Engineering Commons^™

Filtering Of The Magnetizing Current And Reproduction Of The Primary Voltage Of The Measuring Two-Wrinded Voltage Transformers, A G. Saidkhodjaev, V K. Vanin, M G. Popov, L A. Bainazarova

Technical science and innovation

The paper studies a qualitatively new way to reduce the measurement error of phase voltages in solving the problem of filtering the magnetization current and the reproduction of the primary voltage signals of two-winding measuring transformers. Errors of voltage measuring transformers in these transient and stationary processes are primarily due to the nonlinearity of the magnetization characteristics of the electrical steel cores and, in addition, the active resistance of the windings, the load and their inductances, and in some cases, and capacity. In fact, errors are methodical and in many practical applications limit the use of various transformers because of …

An Overview Of Methods And A New Three-Dimensional Fea And Analytical Hybrid Technique For Calculating Ac Winding Losses In Pm Machines, Narges Taran, Dan M. Ionel, Vandana Rallabandi, Greg Heins, Dean Patterson

Power and Energy Institute of Kentucky Faculty Publications

This article proposes a new hybrid analytical and numerical finite element (FE) based method for calculating ac eddy current losses in wire windings and demonstrates its applicability for axial flux permanent magnet electric machines. The method takes into account three-dimensional (3-D) field effects in order to achieve accurate results and yet greatly reduce computational efforts. The new 3-D FE-based method is advantageous as it employs minimum simplifications and considers the end turns in the eddy current path, the magnetic flux density variation along the effective length of coils, and the field fringing and leakage, which ultimately increases the accuracy of …

Design Optimization Of Coreless Axial-Flux Pm Machines With Litz Wire And Pcb Stator Windings, Murat G. Kesgin, Peng Han, Narges Taran, Damien Lawhorn, Donovin Lewis, Dan M. Ionel

Electrical and Computer Engineering Faculty Publications

Coreless axial-flux permanent-magnet (AFPM) machines may be attractive options for high-speed and high-power-density applications due to the elimination of core losses. In order to make full use of the advantages offered by these machines and avoid excessive eddy current losses in windings, advanced technologies for winding conductors need to be employed to suppress the eddy effect, such as the Litz wire and printed circuit board (PCB). In this paper, the best practices for designing Litz wire/PCB windings are discussed and a brief survey of state of the art PCB winding technology is provided. Three coreless AFPM machines are mainly considered. …

A Comparative Study Of Methods For Calculating Ac Winding Losses In Permanent Magnet Machines, Narges Taran, Vandana Rallabandi, Dan M. Ionel, Greg Heins, Dean Patterson

Power and Energy Institute of Kentucky Faculty Publications

In this study different methods of estimating the additional ac winding loss due to eddy currents at open-circuit are explored. A comparative study of 2D and 3D FEA, and hybrid numerical and analytical methods is performed in order to recommend feasible approaches to be employed. Axial flux permanent magnet (AFPM) machine case studies are included, namely a machine with open slots and a coreless configuration. These machine topologies are expected to present a substantial amount of ac winding loss, which would therefore need to be considered during optimal design. This study is one of the first ones to compare meticulous …

Computationally Efficient Strand Eddy Current Loss Calculation In Electric Machines, Alireza Fatemi, Dan M. Ionel, Nabeel Demerdash, Dave A. Staton, Rafal Wrobel, Yew Chuan Chong

Electrical and Computer Engineering Faculty Research and Publications

A fast finite element (FE) based method for the calculation of eddy current losses in the stator windings of randomly wound electric machines is presented in this paper. The method is particularly suitable for implementation in large-scale design optimization algorithms where a qualitative characterization of such losses at higher speeds is most beneficial for identification of the design solutions that exhibit the lowest overall losses including the ac losses in the stator windings. Unlike the common practice of assuming a constant slot fill factor s _f for all the design variations, the maximum s _f in the developed method is …

A Computationally Efficient Method For Calculation Of Strand Eddy Current Losses In Electric Machines, Alireza Fatemi, Dan M. Ionel, Nabeel Demerdash, Dave A. Staton, Rafal Wrobel, Yew Chuan Chong

Electrical and Computer Engineering Faculty Research and Publications

In this paper, a fast finite element (FE)-based method for the calculation of eddy current losses in the stator windings of randomly wound electric machines with a focus on fractional slot concentrated winding (FSCW) permanent magnet (PM) machines will be presented. The method is particularly suitable for implementation in large-scale design optimization algorithms where a qualitative characterization of such losses at higher speeds is most beneficial for identification of the design solutions which exhibit the lowest overall losses including the ac losses in the stator windings. Unlike the common practice of assuming a constant slot fill factor, sf, for all …

Effects Of Cold Work On Near-Surface Conductivity Profiles In Laser Shock Peened And Shot Peened Nickel-Base Superalloy, Tyler J. Lesthaeghe, Brian F. Larson, Ramya Chandrasekar, Anatoli M. Frishman, Chester C.H. Lo, Norio Nakagawa

Tyler J Lesthaeghe

This paper reports on a study of the effects of cold work induced by surface enhancement treatment on conductivity profiles in nickel-base superalloys, as part of the on-going efforts aimed at evaluating the feasibility of characterizing near-surface residual stress profiles in peened engine components using a swept frequency eddy current (SFEC) technique. The approach is based on the empirical piezoresistivity effect that correlates conductivity changes with residual stress, but recent studies have shown that conductivity changes induced by peening processes are also influenced by metallurgical factors such as cold work. In this study, conductivity deviation profiles were obtained by model-based …

Determination Of Electromagnetic Properties Of Steel For Prediction Of Stray Losses In Power Transformers, Leonardo Strac, Damir Zarko

Turkish Journal of Electrical Engineering and Computer Sciences

This paper introduces a method for determination of equivalent linear electromagnetic parameters (constant complex permeability and electrical conductivity) of nonlinear magnetic steel, which can be used in a time-harmonic finite-element simulation to yield the same losses in the volume of that material as the measured ones. The conductivity and the static hysteresis loop of the steel have been measured, from which complex permeability as a function of flux density has been extracted. The indirect measurement of losses in various samples of nonmagnetic and magnetic steel has been carried out using a physical model of a transformer core with a coil. …

Digital Computer Simulation Of Electromagnetic Field Problems As Applied To The Design Of Electrical Machinery, K. S. Demirchian, V. V. Dombrovski, V. L. Chechurin, M. Sarma

Sarma Mulukutla

The problem of electromagnetic field calculation in the end-zone of electrical machines is considered in this paper. A three-dimensional field requires using new methods of computing because the existing methods with the concept of vector potential demand unacceptable computer time. The new method consists of replacing the eddy magnetic field by the potential field of magnetic charges for the calculation of field, forces and associated inductances. Electrical currents of the rotor and stator windings are replaced by magnetic charges. it is possible to use just one scalar potential function for the computation instead of three components of the vector potential. …

Computing Models For The Magnetic Field Calculation Of Superconducting Electric Machines With The Help Of Scalar Magnetic Potential, V. L. Chechurin, M. Sarma

Sarma Mulukutla

The method of scalar magnetic potential using imaginary magnetic charges is employed effectively for the calculation of the electromagnetic fields in superconducting electric machines. The computing model consists of several single layers of magnetic charges. Finite-difference numerical techniques are utilized for the computation. The cylindrical coordinate system has been used for the calculation of the electromagnetic losses inside the electromagnetic shield of the rotor winding. The tangential and axial components of eddy currents have been taken into account. Linear magnetic charges replace rotor and stator currents; and surface magnetic charges replace the eddy currents inside the electromagnetic shield of the …

Scalar Potential Concept For Calculating The Steady Magnetic Fields And Eddy Currents, Kamo Demirchian, Vladimir Chechurin, Mulukutla Sarma

Sarma Mulukutla

The concept of scalar potential has been used for magnetic field calculation in the USSR during the last decade. It is based on treating the eddy component of the magnetic field separately and calculating the potential field with the help of the scalar potential by introducing imaginary magnetic charges. This method has been developed for digital calculations of magnetic fields in various electromagnetic devices, by solving linear and nonlinear partial-differential equations through mathematical simulation. This paper presents the mathematical formulation of the method. It is advantageous to use the scalar potential method for two-dimensional eddy-current calculations because of the possibility …

Current-Density Distribution In Solid-Rotor Induction Motor, Mulukutla S. Sarma

Sarma Mulukutla

The interaction between the eddy currents induced in the solid cylindrical rotor steel structure and the revolving field of the airgap produces the electrodynamic torque. The polyphase induction machine with solid-iron rotor offers advantages in ease of manufacture, in high torque per ampere at standstill, in withstanding high rotational stresses, and in operating in unusual environments. It is the purpose of this paper to present an approximate three-dimensional nonlinear numerical analysis of the solid-rotor induction motor for finding the three-dimensional current-density distribution in the solid rotor, in order to calculate the performance characteristics, based on finite-difference iterative techniques.

New Developments In The Computer-Aided Analysis Of Three-Dimensional Electromagnetic Field Problems As Applied To The Design Of Electrical Machinery, Mulukutla S. Sarma

Sarma Mulukutla

An accurate knowledge of the magnetic as well as other field distributions is of great importance in design optimization. In two dimensional problems with the current flow in only one direction, the magnetic field can be solved by computing a scalar potential or one component of the vector potential, The general formulation for three-dimensional solutions, including nonlinearities, is more complex and requires all three components of the vector potential as well as a scalar potential for the description of the fields. It is the purpose of this paper to present a general systematic, novel formulation at low frequencies feasible for …

On The Interaction Of An Eddy Current Coil With A Right-Angled Conductive Wedge, John R. Bowler, Theodoros Theodoulidis

John R. Bowler

A fundamental problem in eddy-current nondestructive evaluation is one of finding the quasi-static electromagnetic field of a cylindrical coil in the vicinity of the edge of a metal block. Although the field can be calculated numerically, an effective analytical approach can potentially provide a better understanding of the edge fields and form the basis of a procedure for solving a whole class of related edge problems including edge structures that contain corner cracks. One can represent the metal block as a conductive quarter space in an unbounded region. However, it has been found that the analysis is more straightforward if …

Reducing Eddy Currents In High Magnetic Field Environments, Russell Case

Electronic Theses and Dissertations

When an electrical conducting volume is placed into the bore of an MRI undergoing an image scan, time varying magnetic gradients induce eddy currents in this conducting material. These eddy currents in turn produce a mechanical torque on this volume. It is the goal of this thesis to produce a computer simulation of eddy currents produced by placing conducting materials inside an MRI bore. The first part of the thesis establishes the physics and principles behind an MRI system along with several applications. Next, this thesis presents an analysis of eddy current effects produced on a conductor placed into an …

Modeling Aspects Of Magnetic Actuators And Magnetic Suspension Systems, V. Dale Bloodgood Jr.

Mechanical & Aerospace Engineering Theses & Dissertations

This dissertation is a study of new modeling techniques developed for magnetic suspension systems. The techniques discussed are modifications of magnetic circuit theory and fundamental eddy current models. The techniques are compared against experimental test results and finite element data. The information gained from the experimental testing is used to provide insight into magnetic bearing design.

A small-gap modeling technique called extended circuit theory is developed that incorporates information about the system gained from finite element data, or experimental data, to be included in the analytic model. The variations between the classical magnetic circuit model and the finite element model …

Theory Of Thin-Skin Eddy-Current Interaction With Surface Cracks, Nicola Harfield, John R. Bowler

Nicola Bowler

Eddy-current non-destructive evaluation is commonly performed at relatively high frequencies at which the skin depths are significantly smaller than the dimensions of a typical crack. A thin-skin analysis of eddy currents is presented in which the electromagnetic fields on the crack faces are described in terms of a potential which obeys a two-dimensional Laplace equation. Solutions of this equation for defects in both magnetic and non-magnetic materials are determined by applying thin-skin boundary conditions at the crack perimeter. The impedance change of an eddy-current coil due to the defect is then calculated by numerical evaluation of one-dimensional integrals over the …

Low‐Frequency Perturbation Theory In Eddy‐Current Non‐Destructive Evaluation, Nicola Harfield, Y. Yoshida, John R. Bowler

Nicola Bowler

A method is presented by which series solutions for the impedance change in an eddy‐current test probe due to closed cracks in a non‐magnetic, conducting half‐space can be derived at low frequency. The series solution is applicable for flaws whose dimensions are much smaller than the electromagnetic skin‐depth. The problem is formulated using an approach in which the flaw is represented by an equivalent distribution of current dipoles. The electric field scattered by the flaw is then written as an integral, over the flaw, of the product of the dipole density distribution and an appropriate Green’s function. Terms in the …

Analysis Of Eddy‐Current Interaction With A Surface‐Breaking Crack, Nicola Harfield, John R. Bowler

Nicola Bowler

The change in electromagnetic impedance of a conductor due to the presence of a long, perpendicular surface‐breaking crack in a normally incident, uniform electric field is calculated in closed form in the high‐frequency limit. At high frequencies, where the skin depth is much smaller than the depth of the crack, the fields near the edge and corners of the crack are effectively decoupled. This means that the solution may be formulated as the sum of contributions from the corners, faces, and edge of the crack. Simple analytical expressions for the electric field are found and used to calculate the impedance …