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In the laminated core of transformer, motor, etc. each electrical steel sheet is usually insulated in order to reduce the eddy current loss. Raw steel sheets without insulation are sometimes used in a small core of electrical machines and electronic equipments, because the cost of iron core can be reduced if cheap steel sheets without insulation are used in the core. The purpose of the paper is to show how the contact resistance between sheets of laminated core affects the interlaminar eddy current and to show the criterion for judgment of the necessity of insulation.

The eddy current losses of core made of SPCC (cold rolled steel sheets) of different widths with and without insulation under various conditions are analyzed by using the finite element method (FEM) considering the contact resistance. The equivalent circuit for such a laminated core without insulation is shown. The experimental investigation is also carried out.

A criterion for the judgment of insulation is examined. It is shown that the increase of eddy current is affected by the ratio (this corresponds to the criterion) of the resistance of steel and the contact resistance.

The paper clarifies a criterion for the necessity of insulation between sheets of laminated core. It is shown that a similar tendency to the measured value of eddy current loss can be obtained by utilizing the modeling method of laminated core.

This paper aims to propose a homogenization method considering magnetic anisotropy for a magnetic field analysis of a turbine generator. To verify the validity of the proposed method, the effects of magnetic anisotropy and a space factor on a no-load saturation curve and no-load iron loss of the turbine generator are discussed.

The proposed method was derived from the combination of the homogenization of microscopic fields in a laminated iron core with the modelling of two-dimensional magnetic properties based on free energy. To verify the validity, the proposed method was applied to a finite-element analysis of a simple ring core model. Finally, a no-load saturation curve and iron loss of the turbine generator was investigated by using the proposed method.

The computational accuracy of the homogenization method considering magnetic anisotropy is almost the same as that of the detailed modelling of the laminated structure in the magnetic field analysis of the laminated iron core. Furthermore, it is clarified that magnetic anisotropy does not have a large influence on the no-load saturation curve of the turbine generator because of the large air gap. On the other hand, the space factor affects the shape of the no-load saturation curve.

This paper verifies the validity of the homogenization method considering magnetic anisotropy method and elucidates the effects of magnetic anisotropy and a space factor on no-load characteristics of the turbine generator.

This article has been withdrawn as it was published elsewhere and accidentally duplicated. The original article can be seen here: 10.1108/eb010096. When citing the article, please cite: Takayoshi NAKATA, Norio TAKAHASHI, Koji FUJIWARA, (1992), “SUMMARY OF RESULTS FOR BENCHMARK PROBLEM 10 (STEEL PLATES AROUND A COIL)”, COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, Vol. 11 Iss: 3, pp. 335 - 344.

The purpose of the paper is to give a review of TEAM Problem 21, focus on its extended progress in engineering-oriented developments, and report the new benchmarking activity undertaken by the authors.

Testing electromagnetic analysis methods; verify computation models; detail the field behavior of typical magnetic structure; benefit to large-scale numerical modeling.

The calculated results of power loss and magnetic flux for all the member models agree well with the measured ones. The updated Problem 21 Family can now be used to model the saturation effect in the magnetic plate or the lamination by increasing the exciting currents. The new member model P21d-M allows further detailed examination of the electromagnetic behavior inside laminated sheets. The variation of both the iron loss and the magnetic flux with the excitation patterns and magnetic property data can be investigated inside the laminated sheets and the magnetic plate.

In order to model the possible saturation level of magnetic steel using Ar-V-Ar or T-Ω solvers, the exciting currents are increased from 10 to 50 A. In order to model the iron loss and magnetic flux densities inside the laminated sheets, a very simplified model, P21d-M of Problem 21 Family as shown in Figure 2, has been proposed.

Benchmark problem 10 of the TEAM workshop consists of steel plates around a coil (non‐linear transient eddy current problem). Seven computer codes are applied, and seven solutions are compared with each other and with experimental results.

The purpose of this paper is to examine the mechanism of the increase or decrease of eddy current loss of the segmented Nd‐Fe‐B sintered magnets without insulation, and the effects of parameters on such a phenomenon are discussed.

The measured contact resistance is used in the finite element analysis.

It is shown that the eddy current loss in a magnet shows the peak value when the number of segments are increased at 40 kHz, but this property is changed at low frequency (10 kHz). Its tendency is changed by the contact resistance and the permeance (surrounding iron core).

The reason of a curious property of eddy current loss of segmented magnets is clearly explained by examining the eddy current distribution at various contact resistances.

The purpose of this paper is to propose the speed-up of the fixed-point method by updating the reluctivity at each iteration (this is called a modified fixed-point method).

A modified fixed-point method, which updates the derivative of reluctivity at each iteration, is proposed. It is shown that the formulation of the fixed-point method using the derivative of reluctivity is almost the same as that of the Newton-Raphson method. The convergence characteristic of the newly proposed fixed-point method is compared with those of the Newton-Raphson method.

The modified fixed-point method has an advantage that the programming is easy and it has a similar convergence property to the Newton-Raphson method for an isotropic nonlinear problem.

This paper presents the formulation and convergence characteristic of the modified fixed-point method are almost the same as those of the Newton-Raphson method.

The purpose of the paper is to show that how a new magnetic circuit, which the paper could not imagined beforehand, may be obtained using a newly developed ON/OFF topology optimization method by applying it to the design of magnetic head and motor.

ON/OFF optimization technique combined with finite element method.

It is shown that 3-D topology optimization of SPT head, in which the recording head is increased and the leakage flux is decreased, is possible using the proposed method. The optimization of IPM motor with the minimum torque ripple and the maximum toque is also examined.

3-D ON/OFF optimization method applied to practical problems considering the nonlinearity and rotation of rotor, etc.

This paper describes the cogging torque of the permanent magnet synchronous (PM) motors due to the magnetic anisotropy of motor core. The cogging torque due to the magnetic anisotropy is calculated by the finite element method using two kinds of modeling methods: one is the 2D magnetization property method, and the other is the conventional method. As a result, the PM motors with parallel laminated core show different cogging torque waveform from the PM motors with the rotational laminated core due to the influence of the magnetic anisotropy. The amplitudes of the cogging torque are different depending on the modeling methods in the region of high flux density.