FR2622736A1 - LOW VOLTAGE CIRCUIT BREAKER, DIRECT CURRENT, AND ARC GUIDED CHEEKLES - Google Patents

Abstract

The arc-forming chamber of a low-voltage, direct-current circuit breaker is delimited laterally by two cheeks 40, 42, one of which 42 is made of gas-generating nylon and the other 40 of which is ceramic, serves as a support for a permanent magnet 44.

Description

LOW VOLTAGE CIRCUIT BREAKER WITH DIRECT CURRENT AND GUIDE SHEETS

OF THE ARC

  The invention relates to a low voltage circuit breaker with molded case, intended for breaking direct currents, comprising a breaking chamber subdivided into an arc extinguishing chamber constituted by a stack of metal deionization plates and, a forming chamber. arc provided with separable contacts and delimited by two parallel cheeks, a permanent magnet being disposed between one of the cheeks and the adjacent wall of the housing so as to accelerate the movement of

  the arc towards the arc extinguishing chamber.

  Such a circuit breaker allows, thanks to the presence of the permanent magnet, to obtain an effective breaking of direct currents

low intensity.

  The object of the present invention is to improve the breaking of a circuit breaker of this type in the case of direct currents.

higher intensity.

  According to the invention, this object is achieved by the fact that the first cheek disposed on the side of the permanent magnet is made of ceramic material, the second cheek being made of a gas-generating organic material. According to a preferred embodiment, the second cheek is made of gas-generating nylon, and the permanent magnet is stuck in a cavity

  formed in the outer wall of the first cheek.

  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 shown in the appended drawings, in which: - Figure 1 is a schematic view, in elevation, of a circuit breaker according to the invention, the cover is removed; - Figure 2 is a rear view, in elevation, of the ceramic cheek of the circuit breaker according to Figure 1; - Figure 3 is a section along line III-III of Figure 2; and - Figure 4 is a partial section along line IVIV of the

figure 1.

  In FIG. 1, a miniature circuit breaker pole comprises a casing 10 made of molded insulating material, having on its upper face 12 an operating handle 14 and on the two narrow lateral faces of the connection terminals 16 and 18. Inside the housing are housed a movable contact 20 and a fixed contact 22, electrically connected by a conductor 24 to the terminal 16. The movable contact is controlled by a control mechanism, designated by the general reference 26, connecting the lever 14 to the movable contact 20 In the case are also housed a thermal trip device formed by a bimetallic strip 28 and an electromagnetic trip device 30, capable of causing, in the event of an overload or short-circuit, an automatic opening of the contacts 20, 22. The lower part of the boot 10 contains a

breaking chamber.

  The connection conductor 24 extends beyond the fixed contact

  22 to constitute an electrode or arc horn 32.

  The upper side of the breaking chamber is delimited by an electrode or arc horn 34 electrically connected to the connection terminal 18. The arc horns 32, 34 are arranged so as to pick up an arc drawn between the contacts 20, 22, during their separation. The breaking chamber is divided into an arc extinguishing chamber 36, comprising a stack of metal deionization plates 38, and into an arc forming chamber delimited laterally by two cheeks, 40 and 42, parallel, for guiding of

  the arc framing the pair of contacts 20.22.

  Such a circuit breaker, described in detail in particular in French patent No. 2,344,949 of the applicant, is well known to specialists and it is unnecessary to describe in more detail its

arrangement or its operation.

  According to the invention, the circuit breaker, intended for breaking direct currents, comprises a first cheek 40, made of ceramic material, serving as a support for a permanent magnet 44, and a second nozzle 42 made of an organic gas-generating material, for example in nylon. The magnet 44 is arranged so as to generate a permanent magnetic field causing the displacement of the arc roots towards the extinguishing chamber 36. This magnetic blowing effect is particularly useful for

  low intensity direct current.

  The magnet 44 can be fixed in any suitable manner, for example by gluing on the external face of the cheek 40. In the preferred embodiment shown in the figures, the magnet is glued in a cavity 46 formed in the rear part of the

plays 40.

  Due to the lateral position of the magnet in the arc chamber, the magnetic field can be broken down into two perpendicular components, one of which, main, creates a force causing the arc to move towards the chamber arc extinction 36. The other component creates a force perpendicular to the previous one, tending to move the arc in

  cheek direction 40 carrying the magnet.

  To avoid too rapid wear of this cheek, it is therefore necessary to use a cheek made of ceramic material, for example

example in soapstone.

  According to the invention, the displacement of the arc in the direction of the cheek serving as a support for the permanent magnet is used to combine, in the same circuit breaker, a magnetic blowing effect of the arc used essentially for cutting direct currents of low intensity, and a gas-type blowing intended to facilitate the breaking of more currents

high intensity.

  For this purpose, the cheek 42, opposite the ceramic cheek 40, which carries the magnet, is not made of the same material as the latter, but of a material which, if it has less resistance to wear, can be gasifier or be coated with a gasifier material. In the preferred embodiment, the

  cheek 42 is a gasogenic nylon cheek.

  The slight offset of the arc in the direction of the ceramic cheek 40, due to the presence of the magnet on this cheek, makes it possible to use for the opposite cheek 42 gasogenic nylon which is less resistant to wear, but whose properties gasifiers advantageously combine with the magnetic blowing properties of

the permanent magnet.

Claims (5)

  1. Low-voltage molded case circuit breaker, intended for breaking direct currents, comprising a breaking chamber subdivided into an arc extinguishing chamber (36), constituted by a stack of metal deionization plates (38) and a arc formation chamber provided with separable contacts (20,22) and delimited by two parallel cheeks (40, 42), a permanent magnet (44) being disposed between one (40) of the cheeks and the adjacent wall of the housing so as to accelerate the movement of the arc towards the arc extinguishing chamber, characterized in that the first cheek (40) disposed on the side of the permanent magnet (44) is made of ceramic material, the second   cheek (42) being made of a gas-generating organic material.   2. Circuit breaker according to claim 1, characterized in that the   second cheek (42) is made of gas-generating nylon.   3. Circuit breaker according to any one of claims 1 and 2,   characterized in that the permanent magnet (44) is carried by the first cheek (40).   4. Circuit breaker according to claim 3, characterized in that the permanent magnet (44) is fixed in a cavity (46) formed in   the outer wall of the first cheek (40).   5. Circuit breaker according to one of claims 3 and 4,   characterized in that the magnet (44) is glued to the first cheek (40).