Investigation of evolution strategy and optimization of induction heating model

An optimal design method using the finite element method and the evolution strategy (ES) is investigated. The evolution strategy is applied to the optimization of induction heating model. The position of auxiliary coil, frequency and ampere-turns are optimized so that the distribution of eddy current density on the surface of steel becomes uniform. It is shown that the selection of the appropriate parameter is important in the practical application of ES</p

Magneto-thermal-fluid analysis taking account of natural convection using semi-Lagrange coordinate system

A method for magneto-thermal-fluid analysis, taking account of natural convection using a semi-Lagrange coordinate system, is developed. The developed method is applied to a simple induction heating model in which the steel plate is heated due to an eddy current. It is shown that the result, considering the convection in air, is different from the result neglecting it</p

3-D topology optimization of single-pole-type head by using design sensitivity analysis

It is necessary to develop a write head having a large recording field and small stray field in adjacent tracks and adjacent bits in perpendicular magnetic recording systems. In this paper, a practical three-dimensional topology optimization technique combined with the edge-based finite-element method is proposed. A technique for obtaining a smooth topology is also shown. The optimization of single-pole-type head having a magnetic shield is performed by using the topology optimization technique so that the leakage flux in the adjacent bit can be reduced. A useful shape of the magnetic shield obtained by the proposed technique is illustrated.</p

Some useful techniques in analysis and design of electric machines

Some new techniques in the analysis and design of electric machines are discussed, namely: the time-periodic analysis of the magnetic field in nonoriented materials, taking into account hysteresis characteristics; 3-D transient analysis of capacitor-discharge impulse magnetizers; and a 3-D optimization method of electric machines considering nonlinearity and eddy currents. The usefulness of these techniques is shown by applying them to actual machines and comparisons with measurement results </p

"Dynamic Optimality of Yield Curve Strategies"

This paper formulates and analyzes a dynamic optimization problem of bond portfolios within Markovian Heath-Jarrow-Morton term structure models. In particular, we investigate optimal yield curve strategies analytically and numerically, and provide theoretical justification for a typical strategy which is recommended in practice for an expected change in the shape of the yield curve. In the numerical analysis, we utilize a new technique based on the asymptotic expansion approach in order to increase efficiency in computation.

Analysis of magnetic characteristics of three-phase reactor made of grain-oriented silicon steel

Flux and iron loss distributions of three-phase reactor are analyzed using the finite element method considering 2-D B-H curves and iron losses in arbitrary directions which are measured up to high flux density. It is shown that the total iron loss of reactor yoke does not change so much by the yoke dimension, although the local iron loss is increased when the width of yoke is decreased. The experimental verification of flux and iron loss distributions are also carried out </p

On the continuity of the magnetizing current density in 3-D magnetic field analysis with edge element

The effects of the continuity of the magnetizing current density on the convergence of the incomplete Cholesky conjugate gradient method and the accuracy of the calculated flux densities are investigated by imposing different continuity conditions for both nodal and edge elements. It is shown that the continuity condition should be imposed precisely in the case of edge elements </p

Improvements of single sheet testers for measurement of 2-D magnetic properties up to high flux density

Due to structural limitation, the currently proposed apparatus based on a single sheet tester (SST) cannot measure magnetic properties along arbitrary directions (so-called 2-D magnetic properties) of silicon steel at high flux densities. In this paper, significant improvements are carried out on magnetizing windings and auxiliary yokes of a double excitation type of SST. Furthermore, crosswise overlapped H-coils are introduced so that even an ordinary single-excitation type of SST can be applicable to the measurements of 2-D properties. It is demonstrated that 2-D magnetization property up to 1.9 T can be measured by using the newly developed SST's</p

Study on problems in detecting plural cracks by alternating flux leakage testing using 3D nonlinear eddy current analysis

The alternating magnetic flux leakage testing is used for the detection of cracks in a steel plate. A new technique of how to detect plural cracks, which are located at a very short distance from each other, using the parallel (x-) component of the leakage flux density is proposed. The behavior of leakage flux is examined using a three-dimensional edge-based hexahedral finite-element method. The effects of dimensions of search coils and cracks on the detection accuracy are illustrated. </p

Effective optimal design of 3-D magnetic device having complicated coil using edge element and Biot-Savart method

It is troublesome and time consuming to treat a coil of complicated shape with optimization methods using edge elements, because the current vector potential in the coil of changed shape (changed mesh) should be calculated at each iteration of the optimization. In this paper, an effective optimal design method using the Biot-Savart method (As method) and the evolution strategy is investigated. As it is not necessary to generate a mesh for the coil by using the As method, the mesh becomes simple and, moreover, it is not necessary to calculate the current vector potential in the changed coil at each iteration in order to give the current vector potential in the coil. The usefulness of the proposed method is illustrated by applying it to the optimal design of a deflection coil for a cathode-ray tube</p