EP2447969A1

EP2447969A1 - Switching device for low voltage electrical circuits

Info

Publication number: EP2447969A1
Application number: EP11184462A
Authority: EP
Inventors: Paolo Faure
Original assignee: ABB SpA
Current assignee: ABB SpA
Priority date: 2010-10-28
Filing date: 2011-10-10
Publication date: 2012-05-02
Anticipated expiration: 2031-10-10
Also published as: ES2437931T3; EP2447969B1; DK2447969T3; ITBG20100056A1

Abstract

A switching device for low voltage electrical circuits comprising at least one pole having an arc chute (50, 51, 100), a stationary contact (2, 6) and a corresponding moving contact (3, 7) that can be operated by a contact shaft (4) in such a manner as to move between a first position in which it is engaged with the stationary contact (2, 6) and a second position in which it is spatially distanced from the stationary contact (2, 6).

The switching device comprises at least one moving device, operatively connected to and operated by said contact shaft (4) in such a manner that at least one element of the moving device moves towards the space that is created between the moving contact (3, 7) and the stationary contact (2, 6) when the moving contact (4) moves from the first position thereof towards second position thereof.

Description

The present invention relates to an electrical switching device for low voltage circuits having improved characteristics and functions for extinguishing the electric arcs generated in its poles.
As it is known, switching devices for low voltage circuits (i.e. for applications with operating voltages up to 1000V AC / 1500V DC), such as automatic circuit breakers, disconnectors, contactors, limiters, universally known as switching devices, are devices designed to allow correct operation of specific parts of electrical circuits and of the loads operatively associated therewith, acting, for example, when faults, such as overloads or short circuits, occur.
These switching devices comprise an enclosure containing one or more electrical poles, each of which comprises at least one pair of mutually engageable/disengageable contacts. An appropriate control mechanism causes the relative movement of the pairs of contacts so that they can adopt an engaged position (circuit breaker closed) and a separated position (circuit breaker open).
The phase to open the circuit breaker to interrupt an overcurrent (i.e. a current greater than the rated operating value), for example caused by an overload or short circuit, is particularly critical. In fact, when the contacts separate, an electric arc is created therebetween and the current continues to flow through this into the contacts, which can cause damage both to parts of the circuit breaker and to parts of the electrical circuit associated therewith. For this reason various measures have been adopted to extinguish the electric arc in the fastest and most efficient manner possible.
Generally, an arc chute, in which engagement and separation of the contacts occurs, is associated with each pole of the circuit breaker. The arc chute can comprise an assembly of arc-breaking blades adapted to divide the arc into different parts, accelerating the extinction thereof, and can comprise guide means adapted to guide the electric arc towards the arc-breaking blades.
Another solution provides for the use of gas media and/or materials which, when the electric arc reaches a certain temperature, release substances that help to extinguish the arc.
A further solution provides for the use of ferromagnetic elements that attract the moving contacts towards a position separated from the stationary contacts through electromagnetism. The gas media and the ferromagnetic elements can be arranged in proximity to or inside the arc chutes.
Although the solutions described perform the function for which they are designed, the state of the art leaves space for further improvements able to increase the speed and effectiveness with which electric arcs are extinguished.
The object of the present invention is to provide a switching device with improved capacity to extinguish electric arcs. This object is achieved by a switching device for low voltage electrical circuits comprising at least one pole having an arc chute, a stationary contact and a corresponding moving contact that can be operated by a contact shaft in such a manner as to move between a first position in which it is engaged with the stationary contact and a second position in which it is spatially distanced from the stationary contact. The switching device comprises at least one moving device operatively connected to and operated by said contact shaft in such a manner that at least one element of the moving device moves towards the space that is created between the moving contact and the stationary contact when the moving contact moves from the first position towards the second position.
The switching device according to the present invention will be described hereunder with particular reference to an embodiment thereof as "Miniature Circuit Breaker" (or MCB), or as "molded case circuit breaker" (or MCCB). However, the principles and the technical solutions set forth in the description below must also be considered valid for different embodiments of switching devices for single pole or multi-pole low voltage circuits, such as disconnectors, contactors or limiters.
The characteristics and advantages will be more apparent from the description of preferred, but non-exclusive, embodiments of the present invention, illustrated by way of example in the accompanying drawings, wherein:

Fig. 1 shows a first arc chute and a second arc chute connected to the contact shaft of a circuit breaker in closed configuration, according to a first embodiment;
Fig. 2 shows the first arc chute and the second arc chute of Fig. 1 at the end of the circuit breaker opening phase;
Fig. 3 shows a first arc chute and a second arc chute connected to the contact shaft of a circuit breaker in closed configuration, according to a second embodiment;
Fig. 4 shows the first arc chute and the second arc chute of Fig. 3 at the end of the circuit breaker opening phase;
Fig. 5 shows a further example of arc chute that can be used in a circuit breaker.

For the sake of simplicity, in the course of the description the same numerical references will be used to indicate the same or equivalent elements belonging to the different embodiments illustrated.
A circuit breaker according to the present invention comprises at least one pole having an arc chute, a stationary contact and a corresponding moving contact that can be operated by a contact shaft in such a manner as to move between a first position in which it is engaged with the stationary contact and a second position in which it is spatially distanced from the stationary contact. This circuit breaker comprises at least one moving device, operatively connected to and operated by the contact shaft in such a manner that at least one element of the moving device moves towards the space that is created between the moving contact and the stationary contact when the moving contact moves from the first position towards the second position.
Preferably, the element of the moving device that moves towards the space that is created between the moving contact and the stationary contact comprises at least one portion of the arc chute; in particular, this element can comprise at least one arc-breaking blade or a group of arc-breaking blades of the arc chute.
The term "arc chute" must be intended generally as a structure that defines a space particularly suitable to help to extinguish the electric arc, regardless of the particular examples of arc chute illustrated in the figures to which reference will be made in the continuation of the description.
With reference to Figs. 1-2 and to Figs. 3-4, these show a first preferred solution and a second preferred solution, respectively, particularly suitable to be used in a Miniature Circuit Breaker, without wishing to limit their application in different types of circuit breakers.
The aforesaid figures show a first pole of a circuit breaker having a first stationary contact 2 and a corresponding first moving contact 3 pivoted on a contact shaft 4; following rotation of the contact shaft 4 about its rotation axis 8, the first moving contact 3 moves between a first position (shown in Figs. 1 and 3), or engaged position (circuit breaker closed), and a second position (shown in Figs. 2 and 4), or separated position (circuit breaker open), in which it is spatially distanced from the first stationary contact 2. Rotation of the contact shaft 4 is controlled by an actuation mechanism operated manually (typically using a lever projecting from the enclosure of the circuit breaker) or through the action of one or more protection devices adapted to detect fault conditions, such as the occurrence of overcurrents.
The moving device of the circuit breaker comprises a first arc chute 50 associated with the first pole and mounted movably inside the circuit breaker. The moving device is operatively connected to and operated by the contact shaft 4 in such a manner that the first arc chute 50 moves towards the space that is created between the first moving contact 3 and the first stationary contact 2 when the first moving contact moves from the engaged position to the separated position.
The first arc chute 50 shown in the figures comprises a pair of lateral walls 52 made of electrically insulating material and connected transversely by a rear wall 53 facing a front opening defined for passage of the first moving contact 3 inside the first arc chute 50. The first arc chute 50 comprises an assembly of substantially U-shaped arc-breaking blades 54 positioned between the pairs of lateral walls 52 and are fastened thereto by means of appropriate coupling means. In particular, the lateral edges of the arc-breaking blades 54 each comprise two projections 300 adapted to couple with respective openings 301 defined on the lateral walls 52. Alternatively, a plurality of guides (like the guides 107 of the arc chute 100 shown in Fig. 5) adapted to each receive a corresponding arc-breaking blade 54, can be defined along the lateral walls 52.
Preferably, the assembly of arc-breaking blades 54 comprises at least a first group of arc-breaking blades 200 in which the arc-breaking blades 54 are adapted to be inserted in the space that is created between the first moving contact 3 and the first stationary contact 2 when the moving contact 3 moves from the engaged position towards the separated position. Insertion into said space takes place following movement of the whole first arc chute 50 which is caused by rotation of the contact shaft 4 during the circuit breaker opening phase.
In the examples illustrated, the arc-breaking blades 54 of the first group of arc-breaking blades 200 are arranged in such a manner as to be inserted in succession into the space that is created between the first moving contact 3 and the first stationary contact 2; in particular, these arc-breaking blades 54 are arranged staggered with respect to one another. Alternatively, the assembly of arc-breaking blades 54 could comprise at least one group of arc-breaking blades 54 that are mutually aligned and are inserted simultaneously into the space that is created between the first moving contact 3 and the first stationary contact 2. The assembly of arc-breaking blades 54 shown in Figs. 1-4 also comprises a second group of arc-breaking blades 201, superimposed on the first group of arc-breaking blades 200, in which the arc-breaking blades 54 are adapted to move towards the space that is created between the first moving contact 3 and the first stationary contact 2 when the first moving contact 3 moves from the engaged position towards the separated position. The arc-breaking blades 54 of the second group of arc-breaking blades 201 are arranged in such a manner that they do not intercept the first moving contact 3 during its movement from the engaged position to the separated position.
In the examples illustrated it can be seen how the arc-breaking blades 54 of the second group of arc-breaking blades 201 are staggered with respect to one another and to the arc-breaking blades 54 of the first group of arc-breaking blades 200. In particular, the arc-breaking blades 54 of both groups of arc-breaking blades 200, 201 are arranged staggered with respect to one another in such a manner that their distance from the rear wall 43 decreases as their distance from the first stationary contact 2 increases.
Alternatively to what has been described, the assembly of arc-breaking blades 54 can be constituted entirely by arc-breaking blades 54 mutually aligned and simply made to move towards the space that is created between the first moving contact 3 and the first stationary contact 2, following movement of the first arc chute 50 caused by rotation of the contact shaft 4.
In the solutions illustrated in Figs. 1-4, the moving device comprises a connection element (see the connection element 55 in Figs. 1-2, the connection element 65 in Figs. 3-4) adapted to cause movement of the first arc chute 50 following rotation of the contact shaft 4. The connection element 55 and the connection element 65 both comprise a first end 56, 66 connected directly to the first arc chute 50, and a second end 57, 67 connected directly to the contact shaft 4. Alternatively, the connection element could be connected indirectly to the contact shaft 4 and/or to the first arc chute 50 through the interposition of further elements. In the solution shown in Figs. 1 and 2, the connection element 55 extends longitudinally between its first end 56 and its second end 57 along a principal axis X. The second end 57 comprises a portion 58 that extends towards the contact shaft 4 transversely with respect to the principal axis X. An opening 59 is defined along the portion 58 and is operatively coupled with a pin 60 that extends from the contact shaft 4 towards the opening 59; in the embodiment illustrated, the contact shaft 4 has a cam surface 61 from which the pin 60 extends transversely. The opening 59 is defined by two lateral edges 62 connected by an upper edge 63 and by a lower edge 64.
In the solution shown in Figs. 3 and 4, the connection element 65 extends longitudinally between its first end 66 and its second end 67 along a principal axis Y. A first set of teeth 68, adapted to couple operatively with a second set of teeth 69 defined on the contact shaft 4, is defined on the second end 67.
In a further solution, not shown in the figures, the connection element can comprise at least one connecting rod with a first end connected (directly or indirectly) to the contact shaft 4 and a second end connected (directly or indirectly) to the first arc chute 50.
In the examples of Figs. 1-4, the circuit breaker comprises a second pole with a second stationary contact 6 and a corresponding second moving contact 7 pivoted on the contact shaft 4 in such a manner as to engage with/separate from the second stationary contact 6 following rotation of the contact shaft 4 about its rotation axis 8.
The second pole comprises a second arc chute 51 mounted movably inside the circuit breaker. The structure of the second arc chute 51 is identical to that of the first arc chute 50, and therefore the same elements constituting the two arc chutes 50, 51 are indicated with the same numeric references.
The first end 56 of the connection element 55 and the first end 66 of the connection element 65 are mechanically coupled also to the second arc chute 51. In this manner, a single moving device is configured, comprising: the first arc chute 50, the second arc chute 51 and the connection element 55 (in the solution shown in Figs. 1-2) or the connection element 65 (in the solution shown in Figs. 3-4).
Alternatively, it would be possible to use a first moving device associated with the first pole (comprising the first arc chute 50 and a first connection element equivalent to the connection element 55 or 65) and a second moving device associated with the second pole (comprising the second arc chute 51 and a second connection element equivalent to the connection element 55 or 65). A similar solution could be adopted, for example, also in a molded case circuit breaker, in which arc chutes like the first arc chute 50 are used in each pole of the circuit breaker.
In a further solution, not shown in the figures, the connection element used can comprise a first connecting rod, connected to the contact shaft 4 and to the first arc chute 50, and a second connecting rod, connected to the contact shaft 4 and to the second arc chute 51.
The situation of circuit breaker in closed configuration shown in Figs. 1 and 3 is considered. When an overcurrent occurs the protective devices of the circuit breaker act on the control mechanism causing a rotation of the contact shaft 4 about the rotation axis 8; rotation of the contact shaft is such as to reach the open configuration of the circuit breaker shown in Figs. 2 and 4.
With reference to the solution shown in Figs. 1-2, the pin 60 is initially in contact with the lower edge 64 of the opening 59 when the circuit breaker is in closed configuration. During rotation of the contact shaft 4 the pin 60 slides along the lateral edges 62 until reaching the upper edge 63 at the end of the circuit breaker opening phase. Sliding along the lateral edges 62, the pin 60 exerts a force on the connection element 55 such as to cause movement thereof along the axis X, towards the contact shaft 4. Consequently, also the first arc chute 50 (and the second arc chute 51, when present) moves internally towards the contact shaft 4 along the direction of movement defined by the axis X, from the position shown in Fig. 1 to the position shown in Fig. 2.
With reference to the solution shown in Figs. 3-4, during rotation of the contact shaft 4 the first set of teeth 68 and the second set of teeth 69 mesh with one another in such as manner as to convert the rotational motion of the contact shaft 4 into a linear movement of the connection element 55 along the principal axis Y, towards the contact shaft 4. Consequently, also the first arc chute 50 (and the second arc chute 51, when present) is moved internally towards the contact shaft 4 along the direction of movement defined by the axis Y, from the position shown in Fig. 3 to the position shown in Fig. 4.
From Figs. 1-4 it is apparent how the movement of the first arc chute 50 towards the contact shaft 4 is a movement towards the space that is created between the first moving contact 3 and the first stationary contact 2 during the circuit breaker opening phase. During this movement of the first arc chute 50, the arc-breaking blades 54 of the first group of arc-breaking blades 200 are inserted in succession into the space that is created between the first moving contact 3 and the first stationary contact 2. In the examples of embodiments illustrated in Figs. 1-4, movement of the first arc chute 50 is calibrated in such a manner that a first arc-breaking blade 54 (the one nearest to the first stationary contact 2) is inserted between the first moving contact 3 and the first stationary contact 2 when sufficient space is created therebetween to receive it. Subsequently, a second arc-breaking blade 54, superimposed on the first arc-breaking blade 54, is inserted between the first moving contact 3 and the first stationary contact 2 when the space therebetween has increased sufficiently to receive it.
The first group of arc-breaking blades 200 could comprise a different number of arc-breaking blades 54 with respect to the examples illustrated.
Again during movement of the first arc chute 50 towards the contact shaft 4, the second group of arc-breaking blades 201 moves towards the space that is created between the first moving contact 3 and the first stationary contact 2 without intercepting the moving contact during its movement from the engaged position illustrated in Figs. 1 and 3 towards the separated position illustrated in Figs. 2 and 4.
The same applies for the first group 200 and for the second group 201 of arc-breaking blades 54 of the second arc chute 52.
In the preferred solutions described with reference to Figs. 1-4, the element of the moving device that moves towards the space that is created between the first moving contact 3 and the first stationary contact 2 is constituted by the whole of the first arc chute 50 mounted movably inside the circuit breaker.
In an alternative solution, the circuit breaker according to the present invention comprises a moving device in which the element that moves towards the space that is created between the moving contact and the stationary contact of a pole is constituted by one or more moving parts of the arc chute associated with this pole. Preferably, the moving part of the arc chute comprises at least one arc-breaking blade coupled in a movable manner with the enclosure of the arc chute.
Fig. 5 shows an arc chute 100 comprising an enclosure 101 produced with insulating material and defined by a pair of lateral walls 102, a lower wall 103, an upper wall 104 and, finally, a rear wall 105. The enclosure 101 is open at the front part thereof to allow sliding insertion of an assembly of arc-breaking blades 106 into corresponding guides 107 defined along the lateral walls 102. In this manner, the arc-breaking blades 106 are coupled in a movable manner with the enclosure 101. Arc chutes designed in this manner are particularly suitable to be used in the poles of molded case circuit breakers, without however limiting their application in other types of switches.
The situation of circuit breaker having a pole with an arc chute 100 is considered, in which the moving device comprises at least one arc-breaking blade 106 and is operatively connected to and operated by the contact shaft of the circuit breaker in such a manner that this arc-breaking blade 106 moves towards the space that is created between the moving contact and the stationary contact of the pole when these separate from each other, sliding along its guide 107. The moving device can comprise, for example, connection elements similar to the connections elements 55 and 65 described previously, in which one end thereof is connected directly or indirectly to the contact shaft of the circuit breaker, and another end thereof is connected directly or indirectly to one or more arc-breaking blades 106. Alternatively, it would be possible to use at least one connecting rod, connected directly or indirectly to the contact shaft and to one or more arc-breaking blades 106.
In the arc chute 100 shown in Fig. 5, the arc-breaking blades 106 are aligned with one another. The moving device can comprise at least a first group of arc-breaking blades 106 which together slide towards the space that is created between the stationary contact and the moving contact when these separate, until being inserted simultaneously into this space. Alternatively, the whole assembly of the arc-breaking blades 106 can simply be moved towards the space that is created between the moving contact and the stationary contact when these separate.
According to another solution, the assembly of arc-breaking blades 106 of the arc chute 100 can comprise at least one group of arc-breaking blades 106 arranged in such a manner as to be inserted in succession into the space that is created between the moving contact and the stationary contact when these separate. In particular, the arc-breaking blades 106 can be arranged staggered from one another in the same manner as the arc-breaking blades 54 shown in Figs. 1-4.
Alternatively to the description above, the moving device of the circuit breaker according to the present invention may also not comprise arc chutes mounted movably inside the circuit breaker or moving portions of arc chutes. An element, for example configured as arc-breaking element and/or comprising a gas medium, could be mounted directly on the contact shaft of the circuit breaker (or connected indirectly to the contact shaft), and be structured in such a manner as to be inserted in the space that is created between the contacts of the switch when these separate.
It must be stressed that the principles of the solutions described above can also be applied to double break circuit breakers (in particular molded case circuit breakers), in which each pole comprises at least one moving contact with a central body from which a first arm and a second arm extend on opposite sides with respect to the rotation axis of the central body. The first arm and the second arm are adapted to move between a first position in which they are engaged with a first stationary contact and a second stationary contact, respectively, and a second position in which they are spatially distanced from the respective first and second stationary contacts.
For example, the moving device of the double break circuit breaker can comprise at least a first arc chute and a second arc chute (structurally similar to the first arc chute 50 of the solutions illustrated in Figs. 1-4) mounted movably inside the circuit breaker. The moving device is operatively connected to and operated by the contact shaft of the circuit breaker in such a manner that the first arc chute moves towards the space that is created between the first arm and the first stationary contact, and in such a manner that the second arc chute moves towards the space that is created between the second arm and the second stationary contact. The first and the second arc chute can be connected to the contact shaft through connection elements equivalent to the connection element 55 of Figs. 1-2, or to the connection element 65 of Figs. 3-4. For example, a first set of teeth and a second set of teeth can be defined on opposite parts of the contact shaft with respect to the rotation axis of this contact shaft. The first set of teeth and the second set of teeth are adapted to mesh with respective sets of teeth defined on the connection elements connected to the first arc chute and to the second arc chute, respectively, In a further example, the first arc chute and the second arc chute can be connected to the contact shaft through a connecting rod. Alternatively, the moving device of the double break circuit breaker can comprise a first arc chute and a second arc chute structurally similar to the arc chute 100 shown in Fig. 5. In this solution the moving device is operatively connected to and operated by the contact shaft of the circuit breaker in such a manner that at least one arc-breaking blade of the first arc chute moves towards the space that is created between the first arm and the first stationary contact, and in such a manner that at least a first arc-breaking blade of the second arc chute moves towards the space that is created between the second arm and the second stationary contact. The arc-breaking blades of the first arc chute and of the second arc chute that are included in the moving device can be connected to the contact shaft through connection elements equivalent to the connection element 55 of Figs. 1-2 or to the connection element 65 of Figs. 3-4, or through at least one connecting rod.
In practice, it has been seen how a circuit breaker according to the present invention fully achieves the intended aim. By moving an element of the moving device towards the space that is created between the contacts of the circuit breaker when these separate, extinguishing of the electric arc can start sooner compared to the time required by prior art solutions.
For example, the described movement of the first arc chute 50 (and of the second arc chute 51, where present) allows the assembly of the arc-breaking blades 54 to start to split up the electric arc after a shorter time with respect to the situation in which the first arc chute 50 does not move. Moreover, the first arc chute 50 could comprise gas media which act to extinguish the electric arc in shorter times.
Also in a circuit breaker using the arc chute 100 in Fig. 5, the arc-breaking blades 106 that are made to slide along their guides 107 act to split up the electric arc in shorter times with respect to the situation in which they remain stationary.
At least one part of the moving device can advantageously be inserted in the space that is created between the contacts of the circuit breaker when these separate, in such a manner as to improve the effectiveness with which the electric arc is extinguished. For example, the first group of arc-breaking blades 200 of the first arc chute 50 is inserted in the space that is created between the first moving contact 3 and the first stationary contact 2. Advantageously, the arc-breaking blades 54 of the first group of arc-breaking blades 200 are arranged in such a manner as to be inserted in succession between the first moving contact 3 and the first stationary contact 2; in this manner, an arc-breaking blade 54 is inserted between the first moving contact 3 and the first stationary contact 2 as soon as the space between them is large enough to contain it. Due to this solution, the time and the effectiveness of electric arc extinguishing are improved. In fact, each time an electric arc is intersected by an arc-breaking blade, there is an increase in the level of electrical voltage and power required for it to continue to exist. The sooner this intersection takes place the sooner extinction of the arc begins, reducing the level of energy transiting inside the circuit breaker damaging it.
Finally, it must be stressed that in all the solutions described, the moving device is advantageously operatively connected to and operated by the contact shaft of the circuit breaker. In fact, by connecting the moving device directly to other elements, for example to the moving contacts of the switch, a load would be applied thereto which could cause damage or malfunction thereof; for example, the moving device connected directly to the moving contacts would slow down their movement, which instead must be as fast and free as possible in the circuit breaker opening phase.
The solutions described are susceptible to numerous modifications and variants, all falling within the scope of the present invention. For example, switches could be provided with guide means, adapted to guide the entire arc chute, or at least one moving portion of the arc chute, towards the space that is created between the contacts during their separation. Moreover, the rear wall 53 of the first arc chute 50 (and of the second arc chute 51) could be omitted.
Finally, all the details and the elements described can be substituted by other technically equivalent elements. In practice, the dimensions, the shape and the type of materials of the elements described can be any, according to requirements and to the state of the art.

Claims

A switching device for low voltage electrical circuits comprising at least one pole having an arc chute (50, 51, 100), a stationary contact (2, 6) and a corresponding moving contact (3, 7) that can be operated by a contact shaft (4) in such a manner as to move between a first position in which it is engaged with the stationary contact (2, 6) and a second position in which it is spatially distanced from the stationary contact (2, 6), characterized in that it comprises at least one moving device, operatively connected to and operated by said contact shaft (4) in such a manner that at least one element of said moving device moves towards the space that is created between said moving contact (3, 7) and said stationary contact (2, 6) when the moving contact (3, 7) moves from said first position towards said second position.
The switching device according to claim 1, characterized in that said element of the moving device comprises at least one portion of the arc chute (50, 51, 100).
The switching device according to claim 2, characterized in that said at least one portion of the arc chute (50, 51, 100) comprises at least one arc-breaking blade (54, 106).
The switching device according to claim 3, characterized in that said at least one portion of the arc chute (50, 51, 100) comprises at least a first group of arc-breaking blades (200).
The switching device according to claim 4, characterized in that said the arc-breaking blades (106) of said first group of arc-breaking blades (200) are inserted simultaneously into said space.
The switching device according to claim 4, characterized in that the arc-breaking blades (54) of said first group of arc-breaking blades (200) are arranged in such a manner as to be inserted in succession into said space.
The switching device according to claim 6, characterized in that the arc-breaking blades (54) of said first group of arc-breaking blades (200) are arranged staggered with respect to one another.
The switching device according to claim 6 or 7, characterized in that said at least one portion of the arc chute (50, 51) comprises a second group of arc-breaking blades (201) which are adapted to move towards said space and which are arranged in such a manner that they do not intercept the moving contact (3, 7) during its movement from said first position towards said second position.
The switching device according to claim 8, characterized in that the arc-breaking blades (54) of the second group of arc-breaking blades (201) are staggered with respect to one another and to the arc-breaking blades (54) of the first group of arc-breaking blades (200).
The switching device according to one or more of the preceding claims, characterized in that said element of the moving device is formed by said arc chute (50, 51) mounted movably in said switching device.
The switching device according to one or more of the preceding claims, characterized in that said moving device comprises a connection element (55, 65) having a first end (56, 66) connected directly or indirectly to said at least one portion of the arc chute (50, 51) and having a second end (57, 67) connected directly or indirectly to said contact shaft (4).
The switching device according to claim 11, characterized in that on said second end (57) of the connection element (55) there is defined an opening (59) operatively engaged with a pin (60) which extends from said contact shaft (4) towards said opening (59).
The switching device according to claim 12, characterized in that said contact shaft (4) comprises a cam surface (61) from which said pin (60) extends transversely.
The switching device according to claim 11, characterized in that said second end (67) of the connection element (65) comprises a first set of teeth (68) adapted to engage operatively with a second set of teeth (69) defined on said contact shaft (4).
The switching device according to claim 11, characterized in that said connection element comprises at least one connecting rod.