FR2655770A1 - MULTIPOLAR CIRCUIT BREAKER WITH GAS FILTER COMMON TO THE DIFFERENT POLES. - Google Patents

Abstract

An additional filtering unit 25 is associated with a low voltage molded case circuit breaker to receive in a common chamber 26, provided with a cooling grid, the cut-off gases escaping from the orifices 21,22,23, of the three poles of the circuit breaker.

Description

The invention relates to a low-voltage multipole circuit breaker with

  molded housing, subdivided by insulating partitions into internal compartments each associated with one of the poles, each compartment containing a pair of separable contacts, a stack of arc deionization plates, drawn during the separation of said contacts and an orifice cut-off gas exhaust provided with a first cooling device

these gases.

  Cutting a short-circuit current with or without limitation

  current, can only be done by absorbing energy.

  The order of magnitude of this energy is from one to two times the inductive energy of the circuit acquired at the value of the peak current Cutting by an arc circuit breaker amounts to using a plasma as an essential intermediary to absorb this energy If the elongation of the arc is not enough to ensure cutting, it is forced against and in a breaking chamber This chamber is generally constituted by a stack of metal plates, whether the arc, split or not,

  will heat, melt and partially vaporize.

  All these thermal phenomena are well known for their

  great energy absorption capacities.

  The arc column, brought to high temperature (y 15000 K) in a reduced volume, gives rise to high pressures and, in order to limit these pressures and to contribute to the displacement of the arc in the chamber, openings are provided specially designed which allow a flow of some of these gases to the outside after they have passed through a

  more or less effective filtering to cool them.

  Depending on the installation conditions, these still hot and ionized gases can be a nuisance for the environment and cause harmful effects such as fires, ignitions, burns, pressure in the boxes, leakage currents during cutting. One solution is to reinforce the filtering device but it quickly becomes too bulky and difficult to install pole by pole on a circuit breaker

  multipolar, without penalizing the installation conditions.

  The present invention aims to allow the production of an efficient exhaust gas filtering device

and a reduced size.

  The circuit breaker according to the invention is characterized in that all of said exhaust orifices open into a chamber common to the different poles and communicating with the ambient medium by a gas outlet opening and that a second cooling device is arranged. on the gas flow path between said orifices

exhaust and said outlet.

  According to the present invention, the hot gases are cooled by a second filter common to all the poles and the size of this common filter is less than that of equivalent individual complementary filters. The invention is based

  on the observation that when breaking a short-circuit current

  circuit, for example three-phase, only one of the poles is requested to the maximum and the common cooling or filtering chamber does not need to be adapted to three times this maximum value, but only to twice The cost and the space of the additional filter can therefore be reduced It is possible to provide such a permanent filter on the circuit breaker, or integrated therein, or to arrange this filter in a complementary filter block, which can be associated with the circuit breaker or chassis thereof, during demanding installation conditions, in particular inside cabinets subjected to exceptional climatic conditions or during

special uses.

  The common cooling device or filter comprises a stack of grids, preferably metallic, disposed on all of the poles of the circuit breaker at a distance sufficient to provide a distribution volume of the gases which can come from any of the poles during switching off. This volume is also a function of the optimal pressures sought

  so as not to react to the quality of the cut.

  The gases which pass through the filter are hot and partially ionized, and according to an improvement of the invention the metal grid (s) are mounted on an insulating support or frame and can be brought to a floating potential, different from that of the mass, without generate leakage currents and

risk of priming.

  A second volume is advantageously cleaned downstream of the filter grid to ensure the evacuation of the already cooled gases to the outside. This volume is defined according to the installation cases, in particular safety conditions to be observed to ensure double screw insulation. -visiting a part in floating potential and having dimensions greater than 50 mm. The calculation of the mass of the filter must take into account various factors, in particular the energy released to the outside of the circuit breaker, for example 5 to 10% of the total arc energy and the acceptable temperature rise. The filter may be a single grid or any other perforated or porous material or a stack, for example of adjacent or spaced grids The path of gas escaping from the first cooling device is advantageously rectilinear through the two volumes and the filter grid towards the In some cases, vents in the first volume of the filter allow direct exhaust

  part of the gases to non-hazardous areas.

  Other advantages and features will emerge more

  clearly from the following description of two modes of

  embodiment of the invention, given by way of nonlimiting examples and shown in the appended drawings, in which: FIG. 1 is a diagrammatic elevation view, partially cut away of a circuit breaker according to the invention; Figure 2 is a cross section of the circuit breaker according to Fig 1; Figure 3 is a perspective view of a circuit breaker without additional filter; Figure 4 is a perspective view, partially in section of an additional filter; Figure 5 is a perspective view of an alternative embodiment according to the invention; Figure 6 is a partial cross section of the circuit breaker and its frame according to Figure 5; Figures 7 and 8 are perspective views of the circuit breaker and

of the filter according to figure 5.

  In the figures, a low voltage circuit breaker 10, with molded housing 11, of the type commercially known as MASTERPACT, has three adjacent poles 12,13,14, and separated by internal partitions, 16 The three poles 12,13, 14 are identical and have each of the input and output pads 17, a pair of separable contacts 18, a breaking chamber formed by a stack of deionization sheets 19 and a filtering or cooling device 20 associated with an exhaust orifice 21, 22 , 23 of the poles 12,13,14 A mechanism 24, of which only the lever is shown, controls the opening and closing of the poles 12,13,14 including the automatic opening on fault with

  arcing, when the contacts are separated 18.

  The action of the arc causes heating and overpressure in each blade 12,13,14 with an escape of gas by the

  orifices 21, 22, 23 through the cooling filters 20.

  The intensity of the different arcs depends on the intensity of the current cut in each pole, only one of the poles 12,13,14 being stressed to the maximum. Such a circuit breaker is well known and it is

  no need to describe it in more detail.

  According to the invention an additional cooling or filtering block 25, schematically represented in FIG. 4, is attached to the molded housing 11 opposite the exhaust orifices 21, 22, 23 to confine a common chamber 26 into which the orifices open 21,22,23 of the three poles The chamber 26 is subdivided into two volumes 27 and 28 by a cooling grid 29, forming an internal perforated partition The first volume 27, opposite the circuit breaker 10, distributes the gases escaping from the orifices 21,22,23 and going through the grid 29 to the second volume 28, which communicates with the outside or the surrounding environment by openings 30, formed in the block 25 The grid 29 is electrically insulated, for example by making the walls of the block 25 in a molded insulating material or in any other way to consider it, during a cut, at a floating potential, with respect to the ionized gases passing through the orifices 21,22,23 The first volume 27 is large enough to equalize the pressure in this volume of the gases leaving the different orifices 21, 22, 23, these passing through a substantially rectilinear trajectory the grid 29 the second volume 26 and the openings 30, undergoing additional cooling The dimensions of the second volume 28 and of the openings 30 are determined by the gas flow and safety conditions and the additional filter 25 is adapted to the optimal overpressures for the

break in the poles 12,13,14.

  It is clear that during a short circuit cut, the gases escaping from the most charged pole use a greater part of the cooling capacity of the grid 29 than those from the least charged pole and this distribution allows a reduction in the capacity of the complementary filter 25 compared to three individual filters, associated with the three ptles 12,13,14 The filter 25 can be fixed by any suitable means to the molded housing 11 and it is also possible to integrate this block 25 to the molded housing 1 1 by providing a common chamber, communicating with the three poles through the orifices 21, 22, 23 and containing an additional common filter 29 Likewise, the grid 29 can be constituted by a superposition of several grids or be

  replaced by a porous or perforated block.

  Figures 5 to 8 illustrate an alternative embodiment, in which the same reference numbers are used to designate

  parts similar or identical to those of FIGS. 1 to 4.

  The circuit breaker 10 is associated with a racking-in frame 31, having on the rear side racking-in pliers 32, cooperating with the pads 1 7 and on the front side a connection block 33 The additional filtering block 25 is fixed to the chassis 31 in such a way that this block 25 faces the exhaust orifices 21, 22, 23 when the circuit breaker 10 is plugged in in the working position The operation of course remains the same,

  the addition of additional filtering taking place automatically

  only during the installation of the circuit breaker The chassis or chassis 31, housed in a cabinet subjected to exceptional operating conditions requiring additional cooling of the breaking gases, can be fitted with filter blocks 25 without requiring any modification of the circuit breaker. The additional block can of course be associated or integrated with circuit breakers of different structure, shape and

  constitution being adapted accordingly.

  The invention is not limited to the embodiments described.

Claims (8)

  1) Low-voltage multipole circuit breaker with molded case (11), subdivided by insulating partitions (15,16) into internal compartments each associated with one of the poles (12,13,14), each compartment containing a pair of separable contacts (18), a stack of metal sheets (19) for deionizing the arc, drawn during the separation of said contacts and an orifice (21, 22, 23) for exhaust of the breaking gases, provided with a first device ( 20) for cooling these gases, characterized in that all of said exhaust orifices (21, 22, 23) open into a chamber (26) common to the different poles and communicating with the ambient medium by an opening (30) gas outlet and a second cooling device (29) is disposed on the gas flow path between said exhaust ports (21,22,23) and said outlet ( 30).   2) Multipolar circuit breaker according to claim 1, characterized in that said second cooling device (29) comprises metal parts of   filtering of gases mounted isolated on a support frame.   3) Multipolar circuit breaker according to claim 1 or 2, characterized in that said common chamber (26) is integrated into the   molded case (11) of the circuit breaker.   4) Multipolar circuit breaker according to claim 1 or 2, characterized in that said common chamber (26) is constituted by a block (25) capable of being attached to said molded shoemaker   (11) opposite said exhaust orifices (21,22,23).   (5) Multipole circuit breaker according to any one of   previous claims, characterized in that the gases   leaving the stack of deionization plates (19) of the circuit breaker follow a substantially straight path passing successively through the exhaust orifices (21,22,23), the second cooling device (29) and the outlet opening (30).   6) Multipole circuit breaker according to any one of   previous claims, characterized in that the second   cooling device (29) is a metal grid   subdividing said room into two volumes (27,28).   7) Multipole circuit breaker according to any one of   previous claims, arranged in a cabinet   metallic, characterized in that said second cooling device (29) in the form of a metallic grid is isolated from   other parts of the circuit breaker and the metal cabinet.   8) Multipole circuit breaker according to any one of   previous claims, mounted on a withdrawable chassis   (31) characterized in that said common chamber (26) is integral with said chassis (31) and arranged so as to come opposite the exhaust orifices (21,22,23) during   racking-in of the circuit breaker in working position.