FR2711012A1 - Circuit breaker with improved arc extinction chamber. - Google Patents

Abstract

The movable contact (14, 14a, 14b) of a circuit breaker engages inside an arc extinguishing chamber (32) to the bottom of the U-shaped slots of the various sheets or separators (34) . The fixed contact (18, 20) is disposed in the vicinity of an end plate at the base of the containment volume of the slots. This arrangement contributes to early cooling of the arc, which reduces the volume of gas while keeping the internal pressure at a moderate value. Application: low voltage circuit breakers.

Description

CIRCUIT BREAKER WITH PERFECTED ARC EXTINGUISHING CHAMBER

  The invention relates to an electric circuit breaker having a fixed contact, a movable contact actuated by a control mechanism between a closed position in which the movable contact is in engagement with the fixed contact, and an open position after separation of said contacts for the interrupting the current flowing through the circuit breaker, a pair of current leads; and at least one arc extinguishing chamber disposed in the vicinity of the contacts for cooling and interrupting the arc during the separation phase of said contacts, said chamber comprising a stack of parallel deionization separators equipped with

U-shaped slits reversed.

  The use of parallel separators made of magnetic steel in an arc extinguishing chamber makes it possible to increase the exchange surface area between the hot gases and the metal, and in favorable cases, to divide the arc into a plurality of short arcs allowing a rise of the arc voltage of twenty volts per separator. In known circuit breakers, the contacts are often arranged in an arc forming chamber separated from the arc extinction chamber by a certain distance allowing the development of the arc. The volume of gas generated by the arc being proportional to its temperature, the pressure inside the chamber can reach a high value when the volume of gas becomes too large. This phenomenon exists in particular with the use of gasogenic insulating materials in contact with the arc. In practice, the arc fits properly between the separators only for relatively weak currents. Above a certain intensity, it remains in the arc-forming chamber, or only partially enters the extinguishing chamber because of the plug effect due to the high pressure. The arc nevertheless manages to cool by a combined effect of convection, conduction in contact with the edge of the separators, and also radiation. The insertion of the arc becomes possible when the diameter of the arc decreases, which occurs when the current begins to decrease after limitation. Such a device delays

the moment of extinction of the arc.

  The object of the invention is to limit the pressure generated in an arc extinguishing chamber of a circuit breaker and to improve the cutoff independently of the value of the short-circuit current. The circuit breaker according to the invention is characterized in that the fixed contact is housed inside the arc extinguishing chamber, and cooperates with the contact piece of the movable contact movable in the formed arc formation volume. by the narrow slots of the successive separators, that the lateral confinement walls of the slots surround the moving contact with a slight clearance, and that

  the end of the movable contact piece travels a path close to the bottom of the slots.

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  According to a characteristic of the invention, the fixed contact is carried by a current supply conductor in the arc-forming volume, and in the vicinity of an end plate of the

arc extinction chamber.

  The arrangement of the arc-forming zone in the confinement volume of the slits of the quenching chamber plates reduces the development of the arc to a minimum trajectory that contributes to early cooling of the arc. This results in a significant decrease in the volume of gas which keeps the internal pressure at a moderate value, even in the presence of a high short-circuit current. The arc penetrates quickly into the interstices of the various sheets by splitting into several short arcs. The rapid increase of the arc voltage is then favorable for rapid extinction of the arc, whatever the value of the current to be interrupted.

  Other advantages and features will become clearer from the description that will be

  follow of an embodiment of the invention, given by way of non-limiting example, and shown in the accompanying drawings, in which: Figure 1 is a schematic sectional view of a circuit breaker pole equipped with chambers

  arc extinction according to the invention.

  Figure 2 is a sectional view along the line 2-2 of Figure 1.

  Figure 3 shows a variant of Figure 2.

  FIG. 4 is a side view of FIG.

  In FIG. 1, a pole 10 of an electrical circuit breaker with a molded insulating housing 12 comprises a mobile bridge-shaped contact 14 carried by a switching rod 16 of insulating material. The movable contact bridge 14 is provided with two contact pieces 14a, 14b cooperating on one side with a first fixed contact 18, and on the opposite side with a second fixed contact 20. The contact bridge 14 is mounted floating on the bar 16 through two springs 22, 24 of contact pressure. The first fixed contact 18 is connected to a range 26 of current supply, and the second fixed contact 20 is connected to another range 28 of supply of

  current, which is diametrically opposite with respect to the axis of rotation of the bar 16.

  To each pair of contacts 14a, 18; 14b, 20 of the pole 10 is associated an arc extinguishing chamber 32 formed by a stack of separators or plates 34 deionization, extending

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  substantially parallel to each other, being separated by regular intervals. Each sheet 34 or separator is made of magnetic steel, and is shaped as a quadrangular plate, equipped with a U-shaped central slot 36 (FIG. 2).

  adapted to the passage of the movable contact 14.

  The presence of the parallel plates 14 in the chamber 32 increases the exchange surface between the hot gases and the metal, followed by the splitting of the arc into a plurality of partial arches hung between the successive plates 34. This results in an increase of the arc voltage, and

a rapid extinction of the arc.

  In FIG. 2, it can be seen that the fixed contact 18 is housed inside the extinguishing chamber 32, and that the displacement of the contact piece 14a of the movable contact 14 in the slots 36 of the plates 34 is effected. The end of the contact piece 14a moves opposite the bottom 38 of the slot 36 of each sheet 34, and the side walls 40, 42 of the narrow slot 36 substantially conform to the shape of the movable contact 14. Such penetration of the movable contact 14 in the slots 36 of the plates 34 makes it possible to obtain the birth of the arc directly inside the chamber 32. The initial arc develops in the volume of the slots 36, and quickly hangs on the sheets 34 by splitting into several short arcs. The early cooling of the arc restricts the volume occupied by the arc in the extinguishing chamber 32, and thereby maintains the pressure at a moderate value, even in the presence of

a short circuit current.

  The current supply range 26, 28 serving as a support for the fixed contact 18, 20 associated is advantageously shaped in half-loop favoring the rapid development of the arc towards

the sheets 34.

  According to the variant illustrated in FIGS. 3 and 4, the plates 134 of the arc extinguishing chamber 132 also comprise narrow U-shaped slots 136 with side walls 140, 142, but the thickness of the two lateral branches 140a, 142a disposed on either side of the slots 136 is greater than that of the rear portion 143 common. After separation of the contacts 18, 14a; 20, 14b, the arc is inserted quickly by magnetic attraction in the interstices 145, 146, 147 formed between the rear portions 143 of successive sheets 134. Each gap between the plates 134 at the anterior portion of the branches 140a, 142a has a thickness substantially equal to half the thickness of the gaps 145, 146, 147. A

  such extinction chamber 132 allows to obtain a rapid cut of the arc.

  The sheets may also be replaced by separators made of porous refractory material.

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Claims (8)

  1.Electric circuit breaker having a fixed contact (18, 20), a movable contact (14, 14a, 14b) actuated by a control mechanism between a closed position in which the movable contact (14, 14a, 14b) is in engagement with the fixed contact (18, 20), and an open position after separation of said contacts for interrupting the current flowing through the circuit-breaker, a pair of current supply conductors (26, 28), and at least one extinguishing chamber arcing device (32, 132) arranged in the vicinity of the contacts for cooling and interrupting the arc during the separation phase of said contacts, said chamber comprising a stack of deionization separators (34, 134) equipped with slots (36, 136) U-shaped inverted, characterized in that the stationary contact (18, 20) is housed inside the arc extinguishing chamber (32, 132), and cooperates with the contact piece (14a, 14b). ) of the moving contact (14) displaceable in the arc-forming volume formed by the slots (36, 136) narrow successive separators (34, 134), that the side walls (40, 42; 140, 142) of the slots (36, 136) surround the movable contact (14) with a slight clearance, and that the end of the movable contact piece (14a, 14b)   travels a path close to the bottom of the slots (36, 136).   Circuit breaker according to Claim 1, characterized in that the fixed contact (18, 20) is carried by a current supply conductor (26, 28) in the arc-forming volume, and   near the end separator of the arc extinguishing chamber (32, 132).   3. Circuit breaker according to claim 1 or 2, characterized in that the current supply conductor (26, 28) is shaped according to a demiboucle facilitating the rapid movement of the arc 2 to the sheets (34, 134).   Circuit breaker according to Claim 1 or 2, characterized in that the thickness of the separators   (34) magnetic material is uniform.   Circuit breaker according to Claim 1 or 2, characterized in that the thickness of the separators   magnetic material decreases towards the exit of the arc extinction chamber.   6. Circuit breaker according to claim 1 or 2, characterized in that the two lateral branches (140a, 142a) disposed on either side of the slot (136) of each separator (134).   has a thickness greater than that of the posterior wall (143) common.   Circuit breaker according to one of Claims 1 to 6, characterized in that the separators are formed by steel sheets. 2711012   Circuit breaker according to one of Claims 1 to 6, characterized in that the separators are   made of a porous refractory material.