Chang-Seop Koh

Utilizing genetic algorithms for the optimal design of electromagnetic devices

A new technique for the design optimization of electromagnetic devices that adopts the genetic algorithms (GAs) as the search method is presented. The method is applied to the optimization of the shape of a pole face in an electric motor. The electromagnetic analysis of the devices implemented is performed using 2D finite elements. The results show an excellent promise and potential of using GAs as an efficient technique for the optimal design problem. >

Design optimization of electrical machines using genetic algorithms

The application of genetic algorithms (GAs) to the design optimization of electromagnetic devices is presented in detail. The method is demonstrated on a magnetizer by optimizing its pole face to obtain the desired magnetic flux density distribution. The shape of the pole face is constructed from the control points by means of uniform nonrational b-splines. >

Multiresolution analysis for permeability reconstruction using wavelet

This paper presents a technique for solving the inverse problem using multiresolution analysis. For any real problem in modeling, the quality and quantity of available data are very limited. It is impossible to identify a distributed parameter with infinite or very large freedom. So, multiresolution analysis is proposed in order to obtain a good estimation of the permeability profile with a limited number of unknown parameters. The permeability variations are supposed to be localized spatially and spanned with wavelet bases. Some simulation results show the feasibility of this method.

Measurement of Magnetostriction Characteristics of Electrical Steel Sheet using Three-axial Strain Gauge and Vector Single Sheet Tester

Acoustic noise from a transformer, recently, has drawing more and more attentions. One of the main source of the noise is thought to be magnetostriction of the electrical steel sheets which compose transformer core. This paper deals with the magnetostriction of a highly grain-oriented electrical steel sheet measured by using a vector single sheet tester and a three-axial strain gauge. The results show that direction and axis ratio as well as the magnitude of the applied magnetic flux density contribute much to magnetostriction.

Study on Steady State Analysis of High Power Three-Phase Transformer using Time-Stepping Finite Element Method

This paper presents the fast steady state analysis using time-stepping finite element method for a high power three-phase transformer. The high power transformer spends huge computational cost of the time-stepping finite element method. It is because that the high power transformer requires a lot of time to reach steady state by its large inductance component. In order to reduce computational cost, in this paper, the adaptive time-step control algorithm combined with the embedded 2nd 4th singly diagonally implicit Runge-Kutta method and the analysis strategy using variation of the winding resistance are studied, and their numerical results are compared with those from the typical time-stepping finite element method.

Improved E&S Vector Hysteresis Model for the Precise Modeling of Vector Magnetic Properties of Electrical Steel Sheet

Recently, several vector hysteresis models such as vector Preisach, vector Jiles-Atherton and dynamic E&S model have been proposed to describe vector magnetic properties of electrical steel sheets. However, it is still difficult to find an adequate vector hysteresis model in finite element application for both the Non-oriented and Grain-oriented electrical steel sheets under alternating and rotating field conditions. In this paper, an improved E&S vector hysteresis model is suggested to describe the vector magnetic properties of both Non-oriented and Grain-oriented electrical steel sheets under various magnetic field conditions including alternating and rotating magnetic field conditions. The validity of the proposed model is tested through comparisons with the experimental results under various magnetic field conditions.