JP4450349B2 - Earth leakage detector test circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a test circuit for confirming the operation of an electric leakage detector that detects electric leakage in an electric circuit and outputs an alarm signal.
[0002]
[Prior art]
As shown in FIG. 2, the conventional leakage detector 21 detects the leakage current of the warning circuit 22 with a zero-phase current transformer 23, and the input voltage input from the zero-phase current transformer 23 is previously detected by a sensitivity setting unit 24. The input voltage is converted into a voltage corresponding to the set sensitivity, the input voltage is amplified by the amplifying unit 25, the amplified voltage is compared with a preset set voltage by the comparing unit 26, and an alarm signal is output when the amplified voltage exceeds the set voltage. Is output to inform the outside of the earth leakage by sound or light. The power source of the leakage detection circuit 27 is obtained by stepping down an AC power source by a transformer 28 and rectifying by a rectifier circuit 29 including four diodes D1, D2, D3, and D4 connected to the secondary side of the transformer 28. Power is supplied by a power supply circuit 30 that makes a direct current using a smoothing capacitor C2 connected between output terminals of the circuit 29. Further, the input protection unit 31 protects the circuit from an excessive input voltage. In recent years, the low-pass filter 32 is for removing a high-frequency component because the number of cases in which the leakage detector 21 erroneously detects a leakage due to a high-frequency current mixed into the warning electric circuit 22 from an inverter device or the like is increasing. After the high-frequency component is removed by the low-pass filter 32, the direct-current component is removed by the AC coupling 33 including the capacitor C1 and the resistor R1, and the adjustment elements of the amplifying unit 25 are reduced. The test circuit 34 for confirming the operation of the leakage detection circuit 27 of the leakage detector 21 and the presence or absence of a disconnection failure of the zero-phase current transformer 23 comprises resistors R2 and R3 and a switch 35.
[0003]
[Problems to be solved by the invention]
The power source of the test circuit 34 must be an AC power source because the leakage detection circuit 27 has an AC coupling 33 that removes a DC component. If the power supply of the test circuit 34 is secured from between the secondary side of the transformer 28 and the rectifier circuit 29, the leakage detection circuit 27 does not operate due to the influence of the rectifier circuit 29. Therefore, the transformer 28 has a first secondary winding 28a. Is connected to the rectifier circuit 29, and the second secondary winding 28 b is wound around the transformer 28 to serve as a power source for the test circuit 34. Since the second secondary winding 28b is required, there is a problem that the transformer 28 is enlarged and the manufacturing cost is increased.
[0004]
[Means for Solving the Problems]
In view of the problems of the conventional leakage detector test circuit, the object of the present invention is to provide a leakage detector test circuit that can reduce the manufacturing cost and can be downsized. A zero-phase current transformer that detects the leakage current of the warning circuit, an input protection unit that protects the circuit from excessive input voltage, a sensitivity setting unit that sets the sensitivity of the input voltage, and a low-pass filter that removes high-frequency components An AC coupling that removes a DC component; an amplifier that amplifies the input voltage; and a comparator that compares the amplified voltage with a preset voltage and outputs an alarm signal when the amplified voltage exceeds the preset voltage. A leakage detection circuit, a transformer for stepping down an AC power supply, a rectifier circuit connected to the secondary side of the transformer, a smoothing capacitor connected between the output terminals of the rectifier circuit, and a zero phase Current transformer and leakage detection circuit In order to confirm the operation of the leakage detector composed of a resistor that generates a pseudo-leakage current and a test circuit comprising a switch, the switch provided on the output side of the zero-phase current transformer and the secondary side of the transformer A pseudo-leakage current source is configured by interposing a capacitor between them and a pseudo-leakage current source, and during the test, a pseudo-leakage current is passed from the pseudo-leakage current source to the zero-phase current transformer. It is to confirm the operation of the leakage detection circuit .
[0005]
DETAILED DESCRIPTION OF THE INVENTION
A resistor and a switch are connected in parallel between one output side of the zero-phase current transformer and the input protection unit, and a resistor and a capacitor are connected between the test side of the switch and the secondary side of the transformer to which the power circuit is connected. Are connected in series.
[0006]
【Example】
An embodiment of a test circuit for a leakage detector according to the present invention will be described with reference to the attached drawing of FIG.
[0007]
The leakage detector 1 detects the leakage current of the warning circuit 2 by the zero-phase current transformer 4 connected to the leakage detection circuit 3, and when the input voltage from the zero-phase current transformer 4 is excessive, the input protection unit 5 Is used to protect the leakage detection circuit 3, and then the input voltage input from the zero-phase current transformer 4 is converted into a voltage corresponding to the preset sensitivity preset by the sensitivity setting unit 6. The high frequency component is removed, the direct current component is removed by the alternating current coupling 8 including the capacitor C1 and the resistor R1, the input voltage is amplified by the amplifying unit 9, and the amplified voltage and the preset set voltage are compared by the comparing unit 10. When the amplified voltage exceeds the set voltage, an alarm signal is output, and the leakage is notified to the outside by sound or light.
[0008]
The power supply of the leakage detection circuit 3 is supplied by the power supply circuit 11. The power supply circuit 11 steps down the AC power supply by the transformer 12, rectifies it by the rectifier circuit 13 including four diodes D 1, D 2, D 3, and D 4 connected to the secondary side of the transformer 12, and outputs the rectifier circuit 13. The signal is smoothed and converted to direct current by a smoothing capacitor C2 connected between the terminals.
[0009]
The test circuit 14 for confirming the operation of the leakage detection circuit 3 of the leakage detection detector 1 and the presence or absence of a disconnection failure of the zero-phase current transformer 4 includes resistors R2 and R3 and a switch 15 for switching.
[0010]
The resistor R2 and the switch 15 are connected in parallel between one output side of the zero-phase current transformer 4 and the input protection unit 5, and the switch 15 is normally connected to the monitoring side. One of the test side of the switch 15 and the secondary side of the transformer 12 is connected with a resistor R3 and a capacitor C3 interposed in series. When testing the leakage detection circuit 3, the switch 15 is switched to the test side and the test is performed.
[0011]
By interposing the capacitor C3, the influence of the direct current potential can be removed and the test can be performed normally.
[0012]
In this embodiment, the rectifier circuit 13 is full-wave rectified by a diode bridge, but there is no problem even with half-wave rectification, and the rectifier circuit is not limited.
[0013]
【The invention's effect】
As described above, the leakage detector test circuit according to the present invention includes a zero-phase current transformer that detects a leakage current in a warning circuit, an input protection unit that protects the circuit from an excessive input voltage, and sensitivity of the input voltage. A sensitivity setting unit to set, a low-pass filter to remove high frequency components, an AC coupling to remove DC components, an amplification unit to amplify the input voltage, and the amplified voltage are set by comparing the preset voltage with the preset voltage. Between the leakage detection circuit consisting of a comparator that outputs an alarm signal when the voltage is exceeded, the transformer that steps down the AC power supply, the rectifier circuit connected to the secondary side of the transformer, and the output terminal of the rectifier circuit A leakage detection circuit composed of a power circuit composed of a smoothing capacitor connected to the circuit, and a test circuit composed of a resistor and a switch for generating a pseudo leakage current for confirming the operation of the zero-phase current transformer and the leakage detection circuit. In a vessel Connected by a single connecting line by interposing a capacitor between the switch provided on the output side of the residual current transformer and the secondary side of the transformer, it constitutes a pseudo-leakage current source of the test circuit, during the test By confirming the operation of the zero-phase current transformer and the leakage detection circuit by sending a pseudo-leakage current from the pseudo-leakage current source to the zero-phase current transformer, it is possible to increase the capacity of the capacitor without increasing the number of secondary windings of the transformer. As the transformer is downsized, the leakage detector itself can be reduced in size and weight, and the connection line between the leakage detection circuit and the secondary side of the transformer can be reduced. This has an excellent effect of reducing the number of wires and simplifying the circuit pattern.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a leakage detector according to the present invention.
FIG. 2 is a circuit diagram of a conventional leakage detector.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Leakage detector 2 Warning circuit 3 Leakage detection circuit 4 Zero phase current transformer 5 Input protection part 6 Sensitivity setting part 7 Low pass filter 8 AC coupling 9 Amplification part 10 Comparison part 11 Power supply circuit 12 Transformer 13 Rectification circuit 14 Test circuit 15 Switch C1 Capacitor C2 Smoothing capacitor C3 Capacitor D1 Diode D2 Diode D3 Diode D4 Diode R1 Resistor R2 Resistor R3 Resistor

Claims (1)

A zero-phase current transformer for detecting a leakage current of a warning circuit, an input protection unit for protecting the circuit from an excessive input voltage, a sensitivity setting unit for setting the sensitivity of the input voltage, and a low-pass filter for removing a high-frequency component A comparison between the AC coupling for removing the DC component, the amplifying unit for amplifying the input voltage, and comparing the amplified voltage with a preset voltage and outputting an alarm signal when the amplified voltage exceeds the preset voltage. Power supply comprising: a leakage detecting circuit comprising: a transformer; a transformer for stepping down an AC power supply; a rectifier circuit connected to a secondary side of the transformer; and a smoothing capacitor connected between output terminals of the rectifier circuit In the leakage detector comprising a circuit and a test circuit comprising a switch and a resistor for generating a pseudo leakage current for confirming the operation of the zero-phase current transformer and the leakage detection circuit, the zero-phase current Output Connected by a single connecting line by interposing a capacitor between the secondary side of the switch and the transformer provided to constitute a pseudo leakage current source of the test circuit, the pseudo leakage current source during test A test circuit for a leakage detector, wherein a pseudo leakage current is supplied to the zero-phase current transformer to check the operation of the zero-phase current transformer and the leakage detection circuit.

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