Electromagnetic Field Model Research Articles

Application of the GPR and ERT methods for non-invasive examination of a flood dike

As part of the NAWA-EMMAT project, geophysical surveys were carried out on selected sites in Poland, i.e. on the flood dike and in the surrounding of the concrete water dam. The goal of the surveys was the non- invasive detection of loose zones in the flood dike and fractured zones located in the subsoil of the water dam. Terrain geophysical measurements were conducted with the use of electrical and electromagnetic methods as well as applying seismic methods. Due to the limitations of the length of this paper, only selected results recorded on the flood dike using selected geophysical methods, i.e. electrical resistivity tomography (ERT) and ground penetrating radar (GPR) are presented. The presence of several higher hydraulic permeability zones in the dike was suggested by the results of the ERT method. The GPR method allowed, due to its high resolution, to identify small leakage zones in the body of the dike. An attempt at a quantitative interpretation of the geophysical data was made; for this purpose, the synthetic results obtained from numerical modelling of electrical and electromagnetic fields were applied. For proper construction of numerical models and further interpretation, the results of geotechnical sounding, geological drilling and the results of petrophysical measurements were also used.

О моделировании радиационного электромагнитного поля в полидисперсных средах замкнуто-ячеистой структуры

О моделировании радиационного электромагнитного поля в полидисперсных средах замкнуто-ячеистой структуры

МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ МАГНИТОТЕЛЛУРИЧЕСКОГО ПОЛЯ В ОДНОМЕРНЫХ КУСОЧНО-ГРАДИЕНТНЫХ СРЕДАХ

The solution of forward problems of magnetotelluric sounding for a case of one-dimensional piecewise gradient environments is received. Two problems are considered: the problem of calculating the impedance on the Earth’s surface for a gradient model of the upper half-space (Earth's atmosphere) and the problem of determining the magnetotelluric impedance for layered, piecewise-gradient models of the geological medium, which allow mathematical modeling of the magnetotelluric response functions and study the interaction of electromagnetic field and gradient models of lithosphere media. Such models extend the possibilities of development of the theory and practice of magnetotelluric research, first of all, when solving inverse problems, which is associated with the advantage of analytical solutions over numerical solutions of inverse problems of geophysics in terms of sharp reduction of their dimensionality. The main focus of the work is on the study of geodynamic processes in passive electromagnetic monitoring, the foundations of which are laid in the article (Alexandrov, Rybin, Zabinyakova, 2018).

Computer models in problems of ensuring electromagnetic safety

In the process of the smart grids formation a special attention is started to be paid to the issues of power engineering facilities safe functioning and reduction in their negative impact on personnel and environment. One of the important factors of such an impact is the generation of significant levels of strength of electromagnetic fields (EMF) by high-voltage overhead power transmission lines (OPL). In the context of the electric power industry digitalization, in order to improve the electromagnetic safety of service personnel, development of methods and means for digital modeling of EMF created by power lines of various designs is required, including traction networks of electrified railways. Computer models providing an adequate determination of the OPL EMF can be implemented on the basis of methods and tools designed for determining the parameters of the modes of electric energy systems in phase coordinates, developed at the Irkutsk State University for Railroads Communications. As an example of using these methods, the solution to the problem of constructing pictures of the distribution of EMF in the space surrounding the intersection of a flexible symmetrical conductor and a 25 kV traction network is given.

Design and thermal analysis of a novel permanent magnet-friction integrated brake for vehicle

This article focuses on a new type of permanent magnet-friction integrated brake. The design scheme of integrated brake is proposed. Taking the maximization of braking moment and the minimization of volume as the dual optimization objectives, the particle swarm optimization algorithm is used to optimize the integrated brake, and the main structure parameters of the integrated brake are obtained. Based on the obtained structure parameters, the 3-D model of integrated brake is established. The mathematical models of electromagnetic field and temperature field of integrated brake are given, respectively. Taking a typical braking process as an example, the magnetic field of integrated brake is analyzed based on COMSOL software, which verifies the correctness of the design model of permanent magnet brake. The eddy current loss in the magnetic field of permanent magnet brake and the thermal contact of friction brake are taken as heat sources of the integrated brake, then the temperature field of integrated brake is analyzed. The analysis results show that the integrated brake meets the requirements of braking performances, and improves the heat recession resistance compared with the traditional friction brake.

Influence of Extension Length of Rotor End Windings on the Three-Dimensional Electromagnetic Field and Temperature Rise in the Large Turbine Generator End Zone With Magnetic Screen

Leakage magnetic field from the rotor end windings affects obviously the electromagnetic losses and temperature of end components in the turbine generator end zone with magnetic screen. As the capacity of turbine generator increases, this effect of rotor end windings has become more prominent. To investigate influence of the extension length of rotor end windings on the electromagnetic and thermal fields in the turbine generator end zone with magnetic screen, three-dimensional transient electromagnetic field model of 1250 MW turbine generator end zone is given. Leakage magnetic field and losses of end components are compared and studied in the end zone under the different extension lengths of rotor end windings. Based on the calculation results of electromagnetic losses (heat sources) and flow network (boundary conditions), three-dimensional fluid-thermal coupling field is calculated in the turbine generator end zone with magnetic screen. Distribution of complex fluid velocity in the end zone is obtained. Influence of the different extension lengths of rotor end windings on the stator-end copper coil, screen plate, finger plate, press plate, magnetic screen, and stator end core is researched in the turbine generator end zone. The accuracy of calculation results is validated by experimental values.

Influence of a Novel Stator Teeth Internal Ventilation Structure on Air-Cooled Turbo-Generator Parameters and Stator Temperature

In order to solve the problems of severe heating and cooling difficulty in the stator of air-cooled turbo-generator, a novel stator teeth internal ventilation structure with axial vents in the generator stator teeth is proposed. Based on this structure, global two-dimensional electromagnetic field models of 150MW air-cooled turbo-generator with different stator tooth internal ventilation structures are established to study the influence of the axial vents of the internal ventilation structure on air gap magnetic flux density of the generator, magnetic flux density of stator teeth, stator core loss, and synchronous reactance. Furtherly, flow network models of the ventilation system with different internal ventilation structures and fluid-heat transfer numerical models of stator with half axial and one tooth pitch of generator are established to calculate the effects of the structure on the temperature of stator winding, insulation and teeth. It can provide a new research idea for the ventilation structure of large air-cooled generator.

Analysis of Electromechanical Processes in Asynchronous Machines during Tests by the Loading-Back Method with Energy Recovery in the Network

The article discusses the interrelated electromechanical processes in asynchronous machines when testing by the loading-back method with energy recovery in the network. We analyze a system of two asynchronous machines connected by a common shaft, in which one machine operates as an engine with the voltage supply of increased frequency from the frequency converter and the external machine operates as a network generator. Electromechanical processes in machines have an influence on each other. We have carried out the simulation of electromechanical processes in the motors with allowance for several factors—namely, different degrees of saturation of magnetic cores, torque equalization, and the change in parameters of the windings when changing the operating mode with a nonsinusoidal voltage supply to the asynchronous motor from the frequency converter. A modeling technique with mutual matching of the electromagnetic field models of machines through the relationship of torques on the shaft, based on system minimization of the electromagnetic energy functionals has been presented. The results of simultaneous numerical calculations of interrelated electromagnetic fields in machines and electromechanical processes have been presented. The calculations of electromechanical processes and the characteristics of an asynchronous motor–generator system with a common shaft, mutual load and energy recovery in the network have been performed. The results of experimental studies of a two-machine unit are presented, confirming the theoretical results. It is established that the application of the calculation technique with direct computing the interrelated electromagnetic fields in the engine and generator with allowance for the electromagnetic torque on the shaft provides an error of no more than 7% compared with the experiment.

Accuracy investigation of equivalent dipole arrays for near‐field estimation in presence of shielding or dielectric structures

AbstractThe accuracy of equivalent dipole arrays for source modeling of electromagnetic fields is affected by several factors. In the step for extracting equivalent dipole arrays for a given source, there are three factors that can affect accuracy: scanning height, source spacing, and scanning gap. In the evaluation step of reconstructed fields, there are two other factors that can also affect accuracy: evaluation height and additional structures. In this paper, simple guidelines are suggested considering the three factors in extracting equivalent dipole arrays. Also, the effects of the evaluation height on accuracy of reconstructed fields are demonstrated in the presence of shielding or dielectric structures. A feature selective validation process was utilized to evaluate similarities between actual and estimated fields.

Three-dimensional electromagnetic field model of an auger electromechanical converter with an external solid rotor

This research would not have been possible without the support provided under the state-financed scientific research theme “Development of subsystem for predicting and controlling the dynamics of methane content at mines”. The authors express their gratitude to Professor Mykola Antoshchenko for assistance in conducting the research.

CORRECTNESS OF A MIXED PROBLEM FOR DEGENERATE THREE-DIMENSIONAL HYPERBOLIC-PARABOLIC EQUATIONS

In mathematical modeling of electromagnetic fields in space, the nature of electromagnetic process is determined by the properties of the medium. If the medium is non-conducting, we obtain degenerate three-dimensional hyperbolic equations. If the medium has a high conductivity, then we come to degeneratethree-dimensional parabolic equations. Consequently, the analysis of electromagnetic fields in complex media (for example, if the mediums conductivity changes) is reduced to degenerate three-dimensional hyperbolic-parabolic equations. The mixed problem for multidimensional hyperbolic equations is well studied and has been previously considered in the works of various authors. In the articles of Professor S.A. Aldashev, the unique solvability of the mixed problem for degenerate multidimensional hyperbolic equations is proved. It is known that mixed problems for multidimensional hyperbolic-parabolic equations have not been studied much. The paper finds a new class of degenerate three-dimensional hyperbolic-parabolic equations for which the mixed problem has a unique solution and gives an explicit representation of its classical solution.

A case study of rupture in 110 kV overhead conductor repaired by full-tension splice

Rupture accidents of overhead conductors may occur due to its complex operating environment. If wires rupture happens, the overhead conductors can be repaired by full-tension splice (FTS) in practical engineering to restore the mechanical strength and ampacity required. However, with time increases, ageing will occur on the overhead conductors. There may exist potential of rupture in the repaired segment of the conductor. Once the conductor is broken, the reliability of transmission line will be seriously destroyed. Therefore, it is of great importance to investigate the rupture reason and process of conductor repaired by FTS. In this paper, a rupture accident of 110 kV overhead conductor repaired by FTS is discussed. Firstly, the fractography analysis for the conductor sample is conducted, and the rupture reason is preliminarily inferred according to the rupture feature of the sample. Then, the current density distributions in the repaired segment of new conductor and aged conductor are compared by a finite element analysis (FEA) model of electromagnetic field. Also, the reason of high temperature produced in the conductor sample during rupture process is determined. Subsequently, to analyze the relationship between temperature and equivalent plastic strain, a FEA model of structure field for the steel core of conductor is established. Finally, combined with the fractography test results and simulation results, the rupture mechanism of conductor repaired by FTS is summarized in detail. The analytical method and conclusions proposed in this paper can provide references and suggestions for the study of similar conductor rupture accident and optimization of repaired process.

Modeling and Practical Implementation of a Broadband Double-Ridged Horn Antenna with an Operating Range More Than an Octave and a High Level of Cross-Polarization Discrimination

Introduction. The resolution of the problem of radio polarimetry in multiposition microwave screening systems (MMSS) with aperture synthesis requires the use of antennas with a high level of cross-polarization discrimination (XPD) in a wide spatial angle. The radio images are reconstructed in MMSS at distances commensurate with the aperture of the antenna structures. Therefore, the value of the spatial angle, at which high XPD is required, can reach 30°. This leads to a new problem of creating an antenna configuration of the X and Ku band, the application of which in MMSS will resolve the problem of constructing a radio image of depolarized microwave radiation scattered on the human body in the form of hidden dangerous objects.Aim. To develop a double-ridged receiving antenna for long-term operation in MMSS with an XPD level of 28 dB at a spatial angle of 30° and operating frequencies of 8…20 GHz.Materials and methods. The requirements for the receiving antenna in MMSS were determined. Theoretical justifications were proposed for the choice of antenna design. Aperture synthesis was used to construct microwave images in MMSS. The stages and results of modelling broadband double-ridge antennas were presented using the CST Studio software broadly applied for three-dimensional electro-magnetic field modelling. The results of modelling pyramidal and conical double-ridged antennas, as well as those in circular and elliptical waveguides, were analyzed. The designed antenna was tested in an anechoic chamber. The measurement results were compared with those obtained during simulation.Results. An elliptical double-ridged horn antenna with a VSWR of no more than 2 and cross-polarization discrimination in a spatial angle of 30° of no less than 28 dB for the frequency range that covers an octave was designed and constructed.Conclusion. The developed antenna can be used in MMSS for the purpose of detecting the effect of micro-wave radiation depolarization as hidden dangerous objects on a human body. Such characteristics of the antenna as its high XPD value in a wide spatial angle will allow the future introduction of microwave polarimetry in MMSS.

Influence of inverter output voltage harmonic on surface-mounted permanent-magnet synchronous motor performance

The application of an inverter is becoming more and more widespread in the surface-mounted permanent-magnet synchronous motor (SMPMSM). A large number of voltage harmonics can be generated by the inverter. The electromagnetic torque, loss, and air-gap magnetic density of the SMPMSM are affected by voltage harmonic. To analyze its influence, taking a 3 kW 1500 r/min SMPMSM as an example, a two-dimensional transient electromagnetic field model is established. The correctness of the model is verified by comparing the experimental data with the calculated data. Firstly, the finite element method is used to calculate the electromagnetic field of the SMPMSM, and the performance parameters of the SMPMSM are obtained. Based on these parameters, the influence of voltage harmonic on motor performance is analyzed quantitatively. Secondly, the influence of the voltage harmonic on the air-gap magnetic field is analyzed, and the influence degree of the time harmonic on the air-gap magnetic field is determined. At the same time, torque ripple, average torque, and loss are studied when the different harmonics orders, amplitudes, and phase angles are contained in voltage, and the variation is obtained. Finally, the variation mechanism of eddy current loss is revealed. The conclusion of this paper provides reliable theoretical guidance for improving motor performance.

Modeling and Analysis of Signal Integrity of High-Speed Interconnected Channel With Degraded Contact Surface

High-speed interconnected channels, including printed circuit boards (PCBs) and high-speed connectors, are widely used in digital baseband communication systems. Connector degradation may lead to deterioration of the integrity of digital signals and is one of the major causes of low communication quality. In this work, the effect of electrical contact degradation on signal integrity was investigated using model analysis and experimental testing. A 3-D electromagnetic field model of a high-speed channel with a degraded contact surface was developed to evaluate transmission loss, signal reflection, and crosstalk. Using multiconductor transmission line theory and contact physics, a distributed parameter circuit model of a high-speed channel with a degraded contact surface was also developed. The electromagnetic field model results are in good agreement with those obtained from the distributed parameter circuit model. Both the electromagnetic field model and the circuit model results are validated using experimental tests. The results of this investigation provide a better understanding of the characteristics of signal transmission through a degraded contact surface in a high-speed channel and theoretical support for identifying failure features in fault diagnosis.

Mathematical modeling of MHD processes in the casting of aluminum alloys in electromagnetic mold

The article contains the overview of mathematical modeling of electromagnetic field and magnetohydrodynamic process of the ingot moulding during casting into the electromagnetic mold. We have formulated the system of equations describing the molding process. The authors describe the principle of casting into the electromagnetic mould to produce small diameter ingots, as well as the results obtained. This article gives the analysis of magnetohydrodynamic flows in the area of molding and their impact on the resulting ingot. It is shown that the intensity of the MHD processes is influenced by the frequency of the supply voltage and the shape of the crystallization front. The calculations are based on favorable conditions for the formation of a homogeneous, fine-grained structure. The experimental studies were conducted using samples of aluminum alloy 01417.

Моделирование электромагнитных полей систем катодной защиты трубопроводов в горизонтально-слоистых средах

Моделирование электромагнитных полей систем катодной защиты трубопроводов в горизонтально-слоистых средах

Influence of Electromagnetic Characteristics of Shaft Material on the Performance of Induction Motor

Abstract Shaft is an important part of rotor, whose electromagnetic characteristics have an impact on the performance of the motor, especially when large diameter shaft and thin rotor yoke are adopted in the two-pole induction motor. Taking a 3 kW two-pole three-phase induction motor as an example, the two-dimensional electromagnetic field model of the motor is established by using finite element method. Firstly, by analyzing the difference of current, power factor, loss and magnetic field distribution of the motor with different shafts that are made from ferromagnetic and non-ferromagnetic materials. It is determined that the different magnetic saturation degree of rotor yoke is the key factor affecting the performance of motor when different shaft materials are used. Secondly, it is verified that the traditional analytic design method has the inaccurate design problem of the rotor yoke height due to neglecting the specific electromagnetic characteristics of shaft material. Finally, by comparing the differences of motor performance when several common magnetic shaft materials are used in motor shafts, the advantages of various shaft materials in improving motor performance are found. The presented results give guidelines to selecting shaft materials to improve motor performance.

Transient analysis with coupled field-circuit model and experimental assessment of a PMSG used in small-scale wind turbine for water heating purpose

This paper introduces the detailed coupled field-circuit analysis including performance characteristics of a 4-kW in-running rotor permanent magnet synchronous generator (PMSG) used in rural-type small-scale wind turbines for water heating purpose. The content of the work consists of design, analysis, optimization, production and testing processes and validation studies. An integrated 2D electromagnetic field and circuit model are used in the design and analysis processes. The electrical machine design involves complex and time-consuming processes. This model provides comprehensive information on machine behavior under different conditions and is an effective to demonstrate compliance with real load conditions prior to the manufacture. The goal of the optimization process is to find a design that offers cost, manufacturability and efficiency as well as generator output values. For this, a multiobjective optimization approach has been used. Typical design and simulation principles are applied to the designed PMSG, respectively, including calculation and evaluation of various output parameters for different simulated wind speed rates and varying load conditions. Furthermore, the analytical studies related to finite element methods and parametric approaches are presented in collaboration with experimental studies carried out for different load rates.

Geometrical Platform of Big Database Computing for Modeling of Complex Physical Phenomena in Electric Current Treatment of Liquid Metals

According to the principles of multiphysical, multiscale simulation of phenomena and processes which take place during the electric current treatment of liquid metals, the need to create an adjustable and concise geometrical platform for the big database computing of mathematical models and simulations is justified. In this article, a geometrical platform was developed based on approximation of boundary contours using arcs for application of the integral equations method and matrix transformations. This method achieves regular procedures using multidimensional scale matrices for big data transfer and computing. The efficiency of this method was verified by computer simulation and used for different model contours, which are parts of real contours. The obtained results showed that the numerical algorithm was highly accurate based on the presented geometrical platform of big database computing and that it possesses a potential ability for use in the organization of computational processes regarding the modeling and simulation of electromagnetic, thermal, hydrodynamic, wave, and mechanical fields (as a practical case in metal melts treated by electric current). The efficiency of this developed approach for big data matrices computing and equation system formation was displayed, as the number of numerical procedures, as well as the time taken to perform them, were much smaller when compared to the finite element method used for the same model contours.