JP2004153877A - Method of discriminating arc current, and arc current discriminator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an arc current discriminating method and an arc current discriminator which can detect the abnormal current of an AC circuit caused by the arc short circuit phenomena by the short circuit between core wires or the series arc phenomena by the cutting of the core wire without causing incorrect detection with a normal load current. <P>SOLUTION: In this arc current discriminating method, this arc current discriminator detects each current peak time A(n) until the point of time when it comes to the current peak values Ipeak1, Ipeak2 etc. of a positive half wave and the current peak values Ipeak1' and Ipeak2' of a negative half wave from the point of time of zero cross of power voltage, and computing the absolute value ΔA(n)=IA(n)-A(n+1)I of the difference between the detected current peak time A(n) and the current peak time A(n+1) of a half wave after one cycle, and performs the integration of the absolute values ΔA(n) of the differences between the current peak times during a period (t0-α) to t0, and compares this integrated value W=W+ΔA(n) with the threshold, and determines that an arc current is generated when the integrated value W is over the threshold. <P>COPYRIGHT: (C)2004,JPO

Description

【００３７】
この積算値Ｗは、Ｗ＝Ｗ＋ΔＡ（ｎ）（但し、所定期間内での積算）でも表される。そしてマイコン３は積算値Ｗと閾値とを比較して、積算値Ｗが閾値を超えたときにアーク電流が発生したと判断する。
【００３８】
次に負荷電流またはアーク電流が流れた場合、各々についての判定までの手順を具体的に説明する。図８は、図７に示す一般家庭で使用される掃除機のスイッチをオンにしたときの負荷電流の各半波の電流ピーク時間Ａ（ｎ）の時間変化を示すもので、横軸は時間として電流波形の半波の数ｎとし、縦軸は電流ピーク時間Ａ（ｎ）としてある。具体的には、図７の負荷電流波形における電源電圧のゼロクロス時点から半波毎の電流ピーク時点Ｐ１〜Ｐ６までの電流ピーク時間Ａ（ｎ）は、図８中の点Ｐ１ａ〜Ｐ６ａに各々示される。
【００３９】
図９は図８の隣り合う周期の電流ピーク時間の差ΔＡ（ｎ）´の変動を示すもので、横軸は電流波形の半波の数ｎとし、縦軸は隣り合う周期の電流ピーク時間の差ΔＡ（ｎ）´としてある。具体的には、図９中の点Ｐ１１は図８中のＰ３ａ−Ｐ１ａ、点Ｐ１２はＰ４ａ−Ｐ２ａ、点Ｐ１３はＰ５ａ−Ｐ３ａを示す。そして、電流ピーク時間の差ΔＡ（ｎ）´が、互いに絶対値が等しい閾値Ｋ１（＝０．５ｍｓｅｃ），Ｋ２（＝−０．５ｍｓｅｃ）の外側である場合のみ、すなわち隣り合う周期の電流ピーク時間の差の絶対値ΔＡ（ｎ）が閾値０．５ｍｓｅｃを超えた場合のみ積算値Ｗ＝Ｗ＋ΔＡ（ｎ）の積算動作を行うが、この負荷電流の場合、電流ピーク時間の差ΔＡ（ｎ）´の全点は閾値Ｋ１，Ｋ２に挟まれた内側に入る、すなわち電流ピーク時間の差の絶対値ΔＡ（ｎ）が閾値０．５ｍｓｅｃ以下となるため、積算動作は行わない。なお、一部の負荷、使用状況を除いて負荷電流の電流ピーク時間の差ΔＡ（ｎ）´はこの閾値Ｋ１，Ｋ２内に入る。
【００４０】
次に、アーク電流が流れた場合として、図１０は、図５に示すアーク電流の各半波の電流ピーク時間Ａ（ｎ）の時間変化を示すもので、図８と同様に求められる。図１１は図１０の隣り合う周期の電流ピーク時間の差ΔＡ（ｎ）´の変動を示すもので、図９と同様に求められる。そして、電流ピーク時間の差ΔＡ（ｎ）´が、正負の閾値Ｋ１，Ｋ２を超える点、すなわち電流ピーク時間の差の絶対値ΔＡ（ｎ）が閾値０．５ｍｓｅｃを超える点Ｐ２１，Ｐ２３，Ｐ２６、Ｐ３０，Ｐ３２，Ｐ４６，Ｐ４８，Ｐ６１，Ｐ６６が出現している点がアーク電流の特徴であり、この電流ピーク時間の差の絶対値ΔＡ（ｎ）が閾値０．５ｍｓｅｃを超えたときに積算値Ｗ＝Ｗ＋ΔＡ（ｎ）の積算動作を行う。
【００４１】
次に［数１］で示す第１の積算方法以外の４種類の積算方法（第２〜第５の積算方法）について説明する。なお、アーク電流の各半波の電流ピーク時間Ａ（ｎ）の時間変化、及び隣り合う周期の電流ピーク時間の差ΔＡ（ｎ）´の変動は前述と同様に図１０、図１１と同様である。まず第２の積算方法は、隣り合う周期の電流ピーク時間の差の絶対値ΔＡ（ｎ）が閾値０．５ｍｓｅｃを超えた場合には｛ΔＡ（ｎ）−０．５ｍｓｅｃ｝を積算し（Ｗａ＝Ｗａ＋ΔＡ（ｎ）−０．５）、０．５ｍｓｅｃ以下の場合はそのときの積算値Ｗａから所定の値Ｌを減算する方法であり（Ｗａ＝Ｗａ−Ｌ、Ｗａ≧０）、ここではＬ＝０．０２とする。図１１の電流ピーク時間の差ΔＡ（ｎ）´に対応する本積算動作は図１２に示され、図１１の点Ｐ２３が負の閾値Ｋ２をＹ＝０．１ｍｓｅｃ超えたとき、図１２の点Ｐ７０に示すように、点Ｐ２３と閾値との差０．１を積算値Ｗａに積算する。次に点Ｐ２４，Ｐ２５は閾値Ｋ１，Ｋ２に挟まれた内側に入っているため、点Ｐ７０→Ｐ７１→Ｐ７２に示すように積算値ＷａからＬ＝０．０２を各々減算する。次に点Ｐ２６が正の閾値Ｋ１を超えた場合は、点Ｐ７２→Ｐ７３に示すように、点Ｐ２６と閾値との差を積算値Ｗａに積算する。そして、電流ピーク時間の差ΔＡ（ｎ）´が大きいとき、点Ｐ７４のように積算値Ｗａが一気にアーク検出閾値Ｋ３（＝０．２）を超えて、この時点でアーク電流検出と判定する。
【００４２】
次に第３の積算方法は、隣り合う周期の電流ピーク時間の差の絶対値ΔＡ（ｎ）が閾値０．５ｍｓｅｃ以上となった場合に１カウントアップし、０．５ｍｓｅｃ未満となった場合は所定の値Ｍを減算する方法で、ここではＭ＝０．２とする。図１１の電流ピーク時間の差ΔＡ（ｎ）´に対応する本積算動作は図１３に示され、図１１の点Ｐ２１が正の閾値Ｋ１以上となったとき、図１３の点Ｐ８０に示すように積算値Ｗｂの１カウントアップを行う。次に点Ｐ２２は閾値Ｋ１，Ｋ２に挟まれた内側に入っているため、点Ｐ８０→Ｐ８１に示すように積算値ＷｂからＭ＝０．２を減算する。次に点Ｐ２３が負の閾値Ｋ２以下となった場合は、点Ｐ８１→Ｐ８２に示すように積算値Ｗｂの１カウントアップを行う。そして、積算値Ｗｂがアーク検出閾値Ｋ４（＝３）を超えたときにアーク電流検出と判定する。この積算方法は、閾値以上になる電流ピーク時間の差の絶対値ΔＡ（ｎ）がある期間内に亘って続いた場合にアーク検出を行うものである。
【００４３】
また第４の積算方法として、所定期間内で、電流ピーク時間の差の絶対値ΔＡ（ｎ）が閾値０．５ｍｓｅｃを超えた場合には｛ΔＡ（ｎ）−０．５ｍｓｅｃ｝を積算する方法があり、所定期間内での積算値がアーク検出閾値を超えた場合にアーク電流検出と判定する。
【００４４】
さらに第５の積算方法として、所定期間内で、電流ピーク時間の差の絶対値ΔＡ（ｎ）が、閾値０．５ｍｓｅｃ以上になった場合に１カウントアップする方法があり、所定期間内での積算値がアーク検出閾値を超えた場合にアーク電流検出と判定する。
【００４５】
上記第２〜第５の積算方法のいずれも、電流ピーク時間の差の絶対値ΔＡ（ｎ）が閾値０．５ｍｓｅｃを超えた場合に積算を行うが、第２，第４の積算方法は電流ピーク時間の差の絶対値ΔＡ（ｎ）と閾値０．５ｍｓｅｃとの差を積算しており、この積算方法は、ΔＡ（ｎ）−０．５ｍｓｅｃが大きい場合に、積算値が一気に大きくなってアーク検出を行うので、検出時間を早くできるという特徴を有する。対して、第３，第５の積算方法は電流ピーク時間の差の絶対値ΔＡ（ｎ）が閾値０．５ｍｓｅｃを超えた場合に１カウントアップしており、この積算方法はマイコン３のプログラミング上計算が容易であり、メモリの使用量を抑えることができるという特徴を有する。
【００４６】
また積算期間に関しては、上記第４，第５の積算方法は常に最新の所定期間内での積算によってアーク電流を判定するのに対して、上記第２，第３の積算方法は電流ピーク時間の差の絶対値ΔＡ（ｎ）が閾値０．５ｍｓｅｃを超えた場合に積算し、超えない場合に減算するもので、最新の積算期間の情報をメモリに記憶する必要がないためマイコン３のメモリを削減できるが、この積算方法は上記第４，第５の積算方法の簡易方法として考案したもので、積算時間が長い場合、意図した積算が行われない場合がある。
【００４７】
インバータ式の電子レンジ等の電流波形は図１４に示すように、電流波形のピーク付近が平らである。この電流信号をマイコン３でＡ／Ｄ変換すると図１５のようになり、Ａ／Ｄ変換の分解能（図１５では１００μｓｅｃでサンプリングしている）によっては時間ｔ１〜ｔ２の範囲で同じデジタル値の電流ピーク値Ｉｐｅａｋ１０が複数点となることがある。この場合は、最も早く電流ピーク値Ｉｐｅａｋ１０が発生した時間ｔ１と、最も遅く電流ピーク値Ｉｐｅａｋ１０が発生した時間ｔ２との中間である時間ｔ３を電流ピーク時間Ａ（ｎ）とすることで、電流ピーク時間Ａ（ｎ）の検出精度を向上させることができる。
【００４８】
また図１６は、電流波形のピーク付近が平らでありながら、電流ピーク点のある部分がＡ／Ｄ変換の誤差によって本来の検出すべき位置よりずれた場合、その電流ピーク点の時間をそのまま電流ピーク時間Ａ（ｎ）とすると誤差が生じる。これを防ぐために、電流ピーク点から電流ピーク値Ｉｐｅａｋ１１に比べて非常に小さい値だけ下がった電流Ｉｐｅａｋ１１’であり、且つ電流ピーク値の発生時間より早い点Ｅ，電流ピーク値の発生時間より遅い点Ｆの時間ｔ４，ｔ５を検出し、時間ｔ４，ｔ５の中間である時間ｔ６を電流ピーク時間Ａ（ｎ）とすることで、電流ピーク時間Ａ（ｎ）の検出精度を向上させることができる。
【００４９】
さらに、アーク電流波形のピークは凸状であり、アーク電流波形では同じデジタル値の電流ピーク値が負荷電流と同じように続くことはないことから、同じデジタル値の電流ピーク値が一定数以上続く場合この波形は負荷特有の波形であると判断でき、負荷特有の波形である場合は、電流ピーク時間の差の絶対値ΔＡ（ｎ）を強制的にゼロ（ΔＡ（ｎ）＝０）とすることで、このような負荷特性による誤動作を防ぐことができる。
【００５０】
次に、負荷電流の力率が非常に悪い場合の電流波形と電源電圧波形とを図１７に示す。負荷電流の力率が非常に悪い場合には、電流ピーク点が電圧ゼロクロス時点ｔ７，ｔ８の近傍となることがある。電流ピーク値は電圧ゼロクロス時点ｔ７−ｔ８間で検出するので、電流ピーク点がこの時点ｔ７−ｔ８間から外れると電流ピーク時間Ａ（ｎ）を誤検出する場合がある。そこで、電流ピーク点の検出精度を考慮して、電圧ゼロクロス時点ｔ７，ｔ８の近傍の範囲Ｔ１（例えば位相０°〜１０°），Ｔ２（例えば位相１７０°〜１８０°）内に電流ピーク点が存在する場合は、電流ピーク時間の差の絶対値ΔＡ（ｎ）を強制的にゼロ（ΔＡ（ｎ）＝０）とすることで、このような負荷による誤動作を防ぐことができる。
【００５１】
また、電源を投入して負荷電流が流れ始めた直後や、負荷機器を使用中に使用モードを切り換えたとき、電流ピーク時間Ａ（ｎ）が変動する場合がある。この場合の電流ピーク時間の差の絶対値ΔＡ（ｎ）は、アーク電流発生時の電流ピーク時間の差の絶対値ΔＡ（ｎ）よりも大きく、変動の継続時間は数周期と短い。したがって、電流ピーク時間の差の絶対値ΔＡ（ｎ）が閾値より大きい場合、電流ピーク時間の差の絶対値ΔＡ（ｎ）を強制的にゼロ（ΔＡ（ｎ）＝０）とすることで、負荷機器の電源投入や、使用モードの切り換えによる誤動作を防ぐことができる。
【００５２】
次に、インバータ式の洗濯機等の場合、電流ピーク時間の差の絶対値ΔＡ（ｎ）は大きく、誤動作を引き起こす恐れがある。以下この誤動作を防止する方法について説明する。図１８はインバータ式の洗濯機の電流ピーク時間の差ΔＡ（ｎ）´である。この変動は負荷機器の中でも大きく、アーク電流発生時の変動の大きさに匹敵する。
【００５３】
ここで図１９は、インバータ式の洗濯機の負荷電流について、隣り合う周期の電流ピーク値の差｛Ｉｐｅａｋ（ｎ＋１）−Ｉｐｅａｋ（ｎ）｝と、電流ピーク時間の差ΔＡ（ｎ）´との相関を表したものであり、図２０はインバータ式の洗濯機のアーク電流について図１９と同様の相関を表したものである。インバータ式の洗濯機の負荷電流は一般的に原点に近い部分に集まり、図１９では原点を斜めに横切る範囲Ｑ１内に収まっており、隣り合う周期の電流ピーク値の差の変動は大きいものの、電流ピーク値の差が小さい領域（例えば−５Ａ〜５Ａ）ではピーク時間の差の変動は比較的小さく、電流ピーク値の差が−５Ａ〜５Ａで且つピーク時間の差が５００μｓｅｃ以上あるいは−５００μｓｅｃ以下の範囲Ｑ２内には分布がないことが特徴である。対してアーク電流は、その電流値及び電流ピークの時間が半波毎に不規則に変動する。よって図２０に示すように、その分布は負荷電流に比べて広い範囲Ｑ３に広がるのが特徴であり、電流ピーク値の差が小さい領域でもピーク時間の差の変動は大きいものとなっている。したがって、電流ピーク値の差の絶対値が閾値よりも大きい領域Ｑ４（図１９の斜線部，５Ａ以上及び−５Ａ以下）に存在する場合は、電流ピーク時間の差の絶対値ΔＡ（ｎ）を強制的にゼロ（ΔＡ（ｎ）＝０）とすることで、検出対象から除外してインバータ式の洗濯機での誤動作を防ぐことができる。
【００５４】
さらに、一般的な負荷での誤動作対策を以下説明する。アーク電流の各半波のピーク電流値の変動は負荷電流のピーク電流の変動に比べて大きいので、積算値Ｗが閾値を超え、且つ交流電流の半波毎の電流ピーク値Ｉｐｅａｋ（ｎ）を検出し、検出した電流ピーク値Ｉｐｅａｋ（ｎ）と１周期後の半波の電流ピーク値Ｉｐｅａｋ（ｎ＋１）との差の絶対値ΔＩｐｅａｋ（ｎ）＝｜Ｉｐｅａｋ（ｎ＋１）−Ｉｐｅａｋ（ｎ）｜を閾値と比較し、電流差の絶対値ΔＩｐｅａｋ（ｎ）が閾値より大きい状態が所定の回数連続して続いたときにアーク電流が発生したと判断すれば、電流ピーク点の位相の変動と電流ピーク値の変動とによってアーク電流検出の判定を行うので、誤動作をより少なくすることができる。
【００５５】
また別の対策を以下説明する。アーク電流の電流ピーク時間Ａ（ｎ）は不規則に変動するので、電流ピーク時間の差の絶対値ΔＡ（ｎ）もある範囲でばらつく。一方、負荷電流の電流ピーク時間の差の絶対値ΔＡ（ｎ）は、負荷への電源投入時、使用モードの変更時や、インバータ式の洗濯機等を除いて、電流ピーク時間の差の絶対値ΔＡ（ｎ）は比較的小さく、所定の範囲内に収まる。そこで、電流ピーク時間の差の絶対値ΔＡ（ｎ）を、電流ピーク時間の差の絶対値ΔＡ（ｎ）によって区切られた小区分毎に積算する。例えば、小区分をＷ１，Ｗ２，Ｗ３．．．とし、ｐ＜ΔＡ（ｎ）≦ｑであれば小区分Ｗ１で積算し、ｑ＜ΔＡ（ｎ）≦ｒであれば小区分Ｗ２で積算し、．．．というように各小区分Ｗ１，Ｗ２，Ｗ３．．．毎に積算して、各小区分毎に設定した閾値と比較する。
【００５６】
上記積算方法を用いると、アーク電流は電流ピーク時間の差の絶対値ΔＡ（ｎ）がばらつくので、複数の小区間においてまんべんなく積算される。対して負荷電流の場合は、特定の小区間のみにおいて積算される。したがって、予め設定した複数の小区分において、小区分毎の積算値が閾値を超えた場合にアーク電流検出と判定することで、負荷電流に対する誤動作を低減することができる。
【００５７】
（実施形態２）
図２１は、アーク電流のピーク位相として、半波毎の電流ピーク点から次の半波の電流ピーク点までの時間（電流ピーク時間）Ｂ（ｎ）（正の半波：ｎ＝１，２，３，４，５，．．．、負の半波：ｎ＝１´，２´，３´，４´，５´，．．．）を検出し、検出した電流ピーク時間Ｂ（ｎ）と１周期後に検出した半波の電流ピーク時間Ｂ（ｎ＋１）との差（隣り合う周期の電流ピーク時間の差）の絶対値ΔＢ（ｎ）＝｜Ｂ（ｎ）−Ｂ（ｎ＋１）｜を算出して、隣り合う周期の電流ピーク時間の差の絶対値ΔＢ（ｎ）に対して所定期間（ｔ０−α）〜ｔ０間で［数２］で表される積算を行うものである。
【００５８】
【数２】

【００５９】
この積算値Ｗは、Ｗ＝Ｗ＋ΔＢ（ｎ）（但し、所定期間内での積算）でも表される。そして積算値Ｗと閾値とを比較して、積算値Ｗが閾値を超えたときにアーク電流が発生したと判断する。
【００６０】
このアーク電流判別方法は、実施形態１のような電圧のゼロクロス時点の検出が不要であり、電流波形のみの検出によってアーク電流の判別を行うことができ、電流ピーク点の位相検出方法以外については実施形態１と同様に行うことができる。
【００６１】
（実施形態３）
図２２は、アーク電流のピーク位相として、半波毎の電流ピーク点から次の１周期後の半波の電流ピーク点までの時間（電流ピーク時間）Ｃ（ｎ）（正の半波：ｎ＝１，２，３，４，５，．．．、負の半波：ｎ＝１´，２´，３´，４´，５´，．．．）を検出し、検出した電流ピーク時間Ｃ（ｎ）と１周期後に検出した半波の電流ピーク時間Ｃ（ｎ＋１）との差（隣り合う周期の電流ピーク時間の差）の絶対値ΔＣ（ｎ）＝｜Ｃ（ｎ）−Ｃ（ｎ＋１）｜を算出して、隣り合う周期の電流ピーク時間の差の絶対値ΔＣ（ｎ）に対して所定期間（ｔ０−α）〜ｔ０間で［数３］で表される積算を行うものである。
【００６２】
【数３】

【００６３】
この積算値Ｗは、Ｗ＝Ｗ＋ΔＣ（ｎ）（但し、所定期間内での積算）でも表される。そして積算値Ｗと閾値とを比較して、積算値Ｗが閾値を超えたときにアーク電流が発生したと判断する。
【００６４】
このアーク電流判別方法は、ドライヤーの弱モードで出現する半波整流した電流波形のように正側と負側とで異なる電流波形の場合に有効であり、電流ピーク点の位相検出方法以外については実施形態１と同様に行うことができる。
【００６５】
ここで、一般家庭では複数の負荷が同時に使用されることが普通であり、この一般家庭の電路を流れる電流波形は、各負荷電流の合成（和）となり、このような状況でもアーク電流が流れた場合には検出する必要がある。上記実施形態１〜３においては、このような場合でも各半波の電流ピーク時間が同様に変動するので、アーク電流の検出が可能である。
【００６６】
また、プラグのトラッキング現象は、プラグの栓刃間で微少な電流が流れ、絶縁劣化の進行によって徐々に電流が大きくなり、最終的には短絡に至る。この現象は比較的小さい電流（２〜３Ａ程度）でもアークを発生し火災に至るため、なるべく小さいアーク電流で検出して電路を遮断する必要がある。上記実施形態１〜３においては電流ピーク時間を検出するので、２〜３Ａ程度の小さい電流値についても電流ピーク時間の検出が可能であり、プラグのトラッキング現象を早期に検出することができる。
【００６７】
上記実施形態１〜３においては、電流ピーク時間の変動を検出して、アーク電流と負荷電流とを識別する方法、及びその装置について述べた。しかし、アーク電流の性質からすれば、各周期毎のアーク電流が流れ始める時間や電流が流れなくなる時間等も同様に変動する性質がある。したがって上記実施形態１〜３で述べた電流ピーク時間の変動以外にも、電流の始点、終点の時間を検出することによってもアーク電流と負荷電流とを識別することができる。
【００６８】
また、検出した電流ピーク時間Ａ（ｎ）、Ｂ（ｎ）、Ｃ（ｎ）と１周期後の半波の電流ピーク時間Ａ（ｎ＋１）、Ｂ（ｎ＋１）、Ｃ（ｎ＋１）との差の絶対値を算出して、この電流ピーク時間の差の絶対値を変数とする関数を積算しているが、電流ピーク時間の差は検出した電流ピーク時間と所定の周期後に検出した半波の電流ピーク時間との差でよく、例えば検出した電流ピーク時間Ａ（ｎ）、Ｂ（ｎ）、Ｃ（ｎ）と半周期後に検出した半波の電流ピーク時間Ａ（ｎ）´、Ｂ（ｎ）´、Ｃ（ｎ）´との差の絶対値であってもよい。
【００６９】
【発明の効果】
請求項１の発明は、交流電源から交流負荷回路に供給される交流電流の半波毎の電流ピーク点の位相を検出し、検出した電流ピーク点の位相と所定周期後に検出した半波の電流ピーク点の位相との差の絶対値を算出して、前記位相差の絶対値を変数とする関数を積算し、前記積算値と閾値とを比較して、前記積算値が閾値を超えたときにアーク電流が発生したと判断するので、正常な負荷電流では誤検出せず、芯線間の短絡によるアーク短絡現象や、芯線の切断が原因によって発生する直列アーク現象による交流回路の異常電流を検出できるという効果がある。
【００７０】
請求項２の発明は、請求項１において、前記交流電流の電流ピーク点の位相は、電源電圧のゼロクロス時点から半波毎の電流ピーク点までの時間として検出されるので、交流電流の電流ピーク点の位相の具体的な検出方法を提供できるという効果がある。
【００７１】
請求項３の発明は、請求項１において、前記交流電流の電流ピーク点の位相は、半波毎の電流ピーク点から次の半波の電流ピーク点までの時間として検出されるので、請求項２のような電圧のゼロクロス時点の検出が不要であり、電流波形のみの検出によってアーク電流検出の判定を行うことができるという効果がある。
【００７２】
請求項４の発明は、請求項１において、前記交流電流の電流ピーク点の位相は、半波毎の電流ピーク点から１周期後の半波の電流ピーク点までの時間として検出されるので、ドライヤーの弱モードで出現する半波整流した電流波形のように正側と負側とで異なる電流波形の場合に有効であるという効果がある。
【００７３】
請求項５の発明は、請求項１乃至４いずれかにおいて、前記積算動作は、前記位相差の絶対値を変数とする関数を所定期間内で積算するので、最新の期間の情報によってアーク電流検出の判定を行うことができるという効果がある。
【００７４】
請求項６の発明は、請求項２乃至５いずれかにおいて、前記交流電流を所定の周期でサンプリングしてデジタル値に変換してから電流ピーク点の時間を検出し、同じデジタル値の電流ピーク値が半波内で複数個検出された場合は、最も早く電流ピーク値が発生した時間と最も遅く電流ピーク値が発生した時間との中間を電流ピーク点の時間とするので、インバータ式の電子レンジ等のようにピーク付近が平らな電流波形に対して、電流ピーク点の時間の検出精度を向上させることができるという効果がある。
【００７５】
請求項７の発明は、請求項２乃至５いずれかにおいて、前記交流電流を所定の周期でサンプリングしてデジタル値に変換してから、電流ピーク値に対して微少な値を電流ピーク値から減算した電流値が発生する時間で、且つ電流ピーク値の発生時間より早い時間と遅い時間との中間を電流ピーク点の時間とするので、ピーク付近が平らな電流波形で、電流ピーク点のある部分がＡ／Ｄ変換の誤差によって本来の検出すべき位置よりずれた場合にでも、電流ピーク点の時間の検出精度を向上させることができるという効果がある。
【００７６】
請求項８の発明は、請求項６において、同じデジタル値の電流ピーク値が半波内で所定のサンプリング個数以上検出された場合、前記位相差の絶対値を変数とする関数をゼロに設定するので、負荷特性による誤動作を防止することができるという効果がある。
【００７７】
請求項９の発明は、請求項２乃至７いずれかにおいて、電流ピーク点の時間が所定の範囲外で検出された場合、前記位相差の絶対値を変数とする関数をゼロに設定するので、負荷電流の力率が悪い場合に電流ピーク点の時間を誤検出することを阻止して、負荷特性による誤動作を防止することができるという効果がある。
【００７８】
請求項１０の発明は、請求項１乃至７いずれかにおいて、前記位相差の絶対値が閾値を超えた場合、前記位相差の絶対値を変数とする関数をゼロに設定するので、負荷への電源投入や、使用モードの変更による誤動作を防止することができるという効果がある。
【００７９】
請求項１１の発明は、請求項１乃至７いずれかにおいて、前記交流電流の半波毎の電流ピーク点の電流値を検出し、検出した電流ピーク点の電流値と１周期後に検出した半波の電流ピーク点の電流値との差の絶対値を算出して、前記電流差の絶対値と閾値とを比較し、前記電流差の絶対値が閾値より大きい場合、前記位相差の絶対値を変数とする関数をゼロに設定するので、インバータ式の洗濯機等のように電流ピーク点の時間変動が大きい負荷に対して、誤動作を防止することができるという効果がある。
【００８０】
請求項１２の発明は、請求項１乃至４いずれかにおいて、前記積算値は、前記位相差の絶対値が閾値を超えた場合、前記位相差の絶対値から所定値を引いた値を所定期間内で積算した値であるので、最新期間の情報によってアーク電流検出の判定を行うことができ、電流ピーク点の位相の変動が大きい場合には検出時間が早くなるという効果がある。
【００８１】
請求項１３の発明は、請求項１乃至４いずれかにおいて、前記積算値は、前記位相差の絶対値が閾値を超えた場合、所定期間内でカウントアップした値であるので、最新期間の情報によってアーク電流検出の判定を行うことができ、さらにマイコンのプログラミング上計算が容易であり、メモリの使用量を抑えることができるという効果がある。
【００８２】
請求項１４の発明は、請求項１乃至４いずれかにおいて、前記積算値は、前記位相差の絶対値が閾値を超えた場合、その度に前記位相差の絶対値から第１の所定値を減算した値を積算し、前記位相差の絶対値が閾値を超えない場合、その度に前記積算値から第２の所定値を減算した値であるので、最新期間の情報をメモリに確保する必要がないためマイコンのメモリを削減することができ、さらに電流ピーク点の位相の変動が大きい場合には検出時間が早くなるという効果がある。
【００８３】
請求項１５の発明は、請求項１乃至４いずれかにおいて、前記積算値は、前記位相差の絶対値が閾値を超えた場合、その度にカウントアップし、前記位相差の絶対値が閾値を超えない場合、その度に所定値を減算した値であるので、最新期間の情報をメモリに確保する必要がないためマイコンのメモリを削減することができ、さらにマイコンのプログラミング上計算が容易であり、メモリの使用量をさらに抑えることができるという効果がある。
【００８４】
請求項１６の発明は、請求項１乃至７いずれかにおいて、前記積算値が閾値を超えたとき、且つ前記交流電流の半波毎の電流ピーク点の電流値を検出し、検出した電流ピーク点の電流値と１周期後に検出した半波の電流ピーク点の電流値との差の絶対値を算出して、前記電流差の絶対値と閾値とを比較し、前記電流差の絶対値が閾値より大きい状態が所定の回数連続して続いたときにアーク電流が発生したと判断するので、電流ピーク点の位相の変動と電流ピーク値の変動とによってアーク電流検出の判定を行い、誤動作をより少なくすることができるという効果がある。
【００８５】
請求項１７の発明は、請求項１において、前記位相差の絶対値を変数とする関数は前記位相差の絶対値によって区切られた小区間毎に積算され、小区間毎の積算値は小区間毎に設定された閾値と比較されて、所定の小区間で積算値が閾値を超えたときにアーク電流が発生したと判断するので、誤動作をより少なくすることができるという効果がある。
【００８６】
請求項１８の発明は、交流電源から交流負荷回路に供給される交流電流の半波毎の電流ピーク点の位相を検出する手段と、検出した電流ピーク点の位相と所定周期後に検出した半波の電流ピーク点の位相との差の絶対値を算出する手段と、前記位相差の絶対値を変数とする関数を積算する手段と、前記積算値と閾値とを比較する手段と、前記積算値が閾値を超えたときにアーク電流が発生したと判断する手段とを備えるので、正常な負荷電流では誤検出せず、芯線間の短絡によるアーク短絡現象や、芯線の切断による直列アーク現象による交流回路の異常電流を検出する装置を提供することができるという効果がある。
【図面の簡単な説明】
【図１】本発明の電流ピーク点の位相を検出する第１の方法を示す図である。
【図２】同上の回路構成を示す図である。
【図３】同上の絶対値に変換された電流信号、電圧信号を示す図である。
【図４】同上の絶対値に変換されない電流信号、電圧信号を示す図である。
【図５】アーク電流波形を示す図である。
【図６】アーク電流波形の拡大図である。
【図７】掃除機の負荷電流波形を示す図である。
【図８】掃除機の負荷電流の電流ピーク時間の時間変化を示す図である。
【図９】図８の隣り合う周期の電流ピーク時間の差の時間変化を示す図である。
【図１０】アーク電流の電流ピーク時間の時間変化を示す図である。
【図１１】図１０の隣り合う周期の電流ピーク時間の差の時間変化を示す図である。
【図１２】図１１の電流ピーク時間の差の第１の積算方法を示す図である。
【図１３】図１１の電流ピーク時間の差の第２の積算方法を示す図である。
【図１４】インバータ式電子レンジの電流波形を示す図である。
【図１５】本発明の電流ピーク時間の第１の検出方法を示す図である。
【図１６】同上の電流ピーク時間の第２の検出方法を示す図である。
【図１７】同上の電流ピーク時間の検出範囲を示す図である。
【図１８】インバータ式洗濯機の隣り合う周期の電流ピーク時間の差の時間変化を示す図である。
【図１９】インバータ式洗濯機の負荷電流の電流ピーク差と電流ピーク時間差との相関を示す図である。
【図２０】アーク電流の電流ピーク差と電流ピーク時間差との相関を示す図である。
【図２１】本発明の電流ピーク点の位相を検出する第２の方法を示す図である。
【図２２】同上の電流ピーク点の位相を検出する第３の方法を示す図である。
【符号の説明】
Ａ１，Ａ１´，Ａ２，Ａ２´，．．． 電流ピーク時間
Ｉｐｅａｋ１，Ｉｐｅａｋ１´，．．． 電流ピーク値[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to an arc current discrimination method and an arc current discrimination device for detecting an arc occurrence in an AC load circuit and preventing a fire or the like, and particularly relates to a residential electric circuit including an extension cord, a cord with a fixture, and an outlet plug. It is used for protection equipment.
[0002]
[Prior art]
Conventionally, protection of a cord and a load device by an overcurrent or a short-circuit current has been performed by a circuit breaker using a bimetal or an instantaneous interruption electromagnetic coil. Generally, an instantaneous interruption type circuit breaker is set to be interrupted when a current of 10 times or more the rated current of the circuit breaker flows. However, in the case of an arc short-circuit in which the core wires come into contact due to deterioration of the insulation of the cord, the short-circuit current does not flow to the operating current of the instantaneous circuit breaker, or it is intermittent rather than continuous like the load current. In some cases, a current could occur, causing a fire without the instantaneous circuit breaker operating.
[0003]
In order to compensate for such a drawback, a circuit breaker for detecting a current waveform specific to an arc has been proposed. This circuit breaker detects an arc-specific current waveform as a load current in a current region where an instantaneous circuit breaker cannot detect, such as when the core wires of a cord are in contact with each other, by an electronic circuit. However, a load current waveform may be erroneously recognized as an arc short-circuit current waveform, and a malfunction may occur with a general load current waveform.
[0004]
Here, as a typical phenomenon leading to a fire due to a short circuit, a short circuit occurs between the core wires and a short-circuit current flows.At a short-circuit point, the core wire is melted by a large current and an arc discharge occurs. Because of the high temperature, a high-temperature molten material such as a core wire is scattered, and the surrounding objects are ignited to cause a fire. The arc short-circuit caused by the fusion of the core wires occurs not only in the power cord and the extension cord, but also in the inside of the load device and in the indoor wiring. Furthermore, a minute current may continue to flow between the outlet plug blades due to insulation deterioration, and a tracking phenomenon that eventually causes an arc short circuit may occur.
[0005]
In addition, when one of the core wires in the pair breaks due to some stress and the ends of the broken core wires come into contact with each other with some force, when a load is connected, a load current flows, and the core wire ends. Then, arc discharge occurs. This arc generation phenomenon is called a series arc because the current path and the load are in series, and a fire may occur when the series arc is generated.
[0006]
Therefore, for example, there has been proposed a method of detecting a tracking short circuit based on a current variation calculated by taking a difference between adjacent current values among current values extracted for each unit time. (For example, refer to Patent Document 1).
[0007]
[Patent Document 1]
JP-A-2001-103657 (page 4, left column, line 48 to page 5, left column, line 32, FIGS. 2 to 4)
[0008]
[Problems to be solved by the invention]
However, in the above-mentioned conventional technology, it was not possible to detect an arc short-circuit phenomenon occurring in an AC circuit without malfunction, or to detect a series arc.
[0009]
The present invention has been made in view of the above circumstances, and has as its object the purpose of detecting an AC circuit due to an arc short-circuit phenomenon due to a short circuit between core wires and a series arc phenomenon due to a cut of a core wire without erroneous detection at a normal load current. An object of the present invention is to provide an arc current determination method and an arc current determination device capable of detecting an abnormal current.
[0010]
[Means for Solving the Problems]
The invention according to claim 1 detects a phase of a current peak point for each half-wave of an alternating current supplied from an AC power supply to an AC load circuit, and detects a phase of the detected current peak point and a half-wave current detected after a predetermined period. When the absolute value of the difference from the phase of the peak point is calculated, a function using the absolute value of the phase difference as a variable is integrated, the integrated value is compared with a threshold, and the integrated value exceeds the threshold. It is determined that an arc current has occurred.
[0011]
A second aspect of the present invention is characterized in that, in the first aspect, the phase of the current peak point of the alternating current is detected as a time from a zero crossing point of the power supply voltage to a current peak point for each half wave.
[0012]
According to a third aspect of the present invention, in the first aspect, the phase of the current peak point of the alternating current is detected as a time from the current peak point of each half-wave to the current peak point of the next half-wave. I do.
[0013]
According to a fourth aspect of the present invention, in the first aspect, the phase of the current peak point of the alternating current is detected as a time from a current peak point of each half-wave to a current peak point of a half-wave one cycle later. Features.
[0014]
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the integrating operation integrates a function using the absolute value of the phase difference as a variable within a predetermined period.
[0015]
According to a sixth aspect of the present invention, in accordance with any one of the second to fifth aspects, the AC current is sampled at a predetermined cycle and converted into a digital value, and then the time of the current peak point is detected. Is detected in a half-wave, the time between the earliest occurrence of the current peak value and the latest occurrence of the current peak value is defined as the time of the current peak point.
[0016]
According to a seventh aspect of the present invention, in any one of the second to fifth aspects, the AC current is sampled at a predetermined cycle and converted into a digital value, and then a minute value with respect to the current peak value is subtracted from the current peak value. The time when the current value is generated and the time between the time earlier and the time later than the time when the current peak value is generated is set as the time of the current peak point.
[0017]
According to an eighth aspect of the present invention, in the sixth aspect, when a current peak value of the same digital value is detected by a predetermined number of samples or more in a half wave, a function using the absolute value of the phase difference as a variable is set to zero. It is characterized by the following.
[0018]
According to a ninth aspect of the present invention, in any one of the second to seventh aspects, when the time of the current peak point is detected out of a predetermined range, the function using the absolute value of the phase difference as a variable is set to zero. Features.
[0019]
According to a tenth aspect of the present invention, in any one of the first to seventh aspects, when the absolute value of the phase difference exceeds a threshold value, a function using the absolute value of the phase difference as a variable is set to zero. .
[0020]
According to an eleventh aspect of the present invention, in any one of the first to seventh aspects, a current value at a current peak point for each half-wave of the alternating current is detected, and the half-wave detected one cycle after the detected current value at the current peak point. The absolute value of the difference between the current value of the current peak point and the absolute value of the current difference is compared with a threshold value.If the absolute value of the current difference is greater than the threshold value, the absolute value of the phase difference is calculated. It is characterized in that a function to be a variable is set to zero.
[0021]
According to a twelfth aspect of the present invention, in any one of the first to fourth aspects, when the absolute value of the phase difference exceeds a threshold value, the integrated value is a value obtained by subtracting a predetermined value from the absolute value of the phase difference for a predetermined period. It is characterized in that it is a value integrated within.
[0022]
According to a thirteenth aspect of the present invention, in any one of the first to fourth aspects, the integrated value is a value counted up within a predetermined period when the absolute value of the phase difference exceeds a threshold value.
[0023]
According to a fourteenth aspect of the present invention, in any one of the first to fourth aspects, when the absolute value of the phase difference exceeds a threshold value, the integrated value is a first predetermined value from the absolute value of the phase difference each time. The subtracted values are integrated, and each time the absolute value of the phase difference does not exceed a threshold value, a value obtained by subtracting a second predetermined value from the integrated value is used.
[0024]
In the invention according to claim 15, according to any one of claims 1 to 4, the integrated value is counted up each time the absolute value of the phase difference exceeds a threshold value, and the absolute value of the phase difference is set to a threshold value. When the value does not exceed the predetermined value, a predetermined value is subtracted each time.
[0025]
According to a sixteenth aspect of the present invention, in any one of the first to seventh aspects, when the integrated value exceeds a threshold value, and a current value at a current peak point for each half-wave of the alternating current is detected, and the detected current peak point is detected. The absolute value of the difference between the current value of the current difference and the current value of the half-wave current peak point detected one cycle later is calculated, and the absolute value of the current difference is compared with a threshold value. It is characterized in that it is determined that an arc current has occurred when the larger state continues for a predetermined number of times.
[0026]
According to a seventeenth aspect, in the first aspect, the function using the absolute value of the phase difference as a variable is integrated for each small section divided by the absolute value of the phase difference, and the integrated value for each small section is a small section. It is characterized in that it is compared with a threshold set for each time, and when the integrated value exceeds the threshold in a predetermined small section, it is determined that an arc current has occurred.
[0027]
The invention according to claim 18 is means for detecting the phase of the current peak point for each half-wave of the alternating current supplied from the AC power supply to the AC load circuit, and detecting the phase of the detected current peak point and the half-wave detected after a predetermined period. Means for calculating the absolute value of the difference from the phase of the current peak point, means for integrating a function using the absolute value of the phase difference as a variable, means for comparing the integrated value with a threshold, and the integrated value Means for determining that an arc current has occurred when the threshold value exceeds a threshold value.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0029]
(Embodiment 1)
FIG. 2 shows a circuit configuration example of an embodiment of the present invention. The current detection circuit 1 detects an AC current supplied from an AC power supply of 100 Vrms to an AC load circuit, and the voltage detection circuit 2 detects a power supply voltage. And the microcomputer 3. The current detection circuit 1 includes a CT 10 that outputs a current corresponding to a detected value, a load resistor 11 that converts an output current of the CT 10 into a voltage, a filter 12 that passes only a necessary band, and an amplification circuit 13 that amplifies a signal. And an absolute value circuit 14 for outputting the absolute value of the input as a current signal S1.
[0030]
The voltage detection circuit 2 includes a resistance voltage dividing circuit 20 for dividing a power supply voltage, a differential input circuit 21, a filter 22 for passing only a necessary band, and a voltage converted into a digital pulse by comparing the input with a zero level. A zero-cross comparator 23 that outputs a signal S2.
[0031]
The microcomputer 3 performs A / D conversion of the current signal S1 output from the current detection circuit 1 at a predetermined sampling frequency (for example, 100 μsec), captures the converted signal, and converts the voltage signal S2 converted into a digital pulse by the zero-cross comparator 23 of the voltage detection circuit 2. Take in from I / O port.
[0032]
FIG. 3 shows a current signal S1 and a voltage signal S2 captured by the microcomputer 3, and the reason why the current signal S1 is converted into an absolute value is to increase the resolution of A / D conversion. If the resolution is sufficient, the absolute value circuit 14 is replaced with an adder circuit, and the microcomputer 3 A / D converts the current signal S1 'obtained by superimposing DC on the AC waveform detected by CT10 as shown in FIG. Good. The voltage signal S2 alternates between a high level and a low level every time the polarity of the power supply voltage is inverted.
[0033]
In the microcomputer 3, the current signal S1 and the voltage signal S2 are analyzed by a predetermined program, and when it is determined that the current is an arc current, an accident detection signal S3 is output from the voltage output port.
[0034]
Here, FIG. 5 is a current waveform of a series arc reproduced in an experiment, and FIG. 6 is an enlarged view of a square frame M in FIG. 5, showing an arc current waveform and a power supply voltage (AC 100 V) waveform. FIG. 7 shows a load current waveform when a vacuum cleaner used in a general household is turned on. The characteristic feature of the arc current is that the current path and the resistance at the insulation-deteriorated portion change irregularly, so that the current peak value of each half-wave and the phase of the current peak (peak phase) change irregularly. On the other hand, since the load current is controlled by the load device, the current peak value and the peak phase do not vary irregularly and largely as compared with the arc current.
[0035]
Therefore, in the present embodiment, attention is paid to the fact that the peak phase of the arc current fluctuates irregularly for each half-wave, and the arc current and the load current are distinguished from each other. As the peak phase of the current, current peak values Ipeak1, Ipeak2,. . . And negative half-wave current peak values Ipeak1 ', Ipeak2',. . . Each current peak time A (n) (positive half-wave: n = 1, 2, 3, 4, 5,..., Negative half-wave: n = 1 ′, 2 ′, 3 ′) , 4 ′, 5 ′,...), And the difference between the detected current peak time A (n) and the half-wave current peak time A (n + 1) detected one cycle later (the current peaks of adjacent cycles). Time difference) ΔA (n) ′ = A (n) −A (n + 1) absolute value ΔA (n) = | A (n) −A (n + 1) | The integration represented by [Equation 1] is performed for the absolute value ΔA (n) of the difference between the predetermined period (t0−α) and t0.
[0036]
(Equation 1)

[0037]
This integrated value W is also represented by W = W + ΔA (n) (however, integrated within a predetermined period). Then, the microcomputer 3 compares the integrated value W with the threshold value, and determines that an arc current has occurred when the integrated value W exceeds the threshold value.
[0038]
Next, when the load current or the arc current flows, the procedure up to the determination for each of them will be specifically described. FIG. 8 shows the time change of the current peak time A (n) of each half-wave of the load current when the switch of the vacuum cleaner used in a general home shown in FIG. 7 is turned on. Is the number n of half-waves of the current waveform, and the vertical axis is the current peak time A (n). Specifically, the current peak times A (n) from the zero crossing point of the power supply voltage to the current peak points P1 to P6 for each half-wave in the load current waveform of FIG. 7 are shown at points P1a to P6a in FIG. It is.
[0039]
FIG. 9 shows the variation of the difference ΔA (n) ′ between the current peak times of the adjacent cycles in FIG. 8. The horizontal axis represents the number n of the half-waves of the current waveform, and the vertical axis represents the current peak time of the adjacent cycles. ΔA (n) ′. Specifically, point P11 in FIG. 9 indicates P3a-P1a in FIG. 8, point P12 indicates P4a-P2a, and point P13 indicates P5a-P3a. Only when the current peak time difference ΔA (n) ′ is outside the threshold values K1 (= 0.5 msec) and K2 (= −0.5 msec) having the same absolute value, that is, the current peaks of adjacent cycles The integration operation of the integrated value W = W + ΔA (n) is performed only when the absolute value ΔA (n) of the time difference exceeds the threshold value 0.5 msec. In the case of this load current, the difference ΔA (n) of the current peak time Since all the points of 'enter the area between the thresholds K1 and K2, that is, since the absolute value ΔA (n) of the difference between the current peak times is equal to or smaller than 0.5 msec, the integration operation is not performed. It should be noted that the difference ΔA (n) ′ between the current peak times of the load currents falls within the thresholds K1 and K2 except for some loads and usage conditions.
[0040]
Next, assuming that an arc current flows, FIG. 10 shows the time change of the current peak time A (n) of each half-wave of the arc current shown in FIG. 5, which is obtained in the same manner as FIG. FIG. 11 shows the variation of the difference ΔA (n) ′ between the current peak times of the adjacent cycles in FIG. 10, which is obtained in the same manner as in FIG. Then, the points P21, P23, and P26 where the difference ΔA (n) ′ between the current peak times exceeds the positive and negative threshold values K1 and K2, that is, the points P21, P23, and P26 where the absolute value ΔA (n) of the difference between the current peak times exceeds the threshold value 0.5 msec. , P30, P32, P46, P48, P61, and P66 are features of the arc current, and are integrated when the absolute value ΔA (n) of the difference between the current peak times exceeds the threshold value 0.5 msec. The integration operation of the value W = W + ΔA (n) is performed.
[0041]
Next, four types of integration methods (second to fifth integration methods) other than the first integration method shown in [Equation 1] will be described. The time change of the current peak time A (n) of each half-wave of the arc current and the change of the difference ΔA (n) ′ between the current peak times of the adjacent cycles are the same as those in FIGS. is there. First, the second integration method integrates {ΔA (n) −0.5 msec} when the absolute value ΔA (n) of the difference between the current peak times of adjacent cycles exceeds the threshold value 0.5 msec (Wa). = Wa + ΔA (n) -0.5), a method of subtracting a predetermined value L from the integrated value Wa at that time when it is 0.5 msec or less (Wa = Wa−L, Wa ≧ 0), and here L = 0.02. The main integration operation corresponding to the current peak time difference ΔA (n) ′ in FIG. 11 is shown in FIG. 12, and when the point P23 in FIG. 11 exceeds the negative threshold value K2 by Y = 0.1 msec, the point in FIG. As shown in P70, the difference 0.1 between the point P23 and the threshold value is added to the integrated value Wa. Next, since points P24 and P25 are on the inside between thresholds K1 and K2, L = 0.02 is subtracted from integrated value Wa as shown by points P70 → P71 → P72. Next, when the point P26 exceeds the positive threshold value K1, the difference between the point P26 and the threshold value is integrated into the integrated value Wa, as shown from point P72 to point P73. When the difference ΔA (n) ′ between the current peak times is large, the integrated value Wa exceeds the arc detection threshold value K3 (= 0.2) at a stroke as at a point P74, and it is determined that the arc current is detected at this point.
[0042]
Next, the third integration method counts up by 1 when the absolute value ΔA (n) of the difference between the current peak times of the adjacent cycles becomes equal to or greater than the threshold value of 0.5 msec, and when the absolute value ΔA (n) becomes less than 0.5 msec. A method of subtracting a predetermined value M, here, M = 0.2. The main integration operation corresponding to the difference ΔA (n) ′ of the current peak time in FIG. 11 is shown in FIG. 13, and when the point P21 in FIG. 11 becomes equal to or more than the positive threshold value K1, as shown in a point P80 in FIG. Is incremented by one. Next, since the point P22 is on the inside between the threshold values K1 and K2, M = 0.2 is subtracted from the integrated value Wb as shown from the point P80 to the point P81. Next, when the point P23 becomes equal to or less than the negative threshold value K2, the integrated value Wb is counted up by one as shown from the point P81 to the point P82. Then, when the integrated value Wb exceeds the arc detection threshold value K4 (= 3), it is determined that the arc current is detected. In this integration method, arc detection is performed when the absolute value ΔA (n) of the difference between the current peak times equal to or larger than the threshold value continues over a certain period.
[0043]
As a fourth integration method, when the absolute value ΔA (n) of the difference between the current peak times exceeds the threshold value 0.5 msec within a predetermined period, a method of integrating {ΔA (n) −0.5 msec}. When the integrated value within a predetermined period exceeds an arc detection threshold, it is determined that an arc current has been detected.
[0044]
Further, as a fifth integration method, there is a method of counting up by one when the absolute value ΔA (n) of the difference between the current peak times becomes equal to or larger than the threshold value 0.5 msec within a predetermined period. When the integrated value exceeds the arc detection threshold, it is determined that the arc current has been detected.
[0045]
In any of the second to fifth integration methods, integration is performed when the absolute value ΔA (n) of the difference between the current peak times exceeds the threshold value 0.5 msec. The difference between the absolute value ΔA (n) of the difference between the peak times and the threshold value 0.5 msec is integrated. In this integration method, when ΔA (n) −0.5 msec is large, the integrated value increases at a stretch. Since the arc detection is performed, the detection time can be shortened. On the other hand, the third and fifth integration methods count up by one when the absolute value ΔA (n) of the difference between the current peak times exceeds the threshold value 0.5 msec. The feature is that calculation is easy and the amount of memory used can be suppressed.
[0046]
Regarding the integration period, the fourth and fifth integration methods always determine the arc current by integration within the latest predetermined period, whereas the second and third integration methods determine the current peak time. When the absolute value of the difference ΔA (n) exceeds the threshold value 0.5 msec, the integration is performed, and when the absolute value is not exceeded, the subtraction is performed. The memory of the microcomputer 3 does not need to store the latest integration period information. Although this integration method can be reduced, this integration method is devised as a simple method of the fourth and fifth integration methods. If the integration time is long, the intended integration may not be performed.
[0047]
As shown in FIG. 14, the current waveform of an inverter type microwave oven or the like is flat near the peak of the current waveform. The current signal is A / D converted by the microcomputer 3 as shown in FIG. 15. Depending on the resolution of the A / D conversion (in FIG. 15, sampling is performed at 100 μsec), the current having the same digital value is obtained in the range of time t1 to t2. The peak value Ipeak10 may be a plurality of points. In this case, the current peak time A (n) is defined as a time t3 which is an intermediate time between the time t1 at which the current peak value Ipeak10 occurs earliest and the time t2 at which the current peak value Ipeak10 occurs at the latest. The detection accuracy of the time A (n) can be improved.
[0048]
FIG. 16 shows a case where the current peak point is flat and the current peak point is deviated from the original position to be detected due to an A / D conversion error. An error occurs when the peak time is A (n). In order to prevent this, the current Ipeak 11 ′ is much smaller than the current peak point by a value smaller than the current peak value Ipeak 11, and the point E is earlier than the generation time of the current peak value, and the point is later than the generation time of the current peak value. The detection accuracy of the current peak time A (n) can be improved by detecting the times t4 and t5 of F and setting the time t6 which is an intermediate time between the times t4 and t5 as the current peak time A (n).
[0049]
Furthermore, since the peak of the arc current waveform is convex and the current peak value of the same digital value does not continue in the arc current waveform in the same manner as the load current, the current peak value of the same digital value continues for a certain number or more. In this case, the waveform can be determined to be a load-specific waveform. If the waveform is a load-specific waveform, the absolute value ΔA (n) of the difference between the current peak times is forcibly set to zero (ΔA (n) = 0). Thus, a malfunction due to such load characteristics can be prevented.
[0050]
Next, FIG. 17 shows a current waveform and a power supply voltage waveform when the power factor of the load current is very bad. When the power factor of the load current is very bad, the current peak point may be near the voltage zero-cross times t7 and t8. Since the current peak value is detected between the voltage zero cross times t7 and t8, if the current peak point deviates from this time t7 and t8, the current peak time A (n) may be erroneously detected. Therefore, in consideration of the detection accuracy of the current peak point, the current peak point is located within the ranges T1 (for example, phases 0 ° to 10 °) and T2 (for example, phases 170 ° to 180 °) near the voltage zero-cross times t7 and t8. If there is, by setting the absolute value ΔA (n) of the difference between the current peak times to zero (ΔA (n) = 0), malfunction due to such a load can be prevented.
[0051]
Also, immediately after the power is turned on and the load current starts to flow, or when the use mode is switched while using the load device, the current peak time A (n) may fluctuate. In this case, the absolute value ΔA (n) of the difference between the current peak times is larger than the absolute value ΔA (n) of the difference between the current peak times when the arc current is generated, and the duration of the fluctuation is as short as several cycles. Therefore, when the absolute value ΔA (n) of the difference between the current peak times is larger than the threshold value, the absolute value ΔA (n) of the difference between the current peak times is forcibly set to zero (ΔA (n) = 0). It is possible to prevent a malfunction caused by turning on the power of the load device or switching the use mode.
[0052]
Next, in the case of an inverter type washing machine or the like, the absolute value ΔA (n) of the difference between the current peak times is large, which may cause a malfunction. Hereinafter, a method for preventing this malfunction will be described. FIG. 18 shows the difference ΔA (n) ′ between the current peak times of the inverter type washing machine. This variation is large even among load devices, and is comparable to the magnitude of the variation when the arc current is generated.
[0053]
Here, FIG. 19 shows the difference between the peak current difference {Ipeak (n + 1) -Ipeak (n)} of the adjacent cycle and the difference ΔA (n) ′ of the current peak time for the load current of the inverter type washing machine. FIG. 20 shows the same correlation as in FIG. 19 for the arc current of the inverter type washing machine. In general, the load current of the inverter type washing machine is gathered in a portion near the origin, and falls within a range Q1 obliquely crossing the origin in FIG. 19, and although the fluctuation of the current peak value of the adjacent cycle greatly fluctuates, In a region where the difference between the current peak values is small (for example, -5A to 5A), the change in the peak time difference is relatively small, the difference between the current peak values is -5A to 5A, and the difference between the peak times is 500 µsec or more or -500 µsec or less. Is characterized in that there is no distribution in the range Q2. On the other hand, the arc current fluctuates irregularly every half-wave for its current value and current peak time. Therefore, as shown in FIG. 20, the distribution is characterized in that it spreads over a wider range Q3 than the load current, and the fluctuation of the peak time difference is large even in a region where the current peak value difference is small. Therefore, when the absolute value of the difference between the current peak values is in the region Q4 (the hatched portion in FIG. 19, 5A or more and -5A or less) larger than the threshold value, the absolute value ΔA (n) of the difference between the current peak times is set to By forcibly setting it to zero (ΔA (n) = 0), it is possible to prevent the malfunction of the inverter type washing machine by excluding it from the detection target.
[0054]
Further, measures against malfunction under a general load will be described below. Since the fluctuation of the peak current value of each half-wave of the arc current is larger than the fluctuation of the peak current of the load current, the integrated value W exceeds the threshold value and the current peak value Ipeak (n) for each half-wave of the AC current is The absolute value ΔIpeak (n) = | Ipeak (n + 1) −Ipeak (n) | of the difference between the detected current peak value Ipeak (n) and the half-wave current peak value Ipeak (n + 1) after one cycle. If it is determined that an arc current has occurred when a state in which the absolute value of the current difference ΔIpeak (n) is larger than the threshold value continues for a predetermined number of times, the phase change at the current peak point and the current peak Since the determination of the arc current detection is performed based on the change in the value, the malfunction can be further reduced.
[0055]
Another measure will be described below. Since the current peak time A (n) of the arc current fluctuates irregularly, the absolute value ΔA (n) of the difference between the current peak times also varies within a certain range. On the other hand, the absolute value ΔA (n) of the difference between the current peak times of the load currents is the absolute value of the difference between the current peak times except when the load is turned on, when the use mode is changed, and when an inverter type washing machine is not used. The value ΔA (n) is relatively small and falls within a predetermined range. Therefore, the absolute value ΔA (n) of the difference between the current peak times is integrated for each subsection divided by the absolute value ΔA (n) of the difference between the current peak times. For example, the subsections are W1, W2, W3. . . When p <ΔA (n) ≦ q, integration is performed in the small section W1. When q <ΔA (n) ≦ r, integration is performed in the small section W2. . . Each subsection W1, W2, W3. . . It is integrated every time and compared with the threshold value set for each subsection.
[0056]
When the above integration method is used, the absolute value ΔA (n) of the difference between the peak currents of the arc current varies, so that the arc current is integrated evenly in a plurality of small sections. On the other hand, in the case of load current, integration is performed only in a specific small section. Therefore, in a plurality of preset small sections, when the integrated value for each of the small sections exceeds the threshold value, it is determined that the arc current is detected, so that malfunctions with respect to the load current can be reduced.
[0057]
(Embodiment 2)
FIG. 21 shows a time (current peak time) B (n) (positive half wave: n = 1, 2) from the current peak point of each half wave to the current peak point of the next half wave as the peak phase of the arc current. , 3, 4, 5, ..., negative half-waves: n = 1 ', 2', 3 ', 4', 5 ', ...), and the detected current peak time B (n) And the absolute value ΔB (n) = | B (n) −B (n + 1) | of the difference between the current peak time B (n + 1) detected after one cycle (the difference between the current peak times of adjacent cycles). The calculated value is calculated by integrating the absolute value ΔB (n) of the difference between the current peak times of the adjacent cycles from the predetermined period (t0−α) to t0.
[0058]
(Equation 2)

[0059]
This integrated value W is also represented by W = W + ΔB (n) (however, integrated within a predetermined period). Then, the integrated value W is compared with the threshold value, and when the integrated value W exceeds the threshold value, it is determined that an arc current has occurred.
[0060]
This arc current determination method does not need to detect the zero crossing point of the voltage as in the first embodiment, and can determine the arc current by detecting only the current waveform. This can be performed in the same manner as in the first embodiment.
[0061]
(Embodiment 3)
FIG. 22 shows, as the peak phase of the arc current, the time (current peak time) C (n) (positive half wave: n) from the current peak point of each half wave to the current peak point of the half wave after the next one cycle. = 1,2,3,4,5, ..., negative half-wave: n = 1 ', 2', 3 ', 4', 5 ', ...) and the detected current peak time Absolute value ΔC (n) = | C (n) −C (C) of the difference between C (n) and the current peak time C (n + 1) of the half-wave detected after one cycle (the difference between the current peak times of adjacent cycles). n + 1) | and performs integration represented by [Equation 3] for the absolute value ΔC (n) of the difference between the current peak times of adjacent cycles during a predetermined period (t0−α) to t0. It is.
[0062]
[Equation 3]

[0063]
This integrated value W is also represented by W = W + ΔC (n) (however, integrated within a predetermined period). Then, the integrated value W is compared with the threshold value, and when the integrated value W exceeds the threshold value, it is determined that an arc current has occurred.
[0064]
This arc current discrimination method is effective in the case of different current waveforms on the positive side and the negative side, such as a half-wave rectified current waveform appearing in the weak mode of the dryer, except for the phase detection method of the current peak point. This can be performed in the same manner as in the first embodiment.
[0065]
Here, in a general household, a plurality of loads are usually used at the same time, and the waveform of the current flowing through the electric circuit of the general household is a sum (sum) of the respective load currents. Even in such a situation, the arc current flows. Need to be detected. In the first to third embodiments, even in such a case, the current peak time of each half-wave similarly varies, so that the arc current can be detected.
[0066]
Further, in the tracking phenomenon of the plug, a minute current flows between the plug blades of the plug, and the current gradually increases due to the progress of insulation deterioration, eventually leading to a short circuit. Since this phenomenon generates an arc even with a relatively small current (about 2 to 3 A) and leads to a fire, it is necessary to detect the arc current as small as possible and cut off the electric circuit. In the first to third embodiments, since the current peak time is detected, the current peak time can be detected even with a small current value of about 2 to 3 A, and the tracking phenomenon of the plug can be detected early.
[0067]
In the above first to third embodiments, the method and the apparatus for detecting the fluctuation of the current peak time and discriminating between the arc current and the load current have been described. However, according to the nature of the arc current, the time at which the arc current starts to flow in each cycle, the time at which the current stops flowing, and the like also vary. Therefore, in addition to the fluctuation of the current peak time described in the first to third embodiments, the arc current and the load current can be identified by detecting the time of the start point and the end point of the current.
[0068]
Also, the difference between the detected current peak times A (n), B (n), and C (n) and the current peak times A (n + 1), B (n + 1), and C (n + 1) of the half-wave after one cycle. The absolute value is calculated, and a function using the absolute value of the difference between the current peak times as a variable is integrated. The difference between the current peak times is determined by the detected current peak time and the half-wave current detected after a predetermined period. The difference from the peak time may be used. For example, the detected current peak times A (n), B (n), and C (n) and the half-wave current peak times A (n) ′ and B (n) detected half a cycle later. , C (n) ′.
[0069]
【The invention's effect】
The invention according to claim 1 detects a phase of a current peak point for each half-wave of an alternating current supplied from an AC power supply to an AC load circuit, and detects a phase of the detected current peak point and a half-wave current detected after a predetermined period. When the absolute value of the difference from the phase of the peak point is calculated, a function using the absolute value of the phase difference as a variable is integrated, the integrated value is compared with a threshold, and the integrated value exceeds the threshold. It is determined that an arc current has occurred, so it is not erroneously detected with a normal load current.It detects an arc short-circuit phenomenon due to a short between core wires and an abnormal current in an AC circuit due to a series arc phenomenon caused by a break in the core wire. There is an effect that can be.
[0070]
According to a second aspect of the present invention, in the first aspect, the phase of the current peak point of the AC current is detected as a time from a zero crossing point of the power supply voltage to a current peak point for each half-wave. There is an effect that a specific method for detecting the phase of a point can be provided.
[0071]
According to a third aspect of the present invention, in the first aspect, the phase of the current peak point of the alternating current is detected as the time from the current peak point of each half wave to the current peak point of the next half wave. 2, it is not necessary to detect the zero crossing point of the voltage, and it is possible to determine the arc current detection by detecting only the current waveform.
[0072]
According to a fourth aspect of the present invention, in the first aspect, a phase of a current peak point of the alternating current is detected as a time from a current peak point of each half wave to a current peak point of a half wave after one cycle. This is effective when the current waveforms on the positive side and the negative side are different from each other, such as a half-wave rectified current waveform appearing in the weak mode of the dryer.
[0073]
According to a fifth aspect of the present invention, according to any one of the first to fourth aspects, since the integrating operation integrates a function using the absolute value of the phase difference as a variable within a predetermined period, the arc current detection based on the latest period information. This has the effect that the determination can be made.
[0074]
According to a sixth aspect of the present invention, in accordance with any one of the second to fifth aspects, the AC current is sampled at a predetermined cycle and converted into a digital value, and then the time of the current peak point is detected. Is detected in a half-wave, the time between the time when the current peak value occurs earliest and the time when the current peak value occurs latest is defined as the time of the current peak point. In the case of a current waveform having a flat peak near the peak as in the above-described example, the detection accuracy of the time of the current peak point can be improved.
[0075]
According to a seventh aspect of the present invention, in any one of the second to fifth aspects, the AC current is sampled at a predetermined cycle and converted into a digital value, and then a minute value with respect to the current peak value is subtracted from the current peak value. The time at which the current value is generated, and the time between the time earlier and later than the time at which the current peak value occurs is defined as the time of the current peak point. Has an effect that the accuracy of detecting the time of the current peak point can be improved even when the position is shifted from the original position to be detected due to an A / D conversion error.
[0076]
According to an eighth aspect of the present invention, in the sixth aspect, when a current peak value of the same digital value is detected by a predetermined number of samples or more in a half wave, a function using the absolute value of the phase difference as a variable is set to zero. Therefore, there is an effect that malfunction due to load characteristics can be prevented.
[0077]
According to a ninth aspect of the present invention, in any one of the second to seventh aspects, when the time of the current peak point is detected out of a predetermined range, the function using the absolute value of the phase difference as a variable is set to zero. In the case where the power factor of the load current is poor, it is possible to prevent erroneous detection of the time of the current peak point and to prevent malfunction due to load characteristics.
[0078]
According to a tenth aspect of the present invention, when the absolute value of the phase difference exceeds a threshold value, a function using the absolute value of the phase difference as a variable is set to zero. There is an effect that a malfunction due to a power-on or a change in a use mode can be prevented.
[0079]
According to an eleventh aspect of the present invention, in any one of the first to seventh aspects, a current value at a current peak point for each half-wave of the alternating current is detected, and the half-wave detected one cycle after the detected current value at the current peak point. The absolute value of the difference between the current value of the current peak point and the absolute value of the current difference is compared with a threshold value.If the absolute value of the current difference is greater than the threshold value, the absolute value of the phase difference is calculated. Since the function as a variable is set to zero, there is an effect that malfunction can be prevented for a load such as an inverter type washing machine having a large time variation at the current peak point.
[0080]
According to a twelfth aspect of the present invention, in any one of the first to fourth aspects, when the absolute value of the phase difference exceeds a threshold value, the integrated value is a value obtained by subtracting a predetermined value from the absolute value of the phase difference for a predetermined period. , The determination of the arc current detection can be made based on the information of the latest period, and when the phase of the current peak point fluctuates greatly, the detection time is shortened.
[0081]
According to a thirteenth aspect, in the first aspect, the integrated value is a value counted up within a predetermined period when the absolute value of the phase difference exceeds a threshold value. As a result, it is possible to determine the arc current detection, and furthermore, there is an effect that calculation is easy in programming of the microcomputer and the amount of memory used can be suppressed.
[0082]
According to a fourteenth aspect of the present invention, in any one of the first to fourth aspects, when the absolute value of the phase difference exceeds a threshold value, the integrated value is a first predetermined value from the absolute value of the phase difference each time. When the absolute value of the phase difference does not exceed the threshold value, the value obtained by subtracting the second predetermined value from the integrated value is used each time the subtracted value is integrated. Since there is no memory, the memory of the microcomputer can be reduced, and when the phase of the current peak point fluctuates greatly, the detection time is shortened.
[0083]
In the invention according to claim 15, according to any one of claims 1 to 4, the integrated value is counted up each time the absolute value of the phase difference exceeds a threshold value, and the absolute value of the phase difference is set to a threshold value. If the value does not exceed the predetermined value, the value is subtracted each time.Therefore, it is not necessary to secure the information of the latest period in the memory, so that the memory of the microcomputer can be reduced. This has the effect of further reducing the amount of memory used.
[0084]
According to a sixteenth aspect of the present invention, in any one of the first to seventh aspects, when the integrated value exceeds a threshold value, and a current value at a current peak point for each half-wave of the alternating current is detected, and the detected current peak point is detected. The absolute value of the difference between the current value of the current difference and the current value of the half-wave current peak point detected one cycle later is calculated, and the absolute value of the current difference is compared with a threshold value. Since it is determined that an arc current has occurred when the larger state has continued for a predetermined number of times, the determination of the arc current detection is performed based on the variation of the phase of the current peak point and the variation of the current peak value, and the malfunction is reduced. There is an effect that it can be reduced.
[0085]
According to a seventeenth aspect, in the first aspect, the function using the absolute value of the phase difference as a variable is integrated for each small section divided by the absolute value of the phase difference, and the integrated value for each small section is a small section. Since it is determined that an arc current has occurred when the integrated value exceeds the threshold value in a predetermined small section by being compared with a threshold value set for each, a malfunction can be reduced.
[0086]
The invention according to claim 18 is means for detecting the phase of the current peak point for each half-wave of the alternating current supplied from the AC power supply to the AC load circuit, and detecting the phase of the detected current peak point and the half-wave detected after a predetermined period. Means for calculating the absolute value of the difference from the phase of the current peak point, means for integrating a function using the absolute value of the phase difference as a variable, means for comparing the integrated value with a threshold, and the integrated value Means for determining that an arc current has occurred when the threshold value exceeds a threshold value, so that it is not erroneously detected at a normal load current, an arc short-circuit phenomenon due to a short circuit between core wires, or an AC There is an effect that an apparatus for detecting an abnormal current in a circuit can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first method for detecting the phase of a current peak point according to the present invention.
FIG. 2 is a diagram showing a circuit configuration of the above.
FIG. 3 is a diagram showing a current signal and a voltage signal that have been converted into absolute values according to the first embodiment.
FIG. 4 is a diagram showing a current signal and a voltage signal which are not converted into absolute values according to the embodiment.
FIG. 5 is a diagram showing an arc current waveform.
FIG. 6 is an enlarged view of an arc current waveform.
FIG. 7 is a diagram showing a load current waveform of the vacuum cleaner.
FIG. 8 is a diagram showing a time change of a current peak time of a load current of the vacuum cleaner.
9 is a diagram showing a time change of a difference between current peak times of adjacent periods in FIG. 8;
FIG. 10 is a diagram showing a time change of a current peak time of an arc current.
11 is a diagram showing a time change of a difference between current peak times of adjacent periods in FIG. 10;
FIG. 12 is a diagram illustrating a first integration method of a difference between current peak times in FIG. 11;
FIG. 13 is a diagram illustrating a second method of integrating the difference between the current peak times in FIG. 11;
FIG. 14 is a diagram showing a current waveform of an inverter type microwave oven.
FIG. 15 is a diagram showing a first method of detecting a current peak time according to the present invention.
FIG. 16 is a diagram showing a second method for detecting a current peak time according to the second embodiment.
FIG. 17 is a diagram showing a detection range of a current peak time according to the third embodiment.
FIG. 18 is a diagram showing a time change of a difference between current peak times of adjacent cycles of the inverter type washing machine.
FIG. 19 is a diagram showing a correlation between a current peak difference and a current peak time difference of a load current of the inverter type washing machine.
FIG. 20 is a diagram showing a correlation between a current peak difference and a current peak time difference of an arc current.
FIG. 21 is a diagram showing a second method for detecting the phase of the current peak point according to the present invention.
FIG. 22 is a diagram showing a third method for detecting the phase of the current peak point according to the third embodiment.
[Explanation of symbols]
A1, A1 ', A2, A2',. . . Current peak time
Ipeak1, Ipeak1 ',. . . Current peak value

Claims (18)

The phase of the current peak point for each half-wave of the alternating current supplied from the AC power supply to the AC load circuit is detected, and the difference between the phase of the detected current peak point and the phase of the half-wave current peak point detected after a predetermined period is detected. Calculate the absolute value of, and integrate a function using the absolute value of the phase difference as a variable, compare the integrated value with a threshold value, and determine that an arc current has occurred when the integrated value exceeds a threshold value. An arc current discriminating method characterized by making a judgment. The method according to claim 1, wherein the phase of the current peak point of the alternating current is detected as a time from a zero crossing point of the power supply voltage to a current peak point for each half wave. The method according to claim 1, wherein the phase of the current peak point of the alternating current is detected as a time from a current peak point for each half-wave to a current peak point of the next half-wave. 2. The arc current discriminating method according to claim 1, wherein the phase of the current peak point of the alternating current is detected as a time from a current peak point for each half wave to a current peak point of a half wave after one cycle. . 5. The arc current discriminating method according to claim 1, wherein the integrating operation integrates a function using an absolute value of the phase difference as a variable within a predetermined period. The AC current is sampled at a predetermined cycle and converted to a digital value, and then the time of the current peak point is detected.If a plurality of current peak values of the same digital value are detected in a half wave, the earliest current is detected. 6. The arc current discriminating method according to claim 2, wherein an intermediate time between the time when the peak value occurs and the time when the current peak value occurs latest is defined as the time of the current peak point. A time during which the AC current is sampled at a predetermined cycle and converted into a digital value, and a current value obtained by subtracting a minute value from the current peak value with respect to the current peak value is generated, and a generation time of the current peak value. 6. The arc current discriminating method according to claim 2, wherein an intermediate time between the earlier time and the later time is the time of the current peak point. 7. The arc current according to claim 6, wherein when a current peak value of the same digital value is detected by a predetermined number of samples or more in a half wave, a function using the absolute value of the phase difference as a variable is set to zero. Judgment method. 8. The arc current discriminating method according to claim 2, wherein when a time of the current peak point is detected outside a predetermined range, a function using the absolute value of the phase difference as a variable is set to zero. . 8. The method according to claim 1, wherein when the absolute value of the phase difference exceeds a threshold, a function using the absolute value of the phase difference as a variable is set to zero. The current value at the current peak point for each half-wave of the AC current is detected, and the absolute value of the difference between the current value at the detected current peak point and the current value at the half-wave current peak point detected one cycle later is calculated. Comparing the absolute value of the current difference with a threshold, and when the absolute value of the current difference is larger than the threshold, setting a function having the absolute value of the phase difference as a variable to zero. 8. The arc current determination method according to any one of 1 to 7. The method according to claim 1, wherein the integrated value is a value obtained by integrating a value obtained by subtracting a predetermined value from the absolute value of the phase difference within a predetermined period when the absolute value of the phase difference exceeds a threshold value. 4. The method for determining an arc current according to claim 4. The method according to any one of claims 1 to 4, wherein the integrated value is a value counted up within a predetermined period when the absolute value of the phase difference exceeds a threshold value. When the absolute value of the phase difference exceeds a threshold, a value obtained by subtracting a first predetermined value from the absolute value of the phase difference is integrated each time the absolute value of the phase difference exceeds the threshold. The method according to any one of claims 1 to 4, wherein a value obtained by subtracting a second predetermined value from the integrated value each time the value does not exceed the predetermined value is obtained. The integrated value is a value obtained by counting up each time when the absolute value of the phase difference exceeds a threshold, and subtracting a predetermined value each time when the absolute value of the phase difference does not exceed the threshold. The method according to any one of claims 1 to 4, wherein: When the integrated value exceeds a threshold value, and the current value of the current peak point for each half-wave of the AC current is detected, and the current value of the detected current peak point and the current peak point of the half-wave detected one cycle later are detected. The absolute value of the difference from the current value is calculated, the absolute value of the current difference is compared with a threshold value, and when the state where the absolute value of the current difference is larger than the threshold value continues for a predetermined number of times, the arc current 8. The arc current discriminating method according to claim 1, wherein it is determined that an arc has occurred. A function using the absolute value of the phase difference as a variable is integrated for each small section delimited by the absolute value of the phase difference, and the integrated value for each small section is compared with a threshold value set for each small section, and a predetermined value is calculated. 2. The arc current discriminating method according to claim 1, wherein it is determined that an arc current has occurred when the integrated value exceeds a threshold value in the small section of (1). Means for detecting the phase of the current peak point for each half-wave of the alternating current supplied from the AC power supply to the AC load circuit, and the phase of the detected current peak point and the phase of the half-wave current peak point detected after a predetermined period. Means for calculating the absolute value of the difference, means for integrating a function using the absolute value of the phase difference as a variable, means for comparing the integrated value with a threshold, and when the integrated value exceeds the threshold. Means for determining that an arc current has occurred.

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