JP2002159134A - Test circuit for leakage detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a test circuit for a leakage detector which can reduce the manufacturing cost and dimensions of the leakage detector. SOLUTION: A parallel circuit comprising a resistor R2 and a switch 15 is connected between an output side of a zero-phase current transformer 4 and an input protection unit 5. A series circuit comprising a resistor R3 and a capacitor C3 is connected between the test side of the switch 15 and a secondary side of a transformer 12 to which a power supply circuit 11 is connected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a test circuit for confirming the operation of a leakage detector which detects a leakage in an electric circuit and outputs an alarm signal.

[0002]

2. Description of the Related Art As shown in FIG. 2, a conventional leakage detector 21 detects a leakage current of a warning circuit 22 by a zero-phase current transformer 23, and detects an input voltage input from the zero-phase current transformer 23. The setting unit 24 converts the input voltage into a voltage corresponding to a preset sensitivity, amplifies the input voltage by an amplifier 25, compares the amplified voltage with a preset voltage by a comparator 26,
When the amplified voltage exceeds the set voltage, it outputs an alarm signal and notifies the outside of the earth leakage by sound or light. The power supply of the leakage detection circuit 27 is obtained by stepping down an AC power supply by a transformer 28 and rectifying the AC power by a rectifier circuit 29 including four diodes D1, D2, D3, and D4 connected to the secondary side of the transformer 28. The power is supplied by a power supply circuit 30 that converts the direct current by a smoothing capacitor C2 connected between the output terminals of the circuit 29. Further, the input protection section 31 protects the circuit from an excessive input voltage. The low-pass filter 32 is for removing high-frequency components 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 circuit 22 from an inverter device or the like has increased in recent years. After removing the high-frequency component 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 number of adjustment elements of the amplifier 25 is reduced. A test circuit 34 for confirming the operation of the leakage detection circuit 27 of the leakage detector 21 and for confirming the presence or absence of a disconnection failure of the zero-phase current transformer 23 includes resistors R2 and R3 and a switch 35.

[0003]

The power supply of the test circuit 34 is supplied to an earth leakage detecting circuit 27 by an AC coupling 3 for removing a DC component.
Because of the three, it must be an AC power supply. Transformer 2
If the power supply of the test circuit 34 is secured between the secondary side of the rectifier circuit 29 and the rectifier circuit 29, the leakage detector circuit 27 does not operate due to the influence of the rectifier circuit 29, so the first secondary winding 28a is wound around the transformer 28. To connect the rectifier circuit 29 to the test circuit 34 by winding the second secondary winding 28b around the transformer 28.
Power supply. Since the second secondary winding 28b is required, there is a problem that the transformer 28 becomes large and the manufacturing cost increases.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the conventional test circuit for an electric leakage detector, an object of the present invention is to reduce the manufacturing cost and reduce the size of the electric leakage detector test circuit. The structure is 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, and a sensitivity setting unit that sets the sensitivity of the input voltage. A low-pass filter that removes high-frequency components, an AC coupling that removes DC components, an amplifier that amplifies the input voltage, and a comparison between the amplified voltage and a preset set voltage, and when the amplified voltage exceeds the set voltage. A leakage detection circuit including a comparison unit that outputs an alarm signal; a transformer for stepping down the 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. Power supply circuit consisting of In order to confirm the operation of the zero-phase current transformer and the leakage detection circuit, a leakage detector consisting of a resistor and a test circuit that generates a pseudo-leakage current is connected to the output side of the zero-phase current transformer. That is, a pseudo leakage current source is formed by connecting a capacitor between the provided switch and the secondary side of the transformer with a single connection line.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A resistor and a switch are connected in parallel between one output side of a zero-phase current transformer and an input protection section, and a secondary side of a transformer in which a test side of the switch and a power supply circuit are connected. Is connected with a resistor and a capacitor interposed in series.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a test circuit for an earth leakage detector according to the present invention will be described with reference to the accompanying 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. If the input voltage from the zero-phase current transformer 4 is excessive, the leakage current is input. The leakage detecting circuit 3 is protected by the protection unit 5, and then the input voltage input from the zero-phase current transformer 4 is converted into a voltage corresponding to the sensitivity set in advance by the sensitivity setting unit 6.
To remove the high-frequency component causing a malfunction, remove the DC component by the AC coupling 8 composed of the capacitor C1 and the resistor R1, amplify the input voltage by the amplifier 9, and compare the amplified voltage with a preset set voltage. Compared by part 10,
When the amplified voltage exceeds the set voltage, it outputs an alarm signal and notifies the outside of the earth leakage by sound or light.

The power supply of the electric leakage detection circuit 3 is supplied by a power supply circuit 11. The power supply circuit 11 connects the AC power supply to the transformer 1.
2 and rectified by a rectifier circuit 13 composed of four diodes D1, D2, D3 and D4 connected to the secondary side of the transformer 12, and by a smoothing capacitor C2 connected between output terminals of the rectifier circuit 13. It is smoothed and converted to DC.

A test circuit 14 for confirming the operation of the leakage detection circuit 3 of the leakage detector 1 and for confirming the presence or absence of a disconnection failure of the zero-phase current transformer 4 includes resistors R2 and R3 and a switch 1 of a switching type.
Consists of five.

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 usually connected to the monitoring side. One of the test side of the switch 15 and one of the secondary sides of the transformer 12 is connected with a resistor R3 and a capacitor C3 interposed in series. When the test of the leakage detection circuit 3 is performed, the test is performed by switching the switch 15 to the test side.

By interposing the capacitor C3, the influence of the DC potential can be eliminated and the test can be performed normally.

In the present embodiment, the rectifier circuit 13 is full-wave rectified by a diode bridge. However, there is no problem with half-wave rectification and the rectifier circuit is not limited.

[0013]

As described above, the test circuit of the leakage detector according to the present invention comprises 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 that sets the sensitivity of the input voltage, a low-pass filter that removes high-frequency components, an AC coupling that removes DC components, an amplifier that amplifies the input voltage, and a comparison between the amplified voltage and a preset voltage A leakage detection circuit comprising a comparator for outputting an alarm signal when the amplified voltage exceeds a set voltage, a transformer for stepping down an AC power supply, a rectifier circuit connected to a secondary side of the transformer, and a rectifier. A power supply circuit consisting of a smoothing capacitor connected between the output terminals of the circuit, and a test circuit consisting of a resistor and a switch for generating a pseudo leakage current to confirm the operation of the zero-phase current transformer and the leakage detection circuit. Configured ground fault At the output unit, a capacitor is interposed between the switch provided on the output side of the zero-phase current transformer and the secondary side of the transformer and connected with a single connection line to form a pseudo leakage current source for the test circuit. By doing this, it is not necessary to increase the number of secondary windings of the transformer, but only by adding a capacitor, so that the manufacturing cost is reduced, and the leakage detector itself is reduced in size and weight with the downsizing of the transformer. This has an excellent effect that the number of connection lines between the leakage detection circuit and the secondary side of the transformer can be reduced and the circuit pattern can be simplified.

[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 Rectifier circuit 14 Test circuit 15 Switch C1 Capacitor C2 Smoothing capacitor C3 Capacitor D1 Diode D2 Diode D3 Diode D4 Diode R1 Resistance R2 Resistance R3 Resistance

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01H 83/02 H01H 83/02 F

Claims (1)

[Claims] 1. A zero-phase current transformer for detecting a leakage current of a warning circuit, an input protection unit for protecting a circuit from an excessive input voltage, a sensitivity setting unit for setting the sensitivity of the input voltage, and a high frequency component. A low-pass filter for removing, an AC coupling for removing a DC component, an amplifier for amplifying the input voltage, comparing the amplified voltage with a preset set voltage, and warning when the amplified voltage exceeds the set voltage. A leakage detecting circuit comprising a comparing unit for outputting a signal, a transformer for stepping down the AC power, a rectifying circuit connected to a secondary side of the transformer, and a smoothing circuit connected between output terminals of the rectifying circuit. A power supply circuit composed of a capacitor, and a leakage detector composed of a test circuit composed of a resistor and a switch for generating a pseudo leakage current for confirming operation of the zero-phase current transformer and the leakage detection circuit, The zero-phase A capacitor is interposed between the switch provided on the output side of the current transformer and the secondary side of the transformer and connected by a single connection line to constitute a pseudo leakage current source of the test circuit. Test circuit for leakage detector.