Patent Description:
A DC circuit breaker includes: a fixed element having a fixed contact; and a movable element having a movable contact that is separable from the fixed contact. The DC circuit breaker performs opening between the contacts, to interrupt current. An arc generated in association with the opening is transferred from the contacts onto arc runners disposed in the vicinity of the contacts and is guided into an arc extinguishing chamber.

A plurality of arc extinguishing plates each formed by retaining a grid on an insulating plate are parallelly disposed at fixed intervals in the arc extinguishing chamber. The arc having arrived in the arc extinguishing chamber is divided by the arc extinguishing plates, and an arc voltage equal to or higher than a power supply voltage of a DC circuit is generated, whereby fault current is limited and interrupted.

Patent Document <NUM>, according to its abstract, states that a switch unit for a DC circuit is disclosed, which includes a first switch contact, and a second switch contact, which is movable between a first position, wherein the first switch contact contacts the second switch contact, and a second position, wherein the second switch contact is separated from the first switch contact. A positioning element to position an arc chute on the switch unit, the arc chute comprises a plurality of substantially parallel metal plates, the positioning element arranged to guide an arc, which is created between the first switch contact and the second switch contact, into the arc chute in an arc displacement direction in order to be extinguished. At least one gas emitting element, wherein at an interruption operation of the circuit breaker at its nominal current, the arc between the first switch contact and the second switch contact vaporizes a portion of the gas emitting layer.

Patent Document <NUM>, according to its abstract, relates to a breaker provided with an arc extinguishing mechanism with magnetic blowing and air-blowing functions, and mainly aims at solving the problems of poor breaking capacity and poor arc extinguishing effect due to the fact that the arc extinguishing mechanism of the breaker only has the magnetic blowing function or the air-blowing function. The breaker comprises a magnetic blowing device and a gas production plate, wherein the magnetic blowing device and the gas production plate are correspondingly arranged between a static contact and an arc extinguish chamber and are used for guiding an electric arc generated when a moving contact is separated from the static contact to the arc extinguish chamber.

Patent Document <NUM>, according to its abstract, states that a circuit breaker is provided that suppresses arc return and maintains a high arc voltage, thereby improving cut-off performance. An arc runner guides an arc generated between the contacts to an arc extinguishing chamber. In the arc extinguishing chamber, a plurality of grids and support plates are stacked. The grid has a notch portion that draws an arc at an end portion on the fixed contact and the movable contact side, and an insulating portion that is adjacent to a top portion of the notch portion and extends in the width direction.

Patent Document <NUM>, according to its abstract, states that an electromagnetic arc extinction apparatus comprises an arc chamber of insulating material and having an axial channel and electrodes aligned with the axis of the arc chamber and adapted to form a quenching arc in the form of a helix. The cavity of the arc chamber is bent along a helix to cause the quenching arc to be moved in a radial direction, the pitch of the cavity is at least <NUM> times lesser than the diameter of the arc chamber measured over the cross-section thereof. Conductor plates allow movement of arc roots.

Patent Document <NUM>, according to its abstract, states that, to break an arc within a short time and facilitate the miniaturization of a DC high speed circuit breaker, on the upper part of an arc chute having a pair of arc hones and arc guides, numbers of short and long vertically slender iron plates are alternately mounted at fixed intervals in such a manner that the lower ends are neatly arranged to constitute a cooling part. When an arc bridges numbers of the arc guides, the arc is blown up by the magnetic flux generated by the coil part of the central arc guide and entered into the cooling part, in which the arc is cooled by numbers of the iron plates, current-decreased, and extinguished within a short time.

Patent Document <NUM>, according to its abstract, states that, to provide an arc-extinguishing device enhancing arc-extinguishing performance, this arc-extinguishing device of a switch is constituted by stacking a plurality of grids each having a notch through which a moving electrode is passed at specified intervals. Each partition member is interposed between a pair of grids. The partition member is made of a synthetic resin member having insulating and arc-extinguishing properties, and has a notch through which the moving electrode is passed. An arc generating between a fixed electrode and the moving electrode when a circuit is opened is driven away toward the deepest part between grids so as to detour round the partition members. An arc route is made zigzag. The travelling distance of the arc is extended and arc-extinguishing performance is enhanced.

Patent Document <NUM> relates to an arc distinguisher for a circuit breaker.

Patent Document <NUM> relates to a switch.

In the conventional DC circuit breaker, an arc having arrived on an arc extinguishing plate in the arc extinguishing chamber may flow back in directions toward the contacts during the limitation and the interruption, to cause restrike of an arc. This results in elongation of the time taken to complete interruption and sometimes also leads to failure of interruption.

Considering this drawback, in Patent Document <NUM> and Patent Document <NUM>, an interrupting portion is provided between contacts and arc extinguishing plates in an arc extinguishing chamber. Consequently, hot gases generated by an arc having arrived in the arc extinguishing chamber are prevented from flowing back in directions toward the contacts. Thus, restrike of an arc in the vicinity of the contacts is inhibited. However, Patent Document <NUM> and Patent Document <NUM> have the following problem. That is, control of the flowing direction of an arc which has arrived on, and divided by, an arc extinguishing plate, is not sufficient, and thus backflow of the arc sometimes occurs, to cause failure of interruption.

The present disclosure has been made to solve the above problem, and an object of the present disclosure is to obtain a DC circuit breaker in which an interrupting portion for controlling the flow of an arc is provided on each of arc extinguishing plates in an arc extinguishing chamber, and which has so high interruption performance that no arc flows back from a location on a grid.

According to the present disclosure, a DC circuit breaker as defined in independent claim <NUM> is provided. Further embodiments of the invention are defined in the dependent claims. Although the invention is only defined by the claims, the below embodiments, examples, and aspects are present for aiding in understanding the background and advantages of the invention.

The same or corresponding portions in descriptions of embodiments and the drawings are denoted by the same reference characters.

The present embodiment will be described mainly with reference to <FIG>. <FIG> and <FIG> are each a schematic cross-sectional view showing the schematic structure of a DC circuit breaker <NUM> of the present embodiment. <FIG> shows a closed state between contacts, and <FIG> shows an opened state between the contacts. <FIG> is a perspective view showing several ones taken out from among arc extinguishing plates <NUM> disposed in an arc extinguishing chamber <NUM> of the DC circuit breaker <NUM>. <FIG> shows a state where interrupting portions <NUM> are formed on the arc extinguishing plates <NUM> which are each formed by an insulating plate <NUM> and grids <NUM>. <FIG> shows the back surface structure in <FIG>. <FIG> shows a modification of the arrangement of a grid <NUM>.

<FIG> shows the internal structure of the arc extinguishing chamber <NUM>. <FIG> shows a structure in which the arc extinguishing plates <NUM> which are each formed by the insulating plate <NUM> and the grids <NUM> and on which the interrupting portions <NUM> are formed, are stacked. <FIG> shows the flows, of hot gases, that are controlled by the interrupting portions <NUM>.

<FIG> and <FIG> are each a cross-sectional view of the DC circuit breaker <NUM> of the present embodiment and each show a schematic structure of the device. Of the DC circuit breaker <NUM> shown in each of <FIG> and <FIG>, the lower portion indicates an interruption mechanism portion <NUM> and the upper portion indicates the arc extinguishing chamber <NUM>.

<FIG> shows the interruption mechanism portion <NUM> in a closed state between the contacts. In this state, a movable element <NUM> is pressed by a closing actuator <NUM> in the leftward direction in <FIG>, and a movable contact <NUM> attached to the movable element <NUM> is in contact with a fixed contact <NUM> attached to a fixed element <NUM>. This enables electric conduction between an upper conductor <NUM> and a lower conductor <NUM>.

In the arc extinguishing chamber <NUM> at the upper portion in <FIG>, a space is present above the fixed contact <NUM> and the movable contact <NUM>, and a fixed-side arc runner <NUM> and a movable-side arc runner <NUM> are disposed on the left and right sides. Integrated products are disposed so as to be stacked over the fixed-side arc runner <NUM> and the movable-side arc runner <NUM>. Each integrated product is composed of: grids <NUM> which have electrical conductivity and have flat plate shapes; an insulating plate <NUM> on which the grids <NUM> are disposed and retained; and interrupting portions <NUM> which are each made of resin and each formed in a projecting shape in the form of a line to prevent backflow of hot gases.

In the present embodiment, each member disposed in the arc extinguishing chamber <NUM> and composed of the grids <NUM> and the insulating plate <NUM> is referred to as an arc extinguishing plate <NUM>. Meanwhile, each portion disposed on the arc extinguishing plate <NUM> and having a projecting shape in the form of a line is referred to as an interrupting portion <NUM>.

In <FIG>, the portion enclosed by the broken line in the arc extinguishing chamber <NUM> represents the arc extinguishing plate <NUM>. In the arc extinguishing plate <NUM>, the grids <NUM> are attached to the upper surface of the insulating plate <NUM>, and each interrupting portion <NUM> is further formed on the insulating plate <NUM> so as to originate from an edge of the arc extinguishing plate <NUM>.

The interrupting portion <NUM> on the insulating plate <NUM> can be formed integrally with the insulating plate <NUM>. Alternatively, the interrupting portion <NUM> can be formed as a separate member and attached on the insulating plate <NUM>.

The order of stacking of the interrupting portion <NUM>, and the insulating plate <NUM> and the grids <NUM> which compose the arc extinguishing plate <NUM>, is merely an example, and it is also possible to change the order of the insulating plate <NUM> and the grids <NUM> as described later. In addition, although the interrupting portions <NUM> are formed on the insulating plate <NUM> in the present embodiment, the interrupting portions <NUM> can be formed on the grids <NUM>.

It is noted that <FIG> shows a closed state, and thus, in this state, electric conduction is present between the fixed contact <NUM> and the movable contact <NUM> and no arc has occurred. A flow at the time of generation of an arc will be described with reference to <FIG> and the like.

<FIG> shows the interruption mechanism portion <NUM> in an opened state.

When fault current flows through the interruption mechanism portion <NUM>, a detector <NUM> disposed on the lower conductor <NUM> detects the fault current, and a latch <NUM> retaining the movable element <NUM> is released by the closing actuator <NUM>. Consequently, the movable element <NUM> retaining the movable contact <NUM> is moved. Thus, opening occurs between the fixed contact <NUM> and the movable contact <NUM> in a state where current is being applied. At the time of the opening, an arc <NUM> is generated between the fixed contact <NUM> and the movable contact <NUM>. It is noted that the stage in which the arc <NUM> is generated in the opened state is referred to as emergence and is, in some cases, distinguished from other stages of the arc <NUM>.

The arc <NUM> having emerged between the contacts moves between the fixed-side arc runner <NUM> and the movable-side arc runner <NUM>. This stage is referred to as transference of an arc <NUM>. Then, the arc <NUM> moves into the arc extinguishing chamber <NUM> owing to influences of: electromagnetic forces generated by currents flowing through the fixed-side arc runner <NUM> and the movable-side arc runner <NUM>; and the flows of electrically conductive hot gases. This stage is referred to as travel of an arc <NUM>.

The arc <NUM> having travelled into the arc extinguishing chamber <NUM> arrives at intervals between the arc extinguishing plates <NUM>. The stage in which the arc is divided between the plurality of arc extinguishing plates <NUM> may be referred to as division of an arc <NUM>. If the divided state is maintained, an arc voltage increases to become equal to or higher than a power supply voltage of a circuit. Consequently, limitation and interruption are performed.

In the present embodiment, the interrupting portions <NUM> are, as shown in <FIG>, formed on surfaces of the insulating plates <NUM> of the arc extinguishing plates <NUM> so as to originate from edges of the arc extinguishing plates <NUM> in order to prevent the arc <NUM> from flowing back from the intervals between the arc extinguishing plates <NUM> and prevent restrike of an arc due to hot gases.

Hereinafter, the arrangement, the structures, functions, and the like of the interrupting portions <NUM> will be described with reference to <FIG>.

<FIG> illustrates the arrangement and the structures of the interrupting portions <NUM> formed on the insulating plates <NUM> of the arc extinguishing plates <NUM>. Some of the plurality of arc extinguishing plates <NUM> disposed in the arc extinguishing chamber <NUM> have been taken out and shown.

<FIG> shows the back surface structure in <FIG>. <FIG> shows a modification of the structure of the arc extinguishing plate <NUM>, in which the arrangement of a grid <NUM> is changed.

<FIG> shows a schematic structure of the arc extinguishing plates <NUM> disposed in the arc extinguishing chamber <NUM> and partially shows, together with the schematic structure, the fixed-side arc runner <NUM>, the movable-side arc runner <NUM>, and the like.

As shown in <FIG>, the interrupting portions <NUM> are formed on the insulating plates <NUM> of the arc extinguishing plates <NUM> in the present embodiment. When each arc extinguishing plate <NUM> is disposed in the arc extinguishing chamber <NUM>, the arc extinguishing plate <NUM> is disposed such that the surface on which the interrupting portions <NUM> are formed faces downward as shown in <FIG>.

It is noted that <FIG> shows that the insulating plate <NUM> side on which the interrupting portions <NUM> are formed faces upward for facilitating explanations.

Although each arc extinguishing plate <NUM> is composed of the grids <NUM> and the insulating plate <NUM> and has a structure in which the interrupting portions <NUM> are formed, no grids <NUM> can be viewed in <FIG> owing to the view angle.

In <FIG>, a quadrangular opening in which the traveling arc <NUM> flows is formed at the center of each insulating plate <NUM>. The grids <NUM> are stacked so as to protrude into the opening. As shown in <FIG> and <FIG>, the opening is located directly above the fixed contact <NUM> and the movable contact <NUM>. That is, as shown in <FIG>, the arc <NUM> generated owing to an opening operation between the fixed contact <NUM> and the movable contact <NUM> flows into the opening owing to the flows of hot gases and electromagnetic forces of the fixed-side arc runner <NUM> and the movable-side arc runner <NUM>. Then, the arc arrives at the intervals between the arc extinguishing plate <NUM>, whereby the arc is divided by the grids <NUM> disposed on the arc extinguishing plates <NUM>.

As shown in <FIG>, each interrupting portion <NUM> is disposed in the form of a line and has a projecting shape. The interrupting portion <NUM> is attached to the insulating plate <NUM> by bringing side surfaces of the projecting-shape portion into close contact with the insulating plate <NUM>. Further, the interrupting portion <NUM> is disposed substantially in a radial pattern so as to originate from an edge of the quadrangular opening formed at the center of the insulating plate <NUM> of each arc extinguishing plate <NUM> and so as to face the outer side of the insulating plate <NUM> and extend to an edge on the outer peripheral side of the arc extinguishing plate <NUM>.

Regarding the locations at which the interrupting portions <NUM> are to be formed, the interrupting portions <NUM> are preferably formed in regions in which the grids <NUM> are disposed on the arc extinguishing plate <NUM>. Specifically, the interrupting portions <NUM> are preferably formed on the surfaces of the grids <NUM> stacked on the arc extinguishing plate <NUM> or at locations that: are present on a surface, of the arc extinguishing plate <NUM>, that is opposite to the surface on which the grids <NUM> are formed; and correspond to the locations at which the grids <NUM> are formed.

Further, if the interrupting portions <NUM> are disposed so as to originate from regions in which the grids <NUM> protrude into the quadrangular opening in the arc extinguishing plate <NUM> shown in <FIG>, an effect of controlling arcs can be improved.

The thickness of each interrupting portion <NUM> takes the same value as the thickness of each of the grids <NUM> and the insulating plate <NUM> so as not to inflict any great influence on the stacking structure when the arc extinguishing plates <NUM> are disposed in the arc extinguishing chamber <NUM> in a mutually stacked manner.

Detailed effects of each interrupting portion <NUM> exhibited when the divided arc <NUM> flows into the intervals between the arc extinguishing plates <NUM>, will be described later. Since the interrupting portion <NUM> is disposed in a radial pattern so as to face the outer side of the insulating plate <NUM>, the interrupting portion <NUM> is advantageous in diffusing hot gases. In addition, the interrupting portions <NUM> are each bent at an obtuse angle and have bent portions disposed so as to face each other. Thus, projecting portions at the bent portions make it possible to prevent backflow of hot gases. Therefore, re-emergence of an arc can be prevented.

<FIG> shows the back surface structure of the arc extinguishing plates <NUM> shown in <FIG>. In the structure, projecting portions are formed at center portions in the longitudinal direction of the arc extinguishing plates <NUM> at which no grids <NUM> are disposed. The effect of controlling the arc <NUM> is small in the case of using only these projecting portions. However, if the projecting portions are used in combination with the interrupting portions <NUM> shown in <FIG>, a favorable effect of controlling the arc can be expected.

<FIG> is a modification in which a grid <NUM> is disposed between the insulating plate <NUM> and interrupting portions <NUM>. This arrangement also makes it possible to obtain the favorable effect of controlling the arc.

<FIG> shows the flows of hot gases and the arc <NUM> having travelled to the intervals between the arc extinguishing plates <NUM>. An effect of each interrupting portion <NUM> on the arc <NUM> divided by the arc extinguishing plates <NUM>, will be described with reference to <FIG>. Similarly to <FIG>, <FIG> also shows, for explanations, the state in which the surface of the insulating plate <NUM> of each arc extinguishing plate <NUM> on which the interrupting portions <NUM> are formed faces upward. It is noted that the divided arc <NUM> spreads in all directions such that, since the shape of the insulating plate <NUM> of the arc extinguishing plate <NUM> is symmetric about the quadrangular opening at the center, the diffusion of the arc <NUM> also has symmetry. Considering this, description will be given with the direction being limited to one direction, for facilitating explanations.

The arc <NUM> having emerged upon the opening between the fixed contact <NUM> and the movable contact <NUM> moves and travels into the quadrangular opening portion at the center in <FIG>. The arc <NUM> having travelled past the fixed-side arc runner <NUM> and the movable-side arc runner <NUM> is influenced by the flows of hot gases and the electromagnetic forces of the grids <NUM> of the arc extinguishing plate <NUM> and moves along the white arrow <NUM> which indicates the travel of the arc <NUM> in <FIG>. Consequently, the arc <NUM> turns into a divided arc <NUM>.

Further, hot gases generated by the arc <NUM> and having high electrical conductivity move along the surface of the arc extinguishing plate <NUM> and are diffused in a radial pattern, as indicated by the black arrows <NUM> which indicate the flows of the hot gases.

If no interrupting portion <NUM> is disposed on the insulating plate <NUM>, parts of the diffused hot gases may pass around from sides and may move again in directions toward the center of the arc extinguishing plate <NUM>. In this case, a situation in which restrike of an arc or the like occurs is also conceivable. However, as shown in <FIG>, the interrupting portions <NUM> which have projecting shapes in the forms of lines bent at obtuse angles and which have the bent portions facing each other are formed on the insulating plate <NUM> of the arc extinguishing plate <NUM> so as to originate from edges of the opening at the center and so as to extend to edges on the outer peripheral side of the arc extinguishing plate <NUM>. Thus, hot gases are diffused as indicated by the black arrows <NUM>, and a hot gas passing around from a side is received by one of the bent portions, whereby the hot gas can be diffused in a radial pattern to the outer side of the arc extinguishing plate <NUM>.

By the above features, backflow of the hot gases generated owing to the divided arc <NUM> can be prevented, and the hot gases can be diffused to the outer side of the arc extinguishing plate <NUM>. Therefore, the hot gases can be ejected to the vicinity of a housing of the arc extinguishing chamber <NUM>. Consequently, restrike of an arc can be prevented, and an interruption characteristic of the DC circuit breaker <NUM> can be improved.

In the present embodiment <NUM>, each interrupting portion <NUM> having a bent shape is formed on the lower surface of the insulating plate <NUM> with use of the same resin material as that of the insulating plate <NUM>. However, the present disclosure is not limited thereto. The same advantageous effects can be obtained also by making an interrupting portion <NUM> having a linear or bent projecting shape with use of a different insulating material and attaching the interrupting portion <NUM> to the insulating plate <NUM> by pasting or screwing.

In addition, although a configuration in which the interrupting portions <NUM> are attached to the lower surface of the insulating plate <NUM> of each arc extinguishing plate <NUM> has been described in the present embodiment, the same advantageous effects can be obtained even when an interrupting portion <NUM> having a linear or bent projecting shape is formed on the upper surface of the insulating plate <NUM>.

In addition, although each interrupting portion <NUM> is formed on the insulating plate <NUM> with use of an insulating material in the present embodiment <NUM>, it is also possible to: form an interrupting portion <NUM> having a linear or bent projecting shape on each grid <NUM> of the arc extinguishing plate <NUM> with use of a metal material; and bring side surfaces of the interrupting portion <NUM> into close contact with the grid by welding to fix the interrupting portion <NUM>. Alternatively, the interrupting portion <NUM> can be formed also by half-blanking the grid <NUM> through press working.

Further, although the arc extinguishing chamber <NUM> in which each arc extinguishing plate <NUM> composed of the insulating plate <NUM> and the grids <NUM> is disposed horizontally has been used in the present embodiment <NUM>, the same advantageous effects can be obtained by forming the interrupting portions <NUM> on the insulating plate <NUM> or the grids <NUM> in the same manner, also in an arc extinguishing chamber <NUM> in which each arc extinguishing plate <NUM> composed of the insulating plate <NUM> and the grids <NUM> is disposed in the vertical direction as in a DC circuit breaker <NUM> shown in a cross-sectional view in <FIG>.

<FIG> shows the flows of hot gases and an arc <NUM> having travelled to the intervals between the arc extinguishing plates <NUM> disposed in the vertical direction.

An arc <NUM> having emerged upon opening between the fixed contact <NUM> and the movable contact <NUM> moves and travels into the opening portion at the center in <FIG>. The arc <NUM> is influenced by the flows of hot gases and the electromagnetic forces of the grids <NUM> of each arc extinguishing plate <NUM> and moves along the white arrow <NUM> which indicates the travel of the arc <NUM> in <FIG>. Consequently, the arc <NUM> turns into a divided arc <NUM>.

Further, hot gases generated by the arc <NUM> and having high electrical conductivity can be moved along the surface of the arc extinguishing plate <NUM> and diffused in a radial pattern, as indicated by the black arrows <NUM> which indicate the flows of the hot gases.

In the present embodiment <NUM>, the interrupting portions <NUM> having the bent portions disposed so as to face each other have been used. In addition, an example has been shown in which four interrupting portions <NUM> originating from edges of the opening at the center and extending to edges on the outer peripheral side are used on one arc extinguishing plate <NUM>. However, since the important point about the interrupting portions <NUM> formed on the arc extinguishing plate <NUM> is to move hot gases to the outer side, the shape of each interrupting portion <NUM> is not limited to a bent shape and a projecting shape in the form of a line. Specifically, a cylindrical shape, a prismatic shape, or the like having proportions that greatly differ in the longitudinal direction and the lateral direction may be employed, and the interrupting portion <NUM> does not necessarily have to be so long as to extend to an edge on an outer peripheral side. Furthermore, the number of the interrupting portions <NUM> is also not limited to four and only has to be one or more.

In embodiment <NUM>, an example has been shown in which: the plurality of arc extinguishing plates <NUM> each obtained by superposing the insulating plate <NUM> and the grids <NUM> are disposed in the arc extinguishing chamber <NUM>; and the interrupting portions <NUM> are formed on a surface of the insulating plate <NUM> or each grid <NUM>.

The present embodiment is basically the same as embodiment <NUM> in that each interrupting portion <NUM> is formed so as to originate from an edge of the opening at the center. Meanwhile, the present embodiment is characterized in that interrupting portions <NUM> are formed so as to be in contact with side surfaces of the fixed-side arc runner <NUM> and the movable-side arc runner <NUM>.

<FIG> is a perspective view of an arc extinguishing plate <NUM> at a lowermost stage connected to the fixed-side arc runner <NUM> and the movable-side arc runner <NUM>. <FIG> shows a state where the movable contact <NUM>, the movable element <NUM>, and the upper conductor <NUM> are disposed beneath the arc runners.

The fixed-side arc runner <NUM> and the movable-side arc runner <NUM> are fixed to a surface of the arc extinguishing plate <NUM> such that a part of each arc runner protrudes to the said surface. The interrupting portions <NUM> having bent shapes are disposed in a radial pattern on the surface of the insulating plate <NUM> such that end portions of the interrupting portions <NUM> are connected to the protruding portions of the arc runners.

An arc <NUM> having emerged upon opening between the movable contact <NUM> and the fixed contact (not shown) is transferred between the arc runners, and an arc <NUM> having travelled to a location on the arc extinguishing plate <NUM> at the lowermost stage shown in <FIG> moves in a direction toward the outer periphery owing to the flows of hot gases and electromagnetic force of each grid <NUM> in the same manner as in <FIG>. Consequently, the arc <NUM> turns into a divided arc <NUM>. Further, the arc <NUM> generates hot gas having high electrical conductivity which is prevented by the interrupting portion <NUM> from flowing back, to be diffused in a radial pattern in the direction toward the periphery of the insulating plate <NUM> of the arc extinguishing plate <NUM>.

By the above features, backflow of the hot gases generated owing to the divided arc <NUM> can be prevented, and the hot gases can be diffused to the outer side of the insulating plate <NUM> of the arc extinguishing plate <NUM>. Therefore, the hot gases can be ejected to the vicinity of the housing of the arc extinguishing chamber <NUM>. Further, in the present embodiment, a region in the vicinity of each arc runner is a region in which the arc <NUM> travels at high speed, and thus the effect of preventing the backflow can also be notably obtained. Consequently, restrike of an arc can be prevented, and the interruption characteristic of the DC circuit breaker <NUM> can be improved.

In the present embodiment, an example has been shown in which the interrupting portions <NUM> are formed on the insulating plate <NUM>, at the lowermost stage in the arc extinguishing chamber <NUM>, which is connected to the arc runners. However, the present disclosure is not limited thereto, and the same advantageous effects can be obtained also by forming the interrupting portions <NUM> on the grids <NUM>.

In addition, the disposition locations for the interrupting portions <NUM> are not limited to such locations that the interrupting portions <NUM> are in contact with side surfaces of the arc runners, and only has to be locations near the arc runners. Thus, the same advantageous effects are exhibited also by forming the interrupting portions <NUM> on the inner wall of the arc extinguishing chamber <NUM> retaining the fixed element <NUM> and the movable element <NUM> or on a frame portion forming a circuit breaker body.

Claim 1:
A DC circuit breaker comprising:
an interruption mechanism portion configured to perform opening between a fixed contact (<NUM>) and a movable contact (<NUM>), to interrupt DC current;
an arc extinguishing plate (<NUM>) obtained by superposing an insulating plate (<NUM>) and a grid (<NUM>) which has electrical conductivity and has a plate shape, the arc extinguishing plate (<NUM>) having a surface oriented in a horizontal direction; and
an arc extinguishing chamber (<NUM>) in which the arc extinguishing plate (<NUM>) has an opening at a center portion thereof, and a plurality of the arc extinguishing plates (<NUM>) are accommodated in a stacked state at fixed intervals such that edges that delimit the openings are located above the fixed contact (<NUM>) and the movable contact (<NUM>), wherein
a fixed-side arc runner (<NUM>) and a movable-side arc runner (<NUM>),
characterized in that the fixed-side arc runner (<NUM>) and the movable-side arc runner (<NUM>) are fixed and protrude from the opening of the arc extinguishing plate (<NUM>) at a lowermost stage, have side surfaces on which an interrupting portion (<NUM>) having a projecting-shape side surface brought into close contact with a surface of the arc extinguishing plate (<NUM>) is disposed such that ends of the interrupting portion (<NUM>) are in contact with the side surfaces of the fixed-side arc runner (<NUM>) and the movable-side arc runner (<NUM>).