Search results

1 – 10 of 13
Article
Publication date: 7 August 2019

Ryoko Minehisa, Yasuhito Takahashi, Koji Fujiwara, Norio Takahashi, Masafumi Fujita, Kazuma Tsujikawa and Ken Nagakura

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…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Originality/value

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.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 38 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 19 July 2022

Yasuhito Takahashi, Koji Fujiwara and Takeshi Iwashita

This study aims to enhance the parallel performance of a parallel-in-space-and-time (PinST) finite-element method (FEM) using time step overlapping. The effectiveness of…

Abstract

Purpose

This study aims to enhance the parallel performance of a parallel-in-space-and-time (PinST) finite-element method (FEM) using time step overlapping. The effectiveness of the developed method is clarified in a magnet eddy-current loss analysis of a practical interior permanent magnet synchronous motor (IPMSM) using a massively parallel computing environment.

Design/methodology/approach

The developed PinST FEM is a combination of the domain decomposition method as a parallel-in-space (PinS) method and a parallel time-periodic explicit error correction (PTP-EEC) method, which is one of the parallel-in-time (PinT) approaches. The parallel performance of the PinST FEM is further improved by overlapping the time steps with different processes in the PTP-EEC method.

Findings

By applying the overlapping PTP-EEC method, the convergence of the transient solution to its steady state can be accelerated drastically. Consequently, the good parallel performance of the PinST FEM is achieved in magnetic field analyses of the practical IPMSM using a massively parallel computing environment, in which over 10,000 processes are used.

Originality/value

In this study, the PinST FEM based on time step overlapping is newly developed and its effectiveness is demonstrated in a massively parallel computing environment, in which using either the PinS or PinT method alone cannot achieve sufficient parallel performance. This finding implies a new direction of parallel computing approaches for electromagnetic field computation.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 25 July 2019

Yasuhito Takahashi, Koji Fujiwara, Takeshi Iwashita and Hiroshi Nakashima

This paper aims to propose a parallel-in-space-time finite-element method (FEM) for transient motor starting analyses. Although the domain decomposition method (DDM) is…

Abstract

Purpose

This paper aims to propose a parallel-in-space-time finite-element method (FEM) for transient motor starting analyses. Although the domain decomposition method (DDM) is suitable for solving large-scale problems and the parallel-in-time (PinT) integration method such as Parareal and time domain parallel FEM (TDPFEM) is effective for problems with a large number of time steps, their parallel performances get saturated as the number of processes increases. To overcome the difficulty, the hybrid approach in which both the DDM and PinT integration methods are used is investigated in a highly parallel computing environment.

Design/methodology/approach

First, the parallel performances of the DDM, Parareal and TDPFEM were compared because the scalability of these methods in highly parallel computation has not been deeply discussed. Then, the combination of the DDM and Parareal was investigated as a parallel-in-space-time FEM. The effectiveness of the developed method was demonstrated in transient starting analyses of induction motors.

Findings

The combination of Parareal with the DDM can improve the parallel performance in the case where the parallel performance of the DDM, TDPFEM or Parareal is saturated in highly parallel computation. In the case where the number of unknowns is large and the number of available processes is limited, the use of DDM is the most effective from the standpoint of computational cost.

Originality/value

This paper newly develops the parallel-in-space-time FEM and demonstrates its effectiveness in nonlinear magnetoquasistatic field analyses of electric machines. This finding is significantly important because a new direction of parallel computing techniques and great potential for its further development are clarified.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 38 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 24 July 2019

Naoya Watanabe, Yasuhito Takahashi and Koji Fujiwara

This paper aims to propose an effective modeling method of dynamic hysteresis properties for soft magnetic composite (SMC) core using an equivalent circuit representation…

81

Abstract

Purpose

This paper aims to propose an effective modeling method of dynamic hysteresis properties for soft magnetic composite (SMC) core using an equivalent circuit representation. Because the eddy currents flowing inside iron powder particles should be considered, it is well known that an accurate magnetic field analysis of the SMC core in a wide range of excitation frequency is not easy. To overcome this difficulty, a dynamic hysteresis modeling based on the standard Cauer circuit is investigated.

Design/methodology/approach

In the proposed method, the first inductance represents the static magnetic property of the SMC, and the latter part represents the dynamic effect because of the eddy currents. The values of the circuit elements were determined by an optimization method based on symmetric loops measured at several frequencies. To verify the validity of the proposed modeling method, finite-element analyses of a ring core inductor and an alternating current reactor were performed.

Findings

By comparing the simulated and measured magnetic properties, the necessity to consider magnetic hysteresis in the equivalent circuit model is clarified. Furthermore, the frequency-dependent inductances of practical reactors can be obtained from the finite-element analysis combined with the proposed method.

Originality/value

This paper demonstrates the significance of determining the circuit parameters in the equivalent circuit for dynamic hysteresis modeling based on the measured magnetic properties. The effectiveness of the proposed method is verified by comparing frequency-dependent inductances of two kinds of reactors between the simulation and measurement.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 38 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 1 February 1995

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…

Abstract

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.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 14 no. 2/3
Type: Research Article
ISSN: 0332-1649

Article
Publication date: 1 March 1992

Takayoshi NAKATA and Koji FUJIWARA

Benchmark problem 13 of the TEAM Workshop consists of steel plates around a coil (a nonlinear magnetostatic problem). Seventeen computer codes developed by twelve groups…

Abstract

Benchmark problem 13 of the TEAM Workshop consists of steel plates around a coil (a nonlinear magnetostatic problem). Seventeen computer codes developed by twelve groups are applied, and twenty‐five solutions are compared with each other and with experimental results. In addition to the numerical calculations, two theoretical presentations are given in order to explain discrepancies between the calculations and the experiment.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 11 no. 3
Type: Research Article
ISSN: 0332-1649

Article
Publication date: 1 March 1990

Koji FUJIWARA and Takayoshi NAKATA

Benchmark problem 7 of the TEAM workshop consists of an asymmetrical conductor with a hole. 17 computer codes are applied, and 25 solutions are compared with each other…

Abstract

Benchmark problem 7 of the TEAM workshop consists of an asymmetrical conductor with a hole. 17 computer codes are applied, and 25 solutions are compared with each other and with experimental results for eddy current densities and flux densities. Most of the codes were found to give satisfactory solutions.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 9 no. 3
Type: Research Article
ISSN: 0332-1649

Article
Publication date: 1 March 1990

Takayoshi NAKATA and Koji FUJIWARA

Benchmark problem 10 of the TEAM workshop consists of steel plates around a coil (non‐linear transient eddy current problem). Six computer codes are applied, and 6…

Abstract

Benchmark problem 10 of the TEAM workshop consists of steel plates around a coil (non‐linear transient eddy current problem). Six computer codes are applied, and 6 solutions are compared with each other and experimental results for eddy current densities as well as flux densities. Some codes were found to give oscillatory solutions.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 9 no. 3
Type: Research Article
ISSN: 0332-1649

Article
Publication date: 1 March 1992

Takayoshi NAKATA, Norio TAKAHASHI and Koji FUJIWARA

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…

Abstract

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.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 11 no. 3
Type: Research Article
ISSN: 0332-1649

Article
Publication date: 7 September 2015

Yoshifumi Okamoto, Akihisa Kameari, Koji Fujiwara, Tomonori Tsuburaya and Shuji Sato

– The purpose of this paper is the realization of Fast nonlinear finite element analysis (FEA).

Abstract

Purpose

The purpose of this paper is the realization of Fast nonlinear finite element analysis (FEA).

Design/methodology/approach

Nonlinear magnetic field analysis is achieved by using Newton-Raphson method implemented by relaxed convergence criterion of Krylov subspace method.

Findings

This paper mathematically analyzes the reason why nonlinear convergence can be achieved if the convergence criterion for linearized equation is relaxed.

Research limitations/implications

The proposed method is essential to reduce the elapsed time in nonlinear magnetic field analysis of quasi-stationary field.

Practical implications

The proposed method is able to be extended to not only static field but also time domain FEA strongly coupled with circuit equation.

Social implications

Because the speedup of performance evaluation of electrical machines would be achieved using proposed method, the work efficiency in manufacturing would be accelerated.

Originality/value

It can be seen that the nonlinear convergence can be achieved if the convergence criterion for linearized equation is relaxed. The verification of proposed method is demonstrated using practical nonlinear magnetic field problem.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

1 – 10 of 13