JP2019152558A - Current sensor and voltmeter - Google Patents

Abstract

To provide a current sensor and a voltmeter which can measure an accurate current in a wide current measurement range at low cost even when the current sensor is arranged in a small space.SOLUTION: A current sensor 1 includes: a current bar 5 in which a current to be detected flows; a magnetism collecting core 2 penetrating the current bar 5, the magnetism collecting core having a void 3; and a substrate 4 having a magnetism detecting element in the void 3, and the current sensor detects a current flowing in the current bar 5 on the basis of the result of magnetism detection by the magnetism detection element. The current bar 5 is formed by sequentially connecting three partial current bars 6, 7, and 8, and the partial current bars 6, 7, and 8 surround the void 3 from three directions.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a current sensor and a watt hour meter capable of performing current measurement with high accuracy in a low current and wide current measurement range even when the space where the current sensor is disposed is narrow.

  Conventionally, current sensors that have been used include current transformers (current transformers: CT), configurations in which magnetoelectric transducers such as Hall elements are arranged in the gap portion of the magnetic flux collecting core, and in the gap portion of the magnetic flux collecting core, There are configurations having an element in which a coil pattern is formed on a wound coil or a dielectric substrate. In particular, the method of arranging a magnetoelectric conversion element such as a hall element or a coil pattern on the substrate in the gap portion of the magnetic flux collecting core is electrically separated from the circuit through which the primary current that is the measurement target flows. Therefore, it is excellent in that the current can be accurately measured without affecting the circuit on the primary current side. Furthermore, the method of arranging the elements in which the coil pattern is formed has the characteristics that the linearity and temperature characteristics are excellent, the number of parts is small, and the manufacturing is easy (see Patent Document 1).

  In the current sensor described in Patent Document 1, a current bar is passed through a central opening of an annular magnetic collecting core, and a substrate on which a coil pattern is applied is arranged in a 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 flux collecting core. When the current is a periodic current, the magnetic flux generated according to the cycle 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 for the current flowing through the current bar.

JP 2010-48755 A

  By the way, in the current sensor in which the magnetoelectric conversion element is disposed in the gap portion of the magnetic flux collecting core, the magnetic flux generated in the gap portion is determined by the magnetic characteristics of the magnetic flux collecting core and the shape of the gap portion. In this current sensor, although the linearity can be improved relatively by setting the gap width to several mm, the linearity may be deteriorated due to the non-linearity with respect to the magnetic field of the magnetic material used in the magnetic collecting core. . Specifically, when a large current flows through the current bar, the magnetic permeability of the magnetic material used in the magnetic collecting core decreases due to magnetic saturation, and the magnetic flux generated in the gap portion also decreases accordingly. The magnetic flux generated with respect to the current is not ideally proportional, and the linearity deteriorates. In general, the magnetic permeability of the magnetic material is the largest in a predetermined magnetic field depending on the material, and the initial permeability is smaller than the maximum permeability. Therefore, even when a small current flows through the current bar, the magnetic flux generated due to the low permeability is lowered, the magnetic flux generated with respect to the measurement current is not in an ideal proportional relationship, and the linearity is deteriorated.

  Here, in the above current sensor, due to the limitation of the space where the current sensor is arranged, the current bar may be bent, and magnetic saturation is likely to occur in a part of the magnetic flux collecting core surrounded by the current bar. The linearity sometimes deteriorated.

  Therefore, in order to suppress the above-described magnetic saturation, it is conceivable to use a magnetic flux collecting core made of a material having a high saturation magnetic flux density. However, a material having a high saturation magnetic flux density is more expensive than a material having a low saturation magnetic flux density. There's a problem.

  The present invention has been made in view of the above, and a current sensor capable of accurately performing current measurement at a low cost and in a wide current measurement range even when a space where the current sensor is disposed is narrow, and The purpose is to provide a power meter.

  In order to solve the above-described problems and achieve the object, a current sensor according to the present invention includes a current bar through which a current to be detected flows, and a magnetic flux collecting core in which the current bar penetrates and at least one air gap is provided. And a substrate having one or more magnetic detection elements provided in the one or more gaps, and detecting a current flowing through the current bar based on a magnetic detection result detected by the one or more magnetic detection elements The current bar is arranged so as to surround one of the one or more gaps from three directions.

  In the current sensor according to the present invention, in the above invention, the current bar is a series of partial current bars in which three partial current bars are sequentially coupled, and each partial current bar has the one or more gaps. It arrange | positions so that the said one said space | gap may be enclosed from three directions.

  The current sensor according to the present invention is characterized in that, in the above invention, the current bar that penetrates the magnetic flux collecting core penetrates perpendicularly to the magnetic flux collecting core, and the penetrating portion has a linear shape.

  The current sensor according to the present invention is characterized in that, in the above-described invention, the current bar that penetrates the magnetism collecting core penetrates the center of the magnetism collecting core.

  The current sensor according to the present invention is characterized in that, in the above invention, a plane surrounded by an axis of a current bar surrounding the gap from three directions is arranged to pass through the gap.

  The current sensor according to the present invention is characterized in that, in the above invention, the magnetic detection element is one or more coil patterns formed on the substrate.

  In addition, the watt hour meter according to the present invention is configured to calculate the amount of power flowing through the current bar based on the current signal detected by the current sensor described in any one of the above inventions and the voltage signal detected by the voltage sensor. It is characterized by calculating.

  According to the present invention, each partial current bar of a series of partial current bars in which three partial current bars are sequentially coupled has one said one of the one or more gaps formed in the magnetic flux collecting core from three directions. Since it is arranged so as to surround, the portion with high magnetic flux density generated by the partial current bar other than the partial current bar that penetrates the magnetic collecting core becomes the portion of the gap with low magnetic permeability, and the magnetic collecting core is less likely to be magnetically saturated. . As a result, in the present invention, even when the space where the current sensor is arranged is narrow, current measurement can be performed with high accuracy in a low current and wide current measurement range.

FIG. 1 is a perspective view showing a configuration of a current sensor according to an embodiment of the present invention. 2 is a side view of the current sensor shown in FIG. 1 as viewed from the X direction. FIG. 3 is a diagram illustrating an example of the magnetic detection element disposed in the gap. FIG. 4 is a diagram showing a state of magnetic flux generated by the current flowing through the partial current bars arranged in parallel. FIG. 5 is a diagram showing the relationship between the detection current detected by the magnetic detection element and the current flowing through the current bar. FIG. 6 is a perspective view showing an example of a current sensor having a different arrangement of current bars. FIG. 7 is a view of another example of the current sensor having a different arrangement of current bars as viewed from the X direction. FIG. 8 is a perspective view showing an example of the arrangement of current bars when two air gaps and two magnetic detection elements arranged in the air gap are provided. FIG. 9 is a view of the current sensor shown in FIG. 8 as viewed from the X direction. FIG. 10 is a diagram illustrating an example of the arrangement of current bars when the thickness of the current bar exceeds the width of the gap. FIG. 11 is a block diagram showing an example of a watt hour meter using the current sensor shown in FIG. FIG. 12 is a vector diagram between a three-phase current and a three-phase voltage.

  DESCRIPTION OF EMBODIMENTS 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 configuration of a current sensor 1 according to an embodiment of the present invention. FIG. 2 is a side view of the current sensor 1 shown in FIG. 1 as viewed from the X direction. FIG. 3 is a plan view showing an example of the substrate 4 interposed in the gap 3 shown in FIG. As shown in FIGS. 1 to 3, the current sensor 1 includes a magnetism collecting core 2 formed so as to surround a current bar 5 through which an electric current flows, and a magnetism that performs magnetic detection via a gap 3 in the magnetism collecting core 2. A detection element 10 is provided and has a substrate 4 that detects a current signal flowing in the current bar 5.

  The current bar 5 is a series of partial current bars in which three partial current bars 6, 7, and 8 are sequentially coupled, and each partial current bar 6, 7, and 8 passes through the gap 3 in the X direction, the Y direction, − It arrange | positions so that it may surround from three directions of X direction. Since the current bar 5 is arranged in the + Y direction of the magnetic flux collecting core 2 and is not arranged in the −Y direction of the magnetic flux collecting core 2, the arrangement space of the current sensor 1 can be reduced.

  The partial current bar 7 penetrating through the central opening 2a of the magnetic flux collecting core 2 penetrates in the X direction perpendicular to the magnetic flux collecting core 2, and the partial current bar 7 at the penetrating portion has a linear shape. Further, the axis C <b> 2 of the partial current bar 7 that passes through the central opening 2 a of the magnetic flux collecting core 2 passes through the central axis C of the magnetic flux collecting core 2. Thereby, the magnetic flux generated by the current flowing through the partial current bar 7 is efficiently formed in the magnetic flux collecting core 2. The plane S surrounded by the axes C1, C2, C3 of the partial current bars 6, 7, 8 is arranged so as to pass through the gap space E3 of the gap 3.

  As shown in FIG. 3, the magnetic detection element 10 is provided on the substrate 4, and the substrate 4 is disposed in the gap 3. The magnetic detection element 10 is a coil pattern 21 formed on the substrate 4. The coil pattern 21 is disposed in the gap space E3 of the gap 3. The coil pattern 21 detects a magnetic flux change in the air gap 3 as an induced voltage. In FIG. 3, the coil pattern 21 is formed by two coil patterns that are wound in the same direction by right-hand winding in the drawing and are arranged vertically. One coil pattern arranged in the upper part and another one coil pattern arranged in the lower part and formed inside the substrate 4 are connected by a via 22a. The coil pattern 21 preferably has a larger number of coil patterns because the magnetic detection sensitivity increases when the inductance is increased. The terminals 22b and 22c of the coil pattern 21 are connected to terminals 22d and 22e formed in regions not covered by the gap 3 via connection lines 23a and 23b, respectively. The terminals 22b, 22c, 22d, and 22e are vias, and the connection lines 23a and 23b are formed inside the substrate 4.

  A signal processing circuit (not shown) may be provided in the substrate 4. The signal processing circuit is connected to the magnetic detection element 10 via the terminals 22 d and 22 e outside the gap 3 of the substrate 4. The signal processing circuit includes, for example, a filter circuit, an amplifier circuit, and an output circuit (not shown). The filter circuit is a low-pass filter, removes high frequency components from the current signal output from the magnetic detection element 10, and transmits commercial frequency components of 50 Hz and 60 Hz flowing through the current bar 5. The amplifier circuit amplifies the current signal transmitted through the filter circuit. The output circuit outputs the current signal amplified by the amplifier circuit to the outside.

  FIG. 4 is a diagram showing a state of magnetic flux generated by currents flowing through the partial current bars 6 and 8 arranged in parallel. As shown in FIG. 4, the magnetic fluxes generated by the partial current bars 6 and 8 are combined between parallel lines through which currents in different directions flow, and a region E having a high magnetic flux density is formed between the partial current bars 6 and 8. Is done. In this embodiment, the partial current bar is such that the plane S surrounded by the axes C1, C2, and C3 of the partial current bars 6, 7, and 8 passes through the gap space E3 so that the region E becomes the gap space E3. 6, 7, 8 are arranged.

  When the region E becomes a core portion other than the air gap 3 of the magnetic flux collecting core 2, the core portion is magnetically saturated. In the present embodiment, the region E becomes the air gap space E3, and the air forming the air gap space E3 Since the magnetic permeability is low, magnetic saturation is difficult.

  FIG. 5 is a diagram showing the relationship of the detection current i detected by the magnetic detection element 10 with respect to the current I flowing through the current bar 5. As shown in FIG. 5, when the detected current i exceeds the current Is flowing through the current bar 5 where the magnetic collecting core 2 is magnetically saturated, the detected current i is also saturated with the detected current is, and the current measurement range is narrowed. However, in the present embodiment, since the region E having a high magnetic flux density formed by the current bar 5 becomes the gap space E3, the influence of magnetic saturation of the magnetic flux collecting core 2 is suppressed, and detection of the current I flowing through the current bar 5 is detected. The measurement range with high linearity of the current i can be maintained in an expanded state.

  In FIG. 1, the partial current bar 7 passes through the central opening 2 a of the magnetic collecting core 2. However, the present invention is not limited to this, and the partial current bar 6 is connected to the magnetic collecting core 2 as shown in FIG. 6. It is good also as the current sensor 1a which penetrates the center opening 2a. Thereby, arrangement | positioning of the electric current bar 5 with respect to the magnetic collection core 2 can be performed flexibly. The partial current bar 8 may pass through the central opening 2 a of the magnetic flux collecting core 2. In this case, the current bar 5 is arranged in the X direction with respect to the magnetic core 2.

  Further, as in the current sensor 1 b shown in FIG. 7, when the gap 3 is arranged in the −Z direction as compared with the gap 3 of the current sensor 1 shown in FIG. 1, the partial current bars 6, 7, 8 are arranged. The partial current bars 6 and 8 are arranged so that the plane S surrounded by the axes C1, C2 and C3 is inclined in the −Z direction and passes through the gap space E3.

  Further, in the current sensor 1 shown in FIG. 1, one air gap 3 is provided in the magnetic flux collecting core 2, and one substrate 4 is disposed in the air gap 3, but two or more air gaps 3 are provided in the magnetic flux collecting core 2. The current may be measured by providing the substrate 4 in each gap 3. For example, as shown in FIG. 8 and FIG. 9, two current gaps 3a and 3b may be provided in the magnetic flux collecting core 2, and substrates 4a and 4b may be provided in the air gaps 3a and 3b, respectively, to measure current. In this case, the partial current bars 6, 7, and 8 of the current bar 5 are arranged so as to surround any one of the gap spaces E3, for example, the gap space E3 of the gap 3b from three directions.

  Further, as shown in FIG. 10, the thickness W <b> 2 of the current bar 5 (partial current bars 6, 7, 8) may exceed the width W <b> 1 of the gap 3. In this case, the partial current bars 6, 7, and 8 are arranged so that the plane S surrounded by the axes C1, C2, and C3 of the partial current bars 6, 7, and 8 passes through the gap space E3. This is because the magnetic saturation of the magnetic flux collecting core 2 can be suppressed by setting the region E where the magnetic flux is concentrated as the gap space E3.

  In the above embodiment, each of the partial current bars 6, 7, 8 has a linear shape, but the linear portion may be only a portion that passes through the central opening 2 a of the magnetic flux collecting core 2. For example, the coupling portions of the partial current bars 6 and 7 and the coupling portions of the partial current bars 7 and 8 shown in FIG. 1 may be curved in an arc shape or may be bent in multiple stages. Furthermore, the partial current bar 7 shown in FIG. 6 may be a U-shaped current bar 5 that is convex in the X direction.

  The magnetic detection element 10 is an example of a magnetoelectric conversion element, and may be, for example, a Hall element in addition to a coil element or a coil pattern.

  In the present embodiment, each partial current bar 6, 7, 8 of a series of partial current bars in which the three partial current bars 6, 7, 8 are sequentially coupled has one or more gaps formed in the magnetic core 2. Since one gap 3, 3 a, 3 b of 3, 3 a, 3 b is arranged so as to surround from three directions, the magnetic flux density generated by the partial current bar other than the partial current bar penetrating the magnetic flux collecting core 2 is high. The part becomes the part of the gaps 3, 3a, 3b having a low magnetic permeability, and the magnetic flux collecting core 2 is hardly magnetically saturated. As a result, in the embodiment, even if the space where the current sensors 1, 1a, 1b, 1c, and 1d are arranged is narrow, current measurement can be performed with high accuracy in a low current and wide current measurement range.

  The current bar 5 is formed such that one partial current bar passes through the central opening 2a of the magnetism collecting core 2 and the tip side is bent or bent back. The current sensors 1 and 1a to 1d can be easily manufactured because they can be easily inserted from the gap 3 of the magnetic flux collecting core 2.

(Application example: electricity meter)
FIG. 11 is a block diagram showing an example of a watt-hour meter 200 using the current sensor shown in the above embodiment. This watt-hour meter 200 measures the three-phase power amount between the power source SP and the load LD, and is obtained by the two-watt meter method. FIG. 12 shows a vector diagram between the three-phase currents IR, IS, IT and the three-phase voltages VR, VS, VT.

  As illustrated in FIG. 11, the watt-hour meter 200 includes current sensors 100 a and 100 b, voltage sensors 201 a and 201 b, a power amount calculation unit 202, and an output unit 203 corresponding to the current sensors described in the embodiment. The current sensor 100a detects an R-phase current signal. The current sensor 100b detects a T-phase current signal. 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 generates an instantaneous power signal by multiplying the current signal of the current sensor 100a and the voltage signal of the voltage sensor 201a, obtains effective power obtained by smoothing the instantaneous power signal with a low-pass filter, and current of the current sensor 100b. The signal is multiplied by the voltage signal of the voltage sensor 201b to generate an instantaneous power signal, and the effective power obtained by smoothing the instantaneous power signal is obtained, and the effective power obtained by adding the effective powers is calculated as the amount of power. The output unit 203 displays or outputs the calculated power amount.

Note that the three-phase power P obtained by the two-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
This is the same as obtaining the total power of each phase.

  In addition, each configuration illustrated in the above-described embodiment and application examples is functionally schematic and does not necessarily need to be physically configured as 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 a part thereof is functionally / physically distributed / integrated in arbitrary units according to various usage conditions. Can be configured.

1, 1a, 1b, 100a, 100b Current sensor 2 Magnetic flux collecting core 2a Center opening 3, 3a, 3b Air gap 4, 4a, 4b Substrate 5 Current bar 6, 7, 8 Partial current bar 10 Magnetic detection element 21 Coil pattern 22a Via 22b, 22c, 22d, 22e Terminals 23a, 23b Connection line 200 Energy meter 201a, 201b Voltage sensor 202 Electric energy calculation unit 203 Output unit C Central axis C1, C2, C3 axis E region E3 Gap space i Detected current I Current S Plane W1 Width W2 Thickness

Claims (7)

A current bar through which a current to be detected flows, a magnetic flux collecting core that penetrates the current bar and is provided with one or more air gaps, and a substrate having one or more magnetic detection elements provided in the one or more air gaps. A current sensor for detecting a current flowing through the current bar according to a magnetic detection result detected by the one or more magnetic detection elements,
The current bar is disposed so as to surround one of the one or more gaps from three directions.   The current bar is a series of partial current bars in which three partial current bars are sequentially coupled, and each partial current bar is disposed so as to surround one of the one or more gaps from three directions. The current sensor according to claim 1.   3. The current sensor according to claim 1, wherein the current bar penetrating the magnetism collecting core penetrates perpendicularly to the magnetism collecting core, and the penetrating portion has a linear shape.   The current sensor according to any one of claims 1 to 3, wherein a current bar passing through the magnetic flux collecting core passes through a center of the magnetic flux collecting core.   5. The current sensor according to claim 1, wherein a plane surrounded by an axis of a current bar surrounding the gap from three directions is arranged to pass through the gap.   The current sensor according to claim 1, wherein the magnetic detection element is one or more coil patterns formed on the substrate.   The amount of power flowing through the current bar is calculated based on the current signal detected by the current sensor according to any one of claims 1 to 6 and the voltage signal detected by the voltage sensor. Total.

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