Current Detector

Abstract

To provide a multiphase integrated current detector using a magnetic core for detecting a current with high accuracy to a large current region even when a detection phase interval is uneven pitch.SOLUTION: A gap part G2 of a magnetic core C3 having a C-shape is shifted to a narrow pitch side which is a bottleneck (W8>W7), and a cross-sectional area on the opposite side thereof is enlarged (W5>W2).SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a current detection device that detects current flowing through bus bars or electric wires of multiple phases. [Background technology]

[0002] Conventional current detection devices are configured to detect the current flowing through a bus bar or an electric wire by using a roughly C-shaped magnetic core made of a magnetic material that collects the magnetic flux generated by the current in the gap, and a current detection unit that consists of a magnetic sensing element that is inserted into the gap in the magnetic core and detects the magnetic flux density.

[0003] A case made of an insulating material is used to hold the current detection unit, and the case has an opening for passing a bus bar or an electric wire therethrough, or a shape in which the bus bar is integrally molded.

[0004] In general, in a three-phase integrated current detection device for detecting the current of a three-phase motor or the like, the roughly C-shaped magnetic core, magnetic sensing element, and case openings are arranged in three horizontal rows so that the current flowing through three bus bars arranged horizontally between an inverter (power conversion device) and a three-phase motor can be detected simultaneously. In addition, the three openings are of the same size and pitch so that a predetermined bus bar can pass through them (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-139556 A (page 10, figure 3) Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, in the conventional current detection device, the bus bars aligned in the horizontal direction are arranged to match the terminal pitch dimension of the power conversion device that generates the current to be detected by the current detection device. Power conversion devices used to control three-phase motors, etc., generally use a power module with a terminal block that incorporates and integrates multiple power elements such as insulated gate bipolar transistors (IGBTs) to switch and control the frequency and amplitude of the voltage and current applied to the three-phase motor, and the bus bar is connected to the terminal block of this power module. The terminal pitch dimensions of this power module are not standardized and vary depending on the manufacturer. For example, in the case of a three-phase IGBT power module of the same specified rating, the two pitches between the three terminal blocks are different: Company A has an even pitch of 47 mm and 47 mm, Company B has an even pitch of 48 mm and 48 mm, and Company C has an unequal pitch of 31 mm and 41 mm.

[0007] In the case of an uneven pitch as represented by Company C, the cross-sectional area of ​​the approximately C-shaped magnetic core that constitutes the current detection device is determined to suit the narrowest part of the space in which the magnetic core is placed (the part where the magnetic cores on the narrower pitch side of the uneven pitch are adjacent to each other).This becomes a bottleneck, and it becomes necessary to reduce the cross-sectional area of ​​the magnetic core, resulting in the problem of increased errors due to magnetic saturation. One method for preventing magnetic saturation is to increase the size of the gap in the magnetic core, but this is not appropriate because it makes the core more susceptible to external magnetic flux.

[0008] The present invention has been made to solve the above-mentioned problems, and has an object to provide a multi-phase integrated current detection device that is capable of detecting a larger current even if the pitch between the busbars is narrow. [Means for solving the problem]

[0009] The current detection device according to the present invention includes a substantially C-shaped magnetic core having a gap that collects magnetic flux generated by a current to be detected, and a magnetic sensing element inserted into the gap. The magnetic core surrounds the current direction in both the horizontal and vertical directions, and has a gap in one horizontal direction. The horizontal dimension of the vertically formed portion is different from the horizontal dimension of the other vertically formed portion, and the gap is formed horizontally on the side where the horizontal dimension of the vertically formed portion is smaller. It is a shift from the original. Effect of the Invention

[0010] According to the present invention, by reducing the range of high magnetic flux density in the magnetic core, it is possible to obtain a current detection device that can reduce magnetic saturation in the magnetic core and detect larger currents with higher accuracy. [Brief description of the drawings]

[0011] [Figure 1] 1 is a plan view of a current detection device according to a first embodiment of the present invention. [Diagram 2] 1 is a perspective view of a current detection device according to a first embodiment of the present invention. [Diagram 3] 1 is a diagram showing an internal structure of a current detection device according to a first embodiment of the present invention. [Figure 4] FIG. 1 is a diagram showing a simulation model of a conventional example. [Diagram 5] FIG. 13 is a simulation model diagram of an improved example. [Figure 6] FIG. 2 is a simulation model diagram according to the first embodiment of the present invention. [Figure 7] 13 is a graph showing the results of a simulation. [Figure 8] FIG. 11 is a contour diagram showing a simulation result of a magnetic core C1 corresponding to a conventional example. [Figure 9] FIG. 11 is a contour diagram of a simulation result of a magnetic core C2 corresponding to an improved example. [Figure 10] 13 is a contour diagram showing a simulation result of the magnetic core C3 corresponding to the first embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] First embodiment FIG. 1 is a plan view of a current detecting device 1 in accordance with the first embodiment of the present invention (bus bars 2a to 2c are inserted through openings 3a to 3c), and FIG. 2 is a perspective view thereof. In FIG. 1, 2a to 2c are bus bars made of, for example, copper or aluminum, each having a width of 15 mm and a thickness of 2.6 mm, 3a to 3c are openings into which the bus bars 2a to 2c are inserted, and the bus bar pitch P1 (for example, 31 mm) between 2a and 2b is an unequal pitch that is narrower than the bus bar pitch P2 (for example, 41 mm) between 2b and 2c. In FIG. 2, a power conversion device (not shown) controls and outputs three-phase voltage, current frequency and magnitude, and is connected to a three-phase motor (not shown) via bus bars 2a to 2c connected thereto.

[0013] 3(a) is a plan view of the internal structure of the current detector 1, and FIG. 3(b) is a bottom view thereof, in which 6a-6c are magnetic cores, for example, made of electromagnetic steel sheets, which have a roughly C-shape with gaps 6d and are arranged to surround the periphery of the openings 3a-3c, and collect magnetic flux generated by the current to be measured flowing through the busbars 2a-2c. For example, the magnetic sensing element 4, made of a compound semiconductor Hall element, is soldered and fixed to the printed circuit board 5 in a form inserted into the gaps 6d of the magnetic cores 6a-6c, and converts the magnetic flux density generated by the current to be measured flowing through the busbars 2a-2c into a voltage and outputs it. The output signal is detected by an electronic circuit unit (not shown) soldered and fixed to the printed circuit board 5, and is output to the outside of the current detector 1.

[0014] In FIG. 3(a), the gap 6d of the approximately C-shaped magnetic core 6a is shifted, for example, by 2.25 mm S5 (the dimension from the center of the opening to the center of the gap) toward the narrow pitch (P1) from the center of the opening 3a, and the left dimension S1 of the magnetic core 6a is larger, for example, by 2 mm than the right dimension S2 of the magnetic core 6a. The gap 6d of the magnetic core 6b is shifted, for example, by 2.25 mm S6 (the dimension from the center of the opening to the center of the gap) toward the narrow pitch (P1) from the center of the opening 3b, and the right dimension S3 of the magnetic core 6b is larger, for example, by 2 mm.

[0015] In the current detector 1 configured in this manner, the left dimension S1 of the magnetic core 6a is widened to reduce the magnetic flux density in the S1 portion, while the right dimension S2 of the magnetic core 6a is shifted to the narrower core width side (S2 side) to reduce the range of high magnetic flux density. The same is true for the magnetic cores 6b and 6c. This alleviates the magnetic saturation of the magnetic cores 6a to 6c, making it possible to detect a larger current range with high accuracy. Here, the effect is verified by simulation. The simulation details are explained in FIG.

[0016] 4, busbars 2a to 2c have a width of 15 mm and a thickness of 2.6 mm, and in the verification by simulation, a direct current is applied. Also, in accordance with the first embodiment, busbar pitch P1 is 31 mm, and busbar pitch P2 is 41 mm. As the magnetic cores, three cores having the same outer shape are used for busbars 2a to 2c, and a simulation is performed for three types of magnetic cores (C1 to C3). The simulation details are described below. -The simulator used is ANSYS. · Analysis current is applied to busbars 2a to 2c in the range of 0A to 1200A in increments of 100A. An arbitrary point in the gap G1 is set as a fixed measurement point, and the magnetic flux density is analyzed. Based on the analysis results of the magnetic flux density in the gap G1 from 0 A to 800 A, a linearity estimate is obtained by the least squares method, and the error (linearity error) between this linearity estimate and the analysis results of the magnetic flux density in the gap G1 in the range of 800 A to 1200 A is calculated. The improvement effect of changing the magnetic core shape is visualized using a contour plot of the magnetic flux density of the magnetic core.

[0017] FIG. 4 shows a model of a conventional current detection device, and the shape of the magnetic core C1 corresponding to the conventional example is subject to the spatial constraint of the busbar pitch P1 (the spatial constraint of placing two magnetic cores between the right end of the busbar 2a shown in the figure and the left end of the busbar 2b shown in the figure), and the right dimension W2 of the magnetic core C1 is determined. In general, the width of the magnetic core on the left and right in the figure is equal, and the left dimension of the magnetic core C1 (the left and right dimension of the magnetic core C1) is also W2. In addition, the gap G1 is disposed in the center of the longitudinal dimension W1 of the magnetic core C1. By doing so, the magnetic core becomes linearly symmetrical with respect to the center of the longitudinal dimension W1 of the magnetic core C1, eliminating the front and back directionality, and the magnetic core can be disposed without considering the front and back.

[0018] Figure 5 shows a model of an improved current detection device, and magnetic core C2, which corresponds to the improved example, has only one of the core widths on the left or right side in the figure increased. The magnetic core for busbar 2a has only the left width increased in the figure (left dimension W5 of magnetic core C2), the magnetic core for busbar 2b has only the right width increased in the figure, and the magnetic core for busbar 2c has only the left width increased in the figure. Also, gap G1 is located in the center of longitudinal dimension W6 of magnetic core C2. The three magnetic cores are the same shape, and only the magnetic core for busbar 2b is installed facing backwards from the others.

[0019] 6 shows a model of the current detection device according to the first embodiment of the present invention, in which the magnetic core C3 corresponding to the first embodiment has the gap positioned to one side (the magnetic core for busbar 2a is to the right in the figure, the magnetic core for busbar 2b is to the left in the figure, and the magnetic core for busbar 2c is to the right in the figure) compared to the magnetic core C2 corresponding to the improved example. The three magnetic cores have the same shape, and only the magnetic core for busbar 2b is installed facing backwards from the others. The differences between the magnetic cores C1 to C3 for the busbar 2a can be summarized as follows. Core C1 Left and right core width: equal Gap: center of core Equivalent to conventional example Core C2 Left and right core width: Left is larger Gap: Center of core Corresponding to the improvement example Core C3 Left-right core width: Larger on the left Gap: Right side of core Corresponding to embodiment 1

[0020] The specific dimensions of each magnetic core are described below. FIG. 4 shows the shape of a magnetic core C1 corresponding to a conventional example. In the figure, G2 is 4.0mm W1 is 28.6mm H1 is 19.3mm W2 is 4.5mm W3 is 12.3mm. FIG. 5 shows the shape of the magnetic core C2 corresponding to the improved example. In the figure, G2 is 4.0mm, the same as C1, W6 is 30.6mm, 2.0mm larger than C1. H1 is 19.3mm and the same as C1. W5 is 6.5mm, 2.0mm larger than C1. W2 is 4.5mm and the same as C1, W4 is 13.3 mm, which is 1.0 mm larger than C1. FIG. 6 shows the shape of a magnetic core C3 corresponding to the first embodiment. In the figure, The upper dimensions are W8 16.55mm and W7 10.05mm, and the gap position is shown on the right. It is the same as core C2 except that it is shifted by 3.25 mm.

[0021] The simulation results are described below. FIG. 7 is a graph showing the linearity error obtained by simulating the magnetic flux density for each of the magnetic cores C1, C2, and C3. Table 1 shows the linearity error at 800A to 1200A. 8 to 10 are contour diagrams showing the simulation results of the magnetic flux density in the gap G1 of each of the magnetic cores C1, C2, and C3 when a current of 800 A is applied.

[0022] As shown in the "Magnetic core: C1" item in Table 1, in the magnetic core C1 corresponding to the conventional example, for example, an error of -2.2% occurs at the point of 1000 A. Also, as shown in the contour diagram of the magnetic flux density for "Magnetic core: C1" in Figure 8, it can be seen that the magnetic flux density increases at the even core width on the left and right sides of the figure (left and right dimension W2 of magnetic core C1), creating a bottleneck and causing magnetic saturation of the core. As shown in the "Magnetic core: C2" item in Table 1, the magnetic core C2, which corresponds to the improved example, shows an improvement of 0.63% compared to magnetic core C1, at -1.57% at 1000A. This improvement can be seen from the contour plot of magnetic flux density for "Magnetic core: C2" in Figure 9, where the magnetic flux density is small at the core width on the left (left dimension W5 of magnetic core C2) and the tendency to magnetic saturation is eliminated. However, just like magnetic core C1, which corresponds to the conventional example, it can be seen that the portion at W2 is a bottleneck, causing magnetic saturation of the core.

[0023] As shown in the item "Magnetic core: C3" in Table 1, the magnetic core C3 corresponding to the first embodiment of the present invention shows an improvement of 1.58% compared to the magnetic core C1 corresponding to the conventional example, for example, -0.62% at 1000 A. This improvement can also be seen from the fact that the area with high magnetic flux density is smaller at the core width on the right side of the figure (right dimension W2 of magnetic core C3) as shown in the contour diagram of magnetic flux density for "Magnetic core: C3" in Figure 10. As a result, in the first embodiment of the present invention, it is possible to provide a current detector that can detect a larger current range with high accuracy in a narrow-pitch busbar arrangement. [Table 1] [Explanation of symbols]

[0024] 1: Current detection device 2a~2c: Busbar 3a~3c: Opening 4: Magnetic sensing element 5: Printed circuit board 6a to 6c: Magnetic core 6d: Gap S1: Left dimension of magnetic core 6a S2: Right dimension of magnetic core 6a S3: Right dimension of magnetic core 6b S4: Left dimension of magnetic core 6b S5: Dimension from center of opening to center of gap S6: Dimension from center of opening to center of gap C1: Magnetic core equivalent to the conventional example C2: Magnetic core equivalent to the improved example C3: Magnetic core corresponding to the first embodiment G1: Gap G2: Gap dimension P1: Busbar pitch P2: Busbar pitch H1: Short side dimension of magnetic core W1: Longitudinal dimension of magnetic core C1 W2: Left and right dimension of magnetic core C1, right dimension of magnetic core C2, right dimension of magnetic core C3 W3: Top dimension of magnetic core C1 W4: Top dimension of magnetic core C2 W5: Left dimension of magnetic core C2, left dimension of magnetic core C3 W6: Longitudinal dimension of magnetic core C2, Longitudinal dimension of magnetic core C3 W7: Top dimension of magnetic core C3 W8: Top dimension of magnetic core C3

Claims

1. A current detection device comprising an approximately C-shaped magnetic core having a gap that collects magnetic flux generated by the current to be detected, and a magnetic sensing element inserted into the gap, wherein the magnetic core surrounds the current direction in both the horizontal and vertical directions, has the gap in one part of the horizontal direction, the horizontal dimension of the part formed in the vertical direction differs from the horizontal dimension of the other part formed in the vertical direction, and the gap is shifted horizontally toward the side where the horizontal dimension of the part formed in the vertical direction is smaller.

2. 2. The current detection device according to claim 1, wherein the magnetic core comprises at least two magnetic cores, the magnetic cores being arranged so that the sides of the vertically formed portions having smaller horizontal dimensions are close to each other.

3. 2. The current detection device according to claim 1, wherein the magnetic cores are at least three in number, and the magnetic cores are arranged so that the sides of the vertically formed portions having smaller horizontal dimensions are close to each other and the sides of the vertically formed portions having larger horizontal dimensions are close to each other.

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