Title of Invention

AN EXTINGUISHING CHAMBER OF A CIRCUIT BREAKER WITH SELF- EXTINGUISHING EXPANSION, AND ROTATING ARC

Abstract

An extinguishing chamber of a circuit breaker with self-extinguishing expansion in SF6 comprises a stationary contact device 16 operating in conjunction with a movable contact, and a coil 18 for rotation of the arc on an annular track 32. The stationary contact device 16 is coaxially surrounded by the cylindrical coil 18 and comprises a plurality of contact fingers 42 circumferentially arranged to confine a hollow space receiving the movable contact 14, each contact finger 42 comprising a composite metallic structure having: -a copper main body 52 shaped as a cylindrical sector for flow of the permanent current in the closed position of the movable contact 14, -an electrode 54 made of refractory conducting material, brazed onto the front end of the body 52 to constitute a stationary arcing contact arranged near to the arc rotation track 32, -and a segment 58 made of ferromagnetic material brazed onto the periphery of the electrode 54 and of a part of the body 52 to obtain optimum guiding of the arc on the track 32.

Full Text

The invention relates to an extinguishing chamber for a circuit breaker with self-extinguishing expansion and rotating arc. The extinguishing chamber for a high voltage circuit breaker isolated by a high dielectric strength gas, and equipped with an arc extinguishing device by self-expansion of the gas. In know extinguishing chambers of the kind mentioned, flow of the rated current generally takes place in a main circuit equipped with stationary and movable main contacts which separate before the arcing contacts open, and which close after the arcing contacts have closed. The main circuit is formed by a circuit independent from the arcing circuit and is arranged either coaxially around the coil or offset laterally with respect to the arcing circuit (in particular described in the document EP-A-768,692). The complex architecture of such an extinguishing chamber of the circuit breaker is not suited to a sub-station requiring small dimensions. In the circuit breaker of the document US-A-4,431,886, the coil is permanently excited by the rated current when the contacts are closed. The object of the invention is to achieve an improved extinguishing chamber for a self-extinguishing expansion circuit breaker able to be housed in a compact sub-station. An extinguishing chamber for a circuit breaker with self extinguishing expansion and rotating arc, said chamber comprising: an enclosure made of insulting material containing a stationary contact device operating in conjunction with a movable contact arranged at the end of a conducting tube, which passes with sliding through one of the panels of the enclosure moving between a closed position and an open position of the contacts, an electromagnetic coil for rotation of the arc on the contact track situated on the front face of the coil, said coil being securedly affixed to the stationary contact device to form an overhanging module on the opposite panel of the enclosure, means for the chamber to communicate with the external volume of the enclosure when self-expansion of the gas takes place after the contacts have separated, the stationary contact device being coaxially surrounded by the cylindrical coil, and comprising a plurality of contact fingers arranged circumferentially to confine a hollow space receiving the movable contact, characterized in that each contact finger of the stationary contact device comprises a composite metallic structure comprising: a copper main body shaped as a cylindrical sector for flow of the permanent current in the closed position of the movable contact, an electrode made of refractory conducting material, brazed onto the front end of the body to constitute a stationary arcing contact arranged near to the arc rotation track, and a segment made of ferromagnetic material brazed onto the periphery of the electrode and of a part of the body, said segment being located inside the coil to obtain optimum guiding of the arc on the track. The combined operation of the composite structure of the stationary contact device as main contact and arcing contact, in the internal dimensions of the coil enables a very compact extinguishing chamber to be obtained. According to a preferred embodiment, the electrode is made of a cupro-tungsten alloy base and the segment is made of steel. The electrode and the segment of each contact finger are separated from the contact track by an axial gap of small thickness, enabling switching of the arc for excitation of the coil when the moveable contact separates from the electrode. Each contact finger is provided with a rear edge mounted with latching on a centring part of a current conducting stud. According to one feature of the invention, the coil is connected to the stud by copper support arms forming spacers separated from the contact fingers by insulating pads. A spring in the form of a curved blade is inserted between each insulating pad and the corresponding contact finger. Other advantages and features will become more clearly apparent from the following description of an embodiment of invention given as a non-restrictive example only and represented in the accompanying drawings in which: - Figure 1 is a cross sectional view of the extinguishing chamber according to the invention, represented in the closed position of the contact; - Figure 2 is an identical view to figure 1, respectively when separation of the contacts takes place (broken lines) and in the open position (bold lines); - Figure 3 is a perspective view of the pre-mounted coil and stationary contact device module; - Figure 4 shows an elevational view of figure 3; - Figure 5 is a cross sectional view along the line 5-5 of figure 4; - Figure 6 shows a perspective view of an elementary contact finger of the stationary contact device; - Figure 7 is a top view of a contact finger; - Figure 8 shows a cross sectional view along the line 8-8 of figure 7; - Figure 9 is a cross sectional view along the line 9-9 of figure 7. In figures 1 and 2, an extinguishing chamber 10 for a pole of a high voltage circuit breaker of the self-extinguishing expansion type comprises an enclosure 12 made of insulating material and filled with a high dielectric strength gas, notably sulphur hexafluoride SF6. The internal volume of the extinguishing chamber 10 contains a tubular movable contact 14 operating in conjunction with a stationary contact device 16 associated to an electromagnetic coil 18 for rotation of the arc. The movable contact 14 is located at the end of an elongate tube 20 made of conducting material, which is able to slide tightly through one of the panels 22 of the insulating enclosure 12. The external end of the tube 20 is coupled to an operating mechanism (not represented) designed to move the movable contact 14 between a closed position (figure 1) and an open position (figure 2). The stationary contact device 16 is extended by a conducting stud 24 of cylindrical shape passing through the opposite panel 26 in the longitudinal direction of the enclosure 12, and connected to the outside by the connection strip 28 of the pole. The hollow tube 20 enables the extinguishing chamber 10 to communicate with the external volume of the enclosure 12 as soon as the contacts 14, 16 separate to enable self-expansion of the gas. The insulating enclosure 12 is formed by abutment of two half-shells 12A, 12B each made by moulding from a polymer resin having a good mechanical strength and thermal resistance. With reference to figures 3 to 5, the electromagnetic coil 18 used for extinguishing the arc comprises an axial stacking of copper conducting turns 18A adjoined to one another and electrically connected in series by means of fixing screws 30 with interposed intercalated parts 18B made of insulating material. The front face 31 of the coil 18 is provided with an arc migration track 32, said track 32 of annular shape having an internal diameter slightly greater than the diameter of the movable contact 14. The rear turn 33 opposite the front face 31 is connected to the conducting stud 24 by support arms 34 constituting copper spacers, which are separated from the internal stationary contact device 16 by insulating pads 36. Two steel washers 38, 40 are fixed by screws 30 to the rear face of the coil 18, with interposed insulating washers 41. The stationary contact device 16 of the self-extinguishing expansion circuit breaker comprises three contact fingers 42 in the form of circular sectors, circumferentially arranged to form a cylindrical hollow contact. The internal diameter of this hollow contact corresponds appreciably to the external diameter of the movable contact 14, so as to allow telescopic sliding, respectively at the beginning of opening travel and at the end of closing travel of the movable contact 14. Each contact finger 42 has associated thereto a spring 44 in the form of a curved blade, whose convex face bears on the insulating pad of the corresponding support arm 34. Centring of the three contact fingers 42 with respect to the longitudinal axis of the stationary contact device 16 is performed by means of edges 46 provided at the rear of the contact fingers 42 and mounted with latching on a centring shoulder 48 of the stud 24. The coil 18 surrounds the stationary contact device 16 coaxially with a small annular clearance, the pre-mounted assembly forming an overhanging module fixed to the panel 26 by means of a nut 50 accessible from the outside of the enclosure 12. The structure of the stationary contact device 16 inside the coil 18 is arranged to give it a two/ function of stationary main contact for flow of the permanent current and of stationary arcing contact in the separation and current switching phase in the coil 18. In figures 6 to 9, each contact finger 42 is made of a composite metallic structure formed by different materials assembled by brazing. The main body 52 of the contact finger 42 is made of copper and is shaped as a cylindrical sector for flow of the permanent current when the movable contact 14 is in the closed position. A cupro-tungsten electrode 54 is brazed onto the rear part of the body 52 situated opposite the latching edge 46. This electrode 54 performs the function of stationary arcing contact for protection of the stationary contact device 16 against the effects of the arc. The internal cylindrical part of the body 52 is connected to the electrode 54 by a curved intermediate part 56 making for ease of insertion of the movable contact 14 in the circuit breaker closing phase. A segment 58 made of steel or other ferromagnetic material is brazed onto the periphery of the electrode 54 of the body 52 to perform guiding of the arc and good distribution of the magnetic field generated by the coil 18 when the arc is switched onto the track 32. The axial length of the segment 58 is greater than that of the electrode 54 and extends up to the vicinity of the cylindrical part of the body 52. Operation of the extinguishing chamber 10 according to the invention is as follows : In the closed position (figure 1), the movable contact 14 is inserted in the stationary contact device 16 and is in engagement with the copper body 52 for flow of the permanent current, which can have a rated intensity of 630 A. The contact pressure is exerted by the springs 44 on the contact fingers 42, and the coil 18 is out of operation, since the whole of the current is flowing through the stud 24, the contact fingers 42, and the movable contact 14 of the tube 20. The striction forces enable a compensation effect to be obtained on the contacts to keep them closed. When a short-circuit current occur, the operating mechanism causes the tube 20 to slide upwards and the movable contact 14 to be withdrawn in the direction of the electrode 54. An arc arises as soon as the movable contact 14 separates from the electrode 54, which is separated from the track 32 by a small axial gap. Migration of the arc onto the track 32 then causes the current to flow in the coil 18 and support arms 34, with formation of a magnetic field causing high-speed rotation of the arc around the track 32. There is then no current flowing in the contact fingers 42. The temperature rise of the arc causes a pressure increase of the SF6 gas inside the enclosure 12, followed by a gas flow via the tube 20 to the expansion volume of the tank (not represented). Extinction of the arc takes place as soon as the arc is sufficiently cooled by the gas flow (figure 2). The combined operation of the stationary contact device 16 as main contact and arcing contact, within the internal dimensions of the coil 18. enables a very compact extinguishing chamber to be obtained at a low manufacturina cost. WE CLAIM: 1. An extinguishing chamber for a circuit breaker with self extinguishing expansion and rotating arc, said chamber comprising: an enclosure (12) made of insulting material containing a stationary contact device (16) operating in conjunction with a movable contact (14) arranged at the end of a conducting tube (20), which passes with sliding through one of the panels (22) of the enclosure (12) moving between a closed position and an open position of the contacts, an electromagnetic coil (18) for rotation of the arc on the contact track (32) situated on the front face of the coil (18), said coil being securedly affixed to the stationary contact device (16) to form an overhanging module on the opposite panel (26) of the enclosure (12), means for the chamber (10) to communicate with the extemal volume of the enclosure (12) when self-expansion of the gas takes place after the contacts have separated, the stationary contact device (16) being coaxially surrounded by the cylindrical coil (18), and comprising a plurality of contact fingers (42) arranged circumferentially to confine a hollow space receiving the movable contact (14), characterized in that each contact finger (42) of the stationary contact device (16) comprises a composite metallic structure comprising: a copper main body (52) shaped as a cylindrical sector for flow of the permanent current in the closed position of the movable contact (14), an electrode (54) made of refractory conducting material, brazed onto the front end of the body (52) to constitute a stationary arcing contact arranged near to the arc rotation track (32), and a segment (58) made of ferromagnetic material brazed onto the periphery of the electrode (54) and of a part of the body (52), said segment being located inside the coil (18) to obtain optimum guiding of the arc on the track (32). 2. The extinguishing chamber as claimed in claim 1, wherein the electrode (54) is made of a cupro-tungsten alloy base. 3. The extinguishing chamber as claimed in claims 1 or 2, wherein the segment (58) is made of steel. 4. The extinguishing chamber as claimed in claim 1, wherein the electrode (54) and the segment (58) of each contact finger (42) are separated from the contact track (32) by an axial gap of small thickness, enabling switching of the arc for excitation of the coil (18) when the movable contact (14) separates from the electrode (54). 5. The extinguishing chamber as claimed in claim 1, wherein each contact finger (42) is provided with a rear edge (46) mounted with latching on a centring part (48) of a current conducting stud (24). 6. The extinguishing chamber as claimed in claim 5, wherein the coil (18) is connected to the stud (24) by copper support arms (34) forming spacers separated from the contact fingers (42) by insulating pads (36). 7. The extinguishing chamber as claimed in claim 6, wherein a spring (44) in the form of a curved blade is inserted between each insulating pad (3 6) and the corresponding contact fingers (42). 8. The extinguishing chamber as claimed in claim 6, wherein the coil (18) is formed by axial stacking of conducting tums (18A) insulated from one another by insulating intercalated parts (18B), and that the rear face of the coil (18) opposite the track (32) is equipped with steel washers (38, 40), the assembly being secured by fixing screws (30). 9. The extinguishing chamber as claimed in claim 1, wherein the communication means are formed by the hollow tube (20) of the movable contact (14). 10. An extinguishing chamber for a circuit breaker with self extinguishing expansion and rotating arc substantially as described hereabove and illustrated with reference to the accompany drawings. Dated this 12 day of January 1999

Documents:

0046-mas-1999 abstract-granded.jpg

0046-mas-1999 abstract-granded.pdf

0046-mas-1999 claims-granded.pdf

0046-mas-1999 description (complete)-granded.pdf

0046-mas-1999 drawings-granded.pdf

46-mas-1999-abstract.pdf

46-mas-1999-claims .pdf

46-mas-1999-correspondance other.pdf

46-mas-1999-correspondance po.pdf

46-mas-1999-description complete.pdf

46-mas-1999-drawings.pdf

46-mas-1999-form 1.pdf

46-mas-1999-form 26.pdf

46-mas-1999-form 3.pdf

46-mas-1999-form 4.pdf