EP0794545B1 - Vacuum switch or circuit breaker - Google Patents

Description

The present invention relates to an electric vacuum switch intended to ensure the break in an electrical circuit especially in low or medium voltage.

We know a circuit breaker as described in patent application FR-2,682,808 of the applicant comprising a vacuum interrupter in which are housed two arcing contacts, one of which is fixed, is secured to one of the bottoms while the other, mobile, is mounted to slide axially inside the cartridge between a closed position and a contact separation position causing the formation of an arc current. This circuit breaker further comprises a coil arranged coaxially outside the cartridge in line with the separation interval of the arcing contacts, this coil being intended to produce an axial magnetic field in the arcing region. One of the drawbacks of this type of circuit breaker is that the coil being in series with the arcing contacts, all of the main current flows through the coil. It follows that it is necessary to provide a coil of large section which therefore has a large footprint and generates considerable losses.
One of the solutions to this problem consists, as described in patent application No. 9413408 of the applicant, of interposing a bypass means between the two ends of the coil, said means being intended to derive part of the main current to through the coil during cutting, in order to create a reduced axial magnetic field and thus a reduced loss. However, in this embodiment, the heat losses remain significant.
We also know the document DE 39 14967 which describes a device according to the preamble of claims 1 and 2, and in which the means for producing the axial magnetic field comprises at least two turns each completely surrounding the envelope of the switch, where significant congestion and significant losses generated.

The present invention solves these problems and proposes a vacuum interrupter or circuit breaker, of particularly simple design, making it possible to further reduce these losses.

To this end, the subject of the present invention is an electrical switch intended to ensure breaking in an electrical circuit, of the type comprising an elongated cartridge under vacuum with a cylindrical envelope closed by two bottoms, in which two arcing contacts are intended intended for be electrically connected respectively to two power supply areas, one of which, fixed, is secured to one of the bottoms while the other, mobile, is mounted to slide axially inside the cartridge, and at least one means intended to produce an axial magnetic field in the zone of formation of the arc, this switch being characterized in that the aforesaid means comprises at least two portions of turn mounted in parallel around the contacts, each portion of turn forming a fraction of a coil of length less than a full turn and each comprising a first end electrically connected to one of the arcing contacts and a second extrem ity electrically connected to the current supply range of said contact, said portions being arranged outside the cartridge, in line with the separation interval of the arcing contacts.
The invention also relates to an electrical switch intended to ensure breaking in an electrical circuit, of the type comprising an elongated cartridge under vacuum with a cylindrical envelope closed by two bottoms, in which are housed two arcing contacts intended to be electrically connected respectively to two current supply ranges, one of which is fixed, is integral with one of the abovementioned bottoms while the other, mobile, is mounted to slide axially inside the cartridge, and at least one means intended to produce an axial magnetic field in the arc formation zone, this switch being characterized in that the aforementioned means comprises at least two portions of turn mounted in parallel around the contacts, each portion of turn forming a fraction of turn of length less than a full turn and each comprising a first end electrically connected to one of the arcing contacts and a second end electrically connected to the current supply range of said contact and in that the first and second ends of each portion of turn are electrically connected by means of bypass intended to divert part of the main current through the portions of turn, during the cut.
According to another characteristic, all of the combined turn portions form a complete loop.
According to a particular characteristic, the turns are two in number.
According to a particular embodiment, the turns portions as well as the bypass means M are mounted coaxially outside the cartridge.

According to another embodiment, the turns portions as well as the bypass means are mounted coaxially inside the cartridge.

According to another characteristic, the turns and the bypass means are mounted between the fixed arcing contact and the corresponding current supply range.

According to a particular embodiment, the turns portions as well as the bypass means are integral part of one or both of the arcing contacts.

Advantageously, the turns portions being two in number, the second end of one of the turns is superimposed on the first end of the other of the portions of turn.

According to another particular embodiment, the switch comprises a first bell comprising several portions of whorl electrically connected by one of their ends to the aforementioned range (or in arcing contact) and by their end opposite to a second bell conductor arranged coaxially to the cartridge and electrically connected to the arcing contact (or respectively to the aforementioned range).

Advantageously, the second bell also includes portions of a coil, the same number of turn portions than the first, electrically connected by one of their ends, respectively to the turns of the first bell and by their ends opposite to said arcing contact, the turns of the coil associated with the first and the second bell being arranged in relation to each other so as to cancel the components axial currents passing through the portions of turns.

According to another characteristic, the aforementioned bypass means comprises a resistive element and / or an inductive element mounted in parallel with the turns portions.

• La figure 1 est une vue en perspective, illustrant une ampoule à vide conforme à une réalisation particulière de l'invention,
• La figure 2 est une vue en perspective, illustrant l'une des portions de spire utilisée dans la réalisation de l'ampoule de la figure précédente,
• La figure 3 est une vue en perspective illustrant les deux portions de spires utilisées dans cette même réalisation et constituant le moyen de création du champ axial.
• La figure 4 est une vue en perspective illustrant l'un des contacts d'une ampoule conforme à une autre réalisation de l'invention,
• Les figures 5 et 6 sont des vues partielles illustrant en coupe axiale, deux autres réalisations d'un interrupteur à vide conforme à l'invention, et
• Les figures 7 et 8 illustrent respectivement une ampoule équipée de trois portions de spire montées en parallèle, et un tiers de spire.

However, other advantages and characteristics of the invention will appear more clearly in the detailed description which follows and refers to the appended drawings given solely by way of example and in which:

• FIG. 1 is a perspective view, illustrating a vacuum interrupter according to a particular embodiment of the invention,
• FIG. 2 is a perspective view, illustrating one of the turns portions used in the production of the bulb of the previous figure,
• Figure 3 is a perspective view illustrating the two portions of turns used in this same embodiment and constituting the means for creating the axial field.
• FIG. 4 is a perspective view illustrating one of the contacts of a bulb according to another embodiment of the invention,
• FIGS. 5 and 6 are partial views illustrating in axial section, two other embodiments of a vacuum interrupter according to the invention, and
• Figures 7 and 8 respectively illustrate a bulb equipped with three portions of turn mounted in parallel, and a third of turn.

In Figure 1, we see a vacuum switch I comprising a bulb (or cartridge) to vacuum C mainly constituted by a cylindrical envelope 1 closed by two bottoms opposite in which are housed two arcing contacts respectively fixed 4 and movable 5 (not visible in this figure, but visible in Figure 5). Fixed arcing contact 4 is secured to the bottom located at the top of the casing 1 while the arcing contact mobile 5 is slidably mounted through the other of the two bottoms.

This switch I also comprises a means intended to create an axial magnetic field between the contacts 4, 5 in order to obtain a diffusion of the arc. According to the realization of the invention illustrated in this figure, this means comprises two half-turns 2, 20 symmetrical such as that 2 illustrated in FIG. 2. These two half-turns 2, 20 are mounted outside of bulb C in line with the contact separation interval arc 4, 5, so as to form a complete loop. Each portion of coil 2, 20 is constituted by a half-turn having two ends 2a, 20a and 2b, 20b extending parallel to the bottoms of cartridge C.

These ends include a first end 2a, 20a, intended to be connected electrically at fixed contact 4, and a second end 2b, 20b, intended to be electrically connected to the area 19 (not shown in this figure) for supplying the current at the fixed arcing contact 4. As can be seen more particularly in FIG. 3, the first two ends 2a, 20a, associated respectively with the two portions of turns are of complementary shape and are arranged end to end, just like the two second ends 2b, 20b. Advantageously, a layer of insulating material 22 with a thickness of about 1mm is interposed between the first 2a, 20a and the second 2b, 20b, ends, said layer 22 extending to the bottom of the portions of coil 2, 20. The first ends 2a, 20a of portion of coil are connected electrically at the second ends 2b, 20b by a bypass means M mounted in parallel with said portions and constituted in this particular embodiment, by a stud 23 made of stainless steel. This means is intended to derive a part sufficient current through the coil portions 2, 20.

de courant qui créent un champ magnétique, le moyen de dérivation M permet d'ajuster le courant à des valeurs précises, ce qui permet de créer précisément le champ magnétique nécessaire en minimisant ainsi les pertes.While the turns allow to obtain fractions

of current which create a magnetic field, the bypass means M makes it possible to adjust the current to precise values, which makes it possible to precisely create the necessary magnetic field thereby minimizing losses.

In FIG. 7, the bulb is equipped with three thirds of a turn, which are once again symmetrical. A single piece is thus used (fig. 8) to make, after mounting several sectors, a complete turn.
Note also the self-locking effect of the sectors after mounting the stud 23, obtained thanks to the particular shape of the ends of the turns portions.

Referring to Figure 4, we see that according to another embodiment of the invention, the two aforementioned two half-turns 2, 20 are formed inside one of the 4 arc contact elements. Note that in this embodiment, the two contacts arc 4, 5 may advantageously be equipped with such portions of turns.

According to the invention, the bulb C is surrounded by several portions of turns. he as a result, currents can be created whose axial component is capable of produce unwanted magnetic fields in the radial direction, these fields having to repel the arc outside the space between the arcing contacts. In order to compensate these axial components, in the two embodiments previously described, the two ends 2a, 2b or 20a, 20b of each portion of coil 2, 20 are axially offset, and the two second ends 2b, 20b are superimposed respectively at the first two ends 20a and 2a.

According to another embodiment described in FIG. 5, the switch I comprises a first bell 14 comprising a number of portions of turns 18, for example seven.

These coil portions include an end electrically connected to a pad supplying current 19 to fixed contact 4 and one end electrically connected to a second conductive bell 15 mounted inside the first 14 and connected electrically in contact with a fixed arc 4, this second bell 15 realizing the compensation of the above-mentioned axial current components. Note that this second bell 15 can advantageously be an integral part of the envelope 1 of the bulb as shown in Figure 5, and be fixed to the first by brazing. Note also that this second bell 15 could also have been placed outside the first. In this embodiment, the bypass means M is constituted by a resistive element 6 in the form of disc interposed between the two aforementioned bells 14, 15.

According to another embodiment illustrated in FIG. 6, the switch I comprises, as in the previous embodiment, two coaxial bells 14, 16, electrically connected to their lower part, one of the outer 14 of which has connected turns 18 electrically at the current supply range 19 of the fixed arcing contact 4. However, in this realization, the compensation of the axial current components is obtained by the fact that the inner bell 16 also includes portions of coil 17, said portions 17 being located in the extension of the turns 18 of the bell external 14 and electrically connected to the fixed arcing contact 4. In this case, the portions of turns belonging to the two bells are arranged in relation to each other of so as to bring the current up so that the currents oriented in the direction axial cancel each other out. Thus, the ratio between the radial field and the axial field is reduced, whence it it follows that the effects of the above-mentioned axial current components are reduced.

The operation of a switch according to one or other of the abovementioned embodiments will be briefly described in the following with reference to the figures.

According to the embodiment illustrated in FIGS. 1 to 4 during cutting, a bypass of the current occurs through the coil portions 2, 20. This results in the creation of a field axial magnetic in the separation zone of the arcing contacts 4, 5. When using two turns, for a given section, each portion making a U-turn, we get a loss corresponding to 25% of that created in the event that all of the current passed through a full turn.

In general, for an effective breaking capacity of 25kA, it is advantageous to obtain an axial magnetic field corresponding to a current of 10kA passing through a turn. As a result, only 40% of the available current must pass through a turn surrounding the bulb completely.

With a single turn, and in the case where all the current crosses said turn, we obtain during the cut, an excessively large axial magnetic field; so during the passage of a permanent current of 1250 A, we create a loss of 68 Watts.

Using a full turn and bypass means, you can adjust the current that goes through the turn and you get exactly the desired axial magnetic field. However, during the passage of the permanent current of 1250 A, the losses are 34 Watts.

With a system consisting of two parallel turns and a bypass means, you can also adjust the bypass current (up to 40% of current flowing through the portions of turn. The loss during the passage of the permanent current is then reduced and reached only 17 Watts. In the latter case, the bypass means can be achieved by a simple stud that supports the two turns of the coil and the bulb, only 20% of the current passing through this stud, which further facilitates mounting.

According to the embodiments illustrated in FIGS. 5 and 6, the derivative current first passes to through the turns 18 of the first bell 14 and then through the second bell 15, 16 before crossing the arcing contacts 4, 5.

Note that an inductive shunt could just as easily have been used instead of a resistive shunt or a combination of an inductive shunt and a resistive shunt.

Claims (12)

1. Electrical switch designed to perform breaking in an electrical circuit, of the kind comprising an elongate vacuum cartridge C with a cylindrical envelope sealed off by two end plates, wherein there are housed two arcing contacts (4, 5) designed to be electrically connected respectively to two current input strips, a stationary one (4) of which is securedly affixed to one of the above-mentioned end plates whereas the other, movable, one (5) is fitted with axial sliding inside the cartridge (C), and at least one means (2, 20) designed to produce an axial magnetic field in the arc formation zone, said means comprising at least two portions of turn (2, 20) fitted in parallel around the contacts (4, 5), characterized in that each portion of turn forms a fraction of a turn of a length smaller than a complete turn and comprises a first end (2a, 20a) electrically connected to one (4) of the arcing contacts (4, 5) and a second end (2b, 20b) electrically connected to the current input strip (19) of said contact (4), said portions (2, 20) being arranged outside the cartridge C, facing the gap separating the arcing contacts (4, 5).
2. Electrical switch according to claim 1, characterized in that the first (2a, 20a) and second (2b, 20b) ends of each portion of turn (2, 20) are electrically connected by a branch-off means M designed to branch a part of the main current off through the portions of turn (2, 20) during breaking.
3. Switch according to claim 1 or 2, characterized in that all the portions of turn together form a full loop.
4. Switch according to any one of the claims 1 to 3, characterized in that the portions of turn (2, 20) are two in number.
5. Switch according to any one of the claims 2 to 4, characterized in that the portions of turn (2, 20) and the branch-off means M are fitted coaxially outside the cartridge C.
6. Switch according to any one of the claims 2 to 4, characterized in that the portions of turn (2, 20) and the branch-off means M are fitted coaxially inside the cartridge C.
7. Switch according to any one of the foregoing claims, characterized in that the portions of turn (2, 20) and the branch-off means M are fitted between the stationary arcing contact (4) and the corresponding current input strip (19).
8. Switch according to any one of the claims 1 to 4, characterized in that the portions of turn (2, 20) and the branch-off means M form an integral part of one or both of the arcing contacts (4, 5).
9. Switch according to any one of the foregoing claims, characterized in that the portions of turn being two in number, the second end (2b, 20b) of each portion of turn is superposed on the first end (2a, 20a) of the other of the portions of turn.
10. Switch according to any one of the foregoing claims, characterized in that it comprises a first bell-housing (14) comprising several portions of turn electrically connected via one of their ends to the above-mentioned strip (19) (or to the arcing contact (4)) and via their opposite end to a second conducting bell-housing (15, 16) arranged coaxially to the cartridge and electrically connected to the arcing contact (4) (or respectively to the above-mentioned strip (19)).
11. Switch according to claim 10, characterized in that the second bell-housing (16) comprises the same number of portions of turn (17) electrically connected via one of their ends respectively to the portions of turn (18) of the first bell-housing (14) and via their opposite end to said arcing contact (4), the portions of turn associated to the first (14) and to the second (16) bell-housing being arranged with respect to one another in such a way as to cancel out the axial components of the currents flowing in the portions of turns.
12. Switch according to any one of the claims 2 to 11, characterized in that the above-mentioned branch-off means comprise a resistive element and/or an inductive element fitted in parallel with the portions of turn (2, 20).

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