JP2006310165A - Ground-fault interruptor having screw loosening sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ground-fault interruptor having a function of interrupting the electric path when a terminal loosens. <P>SOLUTION: In the ground-fault interruptor, a pressure-sensitive sensor 8 to detect the loosening is screw fastened to the terminal together with a crimping terminal 23, and a loosening detection circuit 9 to interrupt the electric path 4 by judging the loosening from a detection signal of the pressure-sensitive sensor 8. The pressure-sensitive sensor 8 is formed by mixing carbon powder with glass fiber and solidifying the mixture with an epoxy resin, and pressing the solidified mixture so that it has a low resistance. The loosening detection circuit 9 has a comparison circuit 17 to compare an output current of the pressure-sensitive sensor 8 with a reference value, judges when the output current falls below the reference value as an occurrence of the loosening and outputs an interrupting signal to operate a withdrawal device 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an earth leakage breaker, and more particularly to an earth leakage breaker that can detect looseness of a terminal as a function other than leakage detection.

The conventional earth leakage breaker is a zero-phase current transformer that detects the zero-phase current of the electric circuit, an earth-leakage detection circuit that outputs a breaking signal when the detected zero-phase current exceeds a predetermined value, and an operation for breaking the electric circuit by receiving the breaking signal When the current detected by the zero-phase current transformer exceeds a predetermined value, it is determined that leakage has occurred and the circuit is interrupted (see, for example, Patent Document 1).
On the other hand, there is a pressure-sensitive sensor that utilizes the electric resistance change characteristic during pressurization of a carbon molded body (pressure-sensitive resistor) obtained by solidifying carbon powder with a resin (see, for example, Patent Document 2).

JP 2001-314031 A JP 2000-82608 A

The above-mentioned conventional earth leakage circuit breaker does not have a function of detecting looseness of the input terminal or output terminal, and heat generation of the terminal caused by loosening of the terminal screw tightening, and further, burnout caused by the heat generation, No measures were taken against the fire.
Accordingly, an object of the present invention is to provide an earth leakage breaker having a function of interrupting an electric circuit when a terminal is loosened by utilizing the properties of the carbon molded body.

In order to solve the above-mentioned problem, the invention described in claim 1 is directed to a zero-phase current transformer for detecting a leakage, and to detect that a leakage has occurred when the detected zero-phase current exceeds a predetermined reference value. An earth leakage breaker having an earth leakage detection circuit for outputting a signal and an interruption means for interrupting an electric circuit in response to the interruption signal, and detecting the looseness of at least one of the input terminal and the output terminal And when the looseness is detected, the blocking means is operated to cut off the electric circuit.
With this configuration, when the terminal is loosened, the electric circuit is cut off, so that it is possible to prevent the terminal from being heated due to the loosening and the occurrence of a fire.

According to a second aspect of the present invention, in the first aspect of the present invention, the looseness detecting means detects a looseness in response to an output signal of the pressure-sensitive sensor that detects the screw tightening pressure of the terminal and the pressure sensor. It is characterized by comprising.
With this configuration, the tightening pressure of the terminal screw is detected, so that looseness can be reliably detected.

According to a third aspect of the present invention, in the invention of the second aspect, the pressure-sensitive sensor has a low electrical resistance in a pressurized state attached to a terminal and screwed, and a high resistance in a loosely decompressed state. It is a carbon molded body formed by containing carbon powder in a resin, and the looseness of a terminal is detected by a change in electric resistance of the carbon molded body.
With this configuration, the pressure sensor has a simple configuration, and the looseness of the terminal can be detected with a simple configuration.

  According to the present invention, when the terminal is loosened, the electric circuit is cut off, so that it is possible to prevent the terminal from being heated and the fire due to the loosening. Moreover, the pressure sensor has a simple configuration, and can detect the looseness of the terminal with a simple configuration.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing an example of an earth leakage breaker according to the present invention, where 1 is an input terminal for connecting a power supply 12, 2 is an output terminal to which a load is connected, and 3 is between the input terminal 1 and the output terminal 2. The zero-phase current transformer 5 detects the zero-phase current of the electric circuit 4, 5 is an IC leakage detection circuit that outputs a cut-off signal when a leakage is detected, 6 is an open / close contact that opens and closes the electric circuit 4, and 7 is an open / close contact 6. A tripping device for opening the terminal, 8 a pressure-sensitive sensor for detecting the looseness of the terminal, 9 for a looseness detection circuit for outputting a cut-off signal when the looseness of the terminal is detected, and 10 for a power supply circuit for supplying power to the looseness detection circuit 9 It is. The switching contact 6 and the tripping device 7 constitute a blocking means.

  The looseness detection circuit 9 includes a signal input unit 15 for connecting the pressure sensor 8 and a photocoupler 16 for electrically separating the input signal from the electric circuit. The pressure sensor 8 is configured to be driven by a power supply voltage, and the tip of the photocoupler 16 is connected to the other electric circuit 4 where the pressure sensor 8 is not provided so as to be connected between the electric circuits 4. A trip circuit drive circuit 18 for operating the trip device 7 has a comparison circuit 17 that receives a signal from the photocoupler 16 and performs a comparison operation with a reference value, and a thyristor 18 a that is turned on by the output of the comparison circuit 17. have.

  The pressure-sensitive sensor 8 is a carbon molded body in which carbon powder is combined with glass fiber and hardened with an epoxy resin, and is formed into a disk shape as shown in a perspective view of an earth leakage circuit breaker with the terminal portion of FIG. 2 disassembled. It has an insertion hole 8a for inserting a terminal screw and a protruding piece 8b for connecting a lead wire. This carbon molded body is formed, for example, by mixing carbon and an epoxy resin in a weight ratio of 86:14. The carbon molded body thus formed is in a low resistance state when a pressure is applied, and a current corresponding to the applied voltage is applied.

  The pressure sensor 8 thus formed is attached to the terminal as shown in FIG. In FIG. 2, 20 is a circuit breaker housing, 21 is an intermediate plate that pressurizes the pressure sensor 8, 22 is a terminal screw, 23 is a crimp terminal for connecting the power cord 23a to the terminal, and 24 is in the housing 20. A lead wire 25 for sending a signal to the looseness detection circuit 9 (not shown) is a terminal board constituting an electric circuit. The intermediate plate 21 has a pair of protrusions 21 a that are inserted into a pair of holes 25 a provided on the left and right of the terminal screw insertion holes of the terminal plate 25. The protrusions 21 a are formed slightly longer than the thickness of the terminal plate 25. ing.

The pressure-sensitive sensor 8 is installed at the lowermost part of the terminal and is pressed by the intermediate plate 21 when tightened by the terminal screw 22. FIGS. 3A and 3B are explanatory views of a longitudinal section of the terminal portion thus attached. FIG. 3A shows a state in which the terminal screw is tightened, and FIG. 3B shows a state in which the terminal screw is loosened.
In the clamped state, the protrusion 21 a of the intermediate plate 21 is directly pressed by the terminal screw 22 through the crimp terminal 23, and is pressed without receiving pressure from the terminal plate 25. Thereafter, when the terminal screw 22 is loosened, as shown in (b), the projection 21a lifts the crimp terminal 23 and the like, the intermediate plate 21 is lifted, and the pressure sensor 8 is not pressurized. Since the pressure sensor 8 is slightly crushed and deformed when pressed by screw tightening, the stress is not dispersed and local stress is not generated and broken.

  Next, the operation of the earth leakage circuit breaker having the above circuit will be described. First, the operation at the time of occurrence of electric leakage, which is a basic operation, will be described. The current detected by the zero phase current transformer 3 is input to the leakage detection circuit 5. The leakage detection circuit 5 determines that leakage has occurred when the detected current value is equal to or greater than a preset reference value, and outputs a cutoff signal from the output terminal 5a. By this interruption signal, the trip device 7 performs a trip operation, the switching contact 6 is opened, and the electric circuit 4 is interrupted.

  When looseness occurs in the terminal to which the pressure sensor 8 is attached, the operation is as follows. In a state where the terminal screw 22 is normally screwed and not loosened, the pressure-sensitive sensor 8 is in a low resistance state because it is pressurized. Therefore, when a power supply voltage is applied, a current always flows, the photocoupler 16 is in an on state, and the input of the comparison circuit 17 is a voltage smaller than a reference value. Therefore, the comparison circuit 17 has no output signal, and the trip device driving circuit 18 does not operate.

  However, when the screw is loosened, the pressure of the pressure sensor 8 is released and the resistance state is increased, and no current flows. For this reason, the photocoupler 16 is turned off, the input voltage to the comparison circuit 17 becomes larger than the reference value, and the comparison circuit 17 outputs a signal. In response to this signal, the thyristor 18a is turned on, the trip device drive circuit 18 outputs a trip signal, and the trip device 7 operates. Accordingly, the switching contact 6 is opened and the electric circuit 4 is interrupted.

  Thus, since the electric circuit is interrupted when the terminal is loosened, the terminal can be prevented from being heated or fired due to the loosening. In addition, since the screw tightening pressure of the terminal is detected, it is possible to reliably detect the looseness, and the pressure sensor has a simple configuration, and the looseness of the terminal can be detected with a simple configuration.

In the above embodiment, since the pressure-sensitive sensor 8 is installed only on one input terminal 1, it cannot be blocked against the looseness of the other terminals. The looseness of the terminal can be detected and blocked. In this case, the looseness detection circuit 9 can be dealt with by providing, for example, a signal input unit 15 and a photocoupler 16 for detecting the sensor current in accordance with the number of pressure-sensitive sensors and connecting them in parallel to the input of the comparison circuit 17.
The pressure sensor 8 is pressurized by the tightening pressure of the terminal screw 22. However, the pressure sensor 8 may be pressed with a cushioning material such as a rubber material interposed therebetween. The pressure sensor 8 is not damaged.

It is a circuit diagram showing an example of an embodiment of a ground-fault circuit breaker according to the present invention. It is an isometric view explanatory drawing of the earth-leakage circuit breaker of the state which decomposed | disassembled the terminal part. FIGS. 3A and 3B are longitudinal sectional explanatory views of the terminal portion of FIG. 2, in which FIG. 2A shows a state in which the terminal screw is tightened, and FIG.

Explanation of symbols

  1 .... Input terminal, 2 .... Output terminal, 4 .... Electric circuit, 5 .... Leakage detection circuit, 6 .... Open / close contact, 7 .... Trip device, 8 .... Pressure sensor, 9 .... Looseness detection circuit , 15... Signal input unit, 18 .. trip device driving circuit.

Claims (3)

A zero-phase current transformer for detecting a leakage, a leakage detection circuit for determining that a leakage has occurred when the detected zero-phase current exceeds a predetermined reference value, and outputting a cutoff signal; An earth leakage breaker having a breaking means for breaking operation,
An earth leakage circuit breaker comprising: a looseness detecting means for detecting a looseness of at least one of the input terminal and the output terminal, and when the looseness is detected, the electric circuit is cut off by operating the interruption means. 2. The earth leakage breaker according to claim 1, wherein the looseness detecting means comprises a pressure sensitive sensor for detecting a screw tightening pressure of the terminal and a looseness detecting circuit for detecting looseness in response to an output signal of the pressure sensitive sensor. A pressure-sensitive sensor is a carbon molded body that is molded by adding carbon powder to a resin so that the electrical resistance decreases in a pressurized state attached to a terminal and screwed, and becomes high in a loose reduced pressure state. The earth leakage circuit breaker according to claim 2, wherein looseness of the terminal is detected by a change in electric resistance of the carbon molded body.

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