Circuit breaker with arc extinguishing mechanism

A circuit breaker having an arc extinguishing mechanism includes a plurality of grids disposed in a longitudinal direction, each having protruding portions at both ends thereof so as to define a space therebetween, a fixing portion to support the grids, insulating plates fixed to both sides of the grids, a stator located below the grids, the stator including an arc runner and a stationary contact disposed at an upper side of the arc runner, and a mover contactable with or separated from the stationary contact with moving up and down within the space, wherein an interval between the insulating plates within the space is shorter than a width of the mover.

CROSS-REFERENCE TO RELATED APPLICATION

Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Patent Application No. 20-2011-0001489, filed on Feb. 22, 2011, the contents of which are hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This specification relates to a circuit breaker with an arc extinguishing mechanism, and particularly, to a circuit breaker with an arc extinguishing mechanism for extinguishing arc generated when a movable contactor is separated from a stationary contactor due to a fault current.

2. Background of the Invention

A circuit breaker is an electric device for protecting a circuit and a line by automatically breaking such circuit or line upon occurrences of an electric overload state or a short-circuit state. In general, current flowing over an electric circuit is generally divided into a rated current and a fault current which flows due to a breakdown like short-circuit, grounding, etc.

The fault current is drastically larger than the rated current, so it is difficult to be cut off. Accordingly, the circuit breaker is designed to block both the rated current and the fault current. A rated switch is able to merely block a current, which is as low as the rated current, so it is distinguished from the circuit breaker. An electric power system includes a power generator, a transformer, a power transmission line and the like. When desiring to suspend some of them, a current of the power generator or power transmission line desired to be suspended is blocked by a circuit breaker such that the power generator or power transmission line can be isolated from the electric power system. Also, when a breakdown such as short-circuit or grounding is caused in the system, an extremely large fault current flows over the system. If the system is left in that state, it may aggravate damage on the broken component or portion and the other may also be out of order due to large current. Thus, the circuit breaker is used for blocking the broken portion.

In general, the circuit breaker exhibits more excellent current limitation when it has superior arc extinguishing capability and takes a shorter time to break current.FIG. 1is a schematic view showing a structure of the related art circuit breaker,FIG. 2is a disassembled perspective view showing a structure of an arc extinguishing mechanism of the related art circuit breaker,FIG. 3is a view showing operations of the related art arc extinguishing mechanism, andFIG. 4is a planar view showing an exhausting direction of arc generated from the related art circuit breaker.

As shown inFIG. 1, the related art circuit breaker100includes a first stator110implemented as a conductor to induce current to flow inwardly, a mover130selectively contactable with the first stator110by a mechanical operation of a switching mechanism120, an arc extinguishing mechanism140to extinguish arc generated between contact points of the mover130and the first stator110, a connecting contactor150coupled with one end of the mover130, a second stator160connected to the connector150and implemented as a conductor to induce a current to flow outwardly, a trip mechanism170to operate the switching mechanism120by detecting a generation of a fault current and abnormal current, and a handle180to manually drive the switching mechanism120.

As shown inFIG. 2, the arc extinguishing mechanism140of the related art circuit breaker100includes a first stator141and a mover142. A stationary contact141aand a movable contact142aare brazed at the first stator141and the mover142, respectively. A rear end of the stationary contact141ais embossed to act as an arc runner141b. A position adjacent to the first stator141and the mover142is shown having an arc chute143. The arc chute143includes a plurality of grids143amade of a metal having ferromagnetism, and fixing plates143bmade of an insulating material to fix the grids143a. The first stator141, the upper grid144and the arc chute143are integrally assembled together and mounted in a case145made of an insulating material.

An operation of the arc extinguishing mechanism of the related art circuit breaker is described as follows.

Referring toFIG. 3, in the related art circuit breaker100, the stationary contact141aand the movable contact142aremain contacted while a rated current flows. However, when a fault current such as overcurrent or short-circuit current, is generated, the mover142is separated due to an electromagnetic repulsive force, which is generated between the stationary contact141aand the movable contact142a, thereby cutting off current. When the mover142is separated, arc is generated between the stationary contact141aand the movable contact142a. The generated arc is induced to the arc runner141bto flow to the arc chute143. The arc is segmented by the grids143aof the arc chute143, thereby increasing an arc voltage to be higher than a power source voltage, which limits the short-circuit current and results in extinguishing arc. Also, the arc extinguishing effect is obtained by arc extinguishing gas, which is generated from the insulating plates143bwhich fix the grids143bof the arc chute143.

However, in the arc extinguishing mechanism of the related art circuit breaker, after arc generated due to a rotary motion of the mover142flows to the arc chute143through the arc runner141b, when the arc is elongated within the arc chute143, an arc column is not induced up to the upper grid144, it is impossible to obtain a significant increase in an arc voltage. Also, the insulating plates143bfor supporting the grids143aare unable to generate significant extinguishing gas due to arc energy. Hence, it is impossible to expect an increase in the arc voltage in response to an increase in pressure. Also, referring toFIG. 4, the arc extinguishing mechanism of the related art circuit breaker extinguishes arc merely by segmenting arc into various directions a, b, c by the grids143aand cooling arc, so it takes a long time to extinguish arc and also arc heat gas is reversely exhausted in a direction d where the rotational shaft of the mover142is installed, which causes problems of arc reignition and damage on the movable contact142aand the stationary contact141a.

SUMMARY OF THE INVENTION

Therefore, to address the drawbacks of the related art, an aspect of the detailed description is to provide an arc extinguishing mechanism for a circuit breaker capable of uniformly distributing arc, generated upon breaking a fault current, into grids so as to improve arc extinguishing efficiency.

To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, there is provided a circuit breaker including a plurality of grids disposed in a longitudinal direction, each having protruding portions at both ends thereof so as to define a space therebetween, a fixing portion to support the grids, insulating plates fixed to both sides of the grids, a stator located below the grids, the stator including an arc runner and a stationary contact disposed at an upper side of the arc runner, and a mover contactable with or separated from the stationary contact with moving up and down within the space, wherein an interval between the insulating plates within the space is shorter than a width of the mover.

In accordance with the aspect, the interval between the pair of insulating plates can be shorter than a width of the mover, namely, end portions of the insulating plates can protrude into the space, so as to allow the generated arc to be more smoothly introduced into the grids and simultaneously increase an amount of arc extinguishing gas generated by the insulating plates, thereby improving an arc extinguishing performance.

Here, the insulating plates may include first insulating plates disposed at both sides of the grids, and second insulating plates coupled to the first insulating plates and extending into the space. Each of the second insulating plates may include a coupling portion coupled to the first insulating plate, and an inclined portion extending from the coupling portion toward the grids with an inclination.

Also, the second insulating plates may be located between the protruding portions of the grids and the mover.

In addition, the interval between the insulating plates within the space can be shorter than a width of the arc runner, to allow more arc to be introduced into the grids.

In accordance with the aspects of the present disclosure with the configuration, arc generated during a breaking operation can be introduced more into grids and a contact area between the arc and the insulating plates can be increased, resulting in enhancement of arc extinguishing efficiency.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 5is a perspective view showing one exemplary embodiment of a circuit breaker in accordance with this specification,FIG. 6is a sectional view of the one exemplary embodiment shown inFIG. 5, andFIG. 7is a planar view of the one exemplary embodiment shown inFIG. 5.

Referring toFIGS. 5 to 7, a circuit breaker10in accordance with the exemplary embodiment may include plural sheets of grids20laminated in a longitudinal (vertical) direction with predetermined intervals.

The grid20may be made of a metal having ferromagnetism. Protruding portion22may be formed at both ends at the front of each grid20based onFIG. 5. A space formed between the protruding portions22may define an arc extinguishing space24in which arc generated due to a longitudinal (vertical, up-and-down) motion of a mover to be explained later is diffused and extinguished. Here, an upper grid26may be located on the top of the grid20. The upper grid26may obscure the upper side of the arc extinguishing space24to prevent the generated arc from being leaked out of the top of the grid20.

A fixing portion30may be installed at the rear of the grids20. The fixing portion30may serve to fix the grids20such that the grids20can remain in the fixed state with the predetermined intervals. In addition, the fixing portion30may be secured with a circuit breaker main body (not shown).

First insulating plates40may be fixed to both side surfaces of the girds20. The first insulating plates40may prevent arc leakage to the outside in cooperation with the upper grid26and also serve to fix the grids20. The first insulating plates40may be made of a material, which is able to generate arc extinguishing gas when contacting arc, so as to rapidly extinguish such arc.

The first insulating plates40may be formed longer than the grids20such that their front sides can protrude from the front sides of the grids20. Second insulating plates50may be fixed onto the protruded portions. Each of the second insulating plates50, as shown inFIG. 5, may include a coupling portion52coupled to the first insulating plate40, and an inclined portion54extending from the coupling portion52with being inclined to the inside of the arc extinguishing space. Hence, an interval a between ends of the inclined portions54may be shorter than an interval between the coupling portions52.

A mover60may be installed at the front of the second insulating plates50. The mover60may have the same structure as the mover of the typical circuit breaker. The mover60may include a plurality of movable contactors62disposed in series.

A stator70may be disposed below the mover60. The stator70may include a stationary contact72contacting the mover60, and an arc runner74to induce arc generated during a breaking process. Here, referring toFIG. 5, the relation among the interval a between the inclined portions54, the width b of the arc runner74and the width c of the mover60may be explained as follows.

Hereinafter, description will be given of operations of the circuit breaker according to the one exemplary embodiment.

In a normal state that the mover60and the stator70contact each other to allow a current flow, when the mover60is separated by an electromagnetic repulsive force, which is generated between the stationary contact72and the mover60upon generation of a fault current due to a particular cause, arc is generated between the two electrodes. Here, the arc is induced to the arc runner74after staying at the stationary contact72for a short term of time. The arc induced to the arc runner74then generates arc extinguishing gas from the first and second insulating plates40and50, which define inner walls of the arc extinguishing space.

Here, the generated arc extinguishing gas compresses and elongates an arc column by pressure, which is instantaneously rapidly risen in the arc extinguishing space, so as to render an arc voltage high, thereby improving a current limitation performance (efficiency). The arc then rapidly moves into the grids20by an attractive force and pressure by a magnetism generated by the grids20, so as to be segmented and cooled.

Here, the second insulating plates50protrude into the arc extinguishing space, so the arc can generate the arc extinguishing gas by contacting the insulating plates50more rapidly. In addition, the inclined portions54of the second insulating plates50can additionally shield the arc extinguishing space. Accordingly, upon the arc generation, pressure within the arc extinguishing space can be further increased, which can make the arc diffused more rapidly into the grids20.

The inclined portions54of the second insulating plates50can also prevent the arc from being reversely exhausted toward the mover60. Consequently, metal particles, which are melted by heat gas and arc heat within the arc extinguishing space can be prevented from being exhausted toward the mover60. This may result in prevention of damages of the stationary contact72and the mover60and prevention of reignition due to the reverse exhaust of the arc, which is ended up with improvement of a current limitation effect.