JP2013053914A - Current measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current measuring device that detects a magnetic field by a current to measure the current and make current detection sensitivity variable.SOLUTION: When a current I to be measured is made to flow through a primary conductor 1 in which an open hole 2 is provided, the current flows in a Y-axis direction, which is a principal direction, in a location having no influence of the open hole 2 and a generated flux is directed in an X-axis direction orthogonal to the direction of the current. Since a bypass current Ia is tilted to the Y-axis direction in the vicinity of the open hole 2, a magnetic field vector component Hy in the Y-axis direction and a vector component Hx in the X-axis direction are generated at the same time. The vector component Hy of the magnetic flux in the Y-axis direction is measured by magnetic detection elements 3a and 3b. As an input-output position, input ends A to C and output ends A' to C' are provided. The input-output positions of the current I to be measured are selected by combining these ends A to C'. When the ends A-A' are selected, since the magnetic field vector component Hy directed to the Y-axis direction of the bypass current Ia becomes larger than that of when ends B-B' are selected, detection sensitivity of current measurement becomes higher.

Description

  The present invention obtains the current amount of the current to be measured by detecting the magnetic field in the vicinity of the conductive region of the primary conductor through which the current to be measured flows, and changes the input / output terminal of the current to be measured to the primary conductor. The present invention relates to a current measuring device that varies the detection sensitivity.

  In the current measurement, a magnetic field is generated in the gap portion of the magnetic core that surrounds the current to be measured, the magnetic field is detected as a voltage value through the magnetic detection element, and the voltage value is calibrated and converted, thereby converting the current to be measured. Current measuring devices for calculating quantities are conventionally used.

  As an example, there is a current measuring device using a fluxgate element as a magnetic detection element as in Patent Document 1. In Patent Document 1, since the primary conductor functions as an exciting coil, the strength of the magnetic field generated in the magnetic core can be adjusted by changing the number of turns of the primary conductor.

  Therefore, the number of turns to the magnetic core can be changed by changing the primary conductor connection method like a transformer, the magnetic flux generated in the magnetic core can be adjusted, and the sensitivity of the current measuring device can be varied.

  On the other hand, a coreless current measuring device that is suitable for miniaturization and does not require a core as shown in Patent Document 2 has been proposed.

US2010 / 0301852A1 JP 2009-276359 A

  However, in the current measuring device that causes the primary side conductor to function as an exciting coil as in Patent Document 1, the number of turns of the primary side conductor can be changed to select the magnetic flux generated in the magnetic core. It is not suitable for miniaturization because it requires it.

  In addition, in a coreless current measuring apparatus such as Patent Document 2, a circulating magnetic field generated by a primary conductor is directly detected by a magnetic detection element. Therefore, as in Patent Document 1, a method of increasing the number of turns of a primary conductor is used. It is difficult to take.

  The object of the present invention is to eliminate the above-mentioned problems, measure the current to be measured by detecting the magnetic field component facing the main direction of the bypass current with respect to the non-conductive region of the primary conductor, and change the current distribution in the primary conductor. It is an object of the present invention to provide a current measuring device that can vary the current detection sensitivity.

  In order to achieve the above object, a current measuring apparatus according to the present invention provides a non-conductive region in a primary conductor through which a current to be measured flows, and sets a main direction of the measured current to bypass the non-conductive region by a magnetic detection element. In a current measuring apparatus for measuring current by detecting a magnetic field component facing, the distribution of the bypass current flowing through the primary conductor is changed by changing the input / output position of the current to be measured to the primary conductor. The detection sensitivity of the measurement current is variable.

  According to the current measurement device of the present invention, the current to be measured flowing through the primary conductor is measured, and the input / output position of the primary conductor is selected to vary the detection sensitivity of the current to be measured.

It is a basic perspective view of the current measuring device of an example. It is explanatory drawing of the electric current and magnetic field in a primary conductor. It is explanatory drawing of the current pathway in a primary conductor. It is a block diagram of a detection circuit. It is a graph of a detection current and an output voltage. It is a perspective view of a specific Example. It is a perspective view of the 1st modification. It is a perspective view of the 2nd modification. It is a block diagram of the 3rd modification. It is a block diagram of the 4th modification.

The present invention will be described in detail based on the embodiments shown in the drawings.
FIG. 1 is a basic perspective view of a current measuring device that performs current measurement on a current to be measured. The primary conductor 1 is in the form of a bus bar or the like formed of a copper foil pattern or a copper plate on a printed circuit board, for example, and the current I to be detected flows through the primary conductor 1.

  A circular through hole 2 which is a non-conductive region is provided in the approximate center of the primary conductor 1 in order to partially interrupt the current. For this reason, a part of the current I to be measured is shown in FIG. As described above, the detour current Ia sympathizes outward on both sides of the through hole 2. Note that the non-conductive region is not necessarily the through-hole 2 but may be embedded with a non-conductive substance that blocks current.

  For convenience of explanation, a coordinate axis is set for the primary conductor 1, the center of the through hole 2 is the origin O, the main direction in which the current I to be measured flows is the Y axis, and the width direction that is the orthogonal axis is the X axis. The thickness direction will be described as the Z axis.

  On the primary conductor 1, two magnetic detection elements 3a and 3b are spaced apart from the through hole 2 in the lateral X-axis direction, arranged in series in the Y-axis direction and symmetrically with respect to the X-axis. Thus, the outputs are detected differentially. The detection units 4a and 4b on the magnetic detection elements 3a and 3b are arranged so that the Y-axis direction is the magnetic field detection direction. The center positions of the detection units 4a and 4b are the distance dx in the X-axis direction from the origin O, the distance dy across the X-axis in the Y-axis direction, and the distance dz from the surface of the primary conductor 1 in the Z-axis direction. It is provided at a shifted location.

  As shown in FIG. 2, when the current I to be measured flows through the primary conductor 1, the current I to be measured flows in the Y-axis direction, which is the main direction, at a place where there is no influence of the through hole 2. Since the magnetic flux generated by the current is directed in a direction perpendicular to the current direction, a magnetic field having only a vector component Hx in the X-axis direction is provided within the width w on the input side of the primary conductor 1 as in the magnetic field vector component Hc0.

  However, since the bypass current Ia is inclined with respect to the Y-axis direction in the vicinity of the through hole 2, a magnetic field vector component Hc1 in which the magnetic field is distorted on both sides of the through hole 2 is generated by the bypass current Ia. That is, both the vector component Hy in the Y-axis direction and the vector component Hx in the X-axis direction are generated in the slope portion of the bypass current Ia. The vector sum of the vector component Hy and the vector component Hx is proportional to the magnitude of the current I to be measured, and since the current direction is symmetrical on both the positive and negative sides of the Y-axis of the through-hole 2, the vector component Hy is symmetrical across the X-axis. And the polarity is reversed.

  In the current measurement, in order to detect only the magnetic field vector component Hy in one direction that is the Y-axis direction, the magnetic detection elements 3a and 3b to be used are preferably highly directional magnetic impedance elements and orthogonal flux gate elements, In the embodiment, a magneto-impedance element is used. As the detection units 4a and 4b, a pattern made of a magnetic thin film and arranged in parallel in a Y-axis direction in the magnetic field detection direction is formed. A high-frequency pulse in the MHz band is applied to the electrodes 5 at both ends, and a change in voltage amplitude of only the magnetic field vector component Hy in the Y-axis direction is obtained as a sensor signal from both ends of the detection units 4a and 4b due to a change in magnetic field. Measurement can be performed by conversion.

  The primary conductor 1 has a plurality of input / output positions of the current I to be measured as input ends A, B, C on the left end, center, and right end on the input side, and these input ends A, B, C on the output side. Output end portions A ′, B ′, and C ′ are provided so as to face each other. The input / output position of the current I to be measured can be selected by combining these input / output end portions A to C ′. For example, FIG. 2 shows a current path when the central input / output end B-B ′ is selected as the current input / output position, and the current path has a symmetrical distribution with respect to the Y axis.

  FIG. 3 shows a current path when the end AA ′ is selected as the input / output position of the current I to be measured with respect to the primary conductor 1, and the through hole 2 is compared with the case where the end BB ′ is selected. Since the magnetic field component facing the main direction of the current I to be measured in the vicinity of is increased, the detection sensitivity of current measurement is increased. From this principle, it is possible to select a desired current detection sensitivity by changing the input / output position of the measured current I of the primary conductor 1.

  FIG. 4 shows a configuration diagram of the detection circuit. The detection units 4a and 4b of the magnetic detection elements 3a and 3b are connected to a resistor R that forms a bridge with respect to the CR pulse oscillation circuit. After the amplitude change from the voltage across the detection units 4a and 4b is taken out by the amplitude detection circuit, the differential amplification circuit performs differential amplification on the outputs of the detection units 4a and 4b, and outputs the current measurement device as an output. obtain.

  In this case, the outputs of the detection units 4a and 4b have the same sensitivity and the same absolute value if they are in symmetrical positions with the X axis in between. This is twice the absolute value of 4a or 4b. In addition, extraneous magnetic field noise is in phase in the detection units 4a and 4b in a narrow range, and by detecting the outputs of the detection units 4a and 4b differentially, the magnetic field noise is canceled and superimposed on the output. Instead, only the vector component Hy of the detour current Ia is measured.

  Here, when all three input / output ends of the current I to be measured are connected, that is, the end (A + B + C) − (A ′ + B ′ + C ′) connection method, or the end AA ′, The output voltage was compared with the case where one part was connected like BB 'and CC'.

  For example, when the primary conductor 1 is energized with the current 3A (ampere), the sensor signal due to the voltage amplitude change is 116.1 mV at the end (A + B + C) − (A ′ + B ′ + C ′) connection. became. On the other hand, when only the end A-A 'is connected, the voltage is 253 mV, similarly, the end B-B' is 151.1 mV, and the end C-C 'is 50.7 mV. From this result, it is understood that the sensitivity of the current measuring device can be varied by selecting the input / output position of the measured current I to the primary conductor 1 of the measured current I.

  It is needless to say that the current measurement sensitivity can be changed also by the connection between two opposing locations, for example, a connection such as the end (A + B) − (A ′ + B ′). Note that connections other than the opposing ends, for example, end A and end B ′ can be connected, but the current distribution is not symmetric between the detectors 4a and 4b, so that differential output processing is possible. There are often complicated issues.

  FIG. 5 shows a graph in which the current I to be measured is measured by changing the AC current (60 Hz) from 1 to 10 Arms and supplying the primary conductor 1 with current in the current measuring device. From this result, it can be seen that the linearity is maintained in the range of 1 to 10A.

  FIG. 6 shows a specific example of the current measuring apparatus, which is configured by providing a plurality of input / output terminals on the primary conductor 1, and the input terminals 6a, Output terminals 6d, 6e, 6f are connected to 6b, 6c and output ends A ′, B ′, C ′. By using these input / output terminals 6a, 6b, 6c, 6d, 6e, and 6f, the current detection sensitivity can be varied by selecting one set or a plurality of sets at the input end and the output end as described above. .

  FIG. 7 is a perspective view of the first modified example, in which an input / output position is selected by soldering the electric wire 7 at a position corresponding to the input / output ends A to C ′ of the current I to be measured of the primary conductor 1 and detected. Sensitivity is changed. This eliminates the need to provide the input / output ends A to C ′ in the primary conductor 1 as shown in FIG.

  In FIG. 7, soldering is adopted as a method of fixing the electric wire 7, but a method of fixing by using a clamp screw, for example, is also conceivable instead of soldering.

  FIG. 8 shows a perspective view of the second modified example, in which a plurality of mounting holes 8 made of screw holes are formed at positions corresponding to the end portions A to C ′ of the primary conductor 1, and the mounting holes 8 are selected. The input / output position of the current I to be measured is selected by using the screwing portion of the electric wire. Thereby, even when it fixes to the primary conductor 1 with a screw mechanically, the measurement sensitivity of the to-be-measured current I can be varied by selecting the attachment hole 8.

  FIG. 9 is a configuration diagram of the third modification example, in which a bar-shaped contact 9 is made slidable at an input end and an output end, and the contact 9 is fixed by, for example, a screw. The contact point between the primary conductor 1 and the contact 9 is changed.

  In this case, the input / output end portions A to C ′ are not specified, and may be brought into contact with arbitrary portions of both end portions of the primary conductor 1. In addition, it is preferable to make the contactor 9 contact so that the detour current Ia with respect to the through hole 2 is symmetric about the X axis. Thereby, the current detection sensitivity can be continuously adjusted.

  FIG. 10 is a configuration diagram of the fourth modified example, and shows an example in which the current detection sensitivity is adjusted using a switch. A switch 10 is arranged at each of the input end portions A to C and the output end portions A ′ to C ′ provided in the primary conductor 1, and switch control is performed by combining the input / output terminals A to C ′ according to the current detection sensitivity. .

  As a result, the current detection sensitivity can be changed by remote switch control without mechanically changing terminals or the like to the input / output ends A to C ′.

DESCRIPTION OF SYMBOLS 1 Primary conductor 2 Through-hole 3a, 3b Magnetic detection element 4a, 4b Detection part 5 Electrode 6a-6c, 6d-6f Input / output terminal 7 Electric wire 8 Mounting hole 9 Contact 10 Switch A, B, C, A ', B' , C 'Input / output end

Claims (9)

  A current measuring device that measures a current by providing a non-conductive region in a primary conductor through which a current to be measured flows, and detecting a magnetic field component facing the main direction of the current to be measured that bypasses the non-conductive region by a magnetic detection element The detection current detection sensitivity can be varied by changing the distribution of the bypass current flowing through the primary conductor by changing the input / output position of the current to be measured to the primary conductor. Current measuring device.   The magnetic detection element is capable of detecting a magnetic field component in one direction, and the magnetic detection element is arranged at a side of the non-conductive region so that the magnetic field detection direction is a main direction of the current to be measured. The current measuring device according to claim 1.   The current measuring apparatus according to claim 1, wherein input / output positions of the current to be measured to the primary conductor are provided at a plurality of locations on the input side and the output side of the primary conductor, respectively.   The current measuring apparatus according to claim 1, wherein the input / output position is disposed opposite to an input side and an output side of the primary conductor.   5. The current measuring apparatus according to claim 3, wherein terminals are connected by selecting input / output positions on the input side and output side.   The current measuring device according to claim 3 or 4, wherein the input / output positions on the input side and the output side are selected and the electric wire is soldered.   5. The current measuring device according to claim 3, wherein attachment holes are provided at input / output positions on the input side and the output side, and electric wires are connected by selecting these attachment holes.   5. The current measuring device according to claim 3, further comprising a contactor that selects input / output positions on the input side and the output side to continuously change the contact location.   The current measuring device according to claim 3 or 4, wherein a connection location is selected by a switch for input / output positions on the input side and output side.

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