Wyniki 1-4 spośród 4 dla zapytania: authorDesc:"Miloš BEKOVIĆ"

FEM-based development of measurement system for magnetic fluid characterization

Czytaj za darmo! »

In this article we describe the FEM based development of measurement system for determination of magnetic fluid heating effect when exposed to ac magnetic field. In the design phase several different geometries of excitation coils has been tested with the aim of achieving the homogeneity of the magnetic field, using FEM magnetic analysis. Furthermore thermal FEM analysis has been performed with intention of selecting suitable materials in the measuring system to achieve thermal stability. Streszczenie. W artykule opisany jest system pomiarowy bazujący na metodzie elementów skończonych (FEM) dla określenia efektu cieplnego w płynie magnetycznym wystawionym na pole magnetyczne AC. W fazie projektowej kilkanaście geometrii cewek wzbudzających zostało przetestowanych przy użyciu metody elementów skończonych w celu osiągnięcia jednorodności pola magnetycznego. Ponadto, analiza cieplna za pomocą FEM została przeprowadzona dla wyselekcjonowania materiałów pozwalających na osiągnięcie cieplnej stabilności. (Rozwój systemu pomiarowego wspomaganego metodą elementów skończonych dla analizy płynu magnetycznego). Keywords: Magnetic fluids, ac losses, heating effect, FEM analysis. Słowa kluczowe: płyny magnetyczne, straty AC, efekt grzania, analiza MES. Introduction Magnetic fluids are relatively new material, distinguished by some specific properties. Besides the obvious, that they are magnets in a liquid state offer many other properties that over the years had found many applications in the industrial applications as well as in biomedicine. In doing so, we can mention some applications such as targeted dosage of active substances by using magnetic fluids, magnetic resonance imaging contrast agents, and promising alternative cancer treatment with so-called hyperthermia [1]. This is a process in which the biocompatible magnetic fluid is introduced into a tumour and exposed to alternating magnetic field, where various acting losses mechanisms res[...]

Experimentally determinate flux linkage curve for dynamic simulation of universal motor

Czytaj za darmo! »

This paper is divided into two sections, where in first section different experimental methods for determining magnetically nonlinear characteristics of universal motor (UM) are described and evaluated. In second section obtained characteristic were used in dynamic simulation of UM and results of dynamic and steady state behaviour are compared with measured characteristics. Streszczenie. Artyku[...]

Determination of a crack's size on the basis of the nondestructive testing with eddy currents using metaheuristics DOI:10.15199/48.2019.05.07

Czytaj za darmo! »

Non-destructive testing is now used more and more often for the testing of materials [1-4]. One of nondestructive methods is testing using eddy currents. In this testing case we measure the magnetic flux density within the vicinity of the tested material which has changed because of the material damage [5-9]. Our problem is a conductive plate with a crack, and is limited to a crack of rectangular geometry having a constant depth. The crack’s position, crack’s length l, crack’s depth d and crack’s width w must be found. The first part of the research was searching for the crack’s position and length. These were found by consideration of the differences between the measured magnetic flux densities and the neighbouring measurement points. Second, the more complex part of the research was searching for the crack’s depth and width. We used differential evolution [10-13] for determining the crack’s depth and width. The Finite Element Method (FEM) [1, 3] model was used for the evaluation of cost function. Measurements Measurements were carried out for two test-cases. These were two plates, the first made of aluminium and the second of austenitic stainless steel, both of 30 mm thickness and dimensions of 330 x 285 mm. The cracks of both plates were the same and had lengths of 40 mm, depths of 10 mm, and widths of 0.5 mm. The cracks were in the middle of their respective plates. The used measuring system, together with the test plate, is shown in Fig. 1. Fig.1. Measuring system The excitation coil had an inner diameter of 36.8 mm, an outer diameter of 53 mm, and a height of 56 mm. It had 566 turns and was supplied with a sinusoidal current of 1A and a frequency of 500 Hz. An axial Hall-probe HS-AGB5-4805 was placed within a bore at the centre of the coil. The Hall probe measured the z component of the magnetic flux density. When, in the continuation of the paper, we talk about the magne[...]

Analysis of Electromagnetic Conditions Around the Conductor Clamp of a Covered Conductor DOI:10.15199/48.2019.05.08

Czytaj za darmo! »

Electric insulators are almost indispensable parts of each electric power network. Development of materials constantly brings new insulators with better insulation and mechanical properties. In the recent years, covered conductors that have many advantages and contribute to increased security of network operation often replace bare conductors. Covered conductors also have some disadvantages, such as inefficient performance of protection systems, difficult location of faults [1], insulation damage due to corona [2], [3], danger for people in the case of a fall of conductor to the ground, if the conductor remains energized, etc. The most frequent problems with covered conductors appear at the points of fixing the conductor to insulator [4], [5]. The reasons of these problems are usually inadequate combinations of properties of materials that compose conductor clamps. In most cases, they are composed of several materials with different dielectric constants with some metal parts between them. Inadequate geometrical forms of components of conductor clamps additionally worsen the situation. The paper presents the results of analyses of electromagnetic conditions in a »D-type« pin insulator, model »VS SER-b/20«, with metal conductor clamp and the use of covered conductor [6], [7]. The numerical computations of conditions inside the insulator and its surroundings were performed using Opera Vector Fields 3D program tool [9]. Computations of electrostatic and timeharmonic electromagnetic field were performed for different materials of components of conductor clamps having the same shape [8]. The influence of various materials is evident from the differences in electric field distribution in and around the insulator and eddy currents in the nearby metal parts. An accurate analysis of electric field calculation results also enabled identification of conditions that lead to damaging of conductor clamps and conducto[...]

 Strona 1