JP7675591B2 - Fault detection circuit and circuit breaker - Google Patents

Description

The present invention relates to a connection failure detection circuit that detects connection failures in an electrical circuit connection, and a circuit breaker equipped with a connection failure detection circuit.

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 is a circuit breaker that detects the loosening of a terminal screw and cuts off the electric path. 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 cutoff operation.

JP 2012-243666 A

However, the technology in Patent Document 1 detects poor connection by turning on the photocoupler using the potential difference generated at the connection terminal and detecting the poor connection using the output. This causes a problem in that the detection is not possible unless the potential difference at the detection site reaches the operating voltage of the photocoupler. In addition, the potential difference detected changes depending on the magnitude of the circuit current, resulting in variation in sensitivity.

In view of these problems, the present invention aims to provide a circuit and 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 is not affected by the circuit current.

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 portion having a plurality of connection terminals that electrically connect an electric path, the electric path being composed of a plurality of electric path components of different polarities, and each connection terminal being provided with 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 path 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 occurrence of a connection failure is judged from the relative difference between the two connection terminals, not 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 be a connection failure. Therefore, a connection failure can be detected 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, and a connection failure can be detected at an early stage.

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 of which is provided with a potential difference detection circuit, and 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, so that a connection failure can be reliably detected even if the terminal section is composed of three terminals.

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 section 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.

The invention of claim 4 is a circuit breaker whose primary and secondary terminal portions are composed of three connection terminals, wherein at least one of the primary and secondary terminal portions is provided with the connection failure detection circuit described in claim 2, and wherein when the connection failure detection circuit determines that a connection failure has occurred, the circuit breaker has an output portion which outputs a disconnection signal, 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.

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 which 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.

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, rather than 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. 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, and connection failures can be detected at an early stage.

FIG. 1 is an explanatory diagram of a circuit breaker equipped with a connection failure detection circuit. FIG. 4 is an explanatory diagram showing a configuration of a connection terminal. 11 is an explanatory diagram showing another embodiment of a connection failure detection circuit and a circuit breaker. FIG.

The present invention will now be described in detail with reference to the accompanying drawings, in which: 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 the circuit breaker 1 is provided with the connection failure detection circuit 2 at its secondary terminal.
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 here 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 incorporated in the housing H of the circuit breaker 1.

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 which has three connection terminals, namely, L1 pole and L2 pole which are voltage poles, and an N pole which is a neutral pole.
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.

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 for causing 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.

2 shows the configuration of the connection terminal 6 of the secondary terminal 12 to which the first differential amplifier 21 is connected. The configuration of the connection terminal 6 itself is common to the individual connection terminals 6 of the primary terminal 11 and the secondary 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 manner, the potential difference between the washer 61 and the crimp terminal 65 of the connection terminal 6 is input.

The voltage may be detected 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 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.

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 5 V in absolute value. If the potential difference between the washer 61 and the crimp terminal 65 is 10 mV in a normal connection state, the output of the first differential amplifier 21 is 1 V.
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 determination unit 23 does not reach the determination threshold of 1 V, and does not determine that a connection failure has occurred.

In addition, even if the current in the circuit 4 increases and the detected potential difference of the first differential amplifier 21 at the L1 terminal increases to, for example, 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.

However, for example, if a connection failure occurs in the connection terminal 6 of the L2 pole 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, and the circuit breaker 1 performs a cutoff operation.

In this way, the occurrence of a connection failure is judged from the relative difference between the two combined connection terminals 6, not from 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 a connection failure. Therefore, a connection failure 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 conventional method, and a connection failure can be detected at an early stage.
When a connection defect 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 defect can be reliably detected even if the terminal section 10 is composed of three terminals.

3 shows a circuit breaker 1a in which the terminal section 10 is composed of two terminals, a primary terminal 11 and a secondary terminal 12. 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 required, resulting in a configuration including three differential amplifiers in total. The determination section 23 determines a connection failure based only on the output voltage of this single 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.

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 the primary terminals.
In addition, although the case where the connection failure detection circuit 2 is assembled in the circuit breaker 1 has been described, the circuit breaker 1 can also be applied to a circuit that does not have a breaking mechanism, such as a terminal block, and the circuit breaker can be made to function effectively by arranging a sounding unit such as a buzzer so that the sounding unit 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.

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 (5)

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. 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. 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. 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. 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 that performs a breaking operation in response to the breaking signal.

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