FR2739972A1 - ELECTRICAL CIRCUIT BREAKER WITH INSULATING GAS AND SELF-EXPANSION - Google Patents

Abstract

An electric circuit breaker has a gas-expanding interrupter chamber 34 enclosing separable arcing contacts and an electromagnetic coil 122 for rotating the arc. An insulating support arm 62 is fixed to the end of the cartridge 43 and comprises a base (108) fixed to a first internal shoulder 110 of the cartridge 43 by screws 111. A heat shield 114 is placed on the base 108 for play the role of flame arrester. The excitation of the coil 122 takes place through a part of the magnetic circuit 138.

Description

ELECTRICAL CIRCUIT BREAKER WITH INSULATING GAS AND SELF-EXPANSION

  The invention relates to a medium-voltage electrical circuit breaker housed in an insulating envelope filled with a gas of high dielectric strength, and containing a cartridge shaped as a self-expanding breaking chamber comprising: - a fixed arcing contact cooperating with a movable arcing contact, - an electromagnetic coil arranged around the fixed arcing contact to generate a magnetic field in the cut-off interval after switching the arc on an electrode, - and a support arm of insulating material fixed to one end of the cartridge and fitted

  a bushing bushing for guiding the movable arcing contact.

  During a short-circuit current cut, the thermal action of the arc inside _5 the cartridge can cause significant gas formation due to the presence of the gas-forming plastic material of the support arm. Part of this gas can enter the cartridge,

  which disrupts the self-expanding effect, with a risk of re-striking the arc.

  The object of the invention is to improve the breaking performance of a circuit breaker

autoexpansion.

  The circuit breaker according to the invention is characterized in that - the support arm comprises a base fixed to a first internal shoulder of the cartridge by fixing means, - and a heat shield surrounds the guide bush, and is supported on the base and a second shoulder of the cartridge to limit the heating of the plastic material of the base following the thermal action of the arc, and to serve as a flame arrester, the hot gases being expelled towards the volume of the envelope through exhaust ports

in the base.

  The heat shield is formed by a polytetrafluoroethylene plate, held in place against the base by means of a stop ring mounted coaxially around the guide sleeve. The presence of this plate prevents the introduction of the gas-generating flow into the

  cartridge, which facilitates the extinction of the arc.

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  According to a characteristic of the invention, the arc capture electrode is coplanar with an annular contact track for rotating the arc, said track being connected to the front face of the coil. The opposite end of the coil is connected to a stud

  current supply via a magnetic circuit.

  To reinforce the magnetic field in the cut-off interval, the excitation of the coil is carried out through a ferromagnetic plate of a magnetic circuit, said plate being

  in electrical connection with the conductive cartridge.

  To resist the phenomenon of load shedding due to electrodynamic forces, the terminal turns of the coil are fixed individually by auxiliary screws respectively

  to the magnetic circuit and to the contact track.

  According to a preferred embodiment, the arcing contacts form a telescopic arrangement, and spring blades bear on the contact fingers associated with the fixed arcing contact and the socket, to ensure the contact pressure when the contact d 'bow

  mobile is engaged inside the fixed arcing contact in the closed position.

  The switching of the arc on the electrode is facilitated by an adjustable support member, comprising a metal washer with notches for the adjustment of the axial clearance between

  the end of the fixed arcing contact and the electrode.

  Other advantages and characteristics will emerge more clearly from the description which follows.

  follow an embodiment of the invention, given by way of nonlimiting example, and shown in the accompanying drawings, in which: - Figure 1 is a sectional view of the circuit breaker equipped with the breaking chamber according to invention, - Figure 2 shows a sectional view of the breaking chamber according to Figure 1, the movable arcing contact not being shown, - Figure 3 is a partial view on an enlarged scale of Figure 2, showing the different operating phases during the opening stroke of the movable arcing contact, - Figure 4 shows a detailed view of the coil, showing the connection of the terminal turns. In FIG. 1, a pole of a three-pole medium-voltage circuit breaker 10 is housed in a sealed insulating jacket 12 filled with a gas of high dielectric strength, in particular of

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  sulfur hexafluoride SF6. The pole includes a pair of bushings 14, 16 arranged in

  current supply ranges for supplying the circuit breaker.

  The bushings 14, 16 are directly connected to a disconnecting member 18 of the main circuit 19, comprising inside the casing 17 a fixed main contact 20 secured to the internal end of the first bushing 14 by screws 21, and a movable main contact 22 pivotally mounted on an axis 24 of a first support bracket 26,

  which is secured to the second crossing 16 by fixing screws 28.

  The casing 12 has a flange 29 closed by a cover 30 with the interposition of a seal 32. Inside the casing 12 is an auxiliary circuit with breaking chamber 34 containing a pair of contacts of arc 36, 38, one of which 38 is movable in longitudinal sliding between a closed position where it is in engagement with the fixed arcing contact 36, and an open position for separating the contacts

arc 36, 38.

  The arcing contacts 36, 38 of the breaking chamber 34 are electrically connected by a connecting conductor 40 and a braid 42, respectively at the bushings 14 and 16, so as to constitute a parallel mounting. In the closed position, the arcing contacts

  36, 38 ensure the shunting of the main contacts 20, 22.

  The interrupting chamber 34 is formed by a cartridge 43 of a self-expanding and arc-extinguishing extinguishing device, said cartridge communicating with the internal volume.

  of the casing 12 through the movable arcing contact 38 tubular.

  The actuation of the movable main contact 22, and of the movable arcing contact 38 is effected by means of a rotary shaft 44, sealingly traversing the wall of the casing 12 while being coupled outside to a control (not shown). Inside of

  the casing 12, the shaft 44 carries a crank 46 at each pole.

  The crank 46 is connected to the main movable contact 22 by a first link 48, and to the movable arcing contact 38 by a second link 50. The articulation of the links 48 takes place at a point 51 of the crank 46, l 'assembly being arranged to close the arcing contacts 36, 38 before the main contacts 20, 22, and open the arcing contacts 36,

  38 after the main contacts 20, 22.

  The interrupting chamber 34 comprises a lower support arm 62, extending perpendicular to the longitudinal axis of the cartridge 43 and the end of which is equipped

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  an axis 64 of articulation. The cartridge 43 is also provided with a pair of studs

  attachment 66 located opposite the arm 62 in the longitudinal direction.

  The articulation axis 64 of the support arm 62 is engaged in a U-shaped notch s in an extension of the bracket 26 for supporting the movable main contact 22. The intermediate part of the connecting conductor 40 is interposed between each pad 66 and a shoulder of the casing 12, and the end pad of the conductor 40 is connected to the main circuit by the screws 21 for fixing the fixed main contact 20 to the bushing 14. In contrast, the braid 42 for connection is connected to an intermediate conductor 82 having a range

  end plated on the base of the bracket 26 by means of the screws 28.

  Referring to Figure 2, the metallic cartridge 43 of the cutting chamber 34 has a cover 100 attached to a cylindrical wall 102 by fixing screws

  104. The cover 100 and the wall 102 are preferably made of an aluminum alloy.

  is the insulating support arm 62 adapts to the lower part of the wall 102 is equipped with a cylindrical guide bush 106, and a base 108 fixed to a first internal shoulder of the wall 102 by screws 111. A tubular brass insert 112 is arranged at

  inside the sleeve 106, and is slidably traversed by the movable arcing contact, 38.

  The support arm 62 is produced by molding an insulating material, in particular based on

polycarbonate.

  A heat shield 114 formed by a polytetrafluoroethylene plate, surrounds the guide sleeve 106 and is placed on the base 108 and a second shoulder 116 coplanar with the wall 102. Maintaining the screen 114 against the base 108 s effect by means of a stop ring 118 mounted coaxially around the sleeve 106. The underside of the heat shield 114 communicates with the internal volume of the envelope 12 through

  orifices 120 augularly distributed around the sleeve 106.

  Opposite the socket 106 is the fixed arcing contact 36 and coil 122 assembly.

  electromagnetic for rotating the arc.

  The presence of the heat shield 114 inside the cutting chamber 34 limits the heating of the plastic material of the base 108 of the support arm 62 following the thermal action of the arc resulting from the cutting. a strong current between the arcing contacts 36, 38. The screen 114 also serves as a flame arrester preventing any propagation of ionized gases generated in the breaking chamber 34 towards the outside of the cartridge 43. The hot gases emitted at the level of the insulating base 108 are driven in the direction of the arrow F s 2739972 through the exhaust orifices 120 and cannot penetrate inside the

cartridge 43.

  Referring to Figure 3, the fixed arcing contact 36 is arranged inside the annular coil 122 and is shaped according to a clamp having a plurality of contact fingers 124 mounted in a groove 125 of a support member 126 fixed to cover 100 by a screw

fixing 128.

  The support member 126 is made of conductive metallic material, in particular of stamped copper and is provided with a washer 130 with notches for adjusting the axial clearance between the end

  of the fixed arcing contact 36 and the arc sensing electrode 132.

  The electrode 132 is coplanar with the contact track 134 attached to the front face of the coil 122, and is used to excite the coil 122 at the start of the opening stroke of the movable arcing contact 38. The coil 122 comprises a stack of conductive turns 136 electrically connected in series, said coil being connected on the opposite side of the track

134 to a magnetic circuit 138.

  The magnetic circuit 138 comprises a plate 140 made of ferromagnetic material, for example steel, inserted between the side wall 102 of the cartridge 43 and the cover 100, and a cylindrical socket 142 arranged coaxially between the fixed arcing contact 36 and the coil 122. Assembly screws, one of which 144 is shown in FIG. 3, pass through the turns 136 of the coil 122 and the contact track 134 to secure the coil 122 to the plate 140 of the magnetic circuit 138. An insulating sleeve 145 is interposed between the coil

  122, and the fixed arcing contact 36 and socket 142 assembly.

  Spring blades 146 bear on the contact fingers 124 and the socket 142 to ensure contact pressure when the movable arcing contact 38 is engaged with the fixed arcing contact 36 in the closed position A. During the appearance of a short-circuit current, the flow of current in the cartridge 43 after opening of the main circuit 19 takes place as follows, with reference to FIG. 3: In the closed position A, the current enters by the fixing stud 66, and circulates in the contact fingers 124 after passing through the connecting conductor 40 and the cover 100. After the passage through the fixed and movable arc contacts 36 and 38, the current goes to the

  crossing 16 via the braid 42 (see FIG. 1).

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  At the start of the opening stroke (position B), the arc is switched to

  the electrode 132 authorizing the excitation of the coil 122.

  In position C, the fixed arcing contact 36 is no longer traversed by the current, the latter circulating entirely in the coil 122 which generates a magnetic field in the cut-off interval for the rotation of the arc on the contact track 134. The current is brought to the coil 122 through the cover 100 conductor and the plate 140 of the magnetic circuit 138. This results in an increase in the magnetic field in the interval of

  breaking, and rapid extinction of the arc.

  In position D, the movable arcing contact 38 is in the open position after

extinction of the arc.

  With reference to FIG. 4, the terminal coils 136 of the coil 122 are individually fixed by auxiliary screws 150, 152, respectively to the plate 140 and to the contact track 134. The connection of the additional screws 150, 152 guarantees good mechanical resistance of the electromagnetic coil 122 despite the presence of forces

  electrodynamics of repulsion generated at the extreme turns.

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Claims (10)

  1. Medium-voltage electric circuit breaker housed in an insulating envelope (12) filled with a gas with high dielectric strength, and containing a cartridge (43) shaped as a self-expanding breaking chamber (34) comprising: - a contact fixed arc (36) cooperating with a movable arcing contact (38), - an electromagnetic coil (122) arranged around the fixed arcing contact (36) to generate a magnetic field in the cut-off interval after switching of the arc on an electrode (132), and a support arm (62) made of insulating material fixed to one end of the cartridge (43) and equipped with a bushing (106) for crossing for guiding the movable arcing contact (38), characterized in that - the support arm (62) comprises a base (108) fixed on a first shoulder (110) internal to the cartridge (43) by fixing means (111), - and a heat shield (114) surrounds the guide sleeve (106), and is supported on the base (108) and a second th shoulder (116) of the cartridge (43) to limit the heating of the plastic material of the base (108) following the thermal action of the arc, and to serve as a flame arrester, the hot gases being expelled towards the volume of the envelope   (12) through exhaust orifices (120) formed in the base (108).   2. Circuit breaker according to claim 1, characterized in that the thermal screen (114) is formed by a polytetrafluoroethylene plate, held in place against the base (108) by means of a stop ring (118) mounted coaxially around the guide sleeve 106.   3. Circuit breaker according to claim 1, characterized in that the arc sensing electrode 132 is coplanar with an annular contact track 134 for rotating the arc, said track being connected to the front face of the coil (122) and that the opposite end of the coil (122) is connected to a current supply stud (66) via a magnetic circuit (138).   4. Circuit breaker according to claim 3, characterized in that the magnetic circuit (138) comprises a plate 140 of ferromagnetic material in connection with the cartridge 43 in conductive material. 8 2739972   5. Circuit breaker according to claim 4, characterized in that the plate 140 of the magnetic circuit is interposed between the side wall (102) of the cartridge (43) and a cover   serving as a support for the fixed arcing contact (36) and coil (122) assembly.   6. Circuit breaker according to claim 3 or 4, characterized in that the coil (122) is constituted by a stack of conductive turns 136, secured to the magnetic circuit (138) by assembly screws (144), the terminal turns the coil (122) being individually fixed by auxiliary screws (150, 152) respectively to the magnetic circuit   (138) and to the contact track (134).   7. Circuit breaker according to claim 4, characterized in that the magnetic circuit (138) further comprises a cylindrical socket (142) arranged coaxially between the arcing contact fixed (36) and the coil (122).   8. Circuit breaker according to claim 7, characterized in that a sleeve (145) of insulating material radially separates the coil (122) from the fixed arcing contact (36) and socket assembly. (142).   9. Circuit breaker according to claim 7 or 8, characterized in that spring blades (146) bear on the contact fingers (124) associated with the fixed arcing contact (36) and the socket (142), to ensure contact pressure when the movable arcing contact (38) is   engaged inside the fixed arcing contact (36) in the closed position.   10. Circuit breaker according to one of claims 1 to 9, characterized in that the arcing contact   fixed (36) is connected by the contact fingers (124) to a directional support member 126, comprising a metal washer (130) with notches for adjusting the axial play between   the end of the fixed arcing contact (36) and the electrode 132.