JP2003059388A - Electric leakage protection plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent burnout accident of equipment when a voltage higher than predetermined is supplied to load equipment through an electric leakage protection plug. SOLUTION: Elements such as a Zener diode that conducts when a voltage higher than a predetermined is applied are connected in parallel with a test switch 7a of an operation confirmation test circuit 7 of the leakage protection plug as a pseudo earth leakage circuit 8. For example, when a leakage protection plug for 100 v appliance is connected to a 200 v plug outlet, the pseudo earth leakage circuit 8 conducts applied with high voltage and the pseudo earth leakage current runs to the test circuit 16 in the same manner as a test switch 7a is pressed. Hence, the pseudo earth leakage current is detected by a zero- phase inverter 3 and the leakage protection plug trips to cut the electrical supply to the load equipment and prevents it from burning-out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earth leakage protection plug which is connected to a power source such as a hot water toilet seat or an electric water heater, and which trips when an electric leakage occurs to prevent an electric shock accident or a device burnout accident.

[0002]

2. Description of the Related Art FIG. 5 shows the outer shape of this type of leakage protection plug. FIG. 5 (A) is a side view and FIG. 5 (B) is a front view. In FIG. 5, at one end of the molded case 10,
A pair of left and right plugs 11 inserted into a power outlet (not shown) protrude, and a cord 12 connected to a load device extends from the other end. On the front of the molded case 10,
Leakage indicator LED13 that indicates the occurrence of trip, reset button 1 that resets the tripped leakage protection plug
4. A test button 15 for a trip test is arranged.

FIG. 6 is a circuit diagram showing the internal structure of the leakage protection plug. As shown in FIG. 6, the leakage protection plug is
A main contact 2 inserted in the main circuit 1 from the power supply side (IN) to the load side (OUT), a zero-phase current transformer (ZCT) 3 penetrating the main circuit 1, and a leakage detection circuit 4 for amplifying the output of ZCT3. , A trip coil 6 connected between the phases of the main circuit 1 via a thyristor 5, a test circuit 7 for a trip test, and the like. The test circuit 7 comprises a test switch 7a and a resistor 7b, which penetrates the ZCT 3 and is connected between the phases of the main circuit 1.

In such an earth leakage protection plug, when an electric leakage occurs in the load circuit, an unbalanced current flows in the main circuit 1 and an output is generated in the ZCT 3 which detects this. Therefore, when the output of ZCT 3 exceeds a certain level, leakage detection circuit 4 determines that there is leakage and immediately turns on thyristor 5. As a result, the trip coil 6 is excited, the main contact 2 latched in the closed state is unlatched and opened, and the power supply is cut off (trip). To reset the tripped earth leakage protection plug, press the reset button 14 (Fig. 5),
The main contact 2 is closed and latched again. On the other hand, when the test switch 7a is pressed via the test button 15 (FIG. 5), the pseudo leakage current flows through the ZCT3. This pseudo-leakage current causes an output in ZCT3, and a trip is performed as in the case of occurrence of a leakage. This test confirms the trip operation of the earth leakage protection plug.

[0005]

By the way, most of the household electric appliances are used at 100v.
Use at 00v was rare. However, in recent years, some electric appliances for home use, such as an air conditioner, have been increasingly used at 200 V due to improved efficiency. Along with that, 100v and 200v have come to be mixed in household wiring, but at the same time, an accident such as 200v being wired to a 100v outlet due to construction mistakes and 100v equipment connected to it being burned is increasing. is there.

The present invention addresses such a situation, and an object thereof is to prevent accidents such as burnout of a device when a 100v device is connected to a 200v outlet.

[0007]

According to the present invention, when a load device is connected to a power source through an earth leakage protection plug, and if the power supply voltage is in an overvoltage state higher than a predetermined voltage, the earth leakage protection plug is tripped immediately. In order to solve the above-mentioned problems, the load devices are prevented from reaching each other. That is, the present invention detects the unbalanced current of the main circuit with a zero-phase current transformer,
It has a test circuit that opens a main contact inserted in the main circuit, penetrates the zero-phase current transformer, and is connected between phases of the main circuit via a test switch, and the test switch is pressed. And a pseudo leakage current is passed through the test circuit, and when the pseudo leakage current is detected by the zero-phase current transformer, the leakage protection plug that opens the main contact conducts when an overvoltage higher than the predetermined voltage of the main circuit is applied. A pseudo leakage circuit is provided, and the pseudo leakage circuit is connected in parallel to the test switch (claim 1). According to this claim 1, when an overvoltage is applied to the leakage protection plug, the pseudo leakage circuit conducts and a pseudo leakage current similar to the case where the test switch is pressed flows into the test circuit, and the leakage protection plug is released. It trips instantly and the power supply to the load equipment is cut off.

A plurality of Zener diodes reversely connected to each other (Claim 2), Zener diodes and diodes (Claim 2) to be reversely connected to each other, and a varistor (Claim 3) are used in the pseudo leakage circuit. be able to.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram of an earth leakage protection plug showing an embodiment of the present invention. 1 is different from the conventional example of FIG. 6 in that the predetermined voltage of the main circuit 1, for example 100, is provided in parallel with the test switch 7a of the test circuit 7.
The point is that the pseudo-leakage circuit 8 is provided that conducts when an overvoltage higher than v, for example, 200 v is applied. Since other configurations are the same as those of the conventional example, description thereof will be omitted. Now, when the earth leakage protection plug of FIG. 1 is inserted into a power outlet, the power supply voltage is directly applied to the pseudo earth leakage circuit 8 connected in parallel with the test switch 7a of the test circuit 7 connected between the phases of the main circuit 1. To be done. In that case, for example, in the leakage protection plug for 100v, the pseudo leakage circuit 8
For example, if it is set to conduct at 140 V or more, there is no problem as long as the power outlet has a predetermined voltage (100 V). 7a is short-circuited,
A pseudo leakage current flows in the test circuit 7, and the leakage protection plug trips instantly. As a result, the load equipment is cut off from overvoltage, and accidents such as burnout are avoided.

[0010]

FIG. 2 is a circuit diagram of essential parts showing a first embodiment in which a Zener diode is used as the pseudo leakage circuit 8. In FIG. 2, the pseudo earth leakage circuit 8 is configured by connecting a plurality (two) of Zener diodes 8A in opposite directions. When an AC overvoltage exceeding the Zener voltage of the Zener diode 8A is applied to the pseudo earth leakage circuit 8, the pseudo earth leakage circuit 8 becomes conductive and the earth leakage protection plug trips at any AC half wave. The Zener diode 8
The number of A is not limited to two, but an appropriate number of Zener diodes 8
It is possible to adjust the conduction voltage by connecting two sets of A connected in the same direction and connecting them in the opposite direction.

FIG. 3 is a main part circuit diagram showing a second embodiment in which a Zener diode and a diode are used as the pseudo leakage circuit 8. In FIG. 3, the pseudo-leakage circuit 8 is formed by connecting the Zener diode 8A and the diode 8B in opposite directions. When an AC overvoltage exceeding the Zener voltage of the Zener diode 8A is applied to the pseudo earth leakage circuit 8, the pseudo earth leakage circuit 8 becomes conductive in the forward AC half-wave of the diode 8B, and the earth leakage protection plug trips. In the second embodiment, since the trip occurs after waiting for the forward half AC wave of the diode 8B, the operation time is slightly delayed. However, since the diode is generally cheaper than the Zener diode, the manufacturing cost is reduced accordingly. Also, the operation time delay is at most about 20 to 30 ms, and practically no problems occur. Note that the number of Zener diodes 8A and diodes 8B is not limited to one, and an appropriate number can be connected in the same direction.

FIG. 4 is a main part circuit diagram showing a third embodiment in which a varistor is used as the pseudo leakage circuit 8. In FIG. 4, the pseudo leakage circuit 8 is composed of one varistor 8C. When an overvoltage exceeding the limit voltage of the varistor 8C is applied to the pseudo earth leakage circuit 8, the pseudo earth leakage circuit 8 becomes conductive and the earth leakage protection plug trips. In the third embodiment, the operating voltage becomes rougher than that using the Zener diode 8A, but since the varistor is generally cheaper than the Zener diode, there is an advantage that the manufacturing cost is further reduced.

[0013]

As described above, according to the present invention, even if an overvoltage is applied due to incorrect wiring or incorrect use, accidents such as equipment burnout can be prevented by tripping the leakage protection plug. Moreover, since it is only necessary to add elements to the existing test circuit, it can be implemented at low cost.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an earth leakage protection plug showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of a main part of a leakage protection plug showing a first embodiment of the present invention.

FIG. 3 is a circuit diagram of a main part of an earth leakage protection plug showing a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a main part of an earth leakage protection plug showing a third embodiment of the present invention.

5A and 5B show the outer shape of a leakage protection plug, FIG. 5A is a side view, and FIG. 5B is a front view.

FIG. 6 is a circuit diagram of a conventional earth leakage protection plug.

[Explanation of symbols]

1 main circuit 2 main contacts 3 Zero-phase current transformer 4 Leakage detection circuit 5 Thyristor 6 trip coil 7 Test circuit 8 Pseudo leakage circuit 8A Zener diode 8B diode 8C Varistor

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5G004 AA01 AB02 BA08 CA08 DC10                       FA01                 5G030 XX04 YY13

Claims (4)

[Claims] 1. An unbalanced current in a main circuit is detected by a zero-phase current transformer, a main contact inserted in the main circuit is opened, the zero-phase current transformer is penetrated, and a test switch is used. Having a test circuit connected between the phases of the main circuit, when the test switch is pressed, a pseudo leakage current is passed through the test circuit, and when the pseudo leakage current is detected by the zero-phase current transformer, the main contact is opened. In the leakage protection plug to be opened, a pseudo leakage circuit is provided, which conducts when an overvoltage higher than a predetermined voltage of the main circuit is applied, and the pseudo leakage circuit is connected in parallel to the test switch. 2. The earth leakage protection plug according to claim 1, wherein the pseudo earth leakage circuit includes a plurality of Zener diodes connected in opposite directions. 3. The leakage protection plug according to claim 1, wherein the pseudo leakage circuit includes a Zener diode and a diode which are reversely connected to each other. 4. The earth leakage protection plug according to claim 1, wherein the pseudo earth leakage circuit includes a varistor.