Low-voltage circuit breaker

Abstract

A low-voltage circuit breaker comprising one or more electrical poles, each of said poles having an internal space with a contact area and an arc extinguishing area, a fixed contact assembly and a movable contact assembly being positioned in said contact area, said movable contact assembly being movable between a closed position in which it is into contact with said fixed contact assembly and an open position in which it is spaced apart from said fixed contact assembly, an arc chamber comprising a plurality of substantially parallel arc-breaking plates made of a ferromagnetic material being positioned in said arc extinguishing area. The low-voltage circuit breaker is characterized in that said arc chamber further comprises at least one arc-breaking plate which is at least partially made of a ceramic material.

Claims

1. A low-voltage circuit breaker comprising one or more electrical poles, each of said poles having an internal space with a contact area, and an arc extinguishing area, a fixed contact assembly and a movable contact assembly being positioned in said contact area, said movable contact assembly being movable between a closed position in which it is into contact with said fixed contact assembly and an open position in which it is spaced apart from said fixed contact assembly, an arc chamber comprising a plurality of substantially parallel arc-breaking plates made entirely of a ferromagnetic material being position in said arc extinguishing area, said arc chamber further comprises at least one arc-breaking plate which is at least partially made of a ceramic material and is substantially parallel to the plurality of arc-breaking plates made of the ferromagnetic material, said arc chamber further comprising at least one arc-breaking plate which is entirely made of the ceramic material.

2. The low-voltage circuit breaker, according to claim 1, wherein said arc chamber comprises a plurality of arc-breaking plates which are at least partially made of a ceramic material.

3. The low-voltage circuit breaker, according to claim 1, wherein said arc-breaking plate at least partially made of a ceramic material has a peripheral region made of a ferromagnetic material and a central region made of a ceramic material.

4. The low-voltage circuit breaker, according to claim 1, wherein said at least one arc-breaking plate which is at least partially made of a ceramic material is positioned in a zone of said arc extinguishing area proximate to said fixed contact assembly.

5. The low-voltage circuit breaker, according to claim 1, further comprises a plurality of arc-breaking plates at least partially made of a ceramic material which are positioned in a zone of said arc extinguishing area proximate to said fixed contact assembly.

6. The low-voltage circuit breaker, according to claim 1, wherein said at least one arc-breaking plate which is at least partially made of a ceramic material comprises a frame made of a ferromagnetic material and a core made of a ceramic material, said core of ceramic material being fitted inside said frame of ferromagnetic material so as to match its internal profile.

7. The low-voltage circuit breaker, according to claim 6, wherein said core made of a ceramic material is provided with one or more tabs engaging corresponding recesses formed in the internal profile of said frame made of a ferromagnetic material.

8. The low-voltage circuit breaker, according to claim 6, wherein said at least one arc-breaking plate which is at least partially made of a ceramic material comprises a core made of a ceramic material which is fitted inside a first and a second adjacent frames made of a ferromagnetic material so as to match the internal profiles of said first and second adjacent frames made of a ferromagnetic material.

9. The low-voltage circuit breaker, according to claim 1, wherein said arc chamber comprises a plurality of substantially parallel plates made of a ferromagnetic material and at least one arc-breaking plate which is at least partially made of a ceramic material inserted into an enclosure made of insulating material positioned in said arc extinguishing area.

10. The low-voltage circuit breaker, according to claim 2, wherein said arc-breaking plate at least partially made of a ceramic material has a peripheral region made of a ferromagnetic material and a central region made of a ceramic material.

11. The low-voltage circuit breaker, according to claim 2, wherein said at least one arc-breaking plate which is at least partially made of a ceramic material is positioned in a zone of said arc extinguishing area proximate to said fixed contact assembly.

12. The low-voltage circuit breaker, according to claim 3, wherein said at least one arc-breaking plate which is at least partially made of a ceramic material is positioned in a zone of said arc extinguishing area proximate to said fixed contact assembly.

13. The low-voltage circuit breaker, according to claim 2, further comprises a plurality of arc-breaking plates at least partially made of a ceramic material which are positioned in a zone of said arc extinguishing area proximate to said fixed contact assembly.

14. The low-voltage circuit breaker, according to claim 3, further comprises a plurality of arc-breaking plates at least partially made of a ceramic material which are positioned in a zone of said arc extinguishing area proximate to said fixed contact assembly.

15. The low-voltage circuit breaker, according to claim 2, wherein said at least one arc-breaking plate which is at least partially made of a ceramic material comprises a frame made of a ferromagnetic material and a core made of a ceramic material, said core of ceramic material being fitted inside said frame of ferromagnetic material so as to match its internal profile.

16. The low-voltage circuit breaker, according to claim 15, wherein said core made of a ceramic material is provided with one or more tabs engaging corresponding recesses formed in the internal profile of said frame made of a ferromagnetic material.

17. The low-voltage circuit breaker, according to claim 7, wherein said at least one arc-breaking plate which is at least partially made of a ceramic material comprises a core made of a ceramic material which is fitted inside a first and a second adjacent frames made of a ferromagnetic material so as to match the internal profiles of said first and second adjacent frames made of a ferromagnetic material.

Description

(1) Further features and advantages of the present invention will be more clear from the description of preferred but not exclusive embodiments of the low-voltage power circuit breaker of the present invention, shown by way of examples in the accompanying drawings, wherein:

(2) FIG. 1 is a perspective view of a low voltage power circuit breaker, according to the invention;

(3) FIG. 2 is an exploded view of a pole of a low voltage power circuit breaker, according to the invention;

(4) FIG. 3 is a first perspective view of a pole of a low voltage power circuit breaker, according to the invention;

(5) FIG. 4 is a second perspective view of a pole of a low voltage power circuit breaker, according to the invention;

(6) FIG. 5 is a perspective view of a first embodiment an arc-breaking plate for an arc chamber in a pole of a low voltage power circuit breaker, according to the invention;

(7) FIG. 6 is a perspective view of a second embodiment an arc-breaking plate for an arc chamber in a pole of a low voltage power circuit breaker, according to the invention;

(8) FIG. 7 is a perspective view of a third embodiment an arc-breaking plate for an arc chamber in a pole of a low voltage power circuit breaker, according to the invention;

(9) FIGS. 8a-8e are plan views of various embodiments of ceramic plates for an arc chamber in a pole of a low voltage power circuit breaker, according to the invention.

(10) With reference to the attached figures, the low voltage power circuit breaker of the present invention, designated by the reference numeral 1, in its more general definition, comprises one or more electrical poles 10.

(11) In the attached figure a pole of an air insulated switch is shown for exemplary purposes. However, the present invention is of more general applicability and can be used also in other kind of switches, such as molded case circuit breakers (MCCB) or low voltage switching device in which the arching phenomena need to be taken into account.

(12) With particular reference to FIGS. 2-4, a typical pole 10 of the circuit breaker 1 has an internal space delimited by an enclosure which, in the embodiment shown, is made of two half-enclosures coupled to each other.

(13) Within said internal space of the pole 10, there is a contact area 11 and an arc extinguishing area 12, located proximate to said contact area 11. A fixed contact assembly 21 and a movable contact assembly 22 are respectively positioned in said contact area 11, said movable contact assembly 22 being movable between a closed position in which it is into contact with said fixed contact assembly 21 and an open position in which it is spaced apart from said fixed contact assembly 21. The set-up of a pole of circuit breaker of this kind is well known in the art and will not be described with further details.

(14) Inside the internal space of the pole 10 there is also an arc chamber 30 positioned in said arc extinguishing area 12. According to embodiments well known in the art, the arc chamber 30 typically comprises a plurality of substantially parallel arc-breaking plates 31 made of a ferromagnetic material which are positioned in said arc extinguishing area 12.

(15) One of the distinguishing features of the low-voltage circuit breaker of the present invention is given by the fact that said arc chamber 30 further comprises at least one arc-breaking plate 32 which is at least partially made of a ceramic material.

(16) Indeed, the number of arc-breaking plates 32 comprising a ceramic material used in the arc chamber 30 can be selected according to the needs and cost/performance consideration, being possible to use in the arc chamber 30 only one (or a limited number) of such plates or a plurality of them.

(17) Even if it is possible to use in the arc chamber 30 of the circuit breaker 1 of the present invention one or more arc-breaking plates which are entirely made of a ceramic material, it is largely preferred to use one or more arc-breaking plates which comprise portions made of a ceramic material and portions made of a ferromagnetic material.

(18) In this respect, with reference also to FIG. 5-8, in largely preferred embodiments of the low-voltage circuit breaker 1 of the present invention, the arc-breaking plates 32, 33, 34, 35 at least partially made of a ceramic material have a peripheral region 330, 340, 350 which is made of a ferromagnetic material and a central region 335, 345, 355 which is made of a ceramic material. As previously explained the presence of both a metallic material and a ceramic material within the same plate allows combining in a synergic way the features and performances of the materials as far as magnetic, electrical, and thermal effects are concerned.

(19) In still a further preferred embodiment of the low-voltage circuit breaker 1 of the present invention, the one or more arc-breaking plates 32, 33, 34, 35 at least partially made of a ceramic material are conveniently concentrated in a zone of said arc extinguishing area 12 which is proximate to said fixed contact assembly 21. Indeed the plates positioned in such zone are those subjected for more time to the arc effect and it is therefore preferable to have a relatively high number of arc-breaking plates 32, 33, 34, 35 comprising a ceramic material in a zone close to the fixed contact and the corresponding arc runner.

(20) With reference to FIGS. 5-7, in typical embodiments of the present invention, the arc-breaking plates 33, 34, 35 which are at least partially made of a ceramic material comprise a frame 330, 340, 350 made of a ferromagnetic material and a core 335, 345, 355 made of a ceramic material. The core 335, 345, 355 of ceramic material is fitted inside said frame 330, 340, 350 of ferromagnetic material so as to match its internal profile, thereby obtaining a mechanically stable assembly.

(21) The mechanical stability of the mixed plate assembly (i.e. frame made of a ferromagnetic material, core made of a ceramic material) can be further improved by providing, as shown in FIG. 5, the core 335 with one or more tabs 336, 337 engaging corresponding recesses 338, 339 formed in the internal profile of the frame 330 made of a ferromagnetic material.

(22) As shown in the attached figures, the shape and dimensioning of the frames 330, 340, 350 as well as of the cores 335, 345, 355, 81, 82, 83, 84, 85 can be designed according to the needs.

(23) In order to avoid troubles during manufacturing and assembly of the cores 335, 345, 355, 81, 82, 83, 84, 85, such cores preferably have a certain thickness which can be greater than the thickness of the corresponding frames 330, 340, 350.

(24) In such a case, with reference to FIGS. 5 to 7, said at least one arc-breaking plate 33, 34, 35 which is at least partially made of a ceramic material comprises a core 335, 345, 355 made of a ceramic material which is fitted inside a first 331, 341, 351 and a second 332, 342, 352 adjacent frames made of a ferromagnetic material so as to match the internal profiles of said first 331, 341, 351 and second 332, 342, 352 adjacent frames made of a ferromagnetic material.

(25) In other words, the core 335, 345, 355 of ceramic material is thicker than the frame of metallic material and is fitted inside two superimposed 331-332; 341-342; 351-352 adjacent, metallic frames. This solution allows avoiding the use of ceramic plates too thin and possibly brittle that may create some trouble their manufacturing and assembly processes and brings about a final assembly which is solid and mechanically stable.

(26) In a typical embodiment of a low-voltage circuit breaker 1 of the present invention, said arc chamber 30 advantageously comprises a plurality of substantially parallel plates 31 which are made of a ferromagnetic material and one or more arc-breaking plate 32, 33, 34, 35 which are at least partially made of a ceramic material. The assembly of the metallic plates 31 and ceramic-containing plates 32, 33, 34, 35 is inserted into an enclosure 60 which is made of insulating material, said enclosure 60 being in turn positioned in the arc extinguishing area 12 of the pole 10 according to known industrial embodiment.

(27) It is clear from the above description that the low voltage power circuit breaker of the present invention, fully achieve the intended aims and solved the above-highlighted problems of the existing electrical cabinets.

(28) In practice, as previously explained, in the low voltage power circuit breaker of the present invention, the particular set of the plates in the arc-breaking plates assembly allows to better withstanding the electrical and magnetic effects arising during the formation of an electrical arc in the arc chambers and at the same time to guarantee better insulation and reduce ablation of the solid surfaces with respect to the arc chambers of known type.

(29) In particular, it has been experimentally seen that by using an arc chamber with a combination of metallic and ceramic plates the electrical and magnetic effects of the conventional metallic plates were substantially maintained while the thermal performances were greatly improved with respect to the conventional arc chambers.

(30) Several variations can be made to the low voltage power circuit breaker thus conceived, all falling within the scope of the attached claims. In practice, the materials used and the contingent dimensions and shapes can be any, according to requirements and to the state of the art.