Extraneous Currents Research Articles

Features of Electrical and Magnetic Skin Effect Modeling from Alternating Electromagnetic Fields in FEMM

Electromagnetic field theory is still one of the most difficult areas in electrical engineering studied by students of specialized universities. Computer simulation learning this section more efficiently. This is especially important with for improving students' individual work in modern educational programs. However, even fairly advanced computer modeling tools have some hidden features. The article is devoted to overcoming the difficulties that arise when using the FEMM program for modeling alternating electromagnetic fields. It is shown that the influence of the electrical skin effect in ac conductors is modeled incorrectly in FEMM. In turn, the influence of the magnetic skin effect in workpieces without extraneous currents placed in the magnetic field of the inductor at a given frequency is simulated correctly. Examples of field models for the variants under consideration are given.

Особенности моделирования электрического и магнитного поверхностного эффекта от переменных электромагнитных полей в Femm

The electromagnetic field theory still remains among of the most difficult sections of electrical engineering that are studied by the students of relevant universities. Computer modeling is a modern tool that helps master this section in a more efficient way. This is especially important in view of the trend toward increasing the role of independent work assigned to students in the modern educational programs. However, even quite advanced computer modeling tools still contain some hidden features. The article addresses the problem of overcoming the difficulties encountered in using the FEMM computer program for modeling alternating electromagnetic fields. It has been found that the way in which the FEMM computerprogram models the influence of the electrical skin effect in alternating current conductors is incorrect. At the same time, the FEMM computer program models the influence of the magnetic skin effect in billets free from extraneous currents placed in the magnetic field of an inductor at a specified frequency is a correct way. Examples of field models for the considered cases are given.

A Numerical Method of Determining Permittivity from the Modulus of the Electric Intensity Vector of an Electromagnetic Field

The system of equations of electrodynamics is considered for a nonmagnetic nonconducting medium. For this system, the problem is under study of determining the permittivity e from the given modulus of the electric intensity vector of the electromagnetic field that is the result of the interference of the two fields generated by some point sources of an extraneous current. It is assumed that permittivity is different from a given positive constant e0 only inside a compact domain Ω0 ⊂ ℝ3, whereas the modulus of the electric field intensity vector is given for all frequencies starting from a fixed frequency ω0 on the boundary S of some domain Ω that includes Ω0. It is shown that this information allows us to reduce the original problem to the well-known inverse kinematic problem of determining the refraction index inside Ω by the travel time of the electromagnetic wave between the points of the boundary of this domain. The algorithm for numerical solution of the inverse problem is constructed, and the test calculations on the simulated data are presented.

MODELING OF THE COMPRESSION OF WAVE PACKETS INDUCED BY A CURRENT FILAMENT IN A PLANE-PARALLEL WAVEGUIDE

The possibility of rigorous simulation of the compression of electromagnetic pulses excited by a filament with a current in a plane-parallel waveguide cavity is investigated. The technique of determining the modulation law of the pulses to be compressed, that has been developed in our previous papers, here is generalized to the case where the pulse source is an extraneous current. The process of compression is modeled with this technique for two symmetrical wave packets propagating towards each other in a ring-shaped waveguide. The interference of these packets is demonstrated in the performed numerical experiment. The result of the interference is doubling of the electric field intensity (regarding to the intensity in each separate wave packet) at the point of the waveguide which is diametrically opposed to that one where the external current is located. The obtained results could be used for the design of passive microwave power compressors and in the accelerator engineering.

Initial-boundary value problem of electromagnetic testing of a flawed ferromagnetic conductor by the residual field of an instantaneously cut-off current

An initial-boundary value problem of electrodynamics is considered for a flawed metal ferromagnetic body that is placed in the field of an instantaneously cut-off extraneous current. A generalized statement of the problem has been found that guarantees the uniqueness of solution and its continuous dependence on the initial data under fairly sweeping assumptions about the conductivity and permeability of the body as well as the smoothness of boundaries of the body and the flaws. Possible generalizations are pointed out for the results to include ferromagnetic conducting bodies that are placed in the field of permanently switched-on current.

Investigation of spherical and cylindrical Luneburg lens antennas by the Green's function method

Luneburg lens antenna radiation fields are calculated with Green's functions of spherical and cylindrical layered structures. Electric field components of spherical and cylindrical Luneburg lenses excited by linear and circular polarized incident field are analysed. Dipole, slot and aperture antennas are described by electric and magnetic extraneous currents. Radiation patterns of cylindrical and spherical Luneburg lens are analysed. Co-polarized and cross-polarized field radiation patterns are shown. The proposed method significantly reduces the computing time for multi-layered lenses in comparison with the most commonly used in antenna design. The first step antenna structure optimization may be performed for a shorter time. The results may be used as the first approximation for Ansys HFSS and other software.

An initial-boundary value problem of structurescopy of a nonferromagnetic metal solid with foreign dielectric inclusions using the residual field of an instantaneously cut-off extraneous current

An initial-boundary value problem of electrodynamics is considered for the structurescopy of a nonferromagnetic metal with foreign dielectric inclusions; it is assumed that structurescopy is carried out using the residual electromagnetic field of an instantaneously cut-off extraneous current. Under the fairly sweeping assumptions on the electric conductivity of the solid, the dielectric permittivity of the foreign inclusions, and the smoothness of the boundaries of the solid and the inclusions, it has been proven that the initial-boundary value problem of electrodynamics under consideration has a unique solution, which depends continuously on the initial conditions.

Excitation of a waveguide transformer

Integral immitance equations for steady-state excitation of a shielded waveguide transformer with any number of arbitrarily arranged adjoint semi-infinite waveguides are derived in the general formulation. Excitation can be carried by arbitrary inner sources (extraneous electric and magnetic currents), as well as by normal modes incident from infinity. The results are extended to the case of nonideal walls for magnetodielectric and metallic inclusions. The results give a generalization of the familiar integral impedance and admittance equations for inhomogeneous waveguides.

Influence of an Extraneous Electric Current on the Stress State of an Annular Plate of Variable Rigidity

Two-dimensional magnetoelastic equations are derived and an algorithm is proposed to solve a boundary-value problem for an annular plate of variable rigidity under the action of an extraneous electric current. A numerical example is given

Parametric interaction of space-charge waves in thin-film semiconductor structures

The general theory of parametric coupling between space-charge waves and drifting charge carriers in thin-film semiconductor structures has been worked out. This theory is applicable, in particular, to n-GaAs and n-InP semiconductors with negative differential conductance due to intervalley electron transitions under high electric fields. We started from the electrodynamic theory of waveguide excitation by extraneous currents, which was extended for arbitrary waveguide structures with composite active media. Our theory makes it possible to study parametric interaction between space-charge waves in semiconductor films with regard for boundary conditions, diffusion, the anisotropy and the frequency dispersion of the differential electron mobility, as well as the multifrequency and multimode nature of a wave process in thin-film structures.

The coupled application of the B-spline wavelet and RLT filtration in staircase voltammetry

In this paper, a new coupled method of the B-spline wavelet and RLT filtration is presented. The B-spline wavelet is a new chemometrics technique to process signals. It is especially appropriate for processing nonstationary signal noise. RLT filtration can be used to remove extraneous currents from faradaic current, but it is not suitable for filtering random noise. The coupled application of these two methods in staircase voltammetry can filter not only random noise but also extraneous currents. Signals of S/N (signal-to-noise ratio)=0.8 can be filtered. The errors of the peak current are less than 5% and those of the peak potential are less than 1%. The processed results of experiment data are also satisfactory.

Simultaneous application of spline wavelet and Riemann–Liouville transform filtration in electroanalytical chemistry

The spline wavelet can be applied to the processing of signals. It is particularly appropriate for processing nonstationary signal noise. Riemann–Liouville transform (RLT) filtration can be used to remove extraneous currents from faradaic current, but it is not suitable for filtering random noise. Spline wavelet and RLT filtration are combined for the first time to filter random noise as well as extraneous currents. Signals with a signal-to-noise ratio of 0.8 can be filtered. Results of processing experimental data are satisfactory.

Staircase pulse voltammetry

AbstractThe faradaic current of interest can often be obscured by some extraneous current. A new method called staircase pulse voltammetry (SPV), with which involving a potential pulse is superimposed on a staircase, is used for removing the double‐layer charging current This paper presents the theoretical consideration and the experimental evidence of this method for a simple reversible system and a catalytic process. The parameters affecting currents are also discussed. Experimental verifications are in agreement with the theories.

A theory of transverse small-scale standing Alfvén waves in an axially symmetric magnetosphere

For a model of an axially symmetric magnetosphere we have constructed a theory of standing Alfvén waves with large azimuthal wavenumbers, m ⪢ 1. It is supposed that the source for such waves can be provided by extraneous currents in the ionospheric E-layer. A monochromatic source excites an oscillation of the poloidal type on the magnetic shell, having an eigenfrequency of poloidal oscillation that coincides with the source frequency. This wave, while travelling across the magnetic shells, changes from the poloidal into the toroidal wave. On the magnetic shell, whose frequency of toroidal eigenoscillations coincides with the frequency of the wave concerned, it is totally absorbed due to energy dissipation in the ionosphere.

Cottrell filtration: removal of extraneous currents from a faradaic signal

The faradaic current from a cottrellian experiment can often be obscured by other currents arising from extraneous sources. The operation of Cottrell filtration is developed and simulation studies are presented which illustrate the success of this filter for the removal of a variety of plausible extraneous currents.

Cottrell filtration: Removal of extraneous currents from a faradaic signal

The faradaic current from a cottrellian experiment can often be obscured by other currents arising from extraneous sources. The operation of Cottrell filtration is developed and simulation studies are presented which illustrate the success of this filter for the removal of a variety of plausible extraneous currents.

Calculation of the electromagnetic fields of a non-stationary source of gamma quanta in the self-consistent model

The electromagnetic fields of a non-stationary gamma source on the earth's surface with finite conductivity are calculated by solving the mixed problem for Maxwell's equations. A two-dimensional non-linear model is used for the solution; the model takes account of the reverse influence of the inherent magnetic field on the extraneous currents and the conductivity of the medium.

Improved magnetic retarding system for watthour meters

Because of the squared relationship between the flux and braking torque of the retarding magnet of the watthour meter, and the need to maintain high meter accuracy under all operating conditions over long periods of time, stability of the magnet is essential. Over the years, this stability and the resistance to demagnetization by extraneous magnetic fields or short-circuit currents have increased with each new material development applied to the retarding system of the meter. A continuation of this series of improvements is currently taking place with the introduction of rare earth magnets.

A Guide for the Protection of Wire Line Communications Facilities Serving Electric Power Stations

Some of the wire communications circuits entering electric power stations are used for control and relaying purposes and often are called upon to perform certain operations during periods of power system faults. This constitutes a major problem in the design of the communications system, since power faults usually result in the introduction of extraneous currents and voltages into the commuuications circuit just at the time when the latter is most urgently required to perform its function.

Chronopotentiometer with Compensation for Extraneous Currents.

Chronopotentiometer with Compensation for Extraneous Currents.