JP4029653B2 - 3-phase AC ammeter, 3-phase AC current measurement method - Google Patents

Description

すなわち、次の３つの計算式が得られる。
【数２】

演算回路が上記計算式に基づいて計算を行うことにより、ｉｕ，ｉｖ，ｉｗの値がそれぞれ求められることになる。
【００２４】
本実施例の３相交流用電流計２によれば、以下のような作用効果を奏することができる。
本実施例では、３相交流が発生する回転合成磁場Ｂを、回転対象位置で直交配置された２つのＭＩセンサ１０，１２によって検知するとともに、その検知結果に基づいて３相交流の電流値ｉｕ，ｉｖ，ｉｗを求めるようにしている。そのために、各相のバスバー２２，２４，２６を特定点Ｏの周囲に１２０°の位置関係をもって回転対称に配置し、さらに特定点Ｏ上に２つのＭＩセンサ１０，１２を配置している。
【００２５】
超高感度なＭＩセンサ１０，１２を用いているため、回転合成磁場Ｂの大きさが非常に小さいものであったとしても、その変化を確実に検出することができ、感度に優れた３相交流用電流計２を提供することができる。さらに本実施例の電流計２では、大型化や故障発生の原因となる電圧検出用コイルを必須構成要素としていないため、全体の小型化が容易でありかつ信頼性に優れたものとなる。また、電圧検出用コイルやシャント抵抗が要らないことから、電圧計を比較的簡単に製造することができる。
【００２６】
ＭＩセンサを３つ用いてバスバー２２，２４，２６を流れる電流値ｉｕ，ｉｖ，ｉｗを個別に測定するという方法も考えられるが、本実施例によればＭＩセンサを１つ省略でき、その分だけ低コスト化と小型化を図ることができる。
【００２７】
この３相交流電流計２では、導通路である各相のバスバー２２，２４，２６は仮想面Ｓを１回のみ通過するように配置されている。従って、バスバー２２，２４，２６が直線的で単純な形状でよくなり、金属材料の折り曲げ加工などが基本的に少なくて済むようになる。簡単かつ安価に製造可能な電流計２とすることができ、また小型化も容易な電流計２となる。また、このようなバスバー２２，２４，２６を用いれば、巻いた部分のない単純形状の導通路となるので、基本的にインピーダンスの影響が出るようなことがなくなる。極めて応答性に優れたものとなり、これにより測定精度をいっそう高くすることができる。
【００２８】
本実施例の３相交流電流計２に使用されるＭＩセンサ１０，１２は、コネクタ１８内に収容されている。ＭＩセンサ１０，１２は小型であっても超高感度という特長があるため、コネクタ１８内に無理なく収容することができる。そして、このようなセンサ内蔵構造としたときには、センサ外付け構造としたときに比べて、全体的にすっきりとした外観となる。
【００２９】
本実施例における各相のバスバー２２，２４，２６は、仮想面Ｓ内にてＭＩセンサ１０，１２を中心として完全回転対称になるように配置されている。そのために具体的には、２つのバスバー２４，２６には捩れ部３０が形成されている。捩れ部３０は、特定点Ｏを中心とする仮想円Ｃの半径Ｒ上にバスバー２４，２６が重なり合うような状態で形成されている。従って、このような配置を採用したことにより、大きさの安定した、センシングに理想的な回転合成磁場Ｂを発生させることができ、測定精度をいっそう高くすることができる。しかも、仮想面通過位置以外の位置については、必要に応じて別のバスバー配置態様を採ることができる。本実施例では、図示しない相手側コネクタ形状に合わせて、バスバー２２，２４，２６の幅方向（短手方向）が同じ方向を向くような配置態様としている。それゆえ、例えば既存のコネクタ１８内に、バスバー２２，２４，２６及びＭＩセンサ１０，１２をともに収容するような構成を実現する際に好都合なものとなる。
【００３０】
（第２実施例）
次に、第２実施例の３相交流電流計４２について説明する。図５は、この３相交流用電流計４２に用いられるバスバー２２，２４，２６の要部概略斜視図を示している。図６は、３相交流用電流計４２の要部概略斜視図を示している。なお同図では各バスバー２２，２４，２６を幅のない単なる曲線で概略的に描いている。図７（ａ）は、仮想面Ｓにおける概略断面図、（ｂ）は２つのＭＩセンサ１０，１２によって検知される回転合成磁界Ｂを表した概略図を示している。
図５に示されるように、本実施例のバスバー２２，２４，２６は、第１実施例のときとは形状が異なっており、具体的には略Ｕ字状に形成された折返し部４４をその一箇所に備えている。略Ｕ字状に形成されたバスバーの巻回数は１ターン弱である。各バスバー２２，２４，２６は、折返し部４４の両端において仮想面Ｓを２回通過するように配置されている。本実施例においても、各バスバー２２，２４，２６は、図７（ａ）に示すように、仮想面Ｓ内にてＭＩセンサ１０，１２のある特定点Ｏを中心として完全回転対称となっている。
【００３１】
このように構成された３相交流用電流計４２は、第１実施例のときと同様の基本構成を備えているので、小型化が容易であって比較的簡単に製造でき、しかも感度・信頼性が高いものとなる。
【００３２】
また本実施例では各バスバー２２，２４，２６が仮想面Ｓを２回通過する構成を採用しているため、仮想面Ｓを１回のみ通過する第１実施例の構成に比べて、大きな回転合成磁場Ｂが発生する。よって、同じ性能のＭＩセンサ１０，１２を用いた場合であっても、より大きなセンサ出力を得ることができ、さらなる高感度化を達成することができる。なお、この構成であれば、巻回数がせいぜいワンターン以下であるため簡単に製造できコスト増もそれほど伴わない。
【００３３】
以上、本発明の具体例を詳細に説明したが、これらは例示に過ぎず、特許請求の範囲を限定するものではない。特許請求の範囲に記載の技術には、以上に例示した具体例を様々に変形、変更したものが含まれる。
・例えば、図８に示す別の実施例の３相交流用電流計５２のようなバスバー配置態様にしてもよい。ここでは、各バスバー２２，２４，２６の厚さ方向が、特定点Ｏを中心とする仮想円Ｃの半径Ｒ方向に対して平行になっている。
・第１、第２実施例では、導通路として断面長方形状のバスバー２２，２４，２６を用いていたが、これに限定されることはない。例えば、図９に示す別の実施例の３相交流用電流計６２のように、断面略円形状の電線６４などを用いることも勿論可能である。
・第１、第２実施例ではＭＩセンサ１０，１２をコネクタ１８に内蔵した構成を採用したが、これに限定されることはなく、ＭＩセンサ１０，１２がコネクタ１８以外のもの（例えばケーブル等）に内蔵されている構成とすることもできる。あるいは、ＭＩセンサ１０，１２がコネクタ１８やケーブルに内蔵されていない構成を採用することも可能である。
・第１実施例ではバスバー２４，２６には捩れ部３０が形成されていたが、これを省略した構成としてもよい。
【００３４】
本明細書又は図面に説明した技術要素は、単独であるいは各種の組合せによって技術的有用性を発揮するものであり、出願時請求項記載の組合せに限定されるものではない。また、本明細書又は図面に例示した技術は複数目的を同時に達成し得るものであり、そのうちの一つの目的を達成すること自体で技術的有用性を持つものである。
【図面の簡単な説明】
【図１】本発明を具体化した第１実施例の３相交流用電流計の概略図を示す。
【図２】第１実施例において、モータドライバ回路から３相交流モータに出力されるＵ，Ｖ，Ｗ相の波形を表したグラフを示す。
【図３】第１実施例の３相交流用電流計の要部概略斜視図を示す。
【図４】（ａ）は第１実施例の３相交流用電流計の仮想面における概略断面図、（ｂ）は３相交流用電流計を構成する２つのＭＩセンサの配置関係を表した概略斜視図、（ｃ）は２つのＭＩセンサによって検知される回転合成磁界を表した概略図を示す。
【図５】第２実施例の３相交流用電流計に用いられるバスバーの要部概略斜視図を示す。
【図６】第２実施例の３相交流用電流計の要部概略斜視図を示す。
【図７】（ａ）は第２実施例の３相交流用電流計の仮想面における概略断面図、（ｂ）は２つのＭＩセンサによって検知される回転合成磁界を表した概略図を示す。
【図８】別の実施例の電流計の要部概略断面図を示す。
【図９】別の実施例の電流計の要部概略断面図を示す。
【符号の説明】
２，４２，５２，６２：３相交流用電流計
４：３相交流を出力する手段であるモータドライバ回路
６：負荷として３相交流モータ
１０，１２：ＭＩセンサ
１８：コネクタ
２２：導通路としてのＵ相バスバー
２４：導通路としてのＶ相バスバー
２６：導通路としてのＷ相バスバー
３０：捩れ部
４４：折返し部
６４：導通路としての電線
Ｓ：仮想面
Ｏ：特定点
Ｃ：仮想円
Ｒ：半径
ｉｕ，ｉｖ，ｉｗ：３相交流の電流値
Ｂ：回転合成磁場[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ammeter for measuring a three-phase alternating current value and a method for measuring a three-phase alternating current value.
[0002]
[Prior art]
When a three-phase AC motor is driven using a DC power supply, a motor driver circuit that converts a DC current into a three-phase AC composed of a U phase, a V phase, and a W phase that are different in phase by 120 ° is often installed. This type of motor driver circuit is configured to operate based on a command from an external controller. In order to detect whether the output of the motor driver circuit is a desired alternating current, a three-phase alternating current ammeter is often provided between the motor driver circuit and the motor, and the measurement result is often fed back to the controller.
In order to measure the current value of each phase of the three-phase alternating current, the following techniques are known.
In the first prior art, coils are provided around each of the conduction paths corresponding to the U phase, V phase, and W phase, the voltages generated at both ends of these coils are measured, and the current value of each phase is obtained therefrom. That's it.
In the second prior art, a shunt resistor is inserted in each of the conduction paths corresponding to the U phase, the V phase, and the W phase, a potential difference generated in these three shunt resistors is measured, and a current value of each phase is obtained therefrom. That's it.
[0003]
[Problems to be solved by the invention]
In the case of the first prior art in which the coil is wound around each conduction path, there is a problem that the whole measuring means is easily increased in size and that the manufacturing is troublesome. In addition, in order to increase the sensitivity, it is necessary to increase the number of turns of the coil, and as a result, the above problem becomes more remarkable. Further, since the coil may be disconnected or short-circuited, there is a problem that high reliability cannot be expected with the measuring means using the coil.
Further, in the second prior art, since it is necessary to insert a shunt resistor in series with each of the conduction paths, there is also a problem that the manufacturing is troublesome. On top of that, there is a limit to the increase in sensitivity.
[0004]
Accordingly, an object of the present invention is to provide a three-phase AC ammeter that is easy to downsize, can be manufactured relatively easily, and is highly sensitive and highly reliable.
[0005]
[Means for solving the problem, operation and effect]
Assuming a virtual plane through which three conduction paths of three-phase alternating current pass, the three conduction paths are arranged approximately rotationally symmetrically with a 120 ° positional relationship around a specific point in the virtual plane. And The three-phase alternating current flowing through each conduction path changes periodically as shown in the graph of FIG. The magnetic field generated at the rotationally symmetric central position is a vector synthesis of the magnetic fields generated by the currents flowing through the respective conduction paths, but the currents flowing through the respective conduction paths are cyclic with a phase difference of 120 ° as shown in the graph of FIG. Therefore, the magnetic field generated at the rotationally symmetrical center position is a constant magnetic field, and becomes a rotating magnetic field that rotates at a constant angular velocity. The rotation period of this magnetic field coincides with the current change period of the three-phase alternating current. If the magnitude and direction of the synthesized magnetic field are known, the magnitude and phase of the current in each phase can be uniquely determined.
The inventor of the present application pays attention to the rotation phenomenon of the synthetic magnetic field at the specific point described above, and also conceived that the direction and magnitude of the synthetic magnetic field is detected by some means and uses it, and further develops this. Finally, the following invention of the present application has been completed.
[0006]
That is, the ammeter for three-phase alternating current of the present invention includes three conductive paths that are parallel to each other and in which the distance between them is equal , and three conductive lines in a virtual plane that is perpendicular to the three conductive paths. Two MI sensors arranged in two orthogonal directions at a specific point at an equal distance from each of the passages, and two outputs from the two MI sensors are converted into a three-phase AC current value by a predetermined calculation formula (Claim 1).
This three-phase alternating current ammeter allows three-phase alternating current to flow through three conductive paths that are parallel to each other and have the same distance from each other, and from each of the three conductive paths in a virtual plane perpendicular to the three conductive paths. A rotating magnetic field in which a three-phase alternating current is generated at a specific point at an equal distance is detected by two orthogonally arranged MI sensors, and two outputs from the two MI sensors are detected by a predetermined calculation formula. It converts into an electric current value (Claim 6).
According to the above apparatus and method, by using two MI sensors arranged orthogonally on a specific point, magnetic fields in two orthogonal directions in a virtual plane can be measured. The direction and magnitude of the magnetic field can be detected. The phase of the current change in each phase can be uniquely determined from the direction of the synthesized magnetic field, and the current amplitude of each phase can be uniquely determined from the magnitude of the synthesized magnetic field.
According to the above apparatus and method, by using two MI sensors arranged orthogonally on a specific point, magnetic fields in two orthogonal directions in the virtual plane can be measured. The direction and size of can be detected. The phase of the current change in each phase can be uniquely determined from the direction of the synthesized magnetic field, and the current amplitude of each phase can be uniquely determined from the magnitude of the synthesized magnetic field.
[0007]
Since the ammeter of the present invention uses an ultrasensitive MI sensor, even if the magnitude of the synthesized magnetic field is very small, the magnitude and direction can be reliably detected, and the sensitivity is excellent. An ammeter can be provided. Furthermore, in the ammeter of the present invention, the voltage detection coil that causes an increase in size and the occurrence of a failure is not an essential component, so that the entire size can be easily reduced and the reliability can be improved. In addition, since no voltage detection coil or shunt resistor is required, an ammeter can be manufactured relatively easily.
[0008]
The “MI sensor” in the present specification refers to an ultrasensitive magnetic sensor using a so-called magnetic impedance effect (MI effect). The MI effect is as follows. That is, when a high-frequency current or a pulse current is passed through an elongated high magnetic permeability metal, a skin effect is produced in the metal. The square of the current path depth δ at this time is proportional to the electrical resistivity ρ, but is inversely proportional to the angular frequency ω of the high-frequency current and the permeability μ in the direction of the magnetic field generated by the current. Therefore, the depth δ of the current path changes due to a change in the magnetic permeability μ caused by the external magnetic field Hex. For this reason, the electric resistance and the inductance change at the same level, and the magnitude of the impedance Z changes with the external magnetic field Hex. The rate of change in the magnitude of the impedance Z can easily be set to 100% per Oersted for an amorphous wire, for example, and such an electromagnetic phenomenon is referred to as the MI effect.
[0009]
In the field of applied magnetism, an electromagnetic phenomenon called GMR (giant magnetoresistance) effect is known. Recently, a magnetic sensor using this effect has been proposed in part, but a magnetic sensor using the MI effect is proposed. It is possible to achieve higher sensitivity. Note that the magnetic sensor using the MI effect has very low power consumption and also has a very fast response because a high-frequency current becomes a carrier for magnetic modulation.
[0010]
In the three-phase alternating current ammeter of the present invention, the current can be measured even if each conduction path passes through the virtual plane once (claim 2).
In this case, since the conductive material forming the conduction path may be a straight and simple shape, it can be manufactured more easily and inexpensively, and the size can be easily reduced. In addition, if the conduction path has a simple shape without a wound portion, it is difficult to influence the impedance. Therefore, the response is extremely excellent, and the measurement accuracy can be further increased.
[0011]
Each conduction path may have a folded portion formed so that the number of turns is equal to or less than one turn, and may be arranged so as to pass through the virtual surface twice at both ends of the folded portion.
In this case, since the conduction path is configured to pass through the virtual plane twice, a large combined magnetic field is generated as compared with the configuration where the conduction path passes only once through the virtual plane. Therefore, even when MI sensors having the same performance are used, a larger sensor output can be obtained, and further higher sensitivity can be achieved. In addition, since the number of windings is at most one turn or less, it can be manufactured easily and is not accompanied by much cost increase.
[0012]
The MI sensor is preferably housed in a connector that connects a means for outputting a three-phase alternating current and a load that operates by the three-phase alternating current (claim 4).
Even if the MI sensor is small, it has the feature of ultra-high sensitivity, so it can be accommodated in the connector without difficulty.
[0013]
It is preferable that each conduction path is constituted by a bus bar, and these bus bars are arranged so as to be rotationally symmetric with respect to the MI sensor.
By arranging in this manner, a synthetic magnetic field ideal for sensing with a stable size can be generated, and the measurement accuracy can be further increased.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The main features of the embodiments of the present invention to be described later will be described.
(Embodiment 1) It is provided with three bus bars which are conduction paths, two of which have a twisted portion at a position passing through a virtual plane, and the twisted portion is on the radius of a virtual circle centered on a specific point. The three-phase AC ammeter according to claim 5, wherein the bus bars are formed so as to overlap each other.
According to the configuration of aspect 1, by forming the twisted portion at a position passing through the virtual plane, it is possible to reliably generate a synthetic magnetic field that is ideal for sensing by the MI sensor. In addition, as for the positions other than the virtual plane passing position, another bus bar arrangement mode can be adopted as necessary. Therefore, for example, it is advantageous in realizing a configuration in which both the bus bar and the MI sensor are accommodated in an existing connector.
[0015]
【Example】
First Embodiment Hereinafter, a three-phase AC ammeter 2 according to a first embodiment embodying the present invention will be described in detail.
FIG. 1 shows a schematic diagram of a three-phase AC ammeter 2 of the first embodiment. FIG. 2 is a graph showing U, V, and W phase current waveforms output from the motor driver circuit 4 to the three-phase AC motor 6. FIG. 3 is a schematic perspective view of a main part of the three-phase AC ammeter 2. FIG. 4A shows a schematic cross-sectional view of the three-phase AC ammeter 2 on the virtual plane S, and FIG. 4B shows the positional relationship between the two MI sensors 10 and 12 constituting the three-phase AC ammeter 2. It is the schematic perspective view represented, (c) has shown the schematic showing the rotation synthetic | combination magnetic field B detected by the two MI sensors 10 and 12. FIG.
[0016]
As shown in FIG. 1, the motor driver circuit 4 is electrically connected to a DC power supply 14 and a controller 16. The controller 16 is configured to output a predetermined command signal to the motor driver circuit 4. The motor driver circuit 4 operates in accordance with the command signal, and is configured to convert a direct current obtained from the direct current power source 14 into a three-phase alternating current shown in the graph of FIG. The motor driver circuit 4 and the three-phase AC motor 6 are electrically connected to each other via a cable and a connector 18. The three-phase alternating current generated by the motor driver circuit 4 is supplied to the U, V, and W-phase windings in the motor 6 via the cable and the conductive path accommodated in the connector 18, whereby the motor 6 rotates. It comes to drive.
[0017]
The three-phase AC ammeter 2 of this embodiment is housed in the connector 18 and is electrically connected to the controller 16. The controller 16 is configured to receive the sensor output from the three-phase AC ammeter 2 and feedback-control the motor driver circuit 4 based on the sensor output.
[0018]
As schematically shown in FIG. 3, the three-phase AC ammeter 2 of this embodiment includes a U-phase bus bar 22, a V-phase bus bar 24, and a W-phase bus bar 26 that are three-phase AC conduction paths. . These bus bars 22, 24, and 26 are embedded in the insulating material 28 constituting the connector 18, for example, by insert molding or the like. The three linear bus bars 22, 24, and 26 have an equal cross-sectional shape and an equal cross-sectional area, and all of them extend in parallel along the same direction.
Here, a virtual plane S that is perpendicular to the three bus bars 22, 24, 26 and through which the bus bars 22, 24, 26 pass is assumed, and one point in the virtual plane S is defined as a specific point O. Define as 4A shows a schematic cross-sectional view of the virtual plane S, FIG. 4B shows a schematic perspective view showing the positional relationship between the two MI sensors 10 and 12, and FIG. 4C shows two MI. The schematic diagram showing the rotation synthetic magnetic field B detected by the sensors 10 and 12 is shown.
[0019]
As shown in FIG. 4 (a), the three bus bars 22, 24, and 26 pass through the virtual plane S only once, and are arranged on the rotation target with a 120 ° positional relationship around the specific point O. ing. The V-phase bus bar 24 and the W-phase bus bar 26 have a twisted portion 30 at the passing position of the virtual plane S. The twisted portion 30 is formed in such a manner that the bus bars 24 and 26 overlap on the radius R of the virtual circle C centered on the specific point O. Therefore, on the virtual plane S, the bus bars 22, 24, and 26 having the same cross-sectional shape and the same cross-sectional area are located at the same distance from the specific point O, and the distance between them is the same. 24, 26 are arranged so as to be completely rotationally symmetric.
[0020]
In FIG. 4C, as an example, a current flows through the U-phase bus bar 22 and the V-phase bus bar 24 from the front side to the back side, and a current flows through the W-phase bus bar 26 from the back side to the front side. It is shown. In this case, each bus bar 22, 24, 26 generates a magnetic field B22, B24, B26. B in the figure indicates a combined magnetic field obtained by vector addition of the magnetic fields B22, B24, and B26. The magnitude of the synthetic magnetic field B depends on the magnitude of the current amplitude flowing through each bus bar 22, 24, 26, and the direction of the synthetic magnetic field B rotates in synchronization with the period of the current flowing through each bus bar 22, 24, 26. To do.
[0021]
As shown in FIG. 4B, the three-phase AC ammeter 2 includes two MI sensors 10 and 12 that are orthogonally arranged at the position of the specific point O. These MI sensors 10 and 12 are fixed to each other so that the relative angle does not fluctuate when they are overlapped in a cross shape, and the position of the specific point O in the virtual plane S as shown in FIG. Is arranged. These MI sensors 10 and 12 play a role of measuring magnetic fields in two orthogonal directions (X direction and Y direction) in the virtual plane S, in other words, detecting the direction and magnitude of the rotationally synthesized magnetic field B. One MI sensor 10 outputs a signal proportional to the magnitude of the X-direction component of the rotational synthetic magnetic field B, and the other MI sensor 12 outputs a signal proportional to the magnitude of the Y-direction component of the rotational synthetic magnetic field B. .
[0022]
As described above, the “MI sensor” refers to an ultrasensitive magnetic sensor using the MI effect. The MI sensors 10 and 12 to be used are not particularly limited, but in this embodiment, an MI element in which pickup means is provided around an amorphous wire (composition: 4% Fe68% Co13% Si15% B) is used. In addition, canceling means for creating a magnetic field state that apparently cancels the external magnetic field may be provided. The amorphous wire is electrically connected to a pulse signal generation circuit provided separately from the MI element. The pulse signal generation circuit includes a DC power supply circuit and a chopper circuit. The pulse signal generation circuit outputs a predetermined pulse current to the amorphous wire. The pickup means is electrically connected to a signal processing circuit provided separately from the MI element. The current picked up by the pick-up means is processed by a signal processing circuit and then output as a sensor output signal. The MI sensors 10 and 12 of this type are driven by pulse signals, so that the power consumption is extremely small and is about several tens of mW at most.
[0023]
Two sensor output signals obtained through the signal processing circuit are input to an arithmetic circuit (not shown). The arithmetic circuit may be provided at a different position in the connector 18, but may be provided separately from the connector 18. In the arithmetic circuit, a predetermined calculation is performed based on these two sensor output signals, and the current value data of the three-phase alternating current obtained as a result is finally input to the controller 16.
When the output of the MI sensor 10 is A, the output of the MI sensor 12 is B, and the current values of the U-phase, V-phase, and W-phase are iu, iv, and iw, respectively, these parameters have the following relationship: Holds.
[Expression 1]

That is, the following three formulas are obtained.
[Expression 2]

When the arithmetic circuit performs calculations based on the above calculation formulas, the values of iu, iv, and iw are obtained.
[0024]
According to the three-phase AC ammeter 2 of the present embodiment, the following operational effects can be achieved.
In the present embodiment, the rotationally synthesized magnetic field B in which the three-phase alternating current is generated is detected by the two MI sensors 10 and 12 arranged orthogonally at the rotation target position, and the current value iu of the three-phase alternating current is based on the detection result. , Iv, iw are obtained. For this purpose, the bus bars 22, 24, 26 of each phase are arranged in a rotationally symmetrical manner with a 120 ° positional relationship around the specific point O, and two MI sensors 10, 12 are arranged on the specific point O.
[0025]
Since the ultra-sensitive MI sensors 10 and 12 are used, even if the magnitude of the rotational synthetic magnetic field B is very small, the change can be detected reliably, and the three-phase excellent in sensitivity. An AC ammeter 2 can be provided. Furthermore, since the ammeter 2 of the present embodiment does not include a voltage detection coil that causes an increase in size or occurrence of a failure as an essential component, the overall size can be easily reduced and the reliability can be improved. Further, since no voltage detection coil or shunt resistor is required, the voltmeter can be manufactured relatively easily.
[0026]
A method of individually measuring the current values iu, iv, and iw flowing through the bus bars 22, 24, and 26 using three MI sensors is also conceivable. However, according to this embodiment, one MI sensor can be omitted. Only cost reduction and size reduction can be achieved.
[0027]
In this three-phase alternating current ammeter 2, the bus bars 22, 24, and 26 of each phase, which are conduction paths, are arranged so as to pass through the virtual plane S only once. Accordingly, the bus bars 22, 24, and 26 may be linear and simple in shape, and the bending of the metal material or the like can be basically reduced. The ammeter 2 can be manufactured easily and inexpensively, and the ammeter 2 can be easily reduced in size. In addition, when such bus bars 22, 24, and 26 are used, a simple-shaped conduction path without a wound portion is provided, so that there is basically no influence of impedance. It becomes extremely excellent in responsiveness, which can further increase the measurement accuracy.
[0028]
The MI sensors 10 and 12 used in the three-phase AC ammeter 2 of this embodiment are accommodated in the connector 18. Even if the MI sensors 10 and 12 are small, they have a feature of ultra-high sensitivity, so that they can be accommodated in the connector 18 without difficulty. When such a sensor built-in structure is used, the overall appearance is cleaner than when a sensor external structure is used.
[0029]
The bus bars 22, 24, and 26 of each phase in the present embodiment are disposed in the virtual plane S so as to be completely rotationally symmetric about the MI sensors 10 and 12. Therefore, specifically, a twisted portion 30 is formed on the two bus bars 24 and 26. The twisted portion 30 is formed in such a manner that the bus bars 24 and 26 overlap on the radius R of the virtual circle C centered on the specific point O. Therefore, by adopting such an arrangement, it is possible to generate a rotationally synthesized magnetic field B that is stable in size and ideal for sensing, and the measurement accuracy can be further increased. In addition, as for the positions other than the virtual plane passing position, another bus bar arrangement mode can be adopted as necessary. In the present embodiment, the arrangement is such that the width direction (short direction) of the bus bars 22, 24, 26 faces the same direction in accordance with the mating connector shape (not shown). Therefore, for example, it is convenient when realizing a configuration in which the bus bars 22, 24, 26 and the MI sensors 10, 12 are accommodated together in the existing connector 18.
[0030]
(Second embodiment)
Next, the three-phase AC ammeter 42 of the second embodiment will be described. FIG. 5 shows a schematic perspective view of main parts of the bus bars 22, 24, and 26 used in the three-phase AC ammeter 42. FIG. 6 shows a schematic perspective view of a main part of the three-phase AC ammeter 42. In the figure, each bus bar 22, 24, 26 is schematically drawn by a simple curve having no width. FIG. 7A is a schematic cross-sectional view of the virtual plane S, and FIG. 7B is a schematic diagram showing the rotation synthesized magnetic field B detected by the two MI sensors 10 and 12.
As shown in FIG. 5, the bus bars 22, 24, and 26 of the present embodiment are different in shape from those of the first embodiment. Specifically, the folded portions 44 formed in a substantially U shape are provided. It is prepared in one place. The number of turns of the bus bar formed in a substantially U shape is less than one turn. Each bus bar 22, 24, 26 is arranged so as to pass through the virtual plane S twice at both ends of the folded portion 44. Also in this embodiment, the bus bars 22, 24, and 26 are completely rotationally symmetric about a specific point O of the MI sensors 10 and 12 in the virtual plane S, as shown in FIG. Yes.
[0031]
The three-phase AC ammeter 42 configured in this way has the same basic configuration as that of the first embodiment, so that it can be easily downsized and can be manufactured relatively easily, and also has sensitivity and reliability. It will be highly prone.
[0032]
Further, in this embodiment, each bus bar 22, 24, 26 employs a configuration that passes through the virtual surface S twice, so that the rotation speed is larger than that of the first embodiment that passes through the virtual surface S only once. A synthetic magnetic field B is generated. Therefore, even when the MI sensors 10 and 12 having the same performance are used, a larger sensor output can be obtained, and higher sensitivity can be achieved. In this configuration, since the number of windings is one turn or less, it can be easily manufactured and the cost is not so much increased.
[0033]
Specific examples of the present invention have been described above in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
-For example, you may make it a bus-bar arrangement | positioning aspect like the ammeter 52 for three-phase alternating current of another Example shown in FIG. Here, the thickness direction of each bus bar 22, 24, 26 is parallel to the radius R direction of the virtual circle C centered on the specific point O.
In the first and second embodiments, the bus bars 22, 24, and 26 having a rectangular cross section are used as the conduction paths, but the present invention is not limited to this. For example, it is of course possible to use an electric wire 64 having a substantially circular cross section as in a three-phase AC ammeter 62 of another embodiment shown in FIG.
In the first and second embodiments, the configuration in which the MI sensors 10 and 12 are incorporated in the connector 18 is adopted, but the present invention is not limited to this, and the MI sensors 10 and 12 are other than the connector 18 (for example, a cable or the like). ) Can also be configured. Alternatively, a configuration in which the MI sensors 10 and 12 are not incorporated in the connector 18 or the cable may be employed.
In the first embodiment, the torsion portion 30 is formed on the bus bars 24 and 26, but this may be omitted.
[0034]
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings can achieve a plurality of purposes at the same time, and has technical utility by achieving one of the purposes.
[Brief description of the drawings]
FIG. 1 shows a schematic diagram of a three-phase AC ammeter of a first embodiment embodying the present invention.
FIG. 2 is a graph showing U, V, and W phase waveforms output from the motor driver circuit to the three-phase AC motor in the first embodiment.
FIG. 3 is a schematic perspective view of a main part of the three-phase AC ammeter of the first embodiment.
4A is a schematic cross-sectional view in a virtual plane of the three-phase alternating current ammeter of the first embodiment, and FIG. 4B is an arrangement relationship of two MI sensors constituting the three-phase alternating current ammeter. FIG. 2C is a schematic perspective view, and FIG. 3C is a schematic diagram illustrating a rotationally synthesized magnetic field detected by two MI sensors.
FIG. 5 is a schematic perspective view of a main part of a bus bar used in a three-phase AC ammeter according to a second embodiment.
FIG. 6 is a schematic perspective view of a main part of a three-phase AC ammeter according to a second embodiment.
FIG. 7A is a schematic cross-sectional view in a virtual plane of the three-phase AC ammeter of the second embodiment, and FIG. 7B is a schematic diagram showing a rotational synthesized magnetic field detected by two MI sensors.
FIG. 8 is a schematic cross-sectional view of a main part of an ammeter according to another embodiment.
FIG. 9 is a schematic cross-sectional view of a main part of an ammeter according to another embodiment.
[Explanation of symbols]
2, 42, 52, 62: Three-phase AC ammeter 4: Motor driver circuit 6 for outputting three-phase AC 6: As a load Three-phase AC motor 10, 12: MI sensor 18: Connector 22: As a conduction path U-phase bus bar 24: V-phase bus bar 26 as a conduction path: W-phase bus bar 30 as a conduction path 30: Twist part 44: Folding part 64: Electric wire S as a conduction path S: Virtual plane O: Specific point C: Virtual circle R : Radius iu, iv, iw: current value of three-phase alternating current B: rotationally synthesized magnetic field

Claims (6)

Three conduction paths that are parallel to each other through which three-phase alternating current flows and are equal in distance to each other, and a specific point that is at an equal distance from each of the three conduction paths in a virtual plane perpendicular to the three conduction paths An ammeter for three-phase alternating current, comprising two MI sensors arranged in two orthogonal directions, wherein two outputs from the two MI sensors are converted into a three-phase alternating current value by a predetermined calculation formula .   The three-phase AC ammeter according to claim 1, wherein each conduction path is arranged so as to pass through the virtual plane only once.   Each conductive path has a folded portion formed so that the number of windings is one turn or less, and is arranged so as to pass through the virtual plane twice at both ends of the folded portion. The three-phase AC ammeter as described.   The three-phase according to any one of claims 1 to 3, wherein the MI sensor is housed in a connector for connecting a means for outputting a three-phase alternating current and a load operated by the three-phase alternating current. AC ammeter.   The three-phase according to any one of claims 1 to 4, wherein each conduction path is constituted by a bus bar, and these bus bars are arranged so as to be rotationally symmetric with respect to the MI sensor. AC ammeter. A three-phase alternating current is passed through three conductive paths that are parallel to each other and equal in distance to each other, and at a specific point that is at an equal distance from each of the three conductive paths in a virtual plane perpendicular to the three conductive paths. Rotating magnetic field generated by three-phase alternating current is detected by two MI sensors arranged orthogonally, and two outputs from two MI sensors are converted into current values of three-phase alternating current by a predetermined calculation formula A three-phase alternating current measurement method.

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