JP2004172485A - Quenching detecting method and equipment of superconductive coil, - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quenching detecting method and equipment of a superconductive coil wherein quick and high sensitivity quenching detection is enabled. <P>SOLUTION: By using a Rogowskii coil 4, induced voltage V<SB>RC</SB>is detected by noncontact, and resistive voltage V<SB>r</SB>is obtained from the induced voltage. As a result, an intermediate terminal in the conventional difference method is unnecessary, application to a large-scale AC superconductive coil is also enabled. It is remarkably effective for preventing burning of a superconductive coil 12 that instant effective power P correlated with thermal stress to the superconductive coil 12 which stress is caused by quenching is used as parameter of generation of quenching. Further, by applying the instant effective power P to a low pass filter 9, a signal having high SN ratio is obtained. As a result, quenching is detected quickly with high sensitivity. <P>COPYRIGHT: (C)2004,JPO

Description

【００１９】
しかし、超伝導コイル１２にクエンチが生じると、常伝導部分に抵抗成分ｒが生じる。このとき、超伝導コイルの両端電圧Ｖ_ＳＣは、超伝導コイルの自己インダクタンスＬに対応する誘導性電圧と、抵抗成分ｒに対応する抵抗性電圧とで構成され、次式（２）のように表される。
【００２０】
【数２】

【００２１】
一方、超伝導コイルに流れる電流変化に伴って、検出コイルには誘導起電力が生じ、検出コイルの両端に誘起電圧Ｖ_ＲＣが検出される。このとき、被測定導体と検出コイルとの相互インダクタンスをＭとすると、誘起電圧Ｖ_ＲＣは、次式（３）のように表される。
【００２２】
【数３】

【００２３】
ここで、自己インダクタンスＬおよび相互インダクタンスＭは一定の値であるので、ｋ＝Ｌ／Ｍとなる定数ｋを求め、次式（４）のような演算を行うことにより、抵抗性電圧Ｖ_ｒが求められる。
【００２４】
【数４】

このように、検出コイルを用いることによって非接触で抵抗性電圧を求めることができる。このため、従来の差分法のような中間端子が不要であり、大型交流超伝導コイルにも適用できる。
【００２５】
また、求めた抵抗性電圧に電流値を乗じて瞬時有効電力に変換し、これをクエンチ検出のパラメータとして用いる。すなわち、次式（５）のような演算を行うことにより、瞬時有効電力Ｐが求められる。
【００２６】
【数５】

【００２７】
ここで、瞬時有効電力は、クエンチに伴う超伝導コイルへの熱的ストレスと相関するものである。このため、超伝導コイルの焼損を防止するために、瞬時有効電力をパラメータとして用いることは極めて有効である。
【００２８】
さらに、抵抗性電圧の値は、クエンチにより生じた抵抗成分の値を電流値に乗じたものであるから、この抵抗性電圧の値に電流値を乗じた瞬時有効電力は電流値の二乗に比例する数値であり、常に正の値を示す。このことは、出力される信号に直流成分を持たせたことに相当する。したがって、この瞬時有効電力に対応する信号をローパスフィルタに通すことによって、高いＳＮ比を持った信号が得られる。これは、直流成分はフィルタ処理をしても減衰しないが高周波のノイズは除去されるという特徴を利用したものであり、フィルタ処理という簡易な方法で高いＳＮ比を持った信号が得られるのである。これにより、クエンチを迅速かつ高感度に検出することができる。
【００２９】
また、本発明の検出方法および装置は、検出用コイルとして適当なものを選択することにより、直流超伝導コイル、交流超伝導コイルのいずれにも適用することができる。
【００３０】
請求項２および請求項５の発明によれば、超伝導コイルに流れる電流値は、検出コイルに流れる誘導起電力を積分して得る。このような構成によれば、検出用コイルの他に別途ＣＴ（変流器）等の電流検出器を使用する必要がないため、測定手順及び装置の構成を簡略化できる。
【００３１】
また、１つの検出器からの信号のみによって電流値と誘導起電力とを得る方法としては、例えば、ＣＴ等により電流値を直接に測定し、これを微分処理することによって誘導起電力（電流の微分値）を求めるという方法も考えられる。しかし、このような方法では、測定電流に電磁的ノイズが重畳した場合、微分演算によりノイズが拡大され、得られる信号のＳＮ比が低くなってしまうおそれがある。それに対して、本発明では、検出用コイルを用いて直接に誘導起電力を検出しており、微分演算を行う必要がないから、ノイズが拡大されるおそれがない。一方、電流値については、誘導起電力を積分処理することによって得るのであるが、積分処理によっては電磁的ノイズが拡大するおそれが少ない。このため、ＳＮ比の高い信号を得ることができ、クエンチを迅速かつ高感度に検出することができる。
【００３２】
請求項３および請求項６の発明によれば、検出用コイルとしてロゴスキーコイルを使用する。このロゴスキーコイルは、自身に流れる電流による磁束の影響を相殺して、超伝導コイルに流れる電流によって誘起される誘導起電力のみを検出ように設計されたものであるから、誘導起電力を精度良く得ることができる。これにより、クエンチを迅速かつ高感度に検出することができる。また、ロゴスキーコイルは簡易な構造であり、取り付けを容易に行うことができるので、測定手順及び装置を簡素化することができる。
【００３３】
【発明の実施の形態】
以下、本発明の超伝導コイルのクエンチ検出方法、及び装置を具体化した一実施形態について、図１〜図３を参照しつつ詳細に説明する。
【００３４】
本実施形態のクエンチ検出装置１は、超伝導コイル１２を備えた主回路１１に取り付けられて、この超伝導コイル１２のクエンチを検出するためのものである。
【００３５】
クエンチ検出装置１の回路図を図１に示した。クエンチ検出装置１が取り付けられる主回路１１には、交流電圧源１３、およびこの交流電圧源１３に接続された超伝導コイル１２が備えられている。この超伝導コイル１２は、液体窒素等の冷媒が満たされた容器１４内に収容されることにより冷却されている。
【００３６】
この超伝導コイル１２の両端にはそれぞれ端子２が取り付けられ、この端子２間には、コイル電圧検出回路３（本発明のコイル電圧検出手段に該当する）が接続され、両端子２間に生じる両端電圧Ｖ_ＳＣを検出できるようになっている。
また、主回路１１において超伝導コイル１２の近傍には、検出用コイルが取り付けられている。検出用コイルとしては、ロゴスキーコイル４を用いることができる。ロゴスキーコイル４は、図２に示すように導線４Ａをらせん状に周回させてコイル部４Ｂを形成させるとともに、そのコイル部４Ｂの一端の導線４Ａを折り返し状に屈曲してコイル内に貫通させ、さらにこのコイル部４Ｂを略円環状に回曲させたものである。そして、このロゴスキーコイル４は、円環内に主回路１１の導線１０を貫通させるようにして主回路１１に取り付けられている。このロゴスキーコイル４は、自身に流れる電流による磁束の影響を相殺して、主回路１１を流れる電流の変化によって誘起される誘起電圧Ｖ_ＲＣのみを検出できるように設計されたものであり、誘起電圧Ｖ_ＲＣを精度良く検出することが可能とされている。
【００３７】
ロゴスキーコイル４の両端は、このロゴスキーコイル４に誘起される誘起電圧Ｖ_ＲＣ出する誘起電圧検出回路５、およびこの誘起電圧Ｖ_ＲＣを積分処理することによって電流ｉの値を得るための積分回路６に接続されている。
【００３８】
コイル電圧検出回路３および誘起電圧検出回路５の出力端子は、電圧Ｖ_ＳＣ、Ｖ_ＲＣを減算処理して抵抗性電圧Ｖ_ｒを得るための減算回路７（本発明の減算手段に該当する）に接続されている。そして、この減算回路７の出力端子、および積分回路６の出力端子は、抵抗性電圧Ｖ_ｒと電流ｉの値とを乗算処理して瞬時有効電力Ｐを得るための乗算回路８（本発明の乗算手段に該当する）に接続される。さらに、乗算回路８の出力端子は、得られた瞬時有効電力Ｐに対応する信号についてノイズ成分の除去を行うためのローパスフィルタ９に接続されている。ローパスフィルタ９の出力端子は、例えば出力された値が所定の閾値を超えたときにクエンチが発生したことを判断して主回路１１を遮断する保護回路等（図示せず）に接続することができる。
【００３９】
以下、上記のように構成されたクエンチ検出装置１の動作について述べる。クエンチ検出装置１によるクエンチ検出の手順を示すフローチャートを図３に示した。
【００４０】
クエンチが発生せず、超伝導コイル１２が超伝導状態に保たれている場合は、抵抗成分ｒは発生しない。このとき、超伝導コイル１２の両端子２間に設置されたコイル電圧検出回路３により検出される両端電圧Ｖ_ＳＣは、超伝導コイル１２の自己インダクタンスＬに対応する誘導性電圧のみにより構成され、次式（１）のように表される。
【００４１】
【数６】

【００４２】
さて、超伝導コイル１２にクエンチが生じると、常伝導部分に抵抗成分ｒが生じる。このとき、コイル電圧検出回路３により検出される両端電圧Ｖ_ＳＣは、超伝導コイル１２の自己インダクタンスＬに対応する誘導性電圧と、抵抗成分ｒに対応する抵抗性電圧とで構成され、次式（２）のように表される（ステップＳ１）。
【００４３】
【数７】

【００４４】
一方、主回路１１を流れる電流の変化によって、主回路１１の導線１０周りの磁場が変化する。これに伴って、ロゴスキーコイル４に誘導起電力が生じ、誘起電圧検出回路５により誘起電圧Ｖ_ＲＣが検出される。このとき、主回路１１の導線１０とロゴスキーコイル４との相互インダクタンスをＭとすると、誘起電圧Ｖ_ＲＣは、次式（３）のように表される（ステップＳ２）。
【００４５】
【数８】

【００４６】
得られた両端電圧Ｖ_ＳＣと誘起電圧Ｖ_ＲＣとは減算回路７に入力される。ここで、自己インダクタンスＬおよび相互インダクタンスＭは一定の値である。したがって、ｋ＝Ｌ／Ｍとなる定数を求め、減算回路７において次式（４）のような演算を行うことにより、抵抗性電圧Ｖ_ｒが求められる（ステップＳ３）。
【００４７】
【数９】

【００４８】
ここで、得られた抵抗性電圧Ｖ_ｒには、超伝導コイル１２に流れるパルス性雑音電流、誘導雑音等の電磁的ノイズが含まれている。このため、この電磁的ノイズをキャンセルして高感度、迅速なクエンチ検出を可能とするため、抵抗性電圧Ｖ_ｒを瞬時有効電力Ｐに変換し、ノイズ除去を行う。
【００４９】
すなわち、ロゴスキーコイル４に生じた誘起電圧Ｖ_ＲＣは電流ｉの微分形となっているので、これを積分回路６において積分処理することにより、電流ｉの値が得られる（ステップＳ４）。
【００５０】
得られた電流ｉの値は、上記の減算回路７から出力された抵抗性電圧Ｖ_ｒとともに乗算回路８に入力される。乗算回路８においては、次式（５）のような演算を行うことにより、瞬時有効電力Ｐが求められる（ステップＳ５）。
【００５１】
【数１０】

【００５２】
得られた瞬時有効電力Ｐは、クエンチに伴う超伝導コイル１２への熱的ストレスと相関するものであるため、超伝導コイル１２の焼損を防止するために、瞬時有効電力Ｐをパラメータとして用いることは極めて有効である。
【００５３】
次に、この瞬時有効電力Ｐに対応する信号をローパスフィルタ９に通すことにより、ノイズ処理を行い、クエンチ信号Ｐ’に変換する（ステップＳ６）。ここで、式（５）に示されるように、瞬時有効電力Ｐはｉ^２に比例する数値であり、常に正の値を示す。このことは式（５）が直流成分を持っていることに相当する。したがって、この瞬時有効電力Ｐをローパスフィルタ９に通すと、直流成分は減衰しないが、高周波の電磁的ノイズは除去され、得られたクエンチ信号Ｐ’はＳＮ比の高い信号となる。
【００５４】
クエンチの検出は、例えば判断回路（図示せず）等によって、クエンチ信号Ｐ’とあらかじめ定めた閾値Ｐ_ｔ’との比較によって行われ、クエンチ信号Ｐ’が閾値Ｐ_ｔ’を超えた場合に、クエンチが発生したとの判定がなされる。この判断回路は、例えば警報装置に接続されて、クエンチ発生の判定がされた場合に警報が発信されるようにしておいても良い。また、保護回路に接続されて、クエンチ発生の判定がされた場合に主回路１１が遮断されるようにしておいても良い。
【００５５】
以上のように本実施形態によれば、ロゴスキーコイル４を使用することにより、非接触で誘起電圧Ｖ_ＲＣを検出し、これより抵抗性電圧Ｖ_ｒを求めることができる。このため、従来の差分法のような中間端子が不要であり、大型交流超伝導コイルにも適用できる。
【００５６】
また、クエンチに伴う超伝導コイル１２への熱的ストレスと相関する瞬時有効電力Ｐを、クエンチ発生のパラメータとして用いることは、超伝導コイル１２の焼損を防止するために極めて有効である。
さらに、瞬時有効電力Ｐは電流ｉの二乗に比例する数値であり、常に正の値を示す。このことは、出力される信号に直流成分を持たせたことに相当する。したがって、この瞬時有効電力Ｐをローパスフィルタ９に通すことによって高いＳＮ比を持った信号が得られる。これにより、クエンチを迅速かつ高感度に検出することができる。
【００５７】
また、電流ｉの値は、誘起電圧Ｖ_ＲＣを積分回路によって積分することにより得られる。このような構成によれば、ロゴスキーコイル４の他に別途ＣＴなどの電流検出器を主回路１１に取り付ける必要がないため、測定手順及び装置の構成を簡略化できる。また、積分処理によっては電磁的ノイズが拡大するおそれが少ない。このため、ＳＮ比の高い信号を得ることができ、クエンチを迅速かつ高感度に検出することができる。
【００５８】
さらに、検出用コイルとしてロゴスキーコイル４を使用する。これにより、誘起電圧Ｖ_ＲＣを精度良く検出することができ、クエンチを迅速かつ高感度に検出することができる。また、ロゴスキーコイル４は簡易な構造であり、取り付けを容易に行うことができるので、測定手順及び装置を簡素化することができる。
【００５９】
［実施例］
以下、実施例を挙げて本発明をさらに詳細に説明する。
【００６０】
＜実施例１＞（熱によるクエンチ）
１．試験装置
試験装置としては、上記実施形態と同様に組み立てたものを用いた。
超伝導コイルとしては、Ｂｉ−２２２３／Ａｇ高温超伝導コイル（（株）昭和電線電纜製）を用いた。この超伝導コイルは、２つのコイルが内層、外装に組み合わせられた２層構造であり、エポキシ樹脂含浸されている。また、臨界温度は１０９．２Ｋ、臨界電流は３Ａである。
主回路の電圧源としては、６０Ｈｚの商用周波数電圧源を用いた。
検出用コイルとしては、図４に示すように、二つのコイル中心が同じとなる空芯変圧器構造（一次巻線１５：主回路、二次巻線１６：誘起電圧検出用コイル）のコイル１７を用いた。なお、本実施例において、上記実施形態のようなロゴスキーコイルではなく空芯変圧器構造の検出用コイルを用いたのは、本実施例は臨界電流の低い小型コイルによる原理検証であるため、ロゴスキーコイルでは検出される誘起電圧Ｖ_ＲＣが微小になりやすく、検出感度が低くなってしまうからである。但し、実用上この検出用コイルは負荷になってはならないので、一次巻線が超伝導コイルや導線を含めた主回路の負荷に対して低負荷（１２回巻、巻線抵抗０．２７５Ω、自己インダクタンス２．１μＨ）となるようにした。
ローパスフィルタとしては、遮断周波数３０Ｈｚ（時定数５ｍｓ、一次）のものを用いた。
【００６１】
２．試験方法
電圧源から、２．０Ａｐｅａｋの一定電流を超伝導コイルに供給した。この状態で、超伝導コイルの周囲にヒータ（５０ｍｍ×１１０ｍｍ、０．７Ｗ）を配置し、超伝導コイルに熱を加えた。
各検出回路および演算回路から出力される両端電圧Ｖ_ＳＣ、誘起電圧Ｖ_ＲＣ、抵抗性電圧Ｖ_ｒ、電流ｉ、瞬時有効電力Ｐ、クエンチ信号Ｐ’、および誘起電圧Ｖ_ＲＣに定数ｋ（上記式（４）参照）を乗じたｋＶ_ＲＣの７つの波形をオシロスコープで観測した。
【００６２】
＜実施例２＞（過電流によるクエンチ）
試験装置としては、上記実施例１と同様のものを使用した。
電圧源から、２．０Ａｐｅａｋの一定電流を超伝導コイルに供給した。この状態で、８〜９Ａｐｅａｋの電流を突発的に通電した。
各検出回路および演算回路から出力される両端電圧Ｖ_ＳＣ、誘起電圧Ｖ_ＲＣ、抵抗性電圧Ｖ_ｒ、電流ｉ、瞬時有効電力Ｐ、クエンチ信号Ｐ’および誘起電圧Ｖ_ＲＣに定数ｋを乗じたｋＶ_ＲＣの７つの波形をオシロスコープで観測した。
【００６３】
＜結果と考察＞
１）熱によるクエンチ
図５には、実施例１における超伝導状態における両端電圧Ｖ_ＳＣ、および電流ｉの波形を表すグラフを、図６には、超伝導状態における誘起電圧Ｖ_ＲＣ、および電流ｉの波形を表すグラフを示した。また、図７には、両端電圧Ｖ_ＳＣの波形と、誘起電圧Ｖ_ＲＣに定数ｋ（＝Ｌ／Ｍ＝４３）を乗じたｋＶ_ＲＣの波形とを比較したグラフを示した。
【００６４】
図５、図６より、両電圧の波形は形状、電流ｉとの位相差もほぼ一致していることが分かる。また、図７より、Ｖ_ＳＣの波形とｋＶ_ＲＣの波形とはほぼ一致することが分かる。これより、クエンチが発生して超伝導コイルに抵抗成分ｒが発生した場合には、Ｖ_ＳＣとｋＶ_ＲＣとの差を求めることにより、式（２）における超伝導コイルの自己インダクタンスＬに対応する誘導性電圧（Ｌｄｉ／ｄｔ）を除去して抵抗性電圧Ｖ_ｒ（ｒｉ）を求めることができるといえる。
【００６５】
図８には、クエンチ発生前後の抵抗性電圧Ｖ_ｒの変化を表すグラフを、図９には、クエンチ発生前後の瞬時有効電力Ｐの変化を表すグラフを、図１０には、クエンチ発生前後のクエンチ信号Ｐ’の変化を表すグラフを示した。
【００６６】
図８、図９より、抵抗性電圧Ｖ_ｒ、瞬時有効電力Ｐのいずれも、クエンチ前後の信号の変化を明確に観測することができない。これは、クエンチ後に生じる抵抗成分ｒが小さいために、ＳＮ比の小さい信号となったためである。一方、図１０より、クエンチ信号Ｐ’は、測定開始後５．２秒で大きく上昇しており、クエンチ発生が明確に検出されている。このように、瞬時有効電力Ｐの信号からノイズ除去を行って得たクエンチ信号Ｐ’をパラメータとして用いることにより、クエンチを高感度で検出できることがわかる。
【００６７】
また、クエンチが発生する以前には抵抗成分ｒは発生しないため、クエンチ信号Ｐ’は０となるはずであるが、実際には２０ｍＷを示している。これは、交流損失相当である。本来、厳密に式（５）を表記しなおすと、交流損失（通電損失瞬時値）も含めて次式（６）のように示される。
【００６８】
【数１１】

【００６９】
ここで、Ｐ_{ＳＣ−Ｌｏｓｓ}は超伝導コイルの交流損失、Ｐ_{ＲＣ−Ｌｏｓｓ}は検出コイルの交流損失（但し、Ｐ_{ＲＣ−Ｌｏｓｓ}は、実際の損失のｋ倍相当）である。右辺カッコ内が両コイルの交流損失の差に相当する。この交流損失の差分がクエンチ以前に現れているのである。確認のため、本実施例の試験装置の通電状態における交流損失を次式（７）、（８）により算出した。
【００７０】
【数１２】

【００７１】
【数１３】

【００７２】
但し、Ｐ’_{ＳＣ−Ｌｏｓｓ}およびＰ’_{ＲＣ−Ｌｏｓｓ}は時間Ｔ（電流周期、１／６０ｓ）でのＰ_{ＳＣ−Ｌｏｓｓ}およびＰ_{ＲＣ−Ｌｏｓｓ}の平均値とした。その結果、Ｐ’_{ＳＣ−Ｌｏｓｓ}＝５４ｍＷ、Ｐ’_{ＲＣ−Ｌｏｓｓ}＝３４ｍＷであり、その差は２０ｍＷであった（図１１参照）。これより、その差２０ｍＷがクエンチ発生以前のＰ’として出力されていたことが確認された。
【００７３】
この交流損失は、超伝導コイルのクエンチの有無にかかわらず常に存在する。したがって、クエンチ信号Ｐ’を閾値と比較してクエンチ検出判定を行う場合には、交流損失を考慮して閾値を充分大きく設定する必要があり、クエンチ信号Ｐ’の変化量が交流損失と比較して小さい場合には、クエンチ発生を迅速かつ高感度に検出できなくなることが考えられる。しかし、図１０に示すように、通常は交流損失よりもクエンチ発生によるクエンチ信号Ｐ’の増大分のほうが充分に大きな値となる。したがって、本発明のクエンチ検出方法では、交流損失を考慮して閾値を充分大きな値とした場合でも、クエンチ発生を迅速かつ高感度に検出できるといえる。
【００７４】
２）過電流によるクエンチ
図１２には、実施例２におけるクエンチ発生前後のクエンチ信号Ｐ’、および電流の変化を表すグラフを示した。
【００７５】
本実施例で用いた超伝導コイルは、６０Ｈｚ、８Ａｐｅａｋの通電において２．５Ａ（瞬時値）程度でクエンチすることがあらかじめ分かっているので、クエンチは６．３秒時に生じたと考えられる。本実施例においても、実施例１と同様にクエンチ信号Ｐ’は、クエンチ発生後に大きく上昇しており、クエンチ発生が明確に検出されていることがわかる。クエンチ信号Ｐ’は実施例１と比較して急激に増大していることから、過電流によるクエンチの場合は熱によるクエンチと比較して常伝導転移、および常伝導部分の拡大が急激に進んでいるものと考えられる。なお、６．３秒以前に生じている数ｍＷのクエンチ信号Ｐ’は、交流損失によるものと考えられる。
【００７６】
以上のように、本発明のクエンチ検出方法によれば、クエンチ発生を迅速かつ高感度に検出できることがわかった。
本発明の技術的範囲は、上記した実施形態によって限定されるものではなく、例えば、次に記載するようなものも本発明の技術的範囲に含まれる。その他、本発明の技術的範囲は、均等の範囲にまで及ぶものである。
（１）上記実施形態では、検出コイルにより得られた誘起電圧Ｖ_ＲＣを積分回路により積分することによって電流値を得ているが、本発明によれば電流値を得る手段は上記実施形態に限るものではなく、例えばＣＴ等の電流検出器により電流値を直接に測定しても良い。
（２）上記実施形態では、減算手段、乗算手段等の演算手段としてアナログ演算により処理を行う回路を用いているが、本発明によればこれらの手段の構成は上記実施形態に限るものではなく、デジタル演算により処理を行うものであっても良い。
【図面の簡単な説明】
【図１】本実施形態のクエンチ検出装置の回路図
【図２】本実施形態の検出用コイルを示す部分拡大図
【図３】本実施形態のクエンチ検出装置によるクエンチ検出の手順を示すフローチャート
【図４】実施例の検出用コイルを示す部分拡大図
【図５】実施例１における超伝導状態における両端電圧Ｖ_ＳＣ、および電流ｉの波形を表すグラフ
【図６】実施例１における超伝導状態における誘起電圧Ｖ_ＲＣ、および電流ｉの波形を表すグラフ
【図７】実施例１における両端電圧Ｖ_ＳＣの波形と、誘起電圧Ｖ_ＲＣに定数ｋを乗じたｋＶ_ＲＣの波形とを比較したグラフ
【図８】実施例１におけるクエンチ発生前後の抵抗性電圧Ｖ_ｒの変化を表すグラフ
【図９】実施例１におけるクエンチ発生前後の瞬時有効電力Ｐの変化を表すグラフ
【図１０】実施例１におけるクエンチ発生前後のクエンチ信号Ｐ’の変化を表すグラフ
【図１１】実施例１における、超伝導コイルの交流損失に基づくＰ’_{ＳＣ−Ｌｏｓｓ}、および検出用コイルの交流損失に基づくＰ’_{ＲＣ−Ｌｏｓｓ}を表すグラフ
【図１２】実施例２におけるクエンチ発生前後の部分有効電流Ｐ’、および通電電流の変化を表すグラフ
【図１３】従来の差分法によるクエンチ検出装置の回路を示す部分拡大図
【符号の説明】
１…クエンチ検出装置
３…コイル電圧検出回路
４…ロゴスキーコイル（検出コイル）
６…積分回路（電流検出手段）
７…減算回路（減算手段）
８…乗算回路（乗算手段）
９…ローパスフィルタ
１２…超伝導コイル[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for detecting a quench of a superconducting coil.
[0002]
[Prior art]
A superconducting device such as a superconducting linear motor or a superconducting energy storage device is configured using a superconducting coil wound with a superconducting material having an electric resistance of 0 at a predetermined critical temperature or lower.
[0003]
This superconducting coil (hereinafter sometimes simply referred to as “coil”) is usually cooled to a very low temperature and maintains a superconducting state. For example, when an overcurrent exceeding the critical current is applied, a transition (quenching) phenomenon to a normal conduction state may occur. In such a case, if the operation of the apparatus is continued as it is, the coil may be burnt out, and eventually the apparatus may be damaged. Therefore, the occurrence of quench is detected quickly and with high sensitivity to protect the apparatus. This is very important.
[0004]
Conventionally, the most rapid and reliable method for detecting the quench phenomenon is to perform detection based on the resistance component generated in the normal conducting portion when the superconducting material partially transitions to the normal conducting state. It is considered to be a high method, and “difference method” and “phase difference method” have been developed as specific methods.
[0005]
The outline of the difference method is as follows. As shown in FIG. 13, by providing terminals 101 at both ends of the superconducting coil 100, extracting an intermediate terminal 102 from the middle of the superconducting coil 100, and connecting two resistors 103 and a voltage detector 104. A so-called “Wheatstone bridge”. When the superconducting coil 100 is in the superconducting state, the voltage value detected by the voltage detector 104 is 0. However, when a quench occurs and the resistance occurs in the superconducting coil 100, the balance of the bridge is lost and the resistive voltage is reduced. Is detected by the voltage detector 104. Thus, it is determined that quench has occurred (see Non-Patent Document 1).
[0006]
The phase difference method detects a quench by detecting a phase change of a current and a voltage due to a resistance component generated by the quench.
[0007]
[Non-patent document 1]
Electron Theory B, Vol. 121, No. 8, pp. 1029-1035 (2001)
[0008]
[Problems to be solved by the invention]
However, in the case of using the difference method, it is necessary to draw out an intermediate terminal from the superconducting coil. However, in the case of a large AC superconducting coil, it is difficult to cope with a high-voltage induced current generated in the coil, so that an intermediate terminal cannot be attached. For this reason, there is a drawback that it can be applied only to DC coils and small AC coils. Further, since the detected resistive voltage is affected by a pulsed noise current, an induced noise, and the like flowing through the coil, it is difficult to detect the quench quickly and with high sensitivity.
[0009]
On the other hand, in the case of the phase difference method, since the resistance component generated by quenching is smaller than the large inductance of the coil, the phase change is extremely small, and the resistance component is easily buried in noise. For this reason, it is difficult to detect a phase change, and it becomes difficult to detect a quench with high accuracy. There is also a drawback that it can only be applied to AC systems.
[0010]
The present invention has been completed based on the above circumstances, and an object of the present invention is to provide a method and an apparatus for detecting a quench of a superconducting coil, which are capable of detecting a quench quickly and with high sensitivity.
[0011]
[Means for Solving the Problems]
A quench detection method according to claim 1 for solving the above-mentioned problem is a quench detection method for detecting a quench of a superconducting coil, comprising: a voltage across the superconducting coil; Calculates the resistive voltage associated with the quench based on the induced electromotive force of the detection coil responsive to the change in the current flowing through the superconducting coil, and multiplies this by the value of the current flowing through the superconducting coil. Power is calculated, and a signal corresponding to the instantaneous active power is passed through a low-pass filter to be used as a quench detection parameter.
[0012]
The invention according to claim 2 is the quench detection method according to claim 1, wherein a current value flowing through the superconducting coil is obtained by integrating an induced electromotive force of the detection coil.
[0013]
The invention according to claim 3 is the quench detection method according to claim 1 or 2, wherein the detection coil is a Rogowski coil.
[0014]
The invention according to claim 4 is a quench detection device for detecting a quench of a superconducting coil, wherein the coil voltage detecting means detects a voltage between both ends of the superconducting coil; A detecting coil for generating an induced electromotive force, a current detecting means for detecting a current flowing through the superconducting coil, a voltage across the superconducting coil detected by the coil voltage detecting means, and an induced electromotive force of the detecting coil. Subtraction means for calculating a resistive voltage associated with the quench of the superconducting coil based on the following formula; and multiplying means for multiplying the current of the superconducting coil detected by the current detecting means by the resistive voltage to obtain instantaneous active power. And a low-pass filter for removing a noise component from the signal corresponding to the instantaneous active power.
[0015]
According to a fifth aspect of the present invention, there is provided the quench detection device for a superconducting coil according to the fourth aspect, wherein the current detection means includes an integration circuit for integrating an induced electromotive force of the detection coil. Features.
[0016]
The invention according to claim 6 is the quench detection device for a superconducting coil according to claim 4 or 5, wherein the detection coil is a Rogowski coil.
[0017]
Function and effect of the present invention
According to the first and fourth aspects of the present invention, the resistive voltage is obtained based on the voltage between both ends of the superconducting coil and the induced electromotive force of the detecting coil which is sensitive to a change in the current flowing through the superconducting coil. That is, when no quench occurs, the voltage V across the superconducting coil is _SC Is composed only of an inductive voltage corresponding to the self-inductance L of the superconducting coil, and is expressed by the following equation (1).
[0018]
(Equation 1)

[0019]
However, when the quench occurs in the superconducting coil 12, a resistance component r is generated in the normal conduction portion. At this time, the voltage V across the superconducting coil _SC Is composed of an inductive voltage corresponding to the self-inductance L of the superconducting coil and a resistive voltage corresponding to the resistance component r, and is expressed by the following equation (2).
[0020]
(Equation 2)

[0021]
On the other hand, as the current flowing through the superconducting coil changes, an induced electromotive force is generated in the detection coil, and the induced voltage V is applied to both ends of the detection coil. _RC Is detected. At this time, if the mutual inductance between the conductor to be measured and the detection coil is M, the induced voltage V _RC Is represented by the following equation (3).
[0022]
[Equation 3]

[0023]
Here, since the self-inductance L and the mutual inductance M are constant values, a constant k that satisfies k = L / M is obtained, and an operation as shown in the following equation (4) is performed. _r Is required.
[0024]
(Equation 4)

As described above, the resistance voltage can be obtained in a non-contact manner by using the detection coil. For this reason, the intermediate terminal unlike the conventional difference method is unnecessary, and the present invention can be applied to a large AC superconducting coil.
[0025]
Further, the obtained resistive voltage is multiplied by a current value to convert it into instantaneous active power, which is used as a parameter for quench detection. That is, the instantaneous active power P is obtained by performing an operation such as the following equation (5).
[0026]
(Equation 5)

[0027]
Here, the instantaneous active power correlates with the thermal stress on the superconducting coil accompanying the quench. Therefore, it is extremely effective to use the instantaneous active power as a parameter in order to prevent burning of the superconducting coil.
[0028]
Furthermore, since the value of the resistive voltage is obtained by multiplying the value of the resistance component caused by the quench by the current value, the instantaneous active power obtained by multiplying the value of the resistive voltage by the current value is proportional to the square of the current value. And always indicate a positive value. This corresponds to giving a DC component to the output signal. Therefore, by passing the signal corresponding to this instantaneous active power through a low-pass filter, a signal having a high SN ratio can be obtained. This utilizes the characteristic that the DC component is not attenuated even if filtered, but high-frequency noise is removed, and a signal having a high SN ratio can be obtained by a simple method called filtering. . Thereby, quench can be detected quickly and with high sensitivity.
[0029]
Further, the detection method and apparatus of the present invention can be applied to both a DC superconducting coil and an AC superconducting coil by selecting an appropriate coil for detection.
[0030]
According to the second and fifth aspects of the present invention, the value of the current flowing through the superconducting coil is obtained by integrating the induced electromotive force flowing through the detection coil. According to such a configuration, there is no need to separately use a current detector such as a CT (current transformer) in addition to the detection coil, so that the measurement procedure and the configuration of the apparatus can be simplified.
[0031]
In addition, as a method of obtaining a current value and an induced electromotive force only by a signal from one detector, for example, the current value is directly measured by CT or the like, and differentiated to obtain an induced electromotive force (current value). (Differential value) is also conceivable. However, in such a method, when the electromagnetic noise is superimposed on the measured current, the noise is enlarged by the differential operation, and the SN ratio of the obtained signal may be reduced. On the other hand, in the present invention, the induced electromotive force is directly detected by using the detection coil, and there is no need to perform the differential operation, so that there is no possibility that the noise is enlarged. On the other hand, the current value is obtained by integrating the induced electromotive force, but there is little possibility that the electromagnetic noise is increased by the integration process. Therefore, a signal having a high SN ratio can be obtained, and quench can be detected quickly and with high sensitivity.
[0032]
According to the third and sixth aspects of the present invention, a Rogowski coil is used as the detection coil. This Rogowski coil is designed to cancel only the induced electromotive force induced by the current flowing in the superconducting coil by canceling out the effect of the magnetic flux caused by the current flowing through itself, so that the induced electromotive force can be accurately detected. Can get better. Thereby, quench can be detected quickly and with high sensitivity. In addition, the Rogowski coil has a simple structure and can be easily mounted, so that the measurement procedure and the apparatus can be simplified.
[0033]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a quench detection method and apparatus for a superconducting coil according to the present invention will be described in detail with reference to FIGS.
[0034]
The quench detection device 1 of the present embodiment is attached to a main circuit 11 having a superconducting coil 12, and detects a quench of the superconducting coil 12.
[0035]
The circuit diagram of the quench detection device 1 is shown in FIG. The main circuit 11 to which the quench detection device 1 is attached includes an AC voltage source 13 and a superconducting coil 12 connected to the AC voltage source 13. The superconducting coil 12 is cooled by being accommodated in a container 14 filled with a refrigerant such as liquid nitrogen.
[0036]
Terminals 2 are attached to both ends of the superconducting coil 12, respectively. A coil voltage detecting circuit 3 (corresponding to a coil voltage detecting means of the present invention) is connected between the terminals 2, and is generated between the two terminals 2. Voltage V _SC Can be detected.
Further, a detection coil is attached near the superconducting coil 12 in the main circuit 11. The Rogowski coil 4 can be used as the detection coil. As shown in FIG. 2, the Rogowski coil 4 spirally wraps the conductive wire 4A to form a coil portion 4B, and bends the conductive wire 4A at one end of the coil portion 4B in a folded shape to penetrate the coil. Further, the coil portion 4B is bent in a substantially annular shape. The Rogowski coil 4 is attached to the main circuit 11 such that the conductor 10 of the main circuit 11 passes through the ring. The Rogowski coil 4 cancels out the influence of the magnetic flux due to the current flowing through itself, and the induced voltage V induced by the change in the current flowing through the main circuit 11. _RC Is designed to detect only the induced voltage V _RC Is detected with high accuracy.
[0037]
Both ends of the Rogowski coil 4 are connected to an induced voltage V induced in the Rogowski coil 4. _RC The induced voltage detection circuit 5 and the induced voltage V _RC Is integrated into an integrating circuit 6 for obtaining the value of the current i.
[0038]
The output terminals of the coil voltage detection circuit 3 and the induced voltage detection circuit 5 _SC , V _RC To the resistive voltage V _r Is connected to a subtraction circuit 7 (corresponding to the subtraction means of the present invention). The output terminal of the subtraction circuit 7 and the output terminal of the integration circuit 6 are connected to the resistive voltage V _r And the value of the current i are connected to a multiplication circuit 8 (corresponding to the multiplication means of the present invention) for obtaining an instantaneous active power P. Further, the output terminal of the multiplication circuit 8 is connected to a low-pass filter 9 for removing a noise component from the signal corresponding to the obtained instantaneous active power P. The output terminal of the low-pass filter 9 may be connected to a protection circuit or the like (not shown) that determines that quench has occurred when the output value exceeds a predetermined threshold value and shuts off the main circuit 11. it can.
[0039]
Hereinafter, the operation of the quench detection device 1 configured as described above will be described. FIG. 3 is a flowchart showing the procedure of quench detection by the quench detection device 1.
[0040]
When no quench occurs and the superconducting coil 12 is kept in the superconducting state, the resistance component r does not occur. At this time, the terminal voltage V detected by the coil voltage detection circuit 3 installed between both terminals 2 of the superconducting coil 12 _SC Is composed only of an inductive voltage corresponding to the self-inductance L of the superconducting coil 12, and is expressed by the following equation (1).
[0041]
(Equation 6)

[0042]
Now, when quench occurs in the superconducting coil 12, a resistance component r is generated in the normal conduction portion. At this time, the both-ends voltage V detected by the coil voltage detection circuit 3 _SC Is composed of an inductive voltage corresponding to the self-inductance L of the superconducting coil 12 and a resistive voltage corresponding to the resistance component r, and is represented by the following equation (2) (step S1).
[0043]
(Equation 7)

[0044]
On the other hand, a change in the current flowing through the main circuit 11 changes a magnetic field around the conductor 10 of the main circuit 11. Accordingly, an induced electromotive force is generated in the Rogowski coil 4, and the induced voltage V _RC Is detected. At this time, assuming that the mutual inductance between the conductor 10 of the main circuit 11 and the Rogowski coil 4 is M, the induced voltage V _RC Is represented by the following equation (3) (step S2).
[0045]
(Equation 8)

[0046]
Obtained voltage V between both ends _SC And induced voltage V _RC Is input to the subtraction circuit 7. Here, the self-inductance L and the mutual inductance M are constant values. Therefore, a constant that satisfies k = L / M is obtained, and the subtraction circuit 7 performs an operation such as the following equation (4), thereby obtaining the resistive voltage V _r Is obtained (step S3).
[0047]
(Equation 9)

[0048]
Here, the obtained resistive voltage V _r Includes electromagnetic noise such as a pulsed noise current flowing through the superconducting coil 12 and induction noise. For this reason, in order to cancel the electromagnetic noise and enable high sensitivity and quick quench detection, the resistive voltage V _r Is converted into an instantaneous active power P, and noise is removed.
[0049]
That is, the induced voltage V generated in the Rogowski coil 4 _RC Is a differential form of the current i, and is integrated by the integration circuit 6 to obtain the value of the current i (step S4).
[0050]
The value of the obtained current i is determined by the resistance voltage V output from the subtraction circuit 7. _r Is input to the multiplication circuit 8 together with the data. In the multiplication circuit 8, the instantaneous active power P is obtained by performing an operation such as the following equation (5) (step S5).
[0051]
(Equation 10)

[0052]
Since the obtained instantaneous active power P is correlated with the thermal stress on the superconducting coil 12 due to quench, the instantaneous active power P is used as a parameter in order to prevent burning of the superconducting coil 12. Is extremely effective.
[0053]
Next, the signal corresponding to the instantaneous active power P is passed through the low-pass filter 9 to perform noise processing, and is converted into a quench signal P ′ (step S6). Here, as shown in Expression (5), the instantaneous active power P is i ² And is always a positive value. This corresponds to equation (5) having a DC component. Therefore, when the instantaneous active power P is passed through the low-pass filter 9, the DC component is not attenuated, but high-frequency electromagnetic noise is removed, and the obtained quench signal P 'becomes a signal having a high SN ratio.
[0054]
The quench is detected by, for example, a determination circuit (not shown) or the like, by using a quench signal P ′ and a predetermined threshold P _t Quenching signal P ' _t If it exceeds', it is determined that quench has occurred. This judging circuit may be connected to, for example, an alarm device so that an alarm is issued when it is determined that quench has occurred. Alternatively, the main circuit 11 may be connected to a protection circuit so that the main circuit 11 is shut off when it is determined that quench has occurred.
[0055]
As described above, according to the present embodiment, by using the Rogowski coil 4, the induced voltage V _RC Is detected, and the resistive voltage V _r Can be requested. For this reason, the intermediate terminal unlike the conventional difference method is unnecessary, and the present invention can be applied to a large AC superconducting coil.
[0056]
Using the instantaneous active power P correlated with the thermal stress on the superconducting coil 12 due to quench as a parameter for quench generation is extremely effective for preventing the superconducting coil 12 from burning out.
Further, the instantaneous active power P is a numerical value proportional to the square of the current i, and always shows a positive value. This corresponds to giving a DC component to the output signal. Therefore, by passing this instantaneous active power P through the low-pass filter 9, a signal having a high SN ratio can be obtained. Thereby, quench can be detected quickly and with high sensitivity.
[0057]
Further, the value of the current i is the induced voltage V _RC Is integrated by an integrating circuit. According to such a configuration, it is not necessary to separately attach a current detector such as a CT to the main circuit 11 in addition to the Rogowski coil 4, so that the measurement procedure and the configuration of the apparatus can be simplified. Also, depending on the integration process, there is little possibility that electromagnetic noise will expand. Therefore, a signal having a high SN ratio can be obtained, and quench can be detected quickly and with high sensitivity.
[0058]
Further, a Rogowski coil 4 is used as a detection coil. Thereby, the induced voltage V _RC Can be accurately detected, and quench can be detected quickly and with high sensitivity. In addition, since the Rogowski coil 4 has a simple structure and can be easily mounted, the measurement procedure and the apparatus can be simplified.
[0059]
[Example]
Hereinafter, the present invention will be described in more detail with reference to examples.
[0060]
<Example 1> (Quench by heat)
1. Testing equipment
As the test device, a device assembled in the same manner as in the above embodiment was used.
As the superconducting coil, a Bi-2223 / Ag high-temperature superconducting coil (manufactured by Showa Electric Cable Co., Ltd.) was used. This superconducting coil has a two-layer structure in which two coils are combined with an inner layer and an outer layer, and is impregnated with epoxy resin. The critical temperature is 109.2K and the critical current is 3A.
A 60 Hz commercial frequency voltage source was used as the voltage source for the main circuit.
As shown in FIG. 4, a coil 17 having an air-core transformer structure (primary winding 15: main circuit, secondary winding 16: induced voltage detecting coil) having the same two coil centers is used as the detection coil. Was used. In the present embodiment, the use of a detection coil having an air-core transformer structure instead of the Rogowski coil as in the above embodiment is because the present embodiment is a principle verification using a small coil having a low critical current. Induced voltage V detected in Rogowski coil _RC Is likely to be minute, and the detection sensitivity is lowered. However, since the detection coil should not be a load in practical use, the primary winding has a low load (12 turns, a winding resistance of 0.275 Ω, a load of the main circuit including the superconducting coil and the conductor). (Self-inductance: 2.1 μH).
A low-pass filter having a cutoff frequency of 30 Hz (time constant of 5 ms, primary) was used.
[0061]
2. Test method
A constant current of 2.0 Apeek was supplied to the superconducting coil from a voltage source. In this state, a heater (50 mm × 110 mm, 0.7 W) was arranged around the superconducting coil, and heat was applied to the superconducting coil.
The voltage V output between both terminals output from each detection circuit and arithmetic circuit _SC , Induced voltage V _RC , Resistive voltage V _r , Current i, instantaneous active power P, quench signal P ′, and induced voltage V _RC Multiplied by a constant k (see equation (4) above) _RC Were observed with an oscilloscope.
[0062]
<Example 2> (Quench by overcurrent)
As the test device, the same device as in Example 1 was used.
A constant current of 2.0 Peak was supplied to the superconducting coil from a voltage source. In this state, a current of 8 to 9 Apeak was suddenly applied.
The voltage V output between both terminals output from each detection circuit and arithmetic circuit _SC , Induced voltage V _RC , Resistive voltage V _r , Current i, instantaneous active power P, quench signal P ′ and induced voltage V _RC Multiplied by constant k _RC Were observed with an oscilloscope.
[0063]
<Results and discussion>
1) Quench by heat
FIG. 5 shows the voltage V between both ends in the superconducting state in the first embodiment. _SC FIG. 6 shows the induced voltage V in the superconducting state. _RC , And a graph showing the waveform of the current i. Also, FIG. _SC And the induced voltage V _RC Multiplied by a constant k (= L / M = 43) _RC A graph comparing with the waveform of FIG.
[0064]
From FIGS. 5 and 6, it can be seen that the waveforms of the two voltages have substantially the same shape and the phase difference with the current i. Also, from FIG. _SC Waveform and kV _RC It can be seen that the waveform almost coincides with the waveform shown in FIG. Thus, when the quench occurs and the resistance component r occurs in the superconducting coil, V _SC And kV _RC , The inductive voltage (Ldi / dt) corresponding to the self-inductance L of the superconducting coil in equation (2) is removed, and the resistive voltage V _r (Ri) can be obtained.
[0065]
FIG. 8 shows the resistance voltage V before and after the quench occurs. _r 9 is a graph showing a change in the instantaneous active power P before and after the occurrence of a quench, and FIG. 10 is a graph showing a change in the quench signal P ′ before and after the occurrence of a quench.
[0066]
8 and 9, the resistive voltage V _r In any of the instantaneous active powers P, changes in the signal before and after the quench cannot be clearly observed. This is because the signal having a small SN ratio was generated because the resistance component r generated after the quench was small. On the other hand, from FIG. 10, the quench signal P ′ greatly rises 5.2 seconds after the start of the measurement, and the occurrence of quench is clearly detected. As described above, it can be seen that quenching can be detected with high sensitivity by using the quench signal P ′ obtained by performing noise removal from the signal of the instantaneous active power P as a parameter.
[0067]
In addition, since the resistance component r does not occur before the occurrence of the quench, the quench signal P 'should be 0, but actually indicates 20 mW. This is equivalent to AC loss. Originally, when Expression (5) is strictly rewritten, it is expressed as in the following Expression (6) including the AC loss (the instantaneous value of the conduction loss).
[0068]
[Equation 11]

[0069]
Where P _SC-Loss Is the AC loss of the superconducting coil, P _RC-Loss Is the AC loss of the detection coil (however, P _RC-Loss Is k times the actual loss). The value in parentheses on the right side corresponds to the difference between the AC losses of both coils. This difference in AC loss appears before the quench. For confirmation, the AC loss in the energized state of the test apparatus of this example was calculated by the following equations (7) and (8).
[0070]
(Equation 12)

[0071]
(Equation 13)

[0072]
However, P ' _SC-Loss And P ' _RC-Loss Is P at time T (current cycle, 1 / 60s) _SC-Loss And P _RC-Loss Was the average value. As a result, P ' _SC-Loss = 54mW, P ' _RC-Loss = 34 mW, and the difference was 20 mW (see FIG. 11). From this, it was confirmed that the difference of 20 mW was output as P 'before the occurrence of the quench.
[0073]
This AC loss is always present regardless of whether the superconducting coil is quenched. Therefore, when performing quench detection determination by comparing the quench signal P ′ with a threshold, it is necessary to set the threshold sufficiently large in consideration of the AC loss, and the amount of change in the quench signal P ′ is compared with the AC loss. If it is too small, quenching may not be detected quickly and with high sensitivity. However, as shown in FIG. 10, the increase of the quench signal P ′ due to the occurrence of the quench usually takes a sufficiently larger value than the AC loss. Therefore, it can be said that the quench detection method of the present invention can detect the occurrence of quench quickly and with high sensitivity even when the threshold is set to a sufficiently large value in consideration of the AC loss.
[0074]
2) Quench by overcurrent
FIG. 12 is a graph illustrating changes in the quench signal P ′ and the current before and after the occurrence of quench in the second embodiment.
[0075]
Since it is known in advance that the superconducting coil used in this example quench at about 2.5 A (instantaneous value) when energizing at 60 Hz and 8 Apeak, it is considered that the quench occurred at 6.3 seconds. Also in this embodiment, as in the first embodiment, the quench signal P 'rises significantly after the occurrence of the quench, and it can be seen that the occurrence of the quench is clearly detected. Since the quench signal P ′ is sharply increased as compared with the first embodiment, the normal conduction transition and the enlargement of the normal conduction portion of the quench caused by the overcurrent progress more rapidly than the quench caused by the heat. It is considered that there is. The quench signal P ′ of several mW generated before 6.3 seconds is considered to be due to AC loss.
[0076]
As described above, according to the quench detection method of the present invention, it was found that the occurrence of quench can be detected quickly and with high sensitivity.
The technical scope of the present invention is not limited by the above-described embodiments, and, for example, those described below are also included in the technical scope of the present invention. In addition, the technical scope of the present invention extends to an equivalent range.
(1) In the above embodiment, the induced voltage V obtained by the detection coil _RC The current value is obtained by integrating the current value by an integration circuit. However, according to the present invention, the means for obtaining the current value is not limited to the above embodiment, and the current value is directly measured by a current detector such as a CT. You may.
(2) In the above embodiment, a circuit that performs processing by analog operation is used as arithmetic means such as subtraction means and multiplication means. However, according to the present invention, the configuration of these means is not limited to the above embodiment. Alternatively, the processing may be performed by digital operation.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a quench detection device according to an embodiment.
FIG. 2 is a partially enlarged view showing a detection coil of the embodiment.
FIG. 3 is a flowchart illustrating a quench detection procedure performed by the quench detection device according to the embodiment;
FIG. 4 is a partially enlarged view showing a detection coil of the embodiment.
FIG. 5 is a diagram illustrating a voltage V across the superconducting state according to the first embodiment. _SC , And a graph representing the waveform of the current i
FIG. 6 shows an induced voltage V in a superconducting state in Example 1. _RC , And a graph representing the waveform of the current i
FIG. 7 shows a voltage V between both terminals in the first embodiment. _SC And the induced voltage V _RC Multiplied by constant k _RC Graph comparing with waveform of
FIG. 8 shows a resistance voltage V before and after the occurrence of a quench in Example 1. _r Graph showing changes in
FIG. 9 is a graph showing a change in instantaneous active power P before and after the occurrence of a quench in the first embodiment.
FIG. 10 is a graph showing a change in a quench signal P ′ before and after the occurrence of a quench in the first embodiment.
FIG. 11 shows P ′ based on the AC loss of the superconducting coil in the first embodiment. _SC-Loss , And P ′ based on the AC loss of the detection coil _RC-Loss Graph representing
FIG. 12 is a graph showing a change in a partial effective current P ′ before and after the occurrence of a quench and a change in a conduction current in Example 2.
FIG. 13 is a partially enlarged view showing a circuit of a conventional quench detection device using a difference method.
[Explanation of symbols]
1. Quench detection device
3: Coil voltage detection circuit
4. Rogowski coil (detection coil)
6. Integrating circuit (current detecting means)
7. Subtraction circuit (subtraction means)
8. Multiplication circuit (multiplication means)
9 ... Low-pass filter
12 ... Superconducting coil

Claims (6)

A quench detection method for detecting a quench of a superconducting coil, comprising: a quench based on a voltage across the superconducting coil and an induced electromotive force of a detecting coil responsive to a change in current flowing through the superconducting coil. Calculate the resistive voltage, calculate the instantaneous active power generated in the superconducting coil by multiplying this by the current value flowing in the superconducting coil, and quench the signal corresponding to the instantaneous active power through a low-pass filter. A method for detecting quench of a superconducting coil, wherein the method is used as a detection parameter. The quench detection method for a superconducting coil according to claim 1, wherein the current value flowing through the superconducting coil is obtained by integrating an induced electromotive force of the detection coil. The method according to claim 1 or 2, wherein the detection coil is a Rogowski coil. A quench detection device for detecting a quench of a superconducting coil,
Coil voltage detection means for detecting the voltage across the superconducting coil,
A detection coil that generates an induced electromotive force in response to a change in current flowing through the superconducting coil;
Current detection means for detecting a current flowing through the superconducting coil,
Subtraction means for calculating a resistive voltage associated with the quench of the superconducting coil based on the voltage across the superconducting coil detected by the coil voltage detecting means and the induced electromotive force of the detection coil,
Multiplying means for obtaining the instantaneous active power by multiplying the current of the superconducting coil detected by the current detecting means by the resistive voltage,
A quench detection device for a superconducting coil, comprising: a low-pass filter that removes a noise component from a signal corresponding to the instantaneous active power. The quench detecting device for a superconducting coil according to claim 4, wherein the current detecting means includes an integrating circuit for integrating an induced electromotive force of the detecting coil. The quench detection device for a superconducting coil according to claim 4, wherein the detection coil is a Rogowski coil.

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