EP0095406B1 - Switch with rotating arc and permanent magnet - Google Patents

Description

• - une enveloppe étanche remplie de gaz isolant à rigidité diélectrique élevée,
• - une paire de contacts séparables et alignés selon la direction axiale de l'enveloppe,
• - un aimant permanent engendrant un champ magnétique dans la zone de séparation des contacts pour imposer une rotation de l'arc,
• - une paire de plages de raccordement de liaison électrique avec les contacts, lesdites plages étant disposées de par et d'autre de la zone de séparation des contacts,
• - et un circuit d'amenée de courant agencé entre la plage et le contact correspondant, et comprenant un premier trajet du courant à l'extérieur de l'aimant.

The invention relates to a rotary arc switch or circuit breaker comprising:

• - a sealed envelope filled with insulating gas with high dielectric strength,
• - a pair of separable contacts aligned in the axial direction of the envelope,
• - a permanent magnet generating a magnetic field in the contact separation zone to impose a rotation of the arc,
• - a pair of electrical connection connection pads with the contacts, said pads being arranged on either side of the contact separation zone,
• - And a current supply circuit arranged between the range and the corresponding contact, and comprising a first current path outside the magnet.

Document EP-A-37 765 relates to such a switch, and the permanent magnet is disposed inside a hollow conductive cylinder forming the fixed contact. The current flowing through the fixed contact and the supply circuit does not pass through the permanent magnet and does not generate any magnetic field capable of demagnetizing the magnet housed inside the fixed contact. The hollow cylinder of the fixed contact is provided with an annular rim disposed opposite a mating annular surface of the movable contact to cooperate by abutment in the closed position.

The breaking performance of such a switch remains limited due to the arrangement of the contacts and the permanent magnet. No possibility is possible to mount a semi-fixed contact or to associate a second permanent magnet with the movable contact, opposite the first magnet on either side of the contact separation zone.

According to document DE-B-1.236.628, the rotary arc switch comprises two permanent annular magnets with radial magnetization and coaxially surrounding the separable contacts. The flow of current through the contacts causes a magnetic field of demagnetization inside each magnet. This results in a risk of demagnetization of the permanent magnets which depends on the intensity of the current flowing in the switch and on the magnetic material of the magnet. This type of switch is mainly used for breaking low currents, but it is unable to cut high currents, for example greater than 15 kA. To reduce the demagnetization effect of the magnet, it has already been proposed according to FIG. 4 of document US-A-3,082,307, to surround the annular magnet through which the fixed contact passes, by means of a screen in copper sleeve shape. The flow, generated by the passage of current in the contact, induces eddy currents in the protective sleeve of the magnet. The result is an antagonistic flow which opposes the demagnetizing flow. This device is not entirely satisfactory, and the risk of demagnetization of the magnet remains, especially for breaking direct currents.

According to document GB-A-1,078,863 relating to a vacuum interrupter, the fixed and movable contacts are formed by hollow cylinders equipped with annular flanges coming into contact by abutment. Each cylinder is placed inside a permanent magnet, and the current is supplied by means of a conductive rod secured to the movable contact.

The problem posed by such a switch is the arrangement of the connection pads located axially on the same side with respect to the contact separation zone, with a risk of priming between the central current supply rod and the hollow cylinder associated with the fixed contact.

The present invention aims to allow the production of a reliable switch whose permanent magnet causing the rotation of the arc is protected from any demagnetization field regardless of the intensity of the current to be interrupted.

The switch according to the invention is characterized in that the permanent magnet is hollow while being crossed by one of the contacts, and in that the contact concerned is electrically connected to said first path of the current supply circuit disposed at the outside of said permanent magnet by a second path of the current supply circuit, said second path being disposed inside the hollow space of said magnet, so as to avoid any demagnetization field inside said hollow space said permanent magnet.

The second path of the current supply circuit comprises a U-shaped rim with a hairpin axial section extending along the internal face of the permanent magnet, the current flowing in opposite directions in the substantially parallel branches of the pin. As a result, inside the magnet, the magnetic fields generated by the passage of current through the branches of the U compensate each other, without any risk of demagnetization of the permanent magnet.

By using an annular permanent magnet, the second current path is advantageously formed by an internal ferrule one end of which is connected to the first external path and the opposite end of which is connected to a contact support tube or sleeve, the internal ferrule being arranged coaxially between the magnet and the tube or sleeve.

One of the contacts surrounded by a first permanent magnet can be fixed and has an annular contact end arranged in the vicinity (projecting or recessed) of the front front face of the magnet. This contact can also be semi-fixed by being connected to the internal ferrule by means of a sliding contact or a contact clamp.

The other movable contact in translation passes axially through a second permanent fixed magnet and is electrically connected to the corresponding internal ferrule of the circuit by a sliding contact, the second magnet being placed opposite the first magnet and separated from the latter by a predetermined axial interval. .

The magnetization of the permanent magnet (s) can be arbitrary, either radial or axial homopolar, or heteropolar. The envelope is filled with an electronegative gas such as sulfur hexafluoride, and according to an important development of the invention, the magnetic blowing of the arc by the action of the permanent magnet (s) is combined with a pneumatic blowing. by self-expansion of compressed gases liable to escape through hollow contacts.

• la figure 1 est une vue schématique partielle en coupe axiale d'un interrupteur à arc tournant selon l'invention, représenté en position de fermeture sur la demi-vue droite, et en position de coupure sur la demi-vue gauche ;
• la figure 2 est une vue partielle, analogue à celle de la fig. 1 d'une variante de réalisation ;
• la figure 3 montre une vue en coupe axiale d'une autre réalisation.

Other advantages and characteristics of the invention will emerge more clearly from the description which follows of different modes of implementation, given by way of nonlimiting examples and represented in the appended drawing in which:

• Figure 1 is a partial schematic view in axial section of a rotary arc switch according to the invention, shown in the closed position on the right half-view, and in the cut-off position on the left half-view;
• Figure 2 is a partial view, similar to that of FIG. 1 of an alternative embodiment;
• Figure 3 shows an axial sectional view of another embodiment.

In FIG. 1, a pole of a switch 10 or of a rotary arc circuit breaker comprises a sealed casing 12 of molded insulating material, filled with insulating gas 13 of high dielectric strength, in particular sulfur hexafluoride. The cylindrical casing 12 has an elongated shape, the upper part of which is closed off by a bottom 14 made of conductive material and with a radial tab shaped as a field 16 for supplying current. Inside the casing 12 are disposed axially a fixed contact 18 cooperating with a movable contact 20 aligned and mounted to slide axially by means of an actuating rod of a control mechanism (not shown).

The fixed contact 18 in the form of a hollow cylinder with a diameter equivalent to that of the movable contact 20, is coaxially surrounded by a permanent and annular fixed magnet 22. The permanent magnet 22 with radial magnetization generates in the arc zone a permanent radial magnetic field causing the rotation of the arc during the separation of the contacts 18, 20. The end of the fixed contact 18 being in abutment with the movable contact 20 in the closed position, protrudes from the front end face 24 of the permanent magnet 22. A current supply circuit 26 ensures the electrical connection of the fixed contact 18 with a central stud 28 of conductive material secured to the bottom 14.

The circuit 26 for supplying current to the tubular fixed contact 18 is formed by an annular conductive carcass of revolution about the longitudinal axis and having a recess 30 for housing the permanent magnet 22. The carcass of the circuit 26 is shaped in loop surrounding the four faces of the annular permanent magnet 22, and comprises a conductive copper base with a U-section constituted, for example, by the assembly of two internal coaxial ferrules 32 and external 34 to an annular washer 36 covering the front face 24 anterior of the magnet 22. The external ferrule 34 is connected to the central stud 28 by a conductive ring 38 extending parallel to the front face 40 posterior of the magnet 22 with the interposition of a ferromagnetic plate 42, by steel example. Opposite the washer 36, the internal ferrule 32, isolated from the ring 38 and the stud 28, is secured to a tube 44 supporting the fixed contact 18 so as to form an annular flange 45 with an inverted U-shaped pin section. , said flange 45 being housed in the cylindrical internal space of the permanent magnet 22. The internal ferrule 32 is interposed coaxially between the cylindrical lateral face 46 internal of the magnet 22 and the tube 44 made of metallic material, in particular copper or steel.

A thin sleeve (not shown) of insulating material can be inserted axially in the radial interval 48 of the inverted flange 45: The circuit 26 for supplying current to the fixed contact 18 forms with the permanent magnet 22 and the stud 28 an assembly monobloc carried by the bottom 14. The permanent magnet 22 is constituted by a ferrite magnet or a metallic magnet, and an insulating layer (not shown) can be interposed between the magnet 22 and the annular conducting carcass of the circuit 26.

Note that the circuit 26 for supplying current to the fixed contact 18 has a first path outside the magnet, connected in series with a second path inside the annular magnet 22. The first path includes the ring 38, the outer ring 34 and the washer 36 which respectively cover the plate 42 of the posterior front face 40, the external cylindrical side face 50, and the front front face 24 of the permanent magnet 22. The second path includes the inverted rim 45 formed by the internal ferrule 32 associated with the tube 44 supporting the fixed contact 18.

• En position de fermeture de l'interrupteur, représentée sur la demi-coupe droite de la fig. 1, le courant rentre par la plage 16 associée au fond 14 et circule dans le plot 28 et le circuit d'amenée 26 au contact fixe 18 selon le sens indiqué par les flèches. Le trajet à partir du plot 28 central est le suivant : bague 38, virole externe 34, rondelle 36, virole interne 32, tube 44, contact fixe 18 et contact mobile 20 en aboutement.

The switch according to FIG. 1 operates as follows:

• In the closed position of the switch, shown in the right half-section of FIG. 1, the current enters through the area 16 associated with the bottom 14 and flows through the pad 28 and the supply circuit 26 to the fixed contact 18 in the direction indicated by the arrows. The path from the central stud 28 is as follows: ring 38, external ferrule 34, washer 36, internal ferrule 32, tube 44, fixed contact 18 and movable contact 20 abutting.

The current flowing through the ring 38, the ferrule 34 and the washer 36 of the first external path does not pass through the annular permanent magnet 22 and does not generate any magnetic field capable of demagnetizing the magnet 22. The ferrule 32 and the tube 44 of the second internal path are separated by the small radial interval 48 and are traversed in the opposite axial direction by the current. This results in compensation for the magnetic fields generated in the internal cylindrical space of the magnet 22 by the passage of current through the ferrule 32 and the tube 44. The permanent magnet is thus protected from any demagnetization field , even in the presence of short-circuit currents of high intensity, for example greater than 20 kA.

The permanent magnet 22 generates a magnetic field which is permanently present in the breaking zone as soon as the contacts 18, 20 are separated. The switch is opened by sliding the movable contact 20 downwards (see half-section left of Fig. 1), and the arc drawn between the contacts 18, 20 extends substantially in the axial direction. The magnetic field of the permanent magnet 22 causes, in a well known manner, the rotation of the arc on the annular tracks of the hollow contacts 18, 20. It should be noted that the axial protrusion of the fixed contact 18 relative to the washer 36 of the conductive carcass maintains the arc roots on the annular tracks of the contacts 18, 20.

FIG. 2 represents an alternative embodiment, in which the axial length of the tube 44 supporting the fixed contact 18 is shortened so as to position the fixed contact 18 set back or in the vicinity of the washer 36. In the closed position, the passage of the current in the supply circuit 26 is identical to that of the device in FIG. 1, and no demagnetization field affects the magnetization of the permanent magnet 22 thanks to the axial outward and return path of the current in the ferrule 32 and the tube 44. At the start of the contact opening stroke 18, 20 the arc of the fixed contact 18 is switched to the washer 36, which then plays the role of an annular migration path of the rotating arc. After the switching, the current flows only in the first path of the circuit 26. The arc turns in the SF6 gas under the action of the field of the magnet around the washer 36 and the annular end of the movable contact 20, the internal ferrule 32 and the tube 44 not being traversed by any current.

FIG. 3 illustrates another alternative embodiment in which the same reference numbers are used to designate identical or similar parts to those of FIGS. 1 and 2. The magnetic blowing by rotation of the arc is accompanied by a double pneumatic blowing due to the thermal expansion of the gas generating a gas flow escaping through the fixed tubular contacts 18 and movable 20. The interrupting chamber 54 of the switch 10 is separated from the casing 12 by an intermediate casing 56 constituted by a cylindrical wall coaxial with the casing 12, and transverse shutter partitions 58, 60. The upper insulating partition 58 is crossed axially by the fixed stud 28 of tubular shape and with radial opening 62 formed between the bottom 14 and the partition 58. The movable contact 20 is integral with a conductive sleeve 63 mounted to slide axially through a orifice in the lower partition 60, said sleeve 63 actuated by means of a control rod 64 sealingly passing through the conductive bottom 66 connected to a connection pad 68. The sleeve 63 has radial openings 70 arranged between the partition 60 and the bottom 66. The two areas 16, 68 for connecting the switch are arranged on either side of the contact separation zone.

The fixed contact 18 is surrounded inside the breaking chamber 54 by the annular permanent magnet 22 and the current supply circuit 26 as described with reference to FIG. 1. The arc rotating under the action of the field of the magnet 22 causes, in a well known manner, the rise in pressure of the gas inside the interrupting chamber 54. This results in a gas flow which promotes extinction. from the arc, the gas escaping taking place towards the envelope 12 in opposite directions respectively through the fixed tubular contact 18 and the opening 62 of the stud 28, and through the movable contact 20 and the openings 70 of sleeve 63.

The magnetic blowing of the arc can be reinforced by using in the device of fig. 3 a second permanent magnet 72 coaxially surrounding the movable contact 20 inside the breaking chamber 54, and arranged opposite the first permanent magnet 22 associated with the fixed contact 18. The second magnet 72 is fixed and axially separated from the first magnet 22 by a predetermined interval corresponding substantially to the axial length of the cut-off zone. The movable contact 20 passes through the second annular permanent magnet 72, and is electrically connected to the bottom 66 of the connection pad 68 by means of a connection circuit 74 arranged to avoid demagnetization of the magnet 72. The circuit of link 74 is similar to the circuit 26 for supplying current to the fixed contact 18, and comprises a sliding contact 76 formed at the level of the partition 60 between the sliding sleeve 63 and a coaxial conductive socket 78. The internal diameter of the sleeve 78 corresponds substantially to the external diameter of the sleeve 63 with the interposition of a radial clearance allowing the bidirectional axial sliding of the sleeve 63. Unlike the sliding contact 76, the sleeve 78 extends along the internal side face of the magnet 72 and is electrically connected to a loop surrounding the magnet 72. The loop is formed by an annular conductive carcass, of structure identical to that associated with the magnet 22 of FIG. 1, and comprising a washer 36a, an outer ferrule 34a, a ring 38a. The latter is connected to a conductive tube 80 fixed in electrical connection with the bottom 66, and passing through the lower partition 60 in an axial direction so as to coaxially surround the socket 78 and the sleeve 63.

• En position de fermeture représentée sur la demi-vue gauche, le parcours du courant dans le circuit d'amenée 26 au contact fixe 18 correspond à celui de l'interrupteur de la fig.1. Le courant passe du contact fixe 18 vers le contact mobile 20 et le manchon 63, puis son sens s'inverse dans la douille 78 après passage dans le contact glissant 76. Le courant circule ensuite dans la rondelle 36a, la virole externe 34a, la bague 38a, le tube 80, le fond 66 et arrive à la plage de raccordement 68. On remarque que la circulation inverse du courant dans le contact mobile 20 et la douille 78 à l'intérieur de l'aimant 72 annulaire n'engendre aucun champ de démagnétisation susceptible d'affecter l'aimantation du deuxième aimant 72.

The operation of the switch 10 according to FIG. 3 is as follows:

• In the closed position shown on the half-view on the left, the path of the current in the supply circuit 26 to the fixed contact 18 corresponds to that of the switch in fig. 1. The current flows from the fixed contact 18 to the movable contact 20 and the sleeve 63, then its direction is reversed in the socket 78 after passage through the sliding contact 76. The current then flows in the washer 36a, the outer ferrule 34a, the ring 38a, the tube 80, the bottom 66 and arrives at the connection pad 68. It is noted that the reverse circulation of the current in the movable contact 20 and the socket 78 inside the annular magnet 72 does not generate any demagnetization field likely to affect the magnetization of the second magnet 72.

During the separation of the contacts 18, 20, the extinction of the arc is facilitated by the reinforcement of the magnetic field in the breaking zone, resulting from the sum of the elementary radial fields of the two magnets 22, 72. The magnetic blowing is combined with a pneumatic blowing by expansion of the SF6 gas through the tubular contacts 18, 20 in the direction of the casing 12.

According to a variant (not shown), the contact 18 instead of being fixed could be arranged in a semi-fixed manner thanks to the addition of an elastic means and a clamp or a sliding contact between the internal ferrule 32 and the contact 18. In the devices of fig. 1 to 3, the magnetization of the permanent magnet (s) 22, 72 is axial, but it is clear that the structure and the magnetization of the magnet can be arbitrary, in particular heteropolar or radial magnetization.

Claims (10)

1. Switch or circuit breaker with rotating arc comprising :

- a tight housing (12) filled with an insulant gas of high dielectric strength,

- a pair of separable contacts (18, 20) aligned according to the axial direction of the housing,

- a permanent magnet (22, 27) generating a magnetic field in the separation zone of the contacts, in order to provoke a rotation of the arc,

- a pair of connection lugs (16, 28) for the electrical connection with the contacts (18, 20), said connection lugs being arranged on one and on the other side of the separation zone of the contacts,

- and a current supply circuit (26, 74) arranged between the connection lug (16, 68) and the corresponding contact (18, 20), and comprising a first current path outsides the magnet, characterized in that the permanent magnet (22, 72) is hollow and is crossed by one of the contacts, and in that the concerned contact is electrically connected with said first path of the current supply circuit (26, 74) arranged outsides said permanent magnet (22, 72) by means of a second path (32, 44, 45) of the current supply circuit, said second path being arranged insides the hollow space of said magnet (22, 72), in order to avoid any demagnetization insides said hollow space of said permanent magnet (22, 72).

2. Switch according to claim 1, characterized by the fact that the second path of the current supply circuit (26, 74) comprises a U-shaped flange with axial hair-pin section extending along the internal face of the permanent magnet (22, 72) the current flowing in opposite directions in the quite parallel branches of said U-shaped flange.

3. Switch according to claim 1 or 2, characterized by the fact that the permanent magnet (22, 72) has a ring shape and that the second current path is constituted by an internal collar (32, 78) one end of which is connected with the first external path and the opposite end of which is connected with a tube (44) or pipe (63) for supporting the contact (18, 20), the internal collar (32, 78) being arranged coaxially between the magnet (22, 72) and the tube (44) or pipe (63).

4. Switch according to claim 2 or 3, characterized by the fact that the opening of the hair-pin shaped U of the second currend path is directed towards the separation zone of the contacts, and that the diameter of the contacts (18, 20) is less than that of the corresponding internal collar (32, 78).

5. Switch according to claim 2, 3 or 4, characterized by the fact that one (18) of the contacts, coaxially surrounded by the first permanent hollow magnet (22), is stationary and comprises a ring-shaped contact end located near the front side (24) of the magnet (22).

6. Switch according to claim 3 or 4, characterized by the fact that one (18) of the contacts, coaxially surrounded by a first permanent hollow magnet (22), is semi-stationary by limited movement of axial translation, and that the support tube (44) associated to said contact (18) is connected with the internal collar (32) by means of a sliding contact or a contact clamp.

7. Switch according to anyone of claims 3-6, characterized by the fact that the other contact (20), movable in translation, crosses axially a second stationary permanent magnet (72) and is connected electrically with the corresponding internal collar (78) of the circuit (74) by means of a sliding contact (76), the second magnet (72) being arranged facing the first magnet (22) and separated from it by a predeterminated axial space.

8. Switch according to anyone of the claims 1-7, characterized by the fact that the first and second current paths in the circuits (26, 74) are connected in series in order to constitute a conducting split frame around the longitudinal axis of the housing (12), said frame being provided with a ring-shaped recess for housing the corresponding permanent magnet (22, 72).

9. Self-expansion switch according to anyone of the preceding claims, the housing (12) being subdivided into a breaking chamber and an expansion chamber, characterized by the fact that one or both contacts (18, 20) are hollow to authorize the escaping of the gas towards the expansion chamber by action of the rotating arc in the breaking chamber.

10. Switch according to one of the preceding claims, characterized by the fact that the permanent magnet (22, 72) associated with the corresponding contact (18, 20) comprises a radial or axial homopolar magnetization or a heteropolar magnetization.

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