JP2015078872A - Current measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current measuring device capable of correctly measuring a current to be measured by correcting a current detection value of a current sensor in consideration of the influence of a magnetic field by the current flowing through a current line in the vicinity.SOLUTION: A current measuring device for measuring an AC current of each of the three phases includes: a current sensor such as a GMR element for detecting each of currents flowing through three phase current lines 10 U, 10 V, and 10 W; and current calculation means 300 for calculating an AC current of each of the three phases by correcting a current detection value by a current sensor using parameters a to i showing an influence given to a current detection value by a magnetic field generated by the current of each phase. In this manner, true three phase AC currents i, i, and iwhich flow through the current lines 10 U, 10 V,and 10 W are correctly measured.

Description

  The present invention relates to a current measuring apparatus that measures an alternating current of each of three phases using a magnetoresistive element such as a GMR (Giant Magneto Resistance) element.

A current measuring apparatus using a GMR element as a current sensor obtains the magnitude of the current to be measured by utilizing the fact that the electrical resistance of the GMR element changes due to the magnetic field generated by the current to be measured.
This GMR element is advantageous in that it enables downsizing of a current sensor and can detect an alternating current and a direct current with high sensitivity, and is widely used, for example, in a three-phase alternating current measuring device.

However, when another current flows adjacent to the current line through which the measured current flows, a kind of disturbance magnetic field generated by this current affects the GMR element for detecting the measured current, and the measured current is accurately May not be detected.
In order to prevent a decrease in measurement accuracy due to the influence of such a disturbance magnetic field, conventionally, other adjacent current lines are arranged away from the GMR element, the physical shape and structure of the current lines are devised, or GMR Measures such as applying a magnetic shield to the element are taken. However, these measures cause an increase in the size of the current measuring device, impairing the downsizing that is a feature of the GMR element, and there is a problem that the cost increases when a magnetic shield is used.

In order to solve these problems, for example, a current measuring device shown in Patent Document 1 is provided.
4A and 4B are explanatory diagrams of the prior art described in Patent Document 1. FIG. 4A is an overall configuration diagram, FIG. 4B is a configuration diagram of a current sensor, and FIG. 4C is a block diagram of a measurement circuit.
As shown in FIGS. 4A and 4B, the shunt flow paths 205 a and 205 c are drawn from the current line 100 through which the current to be measured i flows, and close to the spiral shunt flow path 205 b formed in the current sensor 200. First and second GMR elements 201 and 202 are arranged. Reference numerals 201a and 202a denote sensitivity axes of the GMR elements 201 and 202, and reference numerals 203 and 204 denote terminals of the shunt flow path 205b.
As shown in FIG. 4C, the output signals of the GMR elements 201 and 202 are input to the arithmetic unit 300, and the difference between them is obtained.

In FIG. 4A, when a current i ₁ shunted from the current i to be measured flows through the shunt flow path 205b, a magnetic field H is generated in the direction of the arrow in FIG. 4B, and the GMR elements 201 and 202 are driven by the magnetic field H. Output signals (target current detection signals) are out of phase with each other. On the other hand, when a magnetic field due to a current flowing through another current line adjacent to the current line 100 acts on the GMR elements 201 and 202, the output signals (noise components) of the GMR elements 201 and 202 due to the disturbance magnetic field are in phase with each other.
Therefore, if the difference between the output signals of the GMR elements 201 and 202 is calculated by the arithmetic device 300, the noise component due to the disturbance magnetic field is canceled and only the target current measurement signal can be obtained.

Further, Patent Document 2 discloses the prior art shown in FIGS.
5, reference numerals 401 to 404 denote magnetoresistive elements constituting the Wheatstone bridge. In FIG. 6, reference numeral 400 denotes a sensor chip on which the magnetoresistive elements 401 to 404 are mounted, reference numeral 405 denotes a variable resistor, and reference numeral 406 denotes a center of the sensor chip 400. The line, U _a is the output voltage, U _b is the operating voltage, and I _st is the control current.

  In this prior art, regions I and II are formed on both sides of a region III that is separated from the center line 406 of the sensor chip 400 by a distance a on the left and right sides. Are arranged in line-symmetric positions. A U-shaped current line (not shown) is arranged on the back side of the regions I and II, and the direction of the current to be measured flowing through the current line is reversed between the region I side and the region II side. .

In the above configuration, when the operating voltage U _b is applied to the Wheatstone bridge in a state where the current to be measured flows through the current lines on the back side of the regions I and II, the magnetic field due to the current to be measured causes the magnetoresistive elements 401, 404 and 402, 403. And an output voltage U _a proportional to the magnitude of the current to be measured is obtained. At this time, since the external magnetic field generated by adjacent current lines even when applied to the magneto-resistive element 401 and 404 and 402 and 403, these magnetic fields are to be canceled by the magnetic field generated by the control current I _st, the output voltage U _a Will not be affected.

Japanese Patent Laying-Open No. 2012-52912 (paragraphs [0018] to [0036], FIG. 1, FIG. 2, etc.) US Pat. No. 5,621,377 (column 3, line 14 to line 52, FIG. 1 to FIG. 3)

In the prior art described in Patent Document 1, it is necessary to arrange the GMR elements 201 and 202 close to each other in order to equalize the influence of the disturbance magnetic field on the GMR elements 201 and 202. It required a lot of labor and cost.
Further, in the prior art described in Patent Document 2, the magnetoresistive elements 401, 404 and 402, 403 must be accurately arranged in line-symmetric positions, which has great manufacturing effort and restrictions, and sensor. There was a problem that the chip 400 was enlarged.

  Therefore, the problem to be solved by the present invention is not a measure based on the element arrangement or physical structure, but by correcting the current detection value of the current sensor in consideration of the influence of the magnetic field due to the current flowing through the surrounding current lines. An object of the present invention is to provide a current measuring device capable of accurately measuring a current.

In order to solve the above problems, an invention according to claim 1 is a current measuring device for measuring a current of each phase of three phases.
Current detecting means for detecting currents flowing through at least two phase current lines of the three phases by means of magnetoresistive elements, and
By correcting the current detection value of at least two phases using a parameter indicating the influence of the magnetic field generated by the current of each phase on the current detection value by the magnetoresistive element, the current of each of the three phases is calculated by calculation. Current calculating means.

  According to a second aspect of the present invention, in the current measuring device according to the first aspect, the parameter is a value corresponding to an interval between three-phase current lines.

  According to a third aspect of the present invention, in the current measuring device according to the first or second aspect, currents of all three phases are detected by current detecting means respectively installed on the current lines of the three phases.

  According to a fourth aspect of the present invention, in the current measuring device according to the first or second aspect, the two-phase current is detected by the current detecting means respectively installed on the two-phase current line.

The invention according to claim 5 is the current measuring device according to claim 3, wherein the current calculation means calculates the currents i _U , i _V , i _W of each of the three phases according to the following formula: To do.
i _U = G _UU · i _Udet + G _UV · i _Vdet + G _UW · i _Wdet
i _V = G _VU · i _Udet + G _VV · i _Vdet + G _VW · i _Wdet
i _W = G _WU · i _Udet + G _WV · i _Vdet + G _WW · i _Wdet
It will be described later above _G UU _{~G WW.}

The invention according to claim 6 is the current measuring device according to claim 4, wherein the current calculation means calculates the currents i _U , i _V , i _W of each of the three phases according to the following formula: To do.
i _U = G _UU '· i _Udet + G _UW ' · i _Wdet
i _W = G _WU '· i _Udet + G _WW ' · i _Wdet
i _V = −i _U −i _W
The above G _UU ', G _UW ', G _WU ', and G _WW ' will be described later.

The invention according to claim 7 is the current measuring device according to claim 5,
The three-phase current lines are arranged in a plane, and the distance between the V-phase current line and the U-phase current line and the distance between the V-phase current line and the W-phase current line are equal, When the characteristics of the current sensors are all equal, as will be described later, the current calculation means sets the parameters for obtaining the G _{UU to} G _WW as a = e = i, c = g, b = d = f = h. It is characterized by calculating.

The invention according to claim 8 is the current measuring device according to claim 6,
The three-phase current lines are arranged in a plane, and the distance between the V-phase current line and the U-phase current line and the distance between the V-phase current line and the W-phase current line are equal, When the characteristics of the current sensors are all equal, as will be described later, the current calculation means sets parameters for obtaining the G _UU ', G _UW ', G _WU ', and G _WW ' as a = i, b = h, It is calculated as c = g.
The invention according to claim 9 is the current measuring device according to claim 6,
Three-phase current lines are arranged in a plane, and the distance between the W-phase current line and the U-phase current line and the distance between the W-phase current line and the V-phase current line are equal, When the characteristics of the current detection means are all equal, the current calculation means uses parameters a = i, c = h for obtaining G _UU ', G _UW ', G _WU ', G _WW ' as will be described later. It is calculated as = g

In addition, as described in claim 10, in the current measuring device according to claim 5, the three-phase current lines are three-dimensionally arranged at equal intervals, and the characteristics of the current detection means are all equal. Sometimes, as will be described later, the current calculation means calculates the parameters for obtaining G _{UU to} G _WW as a = e = i, b = c = d = f = g = h, It can be further simplified.
Similarly, as described in claim 11, in the current measuring device according to claim 6, the three-phase current lines are three-dimensionally arranged at equal intervals, and all the characteristics of each current detecting means are all When they are equal, as will be described later, the current calculation means calculates the parameters for obtaining the G _UU ', G _UW ', G _WU ', G _WW ' as a = i, b = c = g = h. As a result, the calculation can be further simplified.

  Further, as described in claim 12, it is desirable to use a GMR element for the magnetoresistive element.

According to the present invention, the current to be measured is corrected by correcting the current detection value by the current detection means for detecting the current to be measured using a parameter that takes into account the influence of the magnetic field due to the current flowing through the surrounding current lines. It can be measured accurately.
In addition, the correction calculation for obtaining the current to be measured only requires relatively simple four arithmetic operations, so that the burden on hardware and software is small.

It is a block diagram of the electric current detection means in 1st Embodiment of this invention. It is a block diagram of the electric current detection means in 2nd Embodiment of this invention. 1 is an overall configuration diagram of a current measurement device common to each embodiment of the present invention. It is explanatory drawing of the prior art described in patent document 1. FIG. It is a circuit diagram of the prior art described in patent document 2. It is a block diagram of the prior art described in patent document 2. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1. First Embodiment FIG. 1 is a configuration diagram of current detection means in a first embodiment of the present invention. In Figure 1, 10 U, 10V, 10 W is adjacent current lines to each other, the current _i U three-phase (U, V, _W-phase), i V, _{i W} flows.
Here, U, V, and W-phase currents to be measured (hereinafter simply referred to as U-phase current, V-phase current, and W-phase current) i _U , i _V , and i _W are used as current lines 10U, 10V, and 10W for the respective phases. _Will be described based on the current detection values i _Udet , i _Vdet , i _Wdet of the current sensors 20U, 20V, 20W each composed of a magnetoresistive element such as a GMR element. In this case, as described above, since the current detection values i _Udet , i _Vdet , i _Wdet of each phase are affected by the magnetic field due to the currents i _U , i _V , i _W of each phase, i _U = i _Udet , i _V = i _Vdet and i _W = i _Wdet are not _satisfied .

Now, as shown in Table 1, the influence of the magnetic field caused by the phase currents i _U , i _V , i _W on the U-phase current detection value i _Udet is expressed by parameters K _UU , K _UV , K _UW , and the V-phase current is also the same. The influence on the detected value i _Vdet is represented by parameters K _VU , K _VV , and K _VW , and the influence on the W-phase current detected value i _Wdet is also represented by parameters K _WU , K _WV , and K _WW .
For convenience, K _UU = a, K _UV = b, K _UW = c, K _VU = d, K _VV = e, K _VW = f, K _WU = g, K _WV = h, K _WW = i And

Here, when the current lines 10U, 10V, and 10W of the respective phases are arranged in this order on a plane and at equal intervals, the detected current values i _Udet , i _Vdet , i _Wdet and the actual phase currents i _U , i _V , Formulas 1 to 3 are established between i and _W.

However, if the characteristics of the current sensors 20U, 20V, and 20W are completely the same, the nine parameters K _{UU to} K _WW change according to the distance between each current line and each current sensor. K _VU = K _VW = K _UV = K _WV , K _WU = K _UW , K _VV = K _WW = K _UU , that is, d = f = b = h, c = g, e = i = a, Equation 1 ~ 3 can be further simplified. However, in the following, the phase currents i _U , i _V , and i _W are obtained based on Formulas 1 to 3 in consideration of variations in characteristics of the current sensors 20U, 20V, and 20W.

また、数式２にＫ_ＵＶを乗算して数式５を得る。

次に、数式４から数式５を減算して数式６を得る。

(1) First, the current detection value _{i UDET,} i _Vdet, how to measure the U-phase current _{i U} with _{i WDET} be described.
First, Equation 4 is obtained by multiplying Equation 1 by _KVV .

Also, Formula 5 is obtained by multiplying Formula 2 by K _UV .

Next, Equation 6 is obtained by subtracting Equation 5 from Equation 4.

また、数式３にＫ_ＶＶを乗算して数式８を得る。

次に、数式７から数式８を減算して数式９を得る。

Next, Equation 7 is obtained by multiplying Equation 2 by K _WV .

Also, Equation 8 is obtained by multiplying Equation 3 by _KVV .

Next, Equation 9 is obtained by subtracting Equation 8 from Equation 7.

また、数式９に（Ｋ_ＵＷＫ_ＶＶ−Ｋ_ＶＷＫ_ＵＶ）を乗算して数式１１を得る。

数式１０から数式１１を減算して数式１２を得る。

Expression 10 is obtained by multiplying Expression 6 by (K _WV K _VW −K _VV K _WW ).

Also, Formula 11 is obtained by multiplying Formula 9 by (K _UW K _VV −K _VW K _UV ).

Equation 12 is obtained by subtracting Equation 11 from Equation 10.

ここで、数式１３のｉ_Ｕを数式１４により定義する。

Expression 13 is obtained from Expression 12.

Here, i _U in Equation 13 is defined by Equation 14.

The above calculation and the above-described K _UU = a, K _UV = b, K _UW = c, K _VU = d, K _VV = e, K _VW = f, K _WU = g, K _WV = h, K _WW = 15, Formulas 15 to 17 are obtained.

Thus, _{G UU,} G UV was determined using Equation 15 to _{17, G UW} and the current detection value _{i UDET,} i _Vdet, the use and _{i WDET,} using Equation 14, it is possible to determine the true U-phase current _{i U} .

数式９に（Ｋ_ＵＵＫ_ＶＶ−Ｋ_ＶＵＫ_ＵＶ）を乗算して数式１９を得る。

数式１８から数式１９を減算して数式２０を得る。

数式２０を変形して数式２１を得る。

(2) Next, the current detection value _{i UDET,} i _Vdet, the method of measuring the W-phase current _{i W} with _{i WDET} be described.
First, Equation 18 is obtained by multiplying Equation 6 by (K _WV K _VU −K _VV K _WU ).

Expression 19 is obtained by multiplying Expression 9 by (K _{UUK VV−} K _VU K _UV ).

Equation 19 is subtracted from Equation 18 to obtain Equation 20.

Equation 20 is transformed to obtain Equation 21.

Here, i _W of Equation 21 is defined by Equation 22.

The above calculation and the above-described K _UU = a, K _UV = b, K _UW = c, K _VU = d, K _VV = e, K _VW = f, K _WU = g, K _WV = h, K _WW = 23, Formulas 23 to 25 are obtained.

Accordingly, the true W-phase current i _W can be obtained from Equation 22 by using G _WU , G _WV , G _WW obtained from Equations 23 to 25 and the current detection values i _Udet , i _Vdet , i _Wdet. .

次いで、数式２にＫ_ＵＷを乗算して数式２７を得る。

数式２６から数式２７を減算して数式２８を得る。

(3) Further, the current detection value _{i UDET,} i _Vdet, how to measure the V-phase current _{i V} with _{i WDET} be described.
First, Equation 26 is obtained by multiplying Equation 1 by K _VW .

Next, Equation 27 is obtained by multiplying Equation 2 by _KUW .

Equation 28 is subtracted from Equation 26 to obtain Equation 28.

また、数式３にＫ_ＶＷを乗算して数式３０を得る。

数式２９から数式３０を減算して数式３１を得る。

Next, Equation 2 is obtained by multiplying Equation 2 by _KWW .

Also, Equation 30 is obtained by multiplying Equation 3 by K _VW .

Equation 31 is obtained by subtracting Equation 30 from Equation 29.

数式３１に（Ｋ_ＵＵＫ_ＶＷ−Ｋ_ＶＵＫ_ＵＷ）を乗算して数式３３を得る。

数式３２から数式３３を減算して数式３４を得る。

Furthermore, Formula 28 is obtained by multiplying Formula 28 by (K _VU K _WW −K _WU K _VW ).

Obtaining a formula 33 by multiplying the _{(K UU K VW -K VU K} UW) in Equation 31.

Equation 34 is obtained by subtracting Equation 33 from Equation 32.

Expression 34 is transformed to obtain Expression 35. Further, the mathematical formula 35 is transformed to obtain the mathematical formula 36.

Here, i _V in Expression 36 is defined by Expression 37.

The above calculation and the above-described K _UU = a, K _UV = b, K _UW = c, K _VU = d, K _VV = e, K _VW = f, K _WU = g, K _WV = h, K _WW = 38, Formulas 38-40 are obtained.

Therefore, the true V-phase current i _V can be obtained from Equation 37 by using G _VU , G _VV , G _VW and current detection values i _Udet , i _Vdet , i _{Wdet obtained} by Equations _38-40. .

Here, _G UU formulas _{15~17, G UV, G UW,} G WU formulas _{23~25, G WV, G WW,} G VU formulas 38 to _40, G _VV, parameters for determining the _{G VW} a -I can be calculated | required by the method as shown below.
In other words, each phase of the current line 10 U, 10V, to 10 W, in passing only U-phase current _{i U,} in passing only V-phase current _{i V,} in passing only W-phase current _{i W,} respectively The current detection values by the current sensors 20U, 20V, and 20W of each phase are actually measured.

この表２は、Ｕ相電流ｉ_Ｕだけを流した場合のＵ相電流検出値ｉ_Ｕｄｅｔが９６［Ａ］、Ｖ相電流検出値ｉ_Ｖｄｅｔが２．８［Ａ］、Ｗ相電流検出値ｉ_Ｗｄｅｔが０．８［Ａ］であり、Ｖ相電流ｉ_Ｖだけを流した場合のＵ相電流検出値ｉ_Ｕｄｅｔが２．８［Ａ］、Ｖ相電流検出値ｉ_Ｖｄｅｔが９６［Ａ］、Ｗ相電流検出値ｉ_Ｗｄｅｔが２．８［Ａ］であり、Ｗ相電流ｉ_Ｗだけを流した場合のＵ相電流検出値ｉ_Ｕｄｅｔが０．８［Ａ］、Ｖ相電流検出値ｉ_Ｖｄｅｔが２．４［Ａ］、Ｗ相電流検出値ｉ_Ｗｄｅｔが９７［Ａ］であることを示している。
なお、Ｖ相電流検出値ｉ_Ｖｄｅｔの２．４［Ａ］、Ｗ相電流検出値ｉ_Ｗｄｅｔの９７［Ａ］は、電流検出時の誤差と考えられるので、これらの誤差がない場合を想定して、２．４［Ａ］→２．８［Ａ］，９７［Ａ］→９６［Ａ］と補正しても良い。 For example, when the amplitudes of the phase currents i _U , i _V , i _W are all 100 [A], the current detection values (actual values) i _Udet , i _Vdet , by the current sensors 20U, 20V, 20W of the respective phases _Assume that i _Wdet is as shown in Table 2.

The Table 2, U-phase current _{i U} U-phase current detection value _{i UDET} in passing only is 96 [A], V-phase current detection value _{i Vdet} is 2.8 [A], W-phase current detection value i _Wdet a is 0.8 [a], U-phase current detection value _{i UDET} in passing only V-phase current _{i V} is 2.8 [a], V-phase current detection value _{i Vdet} is 96 [a], The W-phase current detection value i _Wdet is 2.8 [A], the U-phase current detection value i _Udet is 0.8 [A] when only the W-phase current i _W is passed, and the V-phase current detection value i _Vdet. Is 2.4 [A], and the W-phase current detection value i _Wdet is 97 [A].
It should be _{noted that} 2.4 [A] of the V-phase current detection value i _Vdet and 97 [A] of the W-phase current detection value i _Wdet are considered errors at the time of current detection. Thus, the correction may be made as 2.4 [A] → 2.8 [A], 97 [A] → 96 [A].

In the following, processing is performed using the values in Table 2 as they are. First, _assuming that the parameters indicating the respective phase current detection values i _Udet , i _Vdet , i _Wdet in Table 2 as a percentage are a to i, a = 96 [%], b = 2.8 [%], c = 0. 8 [%], ... This is to U-phase current _{i U,} the 96 [%] is detected by the U-phase current sensor 20 U, due to the influence of the magnetic flux generated by the U-phase current _{i U,} 2.8 [%] is the V-phase current It is detected by the sensor 20V, and 0.8 [%] is detected by the W-phase current sensor 20W.

Here, the parameters a to i are values that reflect the effect of the current for one phase, and a three-phase alternating current flows through the actual current lines 10U, 10V, and 10W. _Udet is simultaneously influenced by the phase currents i _U , i _V , i _W , and this is the same for the V-phase current detection value i _Vdet and the W-phase current detection value i _Wdet .
Therefore, when the influence of each phase current i _U , i _V , i _W is considered, each phase current detection value i _Udet , i _Vdet , when a current having an amplitude of 100 [A] flows through the current line 10U, i _Measure the amplitude of _Wdet to determine a, d, and g. Similarly, the amplitude of each phase current detection value i _Udet , i _Vdet , i _Wdet when a current having an amplitude of 100 [A] flows through the current line 10 V is measured to obtain b, e, h. Further, c, f, i are obtained by measuring the amplitude of each phase current detection value i _Udet , i _Vdet , i _Wdet when a current having an amplitude of 100 [A] flows through the current line 10W.

If the parameters a to i are obtained as described above, G _UU , G _UV , G _{UW of} Expressions 15 to 17, G _WU , G _WV , G _{WW of} Expressions 23 to 25, G _{VU of} Expressions 38 to 40, G _VV and G _VW are determined, and the phase currents i _U , i _V , and i _W can be obtained by calculation.
Here, the parameters a to i in Table 2 are used as they are, and the equation 41 is obtained from these parameters a to i and Equations 14, 22, and 37.

Using this equation 41, the current detection values i _Udet , i _Vdet , i _Wdet by the phase current sensors 20U, 20V, 20W are corrected, and the actual phase currents i _U , i _V , i _W are accurately measured. be able to.

2. Second Embodiment Next, FIG. 2 is a configuration diagram of current detection means in a second embodiment of the present invention, and the same components as those in FIG. 1 are denoted by the same reference numerals.
In this second embodiment, the phase currents _{i U,} i V, and _{i W,} U-phase, W-phase current lines 10 U, the current sensor 20U consisting magnetoresistive element such as GMR elements disposed respectively 10 W, 20W The current detection values i _Udet and i _Wdet are obtained.

As in the first embodiment, parameters K _UU (= a), K _UV (= b), and K _UW are the effects of the magnetic fields generated by the phase currents i _U , i _V , i _W on the U-phase current detection value i _Udet. It is expressed by (= c), and the influence on the W-phase current detection value i _Wdet is also expressed by parameters K _WU (= g), K _WV (= h), and K _WW (= i).
These relationships are shown in Table 3.

When the current lines 10U, 10V, and 10W of each phase are arranged in this order in a planar and equidistant manner, the current detection values i _Udet and i _{Wdet are} between the actual phase currents i _U , i _V , and i _W. The following formulas 42 and 43 hold. _{Incidentally, i U + i V + i} W = 0 (i V = -i U -i W) to the condition.

However, current sensor 20 U, if the characteristics of 20W are completely identical, because the six parameters K _UU ~K _WW, which changes according to the distance between each current line and the current sensors, K _WU = K _UW , K _WV = K _UV , K _WW = K _UU , that is, g = c, h = b, i = a, and the expressions 42 and 43 can be further simplified. However, hereinafter, the phase currents i _U , i _V , and i _W are obtained based on the equations 42 and 43 in consideration of variations in characteristics of the current sensors 20U and 20W.

また、数式４３に（Ｋ_ＵＷ−Ｋ_ＵＶ）を乗算して数式４５を得る。

(1) First, a method for measuring the U-phase current _{i U} using current detection value _{i UDET,} the _{i WDET.}
First, Formula 44 is obtained by multiplying Formula 42 by (K _WW −K _WV ).

Also, Formula 45 is obtained by multiplying Formula 43 by (K _UW −K _UV ).

Next, Equation 45 is subtracted from Equation 44 to obtain Equation 46. Further, the mathematical formula 46 is transformed to obtain the mathematical formula 47.

従って、数式４８〜５０により、電流検出値ｉ_Ｕｄｅｔ，ｉ_Ｗｄｅｔ及びＧ_ＵＵ’，Ｇ_ＵＷ’を用いれば、真のＵ相電流ｉ_Ｕを求めることができる。 Here, the U-phase current i _U is defined by Equation 48. Note that G _UU ′ and G _UW ′ in Formula 48 are as shown in Formulas 49 and 50, and are different from G _UU and G _UW in Formulas 14, 15, and 17.
Further, in Equations 49 and 50, a = K _UU , b = K _UV , c = K _UW , g = K _WU , h = K _WV , i = K _WW .

Therefore, the true U-phase current i _U can be obtained by using the current detection values i _Udet , i _Wdet and G _UU ', G _UW ' according to the mathematical expressions 48 to 50.

また、数式４３に（Ｋ_ＵＵ−Ｋ_ＵＶ）を乗算して数式５２を得る。

(2) Next, the current detection value _{i UDET,} the method of measuring the W-phase current _{i W} with _{i WDET} be described.
First, Formula 51 is obtained by multiplying Formula 42 by (K _WU −K _WV ).

Further, Formula 52 is obtained by multiplying Formula 43 by (K _UU −K _UV ).

The formula 53 is obtained by subtracting the formula 52 from the formula 51. Further, the mathematical formula 53 is transformed to obtain the mathematical formula 54.

従って、数式５５〜５７により、電流検出値ｉ_Ｕｄｅｔ，ｉ_Ｗｄｅｔ及びＧ_ＷＵ’，Ｇ_ＷＷ’を用いれば、真のＷ相電流ｉ_Ｗを求めることができる。 Here, the measured current i _W of the W phase is defined by Equation 55. Incidentally, _{G WU} in Equation 55 _{', G WW'} is shown in Equation 56 and 57.

Therefore, the true W-phase current i _W can be obtained by using the current detection values i _Udet and i _Wdet and G _WU ′ and G _WW ′ according to the equations 55 to 57.

A = K _UU , b = K _UV , c = K _UW , g = K _WU , h for obtaining G _UU ′, G _UW ′ of Formulas 49 and 50 and G _WU ′ and G _WW ′ of Formulas 56 and 57 _{= K} WV, i = _{K WW} can be determined by actual measurement as in the first embodiment. That is, according to Table 2 described above, the U-phase current detection value i _Udet is 96 [A] and the W-phase current detection value i _Wdet is 0.8 [A] when only the U-phase current i _U is passed. , U-phase current detection value _{i UDET} 2.8 in passing only V-phase current _{i V} [a], W-phase current detection value _{i WDET} is 2.8 [a], W-phase current _{i W} only The U-phase current detection value i _Udet is 0.8 [A] and the W-phase current detection value i _Wdet is 97 [A], so that a = 96 [%] and b = 2.8 [%]. ], C = 0.8 [%], g = 0.8 [%], h = 2.8 [%], i = 97 [%].
From these parameters a, b, c, g, h, i, G _UU ′, G _UW ′ of Formulas 49, 50 and G _WU ′, G _WW ′ of Formulas 56, 57 can be obtained. Using Equation 55, the U-phase current i _U and the W-phase current i _W can be obtained by Equation 58.

(3) Further, the V-phase current i _V can be calculated by Equation 59 as described above.
[Numerical formula 59]
i _V = −i _U −i _W

Therefore, it is possible to correct the current detection values i _Udet and i _Wdet by the U-phase current sensor 20U and the W-phase current sensor 20W and accurately measure the actual phase currents i _U , i _V and i _W. .
In the second embodiment, the example in which the current sensors 20U and 20W are respectively installed on the U-phase and W-phase current lines 10U and 10W has been described. However, for example, a current is supplied to the U-phase and V-phase current lines 10U and 10V. Needless to say, the present invention can also be applied to the case where each sensor is installed.

Next, FIG. 3 is an overall configuration diagram of a current measuring device common to the first and second embodiments described above.
In FIG. 3, reference numeral 200 denotes current detection means comprising the current sensors 20U, 20V, 20W of the first embodiment or the current sensors 20U, 20W of the second embodiment, and 300 denotes a current detection value by the current sensors 20U, 20V, 20W. Each phase current i _U , i _V , i _W is calculated from i _Udet , i _Vdet , i _Wdet and parameters a to i, or current detection values i _Udet , i _Wdet and parameters a, b by current sensors 20U, 20W are calculated. , C, g, h, i, current calculation means such as a CPU for calculating each phase current i _U , i _V , i _W.
If the parameters a to i or a, b, c, g, h, i are known, the actual phase currents i _U , i _V , i _W can be accurately obtained only by simple four arithmetic operations by the current calculating means 300. And the burden of hardware and software is small.

In the above-described embodiment, the case where the current lines 10U, 10V, and 10W of each phase are arranged planarly and at equal intervals has been described. However, the current lines 10U, 10V, and 10W of each phase are arranged at equal intervals in three dimensions. (The cross sections of the current lines 10U, 10V, and 10W in the longitudinal direction are equilateral triangles, and the current lines 10U, 10V, and 10W are arranged at the respective apexes), and the characteristics of the phase current sensors are the same. For example, K _VU = K _WU , K _UV = K _WV , K _UW = K _WU , K _UU = K _VV = K _WW in Table 1 can be set, and the phase currents i _U , i _V , i The calculation formula of _W can be further simplified.

10U, 10V, 10W: current lines 20U, 20V, 20W: current sensor 200: current detection means 300: current calculation means

Claims (12)

In the current measurement device that measures the current of each of the three phases,
Current detecting means for detecting currents flowing through at least two phase current lines of the three phases by means of magnetoresistive elements, and
By correcting the current detection value of at least two phases using a parameter indicating the influence of the magnetic field generated by the current of each phase on the current detection value by the magnetoresistive element, the current of each of the three phases is calculated by calculation. Current calculation means;
A current measuring device comprising: The current measuring device according to claim 1,
The said parameter is a value according to the space | interval of the three-phase current line, The current measurement detection apparatus characterized by the above-mentioned. In the current measuring device according to claim 1 or 2,
A current measuring device that detects currents of all three phases by the current detecting means respectively installed on the current lines of the three phases. In the current measuring device according to claim 1 or 2,
A current measuring device for detecting a two-phase current by means of the current detection means respectively installed on a two-phase current line. In the current measuring device according to claim 3,
The current calculation means calculates the currents i _U , i _V , i _W of each of the three phases according to the following mathematical formula.
i _U = G _UU · i _Udet + G _UV · i _Vdet + G _UW · i _Wdet
i _V = G _VU · i _Udet + G _VV · i _Vdet + G _VW · i _Wdet
i _W = G _WU · i _Udet + G _WV · i _Vdet + G _WW · i _Wdet
(Note that
G _UU = (hf-ei) e / {(hf-ei) (ae-db)-(hd-eg) (ce-fb)},
G _UV = {(ei−hf) b + (fb−ce) h} / {(hf−ei) (ae−db) − (hd−eg) (ce−fb)},
G _UW = (ce−fb) e / {(hf−ei) (ae−db) − (hd−eg) (ce−fb)},
G _VU = f (di−gf) / {(di−gf) (bf−ec) − (ei−hf) (af−dc)},
G _VV = {c (gf−di) + i (dc−af)} / {(di−gf) (bf−ec) − (ei−hf) (af−dc)},
G _VW = f (af−dc) / {(di−gf) (bf−ec) − (ei−hf) (af−dc)},
G _WU = (hd-eg) e / {(hd-eg) (ce-fb)-(ae-db) (hf-ei)},
G _WV = {(eg−hd) b + (db−ae) h} / {(hd−eg) (ce−fb) − (ae−db) (hf−ei)},
G _WW = (ae-db) e / {(hd-eg) (ce-fb)-(ae-db) (hf-ei)}
And
a: a parameter indicating the influence of the U-phase current on the U-phase current detection value;
b: a parameter indicating the influence of the V-phase current on the U-phase current detection value,
c: a parameter indicating the influence of the W-phase current on the U-phase current detection value;
d: a parameter indicating the influence of the U-phase current on the V-phase current detection value;
e: a parameter indicating the influence of the V-phase current on the V-phase current detection value;
f: a parameter indicating the influence of the W-phase current on the V-phase current detection value,
g: a parameter indicating the influence of the U-phase current on the W-phase current detection value,
h: a parameter indicating the influence of the V-phase current on the W-phase current detection value,
i: a parameter indicating the influence of the W-phase current on the W-phase current detection value;
i _Udet : U-phase current detection value, i _Vdet : V-phase current detection value, i _Wdet : W-phase current detection value, and the parameters a to i are currents with known amplitudes to any one current line Value obtained from the current detection value of each current detection means) In the current measuring device according to claim 4,
The current calculation means calculates the currents i _U , i _V , i _W of each phase of the three phases according to the following mathematical formula.
i _U = G _UU '· i _Udet + G _UW ' · i _Wdet
i _W = G _WU '· i _Udet + G _WW ' · i _Wdet
i _V = −i _U −i _W
(Note that
G _UU ′ = (i−h) / {(i−h) (ab) − (gh) (c−b)},
G _UW ′ = − (c−b) / {(i−h) (a−b) − (g−h) (c−b)},
G _WU ′ = (g−h) / {(g−h) (c−b) − (i−h) (a−b)},
_GWW '=-(ab) / {(gh) (cb)-(ih) (ab)}
And
a: a parameter indicating the influence of the U-phase current on the U-phase current detection value;
b: a parameter indicating the influence of the V-phase current on the U-phase current detection value,
c: a parameter indicating the influence of the W-phase current on the U-phase current detection value;
g: a parameter indicating the influence of the U-phase current on the W-phase current detection value,
h: a parameter indicating the influence of the V-phase current on the W-phase current detection value,
i: a parameter indicating the influence of the W-phase current on the W-phase current detection value;
i _Udet : U-phase current detection value, i _Wdet : W-phase current detection value,
The parameters a, b, c, g, h, i are values obtained from the current detection values of the respective current detection means when a current having a known amplitude is passed through any one of the current lines) The current measuring device according to claim 5,
The three-phase current lines are arranged in a plane, and the distance between the V-phase current line and the U-phase current line and the distance between the V-phase current line and the W-phase current line are equal, When the characteristics of the current detection means are all equal,
The current calculation means includes
The current measuring device is characterized by calculating with the parameters a = e = i, c = g, b = d = f = h. The current measuring device according to claim 6,
The three-phase current lines are arranged in a plane, and the distance between the V-phase current line and the U-phase current line and the distance between the V-phase current line and the W-phase current line are equal, When the characteristics of the current detection means are all equal,
The current calculation means includes
The current measuring device is calculated as the parameters a = i, b = h, c = g. The current measuring device according to claim 6,
Three-phase current lines are arranged in a plane, and the distance between the W-phase current line and the U-phase current line and the distance between the W-phase current line and the V-phase current line are equal, When the characteristics of the current detection means are all equal,
The current calculation means includes
The current measuring device is calculated with the parameters a = i and c = h = g. The current measuring device according to claim 5,
When the three-phase current lines are three-dimensionally arranged at equal intervals from each other and the characteristics of each current detection means are all equal,
The current calculation means includes
A current measuring device, wherein the calculation is performed with the parameters a = e = i and b = c = d = f = g = h. The current measuring device according to claim 6,
When the three-phase current lines are three-dimensionally arranged at equal intervals from each other and the characteristics of each current detection means are all equal,
The current calculation means includes
The current measuring device is characterized by calculating with the parameters a = i and b = c = g = h. In the current measuring device according to any one of claims 1 to 11,
A current measuring apparatus, wherein the magnetoresistive element is a GMR element.

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