimental measurement, that a flat-topped pyramid provides a possible solution to the measurement of high gain antenna patterns in the forward hemisphere using a planar scanner of size of order 1.5 times the size of the radiating aperture. Additionally, it is shown that by enclosing a medium gain antenna (e.g. a corrugated horn) within an imaginary box and measuring the near field on all six sides of the box, using a suitable rotation of the AUT, a prediction of the full spherical radiation pattern of the antenna can be obtained.Transient behaviour of nonlinearly loaded wires in the presence of a dielectric half-space
http://dl-live.theiet.org/content/conferences/10.1049/cp_20030136
The transient analysis of wires having a nonlinear load in the presence of a half-space is carried out directly in the time domain. The nonlinear wire problem is formulated by the time domain Hallen integral equation. The effect of a two-media configuration is taken into account via the reflection coefficient appearing within the integral equation kernel. The resulting integral equation is solved by the space-time Galerkin-Bubnov boundary integral equation method (GB-BIEM). Some illustrative numerical results are presented.Computation of the flux linkage of windings from magnetic scalar potential finite element solutions
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020177
Windings in finite element models are frequently taken into account as regions with given current density J. The layout of the individual conductors is not considered, the total current (the product of the winding current and the number of turns) is assumed to have a given distribution over the cross section of the winding. This distribution is determined by the arrangement of the conductors and is usually, but not necessarily, uniform. The information about the number of turns is provided by the specification of the winding current I. The aim of this paper is to propose ways to compute the flux linkage in this case (even with nonlinearity taken into account) without having to resort to the magnetic vector potential. (2 pages)Optimization of electrode contour based on novel hybrid algorithm
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020154
The genetic algorithm (GA) and tabu search (TS) algorithm are well known. A novel optimization method for continuous variables of global optimization, a hybrid algorithm, is proposed, that is, the TS is embedded into the GA. It combines the advantages of both the GA and IS algorithm, possessing quicker convergence and obtaining global optimum in the highest probability. The feasibility and validity of the proposed hybrid algorithm are verified by solving the typical mathematical function, and the practicability is proved by optimizing the electrode contour. (2 pages)A GRS method for Pareto-optimal front identification in electromagnetic multiobjective synthesis
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020161
Generalized response surfaces (GRS) methods are a well established technique for single-objective optimization in the case of time consuming objective function evaluation. The essential idea is to consider throughout the optimization two different objective functions; the first one be evaluated in as few cases as possible due to its computational cost, the second one is the interpolation of the true objective function via some interpolation technique and it can be evaluated as many time as is needed. Evolutionary multiobjective optimization is a well established computational research area where several powerful methods are available for a fully convergent Pareto optimal front (POF) approximation. The computational cost of multiobjective optimization evolutionary algorithms (MOEAs) is relevant and it may be impractical when industrial design is concerned and the task of reducing objectives function calls is an open research topic. To this aim the link between GRS methods and MOEAs seems to be an appealing alternative. Though very appealing such linking is not straightforward due to the fact that when dealing with multiobjective problems the equivalent of the current optimum region of single-objective problems (an n-dimensional hypersphere centered on the current optimum) is a very complex and often non- connected area of design domain search space; the iterative update-search strategy is thus non-trivial in this case. (2 pages)The equivalence between cell method, TDTD and FEM
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020135
Some equivalences between the cell method (CM) and other methods, like the finite difference in time domain method (FDTD) and the finite elements method (FEM), are proved. In particular the equivalence of the equations arises between CM and electrostatic 3D FEM, between CM and magnetostatic 3D FEM and between CM and FDTD in 3D electrodynamics. (2 pages)Optimization design of electric field using artificial neural networks
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020155
A combination of artificial neural networks (ANN) and the electric field analysis is applied to solve the inverse problem of the electric field. Taking the high nonlinear ability of the ANN and the numerical analysis of the electromagnetic field into consideration, the inverse problem of the electric field for the demonstration examples has been solved. From the calculation results, it can be seen that the proposed method is feasible and valid. (2 pages)