JP4965402B2 - Current sensor - Google Patents

Description

  The present invention relates to a current sensor for measuring a current flowing through a branch circuit or the like of a domestic distribution board.

  Generally, as a current sensor for non-contact measurement of the amount of alternating current that is passed through wires such as power transmission / transformation equipment and household distribution boards, there is a through-type current sensor that measures the measured wire by passing it through the sensor. Many are used.

  Such a current sensor is easy to receive an external radio wave of that wavelength when the conductor length including the detection coil for detecting the induced current from the electric wire to be measured is approximately 1/10 or more of the wavelength of the external radio wave. Become. For example, if the conductor length of the current sensor is several tens of centimeters, the current sensor can receive a high-frequency unnecessary external magnetic field of around 100 MHz. In this case, even if the current sensor normally detects such an unnecessary external magnetic field of the high-frequency radio wave with the detection coil, the high-frequency component is removed by the current detection circuit that processes the detection current signal at the subsequent stage, so that the influence is almost not. Absent. However, for example, when a high frequency radio wave is generated in a burst cycle, and there is a component of 50/60 Hz or close to this burst cycle, the radio wave of this burst cycle is substantially envelope-detected by a non-linear part of the current detection circuit. The detected envelope may have a 50/60 Hz component. In this case, the current detection value of the current sensor is equal to the current detection value from the 100 V line (50/60 Hz) of the AC power supply to be measured flowing through the wire to be measured, and the current detection value of 50/60 Hz due to a high frequency unnecessary external magnetic field. Will join. For this reason, the error of the current detection value of the current sensor increases, and the current measurement accuracy may deteriorate.

By the way, in order to suppress the influence by such an unnecessary external magnetic field, a current sensor using a Rogowski coil as an AC current detection coil is known. For example, a plurality of radial lines formed on both front and back surfaces of an insulating substrate are continuously connected by through holes to form a toroidal coil, and the toroidal coil is wound up and doubled into a coil and a rewinding coil. A coil for use is known (see, for example, Patent Document 1). This alternating current detection coil can detect a minute current of alternating current, and the front and back coil shapes are symmetrical to cancel the unnecessary external magnetic field to be detected, thereby improving the current measurement accuracy. In addition, a pattern having the same electric potential is applied to an empty space where the coil pattern of the insulating substrate is not provided, thereby reducing the influence of electrostatic noise and improving noise characteristics. However, since the radial line portion of this coil is not shielded, it may be easily affected by a high-frequency unnecessary external magnetic field.
JP 2007-57494 A

  The present invention has been made to solve the above-described problems, and reduces the influence of an unnecessary external magnetic field in a current sensor having an alternating current detection coil in which an opening for passing a conductor through which a current flows is formed. An object of the present invention is to provide a small current sensor that can further improve the accuracy of current measurement.

In order to achieve the above object, the invention of claim 1 is formed of a conductive foil formed in the insulating substrate with openings for passing through a conductor through which a current flows, and radially formed on both front and back surfaces around the opening. A toroidal coil having a plurality of radial lines and electrically connecting the front and back radial lines respectively at both ends of the radial line is provided, and the toroidal coil is doubled in the winding direction and the rewinding direction. A current sensor comprising an alternating current detection coil formed and continuously connected, the shield part having a nonmagnetic conductor that covers and insulates the surface of the alternating current detection coil, and the shield part A signal processing circuit having a ground that is connected and grounded, and a signal input terminal that is connected to the conductor foil of the detection coil; Connecting the insulating substrate and said shield portion forms a printed circuit board having a multilayer structure, a signal input terminal of the conductive foil and the signal processing circuit of the detection coil, through only the printed circuit board within the multi-layer structure It is characterized by being.

  According to a second aspect of the present invention, in the alternating current detecting coil according to the first aspect, the insulated conductor foils of the printed board are connected by a through-through hole penetrating the printed board in the thickness direction. .

  According to a third aspect of the present invention, in the coil for detecting an alternating current according to the first aspect, the radial lines are formed on any two layers of the conductive foil on the inner layer of the printed circuit board, and the ends of the radial lines of the two layers are formed. The insulating layer between the two layers is penetrated in the thickness direction, the front and back surfaces of the printed board are connected by non-through holes that do not penetrate in the thickness direction, and the shield part is connected to a radial line of the printed board. It is provided in an arbitrary layer outside the formed two layers.

  According to a fourth aspect of the present invention, in the AC current detection coil according to any one of the first to third aspects, the shield portion covers an inner peripheral surface of an opening formed in the insulating substrate of the printed circuit board. It is formed as follows.

  According to the invention of claim 1, since the shield part of the printed circuit board can cover and shield substantially the entire surface of the AC current detecting coil, the shielding effect against unnecessary external magnetic field including high frequency noise is improved. The influence of an unnecessary external magnetic field can be further reduced, and stable and highly accurate current detection can be performed. In addition, since the insulating substrate and the shield portion are integrally formed on the printed board, the thickness can be reduced, the manufacturing process can be simplified, and the manufacturing cost can be reduced. In addition, since the induction magnetic field detected by the alternating current detection coil can be prevented from concentrating on the shield part, it is possible to suppress a decrease in current detection sensitivity.

  According to the second aspect of the present invention, a manufacturing process of a printed circuit board that is normally used can be used for the through hole processing process, so that the manufacturing cost can be reduced.

  According to the invention of claim 3, the end portion of the through hole connecting the radial lines between the two layers does not appear outside through the shield portion on the front and back surfaces of the printed circuit board, and thus is formed in the printed circuit board. The shielding effect of the alternating current detection coil is enhanced, and the influence of an unnecessary external magnetic field can be further reduced.

  According to the fourth aspect of the present invention, it is possible to reduce the unnecessary external magnetic field that enters from the inner peripheral surface of the opening of the printed circuit board, so that the influence of the unnecessary external magnetic field can be further reduced.

  Hereinafter, a current sensor 1 according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 5. 1 to 3, a current sensor 1 according to the present embodiment includes a multilayer printed circuit board 2 and an alternating current detection coil 4 (hereinafter referred to as a detection circuit) formed around an opening 3 formed in the printed circuit board 2. Coil), a shield portion 5 that shields the detection coil 4, and a signal processing circuit 6 that performs signal processing of the detection current of the detection coil 4.

  The printed circuit board 2 has a four-layer structure in which four layers of conductive foils are insulated and laminated by insulating substrates 21, 22, and 23, respectively. The first and fourth conductive foils on the front and back surfaces of the printed circuit board 2 are each made of a metal foil (for example, copper foil) of a nonmagnetic conductor, and these conductive foils cover the printed circuit board 2 from both the front and back surfaces. The shield layers 5a and 5b of the shield part 5 are formed. In addition, the second and third conductive foils 24 and 25 of the inner layer of the printed circuit board 2 are arranged on the front and back of the insulating substrate 22 that insulates them, and constitute the detection coil 4. A signal processing circuit 6 is formed on the front surface side of the printed circuit board 2, and a detection current output of the detection coil 4 is input to the signal processing circuit 6 through a connection line 46. The grounding between the conductive foils of the printed circuit board 2 is performed by through through holes 8 that penetrate both the front and back surfaces of the printed circuit board 2 in the thickness direction.

  The opening 3 is a substantially circular through-hole formed in the printed circuit board 2 for penetrating a measured electric wire (conductor) through which a current flows. Around the opening 3, a detection coil 4 is formed for detecting an alternating current flowing through the measurement target wire passing through the opening 3.

  The detection coil 4 includes a plurality of radial lines 41 formed radially on the conductive foils 24 and 25 on both the front and back surfaces around the opening 3 of the insulating substrate 22, and insulating substrates formed at both ends of the radial lines 41. And a through-hole 7 that penetrates through 22 in the thickness direction. The through hole 7 includes through through holes 7a, 7b, and 7c that penetrate the insulating substrate 22 and penetrate both the front and back surfaces of the printed circuit board 2 in the thickness direction. Through the through-holes 7a, 7b, and 7c, the radial lines 41 on both the front and back surfaces of the insulating substrate 22 are electrically connected to each other at their ends to form a toroidal coil 42. The toroidal coil 42 is formed in a double manner by a winding advance coil 43 in the winding advance direction and a rewinding coil 44 in the rewind direction on the insulating substrate 22, and the winding advance coil 43 and the winding advance coil 43 are continuously connected. Thus, the detection coil 4 is configured. With this detection coil 4, the detection current of the current flowing through the conductor to be measured penetrating the opening 3 is the sum of the induction currents generated in both coils 43 and 44, and an induction current proportional to the number of turns of all the coils is obtained. For the unnecessary external magnetic field, the difference between the induced currents detected by the coils 43 and 44 is detected.

  Further, as shown in FIG. 4, the adjacent radial lines 41 of the winding advance coil 43 and the rewinding coil 44 are connected to each other on the front and back of the insulating substrate 22 so as to avoid contact with each other. More connected. With this connection, the toroidal coil 42 can be formed in a planar manner on the front and back of the insulating substrate 22, and the winding advance coil 43 and the rewinding coil 44 can be formed. The connection portions 45 are provided on the front and back surfaces of the insulating substrate 22 at equal pitch intervals on the substantially concentric circles of the openings 3 on the end side opposite to the openings 3 of the plurality of radial lines 41. 41 has the same shape on the front and back of the insulating substrate 22, and the connecting portions 45 on the front and back also have the same shape. Thereby, the cancellation accuracy of the external magnetic field between the winding advance coil 43 and the rewinding coil 44 is improved, the influence of the external magnetic field is reduced, and the current measurement accuracy is increased.

  The detection current signal detected by the detection coil 4 is transmitted to the signal processing circuit 6 through the connection line 46, amplified and processed by the signal processing circuit 6, and output as a measured current value. . Since this signal processing circuit 6 is integrated on the same printed circuit board 2 with the detection coil 4, it can be made small and compact. Further, since the detection coil 4 and the signal processing circuit 6 are arranged close to each other, the connection line 46 is shortened, and it is difficult to receive an unnecessary external magnetic field at the connection line 46.

  Further, as shown in FIG. 5, the radial lines 41 and the connection portions 45 of the detection coil 4 formed on the conductor foils 24 and 25 of the printed circuit board 2 penetrate the shield layers 5 a and 5 b on the front and back surfaces of the printed circuit board 2. Are connected by through-holes 7a, 7b, 7 to form a detection coil 4. Further, the shield layers 5 a and 5 b of the shield part 5 are grounded to each other through through holes 8 penetrating the front and back surfaces of the printed circuit board 2. The detection current detected by the detection coil 4 is connected to the printed circuit board 2 via the connection line 46 connected to the output end of the detection coil 4 in the printed circuit board 2 and the through-through hole 11 connected to the connection line 46. 2 is input to the signal processing circuit 6. Therefore, the current measured value can be taken out from the signal processing circuit 6 by detecting the current flowing through the conductor 20 passing through the opening 3 of the printed circuit board 2 by the detection coil 4. The ground of the signal processing circuit 6 and the shield part 5 are connected to each other and grounded.

Here, the detection coil 4 formed on the printed substrate 2 is covered with a shield section 5 made of conductive foil of the first and fourth layers of the front and back surfaces of the printed circuit board 2 (5a, 5b). The shield part 5 is formed on the same printed circuit board 2 as the detection coil 4, and the front and back surfaces of the detection coil 4 are insulated by insulating substrates 21 and 23, and the external sides of the insulating substrates 21 and 23 are separated from them. It is possible to cover the two in close contact with each other. Thereby, since the surface of the radiation line 41 of the detection coil 4 can be shielded uniformly, the shielding effect on the radiation line 41 is increased, and an unnecessary external magnetic field including high-frequency noise received by the radiation line 41 is suppressed. Can do. Further, since the shield portion 5 is grounded to the ground of the signal processing circuit 6, the ground surface of the signal processing circuit 6 is widened and the circuit operation is stabilized.

  As described above, according to the current sensor 1 of the present embodiment, the shield portion 5 formed on the printed circuit board 2 can cover and shield substantially the entire surface of the detection coil 4, so that the radial line 41 and the like can be provided. This improves the shielding effect against unnecessary external magnetic fields including high-frequency noise received at, can further reduce the influence of unnecessary external magnetic fields, and can perform stable and highly accurate current detection. Further, since the insulating substrates 21 to 23 and the shield part 5 are integrally formed on the multilayered printed board 2, the thickness can be reduced, the manufacturing process can be simplified, and the manufacturing cost can be reduced. In addition, the shield by the shield part 5 having a non-magnetic conductor can eliminate the induction magnetic field from the current flowing through the conductor 20 detected by the detection coil from concentrating on the shield part 5 and suppress the decrease in current detection sensitivity. can do.

  Further, the through holes penetrating the printed circuit board 2 are formed as through holes penetrating both the front and back surfaces of the printed circuit board 2 as through through holes 7a, 7b, 7c, 8, and 11, so that all the through holes Since the manufacturing process of the printed circuit board 2 normally used can be used for the processing process, the manufacturing cost can be further reduced.

  Next, a current sensor 1 according to a second embodiment of the present invention will be described with reference to FIGS. In the current sensor 1 of the present embodiment, the connection of the radial lines 41 on both the front and back surfaces of the insulating substrate 22 penetrates the insulating substrate 22 in the thickness direction, and does not penetrate the front and back surfaces of the printed board 2 in the thickness direction. It is different in that it is connected by through holes 7d, 7e, and 7f, and other configurations are the same as those in the above embodiment.

  In the current sensor 1 of the present embodiment, the through-hole 7 to which the radial lines 41 on both the front and back surfaces of the insulating substrate 22 are connected penetrates only in the thickness direction of the insulating substrate 22 and is formed on both the front and back surfaces of the printed circuit board 2. The non-through-through holes 7d, 7e, 7f that do not penetrate in the thickness direction are formed. For this reason, the shield part 5 (5a, 5b) is blocked by the through holes corresponding to the non-through-through holes 7d, 7e, 7f, and the electromagnetic shielding property of the shield part 5 is improved.

  Thus, according to the current sensor 1 of the present embodiment, the detection coil 1 does not penetrate the radial lines 41 between the two layers of the conductor foils 24 and 25 through the non-through-through holes 7d and 7e that do not penetrate both the front and back surfaces of the printed circuit board 2. Since they are connected by 7f, both end portions of the non-through-through holes 7d, 7e, 7f do not appear on the surface of the printed circuit board 2, and the detection coil 4 is more strongly shielded from the external space on the front and back surfaces. Thereby, the shielding effect with respect to the unnecessary external magnetic field by the shield part 5 can further be improved, and the current measurement accuracy can be further enhanced.

  Next, a current sensor 1 according to a third embodiment of the present invention will be described with reference to FIGS. The current sensor 1 of the present embodiment is formed so that the shield portion 5 covers the inner peripheral surface 12 of the opening 3 of the printed circuit board 2, and other configurations are the same as those of the first embodiment. .

  According to the current sensor 1 of the present embodiment, the inner peripheral surface 12 of the opening 3 of the printed circuit board 2 is shielded by the shield portion 5 (5c), so that the detection coil 4 can be detected from the inner peripheral surface 12 of the printed circuit board 2. Unnecessary external magnetic field entering can be reduced. Thereby, the influence of an unnecessary external magnetic field can be further suppressed, and the current measurement accuracy can be further increased.

  Next, a current sensor 1 according to a fourth embodiment of the present invention will be described with reference to FIG. The current sensor 1 of the present embodiment includes a shield case 30 that covers the current sensor 1, and other configurations are the same as those of the first embodiment.

  The shield case 30 includes a concave housing 31 formed by molding an insulating resin or the like that accommodates the printed circuit board 2, a lid portion 32 that serves as a lid for the housing 31, and an opening that is substantially concentric with the opening 3 of the printed circuit board 2. And an opening 3a. Moreover, each inner surface of the housing 31 and the cover part 32 is covered with shield surfaces 31a and 32a coated or plated with a nonmagnetic conductor member, respectively. The through opening 3 a is an opening that penetrates the shield case 30 through the housing 31 and the lid portion 32. The current sensor 1 can detect the current flowing through the conductor under measurement 20 while being covered with the shield case 30 by passing the conductor under measurement 20 through the through opening 3a. Thus, since the current sensor 1 is covered with the shield case 30, the degree of sealing of electromagnetic shielding is improved, the shielding effect against unnecessary external magnetic fields is increased, and the current measurement accuracy can be further increased.

  In addition, this invention is not limited to the structure of said various embodiment, A various deformation | transformation is possible suitably in the range which does not change the meaning of invention. In the various embodiments described above, the case where the current sensor is formed using a printed circuit board having a multilayer structure of four layers has been described. However, the current sensor may be formed using a printed circuit board having a multilayer structure of four layers or more.

1 is a perspective view of a current sensor according to a first embodiment of the present invention. The disassembled perspective view of the said current sensor. The top view of the said current sensor. The perspective view of the coil for an alternating current detection of the said current sensor. X1-X1 sectional view taken on the line of FIG. The perspective view of the current sensor which concerns on the 2nd Embodiment of this invention. The disassembled perspective view of the said current sensor. The top view of the said current sensor. X2-X2 line sectional drawing of the said FIG. The top view of the current sensor which concerns on the 3rd Embodiment of this invention. X3-X3 line sectional drawing of the said FIG. Sectional drawing of the current sensor which concerns on the 4th Embodiment of this invention.

Explanation of symbols

1 Coil for detecting AC current 2 Printed circuit board (insulating board)
3 Opening 4 AC current detection coil 5, 5a, 5b Shield part (conductor foil)
7 through-hole 7a, 7b, 7c, 8 through-through hole 7d, 7e, 7f non-through-hole 12 inner peripheral surface 20 electric wire (conductor)
21, 22, 23 Insulating substrate 24, 25 Conductor foil 41 Radial line 42 Toroidal coil 43 Winding advance coil 44 Rewinding coil

Claims (4)

An opening for penetrating a conductor through which a current flows is formed in an insulating substrate, and has a plurality of radial lines made of conductive foil formed radially on both front and back sides of the opening, and both ends of the radial line And a toroidal coil for continuously connecting the radial lines on the front and back sides, and an alternating current detecting coil formed by continuously connecting the toroidal coil in a winding direction and a rewinding direction. A current sensor comprising:
A shield part having a nonmagnetic conductor covering the surface of the alternating current detection coil while insulating;
A signal processing circuit having a ground connected to the shield part and grounded, and a signal input terminal connected to a conductor foil of the detection coil;
The insulating substrate and the shield portion form a multilayer printed circuit board, and the conductive foil of the detection coil and the signal input terminal of the signal processing circuit pass only inside the multilayer printed circuit board. A current sensor which is connected .   2. The current sensor according to claim 1, wherein the insulated conductor foils of the printed circuit board are connected by a through-through hole penetrating the printed circuit board in a thickness direction. The radial lines are formed in any two layers of the conductive foil on the inner layer of the printed board, and the ends of the two layers of radial lines penetrate the insulating board between the two layers in the thickness direction, and the printed board Connect both front and back sides of the through-holes that do not penetrate in the thickness direction.
The current sensor according to claim 1, wherein the shield portion is provided in an arbitrary layer outside the two layers where the radial lines of the printed circuit board are formed.   4. The current sensor according to claim 1, wherein the shield part is formed so as to cover an inner peripheral surface of an opening formed in an insulating substrate of the printed circuit board. 5. .

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