Fault detection circuit and circuit breaker

Abstract

To provide a connection failure detection circuit and a circuit breaker for detecting a poor connection even at voltage value where generated potential difference does not reach operating voltage of a photocoupler and unaffected by electric path current.SOLUTION: A connection failure detection circuit 2 includes: a first differential amplifier 21 which detects generated potential difference at an individual connection terminal 6 of a terminal part 10; a second differential amplifier 22 which combines the first differential amplifiers 21 installed in any two connection terminals 6 with mutually different polarity on a same electric circuit and extracts difference of their outputs; and a determination part 23 which determines the presence of a poor connection when the output voltage of the second differential amplifier 22 exceeds a certain value. A circuit breaker 1 includes an output part 3 which generates an interruption signal according to the output of the determination part 23. At occurrence of poor connection, the circuit breaker 1 executes shut-off operation.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a connection failure detection circuit that detects a connection failure in an electric path connection portion, and a circuit breaker provided with the connection failure detection circuit. [Background technology]

[0002] The terminals of circuit breakers are commonly configured so that the crimp terminal on the wire side is pressed against a washer by a terminal screw to establish mechanical and electrical connections. With this type of terminal, if the terminal screw becomes loose, the contact between the washer and the crimp terminal becomes unstable, causing an arc discharge and resulting in overheating. As a countermeasure to this, there are circuit breakers that detect loosening of the terminal screw and cut off the electric circuit. For example, in Patent Document 1, when a predetermined potential difference occurs between the terminal screw and the terminal base, it is determined that a connection failure has occurred and the circuit breaker performs a cut-off operation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-243666 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technology of the above-mentioned Patent Document 1 turns on the photocoupler by the potential difference generated at the connection terminal, and detects the connection failure by the output. Therefore, there was a problem that it could not be detected unless the potential difference at the detection part reached the operating voltage of the photocoupler. In addition, since the potential difference to be detected changed depending on the magnitude of the electric circuit current, there was variation in sensitivity.

[0005] In view of the above problems, the present invention aims to provide a connection failure detection circuit and a circuit breaker that can detect a connection failure even when the generated potential difference is a voltage value that does not reach the operating voltage of the photocoupler, and that is not affected by the circuit current. [Means for solving the problem]

[0006] In order to solve the above problem, the invention of claim 1 is a poor connection detection circuit that detects poor connections in a terminal part having a plurality of connection terminals that electrically connect an electric circuit, the electric circuit being composed of a plurality of electric circuit components of different polarities, and each connection terminal being characterized in having a potential difference detection circuit that detects a potential difference generated at the connection terminal, a differential amplification circuit that combines the potential difference detection circuits provided on any two connection terminals of the same electric circuit that have different polarities to extract the difference in their outputs, and a judgment unit that judges that a poor connection has occurred when the output voltage of the differential amplification circuit exceeds a certain value. With this configuration, the system judges the occurrence of a connection failure based on the relative difference between the two combined connection terminals, rather than the potential difference within the terminals, and determines that a connection failure has occurred if a potential difference of a certain value or more occurs between the connection terminals. This makes it possible to detect a connection failure without being affected by the current in the circuit. In addition, because the differential amplifier circuit extracts the potential difference, it is possible to detect it even if the voltage does not reach the voltage that turns on the photocoupler as in the past, making it possible to detect a connection failure at an early stage.

[0007] The invention of claim 2 is characterized in that, in the configuration described in claim 1, the electrical path is composed of three electrical path components, the terminal section has three connection terminals, each connection terminal is provided with a potential difference detection circuit, and the terminal section has three differential amplification circuits that combine two different outputs of the three potential difference detection circuits and extract the difference between the outputs, and the judgment section judges that a connection failure has occurred when the output voltage of at least one differential amplification circuit exceeds a certain value. According to this configuration, if a connection failure occurs in one of the three connection terminals of the terminal section and the potential difference becomes larger than that of the other connection terminals, this is detected. Therefore, even if the terminal section is composed of three terminals, the connection failure can be reliably detected.

[0008] The invention of claim 3 is characterized in that, in the configuration described in claim 1, the electrical path is composed of two electrical path components, the terminal portion has two connection terminals, each connection terminal is provided with a potential difference detection circuit, and there is one differential amplification circuit that extracts the difference between the outputs of the two potential difference detection circuits, and the judgment portion judges that a connection failure has occurred when the output voltage of the differential amplification circuit exceeds a certain value. According to this configuration, the terminal unit consisting of two connection terminals determines that a connection failure has occurred when a difference occurs in the potential difference between the two connection terminals, so that a connection failure can be detected with a simple configuration.

[0009] The invention of claim 4 is a circuit breaker whose primary and secondary terminal sections are composed of three connection terminals, wherein at least one of the primary and secondary terminal sections is provided with the poor connection detection circuit described in claim 2, and has an output section which outputs a cut-off signal when the poor connection detection circuit determines that a poor connection has occurred, and performs a cut-off operation in response to the cut-off signal. According to this configuration, if a connection failure occurs in the terminal section, it is detected from the relative voltage difference between the terminals and a cut-off operation is performed. Therefore, the detection operation of the connection failure does not vary depending on the magnitude of the current in the circuit.

[0010] The invention of claim 5 is a circuit breaker in which the primary and secondary terminal portions are composed of two connection terminals, and the connection failure detection circuit described in claim 3 is provided in at least one of the primary and secondary terminal portions, and the circuit breaker has an output portion that outputs a disconnection signal when the connection failure detection circuit determines that a connection failure has occurred, and performs a disconnection operation in response to the disconnection signal. According to this configuration, if a connection failure occurs in the terminal section, it is detected from the relative voltage difference between the terminals and a cut-off operation is performed. Therefore, the detection operation of the connection failure does not vary depending on the magnitude of the current in the circuit. Effect of the Invention

[0011] According to the connection failure detection circuit and circuit breaker of the present invention, the occurrence of a connection failure is judged from the relative difference between the two combined connection terminals, not from the potential difference within the terminals, and if a potential difference of a certain value or more occurs between the connection terminals, it is judged to have occurred. Therefore, a connection failure can be detected without being affected by the current in the circuit. In addition, since the differential amplifier circuit extracts the potential difference, it is possible to detect it even if the voltage does not reach the voltage that turns on the photocoupler as in the conventional case, and a connection failure can be detected at an early stage. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is an explanatory diagram of a circuit breaker equipped with a connection failure detection circuit. [Diagram 2] FIG. 4 is an explanatory diagram showing a configuration of a connection terminal. [Diagram 3] 11 is an explanatory diagram showing another embodiment of a connection failure detection circuit and a circuit breaker. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is an explanatory diagram of a circuit breaker equipped with a connection failure detection circuit according to the present invention. 1 is a circuit breaker, 2 is a connection failure detection circuit, and shows a configuration in which the connection failure detection circuit 2 is provided on the secondary terminal of the circuit breaker 1. The circuit breaker 1 shows a case where the electric circuit member is configured as a three-wire electric circuit, and shows a configuration used for a single-phase three-wire electric circuit (hereinafter simply referred to as an "electric circuit") 4. The connection failure detection circuit 2 is attached to a circuit board (not shown) and is built into the housing H of the circuit breaker 1.

[0014] The circuit breaker 1 has a terminal section 10 which constitutes a primary side terminal 11 and a secondary side terminal 12 which electrically connect an electric circuit 4, and has three connection terminals, which are voltage poles L1 and L2, and a neutral pole N. A contact unit 13 for opening and closing an electric circuit spanning between a primary terminal 11 and a secondary terminal 12, and a switching mechanism unit (not shown) for interrupting the contact unit 13 are assembled inside the housing H of the circuit breaker 1. A handle (not shown) for opening and closing the contact unit 13 is also provided on the top of the housing H. However, for the purpose of explanation, Fig. 1 shows the inside of the housing H as seen through.

[0015] The connection failure detection circuit 2 includes first differential amplifiers 21 (21a, 21b, 21c) as three potential difference detection circuits connected to each connection terminal of the secondary side terminal 12, second differential amplifiers 22 (22a, 22b, 22c) which are three differential amplification circuits formed by forming three different pairs of the first differential amplifiers 21 and inputting the outputs of each of the formed pairs, and a judgment unit 23 which judges a connection failure from the output voltage of the second differential amplifier 22. The circuit breaker 1 includes an output unit 3 that outputs a tripping signal to cause the circuit breaker 1 to perform a tripping operation when the determination unit 23 determines that a connection failure has occurred. In response to this tripping signal, the opening and closing mechanism unit of the circuit breaker 1 performs a tripping operation.

[0016] 2 shows the configuration of the connection terminal 6 of the secondary side terminal 12 to which the first differential amplifier 21 is connected. Note that the configuration of the connection terminal 6 itself is common to the individual connection terminals 6 of the primary side terminal 11 and the secondary side terminal 12. The connection terminal 6 has a washer 61, a terminal screw 62, and a nut 63, and is connected to a crimp terminal 65 fixed to the end of an electric wire 62 which is an electric circuit. In the first differential amplifier 21, of a pair of positive and negative input terminals 20a, 20b, the positive input terminal 20a is connected to a washer 61, and the negative input terminal 20b is connected to a crimp terminal 65. In this way, the potential difference between the washer 61 and the crimp terminal 65 of the connection terminal 6 is input.

[0017] The portion where the voltage is detected may be between the washer 61 and the nut 63, or between the washer 61 and the terminal screw 62. When the connection failure detection circuit 2 is provided in the primary side terminal 11, the portions to which the pair of positive and negative input terminals of the first differential amplifier 21 are connected are reversed. In addition, since the terminal unit 10 of the circuit breaker 1 is configured with three terminals, the circuit breaker 1 has three first differential amplifiers 21. And since there are three combinations of the first differential amplifiers 21 that form pairs, the number of second differential amplifiers 22 is also three in order to cover all the combinations.

[0018] The connection failure detection circuit 2 configured as above operates as follows. For example, the amplification degree of the first differential amplifier 21 and the second differential amplifier 22 is 100, and the threshold voltage of the determination unit 23 is 5V in absolute value. If the potential difference between the washer 61 and the crimp terminal 65 is 10mV in a normal connection state, the output of the first differential amplifier 21 is 1V. However, because this value is the value for a normal connection state, all three terminals are approximately 10 mV, and the outputs of the first differential amplifier 21 are all the same voltage of 1 V. Therefore, no potential difference occurs at the differential inputs of the second differential amplifier 22, and the output voltage is close to 0 V even if the amplification degree is 100. Therefore, the judgment unit 23 does not reach the judgment threshold of 1 V, and does not judge that a connection failure has occurred.

[0019] In addition, even if the current in the electric circuit 4 increases and the detected potential difference of the first differential amplifier 21 of the L1 terminal increases to 20 mV, the detected potential difference of the connection terminal 6 of the other poles also increases due to the increase in current, so the operating input of the second differential amplifier 22 continues to be close to 0 V and the output voltage does not change significantly. Therefore, it is not determined that a connection failure has occurred.

[0020] However, for example, if a connection failure occurs in the connection terminal 6 of the L2 electrode and the detected potential difference changes from 10 mV to 20 mV, a difference of 10 mV occurs with the other connection terminals 6. In this case, the outputs of the first differential amplifiers 21a and 21b of the L1 and N poles are 1V, whereas a difference of 20mV occurs in the differential inputs of the first differential amplifier 21c of the L2 pole, so that the output is 2V. Since a difference of 1 V occurs in the differential inputs of both second differential amplifiers 22a, 22c to which this voltage is input, the absolute value of the output voltage greatly exceeds the set threshold value of 5 V. Therefore, the determination unit 23 determines that a connection failure has occurred and outputs a predetermined signal to the output unit 3, and upon receiving this signal, the output unit 3 outputs a cutoff signal, causing the circuit breaker 1 to perform a cutoff operation.

[0021] In this way, the occurrence of a connection fault is judged based on the relative difference between the two combined connection terminals 6, not on the potential difference within the terminals, and if a potential difference of a certain value or more occurs between the connection terminals 6, it is judged to be the occurrence of a connection fault. Therefore, a connection fault can be detected without being affected by the current in the circuit. Also, because the second differential amplifier 22 extracts the potential difference, it is possible to detect it even if the voltage does not reach the voltage that turns on the photocoupler as in the past, and a connection fault can be detected at an early stage. Furthermore, when a connection failure occurs in any one of the connection terminals 6 of the terminal section 10 consisting of three terminals and the potential difference becomes larger than that of the other terminals, this is detected, so that the connection failure can be reliably detected even if the terminal section 10 is composed of three terminals.

[0022] 3 shows a circuit breaker 1a having two terminals, a primary terminal 11 and a secondary terminal 12, which are the terminal unit 10. Similarly to the above embodiment, the secondary terminal 12 is provided with a connection failure detection circuit 2. In the case of a two-terminal circuit breaker 1a, since there are two first differential amplifiers 21 on one terminal section 10, only one second differential amplifier 22 to which the output of the first differential amplifiers 21 is input is sufficient, resulting in a configuration including three differential amplifiers in total. Also, the determination section 23 determines a connection failure based only on the output voltage of this one second differential amplifier 22. The determination threshold is the same as in the above embodiment. In this way, in the terminal section 10 consisting of two terminals, if a difference occurs in the potential difference between the two connection terminals 6, it is determined that a connection failure has occurred, so that a connection failure can be detected with a simple configuration.

[0023] In the above embodiment, the connection failure detection circuit 2 is provided at the secondary terminal 12, but it may be provided at the primary terminal 11, or at both. In addition, although the case where the connection failure detection circuit 2 is assembled in the circuit breaker 1 has been described, it can also be applied to, for example, a terminal block that does not have a breaking mechanism, and can be made to function effectively by arranging a sounding unit such as a buzzer so that it sounds when a connection failure occurs. Furthermore, although a configuration for detecting the potential difference between the crimp terminal 65 and the washer 61 has been described, the present invention can also be applied to other terminal configurations, such as quick-connect terminals, by detecting the potential difference between the inserted electric wire and the terminal fitting. [Explanation of symbols]

[0024] 1, 1a·· circuit breaker, 2·· connection failure detection circuit, 3·· output section, 4·· electrical circuit (electrical circuit component), 6·· connection terminal, 10·· terminal section, 11·· primary side terminal, 12·· secondary side terminal, 13·· contact section, 21·· first differential amplifier (potential difference detection circuit), 22·· second differential amplifier (differential amplification circuit), 23·· judgment section.

Claims

1. A connection failure detection circuit for detecting a connection failure of a terminal portion having a plurality of connection terminals that electrically connect an electric circuit, The electric path is composed of a plurality of electric path members having different polarities, a potential difference detection circuit for detecting a potential difference generated at each of the connection terminals; a differential amplifier circuit that combines the potential difference detection circuits provided on any two of the connection terminals having different polarities of the same electric path and extracts a difference between the outputs of the potential difference detection circuits; a determination unit that determines that a connection failure has occurred when an output voltage of the differential amplifier circuit exceeds a certain value.

2. the electric path is composed of three electric path members, the terminal portion has three connection terminals, and each connection terminal is provided with the potential difference detection circuit; the three differential amplifier circuits each combining two different outputs of the three potential difference detection circuits and extracting a difference between the outputs; 2. The connection failure detection circuit according to claim 1, wherein the determination unit determines that a connection failure has occurred when an output voltage of at least one of the differential amplifier circuits exceeds a certain value.

3. the electric path is composed of two electric path members, the terminal portion has two connection terminals, and each connection terminal is provided with the potential difference detection circuit; a differential amplifier circuit for extracting a difference between outputs of the two potential difference detection circuits; 2. The connection failure detection circuit according to claim 1, wherein the determination unit determines that a connection failure has occurred when the output voltage of the differential amplifier circuit exceeds a certain value.

4. A circuit breaker in which the terminal portions on the primary side and the secondary side are composed of three connection terminals, The connection failure detection circuit according to claim 2 is provided on at least one of the terminals on the primary side and the secondary side, an output section that outputs a disconnection signal when the connection failure detection circuit determines that a connection failure has occurred; A circuit breaker that performs a breaking operation in response to the breaking signal.

5. A circuit breaker in which the terminal portions on the primary side and the secondary side are composed of two connection terminals, At least one of the terminals on the primary side and the secondary side is provided with the connection failure detection circuit according to claim 3, an output section that outputs a disconnection signal when the connection failure detection circuit determines that a connection failure has occurred; A circuit breaker which performs a breaking operation in response to the breaking signal.

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