Coreless current sensor

Abstract

To provide a coreless current sensor capable of obtaining high detection sensitivity even if the size is small.SOLUTION: A coreless current sensor for detecting magnetism generated by a current flowing through a lead-in current line 10 having a bent portion 11 to measure the current, the coreless current sensor comprising one or more pairs of pattern coils 1 to 4 for magnetically detecting at least a circulating magnetic flux φ generated by the lead-in current line 10 as an interlinkage magnetic flux, the respective pattern coils 1-4 are connected so that induced currents caused by induced electromotive force to be magnetically detected are added, and one pattern coil 2 of the pair of pattern coils 1 and 2 closest to the bent part 11 among the pair of pattern coils 1, 2, 3 and 4 is arranged adjacently to the bent part 11 in the inside area E1 of the bent part 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a coreless current sensor that can achieve high detection sensitivity even in a small size. [Background technology]

[0002] A conventional current sensor has a U-shaped magnetic core that sandwiches a current line, and a detection board with a magnetic detection coil disposed in the gap of the magnetic core. The structure of this current sensor is disclosed in, for example, Patent Document 1.

[0003] This current sensor uses a magnetic flux collecting core to converge the magnetic flux generated from the current line, allowing a large amount of magnetic flux to interlink with the magnetic detection coil, increasing the induced electromotive force and ensuring high detection sensitivity.In addition, because this current sensor uses a magnetic flux collecting core, the magnetic field from the outside is absorbed by the magnetic flux collecting core, reducing the external magnetic field interlinking with the magnetic detection coil and reducing the influence of the external magnetic field. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-48755 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional current sensors have had the problem of being large in three dimensions and costly because they use a magnetic core.

[0006] The present invention has been made in view of the above, and has an object to provide a coreless current sensor that can obtain high detection sensitivity even though it is small in size. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the present invention provides a coreless current sensor that detects the magnetism generated by a current flowing through a current line having a bend and measures the current, the sensor comprising one or more pairs of pattern coils that magnetically detect at least the circulating magnetic flux generated by the current line as a linkage magnetic flux, the pattern coils being connected so that induced currents resulting from the magnetically detected induced electromotive forces are added together, and one of the pair of pattern coils that is closest to the bend is positioned adjacent to the bend in an inner region of the bend.

[0008] In addition, the present invention is characterized in that, in the above invention, the other pattern coil of the pair of pattern coils closest to the bend is positioned in the outer region of the straight portion extending from the bend, away from the boundary position between the straight portion and the bend.

[0009] In addition, in the above invention, the present invention is characterized in that, of the pair of pattern coils, excluding the pair of pattern coils closest to the bend portion, each pattern coil of the pair of pattern coils that is close to the external magnetic field generating source is arranged so that the distance from the external magnetic field generating source to each pattern coil is equal.

[0010] In the above invention, a sensor substrate is provided that is fixedly disposed on an upper surface or a lower surface of the current line, and the pair of pattern coils are disposed on the sensor substrate.

[0011] In the present invention, in the above-mentioned invention, each of the pattern coils is a pattern coil of a multi-layer structure formed within the sensor substrate. [Effects of the Invention]

[0012] According to the present invention, high detection sensitivity can be obtained even with a small size. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing the general configuration of a coreless current sensor according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the state of a circular magnetic flux generated in the lead-in current line shown in FIG. [Figure 3] FIG. 3 is a diagram illustrating positions at which changes in magnetic flux density in the inner and outer regions of a current line are observed. [Figure 4] FIG. 4 is a diagram showing the change in magnetic flux density in the inner region. [Figure 5] FIG. 5 is a diagram showing the change in magnetic flux density in the outer region. [Figure 6] FIG. 6 is a diagram showing how to shift the pattern coils in order to investigate the influence of an external magnetic field generated by another current line when the other current line passing through the Z direction is arranged in the inner region. [Figure 7] FIG. 7 is a diagram showing changes in the detection voltage of the external magnetic field detected by each pattern coil and changes in the offset voltage when the pattern coils are shifted. [Figure 8] FIG. 8 is a diagram showing an example of the arrangement of each pattern coil that can reduce the influence of an external magnetic field generated by other current lines. [Figure 9] FIG. 9 is a diagram showing an example of a case where a conventional coreless current sensor having four pattern coils arranged on a sensor substrate is used, and the coreless current sensor shown in FIG. 1 having four pattern coils arranged on a sensor substrate is used. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0015] <Summary configuration> 1 is a schematic diagram showing the general configuration of a coreless current sensor according to an embodiment of the present invention. This coreless current sensor does not use a magnetic core, but instead uses planar pattern coils 1 to 4 that are wound in a spiral shape.

[0016] As shown in FIG. 1, the coreless current sensor has a lead-in current wire 10 drawn in from a current wire carrying a current. A current I flows in lead-in current wire 10 between ends A and B. Lead-in current wire 10 has bent portions 11 and 12. Bent portion 11 is interposed between current wires 13 and 14, bending current wire 13, which extends in the Y direction, in the X direction. Bent portion 12 is interposed between current wires 14 and 15, bending current wire 14, which extends in the X direction, in the -Y direction. Current wire 14 has lead-in portion 18, which draws in current wire 14 in the -Z direction. Lead-in portion 18 is folded back and connected to, for example, the inside of a relay that interrupts the conduction of lead-in current wire 10.

[0017] The coreless current sensor has one or more pairs of pattern coils, namely, a pair of pattern coils 1 and 2 and a pair of pattern coils 3 and 4, which magnetically detect the circulating magnetic flux φ generated by the incoming current line 10 as a flux linkage. Each of the pattern coils 1 to 4 is disposed on a sensor substrate 8 fixedly disposed on the upper or lower surface of the current line 14. The pattern coils 2 and 4 are disposed on the inner region E1 side of the bent portion 11, and the pattern coils 1 and 3 are disposed on the outer region E2 side of the bent portion 11. Therefore, since the pattern coils 1 to 4 are disposed on the flat sensor substrate 8, they are formed on the same plane. Furthermore, the pattern coils 1 to 4 are disposed on the XY plane formed by the incoming current line 10, and the pattern coils 1 and 3 and the pattern coils 2 and 4 are disposed with the current line 14 sandwiched between them.

[0018] Here, the pattern coils 1 and 3 have the same winding direction, and the pattern coils 2 and 4 have the same winding direction but are different from the winding direction of the pattern coils 1 and 3. The pattern coils 1 to 4 are connected so that induced currents resulting from the induced electromotive forces to be magnetically detected are added together. That is, the induced currents IE1 to IE4 generated by the pattern coils 1 to 4 are added together and input to the current calculation unit 100. The current calculation unit 100 calculates the current I flowing through the incoming current line 10 based on this added induced current. The current calculation unit 100 also has functions such as signal amplification and noise removal.

[0019] The number of turns of each of the pattern coils 1 to 4 is the same, and the winding directions of the pattern coils 1 and 3 and the pattern coils 2 and 4 are opposite to each other, so that the induced currents generated by a uniform external magnetic field are cancelled out.

[0020] Each of the pattern coils 1 to 4 is a pattern coil with a multi-layer structure formed within the sensor substrate 8, for example, a four-layer structure or an eight-layer structure. By increasing the number of layers, sensitivity can be increased.

[0021] <Improved sensitivity> In this embodiment, one pattern coil 2 of the pair of pattern coils 1, 2, 3, 4 that is closest to the bent portion 11 is arranged adjacent to the bent portion 11 in an inner region E1 of the bent portion 11. The other pattern coil 1 of the pair of pattern coils 1, 2 that is closest to the bent portion 11 is arranged away from the boundary position P1 between the current line 14 and the bent portion 11 in an outer region E2 of the straight portion (current line 14) extending from the bent portion 11.

[0022] The reason why the pattern coils 1 and 2 are arranged in this manner is that, as shown in Fig. 2, the magnetic flux density due to the circulating magnetic flux φ is high in the inner region E1 of the bent portion 11, and the magnetic flux density due to the circulating magnetic flux φ is low in the outer region E2 of the bent portion 11. This makes it possible to increase the magnetic detection sensitivity of the pattern coil 2 and to suppress a decrease in the magnetic detection sensitivity of the pattern coil 1. As a result, it is possible to increase the magnetic detection sensitivity of each of the pattern coils 1 to 4.

[0023] FIG. 3 is a diagram illustrating positions at which changes in magnetic flux density are observed in the inner region E1 and the outer region E2 of the current line 14. FIG. 4 is a diagram illustrating changes in magnetic flux density in the inner region E1. FIG. 5 is a diagram illustrating changes in magnetic flux density in the outer region E2. The line L2 shown in FIG. 3 indicates an observation position that passes through the center of the pattern coils 2 and 4 and is parallel to the current line 14, and FIG. 4 is a diagram illustrating changes in magnetic flux density with changes in position on this line L2. As shown in FIG. 4, large magnetic flux densities are observed at boundary positions P1 and P2. For example, the magnetic flux density is large in region E11 at boundary position P1. By arranging the pattern coil adjacent to the bend 11, sensitivity can be increased.

[0024] On the other hand, line L1 shown in Fig. 3 indicates an observation position that passes through the center of pattern coils 1 and 3 and is parallel to current line 14, and Fig. 5 is a diagram showing the change in magnetic density with change in position on line L1. As shown in Fig. 5, the magnetic flux density near boundary positions P1 and P2 is lower than that toward the center of current line 14. For example, the magnetic flux density is lower in region E12 near boundary position P1, and moving the pattern coil away from boundary position P1 prevents a decrease in sensitivity. Note that in Figs. 4 and 5, the magnetic flux density is lower at lead-in portion 18 because current line 14 is bent in the +Z direction.

[0025] Therefore, the pattern coil 2 is disposed adjacent to the bent portion 11 in the inner region E1 of the bent portion 11. The pattern coil 1 is disposed away from the boundary position P1 between the current line 14 and the bent portion 11 in the outer region E2 of the straight portion (current line 14) extending from the bent portion 11. The pattern coil 4 may be disposed at any position on the central side of the current line 14 where the magnetic flux density is flat, and the pattern coil 3 may be disposed at any position on the central side of the current line 14 where the magnetic flux density is flat without decreasing.

[0026] Although pattern coils 1 and 2 are arranged relative to bend 11, pattern coils may also be arranged in a similar position relative to bend 12. Also, a pair of pattern coils may be provided for each of bends 11 and 12. Furthermore, pattern coils 3 and 4 do not need to be provided if there is no space for them, and if there is space for them, an additional pair of pattern coils may be provided.

[0027] <Effects of external magnetic fields> Although the pattern coils 1 to 4 can cancel the influence of a uniform external magnetic field, they may be affected by an external magnetic field generated from a nearby external magnetic field source, which is not uniform. For example, as shown in Fig. 6, if another current line 110 passing through the Z direction in the inner region E1 is arranged as an external magnetic field source, the magnetic flux generated by the current line 110 may become a magnetic flux linkage of the pattern coils 1 to 4. Since the magnetic flux generated by the current line 110 is almost parallel to the detection surfaces of the pattern coils 1 to 4, there may be some linkage, although there may be some.

[0028] 7 is a diagram showing the detected voltages of each pattern coil due only to the magnetic flux generated by the current line 110 when the positions of the pattern coils 1 and 3 and the pattern coils 2 and 4 are shifted from the boundary position P1, and the offsetting voltages of each pattern coil. As shown in FIG. 7, the pattern coils 1 and 3 become approximately equal to the current line 110 as they are shifted in the X direction (right side), so the influence (detected voltage) of the external magnetic field (magnetic flux generated by the current line 110) increases, while the pattern coils 2 and 4 become farther from the current line 110 as they are shifted in the -X direction (left side), so the influence of the external magnetic field decreases. Furthermore, the detected voltage of the external magnetic field by the pattern coils 1 and 2 is smaller than the detected voltage of the external magnetic field by the pattern coils 3 and 4 because they are farther from the current line 110.

[0029] The offset addition on the left side of Fig. 7 is the voltage (equivalent to induced current) detected by the current calculation unit 100 due to the external magnetic field, and it can be seen that there is a position where the detected voltage becomes zero as the pattern coils 1 and 3 and the pattern coils 2 and 4 are shifted. By arranging the pattern coils 1 to 4 at this shifted position, it is possible to eliminate the influence of the external magnetic field on the current line 110. In this case, as shown in Fig. 8, it was found that the distances d1 and d2 between the current line 110a of the current lines 110 closest to the pattern coils 1 to 4 and the pattern coils 3 and 4 are approximately equal.

[0030] In this embodiment, the pattern coils 1 and 2 are arranged at fixed positions, and the pattern coils 3 and 4 can be arranged at any positions. Moreover, since the pattern coils 3 and 4 are close to the current line 110 and are greatly affected by an external magnetic field, the influence of the external magnetic field can be suppressed by making the distances d1 and d2 between the pattern coils 3 and 4 and the current line 110a approximately equal.

[0031] <Application to electricity meters> Three-phase, three-wire and single-phase, three-wire energy meters use two current sensors. If these two current sensors use magnetic cores, the space required to place the magnetic cores is large, the current line routing is complicated, and insulation measures are required. However, by using the above-mentioned coreless current sensors instead of the two current sensors, the current line routing is simplified and the overall size can be reduced.

[0032] FIG. 9 is a diagram showing an example of a case in which a conventional coreless current sensor in which four pattern coils 101 to 104 are arranged on a sensor substrate 108 is used, and a coreless current sensor in which four pattern coils 1 to 4 are arranged on the sensor substrate 8 shown in FIG.

[0033] The current wire 110 (current wires 110a, 110b) between the terminals 3S and 3L is a current wire that is folded back toward the relay 41, and a conventional sensor board 108 is disposed between the two folded current wires 110a, 110b. The pattern coils 101 and 102 of the sensor board 108 detect the circulating magnetic flux of the current wire on the 3S side, and the pattern coils 103 and 104 detect the circulating magnetic flux of the current wire 110b on the 3L side. In this case, by winding the pattern coil 102 and the pattern coil 103 in the same direction, the pattern coil 102 simultaneously detects the circulating magnetic flux of the current wire 110b on the 3L side, and the pattern coil 103 detects the circulating magnetic flux of the current wire 110a on the 3S side, thereby increasing the detection sensitivity.

[0034] The sensor substrate 8 of the coreless current sensor shown in Fig. 1 is disposed on the incoming current wire 10 between the terminal 1S and the terminal 1L. As described above, the current wire 14 has the incoming portion 18 and is drawn into the relay 40.

[0035] This allows both current sensors used in the power meter to be replaced with coreless current sensors, which reduces the size and space required compared to using one or more current sensors with magnetic cores, while also significantly improving sensitivity. Furthermore, even when the current line 110 is placed near the incoming current line 10, the placement of the pattern coils 3 and 4 shown in Figure 8 reduces the influence of the magnetic field generated by the current line 110.

[0036] In the above embodiment, the bent portions 11 and 12 are bent at right angles, but this is not limiting and they may be bent at an angle exceeding 90° or less than 90°. Also, the bent portions 11 and 12 may be bent with a partial curve.

[0037] Note that the configurations illustrated in the above embodiments and modifications are merely functional schematics and are not necessarily physically configured as shown. In other words, the distribution and integration of each device and component is not limited to that illustrated, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various usage situations, etc. [Explanation of symbols]

[0038] 1~4,101~104 pattern coil 1S,1L,3S,3L terminal 8,108 Sensor board 10 Lead-in current line 11,12 Bend 13,14,15,110,110a,110b Current line 18 Retraction section 40,41 Relay 100 Current calculation unit A,B ends d1,d2 distance E1 inner area E2 outer area E11,E12 area I current IE1~IE4 Induction current L1,L2 straight line P1,P2 boundary position φ Circulating magnetic flux

Claims

1. A coreless current sensor that detects magnetism generated by a current flowing through a current line having a bent portion and measures the current, one or more pairs of pattern coils for magnetically detecting at least the circulating magnetic flux generated by the current line as a linkage magnetic flux; The pattern coils are connected so that the induced currents resulting from the magnetically detected induced electromotive force are added together.

10. The coreless current sensor according to claim 9, wherein one of the pair of pattern coils closest to the bending portion is disposed adjacent to the bending portion in an inner region of the bending portion.

2. 2. The coreless current sensor according to claim 1, wherein the other pattern coil of the pair of pattern coils closest to the bent portion is positioned in an outer region of the straight portion extending from the bent portion, away from a boundary position between the straight portion and the bent portion.

3. 3. The coreless current sensor according to claim 1, wherein, of the pair of pattern coils, excluding the pair of pattern coils closest to the bent portion, each pattern coil of the pair of pattern coils closest to the external magnetic field source is arranged so that the distance from the external magnetic field source to each pattern coil is equal.

4. a sensor substrate fixedly disposed on an upper surface or a lower surface of the current line; 3. The coreless current sensor according to claim 1, wherein the pair of pattern coils are disposed on the sensor substrate.

5. 3. The coreless current sensor according to claim 1, wherein each of the pattern coils is a pattern coil having a multi-layer structure formed within the sensor substrate.

Images