JP2021043071A - Current sensor and watthour meter - Google Patents

Abstract

To provide a current sensor and a watthour meter which are easy to manufacture and hardly affected by an external magnetic field, and which have a good linearity of current detection characteristics in a wide range.SOLUTION: Provided is a current sensor 2 for measuring a magnetic field formed in the surrounding of a current bar 1 that flows a current and detecting a current signal flowing in the current bar 1, in which coil pattern parts 2a-2d which are portions of resin molding having coil patterns formed on the surface with a metal film are arranged in plurality so as to cover the current bar 1. The coil patterns are a pair of coil patterns having the same shape and arranged symmetrically with respect to the axis of the current bar 1. A formed connecting line is formed with a metal film on the surface of a pedestal part 20 which is a portion of the resin molding, the connecting line connecting the coil patterns in series so as to add an induced voltage generated in the coil patterns.SELECTED DRAWING: Figure 1

Description

The present invention relates to a current sensor and a watt-hour meter that are easy to manufacture, are not easily affected by an external magnetic field, and have good linearity of current detection characteristics over a wide range.

Conventionally used current sensors include current transformers (current transformers: CT), configurations in which magnetic and electrical conversion elements such as Hall elements are arranged in the gaps of the magnetic collector cores, and gaps in the magnetic collector cores. There is a configuration having an element in which a coil pattern is formed on a winding coil or a dielectric substrate. In particular, the method of arranging a magnetic-electric conversion element such as a Hall element or an element having a coil pattern formed on a substrate in the gap portion of the magnetic collection core is electrically separated from the circuit through which the primary current flows, which is the measurement target. Therefore, it is excellent in that the current can be measured accurately without affecting the circuit on the primary current side. Further, the method of arranging the elements forming the coil pattern has excellent linearity and temperature characteristics, has a small number of parts, and is easy to manufacture (see Patent Document 1).

In the current sensor described in Patent Document 1, a current bar is passed through the central opening of the annular magnetic collecting core, and a substrate having a coil pattern is arranged in the gap portion of the magnetic collecting core. When a current flows through the current bar, a magnetic flux proportional to the magnitude of the current flowing through the current bar is generated around the current path. The generated magnetic flux is collected by the magnetic collecting core. When the current is a periodic current, the magnetic flux generated according to the period also changes periodically. As a result, an induced voltage corresponding to the magnitude and frequency of the current is generated in the detection coil having the coil pattern, and this induced voltage is used as a detection signal of the current flowing through the current bar.

Japanese Unexamined Patent Publication No. 2010-48755

By the way, in the current sensor in which the magnetic conversion element is arranged in the gap portion of the magnetic collecting core, the magnetic flux generated in the gap portion is determined by the magnetic characteristics of the magnetic collecting core and the shape of the gap portion. By setting the distance of this gap to several mm, it is possible to obtain current detection characteristics with relatively good linearity. However, due to the non-linearity of the magnetic material used in the magnetic concentrator with respect to the magnetic field, the linearity of the current detection characteristics There is a problem that it may get worse.

Specifically, when a large current flows through the current bar, the magnetic permeability decreases due to the magnetic saturation of the magnetic material used in the magnetic collecting core, and the magnetic flux generated in the gap portion also decreases accordingly. The magnetic flux generated with respect to the current is not in an ideal proportional relationship, and the linearity deteriorates.

Further, in general, the magnetic permeability of a magnetic material has the largest magnetic permeability in a predetermined magnetic field depending on the material, and the initial magnetic permeability is smaller than the maximum magnetic permeability. Therefore, even when a small current flows, the magnetic flux generated decreases due to the low magnetic permeability, the magnetic flux generated with respect to the measured current is not in an ideal proportional relationship, and the linearity of the current detection characteristics deteriorates. To do.

As a current sensor that does not have these problems, there is a method of arranging an air core coil around the current bar and measuring the induced voltage generated in response to a change in magnetic flux, such as a Rogowski coil. However, when using the Rogowski coil, it is necessary to form the coil so as to surround the current bar, and a dedicated winding machine and winding jig according to the coil shape and coil size are required. There is a problem that it is not easy to manufacture.

Further, if the winding of the Rogowski coil has uneven winding, there is a problem that it is easily affected by the misalignment of the current bar, and there is a problem that it is not easy to manufacture an accurate current sensor. Further, when arranging the Rogowski coil, a method is adopted in which one end of the annular coil is divided and arranged so as to surround the current bar. However, in order to reduce winding unevenness as much as possible, it is preferable that one end of the annular coil is not divided for the air core coil. If it is not divided, it is necessary to pass the current bar through the central cavity. The degree becomes low, and problems such as poor assemblyability occur.

In general, it is necessary for the current sensor to be unaffected by an external magnetic field other than the magnetic field generated by the current flowing through the current bar in order to improve the accuracy of current measurement.

Further, the various current sensors described above require a housing in which several types of parts such as a current bar, a magnetic material, a magnetic conversion element, and a coil are accurately arranged and fixed, and the more components there are, the larger the number of parts. This increases and causes a problem of poor assembly.

The present invention has been made in view of the above, and provides a current sensor and a watt-hour meter that are easy to manufacture, are not easily affected by an external magnetic field, and have good linearity of current detection characteristics in a wide range. The purpose.

In order to solve the above-mentioned problems and achieve the object, the current sensor according to the present invention is a current sensor that measures a magnetic field formed around a current bar through which a current flows and detects a current signal flowing through the current bar. The present invention is characterized in that a resin molded product having a coil pattern formed of a metal film on the surface thereof is arranged so as to cover the current bar.

Further, the current sensor according to the present invention is characterized in that, in the above invention, the coil patterns have the same shape and are a pair of coil patterns arranged symmetrically with respect to the axis of the current bar.

Further, the current sensor according to the present invention is characterized in that, in the above invention, a plurality of the pair of coil pattern portions on which the pair of coil patterns are formed are arranged.

Further, in the current sensor according to the present invention, in the above invention, a connection line connecting the coil patterns in series so as to add an induced voltage generated in the coil pattern is formed on the surface of the resin molded product with a metal film. It is characterized by having done it.

Further, the current sensor according to the present invention is characterized in that, in the above invention, the coil pattern surface on which the coil pattern is formed is perpendicular to the magnetic flux generated by the current bar.

Further, in the current sensor according to the present invention, in the above invention, the return line from the end portion side of the connection line for sequentially connecting the coil patterns in series extends along the connection line to the start end side of the connection line. It is characterized by being arranged.

Further, the current sensor according to the present invention is characterized in that a plurality of current sensors described in any one of the above inventions are arranged and connected in series so as to add the induced voltage generated in each current sensor.

Further, the watt hour meter according to the present invention measures the amount of electric energy flowing through the current bar based on the current signal detected by the current sensor and the voltage signal detected by the voltage sensor according to any one of the above inventions. It is characterized by calculating.

According to the present invention, it is possible to provide a current sensor and a watt-hour meter that are easy to manufacture, are not easily affected by an external magnetic field, and have good linearity of current detection characteristics in a wide range.

FIG. 1 is a perspective view showing a schematic configuration of a current sensor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA of the current sensor shown in FIG. FIG. 3 is a sectional view taken along line BB of the current sensor shown in FIG. FIG. 4 is a view taken along the line A of the current sensor shown in FIG. FIG. 5 is an explanatory diagram showing a coil pattern formed in the coil pattern portion of the current sensor shown in FIG. FIG. 6 is an explanatory diagram illustrating two coil pattern surfaces of the coil pattern portion. FIG. 7 is an explanatory diagram for explaining the coil patterns formed on the two coil pattern surfaces of the coil pattern portion and their connection relationships. FIG. 8 is an explanatory diagram illustrating the assembly of the current sensor according to the modified example. FIG. 9 is a diagram showing an arrangement state of the coil pattern portion of the current sensor according to the modified example. FIG. 10 is a perspective view showing a schematic configuration of a current sensor according to a modified example. FIG. 11 is a block diagram showing an example of a watt-hour meter using the current sensor shown in the embodiment. FIG. 12 is a vector diagram between a three-phase current and a three-phase voltage. FIG. 13 is a diagram showing another example of the notch formed in the pedestal portion.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a perspective view showing a schematic configuration of a current sensor 2 according to an embodiment of the present invention. Further, FIG. 2 is a cross-sectional view taken along the line AA of the current sensor 2 shown in FIG. Further, FIG. 3 is a sectional view taken along line BB of the current sensor 2 shown in FIG. Further, FIG. 4 is a view taken along the line A of the current sensor 2 shown in FIG. Further, FIG. 5 is an explanatory diagram showing a coil pattern P1 formed in the coil pattern portion 2b of the current sensor 2 shown in FIG. Further, FIG. 6 is an explanatory diagram for explaining the coil pattern surfaces 2b1 and 2b2 of the coil pattern portion 2b. Further, FIG. 7 is an explanatory diagram for explaining the coil patterns P1 and P1'formed on the coil pattern surface 2b1 which is one surface of the coil pattern portion 2b and the coil pattern surface 2b2 which is the back surface and their connection relationship. .. In FIGS. 1 to 7, the current sensor 2 measures the magnetic field formed around the current bar 1 through which the current flows, and detects the current signal flowing through the current bar 1.

In the current sensor 2, the coil pattern portions 2a to 2d and the pedestal portion 20 for fixing the coil pattern portions 2a to 2d are integrally formed by resin molding. The coil pattern portions 2a to 2d are in a state of being erected perpendicularly to the pedestal portion 20. Further, a notch 21 is formed in the pedestal portion 20, and the current bar 1 is arranged in the notch 21. The notch 21 is formed at a depth at which the axis C at the center of the current bar 1 becomes the center of the arrangement of the coil pattern portions 2a to 2d in a state where the current bar 1 is inserted all the way.

A technique for forming a coil pattern P1 from a metal film on the surface of a resin molded product is generally called MID (Mechatronics Integrated Device), whereby an electric circuit, electrodes, and a pattern are formed on the resin molded product. Specifically, the resin molded product is patterned by laser processing, and a circuit is formed of copper, nickel, gold, etc. by the subsequent plating process. At this time, various resin materials are selected depending on each construction method, reflow conditions for component mounting, and the like. In the present embodiment, for example, a polyamide-based material such as LCP (liquid crystal polymer) or PPA, which has heat resistance and a low coefficient of thermal expansion due to temperature, is used to reduce the influence on the measurement error due to temperature deformation.

The resin material is not limited to these, and can be arbitrarily selected according to the application, such as using a low-grade material that allows temperature influence, for example, a PC or ABS to form a low-cost current sensor 2. You may. In this way, since the parts such as the coil pattern P1 are directly formed on the resin molded product, the three-dimensional resin molding including the coil pattern portions 2a to 2d and the pedestal portion 20 already integrally formed is formed. Parts such as the coil pattern P1 can be placed on the product with high accuracy, and the current sensor 2 can be easily manufactured and assembled.

As shown in FIGS. 1 to 5, in the current sensor 2, two pairs of coil pattern portions 2a, 2c, 2b, and 2d in which the same coil pattern P1 is formed are symmetrical with respect to the axis C of the current bar 1, respectively. Is placed in. The four coil pattern portions 2a to 2d are provided around the current bar 1 at equal angular intervals and at 90 degree intervals around the axis C of the current bar 1. The coil pattern portions 2a to 2d are provided so that the angle θ1 between the coil pattern surface on which the coil pattern P1 is formed and the magnetic flux φ1 to be measured is a right angle.

As shown in FIG. 6, the coil pattern portion 2a has a coil pattern surface 2b1 which is one surface viewed from the direction F1 and a coil pattern surface 2b2 which is a back surface viewed from the direction F2. Coil patterns P1 and P1'are formed, respectively.

As shown in FIG. 7, the two coil patterns P1 and P1'formed on the coil pattern surfaces 2b1 and 2b2 are connected via a via T23 formed of a metal film. Further, the winding direction WA of each coil pattern P1 is such that the induced voltage generated in the coil pattern P1 is added by the magnetic flux φ1 generated by the current flowing through the current bar 1. That is, the winding directions WA of the coil patterns P1 and P1'as viewed from the directions F1 and F2 are opposite directions.

The terminals T21 and T22 of each coil pattern P1 are connected by a connection line TA as shown in FIG. The connection line TA is connected so as to add the induced voltage generated in each coil pattern P1 and P1'of each coil pattern portion 2a to 2d. For example, the terminal T21 on the coil pattern P1 side of the coil pattern portion 2b is connected to the terminal T22 on the coil pattern P1'side of the coil pattern portion 2a, and the terminal T22 on the coil pattern P1'side of the coil pattern portion 2b is a coil pattern. It is connected to the terminal T21 on the coil pattern P1 side of the portion 2c.

As shown in FIGS. 2 and 3, the connecting line TA extending from the terminal TTa (starting end) is connected to the return line TC via a via TB (ending) formed of a metal film. The return line TC is formed along the connection line TA on the opposite surface of the pedestal portion 20. The return line TC is connected to the opposite surface of the pedestal portion 20 via the via TD, and is connected to the terminal TTb. Therefore, the terminals TTa and TTb are formed on the same surface. As a result, the connecting line TA and the return line TC do not go around the current bar 1 and are arranged along the current bar 1, so that the loop region formed by the connecting line TA and the return line TC is small, and this loop is formed. The interlinking magnetic flux is also small, making it less susceptible to the effects of external magnetic fields. As a result, an induced voltage proportional to the magnetic flux φ1 generated by the current flowing through the current bar 1 can be obtained between the terminals TTa and TTb.

As shown in FIG. 2, since the winding directions WA of the coil pattern portions 2b and 2d are opposite to the magnetic flux φ2 of the external magnetic field, the induced voltage due to the magnetic flux φ2 of the external magnetic flux of the coil pattern portions 2b and 2d is It will be countered. On the other hand, the coil pattern portions 2a and 2c are not sensitive to the magnetic flux φ2 of the external magnetic field. As a result, the current sensor 2 is not affected by the magnetic flux φ2 of the external magnetic field.

Similarly, since the winding directions WA of the coil pattern portions 2a and 2c are opposite to the magnetic flux φ3 of the external magnetic field orthogonal to the magnetic flux φ2 of the external magnetic field, the induction by the magnetic flux φ3 of the external magnetic field of the coil pattern portions 2a and 2c. The voltage is canceled. On the other hand, the coil pattern portions 2b and 2d have no sensitivity to the magnetic flux φ3 of the external magnetic field. As a result, the current sensor 2 is not affected by the magnetic flux φ3 of the external magnetic field.

Further, the coil pattern portions 2a to 2d have no sensitivity to the magnetic flux φ4 of the external magnetic field orthogonal to the magnetic fluxes φ2 and φ3 of the external magnetic field. Further, since the return line TC along the connection line TA is provided, the region where the magnetic flux φ4 of the external magnetic field intersects the loop formed by the return line TC along the connection line TA and the connection line TA is small. The induced voltage generated by the magnetic flux φ4 of the external magnetic field can be reduced. Therefore, the current sensor 2 is not easily affected by the magnetic flux φ4 of the external magnetic field.

Therefore, the current sensor 2 has a structure that is not easily affected by the magnetic fluxes φ2, φ3, and φ4 of the external magnetic field in all directions.

According to the embodiment of the present invention, since the pair of coil pattern portions having the same coil pattern formed are arranged symmetrically with respect to the axis of the current bar, the production is easier than that of the Rogowski coil. Since it is not easily affected by an external magnetic field and does not use a magnetic material, it does not become magnetically saturated, and a current sensor with good linearity of current detection characteristics can be realized in a wide range. Further, by forming a coil pattern and a connecting wire connecting each coil on the surface of the resin molded product, the number of parts can be reduced and manufacturing becomes easy.

<Modification example>
In the method of forming a metal film on the resin molded product according to the above embodiment, since the pattern is formed by laser processing, it is necessary to prevent the irradiation of the laser beam from being blocked by other parts in the portion to be patterned. There is. Therefore, in manufacturing, it is preferable that the coil pattern portions 2a to 2d are arranged around the current bar 1 at 90-degree intervals with respect to one current sensor 2. On the other hand, the larger the number of coil pattern portions, the larger the induced voltage can be obtained and the stronger the resistance to disturbance factors such as electromagnetic noise. Therefore, it is desirable to arrange more coil pattern portions.

In this modification, as shown in FIG. 8, the current sensor 3 in which the coil pattern portions are arranged at 90 degree intervals is arranged so as to face the coil pattern portion of the current sensor 2. At this time, as shown in FIG. 9, the coil pattern portions 2a to 2d of the current sensor 2 and the coil pattern portions 3a to 3d of the current sensor 3 are combined so as not to interfere with each other so as to be different from the axis C of the current bar 1. Arrange so that they are at an angle.

As a result, as shown in FIG. 10, the width W1 of the current sensor 4 including the current sensors 2 and 3 can be reduced, and more coil patterns can be arranged in the limited space. For example, the width W1 is the larger value of the width W2 of the coil pattern portions 2a to 2d of the current sensor 2 in the axis C direction and the width W3 of the coil pattern portions 3a to 3d of the current sensor 3 in the axis C direction. ..

Further, the current sensor 2 and the current sensor 3 are connected so that the induced voltage due to the magnetic field generated by the current flowing through the current bar 1 is added. As a result, a larger induced voltage can be obtained as compared with the case where only one current sensor 2 or 3 is used. In this case, the current sensor 4 does not have the same sensitivity to the external magnetic field that causes disturbance as in the case of using one of the current sensors 2 and 3, so that the induced voltage is large and the current sensor 4 is affected by the disturbance due to the external magnetic field. It has a difficult structure.

When the positions of the coil pattern portions 2a to 2d and 3a to 3d interfere with the notch 21, the pair of interfering coil pattern portions are arranged at different angles. Alternatively, as shown in FIG. 13, a notch 31 is formed so that the current bar 1 can be introduced from a position that does not interfere with the coil pattern portions 3a to 3d. The notch 31 of the current sensor 2'is provided, for example, between the coil pattern portions 3a and 3d. When the current bar 1 is introduced into the notch 31, the pedestal portion 20'is inclined with respect to the axis C of the current bar 1 and then perpendicular to the current bar 1.

<Electric energy meter>
FIG. 11 is a block diagram showing an example of a watt-hour meter 200 using the two current sensors 2 (102a, 102b) shown in the embodiment. The current sensors 102a and 102b may be the current sensor 4. The watt-hour meter 200 measures the amount of three-phase power between the power supply SP and the load LD, and is obtained by the two-power wattmeter method. Note that FIG. 12 shows a vector diagram between the three-phase currents IR, IS, IT and the three-phase voltages VR, VS, VT.

As shown in FIG. 11, the electric energy meter 200 has current sensors 102a and 102b, voltage sensors 201a and 201b, electric energy calculation unit 202, and output unit 203 corresponding to the two current sensors 2 shown in the embodiment. .. The current sensor 102a detects an R-phase current signal. The current sensor 102b detects a T-phase current signal. Further, the voltage sensor 201a detects a voltage signal between the R phase and the S phase. The voltage sensor 201b detects a voltage signal between the T phase and the S phase.

The power amount calculation unit 202 multiplies the current signal of the current sensor 102a and the voltage signal of the voltage sensor 201a to generate an instantaneous power signal, obtains the active power smoothed by a low-pass filter, and obtains the active power smoothed by the low-pass filter, and the current of the current sensor 102b. The signal is multiplied by the voltage signal of the voltage sensor 201b to generate an instantaneous power signal, the active power smoothed by a low-pass filter is obtained, and the active power obtained by adding each active power is calculated as the amount of power. The output unit 203 outputs the calculated electric energy as a display output or an external output.

The three-phase power P obtained by the two-power wattmeter method is
P = VRS / IR + VTS / IT
= (VR-VS) / IR + (VT-VS) / IT
= VR / IR + VS / (-IR-IT) + VT / IT
= VR / IR + VS / IS + VT / IT
It is the same as finding the total power of each phase.

Further, each configuration shown in the above-described embodiment and modification is a schematic function, and does not necessarily have to be physically illustrated. That is, the form of distribution / integration of each device and component is not limited to the one shown in the figure, and all or part of them are functionally or physically distributed / integrated in arbitrary units according to various usage conditions. Can be configured.

1 Current bar 2,2', 3,4,102a, 102b Current sensor 2a to 2d, 3a to 3d Coil pattern part 2b1,2b2 Coil pattern surface 20,20'Pedestal part 21,31 Notch 200 Power meter 201a, 201b Voltage sensor 202 Power calculation unit 203 Output unit C-axis F1, F2 direction IR, IS, IT Three-phase current LD load P1, P1'Coil pattern SP power supply T21, T22, TTa, TTb terminal T23, TB, TD Via TA Connection line TC Return line VR, VS, VT Three-phase voltage W1, W2, W3 Width WA Winding direction θ1 Angle φ1 to φ4 Magnetic current

Claims (8)

A current sensor that measures the magnetic field formed around a current bar through which a current flows and detects the current signal flowing through the current bar.
A current sensor characterized in that a resin molded product having a coil pattern formed of a metal film on its surface is arranged so as to cover the current bar. The current sensor according to claim 1, wherein the coil patterns have the same shape and are a pair of coil patterns arranged symmetrically with respect to the axis of the current bar. The current sensor according to claim 2, wherein a plurality of the pair of coil pattern portions on which the pair of coil patterns are formed are arranged. Any one of claims 1 to 3, wherein a connection line connecting the coil patterns in series so as to add an induced voltage generated in the coil pattern is formed on the surface of the resin molded product with a metal film. The current sensor described in 1. The current sensor according to any one of claims 1 to 4, wherein the coil pattern surface on which the coil pattern is formed is perpendicular to the magnetic flux generated by the current bar. Any of claims 1 to 5, wherein the return line from the end portion side of the connection line for sequentially connecting the coil patterns in series is arranged along the connection line to the start end side of the connection line. The current sensor described in one. A plurality of current sensors according to any one of claims 1 to 6 are arranged, and a plurality of current sensors are arranged.
A current sensor characterized in that it is connected in series so as to add the induced voltage generated in each current sensor. An electric energy characteristic of calculating the electric energy flowing through the current bar based on the current signal detected by the current sensor according to any one of claims 1 to 7 and the voltage signal detected by the voltage sensor. Total.

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