Connection failure detection device

Abstract

To provide a connection failure detection device that is able to detect a connection failure before a heat generation temperature becomes high even if the connection failure occurs in a state in which a circuit current is large.SOLUTION: A connection failure detection device includes: a sensitivity setting unit 4 configured to vary, in accordance with a circuit current, a threshold voltage for determining an occurrence of a connection failure; a potential difference determination unit 5 configured to monitor a potential difference between a power-supply-side terminal 2a and a load-side terminal 2b to compare and determine the potential difference with the threshold voltage; a current generation unit 3 configured to generate an adjustment current having the same phase as that of an AC power supply 10 and causes the adjustment current to flow between the power-supply-side terminal 2a and the load-side terminal 2b in addition to a current supplied from the AC power supply 10; a first current transformer 7 configured to measure all currents flowing between power-supply-side terminal 2a and the load-side terminal 2b; and a display 6 configured to give notification of an occurrence of a connection failure. The sensitivity setting unit generates the threshold voltage in inverse proportion to a current value measured by the first current transformer 7. The potential difference determination unit 5 determines that a connection failure has occurred when the potential difference between the power-supply-side terminal 2a and the load-side terminal 2b exceeds the threshold voltage set by the sensitivity setting unit 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a connection failure detection device for detecting connection failures in electrical path connections such as terminal portions. [Background technology]

[0002] At electrical circuit connections where electrical circuits such as electric wires and conductor bars are connected, connection failures can occur due to loose screws, loose plugs, etc. If a connection failure occurs at a connection through which a relatively large current flows, such as in a distribution line or an electrical circuit to power equipment, the increased contact resistance can cause heat generation, which can deteriorate the equipment and, in the worst case, can even cause arc discharge, which can lead to a fire. Therefore, to avoid this, there is a technology disclosed in, for example, Patent Document 1, which is a device for detecting the occurrence of connection failures. In Patent Document 1, a photocoupler is arranged so that it turns on when there is a potential difference between terminals, and a connection failure is detected when this photocoupler turns on. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-145083 Summary of the Invention [Problem to be solved by the invention]

[0004] The conventional technology for detecting a connection failure is configured to determine that a connection failure has occurred when the voltage drop occurring between the terminals reaches a predetermined value. In this case, the current value flowing through the connection is not a physical quantity used to determine a connection failure, so even if the voltage drop amount is the same, the amount of heat generated at the time when the connection failure is determined to have occurred varies. For example, if the voltage drop to be judged is 1.0V, then when the circuit current is 5A and the contact resistance is 0.2Ω, a voltage drop of 1.0V will occur. Also, when the circuit current is 25A and the contact resistance is 0.04Ω, the voltage drop will be 1.0V. On the other hand, when looking at the power generated (heat generation) when a poor connection is detected, since power = voltage x current, a circuit current of 5A is 5W, and a circuit current of 25A is 25W, a difference of 5 times. In this way, when detecting the voltage drop, if the current in the circuit is large, the amount of heat generated is large, and so there are cases where a dangerous condition has already been reached by the time a connection failure is detected.

[0005] In view of these problems, the present invention aims to provide a connection failure detection device that can detect a connection failure before the heat generation temperature becomes too high, even if the connection failure occurs when the circuit current is large. [Means for solving the problem]

[0006] In order to solve the above problem, the invention of claim 1 is a connection failure detection device that detects connection failures in an electric circuit connection section provided in an electric circuit to which an AC power source is connected in order to supply AC power to a load, the electric circuit connection section having a power source side terminal to which the power source side electric circuit is connected and a load side terminal to which the load side electric circuit is connected, and having a sensitivity setting section that varies a threshold voltage for determining whether a connection failure has occurred in accordance with an electric circuit current, a potential difference determination section that monitors a potential difference between the power source side terminal and the load side terminal and compares it with the threshold voltage, an adjustment current generation section that generates an adjustment current in phase with the AC power source and flows it between the power source side terminal and the load side terminal in addition to the current supplied from the AC power source, a total current measurement section that measures the total current flowing between the power source side terminal and the load side terminal, and a notification section that notifies the occurrence of a connection failure, and the sensitivity setting section is configured to change a threshold voltage based on a current value measured by the total current measurement section The proportionality coefficient has a negative proportional relationship The threshold voltage is generated, and the potential difference determining section determines that a connection failure has occurred when the potential difference between the power supply side terminal and the load side terminal exceeds the threshold voltage set by the sensitivity setting section. According to this configuration, the threshold voltage for determining whether a connection failure has occurred is set based on the current flowing through the electrical path connection portion. The proportionality coefficient has a negative proportional relationshipTherefore, even if a connection failure occurs when the electric circuit current is large, the connection failure can be detected before the heat generation temperature becomes high, and the heat generation temperature will not reach a dangerous temperature regardless of the magnitude of the current flowing through the electric circuit connection part. Furthermore, even if the current supplied from the power supply to the load is small, a regulated current is passed through the circuit connection, so the voltage drop due to a poor connection can be increased more than when it is caused by the circuit current alone, and poor connection can be reliably detected.

[0007] The invention of claim 2 is characterized in that, in the configuration described in claim 1, the adjustment current generation unit generates a current of a constant magnitude and flows it between the power supply side terminal and the load side terminal. According to this configuration, the current value generated by the adjustment current generating section is constant, so that the adjustment current generating section can be configured with a simple circuit.

[0008] The invention of claim 3 is characterized in that, in the configuration described in claim 1, the adjustment current generation unit has a circuit current measurement unit that measures the circuit current supplied from the power source to the load, a specified current memory unit that stores a specified value of the current to be passed through the circuit connection unit, a power supply unit that generates and outputs a current, and a current control unit that controls the output current of the power supply unit, and the current control unit controls the power supply unit so that the current flowing through the circuit connection unit becomes the specified value. According to this configuration, for example, the rated current of the electric path connection portion can be constantly passed through the electric path connection portion, and therefore, by constantly passing a large current, connection defects can be reliably detected. [Effects of the Invention]

[0009] According to the present invention, the threshold voltage for determining whether a connection failure has occurred is determined based on the current flowing through the electrical path connection. The proportionality coefficient has a negative proportional relationship Therefore, even if a connection failure occurs when the electric circuit current is large, the connection failure can be detected before the heat generation temperature becomes high, and the heat generation temperature will not reach a dangerous temperature regardless of the magnitude of the current flowing through the electric circuit connection part. Furthermore, even if the current supplied from the power supply to the load is small, a regulated current is passed through the circuit connection, so the voltage drop due to a poor connection can be increased more than when it is caused by the circuit current alone, and poor connection can be reliably detected. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a circuit block diagram showing an example of a connection failure detection device according to the present invention; [Figure 2] This is a waveform diagram showing the relationship between the circuit current and the regulating current, where (a) is the circuit current, (b) is the regulating current, and (c) is the combined current flowing through the circuit connection. [Figure 3] 10 is a diagram showing the relationship between the threshold voltage set by the sensitivity setting unit and the current flowing in the electrical path connection unit. FIG. [Figure 4] FIG. 2 is a circuit block diagram showing a connection failure detection device provided in a three-phase electric circuit. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments embodying the present invention will be described in detail with reference to the drawings. Fig. 1 is a circuit block diagram showing an example of a connection failure detection device according to the present invention, illustrating a configuration in which the device is installed in a single-phase electric circuit. The electric circuit L is a single-phase, two-wire system consisting of two electric wires (a first electric wire L1 and a second electric wire L2) that supply power from a power source 10 consisting of single-phase 100V AC commercial power to a load 11. The connection failure detection device 1 is configured to detect a connection failure if one occurs in an electric circuit connection portion 2 attached to the electric circuit L.

[0012] The electrical path connection portion 2 has a power supply side terminal 2a and a load side terminal 2b, and is provided on both of the electrical paths L consisting of two wires, the electric wires L1 and L2. Under normal conditions, the power supply terminal 2a and the load terminal 2b are connected with little or no contact resistance, but if a connection failure occurs, the contact resistance between these terminals increases, causing a voltage drop proportional to the current in the circuit. The r in Figure 1 represents this contact resistance.

[0013] Furthermore, I is the circuit current, I1 is the current flowing through the circuit connection section 2, and I2 is the current (adjusted current) sent from the current generation section (adjusted current generation section) 3 described later, and these currents have the following relationship: I1=I+I2 Note that I3 indicates the current detected by the first current transformer 7 described later, and the direction of each current arrow indicates the direction of the current when the connection failure detection device 1 performs detection operation, and operates within a half-wave with one polarity of the power supply 10. Also, for the sake of convenience of explanation, Figure 1 shows a case in which the connection failure detection device 1 is installed in only one of the two pairs of power supply side terminals 2a and load side terminals 2b (the circuit connection portion 2 of the second circuit L2), but in reality, connection failure detection devices are installed in both pairs.

[0014] The connection failure detection device 1 has a current generation unit 3 that generates an adjusted current, a sensitivity setting unit 4 that sets a threshold value for determining whether a connection failure has occurred, a potential difference determination unit 5 that determines whether a connection failure has occurred, and a display device 6 that serves as a notification unit that displays the determination result. Further, 7 and 8 are current transformers constituting the current measurement means, with 7 being a first current transformer that measures the current flowing through the electrical circuit connection part 2 and 8 being a second current transformer that measures the current of the electrical circuit L. The first current transformer 7 is installed at a location where the electrical circuit current I is measured, not at the electrical circuit connection part 2, but is configured to measure the current I1 that actually flows through the electrical circuit connection part 2 by winding an electrical wire through which the regulated current I2 generated by the current generation part 3 flows.

[0015] The current generating unit 3 includes a power supply unit 31 that generates an adjusted current I2, which is a current that is passed through the electrical path connection unit 2 in synchronization with the power supply 10, a current measuring unit 32 that measures the current of the electrical path L, a memory unit 33 that stores a predetermined current value (prescribed value), a current control unit 34 that controls the current generated by the power supply unit 31, and an isolation transformer 35 that isolates the current generating unit 3 from the electrical path L. The power supply unit 31 generates an AC current of a constant magnitude and in phase based on the phase information of the circuit current I measured by the second current transformer 8.

[0016] The regulated current I2 is generated via an isolation transformer 35 and supplied between the power supply side terminal 2a and the load side terminal 2b. The regulated current I2 is also supplied to the first current transformer 7. Figure 2 is a waveform diagram showing the relationship between the circuit current I and the regulating current I2, where (a) shows the circuit current I, (b) shows the regulating current I2, and (c) shows the combined current I1 flowing through the circuit connection part 2.

[0017] The current measurement unit 32 calculates the electric path current I based on the measurement value of the second current transformer 8. The storage unit 33 also stores, for example, a rated current value which is the maximum current value that can be passed through the electric path connection unit 2.

[0018] The current control unit 34 controls the on / off of the regulated current I2. Specifically, when the current I1 flowing through the electric path connection unit 2 reaches the current value set in the storage unit 33 based on the electric path current information calculated by the current measurement unit 32, the current control unit 34 performs control to stop the regulated current I2. By passing the adjusted current I2 through the electrical path connection portion 2 in this way, the amount of voltage drop due to the contact resistance r of the electrical path connection portion 2 can be increased even if the electrical path current I is small, making it easier to detect poor connections.

[0019] The sensitivity setting unit 4 sets a threshold value for determining whether a connection failure has occurred. Specifically, it has a current information input unit 41, which is made up of a reference terminal 4a to which voltage information of the power supply side terminal 2a of the electric path connection unit 2 is input, and a current input terminal 4b to which information of a current flowing through the electric path connection unit 2 is input, and a threshold output terminal 4c that outputs a threshold voltage V2. The proportionality coefficient has a negative proportional relationship. Outputs changing voltage information. 3 shows the relationship between the threshold voltage V2 set by the sensitivity setting unit 4 and the current I1 flowing through the electrical path connecting unit 2. As shown in FIG. 3, the threshold voltage V2 output from the threshold output terminal 4c is proportional to the current I1 flowing through the electrical path connecting unit 2. The proportionality coefficient has a negative proportional relationship. The value output is the value indicated by 42.

[0020] The potential difference determination unit 5 determines whether a connection failure has occurred. Specifically, it has a voltage input terminal 5a to which voltage information of the load side terminal 2b of the electrical path connection unit 2 is input, a threshold input terminal 5b to which a threshold voltage V2 is input, and an output terminal 5c to which the determination result is output, and if the detected potential difference V1 exceeds the input threshold voltage V2, it outputs a signal (a connection failure occurrence signal) from the output terminal 5c. Note that 51 is a power supply terminal.

[0021] The display device 6 has a light-emitting display unit equipped with an LED or the like and an alarm sound generating unit, and when the potential difference determination unit 5 outputs a connection failure occurrence signal, it performs notification operations of the occurrence of a connection failure, such as lighting up the LED and sounding a buzzer.

[0022] In this way, the threshold voltage for determining whether a connection failure has occurred depends on the current flowing through the electrical path connection portion 2. The proportionality coefficient has a negative proportional relationship Therefore, even if a connection failure occurs when the circuit current I is large, the connection failure can be detected before the heat generation temperature becomes high, and the heat generation temperature will not reach a dangerous temperature regardless of the magnitude of the current flowing through the circuit connection part 2. Furthermore, even if the current supplied from the power source 10 to the load is small, the regulated current I2 is passed through the circuit connection portion 2, so the voltage drop due to a poor connection can be increased more than when it is caused only by the circuit current I, and the poor connection can be reliably detected. Furthermore, since the current value generated by the current generating unit 3 is constant, a simple circuit is sufficient.

[0023] Next, we will explain another embodiment of the connection failure detection device 1. In the above embodiment, the regulated current I2 flowing through the electrical path connection portion 2 is set to a constant value, but here it is made to fluctuate. In this case, based on the information on the electric path current I calculated by the current measurement unit 32, the current control unit 34 controls the power supply unit 31 to change and control the adjusted current I2 so that the current I1 flowing through the electric path connection unit 2 becomes the current set in the memory unit 33, regardless of changes in the electric path current I. As a result, for example, the rated current of the electric path connection unit 2 is always applied to the electric path connection unit 2. In this way, by constantly passing a large, constant current through the electrical path connection portion 2, a large voltage drop occurs even when the contact resistance r is small, making it possible to reliably detect poor connections.

[0024] Although the above embodiment has been described with reference to the electric circuit connection portion 2 of a single-phase two-wire electric circuit L, the connection failure detection device can also be applied effectively to a multi-phase electric circuit. For example, Fig. 4 shows an example in which the connection failure detection device is applied to a three-phase electric circuit. In Fig. 4, reference numeral 20 denotes a three-phase power source, and the electric circuit L has electric wires consisting of three phases L3 to L5 (third electric wire L3, fourth electric wire L4, fifth electric wire L5), and the connection failure detection device 1 is provided on the fourth electric wire L4. The power supply for the connection failure detection device 1 is obtained from two electric wires (the third electric wire L3 and the fifth electric wire L5) other than the electric wire to be detected. This configuration allows the connection failure detection device 1 to operate as smoothly as in the case of the single-phase electric circuit. In the case of a three-phase four-wire system, power can be supplied to the connection failure detection device from three electric wires other than the electric wire for which connection failure is to be detected. [Explanation of symbols]

[0025] 1··Connection failure detection device, 2··Electrical circuit connection section, 2a··Power supply side terminal, 2b··Load side terminal, 3··Current generation section (adjusted current generation section), 4··Sensitivity setting section, 5··Potential difference judgment section, 6··Display device (notification section), 7··First current transformer (total current measurement section), 8··Second current transformer (electrical circuit current measurement section), 11··Load, 31··Power supply section, 32··Current measurement section (electrical circuit current measurement section), 33··Memory section (specified current memory section), L··Electrical circuit, I2··Adjusted current.

Claims

1. A connection failure detection device for detecting a connection failure of an electric circuit connection portion provided in an electric circuit to which an AC power source is connected in order to supply AC power to a load, the electrical path connection portion has a power supply side terminal to which an electrical path on a power supply side is connected and a load side terminal to which an electrical path on a load side is connected, a sensitivity setting unit that varies a threshold voltage for determining whether a connection failure has occurred in accordance with a current in the electrical path; a potential difference determination unit that monitors a potential difference between the power supply side terminal and the load side terminal and compares the potential difference with a threshold voltage; an adjusting current generating unit that generates an adjusting current in phase with the AC power supply and flows the adjusting current between the power supply side terminal and the load side terminal in addition to the current supplied from the AC power supply; a total current measurement unit that measures a total current flowing between the power supply side terminal and the load side terminal; a notification unit that notifies the occurrence of a connection failure, the sensitivity setting unit generates the threshold voltage having a proportionality coefficient that has a negative proportional relationship with the measured current value of the total current measurement unit; A connection failure detection device characterized in that the potential difference determination unit determines that a connection failure has occurred when the potential difference between the power supply side terminal and the load side terminal exceeds the threshold voltage set by the sensitivity setting unit.

2. 2. The connection failure detection device according to claim 1, wherein the regulated current generating unit generates a current of a constant magnitude and causes the current to flow between the power supply side terminal and the load side terminal.

3. the adjusting current generating unit includes a circuit current measuring unit that measures a circuit current supplied from the power source to a load, a specified current storage unit that stores a specified value of a current to be passed through the circuit connecting unit, a power supply unit that generates and outputs a current, and a current control unit that controls the output current of the power supply unit; 2. The connection failure detection device according to claim 1, wherein the current control unit controls the power supply unit so that the current flowing through the electrical path connection unit becomes the specified value.

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