JPH11299082A - Earth leakage breaking device provided with overvoltage protecting function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an earth leakage breaking device provided with a function of, preventing damages to the electrical equipment and apparatuses due to the overvoltage when an overvoltage is applied to electrical machinery and apparatus. SOLUTION: An earth leakage breaker which monitors the current difference between electrical paths 2, 2' connecting a power supply 1 and a load Z and detects an electric leakage is provided with an overvoltage detecting means B, which monitors the voltage of the power supply 1 and detects overvoltage state. If the overvoltage detecting means B determines that there is an overvoltage, a switching element 7 installed in a leakage detector is turned onto release a relay contact RL. In addition a surge absorbing element 12 is installed between the electrical paths 2, 2'. When an overvoltage exceeding a certain level is applied, overvoltage is absorbed and alleviated by means of the surge absorbing element 12, and a delay in overvoltage detection at the overvoltage detecting means B is compensated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earth leakage breaker, and more particularly, to an earth leakage breaker obtained by adding an overvoltage protection function to an earth leakage breaker built in an electric device or the like.

[0002]

2. Description of the Related Art Conventionally, as a countermeasure against electric leakage causing electric shock or fire, an electric leakage breaker is provided in an indoor distribution board. For example, electric equipment used around water such as a gas water heater is used. In some cases, the device itself has a built-in earth leakage breaker separately from the earth leakage breaker in the distribution board.

FIG. 2 shows an example of an earth leakage breaker built in such an electric device itself. The earth leakage breaker A shown in FIG.
A device interposed between the input terminal 1 and the load Z,
Leakage is detected by detecting a current difference between a reciprocating electric circuit 2, 2 'connecting the AC input terminal (hereinafter simply referred to as a power supply) and the load Z, which is caused by a ground fault current generated on the load Z side. Then, when the leakage is detected, the power supply to the load Z is cut off.

More specifically, the earth leakage breaker A is a zero phase current transformer (ZCT) for detecting a current difference between the electric circuits 2 and 2 '.
4, a leakage detection circuit 5 for detecting a voltage generated between coil terminals of the zero-phase current transformer 4, a relay circuit 6 for driving a relay contact RL, and an output from the leakage detection circuit 5 based on the output from the leakage detection circuit 5. A switching element (thyristor) 7 for turning on the relay circuit 6 and a rectifying and smoothing constant voltage circuit 8 for supplying a drive voltage to the electric leakage detection circuit 5 and the relay circuit 6 are mainly configured. In the example shown in FIG. 2, the leakage detection circuit 5 is formed as an IC,
Is a diode for preventing a current from flowing into the output terminal of the leakage detection circuit 5. The relay contact RL is a normally short-circuited relay, and is opened when the switching element is turned on and the relay circuit 6 is energized.

[0005] When a ground fault current flows due to leakage on the load side, a current difference is generated between the currents flowing through the electric paths 2 and 2 ′, thereby causing a difference between the terminals of the coil of the zero-phase current transformer 4. Voltage is generated. The leakage detecting circuit 5 detects a voltage generated in the coil and supplies a current to the gate of the switching element 7 formed of a thyristor. As a result, the conduction between the anode and the cathode of the switching element 7 is turned on.
Then, the current from the rectifying / smoothing constant voltage circuit 8 flows through the relay circuit 6, the relay contact RL is opened, and the power supply from the power supply 1 to the load Z is cut off.

The reason why such an earth leakage breaker is built in the electric equipment itself is as follows. In other words, in a water heater or the like used around water, it is preferable to increase the current difference detection sensitivity (leakage detection sensitivity) between the electric circuits 2 and 2 'as compared with a normal electric device for safety measures. This is because, in the configuration in which the leakage breaker in which the branch circuits are collectively provided on the distribution board is provided, the detection sensitivity cannot be sufficiently increased due to the necessity of preventing malfunction of the leakage breaker.

[0007]

As described above, it is preferable in terms of safety measures to incorporate an earth leakage breaker for each device in accordance with the characteristics of the device, such as the place where the electric device is used. It was used exclusively for leak detection and had no other functions.

[0008] In other words, the design of such an earth leakage breaker is based on the premise that commercial power supplied to electric equipment is always stable. Therefore, for example, the commercial power supply AC1
No measures have been taken in the case where 00V rises to AC110V or more. However, such a change in voltage or the like has a possibility of damaging a power supply board, a main board, a load device, or the like of an electric device, and there is a need to consider a countermeasure for each device with respect to such a situation.

Particularly, as in today, even in ordinary households, a single-phase three-wire system (100 V / 200 V) is used so that a large amount of electric equipment such as an air conditioner or an electric water heater (power supply voltage of 200 V AC) can be used. In the current situation where electric power is supplied in (1), even if the electric equipment such as a gas water heater is driven by AC100V, if the connection on the neutral (earth wire) side of the above three wires is disconnected, for example, Since an abnormal voltage (overvoltage) is applied to the power supply, it can be said that there is sufficient need to consider a countermeasure against such a situation.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a function capable of preventing damage to equipment caused by overvoltage when the electrical equipment is overvoltaged. The main object is to provide an additional earth leakage cutoff device.

[0011]

According to a first aspect of the present invention, there is provided an earth leakage breaker with an overvoltage protection function interposed between a power supply and a load, and provided between an electric circuit connecting the power supply and the load. An earth leakage interrupting device that detects an earth leakage from a current difference and shuts off power supply to the load, monitors an electric current difference between the electric circuits, and outputs an output when the electric current difference exceeds a predetermined value. Detecting means and monitoring the voltage of the power supply,
Overvoltage detecting means for generating an output when the power supply voltage exceeds a predetermined detection voltage, and load releasing means for releasing the load from a power supply based on an output from the leakage detecting means or the overvoltage detecting means. It is characterized by the following.

Preferably, the load releasing means includes a relay contact provided on an electric circuit, a relay circuit for driving the relay contact, and a power supply to the relay circuit connected in series with the relay circuit. And a switching element for controlling the power supply of the switching element by the output of the leakage detecting means or the overvoltage detecting means, and the rectifying element for rectifying the power supply voltage, And a comparator that divides the power supply voltage rectified by the rectifying element and compares it with a reference voltage to determine whether or not the voltage is an overvoltage.

That is, the earth leakage breaker according to claim 1 of the present invention is obtained by adding an overvoltage detection means for monitoring an increase in power supply voltage to a conventionally provided earth leakage breaker, The configuration is such that the load side is opened from the power supply side not only at the time of leakage detection but also at the time of overvoltage detection. In other words, the first aspect of the present invention is to integrally form the leakage detecting means and the overvoltage detecting means as one device, and to use the load releasing means in common. Therefore, in the earth leakage breaker with the overvoltage protection function of the present invention, the number of parts can be reduced as compared with the case where both the earth leakage breaker and the overvoltage breaker are separately provided, and the device itself can be made compact. Can be.

Further, the earth leakage breaker with overvoltage protection function according to claim 4 is characterized in that a surge voltage absorbing means is interposed on a load side from a relay contact between the electric lines, and preferably, the surge voltage absorbing means is provided. The operating voltage of the voltage absorbing means is set higher than the detection voltage of the overvoltage detecting means.

That is, the present invention according to claim 4 provides:
When the power supply voltage is detected by the overvoltage detection means, if a capacitor is included in a circuit constituting the overvoltage detection means, a time delay occurs from the application of the overvoltage until the load opening means operates. According to the fourth aspect of the present invention, the surge voltage absorbing means is particularly configured to absorb the overvoltage therebetween. The reason why the operating voltage of the surge voltage absorbing means is set higher than the overvoltage detection voltage is to prevent the surge voltage absorbing means from operating due to a slight voltage change that is not judged to be an overvoltage by the overvoltage detecting means. .

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit configuration of a leakage breaker with an overvoltage protection function according to the present invention (hereinafter referred to as a leakage breaker). The earth leakage breaker shown in FIG. 1 is of a type to be added to an electric device such as a water heater (specifically, for example, integrally formed with a plug at the end of a power cord of the device, or a box inside the device main body). AC input terminal of a device connected to a commercial power supply (e.g., a device that incorporates a device configured in a shape, and a device that is configured as a discrete circuit on a controller board in the device body). A power supply) 1 and a load Z, and detects leakage and overvoltage. When leakage or overvoltage is detected, the electric circuits 2 and 2 'connecting the power supply 1 and the load Z are connected. Open to shut off the power supply from the power supply 1 to the load Z.

The leakage interrupter includes a leakage detecting means for monitoring a current difference between the electric circuits 2 and 2 'and generating an output when the current difference between the electric circuits 2 and 2' exceeds a predetermined value. An overvoltage detecting means for monitoring the voltages of the electric circuits 2 and 2 'and generating an output when the voltage exceeds a predetermined voltage; and connecting the load Z to a power supply 1 based on the output from the electric leakage detecting means or the overvoltage detecting means. And a load release means for releasing the load from the main part.

More specifically, this earth leakage breaker includes a zero-phase current transformer (ZCT) 4 for detecting a current difference between the electric circuits 2 and 2 ′, A leakage detecting circuit 5 for detecting a voltage generated in the coil, and a relay contact RL provided on the electric circuits 2 and 2 'as the load releasing means, and a relay circuit 6 for driving the relay contact RL. The operation of the relay circuit 6 is controlled by a switching element (thyristor) 7 that is turned on based on the output from the leakage detection circuit 5;
In addition, it has a configuration similar to that of the leakage breaker shown in the above-described conventional example, for example, a drive power supply for the leakage detection circuit 5 and the relay circuit 6 is supplied via a rectified smoothing constant voltage circuit (such as a full-wave rectification circuit) 8. . That is, also in the earth leakage breaker of the present invention, the earth leakage detection operation and the load opening operation at that time are the same as those of the conventional earth leakage detector.

According to the present invention, these conventional arrangements are provided with overvoltage detecting means for detecting an increase in the voltage of the electric circuits 2 and 2 ', that is, the power supply 1. Specifically, this overvoltage detecting means is connected in parallel to the electric circuits 2 and 2 'as shown by a two-dot chain line B in FIG. 1, and a rectifying diode (rectifying element) 9 for half-wave rectifying the power supply voltage. And a comparator (comparator) 10 for overvoltage detection as a main part. The resistors R _1, R _2, R _{3, and} R ₄ in the drawing all indicate resistors for dividing the input voltage to the comparator 10, and C indicates a capacitor. Further, the diode 11 provided on the output side of the comparator is a diode for cutting off the current from the leakage detection circuit 5 side. In the overvoltage detecting means, the rectifying diode 9 is used.
The power supply voltage thus rectified is divided by the resistors R _{1 and} R ₂ and input to the comparator 10.

The operation of the overvoltage detecting means will be described. For example, when the power supply voltage supplied at 100 V AC rises to 110 V AC or more due to voltage fluctuations, the voltage rise is detected by the comparator 10. You. Specifically, since the power supply voltage is divided by the resistors R _{1 and} R ₂ , the comparator 10 divides the power supply voltage into a reference voltage obtained by dividing the power supply voltage that has been made constant by the rectifying and smoothing constant voltage circuit 8. , The voltage dividing resistors R _{1 and} R through the rectifying diode 9.
_The input voltage divided by ₂ is compared, and if it is determined that the input voltage exceeds the reference voltage, it is determined that an overvoltage has occurred. When it is determined that an overvoltage has occurred, the output of the comparator 10 becomes high, and the gate of the thyristor constituting the switching element 7 is turned on. Is turned on, and the relay circuit 6 is driven. As a result, even when an overvoltage is detected, the relay contact RL is opened and the load Z side is opened from the power supply 1 as in the case of the above-described leakage detection.

As described above, according to the present invention, the relay contact RL is opened not only at the time of leakage detection but also when an overvoltage is applied to the load Z, so that the overvoltage is applied to the load Z. Is prevented. In this case, the opening on the load Z side is performed by the relay contact RL, the relay circuit 6 and the switching element 7 used in the earth leakage breaker.
, The circuit configuration can be simplified and the device can be downsized. For this reason, it is preferable to take up a small space when incorporating it into an electric device or the like.

In the present invention, application of an overvoltage to the load Z is prevented in this way, but in the present invention, it is desirable that a surge voltage absorbing means 12 is further interposed between the electric circuits 2 and 2 '. .

That is, in the case of the above-described overvoltage detecting means, since the capacitor C is provided on the input side of the comparator 10, a time delay occurs in the overvoltage detection due to the capacitor C. As a result, a slight time lag occurs from the occurrence of the overvoltage to the release of the load Z. However, when the above-described overvoltage involves a large voltage fluctuation such as a surge voltage, the load Z side may be damaged due to such a time lag. Therefore, in the present invention, as shown in FIG. 1, it is preferable that a surge voltage absorbing means (surge absorbing element) 12 is connected in parallel between the electric circuits 2 and 2 'in order to absorb such a surge voltage.

More specifically, the surge voltage absorbing means 12
For example, when a voltage equal to or higher than a predetermined operating voltage is applied between terminals, a surge absorbing element (for example, a ZNR) that absorbs a voltage in a portion exceeding the operating voltage is preferably used.

The surge absorbing element 12 whose operating voltage is higher than the voltage (detected voltage) determined as overvoltage by the overvoltage detecting means is used. In other words, the problem of the delay of the overvoltage detection by the capacitor C as described above depends on the set value of the detection voltage, but normally an abnormal voltage such as a surge voltage exceeding the detection voltage is applied. Is the case. Therefore, when the surge absorbing element 12 is selected, it is preferable to use an element having an operating voltage higher than the detection voltage to prevent the load Z from being damaged by such an abnormal voltage.

Thus, such a surge absorbing element 12
In the case where a suddenly high abnormal voltage is applied by interposing between the electric circuits 2 and 2 ′, the abnormal voltage is first absorbed and reduced by the surge absorbing element 12. Then, in this state, the overvoltage detecting means operates,
Despite the delay of the overvoltage detection, it is possible to open the relay contact RL without damaging the load Z.

The above-described embodiment merely shows a preferred embodiment of the present invention, and the present invention is not limited to this, and various design changes can be made within the scope.

For example, in the above embodiment, the reset switch for resetting the switching element 7 is not mentioned, but in the above embodiment in which the switching element 7 is constituted by a thyristor, a reset switch for short-circuiting between the anode and the cathode is provided. By providing this, it is possible to turn off the thyristor once turned on, that is, to return the relay contact RL to the short-circuit state.

In the above embodiment, the relay is used as the load releasing means. However, it is of course possible to release the load Z by another method instead of the relay. Similarly, in the above embodiment, the leakage detection circuit 5
Although the configuration using an IC has been described above, it is also possible to realize the configuration using a circuit configuration other than the IC.

Further, in the above embodiment, the input power
Although the description has been made on the assumption that the device is C100V, the present invention is also applicable to a case where the input power supply is other than the above. That is,
In the present invention, by changing the reference voltage of the comparator 10 and the operating voltage of the surge absorbing element 12, for example, a device (for example, an air conditioner or an electric water heater) having an input voltage of 200 V AC or in a foreign country or the like is used. It is also possible to correspond to a device driven by an input voltage different from Japan.

[0032]

As described above in detail, according to the earth leakage interrupting device of the present invention, the earth leakage interrupting device includes the earth leakage detecting means and the overvoltage detecting means, and operates based on the output of either of them. Therefore, the load can be released from the power supply side not only at the time of electric leakage but also at the time of overvoltage, and damage to the load due to overvoltage such as abnormal voltage can be prevented.

Also, in the present invention, since the load releasing means for releasing the load side due to overvoltage is common between the detection of the leakage and the detection of the overvoltage, the case where both the leakage breaker and the overvoltage breaker are separately provided. The number of parts can be reduced, the size can be reduced, and the manufacturing cost can be reduced.

Further, by interposing the surge voltage absorbing means between the electric lines, the problem of the time delay of the overvoltage detection by the voltage detecting means can be solved, and the damage to the load due to the overvoltage can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating the configuration of a ground fault interrupting device according to the present invention.

FIG. 2 is a schematic configuration diagram illustrating a configuration of a conventional earth leakage breaker.

[Explanation of symbols]

Reference Signs List A Leakage breaker B Overvoltage detection means RL Relay contact 1 Power supply (AC input terminal of electric equipment) 2, 2 'circuit 4 Zero-phase current transformer 5 Leakage detection circuit 6 Relay circuit 7 Switching element 8 Rectification smoothing constant voltage circuit 9 Rectification Diode (rectifier) 10 Comparator (comparator) 12 Surge voltage absorbing means (surge absorbing element)

Claims (5)

[Claims] 1. An earth leakage cut-off device interposed between a power supply and a load, which detects an earth leakage from a current difference between electric circuits connecting the electric power supply and a load and cuts off power supply to the load. A leakage detection means for monitoring a current difference and generating an output when the current difference exceeds a predetermined value; and monitoring a voltage of the power supply and outputting an output when the power supply voltage exceeds a predetermined detection voltage. An overvoltage detecting means for generating the voltage; and a load releasing means for releasing the load from a power supply based on an output from the leakage detecting means or the overvoltage detecting means. 2. The relay according to claim 1, wherein said load releasing means includes a relay contact provided on an electric circuit, a relay circuit for driving said relay contact, and a switching circuit connected in series with said relay circuit for controlling energization of said relay circuit. The leakage interrupting device with an overvoltage protection function according to claim 1, further comprising: an element configured to control energization of the switching element based on an output of the leakage detecting unit or the overvoltage detecting unit. 3. A rectifying element for rectifying a power supply voltage, a comparator rectifying the power supply voltage rectified by the rectifying element, and a comparator for determining whether or not the voltage is an overvoltage by comparing the divided voltage with a reference voltage. The earth leakage cut-off device with an overvoltage protection function according to claim 1, characterized in that: 4. The leakage breaker with overvoltage protection function according to claim 2, wherein a surge voltage absorbing means is interposed on a load side of the relay contact between the electric circuits. 5. The operating voltage of said surge voltage absorbing means is:
The earth leakage breaker with an overvoltage protection function according to claim 4, wherein the voltage is set higher than a voltage detected by the overvoltage detection means.