EP0437151B1 - Multipolar circuit-breaker with a gas filter which is common to different poles - Google Patents

Description

The invention relates to a low-voltage multi-pole circuit breaker with molded case and double cut-off gas cooling device, 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 sheets, drawn during the separation of said contacts and an orifice for exhaust of the breaking gases provided with a first device for cooling these gases.

The breaking of a short-circuit current with or without current limitation 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 sufficient to ensure breaking, it is forced against and in a breaking chamber. This chamber is generally formed by a stack of metal plates, which the arc, split or not, will heat, melt and partly vaporize.

All these thermal phenomena are well known for their great energy absorption capacities.

The arc column, brought to high temperature (≃ 15,000 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 studied which allow a flow of a part of these gases towards the outside after they have passed through a more or less effective filtering device to cool them.

Depending on the installation conditions, these still hot and ionized gases can cause discomfort for the environment and generate harmful effects such as fires, ignitions, burns, pressure in the boxes, leakage currents during the cut. One solution is to strengthen or double the filtering device, but it quickly becomes too bulky and difficult to install pole by pole on a multipole circuit breaker, without penalizing the installation conditions.

Document DE-A-1 788 098 describes in particular a multipolar circuit breaker with a double gas cooling device.

The present invention aims to allow the production of an exhaust gas filtering device which is efficient and of a reduced bulk.

The circuit breaker according to the invention is described in claim 1.

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 during the breaking of a short-circuit current, for example three-phase, only one of the poles is stressed to the maximum and the common cooling or filtering chamber does not need to be adapted to three times this maximum value, but only twice. The cost and size of the additional filter can therefore be reduced. It is possible to provide such a permanent filter on the circuit breaker, or integrated into it or to arrange this filter in a complementary filtering block, which can be associated with the circuit breaker or the frame thereof, under conditions of 'demanding installation, in particular inside cupboards subjected to exceptional climatic conditions or during special uses.

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

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 the safety conditions to be observed to ensure double insulation against 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 from 5 to 10% of the total arc energy and the acceptable heating. The filter can 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 outside. In some cases, vents in the first volume of the filter allow a direct escape of part of the gases to non-hazardous areas.

• la figure 1 est une vue schématique en élévation, partiellement arrachée d'un disjoncteur selon l'invention;
• la figure 2 est une coupe transversale du disjoncteur selon la fig. 1;
• la figure 3 est une vue en perspective d'un disjoncteur sans filtre complémentaire;
• la figure 4 est une vue en perspective, partiellement en coupe d'un filtre complémentaire;
• la figure 5 est une vue en perspective d'une variante de réalisation selon l'invention;
• la figure 6 est une coupe transversale partielle du disjoncteur et de son châssis selon la figure 5;
• les figures 7 et 8 sont des vues en perspective du disjoncteur et du filtre selon la figure 5.

Other advantages and characteristics will emerge more clearly from the following description of two modes of embodiment of the invention, given by way of examples and shown in the accompanying drawings, in which:

• Figure 1 is a schematic elevational view, partially broken 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;
• FIGS. 7 and 8 are perspective views of the circuit breaker and of the filter according to FIG. 5.

In the figures, a low voltage circuit breaker 10, with a molded housing 11, of the type commercially known as MASTERPACT, has three adjacent poles 12,13,14, and separated by internal partitions 15,16. The three poles 12, 13, 14 are identical and each comprise input and output pads 17, a pair of separable contacts 18, a breaking chamber formed by a stack of deionization plates 19 and a filtering or cooling 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 in particular the automatic opening on fault with arcing, during the separation of the contacts 18. The action of the arc causes overheating and overpressure in each pole 12,13,14 with a gas exhaust through 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 there is no need to describe it in more detail.

According to the invention an additional cooling or filter block 25, schematically shown 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 21, 22, 23 of the three poles open. 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 directing through the grid 29 to the second volume 28, which communicates with the outside or the ambient medium 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 various orifices 21, 22, 23, these passing through a grid, along a substantially straight path, the grid 29, the second volume 28 and the openings 30, undergoing a 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 cutting 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 of the capacity of the complementary filter 25 with respect to three individual filters, associated with the three poles 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 into the molded housing 11 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.

FIGS. 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 frame 31, having on the rear side racking clamps 32, cooperating with the pads 17 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 when the circuit breaker is installed. 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, the shape and the constitution being adapted accordingly.

Claims (8)

1. A low-voltage multipole circuit breaker with moulded case (11) and double breaking gas cooling device (20, 29), said circuit breaker being subdivided by isolating partitions (15, 16) into internal compartments each associated to one of the poles (12, 13, 14), each compartment containing a pair of separable contacts (18), a stack of plates (19) for deionisation of the arc drawn when separation of said contacts (18) takes place and an orifice (21, 22, 23) for outlet of the breaking gases, equipped with a first cooling device (20) of these gases, characterized in that the set of said outlet orifices (21, 22, 23) exit into a chamber (26) common to the different poles (12, 13, 14) and communicating with the ambient environment via an opening (30) for outlet of the gases and that the second cooling device (29) is arranged on the outlet path of the gases between said outlet orifices (21, 22, 23) and said gas outlet opening (30).
2. The multipole circuit breaker according to claim 1, characterized in that said second cooling device (29) comprises metal gas filtering parts mounted insulated on a support frame.
3. The multipole circuit breaker according to claim 1 or 2, characterized in that said common chamber (26) is integrated in the moulded case (11) of the circuit breaker.
4. The multipole circuit breaker according to claim 1 or 2, characterized in that said common chamber (25) is formed by a unit (25) able to be adjoined to said moulded case (11) opposite said outlet orifices (21, 22, 23).
5. The multipole circuit breaker according to any one of the foregoing claims, characterized in that the gases outlet from the stack of deionisation plates (19) of the circuit breaker follow an appreciably straight path passing successively via the outlet orifices (21, 22, 23), second cooling device (29) and outlet opening (30).
6. The multipole circuit breaker according to any one of the foregoing claims, characterized in that the second cooling device (29) is a metal grate subdividing said chamber into two volumes (27, 28).
7. The multipole circuit breaker according to any one of the foregoing claims, located in a metal cabinet, characterized in that said second cooling device (29) in the form of a metal grate is insulated from the other parts of the circuit breaker and from the metal cabinet.
8. The multipole circuit breaker according to any one of the foregoing claims, mounted on a withdrawable rack (31), characterized in that said common chamber (26) is securedly united to said frame (31) and arranged in such a way as to come oppcsite the outlet orifices (21, 22, 23) when the circuit breaker is drawn-in to the working position.

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