FR2828329A1 - DEVICE FOR EXTINGUISHING AN ELECTRIC ARC - Google Patents

Abstract

Device (19) for extinguishing an electric arc (17) established in a zone (18) known as the formation of the arc (17) between a fixed contact (7) and a movable contact (8) of a protection device such as a circuit breaker, this device (19) comprising: - an interrupting chamber (20), - two opposite conductors (22, 23) adapted to guide the arc (17) from its formation zone ( 18) towards the interrupting chamber (20) and each having an anterior portion (24, 26) delimiting a prechamber (28), extended by a posterior portion (25, 27) which borders the interrupting chamber (20). 'invention, the conductor (22) carrying the fixed contact (7) is formed of two separate conductive parts (30, 31) which overlap and are in simple mechanical contact, namely a first part (30) forming the front portion ( 24) of said conductor (22), and a second part (31) forming its rear portion (25).

Description

are supplied to said decoding circuit.

  The invention relates to a device for extinguishing an electric arc for

  a protective device such as a circuit breaker.

  Such an electric arc is established in a formation zone between a fixed contact and a movable contact of the device. To extinguish the arc, such a device usually comprises: - a breaking chamber located at a distance from said formation zone and formed of a plurality of superimposed conductive plates, - two opposite conductors, one of which carries the fixed contact, adapted to guide the arc from its formation zone towards the breaking chamber and each having for this purpose an anterior portion delimiting a so-called prechamber space situated between the formation zone of the arc and the breaking chamber, this anterior portion being extended by a

  posterior portion which borders the breaking chamber.

  To illustrate this type of device, reference may be made to the request for

  French patent published under number FR-A-2 598 028.

  Although generally satisfactory, the invention aims to improve a

  such a device, in particular by increasing its breaking capacity.

  To this end, the invention proposes, according to a first aspect, a device for extinguishing an electric arc established in a zone known as the formation of the arc between a fixed contact and a movable contact of a protective device such than a circuit breaker, this device comprising: a breaking chamber located at a distance from said formation zone and formed of a plurality of superimposed conductive plates, - two opposite conductors, one of which carries the fixed contact, adapted to guide 1 arc from its formation zone towards the interrupting chamber and each having for this purpose an anterior portion delimiting a space known as a prechamber situated between the arc formation zone and the interrupting chamber, this anterior portion being extended by a portion posterior which borders the breaking chamber; the conductor carrying the fixed contact being formed of two separate conductive parts which overlap and are in simple mechanical contact, namely a first part forming the front portion of the conductor, and a second

  piece forming its posterior portion.

  In this way, the electrical contact between the two conductive parts is imperfect. This results in the appearance between them of an electrical resistance which, causing the increase in the arc voltage, causes the reduction in the breaking intensity. The breaking capacity of the device is thereby significantly improved. According to one embodiment, the first conductive part is made of copper, the second conductive part preferably being made of a ferromagnetic material, for example steel, while the fixed contact is in particular in the form of a silvery disc. This results in a

  better conduction of the electric arc.

  Furthermore, according to other preferential but non-limiting characteristics: - the conductive parts overlap in the prechamber at the limit of the interrupting chamber; - The second conductive part is nested in the first; - The first conductive part carries the fixed contact; - the conductive parts are in mechanical contact at least at the level of the fixed contact; - The fixed contact being in relief with respect to the first conductive part and having a contact face against which is able to come to apply LED it movable contact, the first conductive part carries a ramp connecting substantially said said face

  contact and the outer surface of the first conductive part.

  The invention also proposes, according to a second aspect, a circuit breaker

  limiter comprising a device as previously described.

  According to one embodiment, this circuit breaker comprises an electromagnet adapted to control the separation of the fixed and movable contacts, said electromagnet comprising a coil electrically connected at the end, on the one hand, to a contact terminal of the circuit breaker and, on the other hand , to the first conductive part. Other characteristics and advantages of the invention will become apparent from the

  light of the following description of an embodiment given as

  non-limiting example, description made with reference to the accompanying drawings in

  which: - Figure 1 is a cutaway elevation view of a limiter circuit breaker according to the invention, in an engaged configuration o its fixed and movable contacts are in electrical contact; - Figure 2 is a view similar to Figure 1, the circuit breaker being here shown in a tripped configuration in which the movable contact is spaced from the fixed contact; - Figure 3 is a view of a detail of Figure 2, illustrating the device

according to the invention.

  In Figures 1 and 2 is shown a limiting circuit breaker 1 comprising a housing 2 in which is housed a control device 3 for opening a

  electrical circuit 4 connecting an input terminal 5 to an output terminal 6.

  The circuit breaker 1 comprises a fixed contact 7 electrically connected to the input terminal 5, as well as a mobile contact 8 electrically connected to the output terminal 6. The mobile contact 8 is here produced in the form of a pivoting metal lever ; it is adapted to occupy, on the one hand, in a so-called closed configuration of the circuit breaker 1, illustrated in FIG. 1, a so-called fermoe position in which it is applied against the fixed contact 7 by establishing an electrical contact with it and , on the other hand, in a so-called tripped configuration of the circuit breaker 1, illustrated in FIG. 2, a so-called open position in which it

located away from fixed contact 7.

  The control device 3 comprises an electromagnet 9 consisting of a coil 10 electrically connected at the end on the one hand, to the input terminal 5 and on the other hand, to the fixed contact 7, and of a ferromagnetic core 11 introduced in

  the spiral winding of the coil 10.

  The core 11 is mounted movable in translation along the main axis of the winding of the coil 1O, and it is adapted to move, under the effect of an overcurrent of the current flowing in the coil 10, from an inactive position towards an active position in which, by pushing at one of its ends a trigger 12 which, in the engaged configuration, maintains the movable contact 8 in the closed position against a return spring 13, causes the displacement of the contact mobile 8 to its open position to open the circuit

  electric 4 and trip the circuit breaker 1.

  In order to subsequently restore the movable contact 8 in its closed position and thus switch on the circuit breaker 1 again by closing the electrical circuit 4, there is provided a reset mechanism 14 comprising a lever 15 available to the user and whose movement after tripping of circuit breaker 1, is able, by means of a set of levers 16, to restore contact

mobile 8 in closed position.

  When the movable contact 8 is opened, an electric arc 17 is established between it and the fixed contact 7 in a zone 18 known as the formation of the arc 17, located at the right of the parts of the fixed contact 7 and of the movable contact 8 opposite. The circuit breaker 1 further comprises a device 19 for extinguishing the arc 17, which comprises a breaking chamber 20 located at a distance from the formation zone 18 and formed of a plurality of superimposed conductive plates 21, as well as two opposite conductors commonly called horns, namely an upstream horn 22 and a downstream horn 23, these horns 22, 23 being adapted to guide the arc 17 from the formation zone 18 towards the chamber

cutoff 20 o it is off.

  The upstream horn 22, which is electrically connected to the input terminal 5 while being connected to the coil 10, carries the fixed contact 7, while the downstream horn

  23 is electrically connected to the output terminal 6.

  To guide the arc 17, each horn 22, 23 has an anterior portion 24, 26 delimiting a space called the prechamber 28, situated between the formation zone 18 of the arc 17 and the breaking chamber 20, each anterior portion 24, 26 being extended by a rear portion 25, 27 which borders the chamber

20.

  As can be seen, seen in FIGS. 1 to 3, the anterior portions 24, 26 of the horns 22, 23 are first of all convergent from the formation zone 18 of the arch 17 to an intermediate zone 29 located in prechamber 28, then

  divergent from this intermediate zone 29 towards the breaking chamber 20.

  The very principle of the extinction of Arc 17 has been known for a long time, and our purpose is not to describe it in detail. It will however be recalled that, when it reaches the breaking chamber 20, the electric arc 17 is separated into a plurality of secondary arcs by the conductive plates 21 before being extinguished, and that the voltage of the arc 17, denoted UarC 'checks the following law: Uarc = Uo + [3 Larc o UO is the voltage of the arc 17 in the formation zone 18, generally between 20 and 25 volts, LarC is the length of the arc 17, that is to say the distance separating the horns 22, 23 in line with the arc 17, generally measured

  in millimeters, and a multiplying coefficient approximately equal to 1.5 V / mm.

  According to the invention, in particular in order to increase the breaking capacity of the circuit breaker 1, the upstream horn 22 is formed from two separate conductive parts, namely a first part 30 which forms the front portion 24 of the horn 22, and a second part 31 which forms its rear portion 25. These two conductive parts 30, 31 overlap in the prechamber 28 in the vicinity of the breaking chamber 20, in this case at the limit of the latter, the second conducting part 31 being, to the right of the overlap point, offset towards the outside of the prechamber 28 relative to the first part

driver 30.

  In view of the above, the point of overlap of the two conductive parts 30, 31 is located in the part of the prechamber 28 where the horns 22, 23 diverge. When the electric arc 17, which has been propelled inside the prechamber 28 towards the breaking chamber 20, reaches the point of overlap after having passed the intermediate zone 29, it jumps from the

  first conductive part 30 to the second 31 without particular difficulty.

  Furthermore, according to the invention, the two conductive parts 30, 31 are in simple mechanical contact, no particular electrical connection such as a weld being provided between them. To this end, and according to an embodiment illustrated in the figures, the second conductive part 31 is nested in the first 30, this nesting sufficient for the relative maintenance of the two parts

  conductive 30, 31 with respect to each other.

  The first conductive part 30 is here in the form of a metal strip made of copper, or of steel covered with a layer of copper, folded so as to have a C-shaped profile and arranged so that its

  concavity is oriented towards the breaking chamber 20.

  Furthermore, the second conductive part 31 is also formed of a metal blade, preferably made of a ferromagnetic material, in particular steel, and which has a straight portion 35 bordering the breaking chamber 20, extended towards the first conductive part by a curved portion 36 having a shape substantially complementary to the first conductive part 30 and fitted in it, so that the second conductive part 31 has a profile substantially at b, the

  convex part is turned towards the prechamber 28.

  The poor electrical contact between the two conductive parts 30, 31, which results from their simple mechanical contact, between them causes the appearance of an electrical resistance which, causing the increase in the voltage of the arc 17, causes a decrease in the cut-off intensity and therefore

  increase of the circuit-breaker's limiting power 1.

  Given their shapes and their respective arrangements, it is likely that the two conductive parts 30, 31 are ultimately in mechanical contact in several places. However, it is preferable that they are in

  contact at least to the right of the fixed contact 7.

  This configuration, namely the shape and the relative arrangement of the conducting parts 30, 31, in particular the arrangement of the first conducting part between the fixed contact 7 and the second conducting part 31, combined with the material of the first and of the second parts conductive 30, 31, respectively of copper and steel, provides a magnetic effect which, by concentrating a magnetic field around the arc 17, propels the latter

  from the formation zone 18 towards the breaking chamber 20.

  In addition, according to one embodiment, the fixed contact 7 is in the form of a silver patch attached to the first conductive part, so that, if the electrical conductivity of the upstream horn 22 decreases from the area of formation 18 of the arc 17 towards the breaking chamber 20, its mechanical resistance to wear increases as for it, which forms a good compromise between the guiding capacities of the arc 17 and the

  longevity of the extinguishing device 19.

  Furthermore, in order in particular to facilitate the passage of the electric arc 17 from the fixed contact 7 to the first conductive part 30, the latter carries a ramp 37 which connects in a substantially continuous manner the contact face 38 of the fixed contact 7, against which is able to come to apply the movable contact 8, and the outer surface 39 of the first conductive part 30. This ramp 37 has the advantage of facilitating the positioning of the fixed contact 7 on the first part

conductive 30 during assembly.

  As regards the downstream horn 23, this can be made in the conventional way of copper, or, preferably, of steel covered for example with a copper layer so as to present both good capacity for

  electrical conductivity and mechanical resistance to wear due to the arc.

  The invention is of course not limited to the embodiment which comes

to be described.

Claims (10)

  1. Device (19) for extinguishing an electric arc (17) established in a zone (18) said to form the arc (17) between a fixed contact (7) and a movable contact (8) d a device (1) for protection such as a circuit breaker, this device (19) comprising: - a breaking chamber (20) located at a distance from said formation zone (18) and formed of a plurality of conductive plates ( 21) superimposed, - two conductors (22, 23) facing one of which one (22) carries the fixed contact (7), adapted to guide the arc (17) from its formation zone (18) towards the cutoff (20) and each having for this purpose an anterior portion (24, 26) delimiting a space (28) said prechamber, located between the formation zone (18) of the arc (17) and the cutout chamber (20 ), this anterior portion (24, 26) being extended by a posterior portion (25, 27) which borders the breaking chamber (20); said device (19) being characterized in that the conductor (22) carrying the fixed contact (7) is formed by two separate conductive parts (30, 31) which overlap and are in simple mechanical contact, namely a first part ( 30) forming the front portion (24) of said conductor (22), and a second   piece (31) forming its rear portion (25).   2. Device according to claim 1, characterized in that the first   co nd u ctrice part (30) is real isoe in copper.   3. Device according to claim 1 or 2, characterized in that the second conductive part (31) is made of a ferromagnetic material.   4. Device according to one of claims 1 to 3, characterized in that   the second conductive part (31) is made of steel.   5. Device according to one of claims 1 to 4, characterized in that   said fixed contact (7) is in the form of a silver pastille.   6. Device according to one of claims 1 to 5, characterized in that   said conductive parts (30, 31) overlap in the prechamber (28) to   the limit of the breaking chamber (20).   7. Device according to one of claims 1 to 6, characterized in that   the second conductive part (31) is nested in the first (30).   8. Device according to one of claims 1 to 7, characterized in that   the first conductive part (31) carries said fixed contact (7) 9. Device according to claim 8, characterized in that the conductive parts (30, 31) are in mechanical contact at least in line with the fixed contact (7). lO. Device according to claim 8 or 9, characterized in that, said fixed contact (7) being in relief with respect to the first conductive part (30) and having a contact face (38) against which is able to come to apply led it movable contact (8), the first conductive part (30) carries a ramp (37) connecting substantially said contact face (38) and the surface   outside (39) of the first conductive part (30).   11. Limiter circuit breaker, characterized in that it comprises a device (19)   according to one of claims 1 to 10.   12. Limiter circuit breaker according to claim 11, characterized in that it comprises an electromagnet (9) adapted to control the separation of the fixed (7) and mobile (8) contacts, said electromagnet (9) comprising a coil (10) connected electrically at the end, on the one hand, to a contact terminal (5) of the circuit breaker (1)