Electric current sensor

Abstract

Provided is an electric current sensor comprising: a first bus bar (10A), a second bus bar (10B), and a third bus bar (10C) through which a three-phase AC current flows; a first sensor unit (20A) having a first magnetic detection element (30A) and a second magnetic detection element (30B); and a second sensor unit (20B) having a third magnetic detection element (30C) and a fourth magnetic detection element (30D), the first sensor unit (20A) being disposed between two bus bars other than one arbitrary bus bar to be measured from among the first through third bus bars, the second sensor unit (20B) having as a measurement object one of the two bus bars other than the one bus bar to be measured, and being disposed between the one bus bar to be measured and the other of the two bus bars other than the one bus bar to be measured, the distance between the first magnetic detection element (30A) and the one of the two bus bars other than the one bus bar to be measured and the distance between the second magnetic detection element (30B) and the other of the two bus bars other than the one bus bar to be measured being substantially equal, and the distance between the third magnetic detection element (30C) and the other of the two bus bars other than the one bus bar to be measured and the distance between the fourth magnetic detection element (30D) and the one bus bar to be measured being substantially equal.

Description

Current Sensor

[0001] The present invention relates to a current sensor.

[0002] Japanese Patent Laid-Open Publication No. 2008-58035 (Patent Document 1) is a prior art document disclosing the configuration of a current measuring device. The current measuring device described in Patent Document 1 measures the current values ​​of each of three conductors through which currents whose sum total is zero flow. The current measuring device includes first and second coreless current sensors, a holding means, a calculating means, and a shielding member. The first and second coreless current sensors are positioned at predetermined relative positions with respect to the three conductors. The holding means acquires and stores coefficients necessary for measuring the currents flowing through the three conductors in a preparation stage prior to measuring the currents. The calculating means utilizes the fact that the sum total of the currents flowing through the three conductors is zero to calculate the current values ​​flowing through each conductor based on the output signals of the first and second coreless current sensors and the coefficients stored in the holding means. A shielding member surrounds each conductor and the first and second coreless current sensors.

[0003] Japanese Patent Application Laid-Open No. 2008-58035

[0004] The current measurement device described in Patent Document 1 requires a shielding member, which increases the device's size and reduces the accuracy of current measurement. Furthermore, the device calculates the current value of each conductor based on previously acquired parameters, which requires complex calculations. This lengthens the time required to calculate the current value, resulting in reduced current measurement responsiveness.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide a current sensor that can improve measurement accuracy and responsiveness while reducing the overall size.

[0006] A current sensor according to the present invention includes a first bus bar, a second bus bar, and a third bus bar, a first sensor unit, a second sensor unit, and a calculation unit. The first bus bar, the second bus bar, and the third bus bar extend in a first direction while being spaced apart from one another and are aligned in a second direction perpendicular to the first direction, through which a three-phase AC current flows. The first sensor unit is disposed between two bus bars other than any one of the first bus bar, the second bus bar, and the third bus bar. The second sensor unit measures one of the two bus bars other than the one bus bar and is disposed between the one bus bar and the other of the two bus bars other than the one bus bar. The calculation unit calculates a current value of each of the first bus bar, the second bus bar, and the third bus bar from output values ​​of the first sensor unit and the second sensor unit. The first sensor unit includes a first magnetic detection element and a second magnetic detection element. The first and second magnetic detection elements each have a sensitivity axis facing a third direction perpendicular to the first and second directions, are aligned in the second direction, and detect magnetic fields generated by currents flowing through the first, second, and third bus bars. The second sensor unit includes a third and fourth magnetic detection element. The third and fourth magnetic detection elements each have a sensitivity axis facing the third direction, are aligned in the second direction, and detect magnetic fields generated by currents flowing through the first, second, and third bus bars. When viewed from the first direction, the distance between the first magnetic detection element and one of the two bus bars other than the bus bar to be measured and the distance between the second magnetic detection element and the other of the two bus bars other than the bus bar to be measured are approximately equidistant. When viewed from the first direction, the distance between the third magnetic detection element and the other of the two bus bars other than the bus bar to be measured, and the distance between the fourth magnetic detection element and the bus bar to be measured are approximately equal.The calculation unit is capable of calculating the value of a current flowing through a bus bar to be measured based on the differential output value between the measurement value of the first magnetic detection element and the measurement value of the second magnetic detection element in the first sensor unit, and is capable of calculating the value of a current flowing through one of two bus bars other than the bus bar to be measured based on the differential output value between the measurement value of the third magnetic detection element and the measurement value of the fourth magnetic detection element in the second sensor unit, and is capable of calculating the value of a current flowing through the other of the two bus bars other than the bus bar to be measured by adding the value of a current flowing through the bus bar to the value of a current flowing through one of the two bus bars other than the bus bar to be measured.

[0007] According to the present invention, it is possible to reduce the overall size of the current sensor while improving the measurement accuracy and responsiveness.

[0008] FIG. 1 is a perspective view showing a configuration of a current sensor according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a configuration of a current sensor according to a first embodiment of the present invention. FIG. 3 is a block diagram showing electrical connections of each component in the current sensor according to the first embodiment of the present invention. FIG. 4 is a cross-sectional view showing a state in which a magnetic field generated from each bus bar in the current sensor according to the first embodiment of the present invention is detected by a first magnetic detection element of a first sensor unit. FIG. 5 is a cross-sectional view showing a state in which a magnetic field generated from each bus bar in the current sensor according to the first embodiment of the present invention is detected by a second magnetic detection element of the first sensor unit. FIG. 6 is a circuit diagram schematically showing a circuit configuration of the current sensor according to the first embodiment of the present invention. FIG. 7 is a cross-sectional view showing a configuration of a current sensor according to a second embodiment of the present invention.

[0009] Hereinafter, current sensors according to embodiments of the present invention will be described with reference to the drawings. In the following description of the embodiments, the same or corresponding parts in the drawings will be given the same reference numerals, and description thereof will not be repeated.

[0010] In the drawings, the direction in which the bus bars are lined up is the X direction as the second direction, the direction in which the bus bars extend is the Y direction as the first direction, and the direction along the sensitivity axis of each magnetic detection element is the Z direction as the third direction. Furthermore, the distance between each component in the current sensor is the distance connecting the centers of the components.

[0011] (Embodiment 1) Fig. 1 is a perspective view showing the configuration of a current sensor according to embodiment 1 of the present invention. Fig. 2 is a cross-sectional view showing the configuration of the current sensor according to embodiment 1 of the present invention. Fig. 3 is a block diagram showing the electrical connections of the components in the current sensor according to embodiment 1 of the present invention.

[0012] As shown in Figures 1 to 3, the current sensor 1 according to the first embodiment of the present invention includes a first bus bar 10A, a second bus bar 10B, a third bus bar 10C, a first sensor unit 20A, a second sensor unit 20B, and a calculation unit 40.

[0013] The first bus bar 10A, the second bus bar 10B, and the third bus bar 10C are three-phase, three-wire bus bars. Three-phase AC current flows through each of the first bus bar 10A, the second bus bar 10B, and the third bus bar 10C. The currents flowing through the first bus bar 10A, the second bus bar 10B, and the third bus bar 10C are AC currents of equal amplitude and phase shifted by 120° from each other.

[0014] The current value (I) of the first current flowing through the first bus bar 10A in the first direction (Y direction) １ ), the current value (I ２ ), and the current value (I ３ ) In １ +I ２ +I ３ = 0. For example, the first current may be a U-phase AC current, the second current may be a V-phase AC current, and the third current may be a W-phase AC current.

[0015] The first bus bar 10A, the second bus bar 10B, and the third bus bar 10C are arranged at intervals in a second direction (X direction) perpendicular to the first direction (Y direction). In this embodiment, the third bus bar 10C is arranged such that the distance between the third bus bar 10C and the second bus bar 10B in the second direction (X direction) is equal to the distance between the first bus bar 10A and the second bus bar 10B. Note that the distance between the first bus bar 10A and the second bus bar 10B and the distance between the second bus bar 10B and the third bus bar 10C in the second direction (X direction) may be different.

[0016] The first bus bar 10A extends linearly along a first direction (Y direction). The current value (I １ ) is an alternating current and can therefore take on positive or negative values.

[0017] The second bus bar 10B extends linearly along the first direction (Y direction). The current value (I ２ ) is an alternating current and can therefore take on positive or negative values.

[0018] The third bus bar 10C extends linearly along the first direction (Y direction). The current value (I ３ ) is an alternating current and can therefore take on positive or negative values.

[0019] The first sensor unit 20A is disposed between any two bus bars other than one of the first bus bar 10A, the second bus bar 10B, and the third bus bar 10C that is the measurement target. In this embodiment, the first sensor unit 20A measures the third bus bar 10C as the one measurement target bus bar. Therefore, the first sensor unit 20A is disposed between the first bus bar 10A and the second bus bar 10B. The first sensor unit 20A is disposed, for example, on a substrate (not shown). The position of the first sensor unit 20A may be fixed by a resin mold or the like.

[0020] The first sensor unit 20A includes a first magnetic detection element 30A and a second magnetic detection element 30B. Each of the first magnetic detection element 30A and the second magnetic detection element 30B can detect a magnetic field generated by a current flowing through the first bus bar 10A, the second bus bar 10B, and the third bus bar 10C.

[0021] The first magnetic detection element 30A and the second magnetic detection element 30B each have a sensitivity axis oriented in a third direction (Z direction) perpendicular to the first direction (Y direction) and the second direction (X direction). Specifically, the first magnetic detection element 30A has a first sensitivity axis A1 oriented in the third direction (Z direction). The second magnetic detection element 30B has a second sensitivity axis A2 oriented in the third direction (Z direction).

[0022] The first magnetic detection element 30A and the second magnetic detection element 30B are aligned in the second direction (X direction). In this embodiment, the first magnetic detection element 30A and the second magnetic detection element 30B are aligned in the second direction (X direction) with their positions in the third direction (Z direction) being approximately the same.

[0023] The second sensor unit 20B measures one of the two bus bars other than the one bus bar to be measured. In the present embodiment, the second sensor unit 20B measures the first bus bar 10A as one of the two bus bars other than the one bus bar to be measured.

[0024] The second sensor unit 20B is disposed between the bus bar to be measured and the other of the two bus bars other than the one to be measured. In this embodiment, the second sensor unit 20B is disposed between the third bus bar 10C and the second bus bar 10B, which is the other of the two bus bars other than the one to be measured. The second sensor unit 20B is disposed, for example, on a substrate (not shown). The position of the second sensor unit 20B may be fixed by a resin mold or the like.

[0025] The second sensor unit 20B includes a third magnetic detection element 30C and a fourth magnetic detection element 30D. Each of the third magnetic detection element 30C and the fourth magnetic detection element 30D can detect a magnetic field generated by a current flowing through the first bus bar 10A, the second bus bar 10B, and the third bus bar 10C.

[0026] The third magnetic detection element 30C and the fourth magnetic detection element 30D each have a sensitivity axis oriented in the third direction (Z direction). Specifically, the third magnetic detection element 30C has a third sensitivity axis A3 oriented in the third direction (Z direction). The fourth magnetic detection element 30D has a fourth sensitivity axis A4 oriented in the third direction (Z direction).

[0027] The third magnetic detection element 30C and the fourth magnetic detection element 30D are aligned in the second direction (X direction). In this embodiment, the third magnetic detection element 30C and the fourth magnetic detection element 30D are aligned in the second direction (X direction) at approximately the same position in the third direction (Z direction).

[0028] At least one of the first magnetic detection element 30A, the second magnetic detection element 30B, the third magnetic detection element 30C, and the fourth magnetic detection element 30D in the first sensor unit 20A and the second sensor unit 20B may have a circuit including at least two or more magnetoresistive elements. Each of the first magnetic detection element 30A, the second magnetic detection element 30B, the third magnetic detection element 30C, and the fourth magnetic detection element 30D may have a circuit including at least two or more magnetoresistive elements. The circuit including at least two or more magnetoresistive elements may be a half-bridge circuit including two magnetoresistive elements or a Wheatstone bridge circuit including four magnetoresistive elements.

[0029] The magnetoresistive element may be any of a tunnel magnetoresistive (TMR) element, a giant magnetoresistive (GMR) element, and an anisotropic magnetic resistance (AMR) element.

[0030] At least one of the first magnetic detection element 30A, the second magnetic detection element 30B, and the third magnetic detection element 30C may include a Hall element. Any of the first magnetic detection element 30A, the second magnetic detection element 30B, the third magnetic detection element 30C, and the fourth magnetic detection element 30D may include a Hall element.

[0031] Each of the first bus bar 10A, the second bus bar 10B, the third bus bar 10C, the first sensor unit 20A and the second sensor unit 20B is arranged on an imaginary plane F along the first direction (Y direction) and the second direction (X direction).

[0032] The calculation unit 40 calculates the current values ​​of the first bus bar 10A, the second bus bar 10B, and the third bus bar 10C from the output values ​​of the first sensor unit 20A and the second sensor unit 20B.

[0033] 3 , the first sensor unit 20A and the second sensor unit 20B are each electrically connected to the calculation unit 40 by wiring. Specifically, the first magnetic detection element 30A, the second magnetic detection element 30B, the third magnetic detection element 30C, and the fourth magnetic detection element 30D are each electrically connected to the calculation unit 40.

[0034] The positional relationship between each bus bar and each magnetic detection element in each sensor unit will be described below.

[0035] 2, when viewed from the first direction (Y direction), the distance a between the first magnetic detection element 30A and the first bus bar 10A (one of the two bus bars other than the bus bar to be measured) and the distance a between the second magnetic detection element 30B and the second bus bar 10B (the other of the two bus bars other than the bus bar to be measured) are approximately equidistant. Note that the term "approximately equidistant" in this embodiment refers to the distances, and includes variations in the assembly positions of the components of the current sensor during the manufacturing process.

[0036] When viewed from the first direction (Y direction), the distance b between the first magnetic detection element 30A and the second bus bar 10B (the other of the two bus bars other than the bus bar to be measured) and the distance b between the second magnetic detection element 30B and the first bus bar 10A (one of the two bus bars other than the bus bar to be measured) are approximately equal.

[0037] Since distance b is the distance a plus the distance between the first magnetic detection element 30A and the second magnetic detection element 30B, if the distance a between the first magnetic detection element 30A and the first bus bar 10A and the distance a between the second magnetic detection element 30B and the second bus bar 10B are approximately equal, then the distance b between the first magnetic detection element 30A and the second bus bar 10B and the distance b between the second magnetic detection element 30B and the first bus bar 10A will necessarily be approximately equal.

[0038] When viewed from the first direction (Y direction), the first magnetic detection element 30A and the third bus bar 10C (one bus bar to be measured) are disposed at a distance c1, and when viewed from the first direction (Y direction), the second magnetic detection element 30B and the third bus bar 10C (one bus bar to be measured) are disposed at a distance c2.

[0039] With regard to the third magnetic detection element 30C and the fourth magnetic detection element 30D, when viewed from the first direction (Y direction), the distance between the third magnetic detection element 30C and the second bus bar 10B (the other of the two bus bars other than the bus bar to be measured) and the distance between the fourth magnetic detection element 30D and the third bus bar 10C (the bus bar to be measured) are approximately equal.

[0040] When viewed from the first direction (Y direction), the distance between the third magnetic detection element 30C and the third bus bar 10C (the bus bar to be measured) and the distance between the fourth magnetic detection element 30D and the second bus bar 10B (the other of the two bus bars other than the bus bar to be measured) are approximately equal.

[0041] When viewed from the first direction (Y direction), the distances of the third magnetic detection element 30C and the fourth magnetic detection element 30D relative to the first bus bar 10A (one of the two bus bars other than the bus bar to be measured) are different from each other.

[0042] In this embodiment, no magnetic shielding plates made of a magnetic material with high magnetic permeability or magnetic cores made of a soft magnetic material for concentrating magnetic fields are provided between the bus bars and the sensor units, thereby enabling the current sensor 1 according to this embodiment to be reduced in overall size.

[0043] Hereinafter, it will be described that even when each sensor unit detects a magnetic field including a bus bar other than the bus bar to be measured, only the current value of the bus bar to be measured can be measured.

[0044] In this embodiment, the first sensor unit 20A detects the current value (I ３ The second sensor unit 20B can measure the current value (I １ ) can be measured. ２ ) is calculated from the current values ​​measured by the first sensor unit 20A and the second sensor unit 20B. When each sensor unit measures the current value flowing through the corresponding bus bar, the current value I ３ The following will explain the case where the following is measured.

[0045] 4 is a cross-sectional view showing a state in which a magnetic field generated from each bus bar in the current sensor according to the first embodiment of the present invention is detected by a first magnetic detection element of a first sensor unit, and FIG. 5 is a cross-sectional view showing a state in which a magnetic field generated from each bus bar in the current sensor according to the first embodiment of the present invention is detected by a second magnetic detection element of the first sensor unit.

[0046] First, as shown in FIG. 4, the magnetic field B detected by the first magnetic detection element 30A is １１ is the sum of the magnetic fields generated from each bus bar and the external magnetic field. When a first current flows, a first magnetic field B1 is generated around the first bus bar 10A. When a second current flows, a second magnetic field B2 is generated around the second bus bar 10B. When a third current flows, a third magnetic field B3 is generated around the third bus bar 10C. In addition, due to external influences, an external magnetic field B ｅｘTherefore, the magnetic field B detected by the first magnetic detection element 30A is １１ Is B １１ =B1+B2+B3+B ｅｘ It is expressed as:

[0047] As shown in FIGS. 2 and 4, the first magnetic field B1 is expressed as B1=μ(½πa)I using the magnetic permeability μ and the distance a from the relationship between the magnetic flux density and the magnetic field strength. １ In the above equation, if μ(1 / 2π) is assumed to be a constant k, then B1 = (k / a)I １ It is expressed as:

[0048] Similarly, when the second magnetic field B2 of the second bus bar 10B is detected by the first magnetic detection element 30A, the second magnetic field B2 is expressed as follows: B2=μ(½πb)I ２ If μ(1 / 2π) is assumed to be a constant k, then B2 = (k / b)I ２ Furthermore, when the third magnetic field B3 of the third bus bar 10C is detected by the first magnetic detection element 30A, the third magnetic field B3 is expressed as follows: B3=μ(½πc1)I ２ If μ(1 / 2π) is assumed to be a constant k, then B3 = (k / c1)I ３ It is expressed as:

[0049] Magnetic field B detected by the first magnetic detection element 30A １１ For example, when the direction of the first sensitivity axis A1 is the positive direction, B １１ =B1+B2+B3+B ｅｘ 2 and 5, the magnetic field B of the second magnetic detection element 30B is expressed as follows: １２ Similarly to the first magnetic detection element 30A, the relationship between the magnetic field strength and the magnetic field strength is expressed by equation (2).

[0050]

[0051] In the first sensor unit 20A, the magnetic field B detected by the first magnetic detection element 30A １１ and the magnetic field B detected by the second magnetic detection element 30B. １２The measured value of the third current flowing through the third bus bar 10C can be processed by the calculation unit 40. Specifically, the calculation unit 40 can calculate the value of the current flowing through the third bus bar 10C (one bus bar to be measured) based on the differential output value between the measured value of the first magnetic detection element 30A and the measured value of the second magnetic detection element 30B in the first sensor unit 20A. ３ is calculated by the following formula:

[0052]

[0053] In order to calculate a differential output value between the measurement value of the first magnetic detection element 30A and the measurement value of the second magnetic detection element 30B, the external magnetic field B measured by the first magnetic detection element 30A and the second magnetic detection element 30B is calculated. ｅｘ Also, the current value I ３ The coefficient (c1-c2) is equal to (b-a) due to the positional relationship of the first magnetic detection element 30A with respect to each bus bar. Therefore, as shown in the above formula (3), by replacing (c1-c2) with (b-a), the current value of each bus bar can be expressed by a formula that includes the coefficient (b-a).

[0054] Furthermore, the current flowing through each bus bar is three-phase AC, and I １ +I ２ +I ３ = 0. Therefore, I １ +I ２ =-I ３ By using this in the above equation, it can be expressed by equation (4).

[0055] By calculating the differential output value between the measurement value of the first magnetic detection element 30A and the measurement value of the second magnetic detection element 30B in the first sensor unit 20A using the above formula, the difference between the measurement value of the first magnetic detection element 30A and the measurement value of the second magnetic detection element 30B is calculated as the current value I of the third current flowing through the third busbar 10C. ３ Therefore, the difference between the measurement value of the first magnetic detection element 30A and the measurement value of the second magnetic detection element 30B, that is, the measurement value V detected and calculated by the first sensor unit 20A, can be expressed as １As shown in equation (5), the current value I ３ Therefore, in the first sensor unit 20A, the current value I flowing through the third bus bar 10C is ３ It is possible to measure

[0056] In the second sensor unit 20B, the measured values ​​of the magnetic field detected by the third magnetic detection element 30C and the measured values ​​of the magnetic field detected by the fourth magnetic detection element 30D are processed by the calculation unit 40. Specifically, the value of the current flowing through the first bus bar 10A (one of the two bus bars other than the one bus bar to be measured) can be calculated based on the differential output value between the measured values ​​of the third magnetic detection element 30C and the fourth magnetic detection element 30D in the second sensor unit 20B.

[0057] The value of the current flowing through the first bus bar 10A is calculated in the same manner as in the first sensor unit 20A. As a result, the measured value V detected and calculated by the second sensor unit 20B is calculated as shown in the following equation (6): ２ is the current value I １ Therefore, in the second sensor unit 20B, the current value I flowing through the first bus bar 10A is １ It is possible to measure

[0058]

[0059] Furthermore, the calculation unit 40 calculates the current value I ３ and a current value I flowing through the first bus bar 10A (one of the two bus bars other than the bus bar to be measured). １ By adding these, it is possible to calculate the value of the current flowing through the other of the two bus bars other than the one bus bar being measured.

[0060] Specifically, the measurement value V detected and calculated by the first sensor unit 20A is １ and the measurement value V detected and calculated by the second sensor unit 20B. ２ and are added in the calculation unit 40, and I １ +I ２ +I ３Using the relationship of I = 0, the following equation (7) can be obtained. As a result, the current value I ２ is the measurement value V detected and calculated by the first sensor unit 20A. １ and the measurement value V detected and calculated by the second sensor unit 20B. ２ It can be calculated as follows.

[0061]

[0062] As described above, in the present embodiment, the magnetic fields in the first bus bar 10A, the second bus bar 10B, and the third bus bar 10C are measured by the first sensor unit 20A and the second sensor unit 20B, respectively, to obtain the current value I flowing through the third bus bar 10C. ３ is calculated based on the measured value of the magnetic field measured by the first sensor unit 20A, and the current value I １ is calculated based on the measured value of the magnetic field measured by the second sensor unit 20B, and the calculated current value I ３ and the current value I １ Based on this, the current value I flowing through the second bus bar 10B ２ This makes it possible to measure the current value of each bus bar of the three-phase AC without providing a shield between the bus bars.

[0063] Next, the circuit configuration of the current sensor 1 according to this embodiment will be described, but the circuit configuration of the current sensor 1 according to this embodiment is not limited to the following configuration.

[0064] 6 is a circuit diagram schematically illustrating a circuit configuration of the current sensor according to the first embodiment of the present invention. As shown in FIG. 6, in this embodiment, the first magnetic detection element 30A, the second magnetic detection element 30B, the third magnetic detection element 30C, and the fourth magnetic detection element 30D each have a Wheatstone bridge circuit made up of four tunneling magnetoresistance elements 31.

[0065] The detection signal of the first magnetic detection element 30A is converted into a first output value (V ＡThe detection signal of the second magnetic detection element 30B is output as a first voltage signal indicating a second output value (V Ｂ The detection signal of the third magnetic detection element 30C is output as a second voltage signal indicating a third output value (V Ｃ The detection signal of the fourth magnetic detection element 30D is output as a third voltage signal indicating a fourth output value (V Ｄ The first amplifier 32A, the second amplifier 32B, the third amplifier 32C, and the fourth amplifier 32D are each configured by an operational amplifier that performs differential amplification.

[0066] The calculation unit 40 is an analog circuit configured by connecting circuit elements such as an amplifier. The calculation unit 40 calculates the first output value (V Ａ ), a first voltage signal representing a second output value (V Ｂ a second voltage signal representing the third output value (V Ｃ a third voltage signal representing a fourth output value (V Ｄ ) is input, and a current (detection) value (I ３ ) corresponding to the first output voltage signal (V １ＯＵＴ ), the current (detection) value of the second current (I ２ ) corresponding to the second output voltage signal (V ２ＯＵＴ ), the current (detection) value of the first current (I １ ) corresponding to the third output voltage signal (V ３ＯＵＴ ) is output.

[0067] The calculation unit 40 includes a first differential amplifier 41A, a second differential amplifier 41B, and a summing amplifier 42.

[0068] The non-inverting input terminal (+) of the first differential amplifier 41A receives a first output value (V Ａ ) is input to the inverting input terminal (-), and the second output value (V Ｂ The first differential amplifier 41A receives a second voltage signal representing a first output voltage signal (V １ＯＵＴ ) is output. In this embodiment, since the above formula (5) holds, the calculation unit 40 outputs the first output voltage signal (V １ＯＵＴ) is the current (detection) value of the third current (I ３ ) can be output as a voltage signal corresponding to the

[0069] The non-inverting input terminal (+) of the second differential amplifier 41B receives the third output value (V Ｃ ) is input to the inverting input terminal (-), and a fourth output value (V Ｄ The second differential amplifier 41B receives a fourth voltage signal representing the third output voltage signal (V ３ＯＵＴ ) is output. In this embodiment, since the above formula (6) holds, the calculation unit 40 outputs the third output voltage signal (V ３ＯＵＴ ) is the current (detection) value of the first current (I １ ) can be output as a voltage signal corresponding to the

[0070] The summing amplifier 42 receives a first output voltage signal (V １ＯＵＴ ) and a third output voltage signal (V ３ＯＵＴ ) is input to the summing amplifier 42. The summing amplifier 42 outputs a second output voltage signal (V ２ＯＵＴ ) is output. In this embodiment, since the above formula (7) holds, the calculation unit 40 outputs the second output voltage signal (V ２ＯＵＴ ) is the current (detection) value of the second current (I ２ ) can be output as a voltage signal corresponding to the

[0071] In the current sensor 1 according to the first embodiment of the present invention, when measuring each bus bar of a three-phase AC current, a first sensor unit 20A and a second sensor unit 20B, each including two magnetic detection elements, are arranged between the bus bars. The two magnetic detection elements are arranged so that the distance between one of the two bus bars other than the bus bar being measured and the distance between the other of the two bus bars other than the bus bar being measured are approximately equal. The two magnetic detection elements detect magnetic fields generated by currents flowing through the bus bars, and the calculation unit 40 calculates a differential output value of the current values ​​measured by the two magnetic detection elements. This allows the measured values ​​of the magnetic fields detected by each sensor unit to be expressed only by values ​​proportional to the current value of the bus bar being measured. The two sensor units each measure the current values ​​of the two bus bars being measured. The measured value of the remaining bus bar is calculated from the current values ​​measured by each sensor unit based on the relationship between the three-phase AC currents. This eliminates the need for a shielding member to block external magnetic fields, and the measurement values ​​of each sensor unit can be expressed solely by the current value of the object to be measured, while canceling the effects of external magnetic fields. This eliminates the need for prior preparations, such as measuring the current value of each bus bar to obtain parameters. Furthermore, complex calculations based on these parameters are also unnecessary. As a result, the overall size of the current sensor 1 can be reduced while improving measurement accuracy and responsiveness.

[0072] In the current sensor 1 according to embodiment 1 of the present invention, there is no need to provide a shielding member for each bus bar and each sensor unit to block external magnetic fields, so compared to the case where a shielding member is provided, a simpler configuration and a lower-cost current sensor can be constructed.

[0073] In the current sensor 1 according to the first embodiment of the present invention, the TMR element, GMR element, AMR element or Hall element can reduce the overall size of the current sensor 1 while improving measurement accuracy and responsiveness.

[0074] In the current sensor 1 according to the first embodiment of the present invention, the bus bars and the sensor units are arranged on a single plane, thereby making it possible to configure the current sensor 1 with a reduced height.

[0075] (Embodiment 2) A current sensor according to embodiment 2 of the present invention will be described below with reference to the drawings. The current sensor according to embodiment 2 of the present invention differs from current sensor 1 according to embodiment 1 of the present invention in the arrangement of the second sensor unit, and therefore description of the same configuration as current sensor 1 according to embodiment 1 of the present invention will not be repeated.

[0076] 7 is a cross-sectional view showing the configuration of a current sensor according to a second embodiment of the present invention. As shown in FIG. 7, a current sensor 1A according to the second embodiment of the present invention includes a first bus bar 10A, a second bus bar 10B, a third bus bar 10C, a first sensor unit 20A, a second sensor unit 50B, and a calculation unit. The first sensor unit 20A measures the third bus bar 10C as one of the bus bars to be measured.

[0077] The second sensor unit 50B measures one of the two bus bars other than the one bus bar to be measured. In the present embodiment, the second sensor unit 50B measures the second bus bar 10B as one of the two bus bars other than the one bus bar to be measured.

[0078] The second sensor unit 50B is disposed between the one bus bar to be measured and the other of the two bus bars other than the one bus bar to be measured. In the present embodiment, the second sensor unit 50B is disposed between the third bus bar 10C and the first bus bar 10A, which is the other of the two bus bars other than the one bus bar to be measured.

[0079] The second sensor unit 50B includes a third magnetic detection element 60C and a fourth magnetic detection element 60D.

[0080] The third magnetic detection element 60C and the fourth magnetic detection element 60D each have a sensitivity axis oriented in the third direction (Z direction). Specifically, the third magnetic detection element 60C has a third sensitivity axis A3 oriented in the third direction (Z direction). The fourth magnetic detection element 60D has a fourth sensitivity axis A4 oriented in the third direction (Z direction).

[0081] The third magnetic detection element 60C and the fourth magnetic detection element 60D are aligned in the second direction (X direction). In this embodiment, the third magnetic detection element 60C and the fourth magnetic detection element 60D are aligned in the second direction (X direction) at approximately the same position in the third direction (Z direction).

[0082] Each of the first magnetic detection element 30A, the second magnetic detection element 30B, the third magnetic detection element 60C, and the fourth magnetic detection element 60D is capable of detecting a magnetic field generated by current flowing through the first bus bar 10A, the second bus bar 10B, and the third bus bar 10C.

[0083] The calculation unit calculates the current values ​​of the first bus bar 10A, the second bus bar 10B, and the third bus bar 10C from the output values ​​of the first sensor unit 20A and the second sensor unit 50B.

[0084] 7, when viewed from the first direction (Y direction), the distance d between the third magnetic detection element 60C and the first bus bar 10A (the other of the two bus bars other than the one bus bar to be measured) and the distance d between the fourth magnetic detection element 60D and the third bus bar 10C (the one bus bar to be measured) are approximately equal.

[0085] When viewed from the first direction (Y direction), the distance e between the third magnetic detection element 60C and the third bus bar 10C (the bus bar to be measured) and the distance e between the fourth magnetic detection element 60D and the first bus bar 10A (the other of the two bus bars other than the bus bar to be measured) are approximately equal.

[0086] When viewed from the first direction (Y direction), the third magnetic detection element 60C and the second bus bar 10B (one of the two bus bars other than the one bus bar to be measured) are disposed at a distance f1. When viewed from the first direction (Y direction), the fourth magnetic detection element 60D and the second bus bar 10B are disposed at a distance f2. Note that the distance f1 and the distance f2 may be different from each other.

[0087] In this embodiment, the first sensor unit 20A detects the current value (I ３ The second sensor unit 50B can measure the current value (I ２ ) can be measured. １ ) is calculated from the current values ​​measured by the first sensor unit 20A and the second sensor unit 50B.

[0088] As in the first embodiment, the first sensor unit 20A, the second sensor unit 50B, and the calculation unit detect and calculate the measurement value V in the first sensor unit 20A based on the following equations (8) to (14): １ , the magnetic field B detected by the third magnetic detection element 60C of the second sensor unit 50B ２１ and the magnetic field B detected by the fourth magnetic detection element 60D. ２２ The measured value V is calculated based on ２ From this, the value of the current flowing through each bus bar 10 can be calculated.

[0089]

[0090] In the current sensor 1A according to the second embodiment of the present invention, when measuring each bus bar of a three-phase AC current, a first sensor unit 20A and a second sensor unit 50B, each including two magnetic detection elements, are arranged between the bus bars. The two magnetic detection elements are arranged so that the distance between one of the two bus bars other than the bus bar being measured and the distance between the other of the two bus bars other than the bus bar being measured are approximately equal. The two magnetic detection elements detect magnetic fields generated by currents flowing through the bus bars, and a calculation unit calculates a differential output value of the current values ​​measured by the two magnetic detection elements. This allows the measured values ​​of the magnetic fields detected by each sensor unit to be expressed only by values ​​proportional to the current value of the bus bar being measured. The two sensor units each measure the current values ​​of the two bus bars being measured. The measured value of the remaining bus bar is calculated from the current values ​​measured by each sensor unit based on the relationship between the three-phase AC currents. This eliminates the need for a shielding member to block external magnetic fields, and the measurement values ​​of each sensor unit can be expressed solely by the current value of the object being measured, eliminating the need for prior preparations such as measuring the current value of each bus bar to obtain parameters. Furthermore, complex calculations based on these parameters are also unnecessary. As a result, the overall size of the current sensor 1A can be reduced while improving measurement accuracy and responsiveness.

[0091] It is desirable that the first bus bar, the second bus bar, and the third bus bar each have approximately the same cross-sectional area in order to facilitate uniformity of the amount of current flowing therethrough.

[0092] In the above-described embodiments, configurations that can be combined may be combined with each other.

[0093] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0094] 1, 1A current sensor, 10A first bus bar, 10B second bus bar, 10C third bus bar, 20A first sensor unit, 20B, 50B second sensor unit, 30A first magnetic detection element, 30B second magnetic detection element, 30C, 60C third magnetic detection element, 30D, 60D fourth magnetic detection element, 31 tunnel type magnetoresistive element, 32A first amplifier, 32B second amplifier, 32C third amplifier, 32D fourth amplifier, 40 calculation unit, 41A first differential amplifier, 41B second differential amplifier, 42 summing amplifier, A1 first sensitivity axis, A2 second sensitivity axis, A3 third sensitivity axis, A4 fourth sensitivity axis, F virtual plane.

Claims

1. A device comprising: a first bus bar, a second bus bar, and a third bus bar extending in a first direction with a distance therebetween and aligned in a second direction perpendicular to the first direction, through which a three-phase AC current flows; a first sensor unit arranged between two bus bars other than any one of the first bus bar, the second bus bar, and the third bus bar that is a measurement target; a second sensor unit that measures one of the two bus bars other than the one measurement target bus bar, and is arranged between the one measurement target bus bar and the other of the two bus bars other than the one measurement target bus bar; and a calculation unit that calculates a current value of each of the first bus bar, the second bus bar, and the third bus bar from an output value of each of the first sensor unit and the second sensor unit; the first sensor units each have a sensitivity axis oriented in a third direction perpendicular to the first direction and the second direction, and include a first magnetic detection element and a second magnetic detection element aligned in the second direction to detect a magnetic field generated by a current flowing through the first bus bar, the second bus bar, and the third bus bar; the second sensor units each have a sensitivity axis oriented in the third direction, and include a third magnetic detection element and a fourth magnetic detection element aligned in the second direction to detect a magnetic field generated by a current flowing through the first bus bar, the second bus bar, and the third bus bar; when viewed from the first direction, a distance between the first magnetic detection element and one of the two bus bars other than the bus bar to be measured, and a distance between the second magnetic detection element and the other of the two bus bars other than the bus bar to be measured, are approximately equidistant; when viewed from the first direction, a distance between the third magnetic detection element and the other of the two bus bars other than the bus bar to be measured, and a distance between the fourth magnetic detection element and the bus bar to be measured, are approximately equidistant;A current sensor, wherein the calculation unit is capable of calculating a current value flowing through the bus bar of the one object to be measured based on a differential output value between the measurement value of the first magnetic detection element and the measurement value of the second magnetic detection element in the first sensor unit, is capable of calculating a current value flowing through one of two bus bars other than the bus bar of the one object to be measured based on a differential output value between the measurement value of the third magnetic detection element and the measurement value of the fourth magnetic detection element in the second sensor unit, and is capable of calculating a current value flowing through the other of the two bus bars other than the bus bar of the one object to be measured by adding together the current value flowing through the bus bar of the one object to the current value flowing through one of the two bus bars other than the bus bar of the one object to be measured.

2. The current sensor according to claim 1, wherein each of said first sensor unit and said second sensor unit has a circuit including a tunneling magnetoresistive element.

3. The current sensor of claim 1, wherein each of said first sensor unit and said second sensor unit has a circuit including a giant magnetoresistance element.

4. The current sensor of claim 1, wherein the first sensor unit and the second sensor unit each have a circuit including an anisotropic magnetoresistive element.

5. The current sensor according to claim 1, wherein each of the first sensor unit and the second sensor unit has a circuit including a Hall element.

6. A current sensor as described in any one of claims 1 to 5, wherein each of the first bus bar, the second bus bar, the third bus bar, the first sensor unit and the second sensor unit is arranged on a virtual plane along the first direction and the second direction.