EP0580515B1 - Circuit breaker with two concentric arc chambers - Google Patents

Description

The invention relates to a self-blowing circuit breaker comprising a casing intended to be filled with a fluid for extinguishing an electric arc, a first closing element disposed inside the casing and defining a first chamber d thermal expansion, a second closure element disposed inside the first closure element and defining a second thermal expansion chamber, a first contact mounted sliding inside the envelope in an axial sliding direction to penetrate inside said first and second thermal expansion chambers in order to cooperate electrically with a second arcing contact which extends axially inside the second thermal expansion chamber, said blowing nozzles being superimposed concentric in this sliding direction to obtain their closure by the first movable arcing contact.

It applies in particular to high and medium voltage circuit breakers having a casing filled with a gas with good dielectric properties, in particular SF6 and which do not include either a blowing piston or a magnet.

Such a self-blowing circuit breaker comprising two thermal expansion chambers having different volumes to allow cutting of currents located in a large range of currents, for example electric currents going from 0 to 25000 amps, is known from document EP- A-150 079.

The object of the invention is to improve the performance of such a thermal expansion gas circuit breaker with two expansion chambers to more effectively cut small and large currents in a large range of electric currents.

To this end, the invention relates to a self-blowing circuit breaker according to one of claims 1 and 2.

The advantages obtained by the invention are as follows. The cutting element has a simple shape. The number of parts of the circuit breaker is reduced compared to conventional self-blowing circuit breakers having two expansion chambers. The circuit breaker according to the invention operates with a much lower control energy than devices having two movable contacts per pole. the circuit breaker operates for the entire current range from 0 to 25,000 amperes and beyond in certain cases.

• La figure 1 représente schématiquement un disjoncteur selon l'état de la technique, tel que connu du document EP-A-150 079, comprenant deux chambres d'expansion fixes et concentriques.
• La figure 2 représente schématiquement le disjoncteur selon l'invention à deux chambres d'expansion dont l'une est mobile par rapport à l'autre, le contact d'arc mobile étant en position enclenchée.
• La figure 3 représente schématiquement le disjoncteur de la figure 2, le contact d'arc mobile étant en position pour couper des petits courants.
• La figure 4 représente le disjoncteur de la figure 2, le contact d'arc mobile étant en position pour couper des grands courants.

Other characteristics and advantages of the invention will appear in the following description of an embodiment of the invention made with reference to the drawings.

• FIG. 1 diagrammatically represents a circuit breaker according to the state of the art, as known from document EP-A-150 079, comprising two fixed and concentric expansion chambers.
• FIG. 2 schematically represents the circuit breaker according to the invention with two expansion chambers, one of which is movable relative to the other, the movable arcing contact being in the engaged position.
• Figure 3 shows schematically the circuit breaker of Figure 2, the movable arcing contact being in position to cut small currents.
• Figure 4 shows the circuit breaker of Figure 2, the movable arcing contact being in position to cut large currents.

FIG. 5 represents another variant of the circuit breaker according to the invention.

In FIG. 1, the medium or high voltage circuit breaker comprises a sealed casing 1 filled with a dielectric gas, such as SF6, inside which is placed an electric arc breaking assembly.

The cut-off assembly comprises a first cylinder 2 delimiting a thermal expansion chamber having a volume V1 and having a blowing nozzle 3 for blowing the electric arc generated by large currents to be cut, a second cylinder 4 incorporated in the cylinder 2 and carrying a nozzle 5 for blowing the electric arc generated by small currents to be cut. The second cylinder 4 delimits a thermal expansion chamber having a volume V2 smaller than the volume V1. Preferably, the two cylinders have concentric sections (coaxial cylinders) to compact the cut-off assembly.

A first fixed arcing contact 6, electrically connected to a first outlet through the two cylinders 4 and 2, is placed inside the small cylinder 4 in the arcing zone. This first contact can be of the tulip type and has contact fingers 20.

Each cylinder 2.4 has a closed end connected to the casing and carrying the fixed arcing contact 6 and an open end carrying a blowing nozzle 3.5. The blowing nozzles 3,5 are superimposed and spaced from each other as visible in FIG. 1. They have substantially concentric gas passage sections (axially aligned). They are crossed by a single movable arcing contact 7 electrically connected to a second socket and mechanically to an operating member which causes it to slide inside the nozzles perpendicularly to their section to engage it between the fingers 20 of the fixed contact 6 or release it. Contacts 6 and 7 are aligned.

The movable contact 7 has an end portion 8 with a section complementary to that of the nozzle 5 for closing the latter and a middle portion 9 with a section complementary to that of the nozzle 3 for closing the latter. The nozzle 5 has a smaller gas passage section than that of the nozzle 3, the size of the nozzle sections being a function of the respective volumes of the expansion chambers.

The movable contact 7 further carries fingers 10 for the passage of the permanent current by establishing electrical contact with the exterior surface of the first cylinder 2.

As shown in FIG. 1, the movable contact 7 is engaged in the fixed contact 6. In the closed position, the current flows through the permanent contact fingers 10.

The circuit breaker works as follows. In the case where a small current passing through the breaking assembly must be cut, the circuit breaker operating member is actuated to move the movable contact 7. The passage of permanent current by the fingers 10 is interrupted at first then it there is switching of the arcing contacts 6 and 7 and an electric arc appears between them. The energy emitted by the electric arc causes a rise in pressure of the gas in the volume V2 by increasing the temperature and a gas circulation takes place between this volume and the volume V1 which plays the role of an expansion volume due to the pressure difference between these two volumes and the clearance of the nozzle 5 by the arcing contact 7 moving. The circulation of gas cuts off the electric arc when the current crosses zero.

In the case where a large current must be cut, the energy emitted by the arc causes a rise in pressure of the gas both in volume V1 and in volume V2 and a circulation of gas takes place in volumes V1 and V2 to the expansion volume V3 to blow the electric arc, the arcing contact 7 having also released the nozzle 3, at the end of the stroke.

Consequently, by simply sliding the movable contact 7 inside the nozzles 3 and 5, the electric arc can be blown for small and large currents to be cut.

The invention will now be described, with reference to FIGS. 2 to 5.

As shown in Figure 2, the small cylinder 4 is slidably mounted inside the large cylinder and carries a part 11 of the first contact 6, the other part 12 of the contact 6 connected to the first electrical outlet being fixed. This part 12 enters a cavity 17 arranged in the small cylinder and is electrically connected to the latter by accordion contacts 13. The large cylinder is connected by its closed end to the casing 1 by means of a third cylinder 15 having orifices 14 opening into the expansion volume V3 and into which the small cylinder 4 also slides.

When the movable arcing contact 7 is in the engaged position, the nozzle 5 remains in abutment on the nozzle 3 under the effect of a spring 16 in abutment on the wall of the envelope and exerting a pushing force on the small cylinder.

To cut small currents as shown in Figure 3, the small cylinder 4 remains in place and the gas flow shown schematically by an arrow takes place directly from the volume V2 to the expansion volume V3 subjected to a lower gas pressure than the volume V2 which improves the efficiency of the blowing of the electric arc. For large currents, the small cylinder 4 slides, under the effect of the pressure increase in the gas in volumes V1 and V2, inside the large cylinder 2 and the third cylinder 15 in the same direction as the sliding of the movable contact 7 and in the opposite direction as visible in FIG. 4 until it comes into abutment against the fixed part 12 of the arcing contact 6. The displacement of the small cylinder is caused by the rise in pressure of the gas due to the bow electric in volume V2. The displacement of the small cylinder 4 results in the separation of the nozzles 3 and 5. The gas circulation shown diagrammatically by two arrows then takes place from the volumes V1 and V2 towards the volume V3 as in the previous case. After switching off the current, the small cylinder 4 returns to the rest position under the action of the spring 16. This arrangement also makes it possible to reduce the travel of the movable arcing contact 7.

According to another variant as visible in FIG. 5, the first contact 6 is in a single fixed part and the small cylinder 4 slides inside the large cylinder 2 and along the first fixed contact 6. The first contact 6 has a shoulder 18 serving as a stop to stop the stroke of the small cylinder.

The nozzle 5 always rests on the nozzle 3 under the effect of the spring 16. The blowing of the electric arc generated by small currents to be cut is identical to the case of FIG. 3. In the case of large currents, the small cylinder slides inside the large cylinder 2 and of the third cylinder 15 under the effect of the pressure increase of the gas in the volumes V1 and V2 but the electric arc to be blown is not lengthened by the displacement of the small cylinder, the arcing contact 6 remaining fixed, which increases the efficiency of the electric arc blowing.

Claims (6)

1. A puffer circuit-breaker comprising, in a casing (1) which is intended to be filled with an electric arc extinguishing fluid, a first closure member (2) provided with a first blast nozzle (3) and defining a first thermal expansion chamber, a second closure member (4) provided with a second blast nozzle (5) and defining a second thermal expansion chamber, a first arcing contact (7) slidably mounted within the casing to slide axially so as to extend through said first and second thermal expansion chambers in order to cooperate electrically with a second arcing contact (6) which extends axially inside the second thermal expansion chamber, said blast nozzles (3, 5) being superimposed in concentric manner along said sliding direction in order to close them by the first moving arcing contact (7), the circuit-breaker being characterized in that:

   - the second closure member (4) is mounted for translational movement inside the first closure member (2) along said axial direction in which the first arcing contact (7) slides;

   - the second arcing contact (6) is mounted for movement inside the casing and fixed inside the second moving closure member (4); and

   - a resilient member (16) is provided to act on the second closure member (4) in order that the second blast nozzle (5) continues to bears on the first blast nozzle (3).
2. A puffer circuit-breaker comprising, in a casing (1) which is intended to be filled with an electric arc extinguishing fluid, a first closure member (2) provided with a first blast nozzle (3) and defining a first thermal expansion chamber, a second closure member (4) provided with a second blast nozzle (5) and defining a second thermal expansion chamber, a first arcing contact (7) slidably mounted within the casing to slide axially so as to extend through said first and second thermal expansion chambers in order to cooperate electrically with a second arcing contact (6) which extends axially inside the second thermal expansion chamber, said blast nozzles (3, 5) being superimposed in concentric manner along said sliding direction in order to close them by the first moving arcing contact (7), the circuit-breaker being characterized in that:

   - the second closure member (4) is mounted for translational movement inside the first closure member (2) along said axial direction in which the first arcing contact (7) slides;

   - the second moving closure member (4) slides along the second arcing contact (6) which is mounted stationary inside the casing; and

   - a resilient member (16) is provided to act on the second closure member (4) in order that the second blast nozzle (5) continues to bears on the first blast nozzle (3).
3. The circuit-breaker according to claim 1 or 2, in which the first blast nozzle (3) has a larger opening cross-section than that of the second blast nozzle (5).
4. The circuit-breaker according to claim 3, in which the first arcing contact (7) comprises a first portion (8) of cross-section complementary to that of the opening of the second blast nozzle (5) so as to close that nozzle, and a second portion (9) of cross-section complementary to that of the opening of the first blast nozzle (3) so as to close that nozzle.
5. The circuit-breaker according to claim 2, in which the second arcing contact (6) has a shoulder (18) to limit the movement of the second closure member (4) relative to the first closure member (2).
6. The circuit-breaker according to any preceding claim, in which said first and second closure members (2, 4) are cylinders of concentric cross-section.

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