低温工学
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48 巻 , 4 号
選択された号の論文の11件中1~11を表示しています
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  • 石山 敦士, 植田 浩史, 王 旭東, 長屋 重夫, 渡部 智則
    48 巻 (2013) 4 号 p. 141-150
    公開日: 2013/05/13
    ジャーナル フリー
    Since high-temperature superconducting (HTS) conductors have a greater volumetric heat capacity at operating temperatures envisaged for practical applications, the possibility of quench caused by a mechanical disturbance such as friction due to wire movement is much lower than that for low-temperature superconducting (LTS) coils. In real applications such as superconducting magnetic energy storage (SMES) systems, however, electrical charging and discharging are repeated and the HTS conductor may deteriorate locally due to cyclic mechanical strain. We also have to consider the possibility of quench caused by a failure in the power supply, cooling system or similar problems. Therefore, a protection scheme assuming quench is also required for HTS coils. In this report, we describe a method of determining the appropriate stabilizer thickness of the YBCOcoated conductors from the perspective of the quench protection of the YBCO coil, which dumps the stored magnetic energy in the coils via external dump resistance. We have been developing a quench detection method for a cryocooler-cooled SMES coil wound with a kA-class laminated bundle conductor composed of an electrically insulated YBCO-coated conductor. Since the normal-zone propagation velocity is quite slow in HTS coils, the detection of a non-recovering normal zone using a voltage signal is quite difficult. Therefore, quench must be detected using some other method. We numerically show that quench in the coil can be detected by observing the transposition of current in the bundle conductor caused by local normal transition. Furthermore, we show the results of experiments on a small model coil wound with a four-YBCO-strand bundle conductor to examine the possibility of a quench detection method by observing the transposition of current in the bundle conductor. This work was mainly supported by the New Energy and Industrial Technology Development Organization (NEDO) as part of the technological development of yttrium-based superconducting power equipment.
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  • 柳澤 吉紀, 前田 秀明
    48 巻 (2013) 4 号 p. 151-156
    公開日: 2013/05/13
    ジャーナル フリー
    REBCO conductors were commercialized only recently in 2009 and therefore the magnet technology for REBCO conductors remains undeveloped. The major technological problems for REBCO coils encountered thus far are (a) degradation in the superconducting performance for mechanical reasons, (b) difficulty in protecting the magnet in the case of a super-normal transition of the REBCO coil and (c) the enormous effect of a screening-current-induced magnetic field. In this paper, the basic mechanism of degradation in the REBCO superconducting coil performance due to mechanical reasons is investigated through experiments and numerical simulations. Effective remedies for the degradation are also discussed.
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  • 柳澤 吉紀, 前田 秀明
    48 巻 (2013) 4 号 p. 157-164
    公開日: 2013/05/13
    ジャーナル フリー
    REBCO conductors were commercialized only recently in 2009 and therefore the magnet technology for REBCO conductors remains undeveloped. The major technological problems for REBCO coils encountered thus far are (a) degradation in the superconducting performance for mechanical reasons, (b) difficulty in protecting the magnet in the case of a super-normal transition of the REBCO coil and (c) the enormous effect of a screening-current-induced magnetic field. In this paper, the basic mechanism of premature thermal runaway in the REBCO superconductor is investigated through experiments and numerical simulations on small model coils. Effective remedies for suppressing the premature thermal runaway are discussed.
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  • 柳澤 吉紀, 前田 秀明
    48 巻 (2013) 4 号 p. 165-171
    公開日: 2013/05/13
    ジャーナル フリー
    REBCO conductors were commercialized only recently in 2009 and therefore the magnet technology for REBCO conductors remains undeveloped. The major technological problems for REBCO coils encountered thus far are (a) degradation in the superconducting performance for mechanical reasons, (b) difficulty in protecting the magnet in the case of a super-normal transition of the REBCO coil and (c) the enormous effect of a screening-current-induced magnetic field. In this paper, the basic mechanism of the screening-current-induced magnetic field and effective remedies for suppressing the screening field is investigated through experiments and numerical simulations.
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研究論文
  • 藤田 真司, 大保 雅載, 竹内 友章, 中村 直識, 鈴木 龍次, 飯島 康裕, 伊藤 雅彦, 齊藤 隆
    48 巻 (2013) 4 号 p. 172-177
    公開日: 2013/05/13
    ジャーナル フリー
    REBCO-coated conductors are expected to show high performance in superconducting applications because of their high mechanical strength and high current density in magnetic fields.We have developed an ion-beam-assisted-deposition (IBAD) and a pulsed-laser-deposition (PLD) technique to produce coated conductors with high performance. We have also produced some REBCO coil experimentally which includes a large-bore cryocooled 5 T magnet. It is important for coil applications to research various properties of coated conductors. In this report, we introduce some evaluation data that we have tested for our coated conductors. All samples for evaluation are based on long-length coated conductors. We carried out bending tests and axial tensile tests to evaluate mechanical properties, and stud-pull tests to evaluate delamination properties. Magnetic field, field angle and temperature dependence of critical current is measured for some coated conductors using a four-probe transport method. In addition, we evaluated longitudinal in-field critical current properties.
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  • 中村 武恒, 高村 豊, 雨宮 尚之, 中尾 公一, 和泉 輝郎
    48 巻 (2013) 4 号 p. 178-186
    公開日: 2013/05/13
    ジャーナル フリー
    In this paper, we studied the DC current transport properties of GdBCO-coated conductors, including the longitudinal distribution of critical current. Inhomogeneity of the local critical current was firstly measured by means of TapeStar™ at 77 K, and then characterized based on a statistical method. Current transport properties were also measured for different positions and/or distances of potential taps using a four-probe method. It was shown that the longitudinal inhomogeneity of the conductor was described by use of a simplified percolation depinning model that takes account of Gaussian distribution. We further distinguished the above-mentioned inhomogeneity between statistical distribution and random failure. Influence of the aforementioned statistically distributed current transport properties on the magnet performance was also elucidated for simple pancake coils. This information is important as it provides guidance for practical system design.
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  • 岩井 貞憲 , 宮崎 寛史, 戸坂 泰造, 田﨑 賢司, 石井 祐介
    48 巻 (2013) 4 号 p. 187-195
    公開日: 2013/05/13
    ジャーナル フリー
    In order to operate conduction-cooled HTS coils wound with REBCO-coated conductors stably without thermal runaway, the coil should not have any degraded area in the winding, and the flux flow characteristics should be calculated numerically. However, the delamination characteristics of short wire, which are considered to be a significant factor in degradation, are inconsistent with the results of thermal stress analysis. Therefore, we newly proposed a method for evaluation of the allowable design range of the coil without degradation. This method is characterized by use of the test results of small model coils differing in the ratio of outer diameter and inner diameter. Additionally, we measured the flux flow characteristics of a dry coil and performed numerical calculation for turn-to-turn. The calculated values were in good agreement with the measured ones.
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