Trapped Field Profiles on Square GdBaCuO Bulks with Different Arrangement of Growth Sector Boundaries

Fujishiro, Hiroyuki; Arayashiki, Takahiro; Tamura, Tomohide; Naito, Tomoyuki; Teshima, Hidekazu; Morita, Mitsuru

doi:10.1143/jjap.51.093005

Cited by 5 publications

(5 citation statements)

References 20 publications

(24 reference statements)

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“…Inhomogeneities occur during the growth process of c-axis seeded, single grain (RE)BCO bulk superconductors, resulting in the formation of growth section regions (GSRs) and growth sector boundaries (GSBs), as shown in figure 2, with a higher J c for the GSBs in comparison with the GSRs [98,[108][109][110]. These play a significant role in the magnetization of these materials, particularly for the PFM technique, where they can affect the magnitude and shape of the trapped field and the maximum temperature rise, and different results are observed in comparison to FC and ZFC, particularly for lower applied fields [111]. J c can also vary as a function of position in a sample: generally a lower J c is found at the edge with respect to the centre and at the bottom with respect to the top [26,33,112].…”

Section: Inhomogeneities In (Re)bco Bulk Superconductorsmentioning

confidence: 99%

Modelling of bulk superconductor magnetization

Ainslie

Fujishiro

2015

Supercond. Sci. Technol.

182

166

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This paper presents a topical review of the current state of the art in modelling the magnetization of bulk superconductors, including both (RE)BCO (where RE = rare earth or Y) and MgB 2 materials. Such modelling is a powerful tool to understand the physical mechanisms of their magnetization, to assist in interpretation of experimental results, and to predict the performance of practical bulk superconductor-based devices, which is particularly important as many superconducting applications head towards the commercialisation stage of their development in the coming years. In addition to the analytical and numerical techniques currently used by researchers for modelling such materials, the commonly used practical techniques to magnetize bulk superconductors are summarised with a particular focus on pulsed field magnetization (PFM), which is promising as a compact, mobile and relatively inexpensive magnetizing technique. A number of numerical models developed to analyse the issues related to PFM and optimise the technique are described in detail, including understanding the dynamics of the magnetic flux penetration and the influence of material inhomogeneities, thermal properties, pulse duration, magnitude and shape, and the shape of the magnetization coil(s). The effect of externally applied magnetic fields in different configurations on the attenuation of the trapped field is also discussed. A number of novel and hybrid bulk superconductor structures are described, including improved thermal conductivity structures and ferromagnet-superconductor structures, which have been designed to overcome some of the issues related to bulk superconductors and their magnetization and enhance the intrinsic properties of bulk superconductors acting as trapped field magnets (TFMs). Finally, the use of hollow bulk cylinders/tubes for shielding is analysed.

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Section: Inhomogeneities In (Re)bco Bulk Superconductorsmentioning

confidence: 99%

Modelling of bulk superconductor magnetization

Ainslie

Fujishiro

2015

Supercond. Sci. Technol.

182

166

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“…4 (a) using the solenoid coil for the rectangular shaped bulk, the trapped field profile was distorted along the growth sector boundary and resulted in lower trapped field at the center of the bulk. The uniformity of the trapped filed profile is correlation with the magnetic flux dynamics [12]. For the solenoid coil, the magnetic flux concentrates on the rim and intrudes into the bulk from the periphery.…”

Section: B Numerical Simulationmentioning

confidence: 97%

“…We also reported the PFM results of a rectangular-shaped bulk using a solenoid coil, showing that an inhomogeneous J c distribution and the shape of the bulk leads to an asymmetric trapped field profile [12]. There has been no research reported in the case of a rectangular-shaped bulk magnetized using a split coil so far.…”

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confidence: 95%

Pulsed-Field Magnetizing Characteristics of Rectangular-Shaped Gd–Ba–Cu–O Bulk Using Split- and Solenoid-Type Coils

Takahashi

Ainslie

Fujishiro

et al. 2017

IEEE Trans. Appl. Supercond.

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We have investigated the trapped field characteristics of a rectangular-shaped Gd-Ba-Cu-O bulk (33 x 33 x 15 mm 3) magnetized by pulsed field magnetization (PFM) using split-and solenoid-type coils. A soft iron yoke was set below the bulk for the solenoid coil and two yokes are inserted in the bores of the split coil. The maximum trapped field, B Zmax , at the center of the bulk surface was 1.73 T at 40 K in the case of the solenoid coil, with a distorted profile. On the other hand, B Zmax was enhanced to 3.05 T at 40 K for the split coil with two yokes, for which a symmetric trapped field profile was observed. The behavior of the magnetic flux motion indicated two conditions for the enhancement of the trapped field: that the magnetic flux intrudes easily into the bulk even for lower applied fields and then saturates with minimal flux creep. We also have investigated the electromagnetic and thermal properties of the bulk during PFM using a numerical simulation, in which the magnetic flux tended to align along the z-axis due to the presence of the soft iron yoke. The use of the split coil with two yokes is effective in enhancing the trapped field for the rectangular-shaped bulks.  Index Terms-(RE) BaCuO bulk, pulsed field magnetization, numerical simulation, trapped field, soft iron yoke I. INTRODUCTION ULSED FIELD MAGNETIZATION (PFM) of (RE)BaCuO bulks (RE: rare earth element or Y) has been investigated intensively for practical applications as a substitute for fieldcooled magnetization (FCM) because PFM is an inexpensive and mobile experimental setup with no need for a superconducting magnet. However, the trapped field, B Z , by PFM is generally lower than that by FCM, where B Z values over 17 T have been achieved [1], because of the large temperature rise caused by the dynamical motion of the magnetic flux [2]. To enhance B Z by PFM, multi-pulse techniques using a solenoid coil are usually effective due to the reduction of temperature rise [3-6]. Using a new multipulse techniquethe so-called modified multi-pulse technique with stepwise cooling (MMPSC)we successfully achieved a highest trapped field of B Z = 5.20 T on a 45 mm Gd-Ba-Cu-O bulk disk at 30 K, which is a record-high value to date [7]. In addition, the use of new types of coils, such as a split coil

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“…However, during the magnetisation, the heat produced by PFM will hinder the realisation of the full trapped field and flux potential in CCs [40]. While zero field cooling and flux pumping have also been reported as general magnetisation methods for CCs [41][42][43][44][45][46], they have not been employed extensively in superconducting machines.…”

Section: Introductionmentioning

confidence: 99%

Magnetisation and demagnetisation of trapped field stacks in a superconducting machine for electric aircraft

Wang,

Zhang,

Hao

et al. 2023

Supercond. Sci. Technol.

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This research presents a comprehensive and innovative approach to investigating the magnetisation and cross-field demagnetisation behaviour of high-temperature superconducting (HTS) coated conductors (CCs) in practical superconducting machines. This study introduces several novel contributions, including the operation of the machine in propulsion energy conversion mode, the exploration of harmonics interaction in a real electric machine environment involving CCs, and the extraction of these harmonics as cross-field components. A 2D electromagnetic-thermal coupled numerical model employing the finite element method (FEM) has been developed and validated against experimental data to simulate a partially superconducting machine. Upon magnetisation, the HTS stacks effectively operate as trapped field magnets (TFMs), generating rotor fields for motor operation. With a peak magnetic flux density of 462 mT of the trapped field stacks (TFSs) in the air gap, the average values of the fundamental and fifth harmonics of the tangential magnetic flux density experienced by the TFSs were observed to be 25 mT and 1.75 mT, respectively. The research has thoroughly examined the impact of cross-field demagnetisation parameters including amplitude and frequency on the demagnetisation of TFSs. Furthermore, the study has also investigated the magnetisation losses occurring in various layers of HTS tapes, encompassing the HTS layer, magnetic substrate layer, and silver stabiliser at different amplitudes and frequencies. Two tape structures, namely a semi-homogenised model and a multi-layered model, have been analysed in terms of magnetisation loss. Additionally, insights into the shielding effect and skin effect at high frequencies were obtained, offering valuable information on the performance of HTS TFSs exposed to high frequency scenarios, especially in high-speed machines for electric aircraft. The research outcomes are anticipated to provide valuable knowledge for the design and optimisation of HTS rotors employing TFSs in superconducting machines, contributing to the advancement of superconducting machine technology.

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Trapped Field Profiles on Square GdBaCuO Bulks with Different Arrangement of Growth Sector Boundaries

Cited by 5 publications

References 20 publications

Modelling of bulk superconductor magnetization

Modelling of bulk superconductor magnetization

Pulsed-Field Magnetizing Characteristics of Rectangular-Shaped Gd–Ba–Cu–O Bulk Using Split- and Solenoid-Type Coils

Magnetisation and demagnetisation of trapped field stacks in a superconducting machine for electric aircraft

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