WO2013121506A1 - Current detector - Google Patents

Abstract

A current detector (1) is provided with a circuit substrate (13) on which a detection unit is mounted, and a connection terminal (14) which is disposed on the circuit substrate (13) and to which a current transformer (5) is connected. The connection terminal (14) has a first connection terminal (141) to which the connection line (106) of a first current transformer (51) is connected, and a second connection terminal (142) to which the connection line (106) of a second current transformer (52) is connected. The first connection terminal (141) and the second connection terminal (142) have a different shape and one of the connection terminals is disposed on one surface (131) of the circuit substrate (13) while the other connection terminal is disposed on the other surface (132) of the circuit substrate (13). Moreover, the first connection terminal (141) and the second connection terminal (142) are disposed on a location so as to overlap with one another in the thickness direction of the circuit substrate (13). Therefore, the current detector (1) can handle various different current transformers (51, 52) and the size of the current detector (1) can be reduced because the first connection terminal (141) and the second connection terminal (142) which have different shapes are disposed on the front and rear surfaces of the circuit substrate (13).

Description

Current detector

The present invention relates to a current detector that detects a current to be detected based on an output of a current transformer.

Conventionally, in houses, office buildings, etc., the power received by the power receiving facility from the power system (distribution system) is generally branched into a plurality of indoor wirings at the distribution panel or distribution board, and each of the power is distributed via the branched indoor wirings. A system that supplies power to the load is employed. In this type of system, it has been proposed to use a power measuring device (multi-circuit watt-hour meter) that measures the amount of power at each of a plurality of measurement points of an AC circuit for the purpose of energy saving or the like (for example, a Japanese patent) (See publication 2005-55404).

This power measurement device includes a current detector (current measurement circuit) that measures current at a measurement point in addition to a voltage measurement circuit that measures the voltage of an AC circuit in order to calculate power from voltage and current. . The current detector is connected to a current transformer coupled to the measurement point of the AC circuit, and measures the current at the measurement point based on the output of the current transformer. This type of current detector includes a circuit board on which a detection unit that detects a current to be detected based on the output of the current transformer is mounted, and the circuit board has a connection terminal (connector) to which the current transformer is connected. Is provided.

By the way, as a general current transformer, a current transformer capable of obtaining a relatively large current (for example, about several A) when a rated current is applied, and a current having a relatively small output (for example, about several tens of mA). There is a current transformer. The former current transformer has a large core and is relatively large as a whole, and the latter current transformer has a small core and is relatively small as a whole. These different types of current transformers may be used depending on the application, but the main current transformers may differ depending on the country or region. Since different types of current transformers have significantly different output currents, in order to accommodate these different types of current transformers, the current detector has a separate input resistance (input impedance) for each current transformer. There is a need.

Therefore, a current detector is considered in which individual connection terminals are provided for each current transformer so that different types of current transformers are used, and the resistance value of the input resistance is different for each connection terminal. In this type of current detector, the shape of the connection terminal is different for each current transformer so that an erroneous connection (incorrect connection) of the current transformer does not occur. However, when the connection terminals having different shapes are arranged on one surface of one circuit board, the area occupied by the connection terminals on the circuit board becomes larger than the case where only one type of connection terminal is provided, This hinders downsizing of the current detector.

The present invention has been made in view of the above reasons, and an object of the present invention is to provide a current detector that can be easily downsized while being compatible with different types of current transformers.

The current detector of the present invention includes a circuit board on which a detection unit that detects a current to be detected based on an output of a current transformer is mounted, and a connection terminal provided on the circuit board and connected to the current transformer. And the connection terminal has a first connection terminal and a second connection terminal, each having a different shape and connected to the detection unit, and the first connection terminal and the second connection terminal. Is provided on one surface and the other surface of the circuit board at positions overlapping each other.

According to the present invention, the first connection terminal and the second connection terminal having different shapes are provided on the one surface and the other surface of the circuit board and overlapped with each other. While corresponding to a current transformer, there is an advantage that miniaturization is easy.

In this current detector, it is preferable that the first connection terminal is a screw type terminal having a terminal screw, and the second connection terminal is a plug-in type terminal.

In this current detector, it is more preferable that a plurality of each of the first connection terminal and the second connection terminal is provided on one circuit board.

It is sectional drawing which shows the structure of the principal part of the current detector which concerns on embodiment. It is a block diagram which shows the structure of the electric quantity management system which concerns on embodiment. It is a circuit diagram which shows the structure of the principal part of the current detector which concerns on embodiment.

The current detector of this embodiment is used in a power measuring device 100 (see FIG. 2) that measures the amount of power at each of a plurality of measurement points of an AC circuit. This power measuring device 100 is provided in a distribution board (not shown) in a house or the like, for example, and measures the amount of power supplied to a load 101 (see FIG. 2) for each branch circuit for each branch circuit. The measurement result is output to the monitoring device 102 (see FIG. 2). The load 101 is, for example, various electric devices such as a lighting fixture, a water heater, an air conditioner, and a television. As a result, the user can confirm the amount of electricity used in the load 101 by the monitoring device 102.

First, a schematic configuration of the power measuring apparatus 100 will be described with reference to FIG.

The power measuring apparatus 100 calculates the power, a current detector 1 that detects a current flowing in a power supply path (branch circuit) 104 from the AC power supply 103 to the load 101, a voltage detector 2 that detects a voltage of the power supply path 104, and power A power calculation unit 3 that performs data output, and a data output unit 4 that outputs data.

The current detector 1 is connected to a current transformer (CT) 5 provided at a measurement point set at a predetermined position of the power feeding path 104 in the distribution board, and is detected based on the output of the current transformer 5. The current at the measurement point is detected. Here, the current detector 1 measures the magnitude of the current flowing through the measurement point of the power supply path 104 and outputs a current signal representing the current value to the power calculation unit 3. The voltage detector 2 is connected to, for example, a main circuit in the distribution board, measures the voltage magnitude of the power supply path 104, and outputs a voltage signal representing the voltage value to the power calculation unit 3. The current detector 1 and the voltage detector 2 have an addition circuit (not shown) that adds a predetermined value to the output signal (current signal, voltage signal). The current signal and voltage signal raised by the amount are input.

The power calculation unit 3 is mainly composed of a microcomputer, and based on the current signal from the current detector 1 and the voltage signal from the voltage detector 2, at the measurement point where the current transformer 5 is provided. Calculate power. Here, the power calculation unit 3 includes an A / D conversion unit (not shown) that converts each analog signal from the current detector 1 and the voltage detector 2 into a digital signal, and each signal after A / D conversion. A multiplication unit (not shown) for obtaining power by multiplication. That is, the multiplication unit calculates power by multiplying the current and the voltage. The power calculation unit 3 calculates the amount of power every predetermined time by integrating the power values obtained by the calculation, and outputs the calculated amount of power to the data output unit 4. The power calculation unit 3 calculates the power after subtracting a predetermined value added by the addition circuit of the current detector 1 and the voltage detector 2 from the signal after A / D conversion.

The data output unit 4 has a communication function compliant with, for example, RS485, and outputs the amount of power obtained by the power calculation unit 3 to the monitoring device 102 through the communication line 105 by communication. In addition, the power measuring apparatus 100 includes an external memory interface (not shown) and a built-in memory, and the data output unit 4 outputs power to these memories and stores the power in the memory. It has a function. Furthermore, the data output unit 4 may output the power amount temporarily stored in the memory to the monitoring device 102 by communication.

The power measuring device 100 configured in this way, together with the current transformer 5 and the monitoring device 102, constitutes an electricity amount management system that manages, for example, the amount of electricity used for each branch circuit. The monitoring device 102 is composed of, for example, a personal computer (personal computer) connected to the power measuring device 100 via a network, acquires data from the power measuring device 100 periodically (for example, every hour), and stores the acquired data. Thereby, the monitoring apparatus 102 displays the data acquired from the electric power measurement apparatus 100 on a monitor (not shown), and can manage the electric usage etc. for every branch circuit.

Next, the configuration of the current detector 1 will be described with reference to FIG.

As shown in FIG. 3, the current detector 1 of the present embodiment includes two types of current transformers (hereinafter referred to as “current transformers 5”): a first current transformer 51 and a second current transformer 52. When not particularly distinguished, it is simply configured to be connectable to a “current transformer 5”. These different types of current transformers 51 and 52 differ in the magnitude of the output current at the time of current detection, and accordingly the overall size also differs. Basically, any one type is selected and the current is changed. Connected to the detector 1. These different types of current transformers may be used depending on the application, but the main current transformers may differ depending on the country or region.

In the present embodiment, the current transformer 5 includes an annular core (not shown) and a coil (not shown) made of a conductive wire wound around the core. The current transformer 5 is attached to a measurement point of the power supply path 104 so that the power supply path 104 (see FIG. 2) passes through the inside of the core, and both ends of the coil are connected to the current detector 1 via dedicated connection lines 106. Connected to. As a result, the current transformer 5 causes the output current corresponding to the current flowing through the power supply path 104 penetrating the core to flow to the current detector 1 via the connection line 106.

Here, the first current transformer 51 is configured such that a relatively large current (for example, about several A) flows through the coil when a rated current (for example, several hundred A) flows through the power supply path 104. The core is relatively large and the overall size is also relatively large. On the other hand, the second current transformer 52 is configured such that a relatively small current (for example, about several tens of mA) flows in the coil when a current flows in the power supply path 104, and the core is relatively The small overall size is also relatively small. In addition, these current transformers 5 may be a split type that can be attached while existing wiring is connected.

As shown in FIG. 3, the current detector 1 includes an input resistor 11 to which the current transformer 5 is connected and a detection unit 12 that detects a voltage generated at the input resistor 11. The input resistor 11 generates a voltage corresponding to the current at the measurement point to be detected by flowing the output current from the current transformer 5. Therefore, the detection unit 12 can acquire a value (voltage) corresponding to the current at the measurement point that is the detection target by detecting the voltage generated in the input resistor 11.

Here, although the detection unit 12 is common to the first current transformer 51 and the second current transformer 52, the output currents of these different types of current transformers 51 and 52 are significantly different. The detector 1 has a separate input resistor 11 for each of the current transformers 51 and 52. In the example of FIG. 3, the input resistor 11 is formed by connecting two types of resistors 111 and 112 having different resistance values in series, and the first current transformer 51 is connected to both ends of the first resistor 111. The second current transformer 52 is connected to both ends of the second resistor 112. For example, the first resistor 111 is a shunt resistor having a resistance value of 5 mΩ, and the second resistor 112 is a resistor having a resistance value of 3.3Ω. The shunt resistor is a highly accurate resistor having a small resistance value and made for current measurement of a circuit through which a large current flows.

In the series circuit of these two types of resistors 111 and 112, one end on the first resistor 111 side is connected to a circuit ground as a reference potential, and the other end on the second resistor 112 side is connected to the detection unit 12. ing. The circuit ground serving as the reference potential may be a zero potential or a predetermined potential other than the zero potential. In this way, the detection unit 12 measures the value of the current flowing through the measurement point of the feed path 104 by measuring the voltage across the input resistor 11 that is a series circuit of the resistors 111 and 112. Here, the detection unit 12 includes an addition circuit (not shown) that adds a predetermined value to the voltage across the input resistor 11, and outputs a current signal raised by a predetermined value to the power calculation unit 3. .

By the way, the current detector 1 includes a circuit board 13 (see FIG. 1) on which the detection unit 12 is mounted, and a connection terminal 14 provided on the circuit board 13 and connected to the current transformer 5. The connection terminal 14 includes a first connection terminal 141 to which the connection line 106 of the first current transformer 51 is connected, and a second connection terminal 142 to which the connection line 106 of the second current transformer 52 is connected. have. Each of the connection terminals 141 and 142 includes a pair of connection portions so that the two-wire connection line 106 is connected thereto.

In the circuit board 13, the first connection terminal 141 is connected to both ends of the first resistor 111 through a conductor pattern (not shown), and the second connection terminal 142 is connected to the second through the conductor pattern. The resistor 112 is connected to both ends. That is, the first connection terminal 141 and the second connection terminal 142 are each connected to the detection unit 12 via the conductor pattern. Therefore, in the state where the first current transformer 51 is connected to the first connection terminal 141, the detection unit 12 can detect the current at the measurement point based on the output current of the first current transformer 51. On the other hand, in a state where the second current transformer 52 is connected to the second connection terminal 142, the detection unit 12 can detect the current at the measurement point based on the output current of the second current transformer 52.

The first connection terminal 141 and the second connection terminal 142 have different terminal shapes, and the first current transformer 51 can be connected only to the first connection terminal 141, and the second current transformer 52 is The front end portion of the connection line 106 has a different structure so that only the second connection terminal 142 can be connected. In the present embodiment, the first connection terminal 141 is a screw type terminal having a terminal screw (not shown), and the second connection terminal 142 is a plug-in type connector terminal. That is, each of the current transformers 51 and 52 does not match the tip structure of the connection line 106 with the connection terminals 142 and 141 that are not the original connection destinations. Therefore, the first current transformer 51 has the second connection terminal. 142 cannot be connected to the first connection terminal 141 in the second current transformer 52. Therefore, in the construction contractor, when connecting the current transformers 51 and 52 to the power measuring device 100, a construction error that connects the current transformers 51 and 52 to the connection terminals 142 and 141 that are not the original connection destinations. This can be avoided, and erroneous connection (incorrect connection) of the current transformers 51 and 52 is prevented.

Here, in the present embodiment, the first connection terminal 141 and the second connection terminal 142 include one surface 131 (upper surface in FIG. 1) 131 and the other surface (FIG. 1) as shown in FIG. 1 is provided separately from the lower surface 132. In the example of FIG. 1, the first connection terminal 141 is surface-mounted on one surface 131 of the circuit board 13, and the second connection terminal 142 is surface-mounted on the other surface 132.

Furthermore, the first connection terminal 141 and the second connection terminal 142 are provided at positions overlapping each other in the thickness direction of the circuit board 13. That is, these connection terminals 141 and 142 are provided separately on the front and back of the circuit board 13 so that at least a part of one of the connection terminals 141 and 142 is located in the other projection plane. In the example of FIG. 1, these connection terminals 141 and 142 are both provided at one end of the circuit board 13.

In the present embodiment, the first connection terminal 141 made of a screw-type terminal has a height dimension from the circuit board 13 larger than that of the second connection terminal 142 made of a connector terminal. On the other hand, an introduction port (not shown) for introducing the connection line 106 is formed. The connection line 106 of the first current transformer 51 is not subjected to any special end treatment because the coating of the tip end portion is peeled off. The first connection terminal 141 fixes the connection line 106 by tightening the terminal screw in a state where the tip end of the connection line 106 of the first current transformer 51 is inserted from the introduction port. It is electrically connected to the flow device 51.

On the other hand, the second connection terminal 142 made of a connector terminal is formed with an introduction port (not shown) for introducing the connection line 106 to the side (left side in FIG. 1). The connection line 106 of the second current transformer 52 is attached with a current transformer-side connector 521 that can be coupled to the second connection terminal 142 at the tip. The second connection terminal 142 is electrically connected to the first current transformer 52 by fixing the connection line 106 when the current transformer-side connector 521 is inserted from the introduction port.

The circuit board 13 is housed in a synthetic resin case 15 and fixed to a fixed position of the case 15. In the example of FIG. 1, the circuit board 13 is disposed along the upper wall 151 of the case 15, and one end edge (the left end edge in FIG. 1) on the connection terminal 141, 142 side is brought into contact with the side wall 152 of the case 15 from the inside. It is fixed in such a position.

In the case 15, connection ports 153 and 154 open at positions corresponding to the introduction ports of the connection terminals 141 and 142 in the side wall 152, respectively, and further correspond to terminal screws of the first connection terminal 141 in the upper wall 151. An operation hole 155 is opened at the position. Accordingly, the connection line 106 of the first current transformer 51 is connected to the first connection terminal 141 through the connection port 153, and the connection line 106 of the second current transformer 52 is connected to the second connection through the connection port 154. The terminal 142 is connected. The operation of tightening or loosening the terminal screw of the first connection terminal 141 is performed through the operation hole 155.

In the present embodiment, the first resistor 111 is provided on one surface 131 of the circuit board 13, the second resistor 112 is provided on the other surface 132 of the circuit board 13, and the detection unit 12 is provided on the circuit board 13. It is provided on the other surface 132. Therefore, the first resistor 111 and the second resistor 112 are electrically connected through a through hole (not shown) formed in the circuit board 13, and the circuit ground is also connected through the through hole. Are drawn on both sides of the circuit board 13.

According to the current detector 1 of the present embodiment described above, the connection terminal 14 for connecting the current transformer 5 has the first connection terminal 141 and the second connection terminal 142 having different shapes. Yes. Therefore, the current detector 1 can cope with different types of current transformers 51 and 52 without causing erroneous connection (incorrect connection) of the current transformers 51 and 52.

In addition, in the current detector 1, the first connection terminal 141 and the second connection terminal 142 are the one surface 131 and the other surface 132 of the circuit board 13 and overlap each other in the thickness direction of the circuit board 13. In the position. Therefore, the current detector 1 can keep the area occupied by the connection terminals 14 on the circuit board 13 smaller than when the connection terminals 141 and 142 are provided on the same surface of the circuit board 13. There is an advantage that the current detector 1 as a whole is reduced in size.

In addition, since the first connection terminal 141 and the second connection terminal 142 are arranged as described above, the current detector 1 determines the distance to the detection unit 12 on the circuit board 13 from both the connection terminals 141. , 142. For this reason, the current detector 1 can align the length of the conductor pattern connected to the detection unit 12 between the connection terminals 141 and 142, thereby avoiding the occurrence of a phase shift by the current transformers 51 and 52. it can. Furthermore, since the current detector 1 can shorten the conductor pattern between the connection terminals 141 and 142 and the detection unit 12 as much as possible, the current detector 1 is less susceptible to the influence of external noise and can improve the current measurement accuracy. .

By the way, the number of the first connection terminals 141 and the second connection terminals 142 is not limited to one each provided on one circuit board 13, and a plurality of first connection terminals 141 and two second connection terminals 142 are provided on one circuit board 13. May be. In this case, the current detector 1 may detect the current of a plurality of circuits with the plurality of connection terminals 14 or may detect the current of one circuit with the plurality of connection terminals 14.

That is, the current detector 1 can detect the current of one circuit with one current transformer 5 if the detection target is a single-phase alternating current such as a single-phase two-wire system or a single-phase three-wire system. The terminal 14 can detect currents of a plurality of circuits. In addition, if the detection target is a multi-phase alternating current such as a three-phase four-wire system, the current detector 1 detects a current with one current transformer 5 for each phase, so that a plurality of connection terminals 14 are used for 1 The circuit current can be detected. Furthermore, even when the detection target is a multi-phase alternating current, the current detector 1 can detect the current of a plurality of circuits if a plurality of sets of connection terminals 14 that detect a current for one circuit are provided. It is.

In the current detector 1, a plurality of connection terminals 141 and 142 are provided on one circuit board 13 in this way, so that compared to a case where one connection terminal 141 and 142 is provided, respectively. The area occupied by the connection terminals 141 and 142 on the circuit board 13 increases. Therefore, in the current detector 1, the first connection terminal 141 and the second connection terminal 142 are the one surface 131 and the other surface 132 of the circuit board 13 and overlap each other in the thickness direction of the circuit board 13. The effect of downsizing due to the provision becomes more remarkable.

In the above embodiment, the first connection terminal 141 is a screw-type terminal and the second connection terminal 142 is a plug-in type connector terminal. However, the first connection terminal 141 and the second connection terminal are exemplified. It is not necessary to be different from 142, and terminals having different shapes may be used. For example, each of the first connection terminal 141 and the second connection terminal 142 is a connector terminal, and only the shape (including shape and size) may be different.

Claims (3)

A circuit board on which a detection unit for detecting a current to be detected based on the output of the current transformer is mounted, and a connection terminal provided on the circuit board and connected to the current transformer,
The connection terminal has a first connection terminal and a second connection terminal, each having a different shape and connected to the detection unit,
The first connection terminal and the second connection terminal are provided on one surface and the other surface of the circuit board at positions overlapping each other in the thickness direction of the circuit board. Current detector. The current detector according to claim 1, wherein the first connection terminal is a screw-type terminal including a terminal screw, and the second connection terminal is a plug-in type terminal. 3. The current detector according to claim 1, wherein a plurality of each of the first connection terminal and the second connection terminal is provided on one circuit board. 4.

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