Igor Ticar

Computation of 3-D magnetostatic fields using a reduced scalar potential

Some improvements to the finite element computation of static magnetic fields in three dimensions using a reduced magnetic scalar potential are presented. Methods are described for obtaining an edge element representation of the rotational part of the magnetic field from a given source current distribution. When the current distribution is not known in advance, a boundary value problem is set up in terms of a current vector potential. An edge element representation of the solution can be directly used in the subsequent magnetostatic calculation. The magnetic field in a DC arc furnace is calculated by first determining the current distribution in terms of a current vector potential. A 3-D problem involving a permanent magnet as well as a coil is solved, and the magnetic field in some points is compared with measurement results. >

FEM analysis of eddy current losses in nonlinear laminated iron cores

A finite element method is presented to compute three-dimensional eddy current distributions in nonlinear laminated iron cores. In a first step, the core is assumed to have an anisotropic conductivity of zero value in the direction perpendicular to the laminations. In a second step, the eddy currents within the sheets are computed by solving the nonlinear field problem individually in each layer. The boundary conditions for these essentially two-dimensional analyses are taken from the three dimensional field distribution determined in the first step. Numerical examples prove the validity of the method.

Voltage-driven coils in finite-element formulations using a current vector and a magnetic scalar potential

Finite-element formulations using a current vector and a magnetic scalar potential are presented for low-frequency electromagnetic problems involving voltage driven coils. Windings both with and without skin effect are treated. The voltage constraint is directly incorporated into the finite-element equation system. Numerical examples are also presented.

An electromagnetic field analysis tool in education

In this paper, an electromagnetic field analysis tool for education in electrical engineering courses which is also accessible from the Web is described. The tool is based on the finite-element model (FEM). However, the main aim here is not to convey the methods of computational electromagnetics, but to give a deeper insight into electromagnetic phenomena. Three examples are shown, an eddy current problem in an axisymmetric ferrite core with air gap and the other two illustrate quasi-static electric transient behavior of the electric field considering imperfect dielectric media.

A FEM method for eddy current analysis in laminated media

Purpose – This paper aims at developing a computational technique to take account of the laminated nature of iron cores when computing their eddy current losses.Design/methodology/approach – A method is presented to compute three‐dimensional eddy current distributions in laminated media by means of the finite element method. In a first step, the laminated medium is assumed to have an anisotropic conductivity with zero (or very low) value in the direction normal to the laminations. In a second step, the eddy currents within the laminates are computed by solving the quasistatic electromagnetic field individually in each sheet. In these essentially two‐dimensional analyses, the boundary conditions are taken from the three‐dimensional field distribution determined in the first step.Findings – Comparisons with results obtained from a finite element model taking account of each laminate prove the validity of the method.Research limitations/implications – The method is presented for linear media only. Taking acc...

FEM simulation of thermistors including dielectric effects

Various applications make use of the extreme temperature-resistance characteristics of barium titanate ceramics. In ac circuits, the influence of dielectric phenomena also has to be considered. A quasi-static transient electric field simulation by the finite-element method coupled with thermal effects taking into account all nonlinear material properties is presented in the paper. The results are validated by measurements.

FEM-based design of an induction motor's part winding to reduce the starting current

The goal of this research is designing the part winding of an induction motor in order to reduce the surge currents when starting. The analyzed motor is to be built for special compressor applications; therefore, the standard star-delta windings are inappropriate. Until recently, winding schemes have been chosen using different analytical and experiential criteria. In this paper, a design process is presented based on transient numerical analysis with the rotation of the rotor also taken into consideration. The developed numerical model enables a study of the motors performance under arbitrary load conditions, and, thus, the entire torque characteristics of the motor can be predicted. Furthermore, the effects of eddy currents in the motor shaft material and their influence on the magnetic field and the motors performance have been analyzed. The numerical results have been verified by laboratory measurements

Determination of current and temperature distribution in overhead conductors by using electromagnetic-field analysis tools

This paper discusses the issue of skin-effect impact on a currents distribution. It presents an analytical approach for determining temperature distribution by using the Electromagnetic Field Analysis Tools two-dimensional (2-D) program (ELEFANT 2D) over the cross sections of tube-type conductors. Using this implemented model, the authors determine the conductors current density by taking into account the skin-effect impact on a multilayered bare conductor by the overhead power transmission lines of the ACSR 490/65 mm/sup 2/ type, and the optical cable of the optical ground wire (OPGW) type. An ELEFANT 2D is given an enabling determination of temperature distribution over the tube-type conductor cross section. The authors have developed, using this program, a computerized mathematical model for temperature determination by considering the skin effect in a multilayer ACSR 490/65 mm/sup 2/ conductor, and the optical cable of the OPGW type. The results show temperature distribution in individual layers of the ACSR 490/65 mm/sup 2/ conductor and the OPGW cable by adiabatic heating at different short-circuit currents.

Design of systems of covered overhead conductors by means of electric field calculation

Recently, in medium voltage overhead line systems, previously bare conductors are being replaced with conductors covered with a layer of insulation. Covered conductors enable an economical increase in operational reliability. At the current stage of development, there are several ways of replacing bare conductors with covered ones. Such a replacement also requires changing the accompanying line accessories, insulators, and line protection devices. The selection of the optimum combination of covered conductors and equipment has been done by means of electric field calculations. The optimization parameters have included the use of existing equipment to the maximum possible extent, new elements of equipment that have to be added, and the prevention of disturbances and failures in operation. Theoretical findings have been confirmed with laboratory tests on prototype combinations of covered conductors and the accompanying equipment.

Numerical analysis of permanent-magnet motor performance considering rotor movement

The paper presents a numerical analysis of a permanent-magnet brushless motor. The goal of the research was to estimate and reduce the torque ripple of a motor under research. The rotor movement was also taken into account in order to consider all the prime causes for torque ripple production. Therefore, two different types of analysis were carried out. The first approach was based on a transient analysis of a two-dimensional (2-D) planar finite-element model coupled to a voltage-fed electric circuit. The second approach was based on a static analysis of 2-D and three-dimensional models where stator current waveforms were calculated separately by a circuit model. Both analyses enable a comprehensive study of the electric machines performance under arbitrary load conditions considering the effects of the time-varying electrical variables as well as those due to rotor movement. An analysis was done of differently constructed varieties of motor model and different source voltage waveforms. Numerical results were verified by measurements in the laboratory.