JP2017020848A

JP2017020848A - Power measurement method for three-phase ac current supplied to resistance load, and power measurement apparatus

Info

Publication number: JP2017020848A
Application number: JP2015137417A
Authority: JP
Inventors: 俊輔高松; Shunsuke Takamatsu
Original assignee: Japan Steel Works Ltd
Current assignee: Japan Steel Works Ltd
Priority date: 2015-07-09
Filing date: 2015-07-09
Publication date: 2017-01-26
Anticipated expiration: 2035-07-09
Also published as: JP6308981B2

Abstract

PROBLEM TO BE SOLVED: To provide a power measurement method capable of measuring electric power at low cost when a load consisting of only a resistance is powered with a three-phase AC current.SOLUTION: A line current of a line R and a line current of a line S are detected by current sensors 6 and 7. A voltage waveform of an inter-line voltage between the line R and a line T is obtained by multiplying the line current of the line R by a resistance value of a resistance between the line R and line T in an ON state when the resistance between the lines R and S is OFF and the line R and line S are in a non-conduction state. The voltage waveform is also considered to continue to have the same phase and amplitude when the resistance between the line R and line S is ON and the line R and line S are in a conductive state as well. A voltage waveform of the inter-line voltage between the line S and line T is obtained by multiplying a line current of the line S by a resistance value of a resistance between the line S and line T in an ON state when the line R and line S are in a non-conduction state. The voltage waveform is considered to continue to have the same phase and amplitude when the resistance between the line R and line S is ON and the line R and line S are in a conduction state as well. Electric power of the load is obtained by a two-power method from the line currents of the line R and line S, and inter-line voltages between the line R and line T and between the line S and line T.SELECTED DRAWING: Figure 1

Description

本発明は、三相交流電流によって抵抗のみからなる負荷に電力を供給するとき、負荷における電力を計算する電力測定方法に関するものであり、より詳しくは、三相３線式の三相交流電線において、複数の単相ヒータ等の抵抗負荷が設けられ、これらがＲ線、Ｓ線、Ｔ線のいずれか２線間に接続されて電力が供給されるとき、これらの抵抗負荷の合計電力を測定する電力測定方法に関するものである。 The present invention relates to a power measurement method for calculating power in a load when power is supplied to a load composed only of a resistor by a three-phase alternating current, and more specifically, in a three-phase three-wire three-phase alternating current electric wire. When a resistance load such as a plurality of single-phase heaters is provided, and these are connected between any two of the R, S, and T lines and power is supplied, the total power of these resistance loads is measured The present invention relates to a power measurement method.

抵抗のみからなる負荷に三相３線式の三相交流電線によって電力を供給することは広く実施されている。例えば抵抗のみからなる負荷として、射出成形機の加熱シリンダに設けられている複数のヒータをあげることができる。加熱シリンダには複数のヒータが巻かれているが、これらのヒータはいわゆる単相ヒータからなり、三相交流電線を構成しているＲ線、Ｓ線、Ｔ線のいずれか２線間に接続されている。そしてこれらの各ヒータにはソリッドステートリレーあるいは電磁接触器が設けられ、ＰＷＭ制御によってＯＮ／ＯＦＦされるようになっている。ＰＷＭ制御は、制御周期に対して電流を供給する通電時間の占める割合、すなわちデューティー比を調整する制御であり、ヒータへの電力供給を調整している。このようにして複数のヒータへ電力が供給されるとき、これらの合計の電力は、周知のように２組の線間における線間電圧と、２線における線電流を測定して、いわゆる２電力法によって計算することができる。この場合２個の電圧センサと、２個の電流センサとが必要になる。 It is widely practiced to supply power to a load consisting only of a resistance by a three-phase three-wire three-phase AC electric wire. For example, a plurality of heaters provided in a heating cylinder of an injection molding machine can be cited as a load consisting of only resistance. A plurality of heaters are wound around the heating cylinder. These heaters are so-called single-phase heaters, and are connected between any two of the R, S, and T wires constituting the three-phase AC wire. Has been. Each of these heaters is provided with a solid state relay or an electromagnetic contactor, and is turned on / off by PWM control. The PWM control is a control that adjusts the ratio of the energization time for supplying current to the control cycle, that is, the duty ratio, and adjusts the power supply to the heater. When electric power is supplied to a plurality of heaters in this way, the total electric power is obtained by measuring the line voltage between the two sets of lines and the line current in the two lines as is well known. Can be calculated by law. In this case, two voltage sensors and two current sensors are required.

特開２００１−３５９２９７号公報JP 2001-359297 A 特開２０００−２６６７８８号公報JP 2000-266788 A 特開２００５−１８９０１２号公報JP 2005-189012 A

抵抗のみからなる負荷に限定されないが、一般的な負荷に対して三相交流電流を供給するとき、その電力を測定する方法が、色々な特許文献において提案されている。特許文献１に記載の電力測定方法も、特許文献２に記載の電力測定方法も類似した方法であり、いずれにおいても線電流については２線において測定するが線間電圧は１組の線間しか測定しない。例えば、Ｓ線とＴ線のそれぞれにおいては線電流を測定するが、線間電圧はＴ線−Ｒ線間についてのみ測定する。そしてＴ線−Ｒ線間の線間電圧についてはこれを測定せず、Ｒ線−Ｓ線間の線間電圧が２／３πだけ位相がずれていると仮定して線間電圧を仮想的に定める。このように定めると、２組の線間における線間電圧と２線における線電流が得られるので、２電力法によって電力を計算することができる。 Although not limited to a load consisting of only a resistor, various patent literatures propose methods for measuring the power when a three-phase alternating current is supplied to a general load. The power measurement method described in Patent Document 1 and the power measurement method described in Patent Document 2 are similar methods. In either case, the line current is measured on two lines, but the line voltage is only between one set of lines. Do not measure. For example, the line current is measured for each of the S line and the T line, but the line voltage is measured only between the T line and the R line. The line voltage between the T line and the R line is not measured, and the line voltage is virtually calculated assuming that the line voltage between the R line and the S line is out of phase by 2 / 3π. Determine. If determined in this way, the line voltage between the two sets of lines and the line current in the two lines are obtained, so that the power can be calculated by the two-power method.

特許文献３に記載の電力測定方法は、主系統の三相３線式の三相交流電線から複数の三相交流電線が分岐し、それらの分岐のそれぞれに負荷が設けられているとき、分岐のそれぞれについて電力を測定する方法を対象としている。特許文献３に記載の方法では、主系統の三相交流電線に設ける主装置と、それぞれの分岐の三相交流電線に設ける個別計測装置とによって電力を測定するようにしているが、線間電圧の測定は主装置においてのみ、つまり主系統の三相交流電線においてのみ実施し、それぞれの個別計測装置においては、その分岐の三相交流電線の線電流のみ測定する。そして主装置は測定した線間電圧の波形から、そのゼロクロス点のタイミングと正負の極性を抽出してそれぞれの個別計測装置に送信する。個別計測装置においてはこれを受信して、仮の実効値を与えて仮想的な線間電圧の電圧波形を計算し、この仮想的な電圧波形と、実際に測定した線電流とから仮想的な電力を計算する。そして最後に、主装置で検出される三相交流電圧の実効値をもとに、仮想的な電力から正確な電力を計算する。このようにすると、線間電圧については主系統でのみ測定すればいいので、電圧センサの個数が少なくて済み、コストが小さくなる。 In the power measurement method described in Patent Document 3, when a plurality of three-phase AC wires are branched from a three-phase three-wire AC wire of the main system and a load is provided for each of those branches, It is intended to measure the power for each of the above. In the method described in Patent Document 3, the power is measured by the main device provided in the three-phase AC electric wire of the main system and the individual measuring device provided in the three-phase AC electric wire of each branch. Is measured only in the main device, that is, only in the three-phase AC wires of the main system, and in each individual measuring device, only the line current of the three-phase AC wires in the branch is measured. Then, the main device extracts the timing of the zero cross point and the positive / negative polarity from the measured waveform of the line voltage, and transmits it to each individual measuring device. The individual measuring device receives this, gives a temporary effective value, calculates a voltage waveform of a virtual line voltage, and calculates a virtual waveform from this virtual voltage waveform and the actually measured line current. Calculate power. Finally, accurate power is calculated from virtual power based on the effective value of the three-phase AC voltage detected by the main device. In this way, since the line voltage needs to be measured only in the main system, the number of voltage sensors can be reduced and the cost can be reduced.

従来の、２組の線間における線間電圧と２線における線電流とを測定して２電力法によって電力を計算する方法も、特許文献１または２に記載の電力測定方法も、特許文献３に記載の電力測定方法も、適切に電力を計算することができる。そして、いずれの方法も負荷の種類に拘わらずに電力を計算することができ、それぞれ優れている。しかしながら、特定の条件下においては解決すべき問題も見受けられる。具体的には、負荷が抵抗のみからなる場合において、電力計算に必要なコストをさらに小さくできる余地が見受けられる。例えば射出成形機の射出装置に設けられているヒータは、三相交流電線に接続されて電力が供給される負荷であり、抵抗のみからなる。このように負荷が抵抗のみからなる場合に、電力を測定するのに要するコストを小さくしたい。従来の電力測定方法においては、少なくとも２個の電圧センサと２個の電流センサが必要になり、センサ個数が多くコストは大きい。特許文献１または２に記載の電力測定方法では、１個の電圧センサと２個の電流センサだけで電力が測定できるので、センサの個数は従来の電力測定方法に比して１個少なくて済むが、さらにコストを小さくできる余地はありそうである。特許文献３に記載の電力測定方法では電圧センサは主装置にのみ設ければよく、個別計測装置では省略できるのでコストをある程度小さくすることはできるが、少なくとも主装置においては２組の線間電圧を測定するために２個の電圧センサは必要であるので、これもさらにコストを小さくできる余地がありそうである。 The conventional method for calculating the power by the two-power method by measuring the line voltage between the two sets of lines and the line current in the two wires, and the power measurement method described in Patent Document 1 or 2, are also disclosed in Patent Document 3. The power measurement method described in 1 can also calculate power appropriately. Each method can calculate electric power regardless of the type of load, and each method is excellent. However, there are also problems to be solved under certain conditions. Specifically, when the load consists only of resistance, there is room for further reducing the cost required for power calculation. For example, a heater provided in an injection device of an injection molding machine is a load that is connected to a three-phase AC electric wire and supplied with electric power, and consists only of a resistor. In this way, when the load consists only of a resistor, it is desired to reduce the cost required for measuring the power. In the conventional power measuring method, at least two voltage sensors and two current sensors are required, and the number of sensors is large and the cost is high. In the power measurement method described in Patent Document 1 or 2, since power can be measured using only one voltage sensor and two current sensors, the number of sensors can be reduced by one as compared with the conventional power measurement method. However, there seems to be room for further cost reduction. In the power measurement method described in Patent Document 3, the voltage sensor only needs to be provided in the main device and can be omitted in the individual measurement device, so that the cost can be reduced to some extent. Since two voltage sensors are required to measure the current, there is a possibility that this can be further reduced in cost.

本発明は、上記したような問題点を解決した、電力測定方法を提供することを目的としており、具体的には、三相交流電流によって抵抗のみからなる負荷に電力を供給するときに、小コストで電力を測定できる電力測定方法を提供することを目的としている。 An object of the present invention is to provide a power measurement method that solves the above-described problems. Specifically, when power is supplied to a load composed only of a resistor by a three-phase alternating current, a small amount is provided. The object is to provide a power measurement method capable of measuring power at a low cost.

本発明は、上記目的を達成するために、Ｒ線、Ｓ線、Ｔ線からなる三相３線式の三相交流電線において、複数個の抵抗のみからなる負荷が接続されているときの電力測定方法として構成される。このような抵抗は、Ｒ線−Ｓ線間、Ｓ線−Ｔ線間、Ｔ線−Ｒ線間のそれぞれに接続されて独立してＯＮ／ＯＦＦされるようになっている。電力測定方法は、２電力法によって計算するようにし、まずＲ線の線電流とＳ線の線電流は、Ｒ線とＳ線のそれぞれに設けた電流センサによって検出する。しかしながらＲ線−Ｔ線間の線間電圧、Ｓ線−Ｔ線間の線間電圧は、センサによってではなく計算によって得るようにする。具体的には、Ｒ線−Ｔ線間の線間電圧は、Ｒ線−Ｓ線間の抵抗がＯＦＦでＲ線−Ｓ線間が不導通のときに、Ｒ線の線電流にＲ線−Ｔ線間のＯＮ状態の抵抗の抵抗値を乗じて電圧波形を得る。そしてＲ線−Ｓ線間の抵抗がＯＮでＲ線−Ｓ線間が導通しているときも該電圧波形が同位相と振幅で継続すると見なす。Ｓ線−Ｔ線間の線間電圧も同様に計算によって得るようにし、Ｒ線−Ｓ線間の抵抗がＯＦＦでＲ線−Ｓ線間が不導通のときはＳ線の線電流にＳ線−Ｔ線間のＯＮ状態の抵抗の抵抗値を乗じて電圧波形を得る。そしてＲ線−Ｓ線間の抵抗がＯＮでＲ線−Ｓ線間が導通しているときも該電圧波形が同位相と振幅で継続すると見なす。このようにして得られたＲ線の線電流とＳ線の線電流とＲ線−Ｔ線間の線間電圧とＳ線−Ｔ線間の線間電圧とから２電力法によって負荷の電力を得る。 In order to achieve the above object, the present invention is a three-phase three-wire type three-phase AC electric wire composed of an R line, an S line, and a T line, and an electric power when a load consisting only of a plurality of resistors is connected. Configured as a measurement method. Such resistors are connected to the R line-S line, the S line-T line, and the T line-R line, respectively, and are turned ON / OFF independently. The power measurement method is calculated by the two-power method. First, the line current of the R line and the line current of the S line are detected by current sensors provided for the R line and the S line, respectively. However, the line voltage between the R line and the T line and the line voltage between the S line and the T line are obtained not by the sensor but by calculation. Specifically, the line-to-line voltage between the R line and the T line is the same as the line current of the R line when the resistance between the R line and the S line is OFF and the R line and the S line are not conductive. A voltage waveform is obtained by multiplying the resistance value of the ON-state resistance between the T lines. When the resistance between the R line and the S line is ON and the connection between the R line and the S line is conductive, the voltage waveform is considered to continue with the same phase and amplitude. Similarly, the line voltage between the S line and the T line is obtained by calculation. When the resistance between the R line and the S line is OFF and the line between the R line and the S line is not conductive, the line current of the S line is converted into the S line. A voltage waveform is obtained by multiplying the resistance value of the ON-state resistance between the -T lines. When the resistance between the R line and the S line is ON and the connection between the R line and the S line is conductive, the voltage waveform is considered to continue with the same phase and amplitude. The load power is calculated by the two-power method from the line current of the R line, the line current of the S line, the line voltage between the R line and the T line, and the line voltage between the S line and the T line thus obtained. obtain.

かくして、請求項１に記載の発明は、上記目的を達成するために、Ｒ線、Ｓ線、Ｔ線からなる三相３線式の三相交流電線において、Ｒ線−Ｓ線間、Ｓ線−Ｔ線間、Ｔ線−Ｒ線間のそれぞれに接続されて独立してＯＮ／ＯＦＦされる複数個の抵抗からなる負荷について、その電力を得る電力測定方法であって、Ｒ線の線電流とＳ線の線電流は、Ｒ線とＳ線のそれぞれに設けた電流センサによって検出するようにし、Ｒ線−Ｔ線間の線間電圧は、Ｒ線−Ｓ線間の抵抗がＯＦＦでＲ線−Ｓ線間が不導通のときは前記Ｒ線の線電流にＲ線−Ｔ線間のＯＮ状態の抵抗の抵抗値を乗じて電圧波形を得、そしてＲ線−Ｓ線間の抵抗がＯＮでＲ線−Ｓ線間が導通しているときも該電圧波形が同位相と振幅で継続すると見なし、Ｓ線−Ｔ線間の線間電圧は、Ｒ線−Ｓ線間の抵抗がＯＦＦでＲ線−Ｓ線間が不導通のときは前記Ｓ線の線電流にＳ線−Ｔ線間のＯＮ状態の抵抗の抵抗値を乗じて電圧波形を得、そしてＲ線−Ｓ線間の抵抗がＯＮでＲ線−Ｓ線間が導通しているときも該電圧波形が同位相と振幅で継続すると見なし、前記Ｒ線の線電流と、前記Ｓ線の線電流と、前記Ｒ線−Ｔ線間の線間電圧と、前記Ｓ線−Ｔ線間の線間電圧とから２電力法によって前記負荷の電力を得ることを特徴とする電力測定方法として構成される。
請求項２に記載の発明は、請求項１に記載の方法において、前記Ｒ線−Ｔ線間の線間電圧の電圧波形を得るとき、その電圧値がゼロになる所定のゼロクロス点から次のゼロクロス点までの半周期分または所定のゼロクロス点から２個先のゼロクロス点までの１周期分について得てこれを標準電圧波形とし、Ｒ線−Ｓ線間の抵抗がＯＮでＲ線−Ｓ線間が導通しているときは該標準電圧波形が同位相と振幅で継続すると見なすようにし、前記Ｓ線−Ｔ線間の線間電圧の電圧波形を得るとき、所定のゼロクロス点から次のゼロクロス点までの半周期分または所定のゼロクロス点から２個先のゼロクロス点までの１周期分について得てこれを標準電圧波形とし、Ｒ線−Ｓ線間の抵抗がＯＮでＲ線−Ｓ線間が導通しているときは該標準電圧波形が同位相と振幅で継続すると見なすようにすることを特徴とする電力測定方法として構成される。
請求項３に記載の発明は、請求項１または２に記載の方法において、前記負荷が複数の単相ヒータからなることを特徴とするヒータの電力測定方法として構成される。
請求項４に記載の発明は、Ｒ線、Ｓ線、Ｔ線からなる三相３線式の三相交流電線において、Ｒ線−Ｓ線間、Ｓ線−Ｔ線間、Ｔ線−Ｒ線間のそれぞれに接続されて独立してＯＮ／ＯＦＦされる複数個の抵抗からなる負荷の電力を測定する電力測定装置であって、前記電力測定装置は、Ｒ線とＳ線のそれぞれに設けられている電流センサを備え、請求項１〜３のいずれかの方法によって前記負荷の電力を測定することを特徴とする電力測定装置として構成される。 Thus, in order to achieve the above object, the invention according to claim 1 is a three-phase three-wire three-phase AC electric wire composed of an R line, an S line, and a T line. A power measurement method for obtaining the power of a load comprising a plurality of resistors connected to each other between -T lines and between T lines and R lines and independently turned ON / OFF, wherein R line current The line current between the R line and the S line is detected by a current sensor provided on each of the R line and the S line, and the line voltage between the R line and the T line is R when the resistance between the R line and the S line is OFF. When the line-S line is not conductive, the line current of the R line is multiplied by the resistance value of the ON-state resistance between the R line-T line to obtain a voltage waveform, and the resistance between the R line-S line is Even when the line between the R line and the S line is ON, the voltage waveform is considered to continue with the same phase and amplitude, and the line voltage between the S line and the T line is represented by the R line. When the resistance between the S lines is OFF and the R line and the S line are not conductive, a voltage waveform is obtained by multiplying the line current of the S line by the resistance value of the ON state resistance between the S line and the T line, and When the resistance between the R line and the S line is ON and the connection between the R line and the S line is conducted, the voltage waveform is assumed to continue with the same phase and amplitude, and the line current of the R line and the line of the S line The power measurement method is characterized in that the power of the load is obtained by a two-power method from a current, a line voltage between the R line and the T line, and a line voltage between the S line and the T line. The
According to a second aspect of the present invention, in the method of the first aspect, when the voltage waveform of the line voltage between the R line and the T line is obtained, the voltage value becomes zero from a predetermined zero crossing point. A half-cycle to the zero-cross point or one cycle from the predetermined zero-cross point to the next zero-cross point is obtained as a standard voltage waveform, the resistance between the R-line and S-line is ON, and the R-line-S-line When the gap is conductive, the standard voltage waveform is assumed to continue with the same phase and amplitude, and when the voltage waveform of the line voltage between the S line and the T line is obtained, the next zero cross from the predetermined zero cross point is obtained. A half-cycle to a point or one cycle from a predetermined zero-cross point to the next zero-cross point is obtained as a standard voltage waveform, the resistance between the R line and the S line is ON, and the line between the R line and the S line is ON. Is in phase, the standard voltage waveform is in phase Configured as a power measurement method, characterized by so considered to continue in amplitude.
According to a third aspect of the present invention, in the method according to the first or second aspect, the load is composed of a plurality of single-phase heaters.
The invention according to claim 4 is a three-phase three-wire type three-phase AC electric wire composed of an R line, an S line, and a T line. A power measuring device for measuring the power of a load comprising a plurality of resistors connected to each other and independently turned ON / OFF, wherein the power measuring device is provided for each of the R line and the S line. The power sensor is configured to measure the power of the load by the method according to any one of claims 1 to 3.

以上のように、本願発明によると、Ｒ線、Ｓ線、Ｔ線からなる三相３線式の三相交流電線において、Ｒ線−Ｓ線間、Ｓ線−Ｔ線間、Ｔ線−Ｒ線間のそれぞれに接続されて独立してＯＮ／ＯＦＦされる複数個の抵抗からなる負荷について、その電力を得る電力測定方法として構成されている。つまり本発明の電力測定方法は、三相３線式の三相交流電線によって、抵抗のみからなる負荷に電力を供給する場合を対象としている。そして本発明によると、Ｒ線の線電流とＳ線の線電流は、Ｒ線とＳ線のそれぞれに設けた電流センサによって検出するようにしている。つまり電流センサは２個必要になる。しかしながら本発明によると、Ｒ線−Ｔ線間の線間電圧は、Ｒ線−Ｓ線間の抵抗がＯＦＦでＲ線−Ｓ線間が不導通のときはＲ線の線電流にＲ線−Ｔ線間のＯＮ状態の抵抗の抵抗値を乗じて電圧波形を得、そしてＲ線−Ｓ線間の抵抗がＯＮでＲ線−Ｓ線間が導通しているときも該電圧波形が同位相と振幅で継続すると見なす。つまりＲ線−Ｔ線間の線間電圧を測定するために格別に電圧センサを必要としない。同様にＳ線−Ｔ線間の線間電圧は、Ｒ線−Ｓ線間の抵抗がＯＦＦでＲ線−Ｓ線間が不導通のときはＳ線の線電流にＳ線−Ｔ線間のＯＮ状態の抵抗の抵抗値を乗じて電圧波形を得、そしてＲ線−Ｓ線間の抵抗がＯＮでＲ線−Ｓ線間が導通しているときも該電圧波形が同位相と振幅で継続すると見なす。つまりＳ線−Ｔ線間の線間電圧も、格別に電圧センナを必要とせずに得られる。本発明は、このようにして得られたＲ線の線電流と、Ｓ線の線電流と、Ｒ線−Ｔ線間の線間電圧と、Ｓ線−Ｔ線間の線間電圧とから２電力法によって負荷の電力を得るように構成されているので、必要とするセンサは２個の電流センサだけで済む。電力測定に要するコストが小さいという本発明に特有の効果が得られる。 As described above, according to the present invention, in a three-phase three-wire type three-phase AC electric wire composed of an R line, an S line, and a T line, between the R line and the S line, between the S line and the T line, and between the T line and the R line. It is configured as a power measuring method for obtaining power of a load composed of a plurality of resistors connected to each other between the lines and independently turned on / off. That is, the power measurement method of the present invention is intended for the case where power is supplied to a load consisting only of resistance by a three-phase three-wire three-phase AC electric wire. According to the present invention, the line current of the R line and the line current of the S line are detected by the current sensors provided for each of the R line and the S line. That is, two current sensors are required. However, according to the present invention, the line voltage between the R line and the T line is such that the resistance between the R line and the S line is OFF and the connection between the R line and the S line is non-conductive. The voltage waveform is obtained by multiplying the resistance value of the ON-state resistance between the T lines, and when the resistance between the R line and the S line is ON and the R line and the S line are conductive, the voltage waveform is in phase. And continue with amplitude. That is, no special voltage sensor is required to measure the line voltage between the R line and the T line. Similarly, the line-to-line voltage between the S-line and the T-line is the S-line current between the S-line and the T-line when the resistance between the R-line and the S-line is OFF and the R-line and the S-line are non-conductive. The voltage waveform is obtained by multiplying the resistance value of the resistance in the ON state, and the voltage waveform continues with the same phase and amplitude even when the resistance between the R line and the S line is ON and the connection between the R line and the S line is conducted. I think that. That is, the line voltage between the S line and the T line can also be obtained without requiring a voltage senna. According to the present invention, the line current of the R line, the line current of the S line, the line voltage between the R line and the T line, and the line voltage between the S line and the T line thus obtained are Since the power of the load is obtained by the power method, only two current sensors are required. An effect peculiar to the present invention that the cost required for power measurement is small can be obtained.

他の発明によると、Ｒ線−Ｔ線間の線間電圧の電圧波形を得るとき、その電圧値がゼロになる所定のゼロクロス点から次のゼロクロス点までの半周期分または所定のゼロクロス点から２個先のゼロクロス点までの１周期分について得てこれを標準電圧波形とし、Ｒ線−Ｓ線間の抵抗がＯＮでＲ線−Ｓ線間が導通しているときは該標準電圧波形が同位相と振幅で継続すると見なすようにし、Ｓ線−Ｔ線間の線間電圧の電圧波形を得るとき、所定のゼロクロス点から次のゼロクロス点までの半周期分または所定のゼロクロス点から２個先のゼロクロス点までの１周期分について得てこれを標準電圧波形とし、Ｒ線−Ｓ線間の抵抗がＯＮでＲ線−Ｓ線間が導通しているときは該標準電圧波形が同位相と振幅で継続すると見なすように構成されている。このようにすると、少なくとも標準電圧波形について記憶するようにするだけで、仮想的に電圧波形を生成することができるので、さらに電力測定方法がシンプルになる。 According to another invention, when the voltage waveform of the line voltage between the R line and the T line is obtained, from the predetermined zero cross point where the voltage value becomes zero to the next zero cross point or from the predetermined zero cross point Obtained for one cycle up to the next zero cross point, and this is used as a standard voltage waveform. When the resistance between R line and S line is ON and the connection between R line and S line is conductive, the standard voltage waveform is When obtaining the voltage waveform of the line voltage between the S-line and the T-line so as to continue with the same phase and amplitude, two half-cycles from the predetermined zero cross point to the next zero cross point or two from the predetermined zero cross point Obtained for one period up to the previous zero cross point, this is used as a standard voltage waveform, and when the resistance between R line and S line is ON and the connection between R line and S line is conductive, the standard voltage waveform is in phase And is configured to be considered to continue at amplitudeIn this way, since it is possible to virtually generate a voltage waveform only by storing at least the standard voltage waveform, the power measurement method is further simplified.

複数の抵抗が接続された三相３線式の三相交流電線に設けられている、本発明の実施の形態に係る電力測定装置の一部を示す図で、その（ア）〜（エ）は、各抵抗のＯＮ／ＯＦＦ状態が異なる４種類のケースのそれぞれについて示す、電力測定装置の一部を示す回路図である。It is a figure which shows a part of power measuring device which concerns on embodiment of this invention provided in the three-phase three-wire type | system | group three-phase alternating current electric wire to which several resistance was connected, The (a)-(e) These are circuit diagrams which show a part of electric power measurement apparatus shown about each of four types of cases from which the ON / OFF state of each resistance differs. 複数の抵抗が接続された三相３線式の三相交流電線に設けられている、本発明の実施の形態に係る電力測定装置の一部を示す回路図である。It is a circuit diagram showing a part of a power measuring device concerning an embodiment of the present invention provided in a three-phase three-wire type three-phase AC electric wire to which a plurality of resistances are connected. 本発明の実施の形態に係る電力測定方法において測定されるＲ線、Ｓ線の線電流と、計算によって得られるＲ線−Ｔ線間、Ｓ線−Ｔ線間の線間電流を示すグラフである。It is a graph which shows the line current of R line | wire and S line | wire measured in the electric power measurement method which concerns on embodiment of this invention, and the line | wire current between R line | wire and T line | wire obtained by calculation, and between S line | wire and T line | wire. is there. 本発明の実施の形態に係る電力測定方法において計算によって得られるＲ線−Ｔ線間の線間電流を示すグラフである。It is a graph which shows the line-to-line current between R line | wire and T line obtained by calculation in the electric power measurement method which concerns on embodiment of this invention.

以下、本発明の実施の形態について説明する。本発明の実施の形態に係る電力測定装置１は、図１の（ア）に示されているように、Ｒ線、Ｓ線、Ｔ線からなる三相３線式の三相交流電線に設けられている。そして、電力測定装置１が電力を測定する対象の負荷は、独立してＯＮ／ＯＦＦされる抵抗２、３、４のみからなる。本実施の形態において、抵抗２、３、４はいわゆるＰＷＭ制御によりＯＮ／ＯＦＦされるヒータ２、３、４からなる。つまり、本実施の形態に係る電力測定装置１は複数個のヒータからなる負荷の電力を測定する電力測定装置になっている。これらのヒータ２、３、４はＲ線、Ｓ線、Ｔ線のそれぞれ２線間、つまりＲ線−Ｓ線間、Ｓ線−Ｔ線間、Ｔ線−Ｒ線間に接続されている。ところで図１の（ア）においては、任意の２線間に接続されているヒータは１個のみから構成されているように示されている。もちろんそれぞれの２線間にヒータが１個のみ接続されるようにしてもいいが、一般的にはそれぞれの２線間に複数個のヒータが並列に接続されている。例えば図２に示されているように、Ｒ線−Ｓ線間に３個のヒータ２ａ、２ｂ、２ｃが並列に接続され、Ｓ線−Ｔ線間に３個のヒータ３ａ、３ｂ、３ｃが接続され、Ｔ線−Ｒ線間に２個のヒータ４ａ、４ｂが接続されている。図１の（ア）に示されているヒータ２、３、４は、それぞれ図２に示されているように並列に接続された複数個のヒータ２ａ、２ｂ、…４ａ、４ｂを簡略化して示したものになっている。これらのヒータ２ａ、２ｂ、…は、図に示されていないソリッドステートリレーによって独立してＯＮ／ＯＦＦされるようになっている。図２において、ヒータ２ａ、２ｂ、２ｃ、３ｃ、４ｂはＯＦＦされている状態を、ヒータ３ａ、３ｂ、４ａはＯＮされている状態が示されているが、これによってＲ線−Ｓ線間が不導通の状態に、Ｓ線−Ｔ線間、Ｔ線−Ｒ線間は導通した状態になっている。この状態を簡略的に示した図が図１の（イ）である。つまり、ヒータ２がＯＦＦでＲ線−Ｓ線間が不導通の状態に、ヒータ３、４がＯＮでＳ線−Ｔ線間、Ｔ線−Ｒ線間が導通の状態になっている。 Embodiments of the present invention will be described below. As shown in FIG. 1A, the power measuring device 1 according to the embodiment of the present invention is provided on a three-phase three-wire type three-phase AC electric wire composed of an R line, an S line, and a T line. It has been. The load on which the power measuring device 1 measures power consists of only the resistors 2, 3, and 4 that are independently turned ON / OFF. In the present embodiment, the resistors 2, 3, 4 are composed of heaters 2, 3, 4 that are turned on / off by so-called PWM control. That is, the power measuring apparatus 1 according to the present embodiment is a power measuring apparatus that measures the power of a load composed of a plurality of heaters. These heaters 2, 3, and 4 are connected between two R lines, S lines, and T lines, that is, between R lines and S lines, between S lines and T lines, and between T lines and R lines. Incidentally, in FIG. 1A, the heater connected between any two wires is shown to be composed of only one. Of course, only one heater may be connected between each two lines, but generally a plurality of heaters are connected in parallel between each two lines. For example, as shown in FIG. 2, three heaters 2a, 2b, and 2c are connected in parallel between the R line and the S line, and three heaters 3a, 3b, and 3c are connected between the S line and the T line. Two heaters 4a and 4b are connected between the T line and the R line. The heaters 2, 3 and 4 shown in FIG. 1A are simplified from the plurality of heaters 2a, 2b,... 4a and 4b connected in parallel as shown in FIG. It is what is shown. These heaters 2a, 2b,... Are independently turned ON / OFF by a solid state relay (not shown). In FIG. 2, the heaters 2a, 2b, 2c, 3c, and 4b are turned off, and the heaters 3a, 3b, and 4a are turned on. In a non-conductive state, the S line and the T line and the T line and the R line are in a conductive state. FIG. 1A shows a simplified diagram of this state. That is, the heater 2 is OFF and the R line and the S line are in a non-conductive state, and the heaters 3 and 4 are ON and the S line and the T line are in a conductive state.

本実施の形態に係る電力測定装置１は、Ｒ線とＳ線のそれぞれに設けられている２個の電流センサ６、７と、図に示されていないコントローラとから構成されている。コントローラは、電流センサ６、７によって検出されるＲ線、Ｓ線の線電流が入力され、そしてヒータ２、３、４、つまりヒータ２ａ、２ｂ、…４ａ、４ｂのそれぞれの抵抗値が記憶されている。またコントローラは、ヒータ２ａ、２ｂ、…４ａ、４ｂのＯＮ／ＯＦＦ状態が検出できるようになっている。本実施の形態においてはヒータ２ａ、２ｂ、…４ａ、４ｂをＰＷＭ制御しているのは、このコントローラでもあるので、コントローラは当然にＯＮ／ＯＦＦ状態を検出できる。 The power measuring apparatus 1 according to the present embodiment is composed of two current sensors 6 and 7 provided on each of the R line and the S line, and a controller not shown in the figure. The controller receives R and S line currents detected by the current sensors 6 and 7, and stores the resistance values of the heaters 2, 3, and 4, that is, the heaters 2a, 2b,. ing. The controller can detect the ON / OFF states of the heaters 2a, 2b,... 4a, 4b. In this embodiment, it is also this controller that PWM-controls the heaters 2a, 2b,... 4a, 4b, so that the controller can naturally detect the ON / OFF state.

一般的に、三相３線式の三相交流電線から負荷に電力を供給するとき、合計の電力はいわゆる２電力法によって計算することができ、この場合２線における線電流と２組の線間電圧とが必要になる。本実施の形態に係る電力測定方法も２電力法により電力を計算するが、２組の線間電圧は直接測定せず、計算によって得るようにする点に特徴がある。計算によって得ることが可能であるのは、電力を測定する対象の負荷が抵抗のみから、つまりヒータ２、３、４のみからなるからである。負荷が抵抗のみから構成されているので、抵抗のＯＮ／ＯＦＦが所定の状態になっているときに電流と電圧の位相が一致する。具体的には、図１の（イ）、図２に示されているように、Ｒ線−Ｓ線間のヒータ２、つまりヒータ２ａ、２ｂ、２ｃがＯＦＦされてＲ線−Ｓ線間が不導通の状態において、Ｒ線の線電流とＲ線−Ｔ線間の線間電圧、そしてＳ線の線電流とＳ線−Ｔ線間の線間電圧のそれぞれが完全に位相が一致する。その理由は、Ｒ線−Ｓ線間が不導通の状態においては、Ｒ線の線電流はＲ線−Ｔ線間にのみ、Ｓ線の線電流はＳ線−Ｔ線間にのみそれぞれ流れ、負荷には位相の進みや遅れを生じさせるコンデンサやリアクタンスが含まれないからである。本実施の形態に係る電力測定方法では、このようにＲ線−Ｓ線間が不導通の状態のときに、Ｒ線、Ｓ線のそれぞれの線電流からＲ線−Ｔ線間とＳ線−Ｔ線間の線間電圧の電圧波形を計算で得るようにする。そしてＲ線−Ｓ線が導通状態になっているときには、計算で得た電圧波形が同位相と振幅で継続すると見なすようにする。これによって２電力法で電力を計算することができる。 In general, when power is supplied to a load from a three-phase three-wire three-phase AC power line, the total power can be calculated by the so-called two-power method, in which case the line current in two lines and two sets of lines Voltage is required. The power measurement method according to this embodiment also calculates power by the two-power method, but is characterized in that two sets of line voltages are not directly measured but are obtained by calculation. It is possible to obtain by calculation because the load to be measured for electric power consists only of the resistance, that is, only the heaters 2, 3, and 4. Since the load is composed only of the resistor, the phase of the current and the voltage coincide with each other when the resistor is turned on / off in a predetermined state. Specifically, as shown in FIG. 1A and FIG. 2, the heater 2 between the R line and the S line, that is, the heaters 2a, 2b, and 2c are turned off so that the distance between the R line and the S line is reduced. In the non-conductive state, the phase of the line current of the R line and the line voltage between the R line and the T line, and the line current of the S line and the line voltage between the S line and the T line completely match each other. The reason for this is that, when the R-line and the S-line are not conductive, the R-line current flows only between the R-line and the S-line, and the S-line current flows only between the S-line and T-line, This is because the load does not include a capacitor or reactance that causes a phase advance or delay. In the power measurement method according to the present embodiment, when the line between the R line and the S line is in a non-conductive state as described above, the line current between the R line and the S line is calculated from the line between the R line and the T line and the line S. The voltage waveform of the line voltage between the T lines is obtained by calculation. When the R-line-S-line is in a conductive state, it is assumed that the voltage waveform obtained by calculation continues with the same phase and amplitude. As a result, power can be calculated by the two-power method.

図３のグラフも参照して、本実施の形態に係る電力測定方法を詳しく説明する。本実施の形態に係る電力測定装置１では、電流センサ６、７によって常時Ｒ線の線電圧、Ｓ線の線電流がサンプリングされてコントローラに入力されている。サンプリングされているＲ線、Ｓ線の線電流は符号１１、１２のグラフで示されている。各ヒータ２、３、４は前記したようにＰＷＭ制御によりＯＮ／ＯＦＦされているので、図１の（イ）、図２に示されているように、ヒータ２つまりヒータ２ａ、２ｂ、２ｃが全てＯＦＦされる状態が発生する。もし、ヒータ２ａ、２ｂ、２ｃが同時にＯＦＦされる状態が発生しなければ、強制的に所定の時間だけこれらをＯＦＦするようにする。このようにヒータ２つまりヒータ２ａ、２ｂ、２ｃがＯＦＦされているとき、Ｒ線−Ｓ線間が不導通の状態になる。図３のグラフにおいて、符号１４、１５の区間がＲ線−Ｓ線間が不導通の状態になっている。この区間においてはＲ線の線電圧とＲ線−Ｔ線間の線間電圧、そしてＳ線の線電圧とＳ線−Ｔ線間の線間電圧のそれぞれの位相が一致する。そこでこの区間１４、１５において、次式によって線間電圧を得る。
Ｒ線−Ｔ線間の線間電圧＝Ｒ線の線電流×ヒータ４の抵抗値
Ｓ線−Ｔ線間の線間電圧＝Ｓ線の線電流×ヒータ３の抵抗値
ただし、ヒータ４の抵抗値は、Ｒ線−Ｔ線間の全てのヒータ４ａ、４ｂのうちＯＮ状態のヒータの合成抵抗値であり、ヒータ３の抵抗値はヒータ３ａ、３ｂ、３ｃのうちＯＮ状態のヒータの合成抵抗値である。図３において、上の式で得たＲ線−Ｔ線間の線間電圧の電圧波形が符号１８の実線のグラフで、Ｓ線−Ｔ線間の線間電圧の電圧波形が符号１９の実線のグラフで示されている。これらのグラフ１８、１９は曲線で示されているが、実際にはＲ線、Ｓ線の線電流はサンプリング値として検出されるので、Ｒ線−Ｔ線間の線間電圧もＳ線−Ｔ線間の線間電圧も図４に示されているような複数個のサンプリング値として得られることになる。 The power measurement method according to the present embodiment will be described in detail with reference to the graph of FIG. In the power measuring apparatus 1 according to the present embodiment, the current sensors 6 and 7 always sample the line voltage of the R line and the line current of the S line and input them to the controller. The line currents of the R line and S line being sampled are shown by the graphs 11 and 12. Since the heaters 2, 3, and 4 are turned on / off by PWM control as described above, the heater 2, that is, the heaters 2a, 2b, and 2c, as shown in FIG. A state where all are turned off occurs. If the state where the heaters 2a, 2b and 2c are simultaneously turned off does not occur, they are forcibly turned off for a predetermined time. Thus, when the heater 2, that is, the heaters 2a, 2b, and 2c are turned off, the R-line and the S-line are in a non-conductive state. In the graph of FIG. 3, the sections 14 and 15 are in a non-conductive state between the R line and the S line. In this section, the phases of the line voltage of the R line and the line voltage between the R line and the T line, and the line voltage of the S line and the line voltage between the S line and the T line coincide with each other. Therefore, in these sections 14 and 15, the line voltage is obtained by the following equation.
Line voltage between R line and T line = Line current of R line × resistance value of heater 4 Line voltage between S line and T line = Line current of S line × resistance value of heater 3 However, resistance of heater 4 The value is the combined resistance value of the heaters in the ON state among all the heaters 4a, 4b between the R line and the T line, and the resistance value of the heater 3 is the combined resistance value of the heaters in the ON state of the heaters 3a, 3b, 3c. Value. In FIG. 3, the voltage waveform of the line voltage between the R line and the T line obtained by the above equation is a solid line graph 18, and the voltage waveform of the line voltage between the S line and the T line is a solid line 19. Is shown in the graph. Although these graphs 18 and 19 are shown as curves, since the line currents of the R line and S line are actually detected as sampling values, the line voltage between the R line and T line is also S line -T. The line-to-line voltage is also obtained as a plurality of sampling values as shown in FIG.

本実施の形態に係る電力測定方法では、このようにして計算で得られたＲ線−Ｔ線間の線間電圧の電圧波形とＳ線−Ｔ線間の線間電圧の電圧波形のそれぞれは、Ｒ線−Ｔ線間が導通状態になっても、同位相かつ同振幅で継続するものとみなす。そうすると、符号２１、２２の二点鎖線のグラフで示されているようにＲ線−Ｔ線間の線間電圧の電圧波形とＳ線−Ｔ線間の線間電圧の電圧波形が得られる。 In the power measurement method according to the present embodiment, the voltage waveform of the line voltage between the R line and the T line and the voltage waveform of the line voltage between the S line and the T line obtained in this way are respectively , Even if the connection between the R line and the T line is in a conductive state, it is considered to continue with the same phase and the same amplitude. Then, the voltage waveform of the line voltage between the R line and the T line and the voltage waveform of the line voltage between the S line and the T line are obtained as shown by the two-dot chain line graphs of reference numerals 21 and 22.

もちろん、このようにして符号２１、２２の二点鎖線のグラフのようなＲ線−Ｔ線間の線間電圧の電圧波形とＳ線−Ｔ線間の線間電圧の電圧波形を得てもいいが、本実施の形態に係る電力測定方法では、さらに工夫している。つまりこれらの符号２１、２２の電圧波形は、次のような標準電圧波形から得るようにする。標準電圧波形とはＲ線−Ｓ線間が不導通の期間において、Ｒ線−Ｔ線間の線間電圧やＳ線−Ｔ線間の線間電圧の電圧値がゼロになる所定のゼロクロス点から次のゼロクロス点までの半周期分の電圧波形、もしくは所定のゼロクロス点から２個先のゼロクロス点までの１周期分の電圧波形のことをいう。まず、区間１４、１５において、符号１８、１９で示されているＲ線−Ｔ線間の線間電圧とＳ線−Ｔ線間の線間電圧のそれぞれの電圧波形から標準電圧波形を抽出する。図４のグラフは、Ｓ線−Ｔ線間の線間電圧の半周期分の標準電圧波形を示している。そして、本実施の形態に係る電力測定方法では、このような標準電圧波形が、Ｒ線−Ｓ線間が導通状態になっているときも同位相でかつ同振幅で継続するとみなし、符号２１、２２で示されているＲ線−Ｔ線間の線間電圧の電圧波形とＳ線−Ｔ線間の線間電圧の電圧波形を得る。 Of course, even if the voltage waveform of the line voltage between the R line and the T line and the voltage waveform of the line voltage between the S line and the T line are obtained in this way, like the two-dot chain line graphs of reference numerals 21 and 22. The power measurement method according to the present embodiment is further devised. That is, the voltage waveforms of these symbols 21 and 22 are obtained from the following standard voltage waveform. The standard voltage waveform is a predetermined zero cross point at which the voltage value of the line voltage between the R line and the T line and the voltage value of the line voltage between the S line and the T line becomes zero during a period in which the connection between the R line and the S line is not conductive. A voltage waveform corresponding to a half cycle from one to the next zero cross point or a voltage waveform corresponding to one cycle from a predetermined zero cross point to the next zero cross point. First, in the sections 14 and 15, the standard voltage waveform is extracted from the voltage waveforms of the line voltage between the R line and the T line and the line voltage between the S line and the T line indicated by reference numerals 18 and 19, respectively. . The graph of FIG. 4 shows a standard voltage waveform corresponding to a half cycle of the line voltage between the S line and the T line. In the power measurement method according to the present embodiment, such a standard voltage waveform is assumed to continue in the same phase and with the same amplitude even when the R-line and the S-line are in a conductive state. The voltage waveform of the line voltage between the R line and the T line indicated by 22 and the voltage waveform of the line voltage between the S line and the T line are obtained.

符号１６で示されているように、再びＲ線−Ｓ線間が不導通の状態になったら、前記した計算式によって、Ｒ線、Ｓ線の線電圧と、所定の抵抗値とからＲ線−Ｔ線間の線間電圧とＳ線−Ｔ線間の線間電圧とを得るようにし、それぞれの標準電圧波形を更新する。以後同様にしてＲ線−Ｔ線間の線間電圧とＳ線−Ｔ線間の線間電圧とを得る。このように繰り返し標準電圧波形を更新することによって、得られる線間電圧の精度を維持できることになる。 As indicated by reference numeral 16, when the R-line and the S-line are again brought into a non-conductive state, the R-line and the S-line voltage and the predetermined resistance value are calculated from the R-line and the S-line by the above-described calculation formula. The line voltage between the -T lines and the line voltage between the S lines and the T lines are obtained, and the respective standard voltage waveforms are updated. Thereafter, the line voltage between the R line and the T line and the line voltage between the S line and the T line are obtained in the same manner. Thus, by updating the standard voltage waveform repeatedly, the accuracy of the obtained line voltage can be maintained.

本実施の形態に係る電力測定装置１は、電流センサ６、７から検出されるＲ線の線電流とＳ線の線電流と、上記のようにして得られるＲ線−Ｔ線間の線間電圧とＳ線−Ｔ線間の線間電圧とから２電力法によって負荷の電力を計算する。 The power measuring apparatus 1 according to the present embodiment includes an R-line current and an S-line current detected from the current sensors 6 and 7 and a line spacing between the R-line and the T-line obtained as described above. The power of the load is calculated by the two power method from the voltage and the line voltage between the S line and the T line.

ところで、図１の（ウ）に示されているように、ヒータ４がＯＦＦでＲ線−Ｔ線間が不導通の状態のときには、Ｒ線−Ｓ線間が不導通であってもＲ線の線電流は検出できないのでＲ線−Ｔ線間の線間電圧はゼロになる。同様に図１の（エ）に示されているように、ヒータ３がＯＦＦでＳ線−Ｔ線間が不導通の状態のときには、Ｒ線−Ｓ線間が不導通であってもＳ線の線電流は検出できないのでＳ線−Ｔ線間の線間電圧はゼロになる。そうするとこれらのケースにおいては上で説明した標準電圧波形が得られないことになる。そこで、確実にＲ線−Ｔ線間の線間電圧の標準電圧波形を得るには、Ｒ線−Ｔ線間のヒータ２がＯＦＦでＲ線−Ｔ線間が不導通状態であり、かつＲ線−Ｔ線間のヒータ４がＯＮでＲ線−Ｔ線間が導通状態において得るようにすればよく、同様にＳ線−Ｔ線間の線間電圧の標準電圧波形を得るには、Ｒ線−Ｔ線間のヒータ２がＯＦＦでＲ線−Ｔ線間が不導通状態であり、かつＳ線−Ｔ線間のヒータ３がＯＮでＳ線−Ｔ線間が導通状態において得るようにすればよい。 By the way, as shown in FIG. 1C, when the heater 4 is OFF and the R line and the T line are in a non-conductive state, even if the R line and the S line are non-conductive, the R line Therefore, the line voltage between the R line and the T line becomes zero. Similarly, as shown in FIG. 1D, when the heater 3 is OFF and the S-line and the T-line are in a non-conductive state, the S-line even if the R-line and the S-line are non-conductive. Therefore, the line voltage between the S line and the T line becomes zero. Then, in these cases, the standard voltage waveform described above cannot be obtained. Therefore, in order to reliably obtain the standard voltage waveform of the line voltage between the R line and the T line, the heater 2 between the R line and the T line is OFF, the R line and the T line are in a non-conductive state, and R The heater 4 between the line and the T line may be turned on and the line between the R line and the T line may be obtained in a conductive state. Similarly, in order to obtain the standard voltage waveform of the line voltage between the S line and the T line, R So that the heater 2 between the line and the T line is OFF and the line between the R line and the T line is non-conductive, and the heater 3 between the S line and the T line is ON and the line between the S line and the T line is conductive. do it.

１電力測定装置
２、３、４ヒータ
６、７電流センサ 1 Electric power measuring device 2, 3, 4 Heater 6, 7 Current sensor

Claims

In a three-phase three-wire type three-phase AC cable consisting of R, S, and T lines, each is connected independently between R line and S line, between S line and T line, and between T line and R line. A power measurement method for obtaining the power of a load composed of a plurality of resistors that is turned ON / OFF.
The line current of the R line and the line current of the S line are detected by current sensors provided for each of the R line and the S line,
The line voltage between the R line and the T line is the ON current between the R line and the T line when the resistance between the R line and the S line is OFF and the R line and the S line are not conductive. The voltage waveform is obtained by multiplying the resistance value of the resistance in the state, and when the resistance between the R line and the S line is ON and the connection between the R line and the S line is continuous, the voltage waveform continues with the same phase and amplitude. Considered
The line-to-line voltage between the S line and the T line is the ON current between the S line and the T line when the resistance between the R line and the S line is OFF and the R line and the S line are not conductive. The voltage waveform is obtained by multiplying the resistance value of the resistance in the state, and when the resistance between the R line and the S line is ON and the connection between the R line and the S line is continuous, the voltage waveform continues with the same phase and amplitude. Considered
The load power is calculated from the line current of the R line, the line current of the S line, the line voltage between the R line and the T line, and the line voltage between the S line and the T line by a two-power method. A method for measuring power, characterized in that

The method of claim 1, wherein
When obtaining the voltage waveform of the line voltage between the R line and the T line, a half cycle from a predetermined zero cross point where the voltage value becomes zero to the next zero cross point or two zero crosses ahead from the predetermined zero cross point It is obtained for one cycle up to the point, and this is used as a standard voltage waveform. When the resistance between the R line and the S line is ON and the connection between the R line and the S line is conductive, the standard voltage waveform has the same phase and amplitude. Consider it to continue,
When obtaining the voltage waveform of the line voltage between the S-line and the T-line, about a half cycle from a predetermined zero cross point to the next zero cross point or one cycle from a predetermined zero cross point to the next zero cross point Obtain this as a standard voltage waveform. When the resistance between the R line and the S line is ON and the connection between the R line and the S line is conductive, it is assumed that the standard voltage waveform continues with the same phase and amplitude. A method for measuring power.

The method according to claim 1 or 2, wherein the load comprises a plurality of single-phase heaters.

In a three-phase three-wire type three-phase AC cable consisting of R, S, and T lines, each is connected independently between R line and S line, between S line and T line, and between T line and R line. A power measuring device for measuring the power of a load comprising a plurality of resistors that are turned ON / OFF,
The power measuring device includes current sensors provided for each of an R line and an S line, and measures the power of the load by the method according to claim 1.