WO2012025555A1

WO2012025555A1 - Arc chute for a circuit breaker, circuit breaker and method for assembling an arc chute

Info

Publication number: WO2012025555A1
Application number: PCT/EP2011/064521
Authority: WO
Inventors: Philippe Noisette; Yoann Alphand
Original assignee: Abb Technology Ag
Priority date: 2010-08-25
Filing date: 2011-08-24
Publication date: 2012-03-01
Also published as: CN103155075A; EP2609609B1; CN103155075B; EP2609609A1

Abstract

The present disclosure relates to an arc chute for a DC circuit breaker comprising at least two parallel stacks (102, 106) of a plurality of substantially parallel metal plates (104, 104a, 104b, 104n, 108, 108a, 108b, 108n) defining a first axis (A) in parallel to a stacking direction, wherein the metal plates of the same stack have a reference distance (D1) between adjacent metal plates in the direction of the first axis; an arc space (109) defined between the two parallel stacks and adapted to allow an arc to move along the first axis, wherein a second axis (X) traverses the at least two parallel stacks in parallel to the metal plates and the arc space (109), wherein the second axis is substantially orthogonal to the first axis and an arc chute housing (111) having at least one top wall limiting the interior of the arc chute housing in the direction of the first axis, wherein a channel (113a, 113b) is formed between the top wall and the metal plate (104n, 108n) closest to the top wall of the at least one stack (102, 106), the channel having an extension (D3) in the direction of the first axis at least 2 times the reference distance (D1). Further, the present disclosure relates to a circuit breaker and a method for assembling an arc chute of a circuit breaker.

Description

Arc chute for a circuit breaker, circuit breaker and method for assembling an arc chute

The present disclosure relates to an arc chute for a direct current (DC) circuit breaker, in particular, rated for a medium voltage or having a nominal medium voltage. More specifically, the present disclosure relates to a direct current circuit breaker including at least one stack of a plurality of substantially parallel metal plates, the at least one stack defining a first axis in parallel to a stacking direction; an arc space adapted to allow an arc to extend along the first axis, wherein a second axis traverses parallel to the metal plates the at least one stack and the arc space and is substantially orthogonal to the first axis. Typically, medium voltage is a voltage between 400V and 4000V.

Further the present disclosure relates to a circuit breaker and to a method for assembling an arc chute.

Typically, circuit breakers or air circuit breakers are used in a DC circuit on railway vehicles. Other examples may be tramways or trolley buses. For example, such high speed DC circuit breakers may switch direct currents of 1.5 kA with a voltage level of more than 900 Volt.

In arc chute assemblies of conventional DC circuit breakers, plastic frames and metal plates are alternating stacked upon each other, wherein the metal plates are disposed on the plastic frames. The plastic frames have a cut-out such that an arc may be built up between two adjacent metal plates. The plastic frames are used to generate gas, when disconnecting the switch contact, such that the heat in the arc is quickly exhausted from the arc chute and to increase the arc voltage by a change of the chemical composition of the air between the metal plates. Typically, the gas is exhausted to all sides of the metal plates in the arc chute.

The plastic frames form dielectric layers between the metal plates. The arc chutes are then covered by a moulded housing. As the gas is exhausted on all sides, the circuit breaker needs a large amount of space which cannot be used by other equipment. Typically, the space on rolling stock is limited.

It is well-known that it is necessary to elongate and force an arc within the arc chute to build up sufficient voltage, such that the DC current may be cut. The faster the voltage is built up, the shorter the total arcing time will be.

At low currents with respect to the nominal current, for example a current from 10 A to 100 A in the case of a nominal current of 1200 A to 4500 A, there is a low current density, particularly in the arc, such that the magnetic field required to force the arc within the arc chute is limited. Further, the arc feet may have difficulties leaving the contact tips to climb inside the arc chamber or arc chute. Thus, it may take time to build up the required voltage from in certain cases, the arc may adhere to one contact tip such that only 50% of the voltage is built up and the current will never be cut. In another scenario the arc may stick on or adhere to both fixed and mobile contacts such that no voltage built up and the current will never cut.

DEI 02008021025 Al discloses an arc chute unit for a motor protective switch having a single stack of parallel arc chute plates arranged into three groups and between the arc runner plates. The distance of the respective groups or between the peripheral group and the adjacent arc runner plate is at least 2 times of the distance between adjacent arcing chute plates. In such way a high number of arc chute plates are arranged in the limited space of the arcing chamber.

For that reason some arc chutes or circuit breakers includes self blow up coils which are activated depending on the current such that a magnetic field is provided to push up the arc into the arc chute.

However, such a solution is complicated and needs blow-up coils and a control circuit, for example a printed circuit board, for controlling the coil generating the field.

Objects of the invention is to provide a arc chute, an circuit breaker and a method for assembling an arc chute which present not the inconvenience of the known arc chute, in particular to provide an arc chute which needs less maintenance and is easier to build.

According to a first aspect, an Arc chute for a DC circuit breaker is provided including at least two stacks of a plurality of substantially parallel metal plates, the at least two parallel stacks defining a first axis in parallel to a stacking direction, wherein the metal plates of the same stack have a reference distance between adjacent metal plates in the direction of the first axis and wherein a second axis traverses the at least two parallel stacks in parallel to the metal plates and the arc space (109), wherein the second axis is substantially orthogonal to the first axis; an arc space is defined between the two parallel stacks and is adapted to allow an arc to move along the first axis; and an arc chute housing having at least one top wall limiting the interior of the arc chute housing in the direction of the first axis, wherein a channel is formed between the top wall and the metal plate closest to the top wall of the at least one stack, the channel having an extension in the direction of the first axis at least 2 times the reference distance.

The reference distance between two adjacent metal plates of the same stack of the plurality of parallel metal plates may be, in an embodiment, the mean distance between two adjacent metal plates of the same stack of the plurality of parallel metal plates.

In a further embodiment, the reference distance is the distance in the direction of the first axis between two adjacent metal plates of the majority of pairs of two adjacent metal plates of the same stack. For example, the majority of pairs of two adjacent metal plates may include more than 70 percent of the metal plates, in particular more than 80 percent of metal plates, for example more than 90 percent of the metal plates. Thus, the majority of the metal plates, in particular more than 70 percent, for example more than 80 percent or more than 90 percent, of the metal plates, are equidistantly arranged in each stack.

In a typical embodiment, the channel having an extension in the direction of the first axis of more than 2,5 times, in particular more than 3 times, the reference distance and/or the channel having an extension in the direction of the first axis of less than 10 times, in particular less than 7 times the reference distance.

For example, in an embodiment the channel may have an extension in the direction of the first axis be between 5mm and 20 mm, in particular between 7 mm and 15 mm.

In an embodiment, the circuit breaker is an air DC circuit breaker. Thus, each current interruption generates an arc. Typically, an arc starts from a contact separation and remains until the current reaches zero. In embodiments, to be able to cut out DC currents high-speed DC circuit breakers build up DC voltages that are higher than the net voltage. To build up a DC voltage, air circuit breakers may use an arc chute or extinguish chamber in which metallic plates are used to split arcs into several partial arcs, the arc is lengthened and gases are used to increase the arc voltage by a chemical effect, for example by evaporation of plastic or another material.

With the arc chute, even at low currents with respect to the nominal current of the circuit breaker containing said arc chute, the arc is better forced upwards in the housing of the arc chute, in particular due to a gas flow from the switch contacts in the direction of the arc chute compared to conventional arc-chutes due to the channels at the upper end of the arc chute. For example, for currents between 10 A and 200 A or below 200 A with respect to the nominal current which is more than 5 times greater, in particular more than 10 times greater, for example a nominal current between 1000 A and 7000 A, in particular between 1200 A and 4500 A, the arc is better forced upwards or elongated in the housing of the arc chute.

In particular, the increased dimension of the channel in direction of the first axis compared to the spaces between the metal plates belonging to the stacks of metal plates, a gas flow is generated which helps to aspirate the arc towards the arc chute top. Such a gas flow is efficient, especially when the current is low with respect to the nominal current, when the magnetic field is too weak to force the arc. Typically, the magnetic field is created by the arc itself. At the nominal current, the enlarged space between the metal plates and the top wall has typically no substantial negative effect.

In a typical embodiment, the reference distance is between about 1 mm and about 8 mm, in particular between 2 mm and about 6 mm.

For example, in an embodiment, the top wall is substantially parallel to the surface of the plurality of metal plates and/or the normal of the top wall surface facing the interior of the arc chute is parallel to the first axis.

For example, in an embodiment, the top wall and/or the channel extends at least over the at least one stack, in particular all stacks, of a plurality of substantially parallel metal plates and the arc space, in particular along the second axis traversing in parallel to the metal plates the at least one stack and the arc space, wherein the second axis substantially orthogonal to the first axis.

In an embodiment, which may be combined with other embodiments disclosed herein, the top wall is closed, such that gas flow generated by an arc is directed through the channel out of the housing in the direction of the second axis traversing in parallel to the metal plates the at least one stack and the arc space, wherein the second axis is substantially orthogonal to the first axis. In other words, the top wall prevents a gas flow in the direction of the first axis.

Typically, an axis is parallel to the metal plates of the stack of the plurality of substantially parallel metal plates if the axis is parallel to a surface of the metal plates facing a surface of an adjacent metal plate in the direction of the first axis. In a typical embodiment, the arc chute further includes an arc chute housing having at least one side wall, said at least one side wall being substantially parallel to the first axis and/or second axis traversing in parallel to the metal plates the at least one stack and the arc space, wherein the second axis is substantially orthogonal to the first axis, wherein the distance between the at least one sidewall and the metal plates is less than 10mm, in particular less than 5 mm.

In an embodiment, which may be combined with other embodiments disclosed herein, the at least one side wall contacts the metal plates of the at least one stack.

In an embodiment, the side walls limit the channel in a direction orthogonal to the first axis and orthogonal to a second axis. Thus, the channel has a dimension orthogonal to the first axis and to the second axis corresponding to the extension of the metal plates in a direction orthogonal to the first axis and orthogonal to the second axis.

Typically, a circuit breaker using such an arc chute according to an embodiment consumes less space. This may be important for applications where space is limited, for example on trains.

For example, in an embodiment, the arc chute housing has two side walls, wherein both side walls have a distance to the metal plates of less than 10mm, in particular less than 5mm.

In an embodiment, the at least one side wall has a dimension in the direction of the second axis, such that the side wall completely covers at least the at least one stack, in particular two stacks, and the arc space. For example, in the case of two stacks, the side wall covers the two stacks and the arc space between the two stacks.

In an embodiment, the at least one side wall has a dimension in the direction of the second axis corresponding at least 110%, in particular at least 120%, of the dimension of the at least one stack, in particular of the two stacks, and the arc space in the direction of the second axis.

Typically, the side wall has a height corresponding to at least the dimension of the stack in the direction of the first axis.

In an embodiment, which may be combined with other embodiments disclosed herein, the side wall is substantially closed. Typically, the side wall prevents the gas flow in the direction of the third axis. Thus, gas is mainly directed in the direction of the second axis.

Thus, for each stack, the arc chute includes a gas exhaust only in one direction, in particular in the direction of the second axis traversing in parallel to the metal plates the at least one stack and the arc space, wherein the second axis is substantially orthogonal to the first axis.

For example, in an embodiment, which may be combined with other embodiments disclosed herein, the gas created when disconnecting the switch contacts of the circuit breaker is exhausted only in two directions, in particular in two opposite directions, for example in the direction of the second axis.

Hence, a gas exhaust in a direction of a third axis being orthogonal to the first axis and orthogonal to the second axis is prevented.

Thus, the arc chute may include two channels between the respective closest plates to the top wall and the top wall.

For example, in an embodiment, the two parallel stacks include a first stack and a second stack, wherein a distance between a metal plate of a first stack to the closest metal plate of the second stack is between 0,75 times and 2 times, in particular between 0,8 times and 1,5 times, the length of the extension of the metal plates in direction of the second axis and/or the length of the longitudinal edge of the metal plates.

For example, the distance between a metal plate of the first stack and the closest metal plate of the second stack corresponds to the length of the extension of the metal plates in the direction of the second axis.

For example, in the case where the metal plates of the first stack and/or the second stack have a different length in the direction of the second axis and/or a different length of the longitudinal edge, the distance between a metal plate of the first stack to the closest metal plate of the second stack is between 75 percent and 200 percent of the mean length of the extension of the metal plates in the direction of the second axis and/or the mean length of the longitudinal edge of the metal plates. Typically, a metal plate of the first stack and the closest metal plate of the second stack concerns metal plates, which are not electrically permanently connected to each other.

In an embodiment, which may be combined with other embodiment disclosed herein, the distance between a metal plate of a first stack to the closest metal plate of the second stack is between 75 mm and 200mm, in particular between 85 mm and 120 mm, for example about 100 mm, in the direction of the second axis and/or equivalent to the length of the longitudinal edge of the metal plates.

In a typical embodiment, the area of the arc space in a plane having a normal in the direction of the first axis corresponds substantially to the area of the surface of a metal plate. In an embodiment, the plane is limited in the direction of the second axis by the metal plates. For example, the area of the arc space in a plane having a normal in the direction of the first axis is between 5000 mm² and 10000 mm², in particular between 6000 mm² and 9000 mm². In another example, the area of the arc space in a plane having a normal in the direction of the first axis is between 80 percent and 150 percent of the area of the surface of a metal plate. Hence the space to generate a gas flow, which draws or forces the arc into the arc chute, is increased.

For example, in an embodiment, the metal plates of the stacks of metal plates are substantially rectangular and have, in particular, a substantially V-shaped or U-shaped cut-out directed towards the arc space, wherein a second axis is substantially parallel to two longitudinal edges of the metal plates extending adjacent to the sidewalls.

In an embodiment, the housing of the arc chute has at least one opening arranged such that gas may traverse the opening in the direction of the second axis traversing in parallel to the metal plates the at least one stack and the arc space, wherein the second axis is in particular substantially orthogonal to the first axis, wherein, in particular, the at least one opening has an opening surface parallel to a plane spanned by the first axis and the third axis, the third axis being orthogonal to the first axis and the second axis.

In an embodiment, which may be combined with other embodiments disclosed herein, the opening has a dimension in the direction of the first axis of at least 90%, in particular more than 95%, of the dimension in the direction of the first axis of the at least one stack.

In an embodiment, the opening has a dimension substantially corresponding to the dimension of the metal plates in a direction orthogonal to the first axis and the second axis, for example at least 90%, in particular at least 95%, of the width of the metal plates. Typically the width of the metal plates is measured along a third axis orthogonal to the first axis and orthogonal to the second axis.

In an embodiment, the metal plates are substantially rectangular, having a first transversal edge in the direction of the arc space and a second transversal edge opposite to the first transversal edge, and in particular two longitudinal edges substantially parallel to the second axis, wherein the opening of the arc chute housing is adjacent to and/or on the side of the second transversal edge of the metal plates.

In an embodiment, which may be combined with other embodiments disclosed herein, more than 70%), in particular more than 90%, of a surface of a metal plate of the at least one stack faces the surface of an adjacent metal plate in the same stack.

In an embodiment, which may be combined with other embodiments disclosed herein, the metal plates of the arc chute have a surface area from about 3000 mm² to about 12000 mm², in particular between about 5000 mm² and about 8000 mm², and/or have a ratio between the extension in the longitudinal direction, parallel to the second axis, and the extension in the transversal direction of about 1 to 2, in particular 1, 1 to 1,5.

According to a further aspect, a circuit breaker is provided, including a switch unit having a first switch contact and a second switch contact, wherein the second switch contact is movable between a first position, wherein the first switch contact contacts the second switch contact, and a second position, wherein the first and second switch contacts are separated from each other; and an arc chute according an embodiment disclosed herein.

In an embodiment, which may be combined with other embodiments, the circuit breaker is an air circuit breaker.

For example, in an embodiment, the circuit breaker is circuit breaker for a traction vehicle, in particular a railway vehicle, tramway, trolleybus, or the like.

In an embodiment, the circuit breaker may be adapted for rated for a voltage of more than 400 V and/or for currents of more than 1000 A, for example for rated or nominal currents between 1200 A and 4500 A.

In an embodiment, the second switch contact is movable substantially along a moving direction, wherein the second axis is substantially parallel to the moving direction. In an embodiment, which may be combined with other embodiments disclosed herein, the circuit breaker does not include a device for generating an electric and/or magnetic field for forcing an arc into the arc chute. The device for generating an electric and/or magnetic field may be a coil or the like.

In an embodiment, the positioning device is a screw, a hinge, a bolt, a stop, a bar, and the like. For example, the positioning device is used to connect the arc chute to the switching unit.

The present disclosure relates further to a method for assembling an arc chute of a circuit breaker, the arc chute including an arc space, said method including stacking of a plurality of substantially parallel metal plates parallel to a first axis to assemble two parallel stacks, wherein the arc space is adapted to allow an arc to extend along the first axis, wherein the metal plates of the same stack have a reference distance between adjacent metal plates in the direction of the first axis; and mounting at least one top wall of an arc chute housing, the top wall limiting the interior of the arc chute housing in the direction of the first axis, such that a channel is formed between the top wall and the closest metal plate of the at least one stack to the top wall, wherein the channel has an extension in the direction of the first axis of at least 2 times the reference distance.

For example, in an embodiment, the method further includes mounting the arc chute on a switching unit.

So that the manner in which the above recited features of the present invention can be understood in detail, a particular description of the invention, briefly summarized above, may be discussed with reference to embodiments. The accompanying drawings relate to embodiments of the invention and described in the following:

Fig. 1 shows schematically a side view of an embodiment of a circuit breaker with open switch contacts;

Fig. 2 shows schematically a perspective view of some elements of an embodiment of a circuit breaker;

Fig. 3 shows schematically a section of an arc chute in a top view; and

Fig. 4 shows schematically a perspective view of a circuit breaker according to an embodiment. Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in the figures. Each example is provided by way of explanation, and is not meant as a limitation of the invention. Within the following description of the drawings, the same reference numbers refer to the same components. Generally, only the differences with respect to individual embodiments are described.

Fig. 1 shows a side view of a medium-voltage direct-current (DC) circuit breaker. For example, the medium-voltage direct-current circuit breaker may be designed for a nominal current between 1000 and 7000 Amperes, in particular between 1200 and 4500 Amperes.

The circuit breaker is typically an air circuit breaker. The circuit breaker includes an arc chute 100 and a switch unit 200.

The arc chute includes a first stack 102 of metal plates 104a, 104b, 104n and a second stack 106 of metal plates 108a, 108b, 108n. Typically, the metal plates are equidistantly arranged in each stack. In other words, each adjacent pair of metal plates is spaced at the same distance Dl . For example, the distance between adj acent plates may be between 1mm and 8mm, in particular between 2 mm and 6mm. The metal plates of each stack are stacked in a stacking direction which is parallel to a first axis Y. Typically, the arc chute is symmetrical about a first axis Y.

In an embodiment, the number and the form of the metal plates 104a, 104b, 104n, 108a, 108b, ... , 108n of the first and the second stack 102, 106 are substantially equal.

Typically, the metal plates have a thickness from about 0,5 mm to about 8mm, in particular between 0,5 and about 3 mm, for example about 1mm. In an embodiment, which may be combined with other embodiments disclosed herein, the metal plates 104, 108 may have a surface area from about 3000 mm² to about 12000 mm², in particular between about 5000 mm² and about 8000 mm². In an embodiment, the volume of the metal plates is between about 3000 mm³ and about 20000 mm³, in particular between about 5000 mm³ and about 10000 mm³. For example a single metal plate or steel plate may have a weight between 30g and lOOg, for example about 50g.

An arc space 109 is disposed between the first stack 102 and the second stack 106 of metal plates. Typically, when the circuit breaker is opened, an arc mounts in the arc space 109 in an arc displacement direction A, typically corresponding to the first axis Y.

The lowest metal plate, or level zero metal plate 104a of the first stack 102 and the lowest metal plate, or level zero metal plate 108a of the second stack 106 are typically the closest metal plates of the respective stacks 102, 106 with respect to the switch unit 200. Hence, the lowest metal plates 104a, 108a and the top level plates 104n, 108n are disposed on opposite ends in the stacking direction, which is typically parallel to the arc displacement direction A or the first axis Y of the arc chute, of the respective stack 102, 106 of metal plates.

Typically, the surfaces of metal plates or deionising plates 104, 108 of the first stack 102 and the second stack 106 are parallel to a second axis X, which is typically orthogonal to the arc displacement direction A and the first axis Y.

In an embodiment, each stack 102, 106 includes about 36 metal plates 104a, 104b, ... 104n, 108a, 108b, ... 108n. Other embodiments may even include more than 36 metal plates. The number of metal plates typically depends on the nominal current that is switched by the circuit breaker.

The distance D2 between the metal plates of the first stack 102 and the metal plates of the second stack 106 corresponds substantially to the length in the direction of the second axis X of the metal plates. For example, in an embodiment, the distance D2 may be between 75 mm and 150 mm, for example 100 mm. Thus, there is enough space such that a gas flow may force or aspirate an arc into the arc space.

In an embodiment, the arc chute 100 includes a housing 111 having at least one side wall 112. In an embodiment, the at least one sidewall 112 is manufactured from a plastic plate. For example, the sidewalls are substantially closed to prevent a gas exhaust through the sidewalls. The side walls 112 are disposed typically in a plane parallel to a plane spanned by the first axis Y and the second axis X.

Further, the housing 111 includes a top wall 150 which has a surface facing the interior of the arc chute, such that a channel 113a, 113b is formed between the respective closest metal plates, i.e. the top level plates 104n, 108n, which has an extension D3 in direction of the first axis Y, wherein extension D3 is at least two times greater than the distance Dl between a pair of metal plates in the respective stacks 102, 106. Thus, a gas flow can be developed in the channels 113a, 113b. This enables the gas flow to force or pull up the arc into the arc chute even at low currents with respect to the nominal current of the arc chute. Typically, the surface facing the interior of the arc chute has a normal direction being parallel to the first axis Y. The channel width, in direction of third axis Z being orthogonal to the first axis Y and orthogonal to the second axis X, corresponds substantially to the dimension of the metal plates in direction of third axis. Typically, the channel is limited in direction of the third axis Z by the side walls 112. The thick arrows 115 indicate the gas flow through the arc chute in case of low currents with respect to the nominal current. In particular, the gas flow through the channels 113a, 113b is more important than the gas flow between two adjacent metal plates of a stack 104, 106. Thus, the arc is drawn to the top of the arc chute, which enables a split up in a plurality of small arcs between adjacent metal plates.

The arc chute 100, along with its housing, may be easily separated from the switch unit 200. Thus, the maintenance time may be reduced. For example, a positioning device is used to arrange the arc chute at the correct position on the switch unit. The positioning device may be a stop, a screw, or another device to provide the arc chute 100 at the correct position on the switch unit 200.

The switch unit 200 includes a first switch contact 202a, which may be electrically connected to an electrical network or a load attached to a first switch contact terminal 204a. Typically, the first switch contact is connected to a first switch contact bar or bus bar 203 to the first switch contact terminal 204a, wherein, in particular, the first switch contact bar 203 includes the first switch contact terminal 204a. Typically, the first switch contact 202a is fixed to a first end of the first switch contact bar 203, and the first switch contact terminal 204 is disposed at a second end of the first switch contact bar 203, opposite to the first end.

Further, the switch unit 200 includes a second switch contact 202b. The second switch contact 202b is moved by a driving unit 206 in a moving direction S, to move the second switch contact 202b from a first position in which the first switch contact 202a is in physical contact with the second switch contact 202b, and a second position in which the first switch contact 202a is separated from the second switch contact 202b. The second position is shown in Fig. 1. The second switch contact 202b may be connected via a second switch contact terminal 204b to an electrical network or the load. The second switch contact 202b is electrically connected to the second switch contact terminal 204b by a flexible conductor 208a and a second switch contact bar 208b, wherein the flexible conductor 208a is connected to a first end of the second switch contact bar 208b. Typically, the second switch contact terminal 204b is disposed at a second end of the second switch contact bar 208b, wherein the second end is opposite to the first end of the second switch contact bar 208b.

Typically, the arc space 109 is disposed above the first and second switch contacts in operation of the circuit breaker, when the circuit breaker is in closed position, i.e. the first switch contact 202a contacts the second switch contact 202b. Further, the stacking direction of the stack of metal plates 102, 106 is substantially parallel to an arc displacement direction A, which is substantially orthogonal to the moving direction S. Typically, the stacking direction or arc displacement direction A corresponds to a direction in which the arc migrates or extends into the arc chute. Typically, the metal plates 104a, 104b, 104n, 108a, 108b, 108n and the connection bar 1 10 are substantially parallel to the moving direction S, and thus to the second axis X.

A first horn 210a is fixed to the first contact 202a to guide a foot of an arc to the metal plates 104a, 104b, ... 104n, in particular to the lowest metal plate 104a, of the first stack 102 of the arc chute 100. Further, the switch unit 200 is provided with the second horn 210b which is disposed such that the arc having a foot at the second switch contact 202b jumps to the horn 210b and moves to the metal plates 108a, 108b, 108n, in particular to the lowest metal plate 108a, of the second stack 106.

In an embodiment, the lowest metal plate 104a of the first stack 102 and the lowest metal plate 108a of the second stack 106 are respectively electrically connected to the first switch contact 202a and the second switch contact 202b. Thus, an arc foot of an arc created by interrupting a current typically do not remain on the first and second horns 210a, 210b and jump to the lowest metal plates 104a, 108a. Once the respective arc foot has jumped to the lowest metal plates, current flows through a respective equipotential connection.

Fig. 1 shows a side view of the circuit breaker in the open state, wherein the first switch contact 202a is separated from the second switch contact 202b. Further, Fig. 1 shows schematically an arc expansion within the arc chute 200 at a nominal current, in particular, the arcs at different moments after the opening of the switch by moving the second switch contact 202b away from the first switch contact 202a.

At a first time tO, after the contact separation of the first switch contact 202a and the second switch contact 202b the arcing begins. Then at time tl, the arc, or one foot of the arc, leaves one of the first or second switch contacts 202a, 202b, and jumps to the horn 210a, 210b of the respective switch contact 202a, 202b. This may either happen first on the fixed, i.e. the first switch contact 202a, or on the moving contact, i.e. the second switch contact 202b. At t2, the arc leaves the second switch contact. Then, the arc feet are located on first horn 210a and the second horn 210b respectively.

Then at time t3, the arc feet jump to the respective level zero, or lowest, metal plates 104a, 108a and the arc continues to climb within the arc chute. Typically, at this stage, several small arcs are generated between respective adjacent metal plates of the first and second stack 102, 104.

At time t4, the arc is well established on the lowest metal plates 104a, 108a of the first and second stack 102, 106 respectively and continues to climb within the arc chute, in particular the arc space 109.

Finally, at time t5 the arc is fully elongated having reached the top of the arc chute, so that the maximum voltage is built or accumulated. The voltage built up by the arc starts building up or accumulating at time tO, increases from time tl to time t4, and reaches its maximum value at approximately time t5. Typically, the sequence may be, for example, influenced by the magnetic field generated by the current, for example for currents greater than 100 A, a chimney effect due to hot gases, for example for currents lower than 100 A, and/or the mechanical behaviour of the circuit breaker, for example the velocity of the second switch contact 202b.

The arc remains present until the current reaches zero, then the arc is naturally extinguished. Typically, the arcing time is proportional to the prospective short circuit current and time constant of the circuit, the current level when opening (magnetic field), the required voltage to be built up for cutting, the contact velocity, for example of the second switch contact, the circuit breaker geometry, which influences, for example, the chimney effect, and/or the material used which influences the gas created in the arc chute or the circuit breaker.

Fig. 2 shows schematically a perspective view of an arc chute according to an embodiment and Fig. 3 shows schematically a top view of a circuit breaker according to an embodiment. The arc chute 100 has an arc chute base 140, which is mounted on the switch unit 200. The base 140 has an opening 143 for the horns of the switch unit 200. Thus, the opening 143 is typically disposed over the first switch contact 202a and the second switch contact 202b. Typically the opening connects the arc chute 100, in particular the arc space 109 of the arc chute 100, with the switching space 226. An arc created between the first switch contact 202a and the second switch contact 202b enters the arc chute 100 through the opening 143.

As shown in Fig. 3, the metal plates have a longitudinal edge 142 extending substantially parallel to the second axis X, and transversal edges 144 being parallel to a third axis Z, being orthogonal to the first axis Y and the second axis X. The metal plates 104, 106 and/or the longitudinal edges 142 typically have a longitudinal extension 1 in the direction of the second axis X. Typically, the longitudinal edges and transversal edges have a ratio between 0.5 and 0.9, for example 2/3. In the embodiment shown in Fig. 3, the longitudinal edge is longer than the transversal edge.

The transversal edge being adjacent to the arc space 109 includes a substantially V-shaped or substantially U-shaped cut-out 145. Typically, the transverse dimension of the cut-out is more than 50% of the dimension of the transversal edge 144 being adjacent to the arc space 109. The cut-out 145 may have an extension in the direction of the longitudinal edge and/or the second axis X of between 10% and 40%, for example between 15% and 30%, of the length of the longitudinal edges 142. In an embodiment, the substantially V-shaped cut-out has two edges enclosing an angle between 60° and 120°.

Typically, more than 70%, in particular more than 90%, of a surface of a metal plate of a stack faces the surface of an adjacent metal plate. That means that the space between adjacent metal plates is substantially free, in particular from a plastic frame or other material that may impede the creation of an arc between the respective adjacent metal plates. In an embodiment, which may be combined with other embodiments disclosed herein, more than 95% of the surface of a metal plate of the stack faces the surface of an adjacent metal plate. Typically, the arc between adjacent metal plates of a stack 102, 106 may not remain at the same place on the surface of a metal plate. They may use the complete space to migrate on the surface of the metal plate of an arc chute. Thus, the metal plates wear in a more uniform manner, such that the distance and the thickness between of the plates may be reduced. Further, cooling of the metal plates is also improved.

In an embodiment, an internal stopper plate 146 is fixed to the sidewall 112 in the arc space 109, in particular to each sidewall 112, to limit the movement of the metal plates 104, 108 in the direction of the arc space 109 over the base opening 143, so that an arc can ascend within the arc chute 100 between the first stack 102 and the second stack 106. In a further embodiment, the stopper plate may be replaced by two parallel rails fixed to the side wall 112. For example, the stopper plate may have a length in the direction of the second axis corresponding to the minimum extension of the arc space in the direction of the first axis. For example, the stopper plate 146 may have an extension in the direction of the second axis of between 75 mm and 150 mm, in particular between 90 mm and 120 mm. Typically, the transversal edges 144 directed toward the arc space 109 abut against the stopper plate 146.

In an embodiment, which may be combined with other embodiments disclosed herein, the arc chute may include a plurality of substantially parallel deflectors 148, shown in Fig. 1, which are inserted into respective grooves in the sidewalls 112. For example, the grooves and the deflectors may be substantially parallel to the plates 104a, 104b, ... 104n, 108a, 108b, ... 108n. Typically, the deflector plates 148 guide the gas created in the arc chute, in a direction parallel to the metal plates out from the arc chute.

Typically, the top wall 150 is fixed to the side walls 112. Hence, the number of components to assemble is substantially reduced.

Thus, the arc chute 100 is light and small due to the reduced clearance distance to a metallic wall of other components, for example, if the circuit breaker is mounted on an electric vehicle, for example a train. The arc chute can be quickly assembled and may be easily scalable, particularly as no plastic mould is needed. Further, the costs are reduced.

Typically, with the arc chute according to embodiments of the present disclosure, the arc does not always burn at the same place, thus the wear is more evenly distributed about the metal plates 104a, 104b, ... 104n, 108a, 108b, ... 108n, such that the distance between the metal plates and also the thickness of the metal plates may be reduced.

As shown in Figures 3 and 4, the hot gases created during the disconnecting of the first switch contact and the second switch contact may substantially exhaust only in two directions 152a, 152b, in particular in parallel to the direction of the second axis X and/or the moving direction S of the second switch contact. Typically, the housing of the arc chute has openings 154a, 154b in the direction of the moving direction S or an axis traversing the two stacks of the arc chute and the arc space 109. In an embodiment, the openings 154a, 154b have a dimension in the direction of the arc displacement direction A or first axis Y of at least 90%, in particular 95%, of the first stack 102 or the second stack 106 of metal plates. Further, the openings 154a, 154b have a dimension orthogonal to the arc displacement direction A and the moving direction S corresponding substantially to the dimension of the metal plates, for example at least 90%, in particular at least 95% of the width of the metal plates. Typically, the width of the metal plates is measured along a third axis orthogonal to the arc displacement direction A and orthogonal to the moving direction S.

The sidewalls 112 of the housing are typically in contact or adjacent to the metal plate of the first stack 102 and the second stack 106. For example the distance between the sidewalls 112 of the housing and the metal plates is less than 5mm, in particular less than 2mm. Hence, further equipment of the rolling stock on which such a circuit breaker may be disposed may be placed close to the circuit breaker, in contrast to circuit breakers in which the gas is exhausted to all sides of the metal plates 104, 108. Thus, the gas is only exhausted in a direction parallel to the moving direction S or the second axis X shown with arrows 152a and 152b.

Fig. 4 shows a perspective view of an embodiment of a circuit breaker including the arc chute 100 and the switch unit 200. As shown in Fig. 4, the arc chute 100 is covered on the side with the sidewalls 112 and on the top with a cover plate 150.

Thus, in an embodiment, the arc chute can be easily assembled, because the sidewalls 112 and the top wall 150 are plate-shaped and fabricated of plastic. Hence, the arc chute is variable, so that he can be easily adapted to the current or the voltage to be switched, for example the number of metal plates to be inserted into the arc chute can be easily adjusted. Further, the sidewalls 112 and the top wall 150 can be easily adapted to suit, and can be easily manufactured by cutting a larger plate to the format required by the arc chute to be produced.

In an embodiment, which may be combined with other embodiments disclosed herein, the switch unit is covered by switch unit sidewalls 250, which are manufactured from plastic plates. Thus, the switch unit 200 may also be easily manufactured.

Typically, for medium-voltage DC circuit breakers, the total arcing time is much longer than for AC circuit breakers. Thus, higher temperatures are created and a plasma may be generated between the first switch contact and the second switch contact and in the arc chute.

The written description uses examples to disclose the invention, including the best mode, and also enables any person skilled in the art to make and use the invention. While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modifications within the spirit and scope of the claims. Especially, mutually nonexclusive features of the embodiments described above may be combined with each other. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are to be within the scope of the claims.

Claims

Arc chute for a DC circuit breaker comprising

at least two parallel stacks (102, 106) of a plurality of substantially parallel metal plates (104, 104a, 104b, 104η, 108, 108a, 108b, 108n) defining a first axis (A) in parallel to a stacking direction, wherein the metal plates of the same stack have a reference distance (Dl) between adjacent metal plates in the direction of the first axis; an arc space (109) defined between the two parallel stacks and adapted to allow an arc to move along the first axis, wherein

a second axis (X) traverses the at least two parallel stacks in parallel to the metal plates and the arc space (109), wherein the second axis is substantially orthogonal to the first axis and

an arc chute housing (111) having at least one top wall limiting the interior of the arc chute housing in the direction of the first axis, wherein

a channel (113a, 113b) is formed between the top wall and the metal plate (104n, 108n) closest to the top wall of the at least one stack (102, 106), the channel having an extension (D3) in the direction of the first axis at least 2 times the reference distance (Dl) enabling a gas flow to force the arc into the arc chute .

Arc chute according to claim 1, wherein

the channel having an extension (D3) in the direction of the first axis of more than 2,5 times, in particular more than 3 times, the reference distance (Dl) and/or

the channel having an extension (D3) in the direction of the first axis of less than 10 times, in particular less than 7 times the reference distance (Dl).

Arc chute according to one of the preceding claims, wherein

the reference distance (Dl) is between about 1 mm and about 8 mm, in particular between 2 mm and about 6 mm.

Arc chute according to one of the preceding claims, wherein

the top wall (150) is substantially parallel to the surface of the plurality of metal plates and/or

the normal of the top wall (150) surface facing the interior of the arc chute is parallel to the first axis (Y).

Arc chute according to one of the preceding claims, wherein

the top wall (150) and/or the channel extends over all stacks (104, 106) of a plurality of substantially parallel metal plates and the arc space (109),

in particular along the second axis (X).

Arc chute for a DC circuit breaker according to claim 5,

having at least one side wall (112) which is substantially parallel to the first axis and/or second axis traversing in parallel to the metal plates the at least one stack and the arc space (109), wherein the distance between the at least one sidewall (112) and the metal plates is less than 10mm, in particular less than 5mm.

Arc chute according to claim 6, wherein

the two parallel stacks include a first stack and a second stack, wherein

a distance (D3) between the metal plate of the first stack to the closest metal plate of the second stack is between 0,75 times and 2 times, in particular between 0,8 times and 1,5 times, the length (1) of the extension of the metal plates in direction of the second axis and/or the length (1) of the longitudinal edge of the metal plates.

Arc chute according to one of the preceding claims, wherein

the metal plates (104, 108) of the stacks of metal plates are substantially rectangular and have, in particular, a substantially V-shaped or U-shaped cut-out (145) directed towards the arc space (109), wherein a second axis is substantially parallel to two longitudinal edges of the metal plates extending adjacent to the sidewalls (112).

Arc chute according to one of the preceding claims, wherein

the housing of the arc chute has at least one opening arranged such that gas may traverse the opening in the direction of the second axis traversing in parallel to the metal plates the at least two stacks and the arc space (109), wherein

, the at least one opening has an opening surface parallel to a plane spanned by the first axis and the third axis, the third axis being orthogonal to the first axis and the second axis.

Circuit breaker comprising

a switch unit (200) having a first switch contact (202a) and a second switch contact (202b), wherein the second switch contact is movable between a first position, wherein the first switch contact contacts the second switch contact, and a second position in which the first and second switch contacts (202a, 202b) are separated from each other; and

an arc chute (100) according to one of the preceding claims.

11. Circuit breaker according to claim 10, wherein

the second switch contact (202b) is movable substantially along a moving direction (S), wherein the second axis is substantially parallel to the moving direction (S).

12. Circuit breaker according to one of the claims 10 or 11, wherein

the circuit breaker does not comprise a device for generating an electric and/or magnetic field for forcing an arc into the arc chute.

13. Method for assembling an arc chute of a circuit breaker, the arc chute comprising an arc space (109), said method comprising

stacking of a plurality of substantially parallel metal plates (104, 104a, 104b, 104n, 108, 108a, 108b, 108n) parallel to a first axis (A), assembling of two parallel stacks (102, 106) such a second axis (X) traverses the at least two parallel stacks in parallel to the metal plates and the arc space (109), wherein the second axis is substantially orthogonal to the first axis, wherein the arc space is adapted to allow an arc to extend along the first axis and between the two parallel stacks, wherein the metal plates of the same stack have a reference distance between adjacent metal plates in the direction of the first axis; and

mounting at least one top wall of an arc chute housing (111), the top wall limiting the interior of the arc chute housing in the direction of the first axis, such that a channel is formed between the top wall (150) and the closest metal plate (104n, 108n) of the at least one stack to the top wall, wherein

the channel has an extension (D3) in the direction of the first axis (Y) of at least 2 times the reference distance.

14. Method according to claim 13, further comprising

mounting the arc chute (100) on a switching unit (200).