JP2010071776A - Device for detecting alternating current - Google Patents

Device for detecting alternating current Download PDF

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JP2010071776A
JP2010071776A JP2008238936A JP2008238936A JP2010071776A JP 2010071776 A JP2010071776 A JP 2010071776A JP 2008238936 A JP2008238936 A JP 2008238936A JP 2008238936 A JP2008238936 A JP 2008238936A JP 2010071776 A JP2010071776 A JP 2010071776A
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voltage
current transformer
current
converter
voltage dividing
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JP5135138B2 (en
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Tomohisa Okami
智久 狼
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Toshiba Mitsubishi Electric Industrial Systems Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for detecting an alternating current which secures coordination between overvoltage protection of an A/D converter and overvoltage protection of other equipment connected to the secondary circuit of an auxiliary current transformer and has high reliability as a whole. <P>SOLUTION: The device includes a current transformer 1 for detecting the alternating current, the auxiliary current transformer 2 to which a secondary output of the current transformer 1 is input, two voltage dividing resistors 3 and 4 which are connected in series so as to convert a secondary current obtained from the secondary output of the auxiliary current transformer 2 into voltage, the A/D converter 5 to which the voltage applied on the voltage dividing resistor 4 on one side is inputted, overvoltage suppressing means 7 and 8 which are connected in parallel to the input of the A/D converter 5 and which are brought to a state of continuity on impression of a first prescribed voltage and hold this first prescribed voltage, and an overcurrent bypass means 6 which is connected in parallel to the secondary output of the auxiliary current transformer 2 and starts electrification on impression of a second prescribed voltage being higher than the first. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は交流電流検出装置に係り、特に交流母線の電流を検出してデジタル信号に変換する機能を有する交流電流検出装置に関する。   The present invention relates to an alternating current detection device, and more particularly to an alternating current detection device having a function of detecting a current of an alternating current bus and converting it into a digital signal.

従来から、比較的容量の大きい交流母線の電流を検出するための交流電流検出装置として、変流器によって検出された交流電流信号を補助変流器によって適切な電流レベルに変換し、更に分圧抵抗器等によって電圧信号に変換し、この電圧信号を例えばＡ／Ｄ変換器でデジタル信号に変換する方式の交流電流検出装置が採用されていた。このＡ／Ｄ変換器の出力をマイコン等に与えることによって、例えばマイコンによる変換装置等の制御に利用することができる。このような交流電流検出装置に対して、交流母線に過大電流が流れたときの過電圧を保護するために変流器の２次側に過電圧保護回路を設ける提案が為されている（例えば特許文献１参照。）。
特開２００３−２７０２７３号公報（第２−３頁、図１） Conventionally, as an AC current detection device for detecting a current of a relatively large capacity AC bus, an AC current signal detected by a current transformer is converted to an appropriate current level by an auxiliary current transformer, and further divided. An AC current detection device of a type that converts a voltage signal with a resistor or the like and converts the voltage signal into a digital signal with an A / D converter, for example, has been adopted. By giving the output of the A / D converter to a microcomputer or the like, it can be used for controlling a conversion device or the like by the microcomputer, for example. For such an AC current detection device, a proposal has been made to provide an overvoltage protection circuit on the secondary side of the current transformer in order to protect the overvoltage when an excessive current flows through the AC bus (for example, Patent Documents). 1).
JP 2003-270273 A (page 2-3, FIG. 1)

特許文献１に示されている手法は、Ａ／Ｄ変換器の過電圧保護と補助変流器の２次回路全体の過電圧保護を一つの過電圧保護回路で同時に行なおうとするものである。しかるに、電子化されたＡ／Ｄ変換器の過電圧保護については、その保護レベルの精度、信頼性が極めて重要であるのに対し、補助変流器の２次回路に接続される抵抗器などの他の機器の保護レベルは比較的ラフであっても良い。   The technique disclosed in Patent Document 1 intends to simultaneously perform overvoltage protection of the A / D converter and overvoltage protection of the entire secondary circuit of the auxiliary current transformer with one overvoltage protection circuit. However, for the overvoltage protection of electronic A / D converters, the accuracy and reliability of the protection level are extremely important, whereas resistors such as resistors connected to the secondary circuit of the auxiliary current transformer are used. The protection level of other devices may be relatively rough.

また、一般的にＡ／Ｄ変換器の入力電圧を調整可能とするために、分圧抵抗器には分圧比の変更が可能な可変抵抗器が用いられる。従って、Ａ／Ｄ変換器の過電圧保護と補助変流器の２次回路全体の過電圧保護を一つの過電圧保護回路で行うと、分圧比を調整した結果Ａ／Ｄ変換器の過電圧保護レベルも変わり、Ａ／Ｄ変換器の過電圧保護が成り立たなくなったり、不要に低いレベルでの保護動作となって正常な動作に支障を来たす恐れがあった。   In general, in order to be able to adjust the input voltage of the A / D converter, a variable resistor capable of changing a voltage dividing ratio is used as the voltage dividing resistor. Therefore, if the overvoltage protection of the A / D converter and the overvoltage protection of the secondary circuit of the auxiliary current transformer are performed with one overvoltage protection circuit, the overvoltage protection level of the A / D converter also changes as a result of adjusting the voltage division ratio. The overvoltage protection of the A / D converter may not be realized, or the protection operation may be performed at an unnecessarily low level, thereby hindering normal operation.

本発明は上記の課題を鑑みて為されたもので、Ａ／Ｄ変換器の過電圧保護と補助変流器の２次回路に接続される他の機器の過電圧保護間の協調をとり、全体として信頼性の高い交流電流検出装置を提供することを目的とする。   The present invention has been made in view of the above-mentioned problems, and cooperates between the overvoltage protection of the A / D converter and the overvoltage protection of other devices connected to the secondary circuit of the auxiliary current transformer as a whole. An object of the present invention is to provide a highly reliable alternating current detecting device.

上記目的を達成するために、本発明の交流電流検出装置は、交流電流検出用の変流器と、この変流器の２次出力を入力とする補助変流器と、前記補助変流器の２次出力から得られる２次電流を電圧に変換するために直列接続された２つの分圧抵抗器と、前記分圧抵抗器のうち一方の分圧抵抗器に印加される電圧を入力とするＡ／Ｄ変換器と、前記Ａ／Ｄ変換器の入力に並列に接続され、第１の所定電圧が印加されると導通状態となってこの第１の所定電圧を保持する過電圧抑制手段と、補助変流器の２次出力と並列に接続され、前記第１の所定電圧より高い第２の所定電圧が印加されると通電を開始する過電流バイパス手段とを具備したことを特徴としている。   In order to achieve the above object, an AC current detection device according to the present invention includes a current transformer for AC current detection, an auxiliary current transformer that receives a secondary output of the current transformer, and the auxiliary current transformer. Two voltage dividing resistors connected in series to convert a secondary current obtained from the secondary output into a voltage, and a voltage applied to one of the voltage dividing resistors as an input. An A / D converter that is connected in parallel to the input of the A / D converter, and an overvoltage suppressing unit that is in a conductive state when the first predetermined voltage is applied and holds the first predetermined voltage. And an overcurrent bypass means connected in parallel with the secondary output of the auxiliary current transformer and starting energization when a second predetermined voltage higher than the first predetermined voltage is applied. .

本発明によれば、Ａ／Ｄ変換器の過電圧保護と補助変流器の２次回路に接続される他の機器の過電圧保護間の協調をとり、全体として信頼性の高い交流電流検出装置を提供することが可能となる。   According to the present invention, the overvoltage protection of the A / D converter and the overvoltage protection of other devices connected to the secondary circuit of the auxiliary current transformer are coordinated to provide a highly reliable alternating current detection device as a whole. It becomes possible to provide.

以下、図面を参照して本発明の実施例を説明する。   Embodiments of the present invention will be described below with reference to the drawings.

図１は本発明実施例１に係る交流電流検出装置のブロック構成図である。   FIG. 1 is a block diagram of an alternating current detection device according to Embodiment 1 of the present invention.

図１において、交流電流検出装置１０は、交流母線に流れる電流をデジタル信号に変換して制御装置等に設けられたマイコン２０に与える。以下交流電流検出装置１０の内部構成について説明する。   In FIG. 1, an alternating current detection device 10 converts a current flowing in an alternating current bus into a digital signal and supplies the digital signal to a microcomputer 20 provided in a control device or the like. Hereinafter, the internal configuration of the AC current detection device 10 will be described.

変流器１は交流母線の電流を検出し、補助変流器２によって適切な電流レベルに変換する。そして補助変流器２の２次巻線出力と並列に直列接続された分圧抵抗器３及び分圧抵抗器４を接続し、分圧抵抗器４の両端の電圧をＡ／Ｄ変換器５の入力に与える。Ａ／Ｄ変換器５は、分圧抵抗器４に印加される電圧をデジタル信号に変換し、装置の外部に接続されたマイコン２０にこの信号を与える。   The current transformer 1 detects the current of the AC bus and converts it to an appropriate current level by the auxiliary current transformer 2. Then, a voltage dividing resistor 3 and a voltage dividing resistor 4 connected in series with the secondary winding output of the auxiliary current transformer 2 are connected in parallel, and the voltage across the voltage dividing resistor 4 is converted to an A / D converter 5. Give to the input. The A / D converter 5 converts the voltage applied to the voltage dividing resistor 4 into a digital signal, and gives this signal to the microcomputer 20 connected to the outside of the apparatus.

また、Ａ／Ｄ変換器５の過電圧防止手段としてツェナーダイオード７、８を互いに逆向きに直列接続した過電圧防止回路を分圧抵抗４と並列に接続し、更に、補助変流器２の２次側の過電流バイパス手段として電圧依存性抵抗器６を補助変流器２の２次巻線と並列に接続している。   Further, as an overvoltage prevention means of the A / D converter 5, an overvoltage prevention circuit in which Zener diodes 7 and 8 are connected in series in opposite directions is connected in parallel with the voltage dividing resistor 4, and the secondary current of the auxiliary current transformer 2 is further connected. A voltage-dependent resistor 6 is connected in parallel with the secondary winding of the auxiliary current transformer 2 as overcurrent bypass means on the side.

上記の回路構成においては、例えば、交流母線も主回路電流が１０００Ａ／ｐｕでありＡ／Ｄ変換器５の電圧入力範囲が±１０Ｖであるとき、１０００Ａ／ｐｕの電流信号を３〜５Ｖ／ｐｕ程度の電圧信号に変換し、２〜３ｐｕ程度の電流値までマイコン６に入力が可能なよう補助変流器２、分圧抵抗器３及び分圧抵抗器４の定格を選定する。   In the above circuit configuration, for example, when the main circuit current of the AC bus is 1000 A / pu and the voltage input range of the A / D converter 5 is ± 10 V, the current signal of 1000 A / pu is 3 to 5 V / pu. The ratings of the auxiliary current transformer 2, the voltage dividing resistor 3, and the voltage dividing resistor 4 are selected so that the voltage can be converted into a voltage signal of about 2 and the current value of about 2 to 3 pu can be input to the microcomputer 6.

以下、図２を参照して実施例１の動作の詳細について説明する。   The details of the operation of the first embodiment will be described below with reference to FIG.

図２は過電圧防止回路及び電圧依存性抵抗器のＩ−Ｖ特性図である。図２（ｂ）に示したように、ツェナーダイオード７、８による過電圧防止回路に印加される電圧をＶ１、通電電流をＩ１としたときのＩ１−Ｖ１特性は、図２（ａ）に示したようにＶ１が或る電圧閾値Ｖｔｈｒ１以上となったとき、または電圧閾値−Ｖｔｈｒ１以下となったとき電圧のクリップが開始される特性となっている。同様に、電圧依存性抵抗器に印加される電圧をＶ２、通電電流をＩ２としたときのＩ２−Ｖ２特性は、Ｖ２が或る電圧閾値Ｖｔｈｒ２以上となったとき、または電圧閾値−Ｖｔｈｒ２以下となったとき電圧のクリップが開始される特性となる。これらの特性を数式で表すと以下となる。   FIG. 2 is an IV characteristic diagram of the overvoltage prevention circuit and the voltage dependent resistor. As shown in FIG. 2B, the I1-V1 characteristic when the voltage applied to the overvoltage prevention circuit by the Zener diodes 7 and 8 is V1 and the conduction current is I1 is shown in FIG. Thus, when V1 becomes equal to or higher than a certain voltage threshold value Vthr1, or when it becomes equal to or lower than the voltage threshold value −Vthr1, the voltage clipping is started. Similarly, the I2-V2 characteristic when the voltage applied to the voltage-dependent resistor is V2 and the energization current is I2 is as follows: V2 becomes a voltage threshold value Vthr2 or more, or voltage threshold value −Vthr2 or less. When this happens, voltage clipping starts. These characteristics are expressed as follows:

｜Ｖ１｜＜｜Ｖｔｈｒ１｜のとき、 Ｉ１≒０Ａ ・・・（１）
｜Ｖ１｜＞｜Ｖｔｈｒ１｜のとき、 Ｉ１≫０Ａ ・・・（２）
｜Ｖ２｜＜｜Ｖｔｈｒ２｜のとき、 Ｉ２≒０Ａ ・・・（３）
｜Ｖ２｜＞｜Ｖｔｈｒ２｜のとき、 Ｉ２≫０Ａ ・・・（４）
｜Ｖｔｈｒ２｜＞｜Ｖｔｈｒ１｜ ・・・（５）
このような保護特性を有する交流電流検出装置１０において、交流母線の短絡などによって補助変流器２の２次巻線に過電流が発生したとき、以下の３段階に従って現象が進展する。 When | V1 | <| Vthr1 |, I1≈0A (1)
When | V1 |> | Vthr1 |, I1 >> 0A (2)
When | V2 | <| Vthr2 |, I2≈0A (3)
When | V2 |> | Vthr2 |, I2 >> 0A (4)
| Vthr2 |> | Vthr1 | (5)
In the AC current detecting device 10 having such protection characteristics, when an overcurrent is generated in the secondary winding of the auxiliary current transformer 2 due to a short circuit of the AC bus, the phenomenon progresses according to the following three stages.

第１段階は、分圧抵抗４の両端電圧がＶｔｈｒ１に上昇するまでの状態であり、この状態ではツェナーダイオード７、８は非導通状態である。また、電圧依存性抵抗器６もほとんど電流が流れていない状態であり、過電流となる前の段階である。   The first stage is a state until the voltage across the voltage dividing resistor 4 rises to Vthr1, and in this state, the Zener diodes 7 and 8 are nonconductive. The voltage-dependent resistor 6 is also in a state where almost no current flows, and is a stage before an overcurrent occurs.

第２段階は、分圧抵抗４の両端電圧がＶｔｈｒ１に達した後、分圧抵抗４と分圧抵抗３の全体に掛かる電圧がＶｔｈｒ２に上昇するまでの状態であり、この状態ではツェナーダイオード７、８は導通状態となり分圧抵抗４の両端電圧をＶｔｈｒ１に保持してＡ／Ｄ変換器６の過電圧を防止している。このときには未だ電圧依存性抵抗器６にはほとんど電流が流れていない。   The second stage is a state in which the voltage applied across the voltage dividing resistor 4 and the voltage dividing resistor 3 rises to Vthr2 after the voltage across the voltage dividing resistor 4 reaches Vthr1, and in this state, the Zener diode 7 , 8 are in a conducting state, and the voltage across the voltage dividing resistor 4 is held at Vthr1 to prevent overvoltage of the A / D converter 6. At this time, almost no current flows through the voltage-dependent resistor 6.

第３段階は、分圧抵抗３と分圧抵抗４の全体に掛かる電圧がＶｔｈｒ２以上に上昇した状態であり、この状態ではツェナーダイオード７、８は導通状態、電圧依存性抵抗器６も電流を通流する状態となる。ツェナーダイオード７、８が導通状態のまま分圧抵抗４の両端電圧をＶｔｈｒ１に保持する一方、電圧依存性抵抗器６も電流を通流する状態となり分圧抵抗３、４の両端電圧をＶｔｈｒ２の値に実質的に保持する。ここで実質的とは、通電する電流の増大に伴ってＶ２は上昇するが、その程度が僅かであるということである。これによって分圧抵抗３、４及びツェナーダイオード７、８に流入する電流が一定値以上に増大することを制限し、過負荷による分圧抵抗３、４及びツェナーダイオード７、８の焼損を防止することが可能となる。   The third stage is a state in which the voltage applied to the whole of the voltage dividing resistor 3 and the voltage dividing resistor 4 has risen to Vthr2 or more. In this state, the Zener diodes 7 and 8 are in a conducting state, and the voltage dependent resistor 6 also conducts current. It will be in a state to flow. While the Zener diodes 7 and 8 are kept conductive, the voltage across the voltage dividing resistor 4 is held at Vthr1, while the voltage-dependent resistor 6 is also in a state where current flows and the voltage across the voltage dividing resistors 3 and 4 is set to Vthr2. Hold substantially on the value. Here, “substantially” means that V2 rises with increasing current to be energized, but its degree is slight. This restricts the current flowing into the voltage dividing resistors 3 and 4 and the Zener diodes 7 and 8 from increasing to a certain value or more, and prevents the voltage dividing resistors 3 and 4 and the Zener diodes 7 and 8 from being burned by overload. It becomes possible.

以上説明したように、Ａ／Ｄ変換器５の入力電圧がその耐電圧以下となるよう過電圧防止回路におけるＶｔｈｒ１を選定し、分圧抵抗３、４及び過電圧防止回路で発生する損失が許容損失以下となるよう電圧依存性抵抗器のＶｔｈｒ２を選定することによって協調のとれた信頼性の高い過電圧保護を実現することが可能となる。   As described above, Vthr1 in the overvoltage prevention circuit is selected so that the input voltage of the A / D converter 5 is lower than the withstand voltage, and the loss generated in the voltage dividing resistors 3 and 4 and the overvoltage prevention circuit is less than the allowable loss. By selecting Vthr2 of the voltage-dependent resistor so as to be, it becomes possible to realize coordinated and reliable overvoltage protection.

この実施例における電圧依存性抵抗器６の具体例として、ＺＮＲ（登録商標）を適用することができる。一般的にツェナーダイオードの許容損失と比べて、ＺＮＲは許容損失が大きいため、過電流のバイパス動作で焼損することなく、本発明の保護機能を満足することができる。   As a specific example of the voltage dependent resistor 6 in this embodiment, ZNR (registered trademark) can be applied. In general, the ZNR has a large allowable loss as compared with the allowable loss of the Zener diode, so that the protection function of the present invention can be satisfied without being burned out by an overcurrent bypass operation.

図３は本発明実施例２に係る交流電流検出装置のブロック構成図である。この実施例２の各部について、図１の本発明の実施例１に係る交流電流検出装置のブロック構成図の各部と同一部分は同一符号で示し、その説明は省略する。この実施例２が実施例１と異なる点は、交流電流検出装置１０Ａの過電流バイパス手段として実施例１における電圧依存性抵抗器６に代え、一定電圧が印加されると導通状態となる電圧依存性素子６Ａを用いた点である。   FIG. 3 is a block diagram of an AC current detection apparatus according to Embodiment 2 of the present invention. In the second embodiment, the same parts as those in the block diagram of the AC current detecting apparatus according to the first embodiment of the present invention shown in FIG. The difference between the second embodiment and the first embodiment is that the overcurrent bypass means of the AC current detecting device 10A is replaced with the voltage-dependent resistor 6 in the first embodiment, and becomes a conductive state when a constant voltage is applied. This is a point using the conductive element 6A.

以下、図４を参照して実施例２の動作の詳細について説明する。   Details of the operation of the second embodiment will be described below with reference to FIG.

図４は電圧依存性素子６ＡのＩ−Ｖ特性図である。図４（ｂ）に示したように、電圧依存性素子６Ａに印加される電圧をＶ３、通電電流をＩ３としたとき、Ｉ３−Ｖ３特性は図４（ａ）に示したようにＶ３が或る電圧閾値Ｖｔｈｒ３以上となったとき、または電圧閾値−Ｖｔｈｒ３以下となったときそのインピーダンスが極端に低下して電圧が低下する特性となる。すなわち、
｜Ｖ３｜＜｜Ｖｔｈｒ３｜のとき、Ｉ３≒０Ａ ・・・（６）
｜Ｖ３｜＞｜Ｖｔｈｒ３｜となったとき、Ｉ３≫０Ａ・・・（７）
（ただし電圧依存性素子６Ａの導通後、Ｖ３≒０Ｖ）
また、ツェナーダイオード７、８の電圧閾値Ｖｔｈｒ１と電圧依存性素子６Ａの電圧閾値Ｖｔｈｒ３は、以下の関係を有する。 FIG. 4 is an IV characteristic diagram of the voltage dependent element 6A. As shown in FIG. 4B, when the voltage applied to the voltage dependent element 6A is V3 and the energization current is I3, the I3-V3 characteristic is V3 as shown in FIG. 4A. When the voltage threshold Vthr3 is equal to or higher than the voltage threshold Vthr3 or lower, the impedance is extremely lowered and the voltage is lowered. That is,
When | V3 | <| Vthr3 |, I3≈0A (6)
When | V3 |> | Vthr3 |, I3 >> 0A (7)
(However, after the conduction of the voltage dependent element 6A, V3≈0V)
The voltage threshold value Vthr1 of the Zener diodes 7 and 8 and the voltage threshold value Vthr3 of the voltage dependent element 6A have the following relationship.

｜Ｖｔｈｒ３｜＞｜Ｖｔｈｒ１｜ ・・・（８）
このような保護特性を有する交流電流検出装置１０Ａにおいて、交流母線の短絡などによって補助変流器２の２次巻線に過電流が発生したとき、以下の３段階に従って現象が進展する。 | Vthr3 |> | Vthr1 | (8)
In the AC current detection device 10A having such protection characteristics, when an overcurrent is generated in the secondary winding of the auxiliary current transformer 2 due to a short circuit of the AC bus, the phenomenon progresses according to the following three stages.

第１段階は、分圧抵抗４の両端電圧がＶｔｈｒ１に上昇するまでの状態であり、この状態ではツェナーダイオード７、８および電圧依存性素子６Ａは非導通状態であり、過電流となる前の段階である。   The first stage is a state until the voltage across the voltage dividing resistor 4 rises to Vthr1, and in this state, the Zener diodes 7 and 8 and the voltage dependent element 6A are in a non-conducting state, and before the overcurrent occurs. It is a stage.

第２段階は、分圧抵抗４の両端電圧がＶｔｈｒ１に達した後、分圧抵抗３と分圧抵抗４の全体に掛かる電圧がＶｔｈｒ３に上昇するまでの状態であり、この状態ではツェナーダイオード７、８は導通状態となり分圧抵抗４の両端電圧をＶｔｈｒ１に保持し過電圧の出力を防止している。電圧依存性素子６Ａはほとんど電流を流していない状態である。   The second stage is a state in which the voltage applied across the voltage dividing resistor 3 and the voltage dividing resistor 4 rises to Vthr3 after the voltage across the voltage dividing resistor 4 reaches Vthr1, and in this state, the Zener diode 7 , 8 are in a conductive state, and the voltage across the voltage dividing resistor 4 is held at Vthr1 to prevent overvoltage output. The voltage dependent element 6A is in a state where almost no current flows.

第３段階は、分圧抵抗３と分圧抵抗４の全体に掛かる電圧がＶｔｈｒ３以上に上昇した状態であり、この状態となると電圧依存性素子６Ａは導通状態となる。電圧依存性素子６Ａは導通状態となると分圧抵抗３、４の両端電圧は実質的にゼロとなる。ここで実質的とは、この分圧抵抗３、４の両端電圧が電圧依存性素子６Ａのオン電圧まで低下するということである。これにより分圧抵抗４の両端電圧がＶｔｈｒ１以下となりツェナーダイオード７、８は非導通状態となる。過電流状態が続く場合には、電圧依存性素子６Ａは導通状態を継続し過電流を還流し、その結果、過負荷による分圧抵抗３、４及びツェナーダイオード７、８の焼損を防止することが可能となる。   The third stage is a state in which the voltage applied to the entire voltage dividing resistor 3 and the voltage dividing resistor 4 has risen to Vthr3 or more. In this state, the voltage-dependent element 6A becomes conductive. When the voltage dependent element 6A becomes conductive, the voltage across the voltage dividing resistors 3 and 4 becomes substantially zero. Here, “substantially” means that the voltage across the voltage dividing resistors 3 and 4 is reduced to the ON voltage of the voltage-dependent element 6A. As a result, the voltage across the voltage dividing resistor 4 becomes Vthr1 or less, and the Zener diodes 7 and 8 are turned off. When the overcurrent state continues, the voltage-dependent element 6A continues to conduct and recirculates the overcurrent, thereby preventing the voltage dividing resistors 3 and 4 and the Zener diodes 7 and 8 from being burned out due to overload. Is possible.

以上から分かるように電圧依存性素子６Ａが導通状態となったとき、交流電流検出値は０ｐｕ程度になってしまうので、正常な制御ができなくなる恐れがある。従ってこの実施例２においては、交流母線の異常を検出する交流過電流の整定値を超える過電流となって制御の対象となる装置の保護動作が働いた後に電圧依存性素子６Ａが導通するようにＶｔｈｒ３を選定しておく必要がある。   As can be seen from the above, when the voltage-dependent element 6A becomes conductive, the AC current detection value becomes about 0 pu, and thus there is a possibility that normal control cannot be performed. Therefore, in the second embodiment, the voltage dependent element 6A is turned on after the overcurrent exceeding the set value of the AC overcurrent that detects the AC bus abnormality is detected and the protection operation of the device to be controlled is activated. It is necessary to select Vthr3.

本実施例の利点は、過電流入力時に電圧依存性素子６Ａは電圧を保持しないため分圧抵抗３、４及び電圧依存性素子６Ａに要求される許容損失が小さくなり、従って回路を小型化できることである。   The advantage of this embodiment is that the voltage-dependent element 6A does not hold a voltage when an overcurrent is input, so that the allowable loss required for the voltage dividing resistors 3 and 4 and the voltage-dependent element 6A is reduced, and thus the circuit can be reduced in size. It is.

以上説明したようにこの実施例２においても、Ａ／Ｄ変換器５の入力電圧が耐電圧以下となるよう過電圧防止回路におけるＶｔｈｒ１を選択し、分圧抵抗３、４及び過電圧防止回路で発生する損失が許容損失以下となるよう電圧依存性素子のＶｔｈｒ３を選定することによって協調のとれた信頼性の高い過電圧保護を実現することが可能となる。   As described above, also in the second embodiment, Vthr1 in the overvoltage prevention circuit is selected so that the input voltage of the A / D converter 5 is equal to or lower than the withstand voltage, and is generated in the voltage dividing resistors 3 and 4 and the overvoltage prevention circuit. By selecting Vthr3 of the voltage dependent element so that the loss is equal to or less than the allowable loss, it is possible to realize coordinated and reliable overvoltage protection.

尚、電圧依存性素子６Ａの具体例としては双方向性のサイダック（登録商標）が挙げられる。   A specific example of the voltage-dependent element 6A is a bidirectional Sidac (registered trademark).

本発明の実施例１に係る交流電流検出装置のブロック構成図。The block block diagram of the alternating current detection apparatus which concerns on Example 1 of this invention. 過電圧防止回路及び電圧依存性抵抗器のＩ−Ｖ特性図。The IV characteristic figure of an overvoltage prevention circuit and a voltage dependence resistor. 本発明の実施例２に係る交流電流検出装置のブロック構成図。The block block diagram of the alternating current detection apparatus which concerns on Example 2 of this invention. 電圧依存性素子のＩ−Ｖ特性図。The IV characteristic figure of a voltage dependence element.

符号の説明Explanation of symbols

１ 変流器
２ 補助変流器
３、４ 分圧抵抗器
５ Ａ／Ｄ変換器
６ 電圧依存性抵抗器
６Ａ 電圧依存性素子
７、８ ツェナーダイオード
１０、１０Ａ 交流電流検出装置
２０ マイコン DESCRIPTION OF SYMBOLS 1 Current transformer 2 Auxiliary current transformer 3, 4 Voltage dividing resistor 5 A / D converter 6 Voltage dependence resistor 6A Voltage dependence element 7, 8 Zener diode 10, 10A AC current detection apparatus 20 Microcomputer

Claims (3)

交流電流検出用の変流器と、
この変流器の２次出力を入力とする補助変流器と、
前記補助変流器の２次出力から得られる２次電流を電圧に変換するために直列接続された２つの分圧抵抗器と、
前記分圧抵抗器のうち一方の分圧抵抗器に印加される電圧を入力とするＡ／Ｄ変換器と、
前記Ａ／Ｄ変換器の入力に並列に接続され、第１の所定電圧が印加されると導通状態となってこの第１の所定電圧を保持する過電圧抑制手段と、
補助変流器の２次出力と並列に接続され、前記第１の所定電圧より高い第２の所定電圧が印加されると通電を開始する過電流バイパス手段と
を具備したことを特徴とする交流電流検出装置。 A current transformer for AC current detection;
An auxiliary current transformer that receives the secondary output of the current transformer,
Two voltage dividing resistors connected in series to convert a secondary current obtained from the secondary output of the auxiliary current transformer into a voltage;
An A / D converter having a voltage applied to one of the voltage dividing resistors as an input; and
An overvoltage suppressing means connected in parallel to the input of the A / D converter, and becomes conductive when a first predetermined voltage is applied, and holds the first predetermined voltage;
And an overcurrent bypass means connected in parallel with the secondary output of the auxiliary current transformer and starting energization when a second predetermined voltage higher than the first predetermined voltage is applied. Current detection device. 前記過電流バイパス手段は、
前記第２の所定電圧が印加されると導通状態となり且つ前記第２の所定電圧を実質的に保持する特性を有する電圧依存性抵抗器であることを特徴とする請求項１に記載の交流電流検出装置。 The overcurrent bypass means includes
The alternating current according to claim 1, wherein the alternating current is a voltage-dependent resistor that has a characteristic of becoming conductive when the second predetermined voltage is applied and substantially holding the second predetermined voltage. Detection device. 前記過電流バイパス手段は、
前記第２の所定電圧が印加されると導通状態となり且つその両端電圧を実質的にゼロとするような特性を有する電圧依存性素子であることを特徴とする請求項１に記載の交流電流検出装置。 The overcurrent bypass means includes
2. The AC current detection according to claim 1, wherein the AC current detection element is a voltage-dependent element that has a characteristic of becoming conductive when the second predetermined voltage is applied and having a voltage at both ends substantially zero. apparatus.
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CN109270319A (en) * 2018-11-29 2019-01-25 西安高研电器有限责任公司 A kind of multi-tap voltage transformer and its production, adjustment method

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