Electric arc-blast nozzle made of a material comprising micro-capsules of liquid (CF3)2CFCN and a circuit breaker including such a nozzle

Abstract

The invention relates to an electric arc-blast nozzle (5) for a circuit breaker comprising a middle portion (7) forming a throat defining internally an axial passage (13) for interrupting an electric arc, and two end portions (9, 11) extending on either side of the middle portion (7) and being designed to receive respective arcing contacts (1) and (3) that are movable axially relative to each other. The middle portion (7) and the two end portions (9, 11) are made of a same dielectric material obtained from a composition comprising a fluorocarbon polymer matrix, at least one inorganic filler and micro-capsules of liquid heptafluoro-iso-butyronitrile. The invention also relates to a circuit breaker including such a nozzle (5).

Claims

1. An electric arc-blast nozzle for a circuit breaker, comprising: a middle portion forming a throat defining internally an axial passage for breaking an electric arc, and two end portions extending on either side of the middle portion and being designed to receive respective arcing contacts that are movable axially relative to each other, between an open position of the circuit breaker in which the arcing contacts are separated from each other and a closed position of the circuit breaker in which the arcing contacts are in contact with each other and in which one of the arcing contacts partially closes the axial passage of the middle portion, an arc-control gas flowing through the axial passage of the middle portion in order to interrupt the electric arc that is likely to form during movement of the arcing contacts from the closed position to the open position of the circuit breaker, the electric arc-blast nozzle being characterized in that the middle portion together with the two end portions are made of a same dielectric material obtained from a composition comprising a fluorocarbon polymer matrix, at least one inorganic filler and micro-capsules of liquid heptafluoro-iso-butyronitrile.

2. The electric arc-blast nozzle according to claim 1, wherein the composition consists of the fluorocarbon polymer matrix, of one or more inorganic filler(s) and of micro-capsules of liquid heptafluoro-iso-butyronitrile.

3. The electric arc-blast nozzle according to claim 1, wherein a proportion by weight of the micro-capsules of liquid heptafluoro-iso-butyronitrile lies in a range 0.1% to 30% relative to a total weight of the composition.

4. The electric arc-blast nozzle according to claim 1, wherein said inorganic filler(s) are selected from a group consisting of oxides, fluorides, sulfides, graphite, mica, glass, ceramics and mixtures thereof.

5. The electric arc-blast nozzle according to claim 1, wherein a proportion by weight of the inorganic filler(s) lies in a range 0.1% to 30% relative to a total weight of the composition.

6. The electric arc-blast nozzle according to claim 1, wherein the fluorocarbon polymer of the composition is selected from a group consisting of a polytetrafluoroethylene, a perfluoroalkoxy, fluorinated ethylene propylene, a vinylidene polyfluoride and a copolymer of ethylene and of tetrafluoroethylene, and is a polytetrafluoroethylene.

7. The electric arc-blast nozzle according to claim 1, further comprising a sheath disposed on a first outside surface of each of the two end portions and on a second outside surface of the middle portion forming the throat.

8. The electric arc-blast nozzle according to claim 1, wherein both of the arcing contacts are movable.

9. The electric arc-blast nozzle according to claim 8, further comprising a cap that surrounds the arcing contact, this cap being made of the same dielectric material than the dielectric material of the middle portion and the two end portions.

10. A medium- or high-voltage circuit breaker comprising: at least two arcing contacts that are movable axially relative to each other, between the open position of the circuit breaker in which the arcing contacts are separated from each other and the closed position of the circuit breaker in which the arcing contacts are in contact with each other, the electric arc-blast nozzle as defined according to claim 1, and the arc-control gas flowing through the axial passage of the middle portion of the nozzle in order to interrupt the electric arc that is likely to form during movement of the arcing contacts from the closed position to the open position of the circuit breaker.

11. The circuit breaker according to claim 10, wherein the arc-control gas comprises heptafluoro-iso-butyronitrile in a mixture with a dilution gas.

12. The circuit breaker according to claim 10, wherein the arc-control gas is a mixture of 2 molar percent (mol %) to 15 mol % heptafluoro-iso-butyronitrile, 60 mol % to 98 mol % carbon dioxide and 0 to 25 mol % oxygen.

13. A method for releasing heptafluoro-iso-butyronitrile into an arc-control gas of a medium- or high-voltage circuit breaker in use, the arc-control gas comprising heptafluoro-iso-butyronitrile in a mixture with a dilution gas, wherein the method consists in implementing a coating formed by a dielectric material obtained from a composition comprising a fluoropolymer matrix, at least one inorganic filler and microcapsules of liquid heptafluoro-iso-butyronitrile inside said medium- or high-voltage circuit breaker.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a fragmentary and diagrammatic view in longitudinal section of a circuit breaker including an electric arc-blast nozzle of the invention.

(2) FIG. 2 is a fragmentary and diagrammatic view in longitudinal section of a circuit breaker including an electric arc-blast nozzle of the invention, the nozzle being provided with a sheath.

(3) It is stated that the elements shared in FIGS. 1 and 2 are identified by the same reference numbers.

(4) FIG. 3 presents the nozzle material implemented in the invention (FIG. 3A) and its interaction with arc and evaporation process (FIG. 3B).

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

(5) FIG. 1 shows a circuit breaker portion. The circuit breaker includes: at least two arcing contacts 1 and 3 that are movable axially relative to each other, along an axis A, between an open position of the circuit breaker in which the arcing contacts 1 and 3 are separated from each other and a closed position of the circuit breaker in which the arcing contacts 1 and 3 are in contact with each other; and an arc-blast nozzle 5 according to the invention.

(6) This nozzle 5 includes a throat-forming middle portion 7, an end portion 9 disposed upstream and an end portion 11 disposed downstream, the upstream and downstream disposition of the end portions 9 and 11 being relative to the flow direction of the arc-control gas. These two end portions 9 and 11 extend on either side of the middle portion 7. These portions 7, 9 and 11 are circularly symmetrical about the axis A.

(7) The middle portion 7 defines internally an axial arc-control passage 13, said axial passage 13 having an inlet 13a and an outlet 13b. This middle portion 7 is referred to as the throat-forming middle portion 7, because of the inside sectional area of the axial passage 13, which is smaller than the inside sectional areas of each of the end portions 9 and 11.

(8) The end portions 9 and 11 receive and surround the arcing contacts 1 and 3 respectively.

(9) The end portion 9 disposed upstream makes it possible to channel the arc-control gas situated upstream and intended for blasting the electric arc, whereas the end portion 11 disposed downstream has the function of evacuating and diffusing the gas that has been blasted and that is situated downstream, where upstream and downstream being defined relative to the flow direction of the arc-control gas.

(10) The end portion 9 may also comprise a cap 10 that surrounds the arcing contact 1.

(11) In FIG. 1, the arcing contacts 1 and 3 are separated from each other and therefore correspond to the open position of the circuit breaker.

(12) When the arcing contacts 1 and 3 are in contact with each other, in the closed position of the circuit breaker, the arcing contact 3 partially closes the axial passage 13 of the middle portion 7.

(13) Between the arcing contact 1 and the wall of the end portion 9 there is disposed a delivery channel 15 for conveying the arc-control gas, enabling the gas to flow in the axial passage 13 of the middle portion 7, from its inlet 13a until it reaches its outlet 13b, in order to extinguish an electric arc likely to form during movement of the arcing contacts 1 and 3 from the closed position to the open position of the circuit breaker.

(14) The end portion 11 includes a frustoconical portion 11a extending the middle portion 7 and situated facing the outlet 13b of the axial passage 13, this frustoconical portion 11a being followed by a cylindrical portion 11b.

(15) The throat-forming middle portion 7 together with the cap 10 and the end portions 9 and 11 are made of the same dielectric material. Such a dielectric material is obtained from a particular composition, which comprises a fluorocarbon polymer matrix, at least one inorganic filler and micro-capsules of liquid heptafluoro-iso-butyronitrile.

(16) FIG. 2 shows a nozzle 17 of the invention, which is of the type shown in FIG. 1 and which further comprises a sheath 19 disposed on the outside surface of each of the two end portions 9 and 11 and on the outside surface of the throat-forming middle portion 7.

(17) The sheet 19 is formed from a second dielectric material that also presents good mechanical properties and good high-temperature behavior. Typically, this second dielectric material is obtained from a second composition having a polymer matrix, such as a PTFE matrix, and may include one or more inorganic fillers.

(18) Reference may be made to the summary of the invention for further details about the different variants of this second composition suitable for being envisaged in order to obtain the second dielectric material constituting the sheet 19.

(19) As already indicated, the throat-forming middle portion 7 together with the cap 10 and the end portions 9 and 11 are made of the same dielectric material. Such a dielectric material is obtained from a particular composition, which comprises a fluorocarbon polymer matrix, at least one inorganic filler and micro-capsules of liquid heptafluoro-iso-butyronitrile. In particular embodiments, this material is obtained from a composition consisting of a fluorocarbon polymer matrix, of at least one inorganic filler and of micro-capsules of liquid heptafluoro-iso-butyronitrile. Such a material is represented at FIG. 3A with A representing the fluorocarbon polymer matrix such as PTFE, B the inorganic fillers and C the micro-capsules of liquid heptafluoro-iso-butyronitrile.

(20) Reference may be made to the summary of the invention for further details about the different variants of this particular composition suitable for being envisaged in order to obtain the dielectric material constituting the middle portion 7 and the end portions 9 and 11 of the nozzle 5.

(21) In case of arc, the radiation generates the ablation of the inner surface of the nozzle, to which the portions 11a and 11b in FIGS. 1 and 2 belong. The radiation of the arc will generate fluorocarbon polymer vapor such as PTFE vapor by sublimation and heptafluoro-iso-butyronitrile evaporation, see FIG. 3B. When the arc-control gas comprises CO.sub.2 and heptafluoro-iso-butyronitrile, this evaporation acts as a local source of heptafluoro-iso-butyronitrile and helps keeping constant the heptafluoro-iso-butyronitrile content into the gas phase and therefore contribute to the long term stability of the breaker for arc interruprion and insulation.

BIBLIOGRAPHY

(22) [1] International application WO 2014/037566 [2] International application WO 2015/040069