Calculation Of Current Distribution Research Articles

Investigation of current flow in the bars of radially-ducted cage rotors using a three-dimensional finite-element eddy current formulation

The authors describe the application of a three-dimensional eddy current formulation to the problem of the calculation of the current density distribution in the bars of cage rotor induction machines with radially ducted rotors under steady-state conditions. The most suitable choice of formulation and its application to the ducted rotor problem are considered, and the rotor model and boundary conditions are described. Results are given in terms of the variation of the current density distribution and power loss along the bar, illustrating the effect of the ducts on the bar resistance. >

Calculation of steady-state distributions of concentrations and potential controlled by diffusion and migration of ions

A numerical method is proposed for the calculation of concentration, potential, and current distributions in electrochemical cells controlled by diffusion and migration of ions. Thus a hypothetical variablev(x, y, t) is assumed to satisfy a differential equation which is similar to that of non-steady-state heat conduction and corresponds, at steady state, to Poisson's equation for the potential. The differential equation forv(x, y, t) and the diffusion-migration equations of ions are simultaneously solved by a finite difference method. Examples of calculation are given for single and mixed electrolyte solutions in one- and two-dimensional cells. The proposed method is applicable to systems in which bipolarity occurs.

Dependence of CIT PF Coil Currents on Profile and Shape Parameters Using the Control Matrix

The plasma shaping flexibility of the Compact Ignition Tokamak (CIT) poloidal field (PF) coil set is demonstrated through magnetohydrodynamic (MHD) equilibrium calculations of optimal PF coil current distributions and their variation with poloidal beta, internal inductance, plasma 95% elongation, and 95% triangularity. Calculations of the magnetic stored energy are used to compare solutions associated with various plasma parameters. The Control Matrix (CM) equilibrium code,1 together with the nonlinear equation and numerical optimization software packages HYBRD2 and VMCON3 respectively, is used to find equilibrium coil current distributions for fixed divertor geometry, volt-seconds, and plasma profiles in order to isolate the dependence on individual parameters. A reference equilibrium and coil current distribution are chosen, and correction currents dI are determined using the CM equilibrium method to obtain other specified plasma shapes. The reference equilibrium is the κ = 2 divertor at beginning of flattop (BOFT) with a minimum stored energy solution for the coil current distribution. The pressure profile function is fixed.

Normalized and Average Current Distributions on Unevenly Spaced Patterns

Spatial variations in electrochemical etch rate are predicted for an unevenly spaced pattern of lines. Two models, based on primary current distribution calculations, are presented. One model is used to estimate the normalized current distribution on an individual line of the pattern. The results indicate that the model, which accounts only for the placement of the nearest neighbor lines while ignoring the other geometric details, predicts well the primary current distribution. The other model, based on boundary integral equations, is used for an estimation of the distribution from line to line of the average current densities. The results, which agree with experiment, are insensitive to the details of the normalized current distributions that are assumed on the individual lines in the pattern.

Computation of current distribution in electrodeposition, a review

Computation of current distribution in electrodeposition, a review

Application of the Boundary‐Element Method to Offshore Cathodic Protection Modeling

This paper deals with the main aspects of the calculation of current and potential distributions and summarizes some results obtained on different systems using a computer program based on the boundary‐element method. Model results are compared to literature data for well‐known geometries, and to experimental data obtained both in laboratory testing with a suitable cell and in field testing on offshore structures (in particular platform nodes). The good predictive capability of computer modeling is shown.

Studies of current distribution in large-scale superconducting cables influenced by internal and external magnetic fields

Round multiwire superconducting cables and subcables, used in complex cables, have been studied. The calculation of current distribution between the layers in a multiwire subcable or cable is given. It is shown that the main parameters influencing the current distribution are the geometry of the layers, the diameter of superconducting elements in the layers and the ratio between the values of external magnetic field and subcable current. Recommendations are given as to the design of multiwire subcables and twisted layer conductors.

Numeric calculation of current distribution in the damper cylinder of a large superconducting generator

The calculation of the subtransient reactance, winding forces, and surface losses in large superconducting turbogenerators with an air-gap stator winding must start from the three-dimensional magnetic stator winding field. A calculation method for the damper current distribution is presented that approximates the damper cylinder by a grid of short-circuited loops with an infinite conductivity. The magnetic field of the stator winding and the field of the damper cylinder are calculated by the Biot-Savart law. The loop currents are calculated by iteration. As a sample result, damper current distribution plots are shown for a generator with a special type of high-voltage stator winding called the coaxial turn winding.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Localized hyperthermia by means of a paired-coil configuration: Calculation of current distributions in cubical model

A method of localized hyperthermia of deep tissues by means of paired-coil arrays is proposed. The basic idea is to concentrate induced eddy currents in the vicinity of target tumors locally by paired coils positioned outside the body. Two coaxial pairs of coils are positioned on the surface of the body in parallel with each other in such a manner that the magnetic fields pass through the body in opposite directions around the target focus. To demonstrate the effectiveness of the method, spatial distributions of induced eddy currents are obtained in a cubical model by a finite element method.

Calculations of the Josephson current distribution in two-dimensional tunnel junctions

A numerical method has been developed for the calculation of the time-independent Josephson current distribution in two-dimensional tunnel junctions. Results obtained with this method agree well with experimental measurements of the Josephson current distribution using low temperature scanning electron microscopy.

Investigation of the Turn-off Behaviour for the Design and Development of High Current GTO Thyristors

Understanding of the turn-off behaviour of parallel connection of multitude of elementary thyristor units constituting the GTO (Gate Turn Off) thyristor is of primary importance for the development of the GTO thyristors with high current and voltage ratings. The maximum turn-off current was measured on test structures with emitter length, emitter width and gate contact width varying from 2 to 6 mm, 150 to 350/um and 100 to 500/um, respectively. The emitters had both constant and varied width and number of emitters was from 1 to 14. The uneven current load sharing between emitters explains following findings: The nonlinear dependence of the maximum turn-off current on the number of emitters connected in parallel and deviation from theoretically predicted inverse proportionality between maximum turn-off current and emitter width which is shown to hold for single emitter. The influence of the lateral voltage drop in the gate metallization on the maximum turn-off current is demonstrated and results agree well with two- dimensional computer calculations of current flow and potential distribution.

Application of the boundary matching method to elliptic conductors

A boundary matching method for the calculation of current density distribution in a long conductor with arbitrary cross section is presented in another paper. An example is given here treating an elliptical cross section. Explicit expressions for the current density distribution and conductor internal impedance are obtained. The current density and impedance are evaluated for elliptic conductors with different ellipticity. Experimental and published data confirm the analysis.

Calculation of Current Distribution and Electrode Shape Change by the Boundary Element Method

The boundary element method coupled with a Newton‐Raphson iteration technique is used to determine current distributions in electrochemical systems, particularly for applications involving electrode shape change such as electroplating and electrochemical machining (ECM). The derivation of the system of equations with the appropriate boundary conditions is presented. Primary and secondary current distributions are calculated for applications including simultaneous deposition and dissolution on opposing electrodes. In the case of copper electrorefining, a comparison between theory and experiment is made. An example of surface leveling in ECM is also given.

Normalized Force-Speed Curves of Eddy Current Brakes with Ferromagnetic Loss Drums

The paper presents a set of normalized force-speed curves of a salient pole eddy current brake with Prohlich B-H characteristic for the loss drum, taking the air-gap flux distortion into account. With reasonable assumptions, the calculation of eddy current distribution in the loss drum can be simplified to the solution of a 1-dimensional nonlinear diffusion equation with an implicit boundary condition. This equation is normalized and solved numerically by a stable iterative scheme. The normalized curves are used to predict the performance of an experimental machine and can be used in the design of similar devices.

Distribution of Ground Fault Currents Along Transmission Lines -- An Improved Algorithm

The calculation of fault current distribution between ground wires and ground is important for the operation of modern power systems. A new method is presented based on an approach whereby the current distribution is solved through the computation of driving-point impedances. The method is applied to three phase systems with mutual couplings between conductors (phase and ground, respectively) included. Currents computed by this method and methods published in recent literature are compared and are found in good agreement. Results show that the method is more efficient in terms of CPU time and memory space.

Calculations of electrical properties of thin metal bridge foils using the boundary element method

This paper reports a study of the effects of geometry on the flow of current through a bridge foil. Using the Boundary Element Method, calculations of current distributions in bridges of various geometries are presented. A discussion is given of the effect of the bridge design on the current distribution and an improved design presented for situations which require current in the bridge to be as uniform as possible. The use of the BEM to estimate further the time evolution of the bridge as it heats up is discussed.

Applying the boundary element method to electrochemical calculations of primary current distribution

The computation of primary current distribution using the boundary element method has been analysed. A numerical example has been included. Values obtained numerically have been compared with those obtained experimentally. A fairly good accuracy has been observed. Some computational problems occurring when using the boundary element method for electrochemical problems have been discussed.

The singular integral problem in surfaces

The calculation of surface current distribution, given the geometry and source description, is a fundamental problem in antenna theory. In extending the harmonic analysis-integral equation method from one-dimensional to two-dimensional problems, a new way to deal with the singularity in the source-field relation is needed. Some results are given for surface current integrals which convert them to a convergent form.

Finite difference calculation of current distributions at polarized electrodes

AbstractThe changing geometry of electrodes undergoing electrodeposition or dissolution can be simulated by successive solutions of Laplace's equation with nonlinear boundary conditions. To overcome the instability in the finite‐difference calculation caused by nonlinear boundary conditions, a weighting algorithm to compute the new surface potential on successive iterations has been developed.

π-Electron ring currents and magnetic properties of porphyrin molecules in the MO LCAO SCF method

The coupled variant of double-parameter perturbation theory in the MO LCAO SCF method in the London approximation has been used for the calculation of π-electron current distributions in the molecules of porphin and its derivatives. The chemical shifts of1H-NMR have been computed on the basis of calculations of ring currents and charge distributions. It is shown that π-electron ring currents are responsible for the dominant contribution to the shielding of protons. The theoretical and experimental values of proton chemical shifts are in a good agreement. Chemical shifts of the13C and15N nuclei have also been estimated. Two aromaticity scales are proposed for the compounds under study based on the calculations of the π-electron contribution to the diamagnetic susceptibility and of π-electron currents, respectively.