Arc chute for a direct current switching device

Abstract

The invention discloses an arc chute for a direct current switching device, comprising: at least one stack formed by a plurality of substantially parallel metallic splitter plates (1); at least one stack formed by a plurality of substantially parallel insulation plates (3), the edges of the insulation plates (3) facing the edges of the splitter plates (1); a housing (2) made of electrically insulating material surrounding the at least one stack of splitter plates (1) and the at least one stack of insulation plates (3), wherein each of the splitter plates (1) includes a base part (11) and two legs (12) extending from two opposite sides of the base part (11), whereby the legs (12) on each side of the base part (11) also form a stack, and whereby each stack of the legs (12) is covered by insulation barrier (5) from their internal side, from their bottom side and from the lateral side of the most external splitter plates (1). The insulation barrier (5) comprises partition walls (4), the partition walls (4) being made of electrically insulative and heat resistant material, whereby partition walls (4) are formed as insulation sheets arranged in a spaced relation in a stack, meshing with each stack of the legs (12) and separating the legs (12) from each other. The invention allows to prevent arc reignition below the splitter plates and between the legs of splitter plates, and to protect the legs and bottom area of side walls against the direct contact with burning arc.

Description

Technical Field

[0001] The invention belongs to the field of electrical switching devices with arc chutes for arc quenching. More particularly, the invention relates to an arc chute for direct current (DC) switching device, especially circuit breaker.Background

[0002] Circuit breakers are devices used to interrupt the electric current flow especially in the case of abnormal operating conditions, for example current overload. When a fault occurs, a circuit breaker interrupts the current by moving the contacts apart. Upon separation of the contacts, an electric arc is generated between them. An electric arc is the discharge of electric current through gas or air. Electric arc or arc discharge generates a large amount of heat, which can cause damage to the contacts by melting them, as well as it can cause damage to other components of the circuit breaker. Moreover, as the arc temperature is very high, when a surrounding structure is melted and broken, a metal powder or soot of carbon is produced, which adheres to a main contact. Thus, a contact resistance at an adhering portion is increased, and there is a possibility that energization fault occurs. According to that, frequent condition checks of main contact are required, and the adhering portion needs to be frequently removed.

[0003] Therefore, to minimize the damage, the arc needs to be safely and rapidly extinguished, and the current needs to be interrupted as soon as possible. For this purpose, arc chutes are used which are placed near the circuit breaker contacts. Thus, arc chutes are one of the key components of circuit breakers - they protect the circuit breakers from heat and damages caused as a result of arc formation.

[0004] Alternating current (AC) switching systems utilize the naturally occurring zero-crossings of the alternating current flowing through the switching system for extinguishing the arc. Direct current (DC) switching systems cannot utilize natural zero-crossings since there are none - DC current does not pass through zero like AC. Thus, for DC switching systems, circuit breaker has to reduce the current down to zero by itself (forcing the current passage to zero). When connecting such a circuit breaker to a DC circuit, unlike an AC circuit in which the current zero point is set at regular intervals, the arc generated when the DC circuit is interrupted continues. Therefore, the conventional circuit breakers connected to the DC circuit increases the arc voltage by increasing the gap between the fixed and movable contacts at the time of opening, and the voltage between the contacts is higher than the power supply voltage of the DC circuit. In this way, the current drops down and is interrupted.

[0005] As known from the art, arc chutes are made of a highly durable, arc-proof material, in which the arc plates (splitter plates) have been integrated. Arc chute contains a set of stacks of substantially parallel metal plates insulated from each other by an air gap between each of them. The splitter plates split the arc into partial arcs and increase the arc voltage by multiplying the anode and cathode voltage drop. Because of their high heat capacity, the plates and arc chute walls absorb a large amount of the arc's energy. Thus, arc chute allows to divide, cool down and extinguish the electric arc. Specifically, the metal splitter plates, normally made of ferromagnetic material, allow to elongate the arc in arc chute.

[0006] The arc is attracted by magnetic and fluid-dynamic forces towards and between the splitter plates. The structure of the arc chute lengthens the arc further and splits it into small segments . This increases the arc length, cools it down and finally arc is extinguished.

[0007] The simplest known arc chutes do not comprise any insulating plates (especially these used for circuit breakers having lower short-circuit capacities). Other known arc chutes comprise insulation plates or other insulation elements placed above the splitter plates. Generally, insulation plates or other insulating elements allow to limit the speed of the arc spreading and allow to keep the arc inside the arc chute as long as possible, until it is completely extinguished. Additionally, insulation plates cool down the arc by increasing its resistance. They also help to increase the overall length of the arc.

[0008] There are many prior art documents which relate to several different problems in the field of arc breakers.

[0009] The most widely used electrical circuit breakers for electrical connections, which are low-voltage circuit breakers, are Miniature circuit breakers (MCBs), Residual current circuit breakers (RCCBs) and Molded Case Circuit Breaker (MCCBs). In case of such domestic DC breakers, the splitter plates are sometimes equipped with legs.

[0010] Legs in various forms and shapes are intended to direct the arc so that it extends in the center of the arc chute and not against its walls. In the state of the art there are several solutions of splitter plates with legs, which sometimes may be covered, for example to prevent undesirable electrical arcing.

[0011] For example, EP1098331A2 discloses an arc chute having splitter plate with legs covered by end caps. The end caps are formed from electrically insulating material which, during the presence of the electrical arc, ablates and outgasses material as a result of being exposed to the high heat from the electrical arc. The gasses produced assist in cooling the arc and increase the resistance of the conducting plasma generated within the arc chamber which therefore, increases the arc voltage and accelerates the extinguishment of the electrical arc. The end caps also prevent undesirable electrical arcing between the movable contact arm and the intermediate arc plates and other parts of the operating mechanism of the circuit breaker.

[0012] Document US20080192400A1, filed by the present Applicant, discloses a protection device for protecting an electrical installation against overvoltages, overloads or short-circuits, comprising at least two main electrodes between which an electric arc is able to form, and an electric arc breaker device extending, considering the direction of propagation of the arc, between an upstream end and a downstream end and having, at the upstream end, an entry area for the arc, at which the electric arc penetrates inside the breaker device. The breaker device includes, positioned at the upstream end, insulating means against the return of the electric arc, structurally designed to allow the arc to enter the breaker device while forming an obstacle against the exiting of the electric arc, to prevent the electric arc, once located inside the breaker device, from escaping from the breaker device. The insulating means are formed by one or several flexible strips in an insulating material, laid out in order to form a partial insulating barrier between the electrodes and the upstream end.

[0013] Document DE102008021138A1, filed by the present Applicant, discloses an electric arc extinguishing plate arrangement for use in e.g. circuit breaker, having electric arc extinguishing plates held by rib at distance to each other, where rib is projected from box broad side to box interior. In the embodiment of the arc chute, the broad side wall of the box to over the inlet edge the arc quenching plates is extended and the leading edge through a molded bar, which are thus for the arc quenching plates forms an undercut, additionally covering. There remains thus the V-shaped inlet area at the arc quenching plates uncovered.

[0014] There are several problems with known arc chutes comprising parallel splitter plates with legs. At certain short circuit conditions arc may be reignited below splitter plates and stacked there, and thus cannot be extinguished correctly. Burning arc causes degradation of splitter plates and arc chutes walls. In most cases legs are not separated from the arc, and the risk of re-ignition and damage is very high. Thus, to minimize this risk, splitter plates legs are being equipped with insulation. In known solutions, the legs are usually covered with a simple insulating plate or covered with some insulating material (for example by painting, fluidization or pouring in a mold).

[0015] Nevertheless, known solutions still have many drawbacks - insulation is not sufficient and does not protect completely from re-ignition and damage, as well as manufacturing costs are high and production is complicated. Moreover, in known solutions the legs are not completely surrounded by insulating material, or the insulating material disturbs the movement of the arc towards the splitter plates. Covering the legs from the outside is not sufficient because when the device is turned off, the arc is formed on the lower edges of the legs. The reignited arc increases the total arc extinguishing time, which increases erosion of both the legs and adjacent insulating materials and causes unnecessary overheating of the arc chute and other circuit breaker components. In other words, known solutions thus still do not allow to sufficiently prevent arc reignition below the splitter plates and between the legs of splitter plates. Legs of splitter plates and bottom area of side walls are not protected against the direct contact with burning arc, and the degradation of material of splitter plates and side wall during switching operation is not prevented. Also, there still exists the risk of run-back of the arc to bottom area of arc chute and possible of arc reignition between breaker arc runners.Summary

[0016] The object of the invention is to overcome said drawbacks of the prior art and to prevent arc reignition below the splitter plates and between the legs of splitter plates, and protect legs of splitter plates and bottom area of side walls against the direct contact with burning arc.

[0017] This has been achieved by providing an arc chute for a direct current switching device, comprising: at least one stack formed by a plurality of substantially parallel metallic splitter plates; at least one stack formed by a plurality of substantially parallel insulation plates, the edges of the insulation plates facing the edges of the splitter plates; a housing made of electrically insulating material surrounding the at least one stack of splitter plates and the at least one stack of insulation plates; wherein each of the splitter plates includes a base part and two legs extending from two opposite sides of the base part, whereby the legs on each side of the base part also form a stack; and whereby each stack of the legs is covered by insulation barrier. The invention is characterized in that the insulation barrier comprises partition walls, the partition walls being made of electrically insulative and heat resistant material, whereby partition walls are formed as insulation sheets arranged in a spaced relation in a stack, meshing with each stack of the legs and separating the legs from each other.

[0018] Preferably, the insulation barrier is formed by an insulation cover and the bottom part of the housing, adjacent to the legs, whereby the partition walls form one piece with the insulation cover and protrude from each insulation cover.

[0019] Alternatively, the insulation barrier is formed by the insulation cover and the bottom part of the housing, adjacent to the legs, whereby the partition walls are formed as insulation sheets protruding from each of the bottom parts of the housing, adjacent to the legs.

[0020] Alternatively, the insulation barrier is formed by the insulation cover having partition walls protruding from it and having a vertical wall, whereby the vertical wall is placed between the legs and the housing.

[0021] Alternatively, the insulation barrier is formed by the housing adjacent to the legs, whereby the housing is shaped to have a part forming the insulation cover, and whereby the partition walls protrude from each of the bottom parts of the housing, adjacent to the legs.

[0022] Preferably, the legs are covered from their bottom side by a bottom part of the insulation cover.

[0023] Alternatively, the legs are covered from their bottom side by a bottom part of the housing.

[0024] Preferably, the thickness of the insulation cover is at least 2,6 mm.

[0025] Preferably, the thickness of the vertical wall is between 2 mm to 10 mm.

[0026] Preferably, the insulation cover is connected with the housing by pins protruding from the housing inserted into respective openings in the insulation cover or by pins protruding from the insulation cover inserted into respective openings in the housing.

[0027] Alternatively, the insulation barrier is connected with the housing by pins protruding from the housing inserted into respective openings in the insulation barrier or by pins protruding from the insulation barrier inserted into respective openings in the housing.

[0028] Preferably, the partition walls are made of material resistant to temperatures of at least 150°C.

[0029] Preferably, the insulation barrier with partition walls is made of electrically insulative and heat resistant resin, preferably unsaturated polyester.

[0030] Alternatively, the insulation barrier with partition walls is made of an inorganic insulating material, preferably ceramics.

[0031] Preferably, the thickness of partition walls is from 0,2 mm to 0,6 mm smaller than the distance between subsequent splitter plates.Brief Description of the Drawings

[0032] The present invention will be presented in a more detailed way with reference to the accompanying drawing, in which: Fig. 1 shows the cross-section of the arc chute parallel to the plane of the splitter plates, according to the first embodiment; Fig. 2 shows the external view of the arc chute from the front, parallelly to the plane of the splitter plates, according to the first embodiment; Fig. 3 shows partial cross-section of the DC circuit breaker and arc chute; Fig. 4 shows a cross-section of the arc chute parallel to the plane of the splitter plates, in a more detailed view showing the splitter plates inserted between partition walls, according to the first embodiment; Fig. 5 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates, according to the first embodiment; Fig. 6 shows the cross-section of the arc chute parallel to the plane of the splitter plates, in a view showing the splitter plates inserted between partition walls, according to the second embodiment; Fig. 7 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates, according to the second embodiment; Fig. 8 shows the cross-section of the arc chute parallel to the plane of the splitter plates, in a view showing the splitter plates inserted between partition walls, according to the third embodiment; Fig. 9 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates, according to the third embodiment; Fig. 10 shows the cross-section of the arc chute parallel to the plane of the splitter plates, in a view showing the splitter plates inserted between partition walls, according to the fourth embodiment; Fig. 11 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates, according to the fourth embodiment. Detailed Description

[0033] Preferred embodiments of the invention are described in detail below. The examples serve only as an illustration and do not limit the scope of the present invention.

[0034] The invention, in general, concerns an arc chute for direct current switching device, which may be provided in various types of electric equipment such as circuit breakers, contactors etc. The device may more particularly be employed in a direct current (DC) circuit breaker, specifically for low and medium voltage application. The arc chute according to the invention is designed to be used in industrial applications, for example in DC circuits on railway, tramways or metro power distribution systems, copper processing plants, mining or steel mills.

[0035] DC circuit breaker normally comprises a switch with a first switch contact and a second switch contact, wherein the second switch contact is movable between a first position, in which the first switch contact is touching the second switch contact, and a second position, in which the first and second switch contacts are separated from each other. Further, DC circuit breaker comprises an arc chute having a stack of a plurality of substantially parallel metal plates separated from each other by a certain distance, as it was described above. The arc chute typically also comprises a pair of arc horns for guiding the arc in the arc chute towards the splitter plates 1. Arc horns are connected with arc runners, the arc runners being elements of the circuit breaker which guide the arc towards the arc chute. In other words, arc horns placed in the arc chute are the end elements of the arc runners.

[0036] Arc chute according to the invention, in all possible embodiments, shown in the attached Figures, comprises at least one stack formed by a plurality of substantially parallel splitter plates 1, separated by air gaps. Air gaps between splitter plates 1 may be equal or may be of different width. Splitter plates 1 are arranged in spaced relation in a stack, and their arrangement is obtained (dependent on the particular embodiment) for example by positioning them, dependent on the embodiment, by housing 2 and / or partition walls 4 and / or insulation barrier 5. In some embodiments, splitter plates 1 may be mounted in some support structure or in grooves located on the internal side of housing 2. However, supporting and positioning of the splitter plates 1 may be achieved differently.

[0037] In all presented embodiments, the arc chute has insulation plates 3 placed above the splitter plates 1. Insulation plates 3 also form a stack like splitter plates 1. The edges of the insulation plates 3 face the edges of the splitter plates 1. The number of insulation plates 3 may be equal to the number of splitter plates 1. In another embodiment, which is shown in the Figures (this is visible especially in Fig. 3), for example due to the structure of the arc chute (due to presence of mounting points of the arc chute on the side walls of the housing 2), the number of insulation plates 3 may be smaller than the number of the splitter plates 1.

[0038] In all presented embodiments, the splitter plates 1 (on their bottom side, i.e. in their lower part) have legs 12, formed by longitudinal protrusions of each splitter plate 1. Each splitter plate 1 has thus a substantially continuous part - base part 11 - and a leg part - legs 12, so that each splitter plate 1 is longer on its both ends - thus, the gap is formed between its lower ends (legs 12), and each splitter plate 1 has the form of inverted V-shaped opening. Thus, each of the splitter plates 1 includes a base part 11 and two legs 12, which are extending from two opposite sides of the base part 11. Legs 12 of each splitter plate 1 form a stack, same as the base parts 11 of the splitter plates 1. The legs 12 are substantially parallel to each other. Typically, the width of the legs 12 is from 5 mm in their narrowest place to 12 mm in their widest place - preferably 8 mm. The thickness of the legs 12 (as well as the base part 11) is from 2 mm to 3 mm, preferably 2,5 mm. The shape of the arc splitter plate 1 is such that in the presence of the magnetic field the arc is drawn towards the apices of the V-shaped openings in each of the arc splitter plates 1. At the top of the V-shaped openings the presence of the magnetic field is mitigated and the arc is broken down into a plurality of arcs known as series arcs.

[0039] The arc chute is also equipped with a housing 2, surrounding the splitter plates 1 and insulation plates 3. The housing 2 is made of electrically insulative and heat resistant material. The housing 2 is thus made, for example, of electrically insulative and heat resistant resin, such as UP (unsaturated polyester), or of inorganic insulating material such as ceramics.

[0040] The essence of the invention is providing partition walls 4 formed as a stack of insulating sheets, which mesh with the legs 12 and separate them from each other, such as there is formed a stack of alternatingly arranged legs 12 and partition walls 4.

[0041] First embodiment of the invention is shown in Figs. 1, 2, 4 and 5. The arc chute according to the first embodiment of the invention is schematically presented in Fig. 1, showing a cross-section of the arc chute parallel to the plane of the splitter plates 1. Fig. 2 shows the external view of the arc chute from the front, parallelly to the plane of the splitter plates 1, showing that the legs 12 are covered also from their front (and rear) side. Fig. 4 shows a cross-section of the arc chute parallel to the plane of the splitter plates 1, in a more detailed view showing the splitter plates 1 inserted between partition walls 4. Fig. 5 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates 1.

[0042] Fig. 3 shows partial cross-section of the DC circuit breaker and arc chute, whereby the cross-section is perpendicular to the plane of the splitter plates 1 - this Fig. 3 shows the arrangement of splitter plates 1 and insulation plates 3, which may be arranged such that the heights of the splitter plates 1 are alternating - in each subsequent pair, splitter plate 1 is, respectively, longer or shorter, whereby the corresponding insulation plate 3 is, respectively, shorter or longer.

[0043] In this first embodiment, the insulation barrier 5 covers each of the legs 12, such as the legs 12 are insulated from each other by the partition walls 4 of the insulation barrier 5. The insulation barrier 5 is formed by a lower part of the housing 2, adjacent to the legs 12, and by the insulation cover 6. The lower part of the housing 2 covers the legs 12 from their external side, whereby the insulation cover 6 covers the legs 12 from their internal side (from the side of the V-shaped openings - from the side of the arc) and also from the lateral side of the most external splitter plates 1, as well as from their bottom side. The insulation cover 6 is equipped with partition walls 4, separating the legs 12 from each other. This can be best seen in Fig. 4 and Fig. 5 - partition walls 4 connected with insulation cover 6 resemble a shape of the comb. Insulation cover 6 is connected with the housing 2, in order to be stably mounted, for example by pins protruding from the housing 2 (shown in Fig. 5), inserted into respective openings in the bottom of the insulation cover 6 (in the part of the insulation cover which does not have partition walls 4 protruding from it). The pins may also protrude from the insulation cover 6 and be inserted into respective openings in the housing 2.

[0044] To be precise, each stack of the legs 12 (on the left and on the right side of the base part 11) is covered by its own insulation barrier 5. One insulation barrier 5 may, in another embodiment, cover several stacks of legs 12 (this embodiment is not shown in the Figures). Each stack of the legs 12 is thus equipped with the partition walls 4 arranged parallelly to the legs 12 and formed as a part of the insulation cover 6. In other words, partition walls 4 and insulation cover 6 form one-piece element, meshing with legs 12 and covering them from the side of the V-shaped opening, whereby from the other side the splitter plates 1 are covered by the bottom part of the housing 2. Partition walls 4 are formed as a stack of insulating sheets, which mesh with the legs 12 (they fill in the gaps between the legs 12) and separate the legs 12 from each other, such as there is formed a stack of alternatingly arranged legs 12 and partition walls 4. As mentioned above, the insulation cover 6 also may cover the legs 12 from their bottom side. The thickness of the insulation cover 6, preferably, should not be smaller than 2,5 mm. This thickness is measured between the edge of the leg 12 and the surface (from the internal side of the arc chute) od the insulation cover 6 in its thinnest part. The thickness of partition walls 4 depends on the distance between subsequent splitter plates 1 and usually is about 0,2 to 0,6 mm smaller than this distance, in order to create a space for installation purposes.

[0045] In one variation of the first embodiment, the bottom side of the stack of legs 12 may be covered by a piece of the housing 2 instead of a piece of the insulation cover 6 (not shown in the Figures).

[0046] Second embodiment of the invention is shown in Figs. 6 and 7. The arc chute according to the second embodiment of the invention is schematically presented in Fig. 6, showing a cross-section of the arc chute parallel to the plane of the splitter plates 1, where the splitter plates 1 are inserted between partition walls 4. Fig. 7 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates 1.

[0047] In this second embodiment, the insulation barrier 5 covers each of the legs 12, such as the legs 12 are insulated from each other by the partition walls 4. The insulation barrier 5 is formed by a lower part of the housing 2, adjacent to the legs 12, and by the insulation cover 6. The lower part of the housing 2 covers the legs 12 from their external side, whereby the insulation cover 6 covers the legs 12 from their internal side (from the side of the V-shaped openings - from the side of the arc) and also from the lateral side of the most external splitter plates 1. Most external splitter plates 1 may be covered by a part of housing 2 or by a part of insulation cover 6. The housing 2 is equipped with partition walls 4, separating the legs 12 from each other - partition walls 4 are connected with housing 2 and resemble a shape of the comb. The bottom side of the legs 12 is covered by a part of the housing 2 below the partition walls 4. The bottom side of the legs 12 may also be covered by a bottom part of the insulation cover 6 (this is not shown in the Figures).

[0048] Each stack of the legs 12 is covered by its own insulation barrier 5. One insulation barrier 5 may, in another embodiment, cover several stacks of legs 12 (this embodiment is not shown in the Figures). Each stack of the legs 12 is thus equipped with the partition walls 4 formed as a part of the housing 2 - in other words, partition walls 4 and housing 2 form one-piece element, meshing with the legs 12 and also covering them from the bottom (from their lowest part), whereby from the other side the legs 12 are covered by the insulation cover 6. Thus, in the second embodiment the insulation cover 6 does not have partition walls 4 - instead, it is formed as a smooth element covering the legs 12 from the side from the arc. Partition walls 4 are formed as a stack of insulating sheets, which mesh with the legs 12 (they fill in the gaps between the legs 12) and separate them from each other, such as there is formed a stack of alternatingly arranged legs 12 and partition walls 4. The insulation cover 6 may be connected with the housing 2 for example by pins protruding from the housing 2 inserted into respective openings in the insulation cover 6, or by pins protruding from the insulation cover 6 inserted into respective openings in the housing 2. The openings in the housing 2 for receiving pins are visible in Fig. 7. The thickness of the insulation cover 6, preferably, should not be smaller than 2,5 mm, similarly as in the first embodiment. The thickness of partition walls 4 depends on the distance between subsequent splitter plates 1 and usually is about 0,2 to 0,6 mm smaller than this distance.

[0049] In one variation of the second embodiment, the bottom side of the stack of legs 12 may be covered by a piece of the insulation cover 6 instead of a piece of the housing 2 (not shown in the Figures).

[0050] Third embodiment of the invention is shown in Figs. 8 and 9. The arc chute according to the third embodiment of the invention is thus schematically presented in Fig. 8, showing a cross-section of the arc chute parallel to the plane of the splitter plates 1, where the splitter plates 1 are inserted between partition walls 4. Fig. 9 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates 1.

[0051] In this third embodiment, the insulation barrier 5 also covers each of the legs 12, such as the legs 12 are insulated from each other by the partition walls 4. The insulation barrier 5 is in this case formed by the appropriately shaped insulation cover 6 having additionally a vertical wall 7. The insulation cover 6 covers the legs 12 from their internal side (from the side of the V-shaped openings - from the side of the arc), from the lateral side of the most external splitter plates 1, from their bottom, as well as from their side which was in the previous embodiments covered by the housing 2 - i.e. from the side of the housing 2. The insulation cover 6 is equipped with partition walls 4, separating the legs 12 from each other - partition walls 4 are connected with insulation cover 6 and resemble a shape of a comb. Further, insulation cover 6 has the vertical wall 7, which is placed between the legs 12 and the housing 2. Thus, the legs 12 are covered from each side solely by the insulation cover 6 having the vertical wall 7, partition walls 4 and obviously a part covering the legs 12 from the side of the V-shaped opening and from their bottom side. The insulation cover 6 can be placed on the legs 12 by inserting it (sliding) from the bottom side of the legs 12. Insulation barrier 5 is preferably connected with the housing 2, in order to be stably mounted, for example by pins protruding from the housing 2 (shown in Fig. 9), inserted into respective openings in the insulation barrier 5 (for example in its vertical wall 7), or by pins protruding from the insulation barrier 5 inserted into respective openings in the housing 2.

[0052] Each stack of the legs 12 is covered by its own insulation barrier 5. One insulation barrier 5 may, in another embodiment, cover several stacks of legs 12 (this embodiment is not shown in the Figures). Each stack of the legs 12 is thus equipped with the partition walls 4 formed as a part of the insulation cover 6 - in other words, the insulation cover 6 with partition walls 4 and vertical wall 7 form one-piece element - insulation barrier 5, meshing with the legs 12 and also covering them from their bottom (from their lowest part) and from their lateral sides. Partition walls 4 are formed as a stack of insulating sheets, which mesh with the legs 12 (they fill in the gaps between the legs 12) and separate them from each other, such as there is formed a stack of alternatingly arranged legs 12 and partition walls 4. The thickness of the insulation cover 6, preferably, should not be smaller than 2,5 mm, similarly as in previous embodiments. The thickness of partition walls 4, as in previous embodiments, depends on the distance between subsequent splitter plates 1 and usually is from 0,2 to 0,6 mm smaller than this distance. The thickness of the vertical wall 7 depends on the material used and production method of this element; nevertheless, its thickness may be comprised between 2 to 10 mm.

[0053] In the fourth embodiment of the invention, shown in Figures 10 and 11, the insulation barrier 5 also covers each of the legs 12, such as the legs 12 are insulated from each other by the partition walls 4. The arc chute according to the fourth embodiment of the invention is thus schematically presented in Fig. 10, showing a cross-section of the arc chute parallel to the plane of the splitter plates 1, where the splitter plates 1 are inserted between partition walls 4. Fig. 11 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates 1.The insulation barrier 5 is in this case formed solely by the appropriately shaped housing 2. The housing 2 thus has a part covering the legs 12 from their internal side (from the side of the V-shaped openings - from the side of the arc), a part covering the stack of legs 12 from the lateral side of the most external splitter plates 1, as well as a part covering the stack of legs 12 from its bottom side. The housing 2 is equipped with partition walls 4, separating the legs 12 from each other - partition walls 4 are connected with housing 2 and resemble a shape of a comb. Thus, the legs 12 are covered from each side solely by the housing 2 having partition walls 4. In other words, housing 2 is shaped to have a part forming the insulation cover 6 as in previous embodiments, covering the stack of legs 12 from the side of the V-shaped opening, and to have a part covering the stack of legs 12 from their bottom side. In yet another words, the fourth embodiment resembles the second embodiment shown in Figs. 6 and 7, in which the housing 2 having partition walls 4 forms one piece with the insulation cover 6.

[0054] Each stack of the legs 12 is covered by its own insulation barrier 5. Each stack of the legs 12 is thus equipped with the partition walls 4 formed as a part of the housing 2 - in other words, the housing 2 with partition walls 4 and parts covering the remaining sides of the stack of legs 12 (bottom and sides as mentioned above) form one-piece element - insulation barrier 5, meshing with the legs 12 and also covering them from their bottom (from their lowest part) and from their lateral sides. Partition walls 4 are formed as a stack of insulating sheets, which mesh with the legs 12 (they fill in the gaps between the legs 12) and separate them from each other, such as there is formed a stack of alternatingly arranged legs 12 and partition walls 4. The thickness of the part covering the stack of legs 12 from the side of the V-shaped openings, forming the insulation cover 6 as in previous embodiments, should not be smaller than 2,5 mm, similarly as in previous embodiments. The thickness of partition walls 4, as in previous embodiments, depends on the distance between subsequent splitter plates 1 and usually is from 0,2 to 0,6 mm smaller than this distance.

[0055] In this fourth embodiment, the arc chute may be formed easily by means of 3D printing, since in this case the arc chute (excluding splitter plates 1 and insulation plates 3) is manufactured as one-piece element. In all of the embodiments, the walls of the housing 2 are manufactured as one-piece element.

[0056] Splitter plates legs 12, in all of the presented embodiments, are made of metal, preferably steel (since they form a part of the splitter plates 1, they are made of the same material as splitter plates 1). The partition walls 4 (as well as other parts of insulation barrier 5) are in all presented embodiments preferably made of the same material as the housing 2. Preferably, this material is resistant to temperatures of at least 150°C. More preferably, the material is resistant to temperatures of between 150 to 210°C - in the state of the art, standard insulating materials in this type of structures have a resistance to continuous temperatures between 150-210°C. The material may be for example an electrically insulative and heat resistant resin (for example unsaturated polyester).

[0057] Such a resistancy is necessary due to the necessity to withstand the temperature to which the splitter plates 1 are heated up during arc extinguishing process. All insulating materials in the arc chute are briefly exposed (for less than a second - usually for several miliseconds) to a very high electric arc temperature (up to approx. 5700°C). After that, they are exposed to the temperature to which the splitter plates 1 heated up during arc extinguishing process - this temperature can reach up to 500°C.

[0058] The partition walls 4 (and housing 2) may also be made of material having higher temperature resistancy (even above 500°C), such as inorganic insulating materials - various types of ceramics or glass-cement materials. However, due to high costs, poorer mechanical properties and water absorption, these materials are used only in justified cases.

[0059] In all embodiments, partition walls 4 are made of heat-resistant insulation material, for example from a material made of glass and polyester, or made of ceramics, or made of glass and concrete (as discussed above). Partition walls 4 have generally a shape of a comb (they are formed as a stack of insulation sheets) - this arrangement is crucial since, as said before, if the legs 12 would be covered only from the outside, the arc would reignite and would be formed on the lower edges of the legs 12, leading to erosion of the legs 12 and adjacent insulating materials, overheating of the arc chute and of other circuit breaker components. Providing partition walls 4 allows to fill the air gaps between the legs 12 of the splitter plates 1, and thus separate them from each other. Thanks to that, the reigniting arc no longer forms on the lower edges of the legs 12.

[0060] To sum up, there is provided an arc chute having insulation barrier 5, formed either by a part of the housing 2 and the insulation cover 6 having partition walls 4, or by a part of the housing 2 having partition walls 4 and by a plain insulation cover 6, or by the insulation cover 6 having partition walls 4 and the vertical wall 7 perpendicular to the legs 12, the vertical wall 7 being placed between the housing 2 and the legs 12, or formed solely by the housing 2. The partition walls 4 are formed as a stack of substantially parallel insulation sheets separating the legs 12 from each other. This allows to protect metal parts (the splitter plates 1 legs 12 and also bottom area of side walls) from direct contact with electric arc, and therefore degradation of splitter plates 1 and arc chutes walls due to burning arc during switching operation is avoided. In other words, the presence of the partition walls 4 between the legs 12 prevents the arc from burning between these legs 12 (arc reignition below the splitter plates 1 and between the legs 12 is prevented). Partition walls 4 direct the arc towards the center of the arc chute and reduce risk of run-back of arc to the bottom area of arc chute and possibility of arc reignition between breaker arc runners. Thus, the arc is burning only above the legs 12, in the region of the base parts 11 (between base parts 11 of the splitter plates 1), comprising greater amount of material. The legs 12 are completely surrounded by insulating material, which additionally forms a uniform, smooth surface on the side of the arc that does not disturb (does not cause turbulence) the movement of the arc towards the splitter plates 1.

[0061] The arc chute disclosed herein is intended for being arranged in a switching device such as circuit breaker, comprising a stationary contact and a moveable contact, connectable / disconnectable to said stationary contact, forming an electrical switch.List of reference numerals:

[0062] 1 - splitter plate 11 - base part 12 - legs 2 - housing 3 - insulation plate 4 - partition walls 5 - insulation barrier 6 - insulation cover 7 - vertical wall

Examples

first embodiment

[0041]First embodiment of the invention is shown in Figs. 1, 2, 4 and 5. The arc chute according to the invention is schematically presented in Fig. 1, showing a cross-section of the arc chute parallel to the plane of the splitter plates 1. Fig. 2 shows the external view of the arc chute from the front, parallelly to the plane of the splitter plates 1, showing that the legs 12 are covered also from their front (and rear) side. Fig. 4 shows a cross-section of the arc chute parallel to the plane of the splitter plates 1, in a more detailed view showing the splitter plates 1 inserted between partition walls 4. Fig. 5 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates 1.

[0042]Fig. 3 shows partial cross-section of the DC circuit breaker and arc chute, whereby the cross-section is perpendicular to the plane of the splitter plates 1 - this Fig. 3 shows the arrangement of splitter plates 1 and insulation plates 3, which may be arranged su...

second embodiment

[0046]Second embodiment of the invention is shown in Figs. 6 and 7. The arc chute according to the invention is schematically presented in Fig. 6, showing a cross-section of the arc chute parallel to the plane of the splitter plates 1, where the splitter plates 1 are inserted between partition walls 4. Fig. 7 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates 1.

[0047]In this second embodiment, the insulation barrier 5 covers each of the legs 12, such as the legs 12 are insulated from each other by the partition walls 4. The insulation barrier 5 is formed by a lower part of the housing 2, adjacent to the legs 12, and by the insulation cover 6. The lower part of the housing 2 covers the legs 12 from their external side, whereby the insulation cover 6 covers the legs 12 from their internal side (from the side of the V-shaped openings - from the side of the arc) and also from the lateral side of the most external splitter plates 1. Mo...

third embodiment

[0050]Third embodiment of the invention is shown in Figs. 8 and 9. The arc chute according to the invention is thus schematically presented in Fig. 8, showing a cross-section of the arc chute parallel to the plane of the splitter plates 1, where the splitter plates 1 are inserted between partition walls 4. Fig. 9 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates 1.

[0051]In this third embodiment, the insulation barrier 5 also covers each of the legs 12, such as the legs 12 are insulated from each other by the partition walls 4. The insulation barrier 5 is in this case formed by the appropriately shaped insulation cover 6 having additionally a vertical wall 7. The insulation cover 6 covers the legs 12 from their internal side (from the side of the V-shaped openings - from the side of the arc), from the lateral side of the most external splitter plates 1, from their bottom, as well as from their side which was in the previous embodi...

Technical Field

[0001] The invention belongs to the field of electrical switching devices with arc chutes for arc quenching. More particularly, the invention relates to an arc chute for direct current (DC) switching device, especially circuit breaker.Background

[0002] Circuit breakers are devices used to interrupt the electric current flow especially in the case of abnormal operating conditions, for example current overload. When a fault occurs, a circuit breaker interrupts the current by moving the contacts apart. Upon separation of the contacts, an electric arc is generated between them. An electric arc is the discharge of electric current through gas or air. Electric arc or arc discharge generates a large amount of heat, which can cause damage to the contacts by melting them, as well as it can cause damage to other components of the circuit breaker. Moreover, as the arc temperature is very high, when a surrounding structure is melted and broken, a metal powder or soot of carbon is produced, which adheres to a main contact. Thus, a contact resistance at an adhering portion is increased, and there is a possibility that energization fault occurs. According to that, frequent condition checks of main contact are required, and the adhering portion needs to be frequently removed.

[0003] Therefore, to minimize the damage, the arc needs to be safely and rapidly extinguished, and the current needs to be interrupted as soon as possible. For this purpose, arc chutes are used which are placed near the circuit breaker contacts. Thus, arc chutes are one of the key components of circuit breakers - they protect the circuit breakers from heat and damages caused as a result of arc formation.

[0004] Alternating current (AC) switching systems utilize the naturally occurring zero-crossings of the alternating current flowing through the switching system for extinguishing the arc. Direct current (DC) switching systems cannot utilize natural zero-crossings since there are none - DC current does not pass through zero like AC. Thus, for DC switching systems, circuit breaker has to reduce the current down to zero by itself (forcing the current passage to zero). When connecting such a circuit breaker to a DC circuit, unlike an AC circuit in which the current zero point is set at regular intervals, the arc generated when the DC circuit is interrupted continues. Therefore, the conventional circuit breakers connected to the DC circuit increases the arc voltage by increasing the gap between the fixed and movable contacts at the time of opening, and the voltage between the contacts is higher than the power supply voltage of the DC circuit. In this way, the current drops down and is interrupted.

[0005] As known from the art, arc chutes are made of a highly durable, arc-proof material, in which the arc plates (splitter plates) have been integrated. Arc chute contains a set of stacks of substantially parallel metal plates insulated from each other by an air gap between each of them. The splitter plates split the arc into partial arcs and increase the arc voltage by multiplying the anode and cathode voltage drop. Because of their high heat capacity, the plates and arc chute walls absorb a large amount of the arc's energy. Thus, arc chute allows to divide, cool down and extinguish the electric arc. Specifically, the metal splitter plates, normally made of ferromagnetic material, allow to elongate the arc in arc chute.

[0006] The arc is attracted by magnetic and fluid-dynamic forces towards and between the splitter plates. The structure of the arc chute lengthens the arc further and splits it into small segments . This increases the arc length, cools it down and finally arc is extinguished.

[0007] The simplest known arc chutes do not comprise any insulating plates (especially these used for circuit breakers having lower short-circuit capacities). Other known arc chutes comprise insulation plates or other insulation elements placed above the splitter plates. Generally, insulation plates or other insulating elements allow to limit the speed of the arc spreading and allow to keep the arc inside the arc chute as long as possible, until it is completely extinguished. Additionally, insulation plates cool down the arc by increasing its resistance. They also help to increase the overall length of the arc.

[0008] There are many prior art documents which relate to several different problems in the field of arc breakers.

[0009] The most widely used electrical circuit breakers for electrical connections, which are low-voltage circuit breakers, are Miniature circuit breakers (MCBs), Residual current circuit breakers (RCCBs) and Molded Case Circuit Breaker (MCCBs). In case of such domestic DC breakers, the splitter plates are sometimes equipped with legs.

[0010] Legs in various forms and shapes are intended to direct the arc so that it extends in the center of the arc chute and not against its walls. In the state of the art there are several solutions of splitter plates with legs, which sometimes may be covered, for example to prevent undesirable electrical arcing.

[0011] For example, EP1098331A2 discloses an arc chute having splitter plate with legs covered by end caps. The end caps are formed from electrically insulating material which, during the presence of the electrical arc, ablates and outgasses material as a result of being exposed to the high heat from the electrical arc. The gasses produced assist in cooling the arc and increase the resistance of the conducting plasma generated within the arc chamber which therefore, increases the arc voltage and accelerates the extinguishment of the electrical arc. The end caps also prevent undesirable electrical arcing between the movable contact arm and the intermediate arc plates and other parts of the operating mechanism of the circuit breaker.

[0012] Document US20080192400A1, filed by the present Applicant, discloses a protection device for protecting an electrical installation against overvoltages, overloads or short-circuits, comprising at least two main electrodes between which an electric arc is able to form, and an electric arc breaker device extending, considering the direction of propagation of the arc, between an upstream end and a downstream end and having, at the upstream end, an entry area for the arc, at which the electric arc penetrates inside the breaker device. The breaker device includes, positioned at the upstream end, insulating means against the return of the electric arc, structurally designed to allow the arc to enter the breaker device while forming an obstacle against the exiting of the electric arc, to prevent the electric arc, once located inside the breaker device, from escaping from the breaker device. The insulating means are formed by one or several flexible strips in an insulating material, laid out in order to form a partial insulating barrier between the electrodes and the upstream end.

[0013] Document DE102008021138A1, filed by the present Applicant, discloses an electric arc extinguishing plate arrangement for use in e.g. circuit breaker, having electric arc extinguishing plates held by rib at distance to each other, where rib is projected from box broad side to box interior. In the embodiment of the arc chute, the broad side wall of the box to over the inlet edge the arc quenching plates is extended and the leading edge through a molded bar, which are thus for the arc quenching plates forms an undercut, additionally covering. There remains thus the V-shaped inlet area at the arc quenching plates uncovered.

[0014] There are several problems with known arc chutes comprising parallel splitter plates with legs. At certain short circuit conditions arc may be reignited below splitter plates and stacked there, and thus cannot be extinguished correctly. Burning arc causes degradation of splitter plates and arc chutes walls. In most cases legs are not separated from the arc, and the risk of re-ignition and damage is very high. Thus, to minimize this risk, splitter plates legs are being equipped with insulation. In known solutions, the legs are usually covered with a simple insulating plate or covered with some insulating material (for example by painting, fluidization or pouring in a mold).

[0015] Nevertheless, known solutions still have many drawbacks - insulation is not sufficient and does not protect completely from re-ignition and damage, as well as manufacturing costs are high and production is complicated. Moreover, in known solutions the legs are not completely surrounded by insulating material, or the insulating material disturbs the movement of the arc towards the splitter plates. Covering the legs from the outside is not sufficient because when the device is turned off, the arc is formed on the lower edges of the legs. The reignited arc increases the total arc extinguishing time, which increases erosion of both the legs and adjacent insulating materials and causes unnecessary overheating of the arc chute and other circuit breaker components. In other words, known solutions thus still do not allow to sufficiently prevent arc reignition below the splitter plates and between the legs of splitter plates. Legs of splitter plates and bottom area of side walls are not protected against the direct contact with burning arc, and the degradation of material of splitter plates and side wall during switching operation is not prevented. Also, there still exists the risk of run-back of the arc to bottom area of arc chute and possible of arc reignition between breaker arc runners.Summary

[0016] The object of the invention is to overcome said drawbacks of the prior art and to prevent arc reignition below the splitter plates and between the legs of splitter plates, and protect legs of splitter plates and bottom area of side walls against the direct contact with burning arc.

[0017] This has been achieved by providing an arc chute for a direct current switching device, comprising: at least one stack formed by a plurality of substantially parallel metallic splitter plates; at least one stack formed by a plurality of substantially parallel insulation plates, the edges of the insulation plates facing the edges of the splitter plates; a housing made of electrically insulating material surrounding the at least one stack of splitter plates and the at least one stack of insulation plates; wherein each of the splitter plates includes a base part and two legs extending from two opposite sides of the base part, whereby the legs on each side of the base part also form a stack; and whereby each stack of the legs is covered by insulation barrier. The invention is characterized in that the insulation barrier comprises partition walls, the partition walls being made of electrically insulative and heat resistant material, whereby partition walls are formed as insulation sheets arranged in a spaced relation in a stack, meshing with each stack of the legs and separating the legs from each other.

[0018] Preferably, the insulation barrier is formed by an insulation cover and the bottom part of the housing, adjacent to the legs, whereby the partition walls form one piece with the insulation cover and protrude from each insulation cover.

[0019] Alternatively, the insulation barrier is formed by the insulation cover and the bottom part of the housing, adjacent to the legs, whereby the partition walls are formed as insulation sheets protruding from each of the bottom parts of the housing, adjacent to the legs.

[0020] Alternatively, the insulation barrier is formed by the insulation cover having partition walls protruding from it and having a vertical wall, whereby the vertical wall is placed between the legs and the housing.

[0021] Alternatively, the insulation barrier is formed by the housing adjacent to the legs, whereby the housing is shaped to have a part forming the insulation cover, and whereby the partition walls protrude from each of the bottom parts of the housing, adjacent to the legs.

[0022] Preferably, the legs are covered from their bottom side by a bottom part of the insulation cover.

[0023] Alternatively, the legs are covered from their bottom side by a bottom part of the housing.

[0024] Preferably, the thickness of the insulation cover is at least 2,6 mm.

[0025] Preferably, the thickness of the vertical wall is between 2 mm to 10 mm.

[0026] Preferably, the insulation cover is connected with the housing by pins protruding from the housing inserted into respective openings in the insulation cover or by pins protruding from the insulation cover inserted into respective openings in the housing.

[0027] Alternatively, the insulation barrier is connected with the housing by pins protruding from the housing inserted into respective openings in the insulation barrier or by pins protruding from the insulation barrier inserted into respective openings in the housing.

[0028] Preferably, the partition walls are made of material resistant to temperatures of at least 150°C.

[0029] Preferably, the insulation barrier with partition walls is made of electrically insulative and heat resistant resin, preferably unsaturated polyester.

[0030] Alternatively, the insulation barrier with partition walls is made of an inorganic insulating material, preferably ceramics.

[0031] Preferably, the thickness of partition walls is from 0,2 mm to 0,6 mm smaller than the distance between subsequent splitter plates.Brief Description of the Drawings

[0032] The present invention will be presented in a more detailed way with reference to the accompanying drawing, in which: Fig. 1 shows the cross-section of the arc chute parallel to the plane of the splitter plates, according to the first embodiment; Fig. 2 shows the external view of the arc chute from the front, parallelly to the plane of the splitter plates, according to the first embodiment; Fig. 3 shows partial cross-section of the DC circuit breaker and arc chute; Fig. 4 shows a cross-section of the arc chute parallel to the plane of the splitter plates, in a more detailed view showing the splitter plates inserted between partition walls, according to the first embodiment; Fig. 5 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates, according to the first embodiment; Fig. 6 shows the cross-section of the arc chute parallel to the plane of the splitter plates, in a view showing the splitter plates inserted between partition walls, according to the second embodiment; Fig. 7 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates, according to the second embodiment; Fig. 8 shows the cross-section of the arc chute parallel to the plane of the splitter plates, in a view showing the splitter plates inserted between partition walls, according to the third embodiment; Fig. 9 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates, according to the third embodiment; Fig. 10 shows the cross-section of the arc chute parallel to the plane of the splitter plates, in a view showing the splitter plates inserted between partition walls, according to the fourth embodiment; Fig. 11 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates, according to the fourth embodiment. Detailed Description

[0033] Preferred embodiments of the invention are described in detail below. The examples serve only as an illustration and do not limit the scope of the present invention.

[0034] The invention, in general, concerns an arc chute for direct current switching device, which may be provided in various types of electric equipment such as circuit breakers, contactors etc. The device may more particularly be employed in a direct current (DC) circuit breaker, specifically for low and medium voltage application. The arc chute according to the invention is designed to be used in industrial applications, for example in DC circuits on railway, tramways or metro power distribution systems, copper processing plants, mining or steel mills.

[0035] DC circuit breaker normally comprises a switch with a first switch contact and a second switch contact, wherein the second switch contact is movable between a first position, in which the first switch contact is touching the second switch contact, and a second position, in which the first and second switch contacts are separated from each other. Further, DC circuit breaker comprises an arc chute having a stack of a plurality of substantially parallel metal plates separated from each other by a certain distance, as it was described above. The arc chute typically also comprises a pair of arc horns for guiding the arc in the arc chute towards the splitter plates 1. Arc horns are connected with arc runners, the arc runners being elements of the circuit breaker which guide the arc towards the arc chute. In other words, arc horns placed in the arc chute are the end elements of the arc runners.

[0036] Arc chute according to the invention, in all possible embodiments, shown in the attached Figures, comprises at least one stack formed by a plurality of substantially parallel splitter plates 1, separated by air gaps. Air gaps between splitter plates 1 may be equal or may be of different width. Splitter plates 1 are arranged in spaced relation in a stack, and their arrangement is obtained (dependent on the particular embodiment) for example by positioning them, dependent on the embodiment, by housing 2 and / or partition walls 4 and / or insulation barrier 5. In some embodiments, splitter plates 1 may be mounted in some support structure or in grooves located on the internal side of housing 2. However, supporting and positioning of the splitter plates 1 may be achieved differently.

[0037] In all presented embodiments, the arc chute has insulation plates 3 placed above the splitter plates 1. Insulation plates 3 also form a stack like splitter plates 1. The edges of the insulation plates 3 face the edges of the splitter plates 1. The number of insulation plates 3 may be equal to the number of splitter plates 1. In another embodiment, which is shown in the Figures (this is visible especially in Fig. 3), for example due to the structure of the arc chute (due to presence of mounting points of the arc chute on the side walls of the housing 2), the number of insulation plates 3 may be smaller than the number of the splitter plates 1.

[0038] In all presented embodiments, the splitter plates 1 (on their bottom side, i.e. in their lower part) have legs 12, formed by longitudinal protrusions of each splitter plate 1. Each splitter plate 1 has thus a substantially continuous part - base part 11 - and a leg part - legs 12, so that each splitter plate 1 is longer on its both ends - thus, the gap is formed between its lower ends (legs 12), and each splitter plate 1 has the form of inverted V-shaped opening. Thus, each of the splitter plates 1 includes a base part 11 and two legs 12, which are extending from two opposite sides of the base part 11. Legs 12 of each splitter plate 1 form a stack, same as the base parts 11 of the splitter plates 1. The legs 12 are substantially parallel to each other. Typically, the width of the legs 12 is from 5 mm in their narrowest place to 12 mm in their widest place - preferably 8 mm. The thickness of the legs 12 (as well as the base part 11) is from 2 mm to 3 mm, preferably 2,5 mm. The shape of the arc splitter plate 1 is such that in the presence of the magnetic field the arc is drawn towards the apices of the V-shaped openings in each of the arc splitter plates 1. At the top of the V-shaped openings the presence of the magnetic field is mitigated and the arc is broken down into a plurality of arcs known as series arcs.

[0039] The arc chute is also equipped with a housing 2, surrounding the splitter plates 1 and insulation plates 3. The housing 2 is made of electrically insulative and heat resistant material. The housing 2 is thus made, for example, of electrically insulative and heat resistant resin, such as UP (unsaturated polyester), or of inorganic insulating material such as ceramics.

[0040] The essence of the invention is providing partition walls 4 formed as a stack of insulating sheets, which mesh with the legs 12 and separate them from each other, such as there is formed a stack of alternatingly arranged legs 12 and partition walls 4.

[0041] First embodiment of the invention is shown in Figs. 1, 2, 4 and 5. The arc chute according to the first embodiment of the invention is schematically presented in Fig. 1, showing a cross-section of the arc chute parallel to the plane of the splitter plates 1. Fig. 2 shows the external view of the arc chute from the front, parallelly to the plane of the splitter plates 1, showing that the legs 12 are covered also from their front (and rear) side. Fig. 4 shows a cross-section of the arc chute parallel to the plane of the splitter plates 1, in a more detailed view showing the splitter plates 1 inserted between partition walls 4. Fig. 5 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates 1.

[0042] Fig. 3 shows partial cross-section of the DC circuit breaker and arc chute, whereby the cross-section is perpendicular to the plane of the splitter plates 1 - this Fig. 3 shows the arrangement of splitter plates 1 and insulation plates 3, which may be arranged such that the heights of the splitter plates 1 are alternating - in each subsequent pair, splitter plate 1 is, respectively, longer or shorter, whereby the corresponding insulation plate 3 is, respectively, shorter or longer.

[0043] In this first embodiment, the insulation barrier 5 covers each of the legs 12, such as the legs 12 are insulated from each other by the partition walls 4 of the insulation barrier 5. The insulation barrier 5 is formed by a lower part of the housing 2, adjacent to the legs 12, and by the insulation cover 6. The lower part of the housing 2 covers the legs 12 from their external side, whereby the insulation cover 6 covers the legs 12 from their internal side (from the side of the V-shaped openings - from the side of the arc) and also from the lateral side of the most external splitter plates 1, as well as from their bottom side. The insulation cover 6 is equipped with partition walls 4, separating the legs 12 from each other. This can be best seen in Fig. 4 and Fig. 5 - partition walls 4 connected with insulation cover 6 resemble a shape of the comb. Insulation cover 6 is connected with the housing 2, in order to be stably mounted, for example by pins protruding from the housing 2 (shown in Fig. 5), inserted into respective openings in the bottom of the insulation cover 6 (in the part of the insulation cover which does not have partition walls 4 protruding from it). The pins may also protrude from the insulation cover 6 and be inserted into respective openings in the housing 2.

[0044] To be precise, each stack of the legs 12 (on the left and on the right side of the base part 11) is covered by its own insulation barrier 5. One insulation barrier 5 may, in another embodiment, cover several stacks of legs 12 (this embodiment is not shown in the Figures). Each stack of the legs 12 is thus equipped with the partition walls 4 arranged parallelly to the legs 12 and formed as a part of the insulation cover 6. In other words, partition walls 4 and insulation cover 6 form one-piece element, meshing with legs 12 and covering them from the side of the V-shaped opening, whereby from the other side the splitter plates 1 are covered by the bottom part of the housing 2. Partition walls 4 are formed as a stack of insulating sheets, which mesh with the legs 12 (they fill in the gaps between the legs 12) and separate the legs 12 from each other, such as there is formed a stack of alternatingly arranged legs 12 and partition walls 4. As mentioned above, the insulation cover 6 also may cover the legs 12 from their bottom side. The thickness of the insulation cover 6, preferably, should not be smaller than 2,5 mm. This thickness is measured between the edge of the leg 12 and the surface (from the internal side of the arc chute) od the insulation cover 6 in its thinnest part. The thickness of partition walls 4 depends on the distance between subsequent splitter plates 1 and usually is about 0,2 to 0,6 mm smaller than this distance, in order to create a space for installation purposes.

[0045] In one variation of the first embodiment, the bottom side of the stack of legs 12 may be covered by a piece of the housing 2 instead of a piece of the insulation cover 6 (not shown in the Figures).

[0046] Second embodiment of the invention is shown in Figs. 6 and 7. The arc chute according to the second embodiment of the invention is schematically presented in Fig. 6, showing a cross-section of the arc chute parallel to the plane of the splitter plates 1, where the splitter plates 1 are inserted between partition walls 4. Fig. 7 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates 1.

[0047] In this second embodiment, the insulation barrier 5 covers each of the legs 12, such as the legs 12 are insulated from each other by the partition walls 4. The insulation barrier 5 is formed by a lower part of the housing 2, adjacent to the legs 12, and by the insulation cover 6. The lower part of the housing 2 covers the legs 12 from their external side, whereby the insulation cover 6 covers the legs 12 from their internal side (from the side of the V-shaped openings - from the side of the arc) and also from the lateral side of the most external splitter plates 1. Most external splitter plates 1 may be covered by a part of housing 2 or by a part of insulation cover 6. The housing 2 is equipped with partition walls 4, separating the legs 12 from each other - partition walls 4 are connected with housing 2 and resemble a shape of the comb. The bottom side of the legs 12 is covered by a part of the housing 2 below the partition walls 4. The bottom side of the legs 12 may also be covered by a bottom part of the insulation cover 6 (this is not shown in the Figures).

[0048] Each stack of the legs 12 is covered by its own insulation barrier 5. One insulation barrier 5 may, in another embodiment, cover several stacks of legs 12 (this embodiment is not shown in the Figures). Each stack of the legs 12 is thus equipped with the partition walls 4 formed as a part of the housing 2 - in other words, partition walls 4 and housing 2 form one-piece element, meshing with the legs 12 and also covering them from the bottom (from their lowest part), whereby from the other side the legs 12 are covered by the insulation cover 6. Thus, in the second embodiment the insulation cover 6 does not have partition walls 4 - instead, it is formed as a smooth element covering the legs 12 from the side from the arc. Partition walls 4 are formed as a stack of insulating sheets, which mesh with the legs 12 (they fill in the gaps between the legs 12) and separate them from each other, such as there is formed a stack of alternatingly arranged legs 12 and partition walls 4. The insulation cover 6 may be connected with the housing 2 for example by pins protruding from the housing 2 inserted into respective openings in the insulation cover 6, or by pins protruding from the insulation cover 6 inserted into respective openings in the housing 2. The openings in the housing 2 for receiving pins are visible in Fig. 7. The thickness of the insulation cover 6, preferably, should not be smaller than 2,5 mm, similarly as in the first embodiment. The thickness of partition walls 4 depends on the distance between subsequent splitter plates 1 and usually is about 0,2 to 0,6 mm smaller than this distance.

[0049] In one variation of the second embodiment, the bottom side of the stack of legs 12 may be covered by a piece of the insulation cover 6 instead of a piece of the housing 2 (not shown in the Figures).

[0050] Third embodiment of the invention is shown in Figs. 8 and 9. The arc chute according to the third embodiment of the invention is thus schematically presented in Fig. 8, showing a cross-section of the arc chute parallel to the plane of the splitter plates 1, where the splitter plates 1 are inserted between partition walls 4. Fig. 9 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates 1.

[0051] In this third embodiment, the insulation barrier 5 also covers each of the legs 12, such as the legs 12 are insulated from each other by the partition walls 4. The insulation barrier 5 is in this case formed by the appropriately shaped insulation cover 6 having additionally a vertical wall 7. The insulation cover 6 covers the legs 12 from their internal side (from the side of the V-shaped openings - from the side of the arc), from the lateral side of the most external splitter plates 1, from their bottom, as well as from their side which was in the previous embodiments covered by the housing 2 - i.e. from the side of the housing 2. The insulation cover 6 is equipped with partition walls 4, separating the legs 12 from each other - partition walls 4 are connected with insulation cover 6 and resemble a shape of a comb. Further, insulation cover 6 has the vertical wall 7, which is placed between the legs 12 and the housing 2. Thus, the legs 12 are covered from each side solely by the insulation cover 6 having the vertical wall 7, partition walls 4 and obviously a part covering the legs 12 from the side of the V-shaped opening and from their bottom side. The insulation cover 6 can be placed on the legs 12 by inserting it (sliding) from the bottom side of the legs 12. Insulation barrier 5 is preferably connected with the housing 2, in order to be stably mounted, for example by pins protruding from the housing 2 (shown in Fig. 9), inserted into respective openings in the insulation barrier 5 (for example in its vertical wall 7), or by pins protruding from the insulation barrier 5 inserted into respective openings in the housing 2.

[0052] Each stack of the legs 12 is covered by its own insulation barrier 5. One insulation barrier 5 may, in another embodiment, cover several stacks of legs 12 (this embodiment is not shown in the Figures). Each stack of the legs 12 is thus equipped with the partition walls 4 formed as a part of the insulation cover 6 - in other words, the insulation cover 6 with partition walls 4 and vertical wall 7 form one-piece element - insulation barrier 5, meshing with the legs 12 and also covering them from their bottom (from their lowest part) and from their lateral sides. Partition walls 4 are formed as a stack of insulating sheets, which mesh with the legs 12 (they fill in the gaps between the legs 12) and separate them from each other, such as there is formed a stack of alternatingly arranged legs 12 and partition walls 4. The thickness of the insulation cover 6, preferably, should not be smaller than 2,5 mm, similarly as in previous embodiments. The thickness of partition walls 4, as in previous embodiments, depends on the distance between subsequent splitter plates 1 and usually is from 0,2 to 0,6 mm smaller than this distance. The thickness of the vertical wall 7 depends on the material used and production method of this element; nevertheless, its thickness may be comprised between 2 to 10 mm.

[0053] In the fourth embodiment of the invention, shown in Figures 10 and 11, the insulation barrier 5 also covers each of the legs 12, such as the legs 12 are insulated from each other by the partition walls 4. The arc chute according to the fourth embodiment of the invention is thus schematically presented in Fig. 10, showing a cross-section of the arc chute parallel to the plane of the splitter plates 1, where the splitter plates 1 are inserted between partition walls 4. Fig. 11 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates 1.The insulation barrier 5 is in this case formed solely by the appropriately shaped housing 2. The housing 2 thus has a part covering the legs 12 from their internal side (from the side of the V-shaped openings - from the side of the arc), a part covering the stack of legs 12 from the lateral side of the most external splitter plates 1, as well as a part covering the stack of legs 12 from its bottom side. The housing 2 is equipped with partition walls 4, separating the legs 12 from each other - partition walls 4 are connected with housing 2 and resemble a shape of a comb. Thus, the legs 12 are covered from each side solely by the housing 2 having partition walls 4. In other words, housing 2 is shaped to have a part forming the insulation cover 6 as in previous embodiments, covering the stack of legs 12 from the side of the V-shaped opening, and to have a part covering the stack of legs 12 from their bottom side. In yet another words, the fourth embodiment resembles the second embodiment shown in Figs. 6 and 7, in which the housing 2 having partition walls 4 forms one piece with the insulation cover 6.

[0054] Each stack of the legs 12 is covered by its own insulation barrier 5. Each stack of the legs 12 is thus equipped with the partition walls 4 formed as a part of the housing 2 - in other words, the housing 2 with partition walls 4 and parts covering the remaining sides of the stack of legs 12 (bottom and sides as mentioned above) form one-piece element - insulation barrier 5, meshing with the legs 12 and also covering them from their bottom (from their lowest part) and from their lateral sides. Partition walls 4 are formed as a stack of insulating sheets, which mesh with the legs 12 (they fill in the gaps between the legs 12) and separate them from each other, such as there is formed a stack of alternatingly arranged legs 12 and partition walls 4. The thickness of the part covering the stack of legs 12 from the side of the V-shaped openings, forming the insulation cover 6 as in previous embodiments, should not be smaller than 2,5 mm, similarly as in previous embodiments. The thickness of partition walls 4, as in previous embodiments, depends on the distance between subsequent splitter plates 1 and usually is from 0,2 to 0,6 mm smaller than this distance.

[0055] In this fourth embodiment, the arc chute may be formed easily by means of 3D printing, since in this case the arc chute (excluding splitter plates 1 and insulation plates 3) is manufactured as one-piece element. In all of the embodiments, the walls of the housing 2 are manufactured as one-piece element.

[0056] Splitter plates legs 12, in all of the presented embodiments, are made of metal, preferably steel (since they form a part of the splitter plates 1, they are made of the same material as splitter plates 1). The partition walls 4 (as well as other parts of insulation barrier 5) are in all presented embodiments preferably made of the same material as the housing 2. Preferably, this material is resistant to temperatures of at least 150°C. More preferably, the material is resistant to temperatures of between 150 to 210°C - in the state of the art, standard insulating materials in this type of structures have a resistance to continuous temperatures between 150-210°C. The material may be for example an electrically insulative and heat resistant resin (for example unsaturated polyester).

[0057] Such a resistancy is necessary due to the necessity to withstand the temperature to which the splitter plates 1 are heated up during arc extinguishing process. All insulating materials in the arc chute are briefly exposed (for less than a second - usually for several miliseconds) to a very high electric arc temperature (up to approx. 5700°C). After that, they are exposed to the temperature to which the splitter plates 1 heated up during arc extinguishing process - this temperature can reach up to 500°C.

[0058] The partition walls 4 (and housing 2) may also be made of material having higher temperature resistancy (even above 500°C), such as inorganic insulating materials - various types of ceramics or glass-cement materials. However, due to high costs, poorer mechanical properties and water absorption, these materials are used only in justified cases.

[0059] In all embodiments, partition walls 4 are made of heat-resistant insulation material, for example from a material made of glass and polyester, or made of ceramics, or made of glass and concrete (as discussed above). Partition walls 4 have generally a shape of a comb (they are formed as a stack of insulation sheets) - this arrangement is crucial since, as said before, if the legs 12 would be covered only from the outside, the arc would reignite and would be formed on the lower edges of the legs 12, leading to erosion of the legs 12 and adjacent insulating materials, overheating of the arc chute and of other circuit breaker components. Providing partition walls 4 allows to fill the air gaps between the legs 12 of the splitter plates 1, and thus separate them from each other. Thanks to that, the reigniting arc no longer forms on the lower edges of the legs 12.

[0060] To sum up, there is provided an arc chute having insulation barrier 5, formed either by a part of the housing 2 and the insulation cover 6 having partition walls 4, or by a part of the housing 2 having partition walls 4 and by a plain insulation cover 6, or by the insulation cover 6 having partition walls 4 and the vertical wall 7 perpendicular to the legs 12, the vertical wall 7 being placed between the housing 2 and the legs 12, or formed solely by the housing 2. The partition walls 4 are formed as a stack of substantially parallel insulation sheets separating the legs 12 from each other. This allows to protect metal parts (the splitter plates 1 legs 12 and also bottom area of side walls) from direct contact with electric arc, and therefore degradation of splitter plates 1 and arc chutes walls due to burning arc during switching operation is avoided. In other words, the presence of the partition walls 4 between the legs 12 prevents the arc from burning between these legs 12 (arc reignition below the splitter plates 1 and between the legs 12 is prevented). Partition walls 4 direct the arc towards the center of the arc chute and reduce risk of run-back of arc to the bottom area of arc chute and possibility of arc reignition between breaker arc runners. Thus, the arc is burning only above the legs 12, in the region of the base parts 11 (between base parts 11 of the splitter plates 1), comprising greater amount of material. The legs 12 are completely surrounded by insulating material, which additionally forms a uniform, smooth surface on the side of the arc that does not disturb (does not cause turbulence) the movement of the arc towards the splitter plates 1.

[0061] The arc chute disclosed herein is intended for being arranged in a switching device such as circuit breaker, comprising a stationary contact and a moveable contact, connectable / disconnectable to said stationary contact, forming an electrical switch.List of reference numerals:

[0062] 1 - splitter plate 11 - base part 12 - legs 2 - housing 3 - insulation plate 4 - partition walls 5 - insulation barrier 6 - insulation cover 7 - vertical wall

Examples

first embodiment

[0041]First embodiment of the invention is shown in Figs. 1, 2, 4 and 5. The arc chute according to the invention is schematically presented in Fig. 1, showing a cross-section of the arc chute parallel to the plane of the splitter plates 1. Fig. 2 shows the external view of the arc chute from the front, parallelly to the plane of the splitter plates 1, showing that the legs 12 are covered also from their front (and rear) side. Fig. 4 shows a cross-section of the arc chute parallel to the plane of the splitter plates 1, in a more detailed view showing the splitter plates 1 inserted between partition walls 4. Fig. 5 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates 1.

[0042]Fig. 3 shows partial cross-section of the DC circuit breaker and arc chute, whereby the cross-section is perpendicular to the plane of the splitter plates 1 - this Fig. 3 shows the arrangement of splitter plates 1 and insulation plates 3, which may be arranged su...

second embodiment

[0046]Second embodiment of the invention is shown in Figs. 6 and 7. The arc chute according to the invention is schematically presented in Fig. 6, showing a cross-section of the arc chute parallel to the plane of the splitter plates 1, where the splitter plates 1 are inserted between partition walls 4. Fig. 7 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates 1.

[0047]In this second embodiment, the insulation barrier 5 covers each of the legs 12, such as the legs 12 are insulated from each other by the partition walls 4. The insulation barrier 5 is formed by a lower part of the housing 2, adjacent to the legs 12, and by the insulation cover 6. The lower part of the housing 2 covers the legs 12 from their external side, whereby the insulation cover 6 covers the legs 12 from their internal side (from the side of the V-shaped openings - from the side of the arc) and also from the lateral side of the most external splitter plates 1. Mo...

third embodiment

[0050]Third embodiment of the invention is shown in Figs. 8 and 9. The arc chute according to the invention is thus schematically presented in Fig. 8, showing a cross-section of the arc chute parallel to the plane of the splitter plates 1, where the splitter plates 1 are inserted between partition walls 4. Fig. 9 shows an exploded view of a cross-section of the arc chute parallel to the plane of the splitter plates 1.

[0051]In this third embodiment, the insulation barrier 5 also covers each of the legs 12, such as the legs 12 are insulated from each other by the partition walls 4. The insulation barrier 5 is in this case formed by the appropriately shaped insulation cover 6 having additionally a vertical wall 7. The insulation cover 6 covers the legs 12 from their internal side (from the side of the V-shaped openings - from the side of the arc), from the lateral side of the most external splitter plates 1, from their bottom, as well as from their side which was in the previous embodi...

Claims

1. An arc chute for a direct current switching device, comprising at least one stack formed by a plurality of substantially parallel metallic splitter plates (1), at least one stack formed by a plurality of substantially parallel insulation plates (3), the edges of the insulation plates (3) facing the edges of the splitter plates (1), a housing (2) made of electrically insulating material surrounding the at least one stack of splitter plates (1) and the at least one stack of insulation plates (3), wherein each of the splitter plates (1) includes a base part (11) and two legs (12) extending from two opposite sides of the base part (11), whereby the legs (12) on each side of the base part (11) also form a stack, whereby each stack of the legs (12) is covered by insulation barrier (5), characterized in that the insulation barrier (5) comprises partition walls (4), the partition walls (4) being made of electrically insulative and heat resistant material, whereby partition walls (4) are formed as insulation sheets arranged in a spaced relation in a stack, meshing with each stack of the legs (12) and separating the legs (12) from each other.

2. The arc chute for a direct current switching device according to claim 1, wherein the insulation barrier (5) is formed by an insulation cover (6) and the bottom part of the housing (2), adjacent to the legs (12), whereby the partition walls (4) form one piece with the insulation cover (6) and protrude from each insulation cover (6).

3. The arc chute for a direct current switching device according to claim 1, wherein the insulation barrier (5) is formed by the insulation cover (6) and the bottom part of the housing (2), adjacent to the legs (12), whereby the partition walls (4) are formed as insulation sheets protruding from each of the bottom parts of the housing (2), adjacent to the legs (12).

4. The arc chute for a direct current switching device according to claim 1, wherein the insulation barrier (5) is formed by the insulation cover (6), having partition walls (4) protruding from it, and having a vertical wall (7), whereby the vertical wall (7) is placed between the legs (12) and the housing (2).

5. The arc chute for a direct current switching device according to claim 1, wherein the insulation barrier (5) is formed by the housing (2) adjacent to the legs (12), whereby the housing (2) is shaped to have a part forming the insulation cover (6), and whereby the partition walls (4) protrude from each of the bottom parts of the housing (2), adjacent to the legs (12).

6. The arc chute for a direct current switching device according claim 2 or 3 or 4, wherein the legs (12) are covered from their bottom side by a bottom part of the insulation cover (6).

7. The arc chute for a direct current switching device according claim 2 or 3 or 5, wherein the legs (12) are covered from their bottom side by a bottom part of the housing (2).

8. The arc chute for a direct current switching device according to claim 2 or 3 or 4 or 5 or 6 or 7, wherein the thickness of the insulation cover (6) is at least 2,6 mm.

9. The arc chute for a direct current switching device according to claim 4 or 6 or 8, wherein the thickness of the vertical wall (7) is between 2 mm to 10 mm.

10. The arc chute for a direct current switching device according to claim 2 or 3 or 6 or 7 or 8, wherein the insulation cover (6) is connected with the housing (2) by pins protruding from the housing (2) inserted into respective openings in the insulation cover (6) or by pins protruding from the insulation cover (6) inserted into respective openings in the housing (2).

11. The arc chute for a direct current switching device according to claim 4 or 6 or 8 or 9, wherein the insulation barrier (5) is connected with the housing (2) by pins protruding from the housing (2) inserted into respective openings in the insulation barrier (5) or by pins protruding from the insulation barrier (5) inserted into respective openings in the housing (2).

12. The arc chute for a direct current switching device according to any of the preceding claims, wherein the partition walls (4) are made of material resistant to temperatures of at least 150°C.

13. The arc chute for a direct current switching device according to claim 11, wherein the insulation barrier (5) with partition walls (4) is made of electrically insulative and heat resistant resin, preferably unsaturated polyester.

14. The arc chute for a direct current switching device according to claim 11, wherein the insulation barrier (5) with partition walls (4) is made of an inorganic insulating material, preferably ceramics.

15. The arc chute for a direct current switching device according to any of the preceding claims, wherein the thickness of partition walls (4) is from 0,2 mm to 0,6 mm smaller than the distance between subsequent splitter plates (1).

Images