JP4284579B2 - Current detection method, current detection device, and measuring instrument equipped with current detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a current detection method, a current detection device, and a measurement device including the current detection device, and more particularly, a current detection method, a current detection device, and a measurement device including the current detection device that detect current using a shunt resistor. Regarding improvement.
[0002]
[Prior art]
Conventionally, current detection using a shunt resistor is performed by passing a current for measuring the voltage / current to be measured through the shunt resistor, and measuring the voltage / current to be measured by measuring a potential difference between both ends of the shunt resistor. Doing is a widely used measurement technique.
[0003]
As shown in FIG. 4, a measuring instrument equipped with such a current detection unit detects a current by inputting a measurement current from both ends of the measurement unit 30 having a load for passing a voltage / current to be measured and the load. Current detection unit 40. Other configurations are omitted.
[0004]
The current detection unit 40 is configured to detect a current using a shunt resistor 43 as a resistor, and outputs a current input terminal 41a that inputs a measurement current Iin and an output current Iout that flows through the shunt resistor 43. An output terminal 41b, a shunt mold resistor 44 formed by molding a shunt resistor 43 through which a measurement current Iin input from the current input terminal 41a is molded, and a shunt resistor between the current input terminal 41a and the current output terminal 41b. The input conductor 47a and the output conductor 47b are electrically connected to the connection lines 45a and 45b connected to both ends of the terminal 43, respectively.
[0005]
The input conductor 47a and the output conductor 47b are each configured by a plate member, and the input conductor 47a has a configuration in which the connection line 45a and the current input terminal 41a are electrically connected. The conductor 47b has a configuration in which the connection line 45b and the current output terminal 41b are electrically connected.
[0006]
The shunt mold resistor 44 is arranged on the heat sink 46 in order to release heat generated from the molded shunt resistor 43.
[0007]
The current detection unit 40 of the measuring device having such a configuration is configured such that the measurement current Iin input from the external power source (not shown) input to the measurement unit 30 to the current input terminal 41a is shunted via the input conductor 47a. The current flows to the resistor 43 and flows to the current output terminal 41b as the measurement current Iout. By detecting the potential difference between both ends of the shunt resistor 43 in this state, the current / voltage flowing through the measurement unit 30 can be measured.
[0008]
[Problems to be solved by the invention]
However, in the conventional current detection unit as described above, a phenomenon occurs in which heat and a magnetic field are generated from the shunt resistor 43 itself by causing the measurement current Iin to flow through the shunt resistor 43. This phenomenon increases as the power consumption in the shunt resistor 43 and the input and output conductors 47a and 47b increases, and this phenomenon is particularly caused when measuring a large current. There is a problem that it affects the measurement, more or less.
[0009]
Specifically, the heat generation of the shunt resistor 43 changes the specific resistance value of the shunt resistor 43 itself, which causes an error factor in current measurement. Further, the heat generation of the input and output conductors 47a and 47b itself not only prevents the heat dissipation of the shunt resistor 43 by the heat sink 45 but also heats the shunt resistor 43 itself, so that the heat generation of the shunt resistor 43 itself is the same. It becomes an error factor of current measurement.
[0010]
Furthermore, the generation of a magnetic field around the shunt resistor 43 causes an induced current in the shunt resistor 43, and thus causes an error factor in current measurement, similar to heat generation.
[0011]
In addition, according to the configuration of the conventional current detection unit 40 described above, the heat sink 46 is provided to release the heat generated in the shunt resistor 43 in order to reduce the influence of heat generation that causes an error in current measurement. Since the shunt resistor 43 is covered with the shunt mold 42, it cannot be directly brought into contact with the heat sink 46 to dissipate heat. That is, since the heat sink 46 performs heat dissipation in a state where a certain amount of thermal resistance exists between the shunt resistor 43 and the heat sink 46, it is difficult to efficiently suppress the temperature rise of the shunt resistor 43. Is also present.
[0012]
Therefore, the present invention has been made to solve these problems. In the current detection method using a shunt resistor, the heat radiation effect and the magnetic field shielding effect of a conductor provided in the vicinity of the shunt resistor are increased. It is an object of the present invention to provide a current detection method, a current detection device, and a measurement device including the current detection device that can reduce the influence of an error factor.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, a current detection method, a current detection device, and a measuring instrument equipped with the current detection device according to the present invention have the following method and configuration.
[0014]
(1) A shunt mold resistor having a molded shunt resistor is disposed on a heat sink for heat dissipation, and each of the two connection lines connected to both ends of the shunt resistor and a current that allows a desired measurement current to flow. Electrically connecting each of the input conductor and / or output conductor having heat dissipation means and / or magnetic field shielding means between the input terminal and the current output terminal ;
The input conductor and / or output conductor having the heat radiation means and / or the magnetic field shielding means are formed by forming a single plate member in a U shape and overlapping the plate member formed in the U shape in an insulated state. The current detection method characterized by the above-mentioned .
(2) The input conductor formed in the U-shape is formed larger than the output conductor formed in the U-shape, and the output conductor is the same inside the U-shape of the input conductor. The current detection method according to (1) , wherein the current detection method is arranged so as to overlap in a direction.
[0015]
(3) a current input terminal and a current output terminal for supplying a measurement current to be detected, a shunt mold resistor connected between the current input terminal and the current output terminal and having a molded shunt resistor, and the shunt A heat sink for dissipating heat by disposing a mold resistor; and an input conductor and an output conductor electrically connected between each of the current input terminal and the current output terminal and both ends of the shunt resistor. In the current detection device, the input conductor and / or the output conductor include a heat radiating means and / or a magnetic field shielding means ,
The input conductor and / or output conductor provided with the heat dissipation means and / or the magnetic field shielding means are formed by forming a single plate member in a U shape and overlapping the plate members formed in the U shape in an insulated state. A current detection device characterized by that .
(4) The input conductor formed in the U-shape is formed larger than the output conductor formed in the U-shape, and the output conductor is the same inside the U-shape of the input conductor. The current detection device according to (3) , wherein the current detection device is arranged so as to overlap in a direction.
[0016]
(5) A shunt mold resistor having a current transformer that generates a measurement current of a secondary current on the secondary side according to the current to be measured input to the primary side, and a molded shunt resistor that passes the secondary current An input conductor and an output electrically connected between each of the secondary ends of the current transformer and both ends of the shunt resistor. In the current detection device having a conductor, the input conductor and / or the output conductor is provided with a heat radiating means and / or a magnetic field shielding means ,
The input conductor and / or output conductor provided with the heat dissipation means and / or the magnetic field shielding means are formed by forming a single plate member in a U shape and overlapping the plate members formed in the U shape in an insulated state. A current detection device characterized by that .
(6) The input conductor formed in the U-shape is formed larger than the output conductor formed in the U-shape, and the output conductor is the same inside the U-shape of the input conductor. The current detection device according to (5) , wherein the current detection device is arranged so as to overlap in a direction.
[0017]
(7) A measuring device including current detection means for measuring a voltage / current to be measured, wherein the current detection means includes a current input terminal and a current output terminal for supplying a measurement current to be detected, and the current input terminal. A shunt mold resistor having a molded shunt resistor, a heat sink that dissipates and dissipates heat, and each of the current input terminal and the current output terminal, and the shunt. Between each of both ends of the resistor, it is provided with an input conductor and an output conductor that are electrically connected and have a heat dissipation means and / or a magnetic field shielding means ,
The input conductor and / or output conductor provided with the heat dissipation means and / or the magnetic field shielding means are formed by forming a single plate member in a U shape and overlapping the plate members formed in the U shape in an insulated state. A measuring instrument equipped with a current detection device characterized by the above .
(8) The input conductor formed in the U-shape is formed larger than the output conductor formed in the U-shape, and the output conductor is the same inside the U-shape of the input conductor. A measuring instrument comprising the current detecting device according to (7), wherein the measuring device is arranged in a direction.
[0018]
(9) A measuring device including a current detection means for measuring a voltage / current to be measured, wherein the current detection means is a secondary current on the secondary side according to a current to be detected input to the primary side. A shunt mold resistor having a shunt resistor for flowing a secondary current generated on the secondary side, a heat sink for dissipating heat by disposing the shunt mold resistor, and a secondary of the current transformer An input conductor and an output conductor that are electrically connected between each of both ends of the side and each of both ends of the shunt resistor and have a heat dissipating means and / or a magnetic field shielding means ,
The input conductor and output conductor provided with the heat dissipation means and / or magnetic field shielding means are formed by forming a single plate member in a U-shape and overlapping the plate members formed in the U-shape in an insulated state. A measuring instrument provided with a current detection device characterized by the above .
(10) The shape of the input conductor formed in the U shape is larger than the output conductor formed in the U shape, and the output conductor is the same inside the U shape of the input conductor. A measuring instrument comprising the current detection device according to (9), wherein the measuring device is arranged in a direction.
[0019]
As described above, by providing the heat-dissipating means and / or the magnetic field shielding means to the shunt resistor used in the current detecting device, which is electrically connected directly and supplying the current, the heat dissipating the conductor directly connected to the shunt resistor. It is possible to release heat generated from the shunt resistor and suppress the temperature rise of the shunt resistor itself. Moreover, since the current loop area flowing through the shunt resistor can be reduced by overlapping the input and output conductors, the influence of the magnetic field generated by the input current on the shunt resistor can be reduced. it can.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a current detection method, a current detection device, and a measurement device including the current detection device according to the present invention will be described with reference to the drawings as a measurement device including a current detection unit.
[0021]
As shown in FIG. 1, the measuring device including the current detection unit according to the first embodiment of the present invention includes a measurement unit 10 that measures a power supply voltage / current flowing through a load Z, and a measurement that is divided from the load Z. The current detector 11 is configured to supply a current to the shunt resistor, detect the potential difference, and measure the power supply voltage / current.
[0022]
As shown in FIGS. 1 and 2, the current detection unit 11 is configured to detect a current using a shunt resistor 3 as a resistor as in the conventional technique, and a current input terminal for inputting a measurement current Iin. A current output terminal 1b that outputs an output current Iout that flows through 1a and the shunt resistor 3, a shunt mold resistor 4 that molds a shunt resistor 3 that flows a measurement current Iin that is input from the current input terminal 1a, and a current input terminal An input conductor 7a and an output conductor 7b that are electrically connected to the connection lines 5a and 5b connected to both ends of the shunt resistor 3 between 1a and the current output terminal 1b. Yes.
[0023]
Each of the input conductor 7a and the output conductor 7b is provided with a heat radiating means and / or a magnetic field shielding means, and a single plate member is formed in a U shape and the plate member formed in the U shape is insulated. It has a structure that is arranged in layers. The input conductor 7a having such a structure is provided between the connection line 5a and the current input terminal 1a and is electrically connected to each other. The output conductor 47b is connected to the connection line 5a. 5b and the current output terminal 1b are provided and electrically connected to each other. Here, the portion to which the input conductor 7a is connected is the side wall surface of the standing portion formed in a U shape, and the portion to which the connection line 5a is connected is formed in a U shape to which the input conductor 7a is connected. It is a side wall surface of the standing part on the opposite side of a standing part. On the other hand, the output conductor 7b is connected to the side wall surface of the upright portion formed in a U shape, and the connection line 5b is connected to the U shape to which the input conductor 7b is connected. It is a side wall surface of the standing part on the opposite side of the formed standing part.
[0024]
Also, the input conductor 7a formed in a U-shape is formed larger than the output conductor 7b, which is also formed in a U-shape. The output conductors 7b are arranged in the same direction with the insulator 8 interposed therebetween.
[0025]
The shunt mold resistor 4 is configured on the heat sink 6 to release heat generated from the molded shunt resistor 3.
[0026]
In the above configuration, the input conductors and the output conductors 7a and 7b have various shapes by changing the shape as shown below as compared with a conductor using a single plate member that has been conventionally used as it is. Has an effect.
[0027]
(1) By making the input and output conductors 7a and 7b U-shaped, the area can be increased compared to a single plate and the distance to the shunt resistor 3 can be shortened, that is, thicker and shorter. be able to. As a result, the power loss of the input and output conductors 7a and 7b itself is smaller than that of a single plate, and the amount of heat generated by the input and output conductors 7a and 7b itself is reduced. Therefore, it is possible to prevent the heat generated by the input and output conductors 7a and 7b from becoming a factor that raises the temperature of the shunt resistor 3.
[0028]
(2) Since the surface area and volume can be increased by making the input and output conductors 7a and 7b have U-shapes, the heat radiation of the input and output conductors 7a and 7b themselves is increased. be able to. Here, since the input and output conductors 7a and 7b are directly connected to the shunt resistor 3 via the connection lines 5a and 5b, the heat generated by the shunt resistor 3 is released from the input and output conductors 7a and 7b. Therefore, the temperature rise of the shunt resistor 3 can be suppressed.
[0029]
(3) Since the input and output conductors 7a and 7b overlap each other, specifically, a bottom portion formed in a U-shape, the current input terminal 1a → the shunt resistor 3 → Since the area of the current loop of the current output terminal 1b is reduced, the influence of the magnetic field generated by the input current (measurement current Iin) on the shunt resistor 3 can be reduced. Further, since the overlapping portion functions as an electrostatic shield, electrostatic noise entering the shunt resistor 3 can be reduced.
[0030]
(4) The vertical distance between the input and output conductors 7a and 7b is shortened and the overlapping area is increased. Thereby, the effect of (3) can be further increased.
[0031]
Thus, although it becomes redundant description, by changing the shape of the input conductor 7a and / or the output conductor 7b, the input and output conductors 7a, 7b work as a radiator directly connected to the shunt resistor 3, Since the heat generated by the shunt resistor 3 can be released, the temperature rise of the shunt resistor 3 is suppressed. In addition, since the current loop area flowing through the shunt resistor 3 is reduced by overlapping the input and output conductors 7a and 7b, the influence of the magnetic field generated by the input current on the shunt resistor 3 is also reduced. That is, the influence of the error factor of the current measurement can be further reduced, and the current measurement in which the error due to heat is reduced can be realized by a simple and low-cost method as compared with the conventional case.
[0032]
More specifically, for example, for the 1 mΩ shunt resistor 3 for current detection, the following two types of input and output conductors 7a and 7b are prepared.
[0033]
(1) L × W × t = 50 mm × 10 mm × 1 mm (conventional type)
(2) L × W × t = 50 mm × 20 mm × 1 mm (improved type)
[0034]
Here, the improved input and output conductors 7a and 7b have a resistance value half that of the conventional input and output conductors, and have twice the volume. When the temperature rise test of the shunt resistor 3 was performed using these input and output conductors 7a and 7b, the temperature rise of the conventional type was 17.9 ° C., and the temperature rise of the improved type was 16.2 ° C. It was. In other words, the improved input and output conductors 7a and 7b have the temperature lowered by 1.7 ° C. by making the width twice as large (widened). This is about 10% improvement. Further, for example, when the temperature coefficient of the shunt resistor 3 is 200 ppm / ° C., the increase in the resistance value due to the heat generation of the shunt resistor 3 is 0.00358 mΩ for the conventional type and 0.00324 mΩ for the improved type, and the improved type is the conventional type. Compared with the mold, the deviation due to the temperature of 340 ppm was suppressed.
[0035]
Thus, the temperature change of the shunt resistor 3 can be improved by doubling the volume of the input and output conductors 7a and 7b.
[0036]
That is, according to the present embodiment, the shape of the input and output conductors 7a and 7b can be made U-shaped to increase the surface area, and both the input and output conductors 7a and 7b can be overlapped. By adopting a shape that can be used, it is possible to suppress the temperature rise of the shunt resistor 3 and to further reduce the influence of heat generation and generated magnetic field of the shunt resistor 3 that is an error factor of current measurement. Therefore, it is possible to realize current measurement with reduced errors due to heat generation by a simple and low-cost method as compared with the conventional case.
[0037]
Next, a measuring instrument provided with the current detection device of the second embodiment will be described with reference to FIG. This measuring device includes a current detection unit that inputs a measurement current using a current transformer in the same manner as that for detecting a current using a shunt resistor.
[0038]
As shown in FIG. 3, the measuring device that obtains the measurement current with the current transformer includes a measurement unit 10a that generates a measurement current I2 by supplying the power supply voltage / current I1 to the current transformer CT, and a measurement current obtained with the current transformer CT. The current detection unit 11 is configured to supply I2 → Iin to the shunt resistor 3 and detect the potential difference to measure the power supply voltage / current. Since this current detection unit 11 is the same as the current detection unit of the measurement instrument of the first embodiment described above, the same reference numerals are given and description thereof is omitted.
[0039]
The current transformer 31 includes a primary side coil L1 that flows an input current I1 and a secondary side coil L2 that is created at a certain ratio. Both ends of the secondary side coil L2 are current input terminals 1a and 1a of the current detection unit. It is configured to be connected to the current output terminal 1b.
[0040]
In the measuring device having such a configuration, the input current I1 input from the outside to the primary coil L1 is transformed to, for example, 1/500 of the input current via the current transformer 31, and the secondary side A secondary current I2 is generated in the coil L2. The secondary current I2 passes through the current input terminal 1a and the input conductor 7a and flows to the shunt resistor 3 as the measurement current Iin, passes through the current output terminal 1b through the output conductor 7b, and is output as the output current Iout. Therefore, the value of the secondary current I2 can be measured by detecting the potential difference generated at both ends of the shunt resistor 3. Therefore, by using the characteristics of the current transformer 31, as a result, the input current I1 can be measured to measure the power supply voltage / current.
[0041]
In addition, since current transformation is performed by the current transformer CT, the current value of the secondary current I2 is small. At this time, in order to detect a small current, the shunt resistor 3 having a relatively large resistance value is required, so that power consumption and heat generation in the shunt resistor 3 also increase. Therefore, conventionally, even when a current is detected by the shunt resistor 3 via the current transformer CT, the temperature rise of the shunt resistor 3 has become an error factor of current measurement.
[0042]
However, by using the U-shaped input conductor 7a and output conductor 7b improved according to the present invention, the input and output conductors 7a and 7b function as a heat radiator directly connected to the shunt resistor 3. Since the heat generated by the shunt resistor 3 can be actively released, the temperature rise of the input and output conductors 7a and 7b themselves can be suppressed as compared with the conventional method, and an error in current measurement can be achieved. The influence of temperature rise as a factor can be reduced.
[0043]
【The invention's effect】
As described above, according to the present invention, the influence of the current measurement error factor can be reduced by providing the heat radiation means and / or the electromagnetic shielding means on the conductor directly connected to the shunt resistor. Thus, it is possible to obtain an effect that a method of suppressing heat generation and reducing a current measurement error can be realized easily and at low cost.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a schematic configuration of a measuring instrument including a current detection unit according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a schematic configuration of the current detection unit.
FIG. 3 is an explanatory diagram illustrating a schematic configuration of a measuring instrument including a current detection unit that performs current detection using a current transformer according to a second embodiment.
FIG. 4 is an explanatory diagram showing a schematic configuration of a current detection device employed in a conventional current input unit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1a Current input / output terminal 1b Current output terminal 2 Mold 3 Shunt resistor 4 Shunt mold resistor 5a Connection line 5b Connection line 6 Heat sink 7a Input conductor 7b Output conductor 8 Insulator 10 Measurement unit 10a Measurement unit 11 Current detection unit

Claims (10)

A shunt mold resistor having a molded shunt resistor is arranged on a heat sink for heat dissipation, each of two connection lines connected to both ends of the shunt resistor, a current input terminal capable of flowing a desired measurement current, and Electrically connecting each of the input conductor and / or output conductor having the heat dissipation means and / or magnetic field shielding means between each of the current output terminals ;
The input conductor and / or output conductor having the heat radiation means and / or the magnetic field shielding means are formed by forming a single plate member in a U shape and overlapping the plate member formed in the U shape in an insulated state. The current detection method characterized by the above-mentioned. The input conductor formed in the U-shape is formed larger than the output conductor formed in the U-shape, and the output conductor is stacked in the same direction on the inner side of the U-shape of the input conductor. The current detection method according to claim 1 , wherein the current detection method is arranged. A current input terminal and a current output terminal for supplying a measurement current to be detected, a shunt mold resistor connected between the current input terminal and the current output terminal and having a molded shunt resistor, and the shunt mold resistor And a heat sink for dissipating heat and an input conductor and an output conductor electrically connected between each of the current input terminal and the current output terminal and both ends of the shunt resistor. In
The input conductor and / or the output conductor are provided with heat radiating means and / or magnetic field shielding means ,
The input conductor and / or output conductor provided with the heat dissipation means and / or the magnetic field shielding means are formed by forming a single plate member in a U shape and overlapping the plate members formed in the U shape in an insulated state. A current detection device characterized by that. The input conductor formed in the U-shape is formed larger than the output conductor formed in the U-shape, and the output conductor is stacked in the same direction on the inner side of the U-shape of the input conductor. The current detection device according to claim 3 , wherein the current detection device is arranged. A current transformer that generates a measurement current of a secondary current on the secondary side according to a current to be measured input to the primary side, and a shunt mold resistor including a molded shunt resistor that passes the secondary current; A heat sink that dissipates heat by disposing the shunt mold resistor, and an input conductor and an output conductor that are electrically connected between both ends of the secondary side of the current transformer and both ends of the shunt resistor; In a current detection device having:
The input conductor and / or the output conductor are provided with heat radiating means and / or magnetic field shielding means ,
The input conductor and / or output conductor provided with the heat dissipation means and / or the magnetic field shielding means are formed by forming a single plate member in a U shape and overlapping the plate members formed in the U shape in an insulated state. A current detection device characterized by that. The input conductor formed in the U-shape is formed larger than the output conductor formed in the U-shape, and the output conductor is stacked in the same direction on the inner side of the U-shape of the input conductor. The current detection device according to claim 5 , wherein the current detection device is arranged. A measuring device having a current detecting means for measuring a voltage / current to be measured,
The current detection means includes a current input terminal and a current output terminal for supplying a measurement current to be detected; a shunt mold resistor connected between the current input terminal and the current output terminal and having a molded shunt resistor; A heat sink for dissipating and dissipating the shunt mold resistor, and electrically connecting and dissipating means and / or magnetic field shielding between each of the current input terminal and current output terminal and both ends of the shunt resistor. An input conductor and an output conductor provided with means ,
The input conductor and / or output conductor provided with the heat dissipation means and / or the magnetic field shielding means are formed by forming a single plate member in a U shape and overlapping the plate members formed in the U shape in an insulated state. A measuring instrument equipped with a current detection device characterized by the above. The input conductor formed in the U-shape is formed larger than the output conductor formed in the U-shape, and the output conductor is stacked in the same direction on the inner side of the U-shape of the input conductor. 8. A measuring instrument comprising the current detecting device according to claim 7, wherein A measuring device having a current detecting means for measuring a voltage / current to be measured,
The current detection means includes a current transformer that generates a secondary current on the secondary side according to a current to be detected input to the primary side, and a shunt resistor that causes the secondary current generated on the secondary side to flow. And electrically connecting between the shunt mold resistor, the heat sink that dissipates the heat by disposing the shunt mold resistor, and both ends of the secondary side of the current transformer and both ends of the shunt resistor. An input conductor and an output conductor provided with a heat dissipating means and / or a magnetic field shielding means ,
The input conductor and output conductor provided with the heat dissipation means and / or magnetic field shielding means are formed by forming a single plate member in a U-shape and overlapping the plate members formed in the U-shape in an insulated state. A measuring instrument provided with a current detection device characterized by the above. The input conductor formed in the U-shape is formed larger than the output conductor formed in the U-shape, and the output conductor is stacked in the same direction on the inner side of the U-shape of the input conductor. 10. A measuring instrument comprising the current detection device according to claim 9, wherein

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