N. TAKAHASHI, T. NAKATA and H. MORISHIGE
Thirteen computer codes developed by eleven groups are applied to the benchmark problem 20 (3‐D static force problem) for the TEAM Workshop. The solutions are compared with each…
Abstract
Thirteen computer codes developed by eleven groups are applied to the benchmark problem 20 (3‐D static force problem) for the TEAM Workshop. The solutions are compared with each other and with experimental results.
T. NAKATA, N. TAKAHASHI and K. FUJIWARA
Seven computer codes developed by five groups are applied to the benchmark problem 13 of the TEAM Workshop which consists of steel plates around a coil (a nonlinear magnetostatic…
Abstract
Seven computer codes developed by five groups are applied to the benchmark problem 13 of the TEAM Workshop which consists of steel plates around a coil (a nonlinear magnetostatic problem). The solutions are compared with each other and with experimental results.
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 are…
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.
N. Takahashi, M. Natsumeda, M. Otoshi and K. Muramatsu
Factors affecting convergence of the simulated annealing method are investigated using an actual model. The convergence characteristics of various optimization methods are…
Abstract
Factors affecting convergence of the simulated annealing method are investigated using an actual model. The convergence characteristics of various optimization methods are examined using the contour line of objective function. Two kinds of combination methods with the simulated annealing method and the Rosenbrock’s method are investigated.
Details
Keywords
K. Muramatsu, T. Nakata, N. Takahashi, K. Fujiwara and H. Ukita
Recently, rare earth magnets with high coercive force such as Nd‐Fe‐B magnets have been developed. When the magnetic characteristic (M‐H curve) of such a strong magnet is…
Abstract
Recently, rare earth magnets with high coercive force such as Nd‐Fe‐B magnets have been developed. When the magnetic characteristic (M‐H curve) of such a strong magnet is measured, the conventional closed magnetic circuit method using an electromagnet cannot be applicable due to the magnetic saturation of the yoke. Therefore, the open magnetic circuit method has been proposed in which high magnetic fields are generated by using a superconducting or a pulsed magnet. In this method, the correction for demagnetizing field is required. The correction can be done using the demagnetizing factor which is a function of the shape and M‐H curve. The conventional studies take into account only the shape.
Zhiguang Cheng, Behzad Forghani, Zhenbin Du, Lanrong Liu, Yongjian Li, Xiaojun Zhao, Tao Liu, Linfeng Cai, Weiming Zhang, Meilin Lu, Yakun Tian and Yating Li
This paper aims to propose and establish a set of new benchmark models to investigate and confidently validate the modeling and prediction of total stray-field loss inside…
Abstract
Purpose
This paper aims to propose and establish a set of new benchmark models to investigate and confidently validate the modeling and prediction of total stray-field loss inside magnetic and non-magnetic components under harmonics-direct current (HDC) hybrid excitations. As a new member-set (P21e) of the testing electromagnetic analysis methods Problem 21 Family, the focus is on efficient analysis methods and accurate material property modeling under complex excitations.
Design/methodology/approach
This P21e-based benchmarking covers the design of new benchmark models with magnetic flux compensation, the establishment of a new benchmark measurement system with HDC hybrid excitation, the formulation of the testing program (such as defined Cases I–V) and the measurement and prediction of material properties under HDC hybrid excitations, to test electromagnetic analysis methods and finite element (FE) computation models and investigate the electromagnetic behavior of typical magnetic and electromagnetic shields in electrical equipment.
Findings
The updated Problem 21 Family (V.2021) can now be used to investigate and validate the total power loss and the different shielding performance of magnetic and electromagnetic shields under various HDC hybrid excitations, including the different spatial distributions of the same excitation parameters. The new member-set (P21e) with magnetic flux compensation can experimentally determine the total power loss inside the load-component, which helps to validate the numerical modeling and simulation with confidence. The additional iron loss inside the laminated sheets caused by the magnetic flux normal to the laminations must be correctly modeled and predicted during the design and analysis. It is also observed that the magnetic properties (B27R090) measured in the rolling and transverse directions with different direct current (DC) biasing magnetic field are quite different from each other.
Research limitations/implications
The future benchmarking target is to study the effects of stronger HDC hybrid excitations on the internal loss behavior and the microstructure of magnetic load components.
Originality/value
This paper proposes a new extension of Problem 21 Family (1993–2021) with the upgraded excitation, involving multi-harmonics and DC bias. The alternating current (AC) and DC excitation can be applied at the two sides of the model’s load-component to avoid the adverse impact on the AC and DC power supply and investigate the effect of different AC and DC hybrid patterns on the total loss inside the load-component. The overall effectiveness of numerical modeling and simulation is highlighted and achieved via combining the efficient electromagnetic analysis methods and solvers, the reliable material property modeling and prediction under complex excitations and the precise FE computation model using partition processing. The outcome of this project will be beneficial to large-scale and high-performance numerical modeling.
Details
Keywords
- New member-set
- TEAM Problem 21 Family
- Overall effectiveness
- Harmonics-DC hybrid excitation
- Magnetic flux compensation
- Load-component
- Shielding
- Stray-field loss
- Additional loss
- Material property under complex excitations
- Electromagnetic fields
- Numerical analysis
- Power losses
- Transient analysis
- Material modeling
- Computational electromagnetics
N. Takahashi, A. Muraoka, D. Miyagi, S. Fujino, K. Miyata and K. Ohashi
The paper examines the convergence characteristics of the “minimized residual method based on the MRTR (three‐term recurrence formula of CG‐type) method” for solving large linear…
Abstract
Purpose
The paper examines the convergence characteristics of the “minimized residual method based on the MRTR (three‐term recurrence formula of CG‐type) method” for solving large linear simultaneous equations.
Design/methodology/approach
The paper uses an example of magnetic field analysis of permanent magnet type of MRI taking account of the minor loop and eddy current.
Findings
It is shown that the preconditioned MRTR method can get a stable and quick convergence for such a relatively ill‐conditioned problem.
Originality/value
Illustrates that the convergence of the Incomplete Cholesky Conjugate Gradient method is one of the important issues in the practical 3D magnetic field analysis.
Details
Keywords
N. Takahashi, S. Nakazaki, H. Kato and J. Asaumi
The purpose of this paper is to provide an approach to the optimal design of open type magnetic circuit of permanent magnet having uniform field.
Abstract
Purpose
The purpose of this paper is to provide an approach to the optimal design of open type magnetic circuit of permanent magnet having uniform field.
Design/methodology/approach
The Biot‐Savart's law and evolution strategy are used for the design of permanent magnet configuration. The optimization is carried out by changing the objective function, dimension of target region, and target flux density.
Findings
The obtained uniformity is affected by the selection of objective function, dimension of target region, and target flux density. About 50 ppm uniformity of 0.08 T in the imaging area is obtained by changing the dimensions, dimension of target region, and target flux of 3D magnets and the amplitudes of magnetization and the directions of magnetization vectors.
Originality/value
This paper describes a new approach for obtaining the optimal shape of open type magnetic circuit which may be used when magnetic resonance imaging is carried out.
Details
Keywords
Katsumi Yamazaki, Yuki Yamato, Hisashi Mogi, Chikara Kaido, Akihito Nakahara, Kazuhiko Takahashi, Kazumasa Ide and Ken'ichi Hattori
The purpose of this paper is to investigate the distribution of in‐plane eddy currents in stator core packets of turbine generators, and to reveal the loss reduction effect by the…
Abstract
Purpose
The purpose of this paper is to investigate the distribution of in‐plane eddy currents in stator core packets of turbine generators, and to reveal the loss reduction effect by the slits in the stator teeth.
Design/methodology/approach
The in‐plane eddy currents are calculated by a 3D finite element method that considers lamination of electrical steel sheets. First, this method is applied to a simple model that simulates the stator core of the turbine generators. The calculated losses are compared with the measured losses in order to confirm the validity. Next, the same method is applied to a 250 MVA class turbine generator.
Findings
The validity of the calculation method is confirmed by the measurement of the simple model. By applying this method to the turbine generator, it is clarified that the considerable in‐plane eddy currents are generated not only at the end stator packets, but also at the top of the teeth of the interior packets due to the duct space. It is also clarified that the in‐plane eddy‐current loss decreases as nearly half by the slits of the stator teeth.
Originality/value
A reliable calculation method for the in‐plane eddy‐current loss in the turbine generators is developed. The results obtained by this method are valuable for the design of the generator from the viewpoint of heat conduction.