EP0022708B1 - Arc quencher for multi-pole low-tension circuit breaker with moulded casing - Google Patents

Description

• -une paire de contacts séparables fixe et mobile,
• - un mécanisme d'actionnement du contact mobile déplaçable entre des positions de fermeture et d'ouverture,
• - des tôles métalliques de refroidissement de l'arc tiré entre lesdits contacts lors de leur séparation après déclenchement du disjoncteur,
• - un orifice d'échappement des gaz de coupure ménagé dans le boîtier à la sortie de ladite chambre,
• -et un dispositif de désionisation agencé au voisinage dudit orifice d'échappement pour refroidir les gaz de coupure ventilés vers le milieu extérieur.

The invention relates to an arc extinguishing chamber for a multipolar low-voltage circuit breaker with a casing made of molded insulating material, comprising per pole:

• -a pair of separable fixed and mobile contacts,
• - a mechanism for actuating the movable contact movable between closed and open positions,
• - metal sheets for cooling the arc drawn between said contacts during their separation after tripping of the circuit breaker,
• a cut-off gas exhaust orifice provided in the housing at the outlet of said chamber,
• -and a deionization device arranged in the vicinity of said exhaust orifice to cool the cut gases vented to the outside environment.

According to a known circuit breaker of the kind mentioned, described in French patent No. 2 269190, the deionization device comprises metal grids or screens with fine mesh, in particular made of steel, housed in the exhaust orifices. The cut-off gases generated in the extinguishing chamber during the cut-off are ventilated to the outside environment after passage through the grids acting as flame arresters, and it has been found that these gases were still strongly ionized at the outlet of the bedroom.

To improve the cooling of the cut-off gases, deionization devices of complicated structure have already been proposed, the large size of which does not allow their use in compact extinguishing chambers for circuit-breakers with molded housings.

According to French Patent No. 1,364,701 relating to a disconnector under load at medium voltage and with magnetic blowing, the chamber is delimited by two transverse walls and is filled over its entire height by a refractory ceramic material or by sand (quartz, zircon...). The arc is extinguished inside the granular mass, and a blowing coil is essential to drive the initial arc into said mass.

According to Swiss Patent No. 247,847, the particle size of the sand in the extinguishing chamber decreases in the direction of movement of the arc.

According to French Patent No. 1,544,434, a succession of expansion and cooling compartments is arranged after the priming chamber and the extinguishing chamber. Each compartment is shaped by a plurality of metal plates perforated by holes of different sizes, so as to form a baffle. The whole has a complicated structure occupying a large bulk.

According to British Patent No. 551 966. the sand is retained by a grid or bars. A magnetic blowing coil or an auxiliary pneumatic blowing device drives the arc towards the chamber filled with said sand.

The object of the invention is to avoid the aforementioned drawbacks and to allow the production of an extinguishing chamber with high breaking capacity, equipped with an improved deionization device of compact structure compatible with the reduced size of the circuit breaker. and allowing efficient cooling of the cut-off gases ventilated to the outside environment.

The extinguishing chamber is characterized in that the deionization device comprises a one-piece exhaust screen of porous structure formed by beads or grains agglomerated by any heating or sintering process, and having dimensions of between 0.5 mm and 1.5 mm corresponding to a predetermined particle size of said porous structure provided with interstices for passage of the cutting gases towards the external medium, the material of the balls comprising a metal or an alloy.

The material of the beads is advantageously based on copper, in particular bronze.

• la figure 1 est une vue en coupe longitudinale d'une chambre d'extinction d'arc selon l'invention, d'un disjoncteur à boîtier moulé représenté partiellement arraché ;
• la figure 2 est une vue de profil de la figure 1, une seule connexion extérieure étant connectée à une plage de sortie du pôle central ;
• la figure 3 représente en perspective le dispositif de désionisation de la fig. 1.

Other advantages and characteristics will emerge more clearly from the description which follows of an embodiment of the invention, given by way of nonlimiting example and represented in the appended drawings, in which:

• Figure 1 is a longitudinal sectional view of an arc extinguishing chamber according to the invention, of a molded case circuit breaker shown partially cut away;
• Figure 2 is a side view of Figure 1, a single external connection being connected to an output pad of the central pole;
• FIG. 3 shows in perspective the deionization device of FIG. 1.

With reference to FIGS. 1 to 3, the low-voltage multi-pole circuit breaker 10 with housing 12 made of molded insulating material and with manual control lever 14, comprises, by pole, an arc extinguishing chamber 16 housed in a lower compartment 18 of the housing 12 .

Each arc extinguishing chamber 16 comprises a pair of separable contacts 20, 22 and a stack of V-shaped cooling plates 24 extending transversely to the direction of extension of the arc drawn between the contacts 20, 22 during their separation after tripping of the circuit breaker. The fixed contact 20 is supported by a conductor 26 in the form of a U-shaped pin, positioned on an intermediate wall 27 of the housing 12 and in electrical connection with an external connection pad 28. A metal shielding element 30 is inserted between the two branches of the conductor pin 26, and is provided with an extension 32 acting as an end separator. The movable contact 22 is integral with a contact arm 34 associated with a pivoting bar of the actuation mechanism (not shown) common to all the poles. A connecting braid 36 connects the opposite end of the arm 34 to the thermal and electromagnetic trip elements (not shown) of each pole. The transverse face of the lower compartment of the housing 12 is provided with an orifice 38 for exhaust of the cut-off gases formed at the outlet from each arc extinguishing chamber 16.

According to the invention, a gas deionization device, designated by the general reference 40, is arranged in each exhaust orifice 38 to reduce the external manifestations of the ionized gases in the vicinity of the connections 43 associated with the pads 28 thanks to efficient cooling. hot gases at the outlet of the chamber 16. Each deionization device 40 cooperates with the sheets 24 and comprises a block 41 (fig. 3) or parallelepiped screen of porous structure, formed from beads 42 or agglomerated grains, sparing between them gas passage interstices. The material of the balls 42 has both good thermal conductivity and a high heat capacity, and in particular comprises a metal or alloy with a high melting point such as bronze, copper or steel. It appeared, on the other hand, that the choice of the dimensions of the balls 42 or of the grains was fundamental for determining the optimal particle size of the porous block 41 and obtaining an effective absorption of the heat at the outlet of the chamber 16 without hampering the exhaust of cut-off gases to the outside environment. This particle size depends on the material chosen and on the volume of the porous block 41, and it was found during tests that the diameter of the balls42 or grains had to be between 0.5 mm and 1.5 mm in order to obtain correct exhaust of the gases and a optimum lowering of the outlet gas temperature. In the embodiment shown, the porous block 41 of dimensions 25 mm x 18 mm and thickness 3.6 mm comprises balls 42 of bronze having diameters close to 0.8 mm. The agglomeration operation of the balls 42 or grains can be carried out by any heating or sintering process well known to specialists.

According to an alternative embodiment, the porous block 41 may consist of balls 42 or grains made of non-metallic material, resistant to the high temperatures of the cutting gases, in particular a refractory or powdery ceramic material based on sand, and the dimensions of which are included in the aforementioned range from 0.5 mm to 1.5 mm. An additional case 44, made of insulating material, is arranged in the exhaust zone of each arc extinguishing chamber 16, in the space provided between the ends of the sheets 24 and the porous block 41. The screen 44 s 'extends in the height direction between the bottom 45 of the housing 12 and the intermediate wall 27, and is pierced with a plurality of holes 46 arranged opposite the porous block 41.

The operation of the deionization device 40 according to the invention follows from the preceding description, and it suffices to recall that when the arc is cut in the extinguishing chamber 16, the cutting gases after passing through the screen 44 insulator, are effectively cooled in the porous block 41 and escape to the outside environment.

The invention is of course in no way limited to the embodiment more particularly described and shown in the accompanying drawings, but it extends quite the contrary to any variant remaining within the framework of mechanical and electrical equivalences, in particular that in which the balls 42 or grains of the porous block would be replaced by other agglomerated elements.

Claims (3)

1. Arc quencher chamber for multi-pole low- tension circuit breaker with moulded insulating casing (12) comprising per pole :

-a pair of separable stationary (20) and movable (22) contacts,

- a driving mechanism for moving between the open and closed positions the movable contact (22),

- metal plates (24) for cooling the arc drawn between said contacts when they separate upon tripping of said circuit breaker,

- an extinction gas venting opening (38) provided in the casing (12) near the output of the chamber (16),

- a deionizing device (40) located near said venting opening for cooling the extinction gas blown outsides, characterized by the fact that the deionizing device comprises a monobloc venting screen (41) with a porous structure formed by balls or corns agglomerated by a sintering or heating process and having a size included between 0,5 mm and 1,5 mm corresponding to a predetermined granulometry of said porous structure having extinction gas venting intervals, the ball material comprising a metal or an alloy.

2. Arc quencher chamber, according to claim 1, characterized by the fact that the base of the material is copper.

3. Arc quencher chamber according to claim 2, characterized by the fact that the material is bronze.

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