Masato Enokizono

Finite Element Analysis Of Transformer Model Core With Measured Reluctivity Tensor

This paper presents a new expression of the vector magnetic properties under alternating and rotating flux conditions. The expression is defined by an improved reluctivity tensor based on measured results. Moreover, the expression is more accurate than conventional expressions about the approximation of magnetic properties in arbitrary direction. Accordingly, our new expression is introduced into a finite element formulation, and applied to a simple anisotropic magnetic field problem. As a result, it is shown that our expression is applicable generally to anisotropic problems.

Two-dimensional magnetic properties of silicon steel sheet subjected to a rotating field

A study of the two-dimensional rotational magnetic properties of a steel sheet are discussed. These are measured making use of the vector relation between magnetic field strength H and magnetic flux density B. The results of this study lead to the following main conclusions: the permeability tensor becomes a full matrix under rotating flux; the off-diagonal terms of the permeability tensor are antisymmetric when the axis ratio of rotating flux is 1.0; and the mu /sub xy/ and mu /sub yx/ terms are due to rotational hysteresis. >

Improvement of T-joint part constructions in three-phase transformer cores by using direct loss analysis with E&S model

This paper presents the effects of the joint method in the T-joint of three-phase transformer cores on iron losses. The effects of joints on the decrease of core loss have been analyzed by using FEM with E&S model, considering the hysteresis of vector magnetic properties. As a result, we can improve the T-joint part constructions to reduce iron losses in the three-phase transformer cores.

Crack detection and recognition using an eddy current differential probe

This paper proposes a new eddy current differential sensor and a system for multi-frequency testing of conducting plates. Precise crack imaging was achieved by the use of spectrograms obtained from an eddy-current probe multi-frequency response and application of a neural network. Results of experiments with test specimens made of SUS304 showing very good sensitivity and spatial resolution are presented. The possibility of detection of an opposite side 20% crack was also confirmed.

Designing of suitable construction of high-frequency induction heating coil by using finite-element method

This paper describes the three-dimensional (3-D) modeling of an induction heating system. To realize the suitable construction of a high-frequency induction heating coil, numerical computations of eddy currents and heat conduction have been carried out by using the finite-element method (FEM) and also taking into account the dependence of material properties on temperature. For a high-frequency induction heating coil, which is normally applicable for heat treatment, the tubular solenoid design is the most appropriate due to its high coil efficiency. Coil efficiency is that part of energy delivered to the coil, which is transferred to the workpiece. Besides coil efficiency, the heating pattern and the production rate are also important. As the heating pattern reflects the coil geometry, optimal coil design is a prerequisite to attain the desired heating. Several modifications, such as spacing in between coil turns, the motion of the workpiece relative to the coil, and dimensional parameters, were carried out until optimal design was achieved.

Influence of Stress on Vector Magnetic Property Under Alternating Magnetic Flux Conditions

Electrical steel sheet in actual rotating machines is magnetized under alternating and rotating magnetic flux conditions. In addition, the magnetic properties of the electrical steel sheet are affected by mechanical stress strongly and are deteriorated due to the residual stress during the manufacturing process. Therefore, it is important to know the magnetic properties under various stress and magnetic flux conditions. In this paper, we investigated the effect of the mechanical stress on vector magnetic property under alternating magnetic flux conditions. Basing on the results, we can conclude that the vector magnetic property of the electrical steel sheet depends on the mechanical stress and the excitation direction. Therefore, it is important to consider the vector magnetic property with the mechanical stress in the design of the electrical machine.

Direct magnetic loss analysis by FEM considering vector magnetic properties

This paper deals with analysis by FEM for iron losses considering vector magnetic properties. We define the tensor magnetic reluctivity and calculate it from the data measured with two-dimensional measurement method. This numerical method is applied to the direct magnetic loss analysis. As a result, it is shown that the calculated results using our method are in a good agreement with measured ones.

Distribution of two-dimensional magnetic properties in three-phase induction motor model core

This paper presents the result for the local magnetic properties in a three-phase induction motor model core. The relationship between the magnetic field strength vector H and the magnetic flux density vector B, is obtained through measurements with a special sensor, which utilizes the H-coil method and the double needle method. As a result, the relationship between the H-vector and the B-vector is made clear, and it is shown that the local properties in an actual core are vectorial in nature.

Measurement of dynamic magnetostriction under rotating magnetic field

Rotational dynamic magnetostriction was measured as a function of rotating magnetic flux density on nonoriented and grain-oriented silicon steel sheets under various magnetization conditions. Rotational dynamic magnetostriction was measured by using a special strain gage which provides x- and y-direction output. Rotational magnetostriction is shown to be considerably larger than conventional alternating magnetostriction along the rolling direction because rotational dynamic magnetostriction is generated by the appearance and disappearance of 90 degrees magnetic domain walls under the rotating flux density. The results obtained explain why the cores of rotating machines and three-phase transformers show larger magnetostriction than that predicted by rolling direction measurements of single-strip sheets under alternating flux. >

Vector Magnetic Property and Magnetic Characteristic Analysis by Vector Magneto-Hysteretic E&S Model

In this paper, the vector magnetic property is explained first. And this paper also presents the magnetic characteristic analysis of the electrical machines by using the vector magnetic hysteretic E&S model. Furthermore, the dynamic E&S model, which can analyze the eddy current effect due to the distorted magnetic flux waveform, is presented. From this method, we can express the various kinds of magnetic properties directly, for example, vector hysteresis loops (Bx-Hx, By-Hy) magnetic power loss and the behavior of H and B vectors by using this model.