JPS6211175A - Leak detector - Google Patents

Abstract

PURPOSE:To obtain a leak detector having high-safety and fail-safe, by providing the winding, which is connected between an apparatus case and a hot-side power source wire through a high resistor, to the current transformer inserted between a power source and the apparatus. CONSTITUTION:A switch S is closed to judge whether the case 101 of the apparatus 1 is earthed. When said case 101 is earthed, a current flows to the winding 24 connected between the case 101 and a hot side power source wire H through a high resistor R and the magnetomotive force of a current transformer 2 comes to non-equilibrium and non-equilibrium output is generated in output winding 23. When the case 101 to the apparatus 1 comes to a non-earth state by an earth disconnection accident, no current flows to the high resistor R and the winding 24 connected between the case 101 and the hot-side power source wire H. Therefore, the current transformer 2 comes to such an equilibrium state that the magnetomotive force of hot-side winding 21 and that of cold side winding 22 are mutually negated and no output is generated in the output winding.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a current leakage detector for detecting current leakage in various electrical and electronic devices, and is a device case and a current transformer inserted between a power source and the device. By providing a winding connected to the hot side power supply line through a high resistance, it is possible to detect the presence or absence of grounding in the device case and to detect electrical leakage.

2. Description of the Related Art As a conventional earth leakage detector, for example, the one shown in FIG. 4 is known. In FIG. 4, l is the device, 101 is the case of the device l, 102 is the internal load, and the case 101
is grounded. 2 is a current transformer, and 3 is a detection circuit.

The current transformer 2 is inserted in series between the power supply and the device 1, and is connected to the hot side type r of the two power supply lines H and C.
Winding 21 including A line H in series Winding 22 including cold side power supply line C in series and output crane 23 Le now λ Output optical axis 9
3 Le Kusunoki loses Lψ connection.

In normal operating conditions with no leakage, the magnetomotive force due to the current flowing through the hot side winding 21 and the magnetomotive force due to the current flowing through the cold side A wire 22 are balanced in opposite directions, so they cancel each other out. Therefore, no output is generated in the output winding 23. This is assumed to be no leakage.

However, if an electrical leakage accident occurs in which the hot side power supply line H conducts to the case 101 (A), the current that has flowed through the hot side winding 21 flows through the case 101 to the ground, and then flows to the cold side winding 22. The current flowing is significantly reduced. Therefore, the magnetomotive force between the hot side winding 21 and the cold side winding 22 becomes unbalanced, and an output is generated in the output winding 23.

By detecting the output with the detection circuit 3, leakage can be detected.

Problems to be Solved by the Invention However, in the conventional earth leakage detector shown in FIG. 4, if the case 101 is not grounded, even if there is an earth leakage, the problem will be the same as in the normal case when there is no earth leakage. The current flowing through the hot side power supply line H and the current flowing through the cold side power supply line C become equal in opposite directions, and the magnetomotive forces of the hot side winding 21 and the cold side winding 22 cancel each other out, and the output winding 23 It produces no output, so it cannot be detected whether or not it is grounded, and if it is not grounded, it is impossible to detect electrical leakage.

If a current leak occurs while the device is grounded, there is no serious danger, but if a current leak occurs without the device being grounded, it is extremely dangerous. In other words, the conventional earth leakage detector cannot detect an earth leakage in the most dangerous state where the case is floating from the ground, and in this state, there is a serious problem of risk of electric shock.

Means for Solving the Problems In order to solve the above-mentioned conventional problems, the present invention provides a winding including a hot-side power wire in series and a cold-side power wire in series with the power wire connecting the power source and the device. In the earth leakage detector in which a current transformer having a winding included in the output winding and an output winding is inserted, and a detection circuit is connected to the output winding, the current transformer is provided with another winding different from each of the windings, and this separate winding is provided. The winding wire is connected between the case of the device and the hot side power supply line through a high resistance.

Effect In the earth leakage detector with the above configuration, when the case of the device is grounded, current flows through the winding connected between the case and the hot side power supply line through a high resistance, and the magnetomotive force of the current transformer is generated. becomes unbalanced, producing an unbalanced output in the output winding.

However, when the case of the device becomes ungrounded, current no longer flows through the winding connected between the case and the hot side power wire, and the current transformer combines the magnetomotive force of the hot side winding with the cold side winding. There is an equilibrium state in which the magnetomotive forces of the Since the currents flowing in the side power line and the cold side power line become significantly unbalanced, the output of the output winding becomes high level.

As mentioned above, the output level of the output winding is approximately zero when it is not grounded, and when it is unbalanced due to leakage, it becomes significantly higher than the normal level. By detecting this with the detection circuit, it is possible to and can detect electrical leakage.

Embodiment FIG. 1 is an electrical circuit diagram of an earth leakage detector according to the present invention.
In the figure, the same reference numerals as in FIG. 4 indicate the same components. In this embodiment, a winding 21 including a hot side power supply line H in series, a winding 22 including a cold side type r Insert the current transformer 2 having It is connected to the line H via a high resistance R. The resistance value of the high resistance R is selected so that the current flowing from the hot side power supply line H through the winding 24 to the case 101 has a minute value that does not affect the human body.

3 is a detection circuit, and S is a switch. The detection circuit 3 includes a rectifier circuit 31 and a level tester 32.

In the earth leakage detector of the above embodiment, the case 10 of the device 1
1 is grounded or not by closing the switch S. If it is grounded, a high resistance R is connected to the winding 24 connected between the case 101 and the hot side power supply line H.
A current flows through the current transformer 2, and the magnetomotive force of the current transformer 2 becomes unbalanced, causing an unbalanced output in the output winding 23.

However, if the case 101 of the device I becomes ungrounded due to a ground disconnection accident or the like, current no longer flows through the high resistance R connected between the case 101 and the hot side power supply line H and the winding 24. Therefore, the current transformer 2 is in an equilibrium state in which the magnetomotive force of the hot side winding 21 and the magnetomotive force of the cold side winding 22 cancel each other out, so that the output winding 23
produces no output.

Next, the hot side power supply line H leaks to the case 101 side (A).
In this case, the current flowing through the high resistance H decreases and the current flowing through the hot side power supply line H and the cold side power supply line C become significantly unbalanced, so that the output of the output winding 23 becomes high level.

Therefore, the non-earthed state and the earth leakage state can be detected by verifying the zero level at the time of non-earth and the high level at the time of electric leakage in the level tester 32 of the detection circuit 3.

- A window comparator is suitable as the level tester 32 as described above. Among these, a fail-safe window comparator (for example, Utility Model Application No. 791072/1987, previously proposed by the present applicant) is particularly suitable. FIG. 2 shows a specific example of the transistor TR1.
``The AND operation oscillator is constituted by TR3, and oscillation is caused by the DC signal Vl given from the rectifier circuit 31.The oscillation output is rectified by the rectifier circuit and output.

The window comparator shown in FIG. 2 is fail-safe because if one circuit fails, the output becomes zero, and the output is the same as when it is not grounded.

The rectifier circuit 31 and the rectifier circuit can also be made fail-safe by forming, for example, a circuit as shown in FIG. In FIG. 3, DI and D2 are diodes, and CI and C2 are capacitors.

Effects of the Invention As described above, according to the present invention, a current transformer inserted between a power supply and a device is connected between the device case and the hot side power supply line via a high resistance. It is possible to provide a highly safe and fail-safe earth leakage detector that includes a winding and can detect the presence or absence of grounding in the device case and earth leakage.

[Brief explanation of drawings]

Figure 1 is an electric circuit diagram of the earth leakage detector according to the present invention, Figure 2 is an electric circuit diagram of a level verification circuit, Figure 3 is an electric circuit diagram of a rectifier circuit, and Figure 4 is an electric circuit diagram of a conventional earth leakage detector. It is an electrical circuit diagram. l...Device 101...Case 102...
・Load 2...Current transformer 21...φHot side winding 22...Cold side winding 23...φOutput winding 24...φ Other winding 3...Detection circuit Figure 1 Figure 2 Figure 3

Claims (3)

[Claims] (1) A current transformer having a winding including a hot side power line in series, a winding including a cold side power line in series, and an output winding is inserted into the power line connecting the power source and the device, and the output winding In the earth leakage detector in which a detection circuit is connected to the current transformer, another winding different from each of the windings is provided in the current transformer, and this other winding is connected to the case of the device and the hot side power supply line through a high resistance. An earth leakage detector characterized in that it is connected between. (2) The earth leakage detector according to claim 1, wherein the detection circuit is a window comparator. (3) The earth leakage detector according to claim 2, wherein the window comparator is configured in a fail-safe manner.