International Journal of Applied Electromagnetics and Mechanics - Volume 59, issue 1

Authors: Kamitani, Atsushi | Takayama, Teruou | Saitoh, Ayumu

Article Type: Research Article

Abstract: A high-performance method is developed for solving a linear system in the shielding current analysis of a high-temperature superconducting (HTS) film containing cracks. When the shielding current density is calculated in the HTS film, a linear system of special type has to be solved at each iteration cycle of the Newton method. If GMRES is applied to the solution of the linear system, its convergence property will be remarkably degraded with increasing crack size. In order to resolve this problem, other variables than corrections of the current vector potential are all eliminated from the linear system. Consequently, the residual history …of GMRES is hardly affected by a crack size so that its convergence property is improved remarkably. Show more

Keywords: Finite element method, high-temperature superconductor, linear-system solver, Newton method

DOI: 10.3233/JAE-171206

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 1, pp. 157-163, 2019

Authors: Kawaguchi, Hideki | Deri, Yi

Article Type: Research Article

Abstract: This paper presents a simulation of magnetization process of a high-T c superconductor (HTS), which is used for undulator magnets of X-ray Fee Electron Laser. The numerical analysis is carried out by a current vector potential method (T-method). In particular, it is discussed to use a power law macro-model for behavior of shielding current in the HTS. It is shown that the power low macro-model provides us better agreement with measurements for the final stage magnetic field distribution compared with conventional simulations based on a critical current macro-model.

Keywords: X-ray free electron laser (XFEL), undulator, high-T c superconductor (HTS), current vector potential method (T-method), critical state model, power law model

DOI: 10.3233/JAE-171051

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 1, pp. 165-171, 2019

Authors: Takayama, Teruou | Saitoh, Ayumu | Kamitani, Atsushi

Article Type: Research Article

Abstract: The acceleration performance of the pellet injection system by using the high-temperature superconducting (HTS) linear acceleration (SLA) to fuel the nuclear fusion reactor has been investigated numerically. To this end, the equivalent circuit model has been developed for analyzing the shielding current density in the HTS film. By using the model, the pellet injection system has been simulated. The results of the computations show that the acceleration performance depends on the parameter of the accelerating coil and the propulsion HTS film. Consequently, the pellet can be accelerated to about 2 km/s with the acceleration of 2 s. This acceleration speed of the …SLA is about 1.7 times as great as that of the conventional pellet injection system. Show more

Keywords: Accelerator magnets, circuit analysis, superconducting linear accelerators

DOI: 10.3233/JAE-171207

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 1, pp. 173-179, 2019

Authors: Miyao, Ryosuke | Igarashi, Hajime | Noguchi, So

Article Type: Research Article

Abstract: This paper presents the current and thermal phenomena of multi-stacked No-Insulation (NI) REBa2 Cu3 O7−x (REBCO, RE = Rare Earth) pancake coils during a local normal-state transition. An NI winding technique is expected to enhance the thermal stability of REBCO pancake coils, and it was verified in numerical simulations on a single pancake coil. However, a multi-stack of pancake coils are used to generate a high magnetic field in practical applications. When a normal-state transition occurs in one of multi-stacked pancake coils, it may deteriorate the stability of the other pancake coils. Therefore, we have developed a …numerical simulation code to clarify the current and thermal behaviors of multi-stacked NI REBCO pancake coils using a partial element equivalent circuit model and a thermal finite element method. Show more

Keywords: High temperature superconducting magnet, PEEC method, no-insulation REBCO pancake coil

DOI: 10.3233/JAE-171219

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 1, pp. 181-189, 2019

Authors: Murakami, Iwanori | Mori, Hayato | Shimizu, Makoto | Quan, Nguyen Manh | Ando, Yoshinori

Article Type: Research Article

Abstract: In this research, we studied the rigidity of superconducting magnetic bearings (SMBs) due to the difference in superconductor arrangement. I The SMB with one large superconductor fabricated in a previous study and the SMB with two small superconductors arranged separately in this study were compared. The rigidity in the axial direction, radial direction, and pitching direction of each bearing were measured. However, since the total volume of the superconductor used for the two SMBs is different, the rigidity per unit volume was compared. The results confirmed that the rigidity per unit volume in all directions is larger when a plurality …of small superconductors is used. In addition, this study verified the characteristics of each SMB by preparing a flywheel with two SMBs and rotating them. Show more

Keywords: Superconductor, magnetic bearing, flywheel, vibration, rigidity

DOI: 10.3233/JAE-171238

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 1, pp. 191-200, 2019

Authors: Vesa, Joonas | Karhula, Taru | Marjamäki, Antero | Panchal, Jay | Rasilo, Paavo

Article Type: Research Article

Abstract: In this paper we describe an algorithmic method to imitate geometries of soft magnetic composites. We use microscope images to determine some of the most important geometric characteristics of the material and optimize the algorithm such that the measured and simulated characteristics are in agreement. We compute the static magnetization curves using the geometries obtained from the images and the algorithm comparing the results. The aim is to produce realistic geometries to be used in homogenization schemes as well as to study the effects of magnetic contacts in general.

Keywords: Geometry generation, homogenization, magnetic composite

DOI: 10.3233/JAE-171032

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 1, pp. 201-208, 2019

Authors: Chevillard, Sylvain | Leblond, Juliette | Mavreas, Konstantinos

Article Type: Research Article

Abstract: We consider the inverse problem of recovering the position and moment of a magnetic dipole from sparse measurements of the field it generates, known on sections of three orthogonal cylinders enclosing it. This problem is motivated by recent measurements performed on Moon rocks, in view of determining their magnetic properties. The key ingredient of the presented method is the use of rational approximation techniques, together with properties of the poles of the approximants, in order to estimate the position of the dipole.

Keywords: Inverse problems, magnetic dipole, source estimation, rational approximation, Moon rocks

DOI: 10.3233/JAE-171033

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 1, pp. 209-215, 2019

Authors: Minowa, Naoki | Takahashi, Yasuhito | Fujiwara, Koji | Ahagon, Akira | Matsuo, Tetsuji

Article Type: Research Article

Abstract: In this paper, we investigate modeling methods of magnetic properties considering the hysteretic properties and the excess eddy-current loss. First, a simple method in which an excess magnetic field given by the Bertotti’s model is added to a surface magnetic field as a post-processing of the 1-D finite-element analysis is compared with a 1-D finite-element method directly considering an excess magnetic field. Additionally, homogenization methods of magnetic property of an electrical steel sheet with the Bertotti’s model are discussed from the standpoints of computational accuracy and costs.

Keywords: Magnetic hysteresis, excess eddy-current loss, homogenization

DOI: 10.3233/JAE-171008

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 1, pp. 217-226, 2019

Authors: Nair, Devi Geetha | Arkkio, Antero

Article Type: Research Article

Abstract: This paper aims to validate the loss components in the net electromagnetic losses in electrical machines through an inverse thermal modelling approach. The specific focus is on the stator core losses, which can be physically divided into yoke and tooth losses. A method to thermally map the three dimensional heat distribution in the 3-D stator core domain from noisy temperature measurements of the stator lamination surface using constrained least square minimization is presented. Preconditioned conjugate gradient method is also introduced as an alternative method and is shown to be a faster, and more accurate choice. The 3-D finite element model …was built for a 37 kW induction motor which served to generate the numerical forward thermal solution. Different measurement data from the yoke and tooth surface, with different levels of simulated noise were used to test the inverse loss approximation. Show more

Keywords: 3-D inverse thermal problem, conjugate gradient, least squares minimization, stator core loss

DOI: 10.3233/JAE-171041

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 1, pp. 227-233, 2019

Authors: Xie, Zheng | Shi, Pengpeng | Li, Qun | Chen, Zhenmao

Article Type: Research Article

Abstract: The influence of magnetic field on stress intensity factor at crack tips of a ferromagnetic material is studied in this paper. A method using a sequential coupling algorithm has been applied to solve this coupled problem explicitly. In order to realize the iterative calculation of the stress intensity factor, a semi-analytical solution of the magnetic field perturbation due to structural deformation near by the crack tips is derived at first. The Maxwell stress, the magnetostriction strain and the nonlinear mechanical property of the magnetic material are taken into consideration to cope with the magneto-mechanical coupling effects. Results of perturbed magnetic …field and distribution of magnetostriction strain at the crack tip are obtained and being evaluated quantitatively. Finally, the effects of the applied external magnetic field on stress intensity factor of a crack in a ferromagnetic material are discussed based on the numerical results. Show more

Keywords: Magnetoelastic, magnetostriction effect, stress intensity factor, ferromagnetic material

DOI: 10.3233/JAE-171156

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 59, no. 1, pp. 235-245, 2019