JP4223744B2

JP4223744B2 - Critical current measurement method for high temperature superconducting wire

Info

Publication number: JP4223744B2
Application number: JP2002188511A
Authority: JP
Inventors: 健吾大倉; 和彦林
Original assignee: International Superconductivity Technology Center; Sumitomo Electric Industries Ltd
Current assignee: International Superconductivity Technology Center; Sumitomo Electric Industries Ltd
Priority date: 2002-06-27
Filing date: 2002-06-27
Publication date: 2009-02-12
Anticipated expiration: 2022-06-27
Also published as: JP2004028901A

Description

【０００１】
【発明の属する技術分野】
本発明は、超電導線材の臨界電流測定方法と、この方法の利用に好適な高温超電導線材の巻線構造に関するものである。特に、長尺の超電導線材をコイル状に巻き取った状態で臨界電流を測定できる方法に関するものである。
【０００２】
【従来の技術】
従来の高温超電導線材の臨界電流を評価する方法として、線材の端部またはその一部だけを測定する場合と、線材全長にわたり測定する場合の２種類がある。
【０００３】
後者の場合、通常、図7に示すように、コイル状に超電導線材を巻き取ったサプライリール210と、このサプライリール210から引き出された超電導線材220を巻き取る巻き取りリール230とを測定ラインに所定間隔に設置して測定を行う。測定に際して、コイル状に巻き取った線材の一部を液体窒素に冷却して超電導状態にし、線材220に通電するための電極と、電圧測定用の端子を超電導線材の表面に押し付けて測定器240をセットする。電極の一定区間で超電導線材を止め、その区間の線材に一定以上の電流を流して電圧を測定して臨界電流を求める。その後、電極、電圧端子を引き上げ、サプライリール210および巻き取りリール230を回転しながら、電極間の線材220を新たに移動した状態で電極、電圧端子を表面に押し付けて同様の測定が行われる。
【０００４】
臨界電流は、普通、電界強度（V/cm）により決定され、通常は10⁻ ⁶V/cmでの電流で決定される。例えば、電流を0から増やしてゆき、電圧が5μVになったときの電流値を読む。
【０００５】
【発明が解決しようとする課題】
しかし、上記の臨界電流の測定方法では次のような問題があった。
▲１▼電源からの電流供給を行わない永久電流モードのコイル用線材特性を評価する場合、測定精度が低く評価できない。
【０００６】
リールに巻き取られた状態の超電導線材全体について臨界電流を測ろうとすると、隣接する線材に流れる電流により磁場の影響があり測定は不可能である。そのため、線材をリールから引き出して測定を行うが、測定電圧は測定器に測定限界があり普通1μV程度であり、線材長さは普通臨界電流測定器の長さに限界があり例えば5m程度であり長くできない。このため、測定できる電界強度（電圧/線材長）には限界がある。永久電流モードでは普通10⁻ ¹⁰V/cmの微小な電界強度を測定する必要があるが、従来法では10⁻ ⁸V/cm程度が限界であった。
【０００７】
▲２▼電極を超電導線材に押し付けるために線材表面に傷が入り劣化する危険性がある。
【０００８】
▲３▼電極や電圧端子が線材に押し付けられる接触型であるため、半田付けに比べて測定感度が低いと言う問題もある。
【０００９】
従って、本発明の主目的は、リールに巻き取った状態の長尺線材でも高精度に臨界電流を測定できる超電導線材の臨界電流測定方法を提供することにある。
【００１０】
また、本発明の他の目的は、前記臨界電流測定方法の実施に最適な超電導線材の巻線構造を提供することにある。
【００１１】
【課題を解決するための手段】
本発明は、一対の超電導線材を接続し、この接続された超電導線材をコイル状に巻回して測定を行うことで上記の目的を達成する。
【００１２】
すなわち、本発明高温超電導線材の臨界電流測定方法は、2本の超電導線材を絶縁した状態で補強材に沿わせ、両超電導線材の一端側を電気的に接続し、この超電導線材をコイル状に巻回して、前記超電導線材の他端側から通電して電圧を測定することで臨界電流を測定することを特徴とする。
【００１３】
一対の超電導線材を一端側で電気的に接続し、この線材をコイル状に巻き取って他端側から電流を流すことで、各超電導線材の電流方向は互いに逆向きとなって磁場が打ち消されるため、磁場による電流値の低下がなく、ほとんど無磁場での低電界特性が得られる。そのため、従来法では測定できなかった永久電流モードのコイル用線材の評価も行うことができる。
【００１４】
また、コイル状に巻き取った状態で測定ができるため、測定器の長さからくる線材長さの制約を受けることがなく、長尺の超電導線材の臨界電流を測定することができる
【００１５】
ここで、超電導線材としては、Bi2223系超電導線材などの酸化物系高温超電導線材が好適である。一般には、テープ状の線材が利用される。
【００１６】
このような超電導線材を巻回するには、補強材を合わせて巻回する。補強材と共に巻回することで、超電導線材に緩みが生じて隙間が生じ、磁場が完全にキャンセルされず、漏れ磁場が生じて正確な臨界電流が測定できないといった不具合を解消できる。その他、超電導線材の巻線時に座屈が生じてコイルが劣化してしまう恐れを解消できる。このため、補強材は1kg以上の張力で巻回することが望ましい。
【００１７】
補強材を巻回する場合、電気的に接続された2本の超電導線材の一端側と共に、補強材も一括して巻き胴に固定しておけば良い。
【００１８】
補強材には、ステンレス、銅、銅合金、アルミニウム、アルミニウム合金、その他の金属材、ならびにFRP（Fiber Reinforced Plastic）などの高強度非金属材などが利用できる。補強材が導電性の場合、補強材と超電導線材との間に絶縁材を介在させることが好ましい。この絶縁材は補強材と独立したものでも良いし、予め一体に接合したものでも良い。補強材の形態は、超電導線材に合わせてテープ線材を用いることが好適である。
【００１９】
また、2本の超電導線材を一端側で電気的に接続する具体的手段としては、半田付けが好適である。半田付けにより確実に両線材を接続することができる。
【００２０】
この半田付けを行う場合、2本の超電導線材を直線状で半田付けしてから巻回すると、通常は半田の曲げ性が悪く固いために巻線するときに超電導線材が折れて劣化する。そこで、各超電導線材に部分的に形成された半田メッキ同士を重ね合わせ、両超電導線材を巻き胴に巻き取る際に半田メッキを溶融・接合させることにより電気的接続箇所を形成することが望ましい。2本の超電導線材を半田付けしてから巻き取るのではなく、巻き取られた状態で半田付けの接合を行うことで、超電導線材の折れを抑制する。
【００２１】
例えば、2本の超電導テープ、絶縁テープ、補強テープを用いる場合、次のように両超電導テープの半田付けを行えばよい。まず、下層超電導テープ、上層超電導テープ、補強テープの順に積層し、この積層テープの一端を巻き胴に固定する。積層テープを少し巻いた後、巻かれた下層超電導テープの表面に半田メッキを行い、上層超電導テープの裏面に直線状で半田メッキを行う。次に、上層超電導テープの半田メッキを半田ごてなどで溶融し、その状態で上層超電導テープを巻回して、下層超電導テープの半田メッキ上に重ねることにより、両超電導テープを半田付けする。その後、半田付けされていない上下層の超電導テープの間に絶縁テープを挿入し、補強テープと一括して巻き胴に巻回する。
【００２２】
超電導線材の他端側には超電導線材に電流を流すための端末電極を設けることが好ましい。この端末電極はCuやAlなどの導電材料を各超電導線材の巻き終り側端部に半田付けすることで形成すればよい。
【００２３】
特に、両超電導線材が電気的に接続された一端側をコイルの巻き始め側とし、他端側を巻き終り側とすることで、端末電極を巻き終り側とし、測定器の線材への接続を容易に行うことができる。
【００２４】
また、超電導線材の少なくとも他端側には、電圧測定用の端子を形成することが好ましい。この端子は、超電導線材を半田付けしやすいものであれば種々の材質が利用できる。例えば、Al、Cu、Agなどが好適である。中でも超電導線材の安定化材に用いられるAgまたはAg合金が望ましい。端子の形状は薄膜が好適である。各超電導線材に接した状態で薄膜端子を設ければよい。
【００２５】
超電導線材の一端側にも同様の電圧測定用端子を設けることで、2本の超電導線材のうち、一方の超電導線材の一端側と他端側の電圧を測定して臨界電流を求めることができる。超電導線材の他端側にのみ電圧測定用端子を設け、これら端子間の電圧を測定すると、超電導線材の一端側における接続箇所（半田付けなど）の抵抗も含めて2本の超電導線材全長の電圧を計測することになる。超電導線材の一端側にも電圧測定用端子を設けておけば、他端側の端子との間の電圧を測定することで、半田付けなどの接続箇所を含むことなく、一方の超電導線材における一端側と他端側の電圧を測定することができる。
【００２６】
【発明の実施の形態】
以下、本発明の実施の形態を説明する。
図１は本発明測定方法に用いる超電導線材を巻き取ったリールの概略模式図である。
【００２７】
このリール10は、円筒状の巻き胴11の両側に円盤状のつば12を有するステンレス製のもので、その巻き胴11には絶縁テープを介して一体化した一対の超電導テープ線材20が巻回されている。
【００２８】
超電導テープ線材20は、安定化材となる銀シース中に複数のBi2223系の超電導フィラメントが埋設されたテープ状線材である。ここでは、長さ100m、幅4.1mm、厚さ0.24mmのテープ状線材を用いた。
【００２９】
図２に超電導テープ線材20の巻き始め側の拡大断面図を示す。この超電導線材を2枚用意し、厚さ70μmのポリイミドテープ（商品名：カプトンテープ）などの絶縁テープ30を介して両超電導テープ線材21,22を沿わせる。さらに、一方の超電導テープ線材上に補強テープ40を沿わせる。この補強テープには、両面にカプトンテープ41が貼り合わされた厚さ0.1mmのステンレステープ42を用いた。補強テープ40は、超電導テープ線材の押さえ巻きが行えるものであれば、特に材質は限定されない。
【００３０】
ここで、両超電導テープ線材21,22の一端から若干ずれた位置を半田付けで接合し、電気的に接続しておく。この半田付けは、両超電導線材21,22の所要箇所に半田メッキを施しておき、巻き胴11に巻き取った状態で溶融接合する。また、この接合箇所50から両超電導線材の他端側に若干ずれた位置に電圧測定用の薄膜端子61,62を設ける。本例では、一方の超電導テープ線材21と絶縁テープ30の間および他方の超電導テープ線材22と補強テープ40の間に、それぞれ厚さ20μmの銀箔を部分的に介在させて半田付けにて固定することで薄膜端子61,62とした。
【００３１】
このような超電導線材の一端側、つまり半田付けで接合された側を巻き始め端としてリールの巻き胴11に巻回し、シングルパンケーキコイルを形成する。巻き胴11には、巻き始め端の固定部13が形成されている（図１）。ここでは、超電導線材の半田付け箇所よりも一端側をGFRP（Glass Fiber Reinforced Plastic）の固定治具で巻き胴11との間に挟み込み、ボルトで固定治具を留めることにより固定部を構成した。
【００３２】
一方、巻き終わり側となる超電導線材の他端側には、電流を流すための端末電極と、電圧測定用の薄膜端子を形成する。図３に超電導テープ線材の巻き終わり側の断面図を示す。端末電極70は、各超電導線材の他端部に銅片を半田付けして構成した。この端末電極を通して超電導テープ線材21,22に所定の電流を流す。薄膜端子80は、前述した薄膜端子61,62と同様の構成で、端末電極70よりも超電導線材の巻き始め側にずれた位置に形成される。
【００３３】
このような超電導線材の臨界電流を測定する場合、コイルを液体窒素で冷却して超電導状態にした後、端末電極間で巻き始めの半田付けした接合箇所を経由して電流を流し、超電導テープの発生電圧を測定することで行う。その際、2通りの測定方法が利用できる。
【００３４】
第1の方法は、図4に示すように、端末電極に測定器90を接続し、一定の電流を流して巻き終わり側の薄膜端子間の電圧を測定して臨界電流を計測する方法である。図4では、説明の便宜上、超電導テープ線材は巻き取った状態ではなく、広げた状態にして示している。この方法では、半田付けした接合箇所を介して一対の超電導テープ線材全長にわたっての電圧を測定することになる。その際、一方の超電導テープ線材21を流れる電流と他方の超電導テープ線材22を流れる電流とは、互いに逆方向に流れるため、発生する磁場を打ち消すことにより、巻き取った状態でも磁場の影響により電流が低下することなく臨界電流を測定することができる。
【００３５】
第２の方法は、図５に示すように、端末電極に電源１００を接続して超電導線材に一定の電流を流し、一端側（巻き始め）の薄膜端子と他端側（巻き終わり）の薄膜端子との間に測定器９０を接続して、両薄膜端子間の電圧を測定する方法である。図５では、説明の便宜上、超電導テープ線材は巻き取った状態ではなく、広げた状態にして示している。この方法では、２本の超電導テープ線材のうち、一方の超電導テープ線材２１の全長にわたって電圧を測定することになる。この方法では、電圧を測定する薄膜端子間に半田付けした接合箇所を含まないため、この接合箇所の抵抗の影響を排してより正確な臨界電流の測定を行うことができる。一方の超電導テープ線材の臨界電流測定を行った後、他方の超電導テープ線材２２の臨界電流も同様にして測定する。この第２の方法でも、一方の超電導テープ線材２１と他方の超電導テープ線材２２とでは電流の方向が逆であり、発生する磁場を打ち消すことにより、巻き取った状態でも磁場の影響により電流が低下することなく臨界電流を測定することができる。
【００３６】
上記の第２の方法により、一方の超電導テープ線材21の全長にわたって電圧を測定し、その電圧値を線材の長さで除した値から電界強度を求めた。電流値と電界強度との関係を図6のグラフに示す。このグラフに示すように、10⁻ ¹⁰V/cmの高精度で線材の電界強度を測定できることがわかる。従って、永久電流モードのコイル用線材の性能評価を行うことができる。また、超電導テープ線材の端部に端末電極や薄膜端子を設けるため、超電導テープ線材の中間部に電極や端子を押し付ける必要がなく、線材の劣化も抑制できる。
【００３７】
【発明の効果】
以上説明したように、本発明方法によれば、2本の超電導線材の一端側を電気的に接続して測定を行うことで、各超電導線材の電流方向は逆向きとなって磁場が打ち消されるため、磁場による超電導電流の低下がなく、ほとんど無磁場での低電界特性を得ることができる。そのため、従来法では測定できない永久電流モードのコイル用線材の評価を行うことができる。
【００３８】
また、コイル状に巻き取った状態で測定が行えるため、長尺の超電導線材の臨界電流測定が可能となり、ゼロ磁界で低電界強度まで測定することができる。
【図面の簡単な説明】
【図１】本発明測定方法に用いる超電導線材を巻き取ったリールの概略模式図である。
【図２】超電導テープ線材の巻き始め側を示す拡大断面図である。
【図３】超電導テープ線材の巻き終り側を示す拡大断面図である。
【図４】本発明測定方法の第１の基本原理を示す説明図である。
【図５】本発明測定方法の第2の基本原理を示す説明図である。
【図６】電流と電界強度との関係を示すグラフである。
【図７】従来の測定方法の説明図である。
【符号の説明】
10 リール
11 巻き胴
12 つば
13 固定部
20、21、22 超電導テープ線材
30 絶縁テープ
40 補強テープ
41 カプトンテープ
42 ステンレステープ
50 接合箇所
61、62 薄膜端子
70 端末電極
80 薄膜端子
90 測定器
100 電源
210 サプライリール
220 超電導線材
230 巻き取りリール
240 測定器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for measuring a critical current of a superconducting wire and a winding structure of a high-temperature superconducting wire suitable for use of this method. In particular, the present invention relates to a method capable of measuring a critical current in a state where a long superconducting wire is wound in a coil shape.
[0002]
[Prior art]
There are two types of methods for evaluating the critical current of a conventional high-temperature superconducting wire: measuring the end of the wire or only a part thereof, and measuring the entire length of the wire.
[0003]
In the latter case, normally, as shown in FIG. 7, a supply reel 210 in which a superconducting wire is wound in a coil shape and a take-up reel 230 in which the superconducting wire 220 drawn out from the supply reel 210 is wound are used as a measurement line. Install at predetermined intervals and perform measurement. At the time of measurement, a part of the wire wound in a coil shape is cooled to liquid nitrogen to be in a superconducting state, and an electrode for energizing the wire 220 and a terminal for voltage measurement are pressed against the surface of the superconducting wire 240 Set. The superconducting wire is stopped in a certain section of the electrode, a current of a certain level or more is passed through the wire in that section, the voltage is measured, and the critical current is obtained. Thereafter, the electrode and the voltage terminal are pulled up, and while rotating the supply reel 210 and the take-up reel 230, the electrode and the voltage terminal are pressed against the surface in a state where the wire 220 between the electrodes is newly moved, and the same measurement is performed.
[0004]
The critical current is usually determined by the field intensity (V / cm), typically 10 ^- is determined by the current at ⁶ V / cm. For example, increase the current from 0 and read the current value when the voltage reaches 5μV.
[0005]
[Problems to be solved by the invention]
However, the above critical current measurement method has the following problems.
(1) When evaluating the coil wire characteristics in the permanent current mode in which no current is supplied from the power source, the measurement accuracy cannot be evaluated low.
[0006]
When the critical current is measured for the whole superconducting wire wound on the reel, the measurement is impossible due to the influence of the magnetic field due to the current flowing in the adjacent wire. Therefore, the wire rod is pulled out from the reel and the measurement is performed, but the measurement voltage has a measurement limit in the measuring instrument and is usually about 1μV, and the wire length is usually in the limit of the critical current measuring instrument and is about 5m, for example. Can't be long. For this reason, there is a limit to the electric field strength (voltage / wire length) that can be measured. The persistent current mode usually 10 ^- it is necessary to measure the small field strength of ¹⁰ V / cm, but the conventional methods 10 ^- about ⁸ V / cm was limited.
[0007]
(2) Since the electrode is pressed against the superconducting wire, there is a risk that the surface of the wire will be scratched and deteriorated.
[0008]
{Circle around (3)} Since the contact type is such that the electrodes and voltage terminals are pressed against the wire, there is also a problem that the measurement sensitivity is lower than that of soldering.
[0009]
Accordingly, a main object of the present invention is to provide a method for measuring the critical current of a superconducting wire capable of measuring the critical current with high accuracy even with a long wire wound on a reel.
[0010]
Another object of the present invention is to provide a winding structure of a superconducting wire that is optimal for the implementation of the critical current measuring method.
[0011]
[Means for Solving the Problems]
The present invention achieves the above-mentioned object by connecting a pair of superconducting wires and measuring the connected superconducting wires in a coil shape.
[0012]
That is, the critical current measuring method for the high-temperature superconducting wire of the present invention is such that the two superconducting wires are insulated and along the reinforcing material, one end side of both superconducting wires is electrically connected, and the superconducting wire is coiled. The critical current is measured by winding and energizing from the other end of the superconducting wire to measure the voltage.
[0013]
A pair of superconducting wires are electrically connected at one end side, and the wires are wound in a coil shape and a current is passed from the other end side, so that the current directions of the respective superconducting wires are opposite to each other and the magnetic field is canceled. Therefore, there is no decrease in the current value due to the magnetic field, and low electric field characteristics with almost no magnetic field can be obtained. Therefore, it is possible to evaluate a coil material for a coil in a permanent current mode that cannot be measured by the conventional method.
[0014]
Further, since the measurement can be performed in a coiled state, the critical current of the long superconducting wire can be measured without being restricted by the length of the wire coming from the length of the measuring instrument.
Here, as the superconducting wire, an oxide-based high-temperature superconducting wire such as a Bi2223 superconducting wire is suitable. In general, a tape-shaped wire is used.
[0016]
In order to wind such a superconducting wire, the reinforcing material is wound together. By winding together with the reinforcing material, the superconducting wire is loosened and a gap is formed, the magnetic field is not completely canceled, and a leakage magnetic field is generated and an accurate critical current cannot be measured. In addition, it is possible to eliminate the risk that the coil will deteriorate due to buckling during winding of the superconducting wire. For this reason, it is desirable to wind the reinforcing material with a tension of 1 kg or more.
[0017]
When the reinforcing material is wound, the reinforcing material may be fixed to the winding drum all together with one end side of the two electrically connected superconducting wires.
[0018]
As the reinforcing material, stainless steel, copper, copper alloy, aluminum, aluminum alloy, other metal materials, and high-strength non-metallic materials such as FRP (Fiber Reinforced Plastic) can be used. When the reinforcing material is conductive, it is preferable to interpose an insulating material between the reinforcing material and the superconducting wire. This insulating material may be independent from the reinforcing material, or may be integrally joined in advance. As for the form of the reinforcing material, it is preferable to use a tape wire according to the superconducting wire.
[0019]
Also, soldering is suitable as a specific means for electrically connecting the two superconducting wires on one end side. Both wires can be securely connected by soldering.
[0020]
When performing this soldering, if the two superconducting wires are soldered in a straight line and then wound, the superconducting wires are broken and deteriorated when they are wound because the solder bend is usually poor and hard. Therefore, it is desirable to form an electrical connection portion by superimposing solder platings partially formed on each superconducting wire and melting and joining the solder plating when winding both superconducting wires on a winding drum. Rather than winding the two superconducting wires after soldering, the soldering is performed in a wound state, thereby suppressing the breakage of the superconducting wires.
[0021]
For example, when two superconducting tapes, insulating tapes, and reinforcing tapes are used, both superconducting tapes may be soldered as follows. First, a lower layer superconducting tape, an upper layer superconducting tape, and a reinforcing tape are laminated in this order, and one end of the laminated tape is fixed to a winding drum. After slightly winding the laminated tape, solder plating is performed on the surface of the wound lower superconducting tape, and solder plating is performed linearly on the back surface of the upper superconducting tape. Next, both the superconducting tapes are soldered by melting the solder plating of the upper superconducting tape with a soldering iron or the like, winding the upper superconducting tape in this state, and superposing it on the solder plating of the lower superconducting tape. Thereafter, an insulating tape is inserted between upper and lower superconducting tapes that are not soldered, and wound around the winding drum together with the reinforcing tape.
[0022]
It is preferable to provide a terminal electrode for flowing a current through the superconducting wire on the other end side of the superconducting wire. The terminal electrode may be formed by soldering a conductive material such as Cu or Al to the end portion on the winding end side of each superconducting wire.
[0023]
In particular, one end side where both superconducting wires are electrically connected is the winding start side of the coil, and the other end side is the winding end side, so that the terminal electrode is the winding end side, and the connection to the measuring instrument wire is made It can be done easily.
[0024]
Moreover, it is preferable to form a terminal for voltage measurement on at least the other end side of the superconducting wire. Various materials can be used for this terminal as long as the superconducting wire is easily soldered. For example, Al, Cu, Ag, etc. are suitable. Of these, Ag or an Ag alloy used as a stabilizer for superconducting wires is desirable. The terminal is preferably a thin film. A thin film terminal may be provided in contact with each superconducting wire.
[0025]
By providing a similar voltage measurement terminal on one end of the superconducting wire, the critical current can be obtained by measuring the voltage at one end and the other end of one of the two superconducting wires. . When a voltage measuring terminal is provided only on the other end of the superconducting wire, and the voltage between these terminals is measured, the voltage of the entire length of the two superconducting wires, including the resistance at the connection point (such as soldering) on one end of the superconducting wire Will be measured. If a voltage measuring terminal is also provided on one end side of the superconducting wire, one end of one superconducting wire can be measured by measuring the voltage between the terminals on the other end side, without including connection points such as soldering. The voltage at the side and the other end can be measured.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 is a schematic diagram of a reel wound with a superconducting wire used in the measuring method of the present invention.
[0027]
This reel 10 is made of stainless steel having a disc-shaped collar 12 on both sides of a cylindrical winding drum 11, and a pair of superconducting tape wires 20 integrated with insulating tape is wound around the winding drum 11. Has been.
[0028]
The superconducting tape wire 20 is a tape-like wire in which a plurality of Bi2223 superconducting filaments are embedded in a silver sheath as a stabilizing material. Here, a tape-shaped wire having a length of 100 m, a width of 4.1 mm, and a thickness of 0.24 mm was used.
[0029]
FIG. 2 shows an enlarged cross-sectional view of the winding start side of the superconducting tape wire 20. Two sheets of this superconducting wire are prepared, and both superconducting tape wires 21 and 22 are placed along an insulating tape 30 such as a polyimide tape (trade name: Kapton tape) having a thickness of 70 μm. Further, the reinforcing tape 40 is placed on one of the superconducting tape wires. As this reinforcing tape, a stainless steel tape 42 having a thickness of 0.1 mm and having a Kapton tape 41 bonded on both sides was used. The material of the reinforcing tape 40 is not particularly limited as long as it can hold the superconducting tape wire.
[0030]
Here, the positions slightly deviated from one ends of the superconducting tape wires 21 and 22 are joined by soldering and electrically connected. In this soldering, solder plating is performed on required portions of both the superconducting wires 21 and 22, and they are melt-bonded while being wound around the winding drum 11. Further, thin film terminals 61 and 62 for voltage measurement are provided at positions slightly shifted from the joint 50 to the other end sides of both superconducting wires. In this example, a silver foil with a thickness of 20 μm is partially interposed between one superconducting tape wire 21 and the insulating tape 30 and between the other superconducting tape wire 22 and the reinforcing tape 40 and fixed by soldering. Thus, the thin film terminals 61 and 62 were obtained.
[0031]
One end side of such a superconducting wire, that is, the side joined by soldering is wound around the reel drum 11 to form a single pancake coil. A winding start end fixing portion 13 is formed on the winding drum 11 (FIG. 1). Here, one end side of the superconducting wire was soldered between the winding drum 11 with a fixing jig of GFRP (Glass Fiber Reinforced Plastic), and the fixing jig was fixed with a bolt.
[0032]
On the other hand, a terminal electrode for passing a current and a thin film terminal for voltage measurement are formed on the other end side of the superconducting wire which is the winding end side. FIG. 3 shows a sectional view of the winding end side of the superconducting tape wire. The terminal electrode 70 was configured by soldering a copper piece to the other end of each superconducting wire. A predetermined current is passed through the superconducting tape wires 21 and 22 through the terminal electrodes. The thin film terminal 80 has the same configuration as the thin film terminals 61 and 62 described above, and is formed at a position shifted from the terminal electrode 70 toward the winding start side of the superconducting wire.
[0033]
When measuring the critical current of such a superconducting wire, after cooling the coil with liquid nitrogen to the superconducting state, a current is passed through the soldered joint at the beginning of winding between the terminal electrodes, and the superconducting tape This is done by measuring the generated voltage. At that time, two measurement methods can be used.
[0034]
As shown in FIG. 4, the first method is a method of measuring a critical current by connecting a measuring device 90 to a terminal electrode, passing a constant current and measuring a voltage between thin film terminals on the winding end side. . In FIG. 4, for convenience of explanation, the superconducting tape wire is shown in an expanded state, not in a wound state. In this method, the voltage over the entire length of the pair of superconducting tape wires is measured via the soldered joint. At that time, the current flowing through one superconducting tape wire 21 and the current flowing through the other superconducting tape wire 22 flow in opposite directions, so that by canceling the generated magnetic field, the current is influenced by the magnetic field even in the wound state. The critical current can be measured without decreasing.
[0035]
In the second method, as shown in FIG. 5, a power source 100 is connected to the terminal electrode, a constant current is passed through the superconducting wire, and a thin film terminal on one end side (start of winding) and a thin film on the other end side (end of winding). In this method, a measuring instrument 90 is connected between the terminals and the voltage between the two thin film terminals is measured. In FIG. 5, for convenience of explanation, the superconducting tape wire is shown in an expanded state, not in a wound state. In this method, the voltage is measured over the entire length of one superconducting tape wire 21 of the two superconducting tape wires. Since this method does not include a soldered joint between thin film terminals for measuring voltage, it is possible to measure the critical current more accurately without the influence of the resistance of the joint. After the critical current of one superconducting tape wire is measured, the critical current of the other superconducting tape wire 22 is measured in the same manner. Even in this second method, the direction of the current is reversed between the one superconducting tape wire 21 and the other superconducting tape wire 22, and the current is reduced by the influence of the magnetic field even in the wound state by canceling the generated magnetic field. The critical current can be measured without doing so.
[0036]
The voltage was measured over the entire length of one superconducting tape wire 21 by the second method, and the electric field strength was determined from the value obtained by dividing the voltage value by the length of the wire. The relationship between the current value and the electric field strength is shown in the graph of FIG. As shown in this graph, ¹⁰ ^- 10 V / cm electric field strength of the wire rod with high precision it can be seen that measuring the. Therefore, it is possible to evaluate the performance of the coil wire in the permanent current mode. Further, since the terminal electrode and the thin film terminal are provided at the end portion of the superconducting tape wire, it is not necessary to press the electrode or terminal against the intermediate portion of the superconducting tape wire, and the deterioration of the wire can be suppressed.
[0037]
【The invention's effect】
As described above, according to the method of the present invention, the current direction of each superconducting wire is reversed and the magnetic field is canceled by measuring by electrically connecting one end side of the two superconducting wires. Therefore, there is no decrease in the superconducting current due to the magnetic field, and low electric field characteristics with almost no magnetic field can be obtained. Therefore, it is possible to evaluate a coil wire for a permanent current mode that cannot be measured by the conventional method.
[0038]
Moreover, since the measurement can be performed in a coiled state, the critical current of a long superconducting wire can be measured, and a low electric field strength can be measured with a zero magnetic field.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a reel wound with a superconducting wire used in the measurement method of the present invention.
FIG. 2 is an enlarged sectional view showing a winding start side of a superconducting tape wire.
FIG. 3 is an enlarged sectional view showing a winding end side of a superconducting tape wire.
FIG. 4 is an explanatory diagram showing a first basic principle of the measurement method of the present invention.
FIG. 5 is an explanatory diagram showing a second basic principle of the measurement method of the present invention.
FIG. 6 is a graph showing the relationship between current and electric field strength.
FIG. 7 is an explanatory diagram of a conventional measurement method.
[Explanation of symbols]
10 reel
11 Rolling drum
12 collar
13 Fixed part
20, 21, 22 Superconducting tape wire
30 Insulation tape
40 Reinforcing tape
41 Kapton tape
42 Stainless steel tape
50 joints
61, 62 Thin film terminal
70 Terminal electrode
80 Thin film terminals
90 measuring instrument
100 power supply
210 Supply reel
220 Superconducting wire
230 Take-up reel
240 measuring instruments

Claims

The two superconducting wires along a stiffener while insulated, one end of both the superconducting wire are electrically connected to winding the superconducting wire in a coil shape,
Forming a voltage measuring terminal at a position shifted from the electrical connection point to the other end side on one end side of the superconducting wire;
The critical current of the one superconducting wire is measured by energizing from the other end of the superconducting wire and measuring the voltage between the voltage measuring terminal of the one superconducting wire and the other end of the superconducting wire. A critical current measurement method for high-temperature superconducting wires characterized by the following.

Two superconducting wires that are electrically connected at one end and arranged along each other;
An insulating material that insulates each of the superconducting wires other than one end side, and
A reinforcing member disposed along the superconducting wire;
Is fixed in a lump at one end of the superconducting wire and reinforcing material, a superconducting wire, e ingredients and winding cylinder insulation and reinforcement is wound,
Each superconducting wire winding structure of the high-temperature superconducting wire, characterized in Rukoto voltage measuring terminal is formed at a position shifted to the other end from an electrical connection point A at one end thereof.

In the two superconducting wires, one end side of the electrical connection portion is formed by superimposing the solder platings partially formed on each superconducting wire, and melting and joining the solder plating when the two superconducting wires are wound around the winding drum. The high-temperature superconducting wire winding structure according to claim 2 , wherein the winding structure is formed by: