JPH0155422B2 - - Google Patents
Info
- Publication number
- JPH0155422B2 JPH0155422B2 JP13445280A JP13445280A JPH0155422B2 JP H0155422 B2 JPH0155422 B2 JP H0155422B2 JP 13445280 A JP13445280 A JP 13445280A JP 13445280 A JP13445280 A JP 13445280A JP H0155422 B2 JPH0155422 B2 JP H0155422B2
- Authority
- JP
- Japan
- Prior art keywords
- capacitor
- current
- operational amplifier
- value
- resistor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000003990 capacitor Substances 0.000 claims description 18
- 238000004804 winding Methods 0.000 description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
- G01R15/183—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measurement Of Current Or Voltage (AREA)
Description
この発明は、演算増幅器を用いた交流入力用電
流電圧変換器に関するものである。
第１図は従来の電流電圧変換器をカレント・ト
ランスに接続した一例を示す。この図で、１はカ
レント・トランスで、鉄心２に一次巻線３と二次
巻線４とが施される。５はコンデンサ、６は演算
増幅器、７はその反転入力側に出力側からフイー
ドバツクを行う抵抗器である。コンデンサ５は演
算増幅器６の反転入力側が直接二次巻線４に接続
されると、その入力が二次巻線４で接地された形
となり、直流でのフイードバツクが極端に減少
し、演算増幅器６の出力の直流安定度が悪くなる
ので、それを防止するため挿入されたものであ
る。８は出力端子である。
測定に際しては、一次巻線３に被測定電流Ｉを
流す。そして出力端子８に得られる出力電圧Ｖか
ら被測定電流Ｉを求める。
さて、第１図の回路において、その伝達特性を
演算増幅器６の利得が充分大きいとして求めると
下記第(1)式のようになる。
Ｖ＝−R1／Ｎ・Ｉ・１／（１−１／ω2LC−ｊｒ／ωL）
…(1)
ここで、Ｎ：一次、二次巻線３，４の巻線比
R1：抵抗器７の抵抗値
ω：角速度
Ｌ：二次巻線４のインダクタンス
Ｃ：コンデンサ５のキヤパシタンス
ｒ：二次巻線４の内部抵抗値
第(1)式からわかるように、低周波域の特性は、
The present invention relates to an AC input current-voltage converter using an operational amplifier. FIG. 1 shows an example of a conventional current-voltage converter connected to a current transformer. In this figure, 1 is a current transformer, and a primary winding 3 and a secondary winding 4 are provided on an iron core 2. 5 is a capacitor, 6 is an operational amplifier, and 7 is a resistor for providing feedback from the output side to its inverting input side. When the inverting input side of the operational amplifier 6 of the capacitor 5 is directly connected to the secondary winding 4, the input is grounded by the secondary winding 4, and the feedback in direct current is extremely reduced. This was inserted to prevent the DC stability of the output from worsening. 8 is an output terminal. During measurement, a current to be measured I is passed through the primary winding 3. Then, the current to be measured I is determined from the output voltage V obtained at the output terminal 8. Now, in the circuit shown in FIG. 1, if the transfer characteristic is determined assuming that the gain of the operational amplifier 6 is sufficiently large, the following equation (1) is obtained. V=-R 1 /N・I・1/(1-1/ω 2 LC-jr/ωL)
...(1) Here, N: Turning ratio of primary and secondary windings 3 and 4 R 1 : Resistance value of resistor 7 ω: Angular velocity L: Inductance of secondary winding 4 C: Capacitance r of capacitor 5 : Internal resistance value of secondary winding 4 As can be seen from equation (1), the characteristics in the low frequency range are:
【式】およびω1＝ｒ／Ｌによつて決ま
り、ω0はω1に比べて小さく、少なとも1/2に選択
しないと低周波域にピークを生ずる。ここで、
ω0＝１／２ω1としたとき
Ｃ＝4L／r2 …(2)
であり、例えば、外径68φ、内径44φ、厚さ13mm
でインダクタンス係数が4300mHのコアに、
0.32φの線材を1000ターン巻いて二次巻線４とす
ると、そのインダクタンスは約4H（ヘンリー）、
その内部抵抗ｒは約10Ωとなり、コンデンサ５の
必要なキヤパシタンスは第(2)式から0.16Fとなる。
このように従来の電流電圧変換器は、低周波域
まで測定範囲が必要な場合には、コンデンサ５の
キヤパシタンスＣは非常に大きな値のものが必要
となる欠点があつた。
この発明は上記の欠点を除去するためになされ
たものである。以下、この発明について説明す
る。
第２図はこの発明の一実施例を示すもので、第
１図の従来例と同様にカレント・トランスに接続
した場合である。この発明では、R1なる抵抗値
をもつ帰還抵抗器７を演算増幅器６の出力側とコ
ンデンサ５の入力側に接続し、高い抵抗値R2を
有する抵抗器９を演算増幅器６の出力側と反転入
力側に接続したもので、その他は第１図と同じで
ある。
第２図の回路における伝達特性を演算増幅器６
の利得が充分大きいとして求めると、下記第(3)式
のようになる。
Ｖ＝−Ｉ／Ｎ・R1R2／R1＋R2・１／｛１−R1＋ｒ／ω
2LC（R1＋R2）−ｊ（１／ωC（R1＋R2）＋ｒ／ωL）｝
…(3)
第(3)式において、
R2≫R1≫ｒ、
１／ωC（R1＋R2）≪ｒ／ωL
とすると、
Ｖ＝−Ｉ／Ｎ・R1R2／R1＋R2
・１／｛１−１／ω2LC・R1／R2−ｊｒ／ωL｝…(4
)
となる。
第(1)式と第(4)式を比べるとわかるように、第(4)
式でのＣ×R2／R1が、第(1)式のＣに相当する。
第(4)式において、フラツト域での変換特性は、
Ｖ＝−Ｉ／Ｎ・R1R2／R1＋R2
であるが、R2≫R1に選ぶので、
Ｖ＝−−Ｉ／Ｎ・R1となる。
すなわち、従来の回路にくらべ、この発明によ
ると、１／R2／R1のコンデンサ５のキヤパシタンス
値で、同一の低周波特性を得ることができること
になる。
例えば、R1＝10KΩ、R2＝10MΩと選べば、
Ｃの値は従来にくらべ、１／107／104＝１／103
で同一の特性が得られることになる。したがつ
て、前述の例においては、従来例ではＣ＝0.16F
を必要としたのが、Ｃ＝160μFでよいことにな
る。
なお、上記ではこの発明の電流電圧変換器をカ
レント・トランスに接続したが、この発明はこれ
に限定されるものでなく、他の被測定電流源であ
つてもよい。
以上詳細に説明したように、この発明は被測定
電流の電流値の応じた電圧をコンデンサを介して
演算増幅器の反転入力端子に加え、この演算増幅
器の出力側から抵抗器を介して入力側にフイード
バツクを加え、被測定電流を電圧値に変換して測
定する交流入力用電流電圧変換器において、電流
―電圧の変換率を決めるフイードバツク抵抗器を
演算増幅器の出力側とコンデンサの入力端子の間
に接続し、演算増幅器の出力側と反転入力側間を
高抵抗の抵抗器で接続することにより従来回路に
おいてはその周波数特性を実現するのに必要とす
るコンデンサの値が実用的な値とならない程大き
な場合でも、前記付加した抵抗器の抵抗値を選定
することにより等価的にそのコンデンサの値を実
現することができ、したがつて、直流安定度の良
い、低い低周波数領域まで平坦な特性をもつ交流
入力用電流電圧変換器が得られる利点がある。It is determined by [Formula] and ω 1 =r/L, and ω 0 is smaller than ω 1 , and unless it is selected to be at least 1/2, a peak will occur in the low frequency range. Here, when ω 0 = 1/2ω 1, C = 4L/r 2 ...(2) For example, outer diameter 68φ, inner diameter 44φ, thickness 13mm
In the core with an inductance coefficient of 4300mH,
If a 0.32φ wire is wound 1000 turns to form secondary winding 4, its inductance is approximately 4H (Henry).
Its internal resistance r is about 10Ω, and the required capacitance of the capacitor 5 is 0.16F from equation (2). As described above, the conventional current-voltage converter has the disadvantage that when a measurement range extending to a low frequency range is required, the capacitance C of the capacitor 5 is required to have a very large value. This invention has been made to eliminate the above-mentioned drawbacks. This invention will be explained below. FIG. 2 shows an embodiment of the present invention, in which it is connected to a current transformer in the same way as the conventional example shown in FIG. In this invention, a feedback resistor 7 having a resistance value of R 1 is connected to the output side of the operational amplifier 6 and an input side of the capacitor 5, and a resistor 9 having a high resistance value R 2 is connected to the output side of the operational amplifier 6. It is connected to the inverting input side, and the rest is the same as in FIG. The transfer characteristics in the circuit shown in Figure 2 are expressed by the operational amplifier 6
Assuming that the gain is sufficiently large, the following equation (3) is obtained. V=-I/N・R 1 R 2 /R 1 +R 2・1/{1-R 1 +r/ω
2 LC (R 1 + R 2 ) − j (1/ωC (R 1 + R 2 ) + r/ωL)}
...(3) In equation (3), R 2 ≫R 1 ≫r, 1/ωC (R 1 +R 2 ) ≪r/ωL, then V=-I/N・R 1 R 2 /R 1 +R 2・1/{1−1/ω 2 LC・R 1 /R 2 −jr/ωL}…(4
) becomes. As can be seen by comparing equations (1) and (4),
C×R 2 /R 1 in the equation corresponds to C in equation (1). In equation (4), the conversion characteristic in the flat region is V=-I/N・R 1 R 2 /R 1 +R 2 , but since R 2 ≫ R 1 is selected, V=--I/ It becomes N・R 1 . That is, compared to the conventional circuit, according to the present invention, the same low frequency characteristics can be obtained with a capacitance value of the capacitor 5 of 1/R 2 /R 1 . For example, if you choose R 1 = 10KΩ and R 2 = 10MΩ,
Compared to the conventional case, the value of C is 1/10 7 /10 4 =1/10 3 and the same characteristics can be obtained. Therefore, in the above example, C=0.16F in the conventional example.
Instead of requiring , C = 160μF will suffice. Although the current-voltage converter of the present invention is connected to a current transformer in the above example, the present invention is not limited to this, and other current sources to be measured may be used. As explained in detail above, the present invention applies a voltage corresponding to the current value of the current to be measured to the inverting input terminal of an operational amplifier via a capacitor, and from the output side of the operational amplifier to the input side via a resistor. In a current-voltage converter for AC input that adds feedback and converts the current to be measured into a voltage value, a feedback resistor that determines the current-voltage conversion rate is installed between the output side of the operational amplifier and the input terminal of the capacitor. By connecting a high-resistance resistor between the output side and the inverting input side of the operational amplifier, the value of the capacitor required to achieve the frequency characteristics in the conventional circuit is no longer practical. Even if the value of the capacitor is large, it is possible to equivalently achieve the value of the capacitor by selecting the resistance value of the added resistor. Therefore, it is possible to achieve a flat characteristic down to a low frequency range with good DC stability. This has the advantage of providing a current-voltage converter for AC input.
第１図は従来の電流電圧変換器の一例を示す回
路図、第２図はこの発明の一実施例を示す回路図
である。
図中、１はカレント・トランス、２は鉄心、３
は一次巻線、４は二次巻線、５はコンデンサ、６
は演算増幅器、７は抵抗器、８は出力端子、９は
抵抗器である。
FIG. 1 is a circuit diagram showing an example of a conventional current-voltage converter, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. In the figure, 1 is the current transformer, 2 is the iron core, 3
is the primary winding, 4 is the secondary winding, 5 is the capacitor, 6
is an operational amplifier, 7 is a resistor, 8 is an output terminal, and 9 is a resistor.
Claims (1)
の電極に印加されるコンデンサと、このコンデン
サの他方の電極に反転入力側が接続された演算増
幅器と、この演算増幅器の出力側と前記反転入力
側との間に接続された抵抗器と、前記演算増幅器
の出力側と前記コンデンサの一方の電極との間に
接続された抵抗器からなり、前記反転入力側に接
続された抵抗器の抵抗値が前記コンデンサの一方
の入力側に接続された抵抗器の抵抗値に比して充
分大きな値に選定されたことを特徴とする交流入
力用電流電圧変換器。1 A capacitor to which a voltage corresponding to the current value of the current to be measured is applied to one electrode, an operational amplifier whose inverting input side is connected to the other electrode of this capacitor, and an output side of this operational amplifier and the inverting input side connected to the other electrode of the capacitor. and a resistor connected between the output side of the operational amplifier and one electrode of the capacitor, and the resistance of the resistor connected to the inverting input side. 1. A current-voltage converter for AC input, characterized in that the value is selected to be sufficiently larger than the resistance value of a resistor connected to one input side of the capacitor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13445280A JPS5760265A (en) | 1980-09-29 | 1980-09-29 | Current voltage converter for ac input |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13445280A JPS5760265A (en) | 1980-09-29 | 1980-09-29 | Current voltage converter for ac input |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5760265A JPS5760265A (en) | 1982-04-12 |
| JPH0155422B2 true JPH0155422B2 (en) | 1989-11-24 |
Family
ID=15128667
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13445280A Granted JPS5760265A (en) | 1980-09-29 | 1980-09-29 | Current voltage converter for ac input |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5760265A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101846702A (en) * | 2010-05-10 | 2010-09-29 | 伊博电源（杭州）有限公司 | Inductive current detection circuit |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2388914B (en) * | 2002-05-10 | 2005-09-28 | Pri Ltd | Clamp-on ct |
| CN109541513B (en) * | 2018-12-25 | 2022-02-08 | 北京东方计量测试研究所 | Alternating current micro-current tracing device and method |
-
1980
- 1980-09-29 JP JP13445280A patent/JPS5760265A/en active Granted
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101846702A (en) * | 2010-05-10 | 2010-09-29 | 伊博电源（杭州）有限公司 | Inductive current detection circuit |
| CN101846702B (en) | 2010-05-10 | 2012-05-30 | 伊博电源（杭州）有限公司 | Inductive current detection circuit |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5760265A (en) | 1982-04-12 |
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