JP3961868B2 - Power converter - Google Patents

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JP3961868B2
JP3961868B2 JP2002106639A JP2002106639A JP3961868B2 JP 3961868 B2 JP3961868 B2 JP 3961868B2 JP 2002106639 A JP2002106639 A JP 2002106639A JP 2002106639 A JP2002106639 A JP 2002106639A JP 3961868 B2 JP3961868 B2 JP 3961868B2
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output
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JP2003304634A (en
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康裕 安東
昌樹 柳川
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Toshiba Mitsubishi Electric Industrial Systems Corp
Toshiba Plant Systems and Services Corp
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Toshiba Mitsubishi Electric Industrial Systems Corp
Toshiba Plant Systems and Services Corp
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Description

【０００１】
【発明の属する技術分野】
本発明は、出力ケーブルの断線検出機能を備えた電力変換装置に関する。
【０００２】
【従来の技術】
従来の電力変換装置としては、図８に示す構成のものがよく知られている。同図において、直流電源１からの直流電圧は、インバータ回路２により任意の周波数の（通常は３相）交流電圧に変換され、負荷としての電動機３に可変周波数の交流電力が供給されるようになっている。インバータ回路２の出力ケーブルには、出力電流を検出する電流検出器としての変流器５が取り付けられ、変流器５で検出された出力電流信号は、整流器６で整流された後、電動機３の回転数を制御する制御回路７に入力されている。制御回路７には、この整流された出力電流信号と速度設定器４で発生した速度基準信号４ａとが入力されている。
【０００３】
次に、装置動作を簡単に説明する。制御回路７は、速度設定器４からの速度基準信号４ａと整流器６で整流された出力電流信号とから電動機３が所定の回転数となるようにインバータ回路２に制御信号７ａを出力する。インバータ回路２は、スイッチング素子として自己消弧型の素子（最近ではＩＧＢＴが主流）が使用されており、制御回路７により出力波形及び出力周波数が制御される。
【０００４】
【発明が解決しようとする課題】
しかしながら、従来の電力変換装置は、出力ケーブルが断線した場合に運転を継続してしまうという問題があった。
【０００５】
本発明は、上記に鑑みてなされたもので、出力ケーブルが断線したとき、これを確実に検出して運転を停止することができ、信頼性を向上させることができる電力変換装置を提供することを目的とする。
【０００８】
【課題を解決するための手段】
上記課題を解決するために、請求項１記載の発明は、出力電流を検出する電流検出手段と、この電流検出手段で検出した出力電流信号を整流する整流手段と、この整流した出力電流信号の最大値及び最小値を演算する電流信号演算手段と、この電流信号演算手段からの最大値と最小値の差が予め定めた電流偏差設定値を一定期間継続して超えたときは偏差大継続信号を出力し、一定期間継続しないときは制御異常信号を出力する制御異常判断手段と、前記最小値が予め定めた所定値以下となったとき低下信号を出力する電流レベル検出手段と、前記偏差大継続信号と前記低下信号の論理積をとって断線検出信号を出力する断線検出手段と、前記断線検出信号により装置動作を停止する制御手段とを有することを要旨とする。この構成により、制御異常判断手段では、出力電流信号の最大値と最小値の差が電流偏差設定値を一定期間継続して超えたとき偏差大継続信号が出力され、一定期間継続しないときは制御異常信号が出力される。偏差大継続信号が出力されたときは、これと低下信号の論理積をとることで出力ケーブルの断線が検出されて運転が停止される。一方、制御異常信号が出力されたときは、出力ケーブルの断線ではなく、制御上の不安定と判断される。
【００１０】
請求項２記載の発明は、出力電流を検出する電流検出手段と、この電流検出手段で検出した出力電流信号を整流する整流手段と、この整流した出力電流信号の最大値及び最小値を演算する電流信号演算手段と、前記出力電流信号の最大値から最小値までの時間と出力周波数の周期とを比較し、前記最大値から最小値までの時間が前記出力周波数の周期に対し所定値以上となったときピーク到達時間検出信号を出力するピーク到達時間検出手段と、前記最小値が予め定めた所定値以下となったとき低下信号を出力する電流レベル検出手段と、前記ピーク到達時間検出信号と前記低下信号の論理積をとって断線検出信号を出力する断線検出手段と、前記断線検出信号により装置動作を停止する制御手段とを有することを要旨とする。この構成により、出力ケーブルが断線したとき、出力電流信号の最大値から最小値までの時間は、出力周波数の周期以下となる。リップル周期検出手段では、この最大値から最小値までの時間と出力周波数の周期とが比較され、最大値から最小値までの時間が出力周波数の周期に対し所定値以上となったときピーク到達時間検出信号が出力される。このピーク到達時間検出信号と低下信号の論理積をとることで、出力ケーブルの断線が確実に検出されて運転が停止される。
【００１１】
請求項３記載の発明は、請求項１または２に記載の電力変換装置において、負荷として複数台の電動機を駆動することを要旨とする。この構成により、負荷である電動機が複数台になっても、出力ケーブルの断線時には出力電流信号の最小値が低下するため、出力ケーブルの断線を確実に検出して運転を停止することが可能となる。
【００１２】
【発明の実施の形態】
以下、本発明の実施の形態を図面に基づいて説明する。
【００１３】
図１及び図２は、本発明の第１の実施の形態を示す図である。まず、図１を用いて、本実施の形態の電力変換装置の構成を説明する。同図において、直流電源１からの直流電圧は、インバータ回路２により任意の周波数の（通常は３相）交流電圧に変換され、電動機３に可変周波数の交流電力が供給されるようになっている。インバータ回路２の出力ケーブルには、出力電流を検出する電流検出手段としての変流器５が取り付けられ、変流器５で検出された出力電流信号は、整流手段としての整流器６で整流された後、電動機３の回転数を制御する制御手段としての制御回路７に入力されている。制御回路７には、この整流された出力電流信号６ａと速度設定器４で発生した速度基準信号４ａが入力されている。制御回路７は、速度設定器４で設定された速度基準で電動機３が回転するように、整流された出力電流信号６ａをフィードバックしつつインバータ回路２に対して位相制御信号７ａを出力して制御する。
【００１４】
そして、本実施の形態では、さらに整流器６の出力端子に電流信号演算手段としての電流信号演算器８が接続され、電流信号演算器８の出力端子に電流偏差検出手段としての電流偏差検出器９と電流レベル検出手段としての電流レベル検出器１０が並列に接続されている。これら電流偏差検出器９と電流レベル検出器１０の各出力は断線検出手段としての断線検出器１１に入力され、断線検出器１１の出力は制御回路７に入力されている。電流信号演算器８は、整流器６から整流された出力電流信号６ａを入力し、その出力電流信号６ａの最大値と最小値を演算する。電流偏差検出器９は、電流信号演算器８から最大値８ａと最小値８ｂを入力し、最大値８ａと最小値８ｂの差が予め定めた電流偏差設定値を超えたときに偏差大信号９ａを出力する。電流レベル検出器１０は、電流信号演算器８から最小値８ｂを入力し、その最小値８ｂが予め設定した所定値以下になったときに低下信号１０ａを出力する。断線検出器１１は、電流偏差検出器９から偏差大信号９ａを入力し、電流レベル検出器１０から低下信号１０ａを入力して偏差大信号９ａと低下信号１０ａの論理積をとり、断線検出信号１１ａを出力する。制御回路７は、断線検出器１１からの断線検出信号１１ａが入力された場合に装置の停止動作を行う。
【００１５】
次に、図２を用いて、出力ケーブル断線時の制御動作を説明する。出力ケーブル断線時は、整流器６から出力される整流された出力電流信号６ａが低下する。したがって、電流信号演算器８から出力される最小値８ｂが低下する。電流偏差検出器９に入力される最小値８ｂが低下することで、最大値８ａと最小値８ｂの差が大きくなって予め定めた電流偏差設定値を超え、電流偏差検出器９は、偏差大信号９ａを出力する。また、電流レベル検出器１０に入力される最小値８ｂも低下することで、最小値８ｂが予め設定した所定値以下になり、電流レベル検出器１０は低下信号１０ａを出力する。この結果、断線検出器１１に、偏差大信号９ａと低下信号１０ａが入力され、断線検出器１１は、これら両信号９ａ，１０ａの論理積をとって出力ケーブルの断線（３相の場合は欠相を含む）を検出し、断線検出信号１１ａを出力する。そして、制御回路７には、断線検出器１１から断線検出信号１１ａが入力され、運転停止動作が行われる。出力電流信号６ａの最大値８ａと最小値８ｂの差のみから、出力ケーブルの断線（又は欠相）を検出したのでは、制御切り替えによる再始動時に誤検出するおそれがある。これに対し、本実施の形態では、上述したように、最小値８ｂが所定値以下になった場合も判定資料に加味し、偏差大信号９ａと低下信号１０ａの論理積をとることで、出力ケーブルの断線（又は欠相）を確実に検出することができる。
【００１６】
図３には、本発明の第２の実施の形態を示す。なお、図３及び後述の各実施の形態を示す図において前記図１における構成要素と同一ないし均等のものは、前記と同一符号を以って示し、重複した説明を省略する。本実施の形態では、整流器６と整流偏差検出器９との間に平均値検出手段としての平均値検出器１２が接続されている。
【００１７】
平均値検出器１２は、整流器６からの整流された出力電流信号６ａを入力し、その出力電流信号６ａの平均値１２ａを算出して出力する。電流偏差検出器９は、平均値検出器１２からの平均値１２ａを入力し、この平均値１２ａに応じて電流偏差設定値に対して補正（調整）を行う。負荷量が変化すると、出力電流信号６ａの平均値が変化する。そこで、この平均値１２ａを算出し、この平均値１２ａに応じて電流偏差設定値を補正することで、負荷量の変化に対しても、出力ケーブルの断線（又は欠相）を確実に検出することができる。
【００１８】
図４には、本発明の第３の実施の形態を示す。本実施の形態は、図１に示した電流偏差検出器９に代えて、電流信号演算器８と断線検出器１１の間に制御異常判断手段としての制御異常判断器１３が接続されている。制御異常判断器１３は２つの出力端子を備え、一方の出力端子は断線検出器１１に接続され、他方の出力端子は制御回路７に接続されている。
【００１９】
制御異常判断器１３は、電流信号演算器８から出力電流信号６ａの最大値８ａと最小値８ｂを入力し、その最大値８ａと最小値８ｂの差が予め定めた電流偏差設定値を超え、これが一定期間継続したとき偏差大継続信号１３ａを断線検出器１１に出力し、一定期間継続しないときは、制御異常信号１３ｂを制御回路７に出力する。偏差大継続信号１３ａが出力されたときは、断線検出器１１により、この偏差大継続信号１３ａと低下信号１０ａの論理積をとることで、出力ケーブルの断線（又は欠相）が検出され、制御回路７により運転停止が行われる。一方、制御異常信号１３ｂが出力されたときは、出力ケーブルの断線ではなく、制御上の不安定と判断される。
【００２０】
図５には、本発明の第４の実施の形態を示す。本実施の形態は、図１に示した電流偏差検出器９に代えて、電流信号演算器８と断線検出器１１の間にリップル周期検出手段としてのリップル周期検出器１４が接続されている。リップル周期検出器１４は、出力線と入力線を備え、出力線は断線検出器１１に接続され、入力線により制御回路７から出力周波数信号７ｂを入力するようになっている。
【００２１】
出力ケーブルが断線（又は欠相）としたとき、出力電流信号６ａの最大値８ａと最小値８ｂの差が最大となるリップル周期は、出力周波数の周期以下（３相の場合、リップル周期は出力周波数の周期の略３分の１以下）となる。リップル周期検出器１４は、電流信号演算器８から出力電流信号６ａの最大値８ａと最小値８ｂを入力し、制御回路７からは出力周波数信号７ｂを入力する。そして、最大値８ａと最小値８ｂの差が最大となるリップル周期と出力周波数の周期とを比較し、リップル周期が出力周波数の周期に対し所定値以上となったときに、リップル周期検出信号１４ａを断線検出器１１に出力する。断線検出器１１では、リップル周期検出信号１４ａと低下信号１０ａの論理積をとることで、出力ケーブルの断線（又は欠相）を検出し、制御回路７により運転停止が行われる。
【００２２】
図６には、本発明の第５の実施の形態を示す。本実施の形態は、図１に示した電流偏差検出器９に代えて、電流信号演算器８と断線検出器１１の間にピーク到達時間検出手段としてのピーク到達時間検出器１５が接続されている。ピーク到達時間検出器１５は、出力線と入力線を備え、出力線は断線検出器１１に接続され、入力線により制御回路７から出力周波数信号７ｂを入力するようになっている。
【００２３】
出力ケーブルが断線（又は欠相）したとき、出力電流信号６ａの最大値８ａから最小値８ｂになるまでの時間は、出力周波数の周期以下となる。ピーク到達時間検出器１５は、電流信号演算器８から出力電流信号６ａの最大値８ａと最小値８ｂを入力し、制御回路７からは出力周波数信号７ｂを入力する。そして、最大値８ａから最小値８ｂになるまでの時間と出力周波数の周期とを比較し、最大値８ａから最小値８ｂになるまでの時間が出力周波数の周期に対し所定値以上となったときに、ピーク到達時間検出信号１５ａを断線検出器１１に出力する。断線検出器１１では、ピーク到達時間検出信号１５ａと低下信号１０ａの論理積をとることで、出力ケーブルの断線（又は欠相）を検出し、制御回路７により運転停止が行われる。
【００２４】
図７には、本発明の第６の実施の形態を示す。本実施の形態では、負荷として複数台の電動機３，３，…を駆動するようになっている。
【００２５】
複数台の電動機３，３，…を駆動する場合であっても、出力ケーブルの断線時には出力電流信号６ａの最小値８ｂが低下するため、出力ケーブル断線を検出することが可能である。
【００２６】
【発明の効果】
以上説明したように、請求項１〜３記載の発明によれば、出力ケーブルが断線したとき、これを確実に検出して運転を停止することができ、信頼性を向上させることができる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態である電力変換装置のブロック図である。
【図２】上記第１の実施の形態における出力ケーブル断線時の制御動作を説明するための出力電流信号波形図である。
【図３】本発明の第２の実施の形態のブロック図である。
【図４】本発明の第３の実施の形態のブロック図である。
【図５】本発明の第４の実施の形態のブロック図である。
【図６】本発明の第５の実施の形態のブロック図である。
【図７】本発明の第６の実施の形態のブロック図である。
【図８】従来の電力変換装置のブロック図である。
【符号の説明】
２ インバータ回路
３ 電動機
５ 変流器（電流検出手段）
６ 整流器（整流手段）
７ 制御回路（制御手段）
８ 電流信号演算器（電流信号演算手段）
９ 電流偏差検出器（電流偏差検出手段）
１０ 電流レベル検出器（電流レベル検出手段）
１１ 断線検出器（断線検出手段）
１２ 平均値検出器（平均値検出手段）
１３ 制御異常判断器（制御異常判断手段）
１４ リップル周期検出器（リップル周期検出手段）
１５ ピーク到達時間検出器（ピーク到達時間検出手段）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power conversion device having an output cable disconnection detection function.
[0002]
[Prior art]
As a conventional power converter, the one shown in FIG. 8 is well known. In the figure, the DC voltage from the DC power source 1 is converted into an AC voltage having an arbitrary frequency (usually three phases) by the inverter circuit 2 so that variable frequency AC power is supplied to the motor 3 as a load. It has become. A current transformer 5 as a current detector for detecting an output current is attached to the output cable of the inverter circuit 2. The output current signal detected by the current transformer 5 is rectified by the rectifier 6, and then the motor 3 Is input to the control circuit 7 for controlling the number of rotations. The control circuit 7 receives the rectified output current signal and the speed reference signal 4 a generated by the speed setter 4.
[0003]
Next, the operation of the apparatus will be briefly described. The control circuit 7 outputs a control signal 7a to the inverter circuit 2 from the speed reference signal 4a from the speed setter 4 and the output current signal rectified by the rectifier 6 so that the motor 3 has a predetermined rotational speed. In the inverter circuit 2, a self-extinguishing element (in recent years, IGBT is mainly used) is used as a switching element, and an output waveform and an output frequency are controlled by the control circuit 7.
[0004]
[Problems to be solved by the invention]
However, the conventional power conversion device has a problem that the operation is continued when the output cable is disconnected.
[0005]
The present invention has been made in view of the above, and provides a power conversion device that can reliably detect and stop operation when an output cable is disconnected, and can improve reliability. With the goal.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that a current detecting means for detecting an output current, a rectifying means for rectifying an output current signal detected by the current detecting means, and a rectified output current signal Current signal calculation means for calculating the maximum and minimum values, and a large deviation continuation signal when the difference between the maximum and minimum values from the current signal calculation means exceeds a predetermined current deviation set value for a certain period of time. Control abnormality determining means for outputting a control abnormality signal when the constant value does not continue for a certain period of time, current level detecting means for outputting a decrease signal when the minimum value falls below a predetermined value, and the large deviation The gist of the invention is to include a disconnection detecting means for taking a logical product of the continuation signal and the lowering signal and outputting a disconnection detection signal, and a control means for stopping the operation of the apparatus by the disconnection detection signal. With this configuration, the control abnormality determination means outputs a large deviation continuation signal when the difference between the maximum value and the minimum value of the output current signal exceeds the current deviation set value for a certain period, and controls when the difference does not continue for a certain period. An abnormal signal is output. When the large deviation continuation signal is output, the disconnection of the output cable is detected by taking the logical product of this and the decrease signal, and the operation is stopped. On the other hand, when the control abnormality signal is output, it is determined that the output cable is not disconnected and that the control is unstable.
[0010]
According to the second aspect of the present invention, the current detection means for detecting the output current, the rectification means for rectifying the output current signal detected by the current detection means, and the maximum value and the minimum value of the rectified output current signal are calculated. A current signal calculation means, comparing the time from the maximum value to the minimum value of the output current signal with the cycle of the output frequency, and the time from the maximum value to the minimum value is a predetermined value or more with respect to the cycle of the output frequency A peak arrival time detection means for outputting a peak arrival time detection signal when the current value reaches, a current level detection means for outputting a decrease signal when the minimum value is equal to or less than a predetermined value, and the peak arrival time detection signal; The gist of the invention is to include a disconnection detection means for taking a logical product of the lowering signals and outputting a disconnection detection signal, and a control means for stopping the operation of the apparatus by the disconnection detection signal. With this configuration, when the output cable is disconnected, the time from the maximum value to the minimum value of the output current signal is equal to or less than the period of the output frequency. In the ripple period detection means, the time from the maximum value to the minimum value is compared with the period of the output frequency, and the peak arrival time when the time from the maximum value to the minimum value exceeds the predetermined value with respect to the period of the output frequency A detection signal is output. By taking the logical product of the peak arrival time detection signal and the decrease signal, the disconnection of the output cable is reliably detected and the operation is stopped.
[0011]
The gist of the invention described in claim 3 is that, in the power converter according to claim 1 or 2 , a plurality of electric motors are driven as loads. With this configuration, even if there are multiple electric motors as loads, the minimum value of the output current signal decreases when the output cable is disconnected, so it is possible to reliably detect the disconnection of the output cable and stop operation. Become.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
1 and 2 are diagrams showing a first embodiment of the present invention. First, the configuration of the power conversion device according to the present embodiment will be described with reference to FIG. In the figure, a DC voltage from a DC power source 1 is converted into an AC voltage having an arbitrary frequency (usually three phases) by an inverter circuit 2, and AC power having a variable frequency is supplied to the motor 3. . The output cable of the inverter circuit 2 is attached with a current transformer 5 as current detection means for detecting output current, and the output current signal detected by the current transformer 5 is rectified by a rectifier 6 as rectification means. Thereafter, it is inputted to a control circuit 7 as a control means for controlling the rotation speed of the electric motor 3. The control circuit 7 receives the rectified output current signal 6 a and the speed reference signal 4 a generated by the speed setter 4. The control circuit 7 outputs and controls the phase control signal 7a to the inverter circuit 2 while feeding back the rectified output current signal 6a so that the motor 3 rotates with the speed reference set by the speed setter 4. To do.
[0014]
In this embodiment, a current signal calculator 8 as a current signal calculator is further connected to the output terminal of the rectifier 6, and a current deviation detector 9 as a current deviation detector is connected to the output terminal of the current signal calculator 8. And a current level detector 10 as a current level detecting means are connected in parallel. The outputs of the current deviation detector 9 and the current level detector 10 are input to a disconnection detector 11 as disconnection detection means, and the output of the disconnection detector 11 is input to the control circuit 7. The current signal calculator 8 receives the output current signal 6a rectified from the rectifier 6, and calculates the maximum value and the minimum value of the output current signal 6a. The current deviation detector 9 receives the maximum value 8a and the minimum value 8b from the current signal calculator 8, and a large deviation signal 9a when the difference between the maximum value 8a and the minimum value 8b exceeds a predetermined current deviation set value. Is output. The current level detector 10 receives the minimum value 8b from the current signal calculator 8, and outputs a decrease signal 10a when the minimum value 8b becomes equal to or less than a predetermined value set in advance. The disconnection detector 11 receives the large deviation signal 9a from the current deviation detector 9, receives the decrease signal 10a from the current level detector 10, and takes the logical product of the large deviation signal 9a and the decrease signal 10a to generate the disconnection detection signal. 11a is output. The control circuit 7 stops the apparatus when the disconnection detection signal 11a from the disconnection detector 11 is input.
[0015]
Next, the control operation when the output cable is disconnected will be described with reference to FIG. When the output cable is disconnected, the rectified output current signal 6a output from the rectifier 6 decreases. Therefore, the minimum value 8b output from the current signal calculator 8 decreases. As the minimum value 8b input to the current deviation detector 9 decreases, the difference between the maximum value 8a and the minimum value 8b increases and exceeds a predetermined current deviation setting value. The current deviation detector 9 The signal 9a is output. Further, the minimum value 8b input to the current level detector 10 also decreases, so that the minimum value 8b becomes equal to or less than a predetermined value set in advance, and the current level detector 10 outputs a decrease signal 10a. As a result, the large deviation signal 9a and the decrease signal 10a are input to the disconnection detector 11, and the disconnection detector 11 calculates the logical product of these two signals 9a and 10a to disconnect the output cable (in the case of three phases, the disconnection signal is missing. Including a phase), and a disconnection detection signal 11a is output. The control circuit 7 receives the disconnection detection signal 11a from the disconnection detector 11, and the operation stop operation is performed. If the disconnection (or phase loss) of the output cable is detected only from the difference between the maximum value 8a and the minimum value 8b of the output current signal 6a, there is a risk of erroneous detection at the time of restart due to control switching. On the other hand, in the present embodiment, as described above, even when the minimum value 8b is equal to or less than the predetermined value, it is added to the determination material, and the logical product of the large deviation signal 9a and the decrease signal 10a is taken to obtain an output. The disconnection (or phase loss) of the cable can be reliably detected.
[0016]
FIG. 3 shows a second embodiment of the present invention. In FIG. 3 and the drawings showing the respective embodiments to be described later, the same or equivalent components as those in FIG. 1 are denoted by the same reference numerals as those in FIG. In the present embodiment, an average value detector 12 as an average value detecting means is connected between the rectifier 6 and the rectification deviation detector 9.
[0017]
The average value detector 12 receives the rectified output current signal 6a from the rectifier 6 and calculates and outputs an average value 12a of the output current signal 6a. The current deviation detector 9 receives the average value 12a from the average value detector 12, and corrects (adjusts) the current deviation set value according to the average value 12a. When the load amount changes, the average value of the output current signal 6a changes. Therefore, the average value 12a is calculated, and the current deviation set value is corrected according to the average value 12a, so that the disconnection (or phase loss) of the output cable can be reliably detected even when the load amount changes. be able to.
[0018]
FIG. 4 shows a third embodiment of the present invention. In this embodiment, instead of the current deviation detector 9 shown in FIG. 1, a control abnormality determination unit 13 as a control abnormality determination unit is connected between the current signal calculator 8 and the disconnection detector 11. The control abnormality determination unit 13 includes two output terminals, one output terminal is connected to the disconnection detector 11, and the other output terminal is connected to the control circuit 7.
[0019]
The control abnormality determiner 13 receives the maximum value 8a and the minimum value 8b of the output current signal 6a from the current signal calculator 8, and the difference between the maximum value 8a and the minimum value 8b exceeds a predetermined current deviation set value, When this continues for a certain period, a large deviation continuation signal 13a is output to the disconnection detector 11, and when it does not continue for a certain period, a control abnormality signal 13b is output to the control circuit 7. When the deviation large continuation signal 13a is output, the disconnection detector 11 detects the disconnection (or phase loss) of the output cable by taking the logical product of the deviation large continuation signal 13a and the decrease signal 10a. The operation is stopped by the circuit 7. On the other hand, when the control abnormality signal 13b is output, it is determined that the output cable is not disconnected and that the control is unstable.
[0020]
FIG. 5 shows a fourth embodiment of the present invention. In the present embodiment, instead of the current deviation detector 9 shown in FIG. 1, a ripple period detector 14 as a ripple period detecting means is connected between the current signal calculator 8 and the disconnection detector 11. The ripple period detector 14 includes an output line and an input line, and the output line is connected to the disconnection detector 11 so that the output frequency signal 7b is input from the control circuit 7 through the input line.
[0021]
When the output cable is disconnected (or open phase), the ripple cycle at which the difference between the maximum value 8a and the minimum value 8b of the output current signal 6a is the maximum is less than the cycle of the output frequency (in the case of three phases, the ripple cycle is output Or less than about one third of the frequency period). The ripple period detector 14 receives the maximum value 8a and the minimum value 8b of the output current signal 6a from the current signal calculator 8, and receives the output frequency signal 7b from the control circuit 7. Then, compared with the period of maximum 8a and the minimum value ripple period difference 8b becomes maximum output frequency, when the ripple period becomes to the period of the output frequency and the predetermined value or more, the ripple period detecting signal 14 a is output to the disconnection detector 11. The disconnection detector 11 detects the disconnection (or phase loss) of the output cable by taking the logical product of the ripple period detection signal 14 a and the drop signal 10 a, and the operation is stopped by the control circuit 7.
[0022]
FIG. 6 shows a fifth embodiment of the present invention. In this embodiment, instead of the current deviation detector 9 shown in FIG. 1, a peak arrival time detector 15 as a peak arrival time detector is connected between the current signal calculator 8 and the disconnection detector 11. Yes. The peak arrival time detector 15 includes an output line and an input line. The output line is connected to the disconnection detector 11, and the output frequency signal 7b is input from the control circuit 7 through the input line.
[0023]
When the output cable is disconnected (or lost phase), the time from the maximum value 8a to the minimum value 8b of the output current signal 6a is less than the cycle of the output frequency. The peak arrival time detector 15 receives the maximum value 8a and the minimum value 8b of the output current signal 6a from the current signal calculator 8, and receives the output frequency signal 7b from the control circuit 7. Then, compared with the period of time and the output frequency from the maximum value 8a until a minimum value 8b, the time from the maximum value 8a until a minimum value 8b reaches to the period of the output frequency and the predetermined value or more Sometimes, the peak arrival time detection signal 15 a is output to the disconnection detector 11. The disconnection detector 11 detects the disconnection (or phase loss) of the output cable by taking the logical product of the peak arrival time detection signal 15a and the decrease signal 10a, and the control circuit 7 stops the operation.
[0024]
FIG. 7 shows a sixth embodiment of the present invention. In this embodiment, a plurality of electric motors 3, 3,... Are driven as loads.
[0025]
Even when driving a plurality of electric motors 3, 3,..., The output cable disconnection can be detected because the minimum value 8b of the output current signal 6a decreases when the output cable is disconnected.
[0026]
【The invention's effect】
As described above, according to the first to third aspects of the present invention, when the output cable is disconnected, this can be reliably detected and the operation can be stopped, and the reliability can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram of a power conversion apparatus according to a first embodiment of the present invention.
FIG. 2 is an output current signal waveform diagram for explaining a control operation when the output cable is disconnected in the first embodiment.
FIG. 3 is a block diagram of a second exemplary embodiment of the present invention.
FIG. 4 is a block diagram of a third embodiment of the present invention.
FIG. 5 is a block diagram of a fourth embodiment of the present invention.
FIG. 6 is a block diagram of a fifth embodiment of the present invention.
FIG. 7 is a block diagram of a sixth embodiment of the present invention.
FIG. 8 is a block diagram of a conventional power conversion device.
[Explanation of symbols]
2 Inverter circuit 3 Electric motor 5 Current transformer (current detection means)
6 Rectifier (rectifying means)
7 Control circuit (control means)
8 Current signal calculator (current signal calculator)
9 Current deviation detector (Current deviation detection means)
10 Current level detector (current level detection means)
11 Disconnection detector (disconnection detection means)
12 Average value detector (mean value detection means)
13 Control abnormality judgment device (control abnormality judgment means)
14 Ripple period detector (ripple period detection means)
15 Peak arrival time detector (peak arrival time detection means)

Claims (3)

出力電流を検出する電流検出手段と、この電流検出手段で検出した出力電流信号を整流する整流手段と、この整流した出力電流信号の最大値及び最小値を演算する電流信号演算手段と、この電流信号演算手段からの最大値と最小値の差が予め定めた電流偏差設定値を一定期間継続して超えたときは偏差大継続信号を出力し、一定期間継続しないときは制御異常信号を出力する制御異常判断手段と、前記最小値が予め定めた所定値以下となったとき低下信号を出力する電流レベル検出手段と、前記偏差大継続信号と前記低下信号の論理積をとって断線検出信号を出力する断線検出手段と、前記断線検出信号により装置動作を停止する制御手段とを有することを特徴とする電力変換装置。  Current detection means for detecting the output current, rectification means for rectifying the output current signal detected by the current detection means, current signal calculation means for calculating the maximum value and the minimum value of the rectified output current signal, and the current When the difference between the maximum value and the minimum value from the signal calculation means exceeds the preset current deviation setting value for a certain period, a large deviation continuation signal is output, and when it does not continue for a certain period, a control abnormality signal is output. Control abnormality determination means, current level detection means for outputting a decrease signal when the minimum value is equal to or less than a predetermined value, and a disconnection detection signal obtained by ANDing the deviation large continuation signal and the decrease signal A power conversion apparatus comprising: a disconnection detection means for outputting; and a control means for stopping the operation of the apparatus by the disconnection detection signal. 出力電流を検出する電流検出手段と、この電流検出手段で検出した出力電流信号を整流する整流手段と、この整流した出力電流信号の最大値及び最小値を演算する電流信号演算手段と、前記出力電流信号の最大値から最小値までの時間と出力周波数の周期とを比較し、前記最大値から最小値までの時間が前記出力周波数の周期に対し所定値以上となったときピーク到達時間検出信号を出力するピーク到達時間検出手段と、前記最小値が予め定めた所定値以下となったとき低下信号を出力する電流レベル検出手段と、前記ピーク到達時間検出信号と前記低下信号の論理積をとって断線検出信号を出力する断線検出手段と、前記断線検出信号により装置動作を停止する制御手段とを有することを特徴とする電力変換装置。  Current detection means for detecting an output current; rectification means for rectifying an output current signal detected by the current detection means; current signal calculation means for calculating a maximum value and a minimum value of the rectified output current signal; and the output Comparing the time from the maximum value to the minimum value of the current signal with the cycle of the output frequency, and when the time from the maximum value to the minimum value is equal to or greater than the predetermined value with respect to the cycle of the output frequency, the peak arrival time detection signal A logical product of the peak arrival time detection signal and the decrease signal, a peak level arrival time detection means for outputting the current value, a current level detection means for outputting a decrease signal when the minimum value falls below a predetermined value. And a control means for stopping the operation of the apparatus in response to the disconnection detection signal. 負荷として複数台の電動機を駆動することを特徴とする請求項１または２に記載の電力変換装置。The power converter according to claim 1 or 2 , wherein a plurality of electric motors are driven as a load.
JP2002106639A 2002-04-09 2002-04-09 Power converter Expired - Lifetime JP3961868B2 (en)

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