JPH0973854A - Earth leakage breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an earth leakage breaker which cannot pass arc gas well to the load side from being filled with the arc gas by smoothing the discharge of the arc gas from the power supply side. SOLUTION: In this earth leakage breaker in which an arc gas discharge opening 17 opposite to an arc-extinguishing chamber 1 is provided with a flexible shield plate 2 that is deformed by gas pressure and a back plate 3 supporting the plate 2 from inside, the back plate 3 is formed into a U shape supporting only the periphery of the shield plate 2 and allowing arc gas to directly pass through. The back plate facilitates the discharge of the arc gas as compared with conventional ones provided with several exhaust holes, and since a zero-phase current transformer and an electronic circuit for amplifying its outputs are arranged on the load side, even such an earth leakage breaker as not able to pass the arc gas well to the load side can be prevented from being deteriorated in insulation as the arc gas fills an outer casing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earth leakage circuit breaker, and more particularly to an earth leakage circuit breaker designed to promote discharge of arc gas from a power source side.

[0002]

2. Description of the Related Art FIG. 5 is an exploded perspective view of essential parts near an arc extinguishing chamber in a conventional earth leakage breaker. In the figure, a shield plate 2 is provided so as to face an arc extinguishing chamber 1 surrounding a fixed / movable contact (not shown).
And a back plate 3 that supports this from the inside.
The shielding plate 2 is made of a flexible insulating thin plate, and the lower part thereof is formed in a wide convex shape. Further, the back plate 3 is formed in a rectangular shape from a strong insulating plate, and a plurality of exhaust holes 4 are formed in the upper part. The shield plate 2 and the back plate 3 are inserted into a groove formed across the case and the cover to face the arc gas discharge port of the outer casing of the earth leakage circuit breaker, which is not shown in the figure, and are normally inserted in the arc gas discharge port. Is closed to prevent foreign matter from entering the earth leakage breaker.

In this case, the left and right edges of the back plate 3 are inserted into the groove over the entire height, but the shield plate 2 is held by inserting only the lower wide portion into the groove on the case side and the upper side. It is a free end. Then, when the arc gas is generated when the current is cut off, the arc gas discharged from the arc gas discharge port acts on the shield plate 2 through the exhaust hole 4 of the back plate 3, and the shield plate 2 receiving this gas pressure causes the fixed end on the case side to move. The upper side of the fulcrum is curved as shown by the chain line in the figure to allow the arc gas to pass through.

[0004]

By the way, the earth leakage circuit breaker is a wiring circuit breaker having an earth leakage protection function added thereto. However, a zero-phase current transformer for earth leakage detection and an electronic device for amplifying its output are used. Circuits and the like are generally arranged at the load-side end of the outer box. Therefore, the arc gas generated when the current is interrupted is blocked by the zero-phase current transformer and the electronic circuit, and the escape to the load side is worse than that of the wiring breaker. Therefore, in the earth leakage circuit breaker, the arc gas is normally discharged only from the power source side. However, in the conventional configuration as shown in FIG. 5, the discharge amount of the arc gas is limited by the opening area of the exhaust hole 4, so that it is large. When the current is cut off, there is a problem that the outer box is filled with arc gas and soot or molten metal powder adheres to the inner surface of the case or the cover to cause a decrease in insulation resistance. Especially in recent years, there is a tendency for the outer box of the earth leakage breaker to be made compact in order to obtain compatibility of installation of the earth leakage breaker and the breaker for wiring, and the arc gas discharge performance from the power supply side of the earth leakage breaker is improved. Demand is growing. Then, the subject of this invention is improving the arc gas discharge | emission performance from a power supply side, without impairing the foreign substance intrusion prevention function by a shielding plate.

[0005]

In order to solve the above problems, the present invention provides an arc gas discharge port facing the arc extinguishing chamber at the power source side end of an earth leakage breaker outer box consisting of a case and a cover. At the same time, the arc gas discharge port is normally closed by a flexible shield plate inserted in a groove that straddles the case and the cover, and a strong back plate having an exhaust hole that supports the shield plate from the inside. When the current is cut off, the shield plate receives the gas pressure of the arc gas discharged from the arc gas discharge port through the exhaust hole of the back plate, and the upper side is curved with the fixed end of the case side as a fulcrum to pass the arc gas. In the earth leakage circuit breaker, the back plate has a U-shape that supports only the peripheral edge of the shield plate.

By making the back plate U-shaped in this way, the back plate is almost transparent to the arc gas,
Exhaust of arc gas is not obstructed by the back plate.
On the other hand, since the periphery of the shield plate is supported by the back plate, there is little risk of being pushed into the arc gas discharge port even if some force acts from the outside, and the shield function is well maintained against the intrusion of foreign matter. Further, by mounting the cover plate on the upper part of the arc extinguishing chamber, the diffusion of the arc gas toward the load side from the upper part of the arc extinguishing chamber is suppressed, and the discharge of the arc gas to the power supply side is further promoted.

[0007]

1 to 4 show an embodiment of the present invention. FIG. 1 is a perspective view of an arc gas discharge port, FIG. 2 is an exploded perspective view thereof, and FIG. 3 is an arc extinguishing chamber. FIG. 4 is a perspective view showing a method of mounting the cover plate, and FIG. 4 is a vertical sectional view of the three-pole earth leakage breaker. First, in FIG. 4, the earth leakage breaker is configured such that each mechanism is housed in an outer box of molded resin composed of a case 5 and a cover 6.
A fixed contactor 8 integrated with the power source side terminal 7, a movable contactor 9 that comes into contact with the fixed contactor 8 through a contact, a fixed conductor 10 that makes sliding contact with the movable contactor 9, and an overcurrent trip device 11 screwed to the fixed conductor 10. Through the heater conductor 11a and the relay conductor 12 joined to the heater conductor 11a, and flows to the load-side terminal 13 integrated with the heater conductor 11a.

Between the overcurrent trip device 11 and the load-side terminal 13, a zero-phase current transformer 1 having a relay conductor 12 as a primary conductor is provided.
4 and an electronic circuit 15 for amplifying its secondary output are arranged. When the energized current becomes an overcurrent state, the overcurrent trip device 11 operates and strikes the trip crossbar 16 to open the movable contact 9. When a leakage occurs, a secondary output is generated in the zero-phase current transformer, and the trip coil unit (not shown) is driven by the output from the electronic circuit 15 that amplifies the secondary output, and the trip crossbar 16 is also hit to move the movable contactor. 9 opens. When the movable contact 9 is separated, an arc is generated between the movable contact 9 and the fixed contact 8, and at the same time, high-temperature arc gas is generated.

Therefore, the arc-extinguishing chamber 1 is arranged so as to surround the fixed / movable contacts 8 and 9, and the arc gas discharge port 17 opening to the power supply side terminal 7 side is provided in a portion of the outer box facing the arc-extinguishing chamber 1.
Is provided across the case 5 and the cover 6. A shield plate 2 and a back plate 3 that supports the shield plate 2 from the inside are arranged at the arc gas discharge port 17. Similarly, an arc gas discharge port 18 is also provided at the load side end of the outer box, but there is a zero-phase current transformer 14 and an electronic circuit 15 on the load side of the earth leakage breaker to prevent the flow of arc gas. Because
In the illustrated earth leakage breaker, the arc gas discharge port 18 on the load side is closed by mounting a thick shielding plate 19.

In FIG. 1, the shield plate 2 and the back plate 3 of the arc gas discharge port 17 are inserted into a pair of left and right grooves 20 extending over a case 5 and a cover 6 (not shown in FIG. 1). Is held. As shown in FIG. 2, the shielding plate 2 is formed of a flexible thin fiber plate and has a convex contour as in the conventional example of FIG. On the other hand, the back plate 3 that supports the shielding plate 2 from the inside is made of a thick fiber plate containing glass fibers, and is formed in a U-shape that supports only the peripheral portion of the shielding plate 2 as illustrated. The width A of the lower wide portion of the shielding plate 2 and the width B of the back plate 3 are equal (A = B), and the upper width C of the shielding plate 2 is larger than the opening width D of the back plate 3 (C > D). The shield plate 2 and the back plate 3 are overlapped with each other and inserted into the groove 20 in which the distance between the opposing groove bottoms is slightly larger than the width dimensions A and B, and the shield plate 2 has only the lower wide portion in the groove 20. Held in.

On the other hand, the arc-extinguishing chamber 1 is constructed by laminating and supporting a plurality of arc-extinguishing grids 22 made of magnetic plates on a pair of left and right side walls 21 made of fiber plates at appropriate intervals. It is joined to the side wall 21 by caulking. The left and right side walls 21 of the arc extinguishing chamber 1 are located slightly inside the opening of the back plate 3. A cover plate 23 is provided above the arc-extinguishing chamber 1.
Is attached. The cover plate 23 is made of a fiber plate, and is provided at one end with a mounting arm 23a that projects left and right. The cover plate 23 is held in the arc-extinguishing chamber 1 by inserting the mounting arm 23a into the hole 21a of the side wall 21. The cover plate 23 is elastically curved as shown in FIG. 3, and the mounting arm 23a is inserted into the hole 21a.

In the earth leakage circuit breaker shown in the above-mentioned embodiment, when arc gas is generated as the movable contact 9 is opened, the shielding plate 2 is easily deformed to the outside by the gas pressure as shown in FIG. Arc gas is discharged from the discharge port 17 through the opening of the back plate 3 as indicated by an arrow. that time,
Since the back plate 3 is almost transparent to the arc gas, it does not hinder the discharge of the arc gas unlike the conventional back plate having a limited exhaust hole area. Therefore, the arc gas is immediately discharged to the outside without going to the load side in the outer box, so that high-pressure gas does not fill the outer box and soot or molten metal powder does not adhere to the inner surface of the case or the cover. On the other hand, since the U-shaped back plate 3 supports the peripheral portion of the shield plate 2 from the inside, even if some external force acts on the shield plate 2 from the outside, the thin shield plate 2 deforms and the arc gas discharge port 1
7 is prevented from entering.

Further, since the upper part of the arc extinguishing chamber 1 is covered with the cover plate 23, the diffusion of the arc gas from the upper part of the arc extinguishing chamber 1 toward the load side is suppressed at the moment when the arc gas is generated, and the arc gas to the power source side is suppressed. The discharge of arc gas is further promoted. The cover plate 23 is in contact with the protrusion 6a of the cover 6 as shown in FIG. 4, and the lifting of the end portion on the opposite side of the mounting arm 23a is suppressed.

[0014]

According to the present invention, since the arc gas is easily discharged to the power source side, even in the earth leakage breaker in which the arc gas is not easily discharged to the load side, the high pressure gas is filled in the outer box and the insulation property is improved. Is effectively prevented. In that case, by mounting a cover plate on the upper part of the arc extinguishing chamber, the diffusion of the arc gas to the load side can be further suppressed.

[Brief description of drawings]

FIG. 1 is a perspective view of an essential part showing an embodiment of the present invention.

FIG. 2 is an exploded perspective view of FIG.

FIG. 3 is a perspective view showing a method of attaching a cover plate to the arc extinguishing chamber.

FIG. 4 is a vertical cross-sectional view of an earth leakage breaker including the shield plate and the back plate of FIG.

FIG. 5 is an exploded perspective view of essential parts showing a conventional example.

[Explanation of symbols]

 1 arc-extinguishing chamber 2 shield plate 3 back plate 5 case 6 cover 14 zero-phase current transformer 15 electronic circuit 17 arc gas discharge port 20 groove 23 cover plate

Claims (2)

[Claims] 1. An arc gas discharge port is provided at an end portion on the power source side of an earth leakage circuit breaker outer box including a case and a cover, the arc gas discharge port facing the arc extinguishing chamber, and the arc gas discharge port straddling the case and the cover. A flexible shield plate inserted in the groove and a strong back plate having an exhaust hole that supports the shield plate from the inside are normally closed, and when the current is cut off, the shield plate is the exhaust hole of the back plate. In the earth leakage circuit breaker, which receives the gas pressure of the arc gas discharged from the arc gas discharge port through the arc gas and allows the arc gas to pass through with the fixed end of the case side as a fulcrum, the upper plate is curved, and the back plate is a peripheral portion of the shielding plate. An earth leakage circuit breaker characterized by being formed in a U shape that supports only the chisel. 2. The earth leakage breaker according to claim 1, wherein a cover plate made of an insulating plate is attached to an upper portion of the arc extinguishing chamber.