EP3232457B1 - Dc electrical circuit breaker - Google Patents

Description

The invention relates to a direct current air breaking electric circuit breaker having improved arc breaking capacity.

There are known direct current electrical circuit breakers with air breaking, which comprise electrical contacts, connected to input and output terminals of the electrical current and being selectively movable with respect to each other between a closed position, in which respective contact areas of the first and second electrical contacts are in contact with each other to allow the flow of direct electrical current between the first and second electrical contacts, and an open position, in which these contact zones are distant from each other.

In a known manner, these circuit breakers make it possible to protect electrical systems against abnormal conditions, such as an electrical overcurrent or a short circuit, by rapidly interrupting the flow of the electrical current when such an abnormal condition is detected. By "rapidly" is meant that the electric current should be interrupted within 100ms or, preferably, less than 10ms after detection of the abnormal condition.

To interrupt the flow of current, the conductors are moved away from each other to their open position. Typically, an electric arc then forms between their contact zones. This arc must be extinguished in order to interrupt the flow of electric current. In practice, for electric currents of high intensity, for example greater than ten amperes, the electric arc moves by blowing in the direction of an arc breaking chamber, where it is extinguished, thus allowing d '' interrupt the flow of current. Such a blowing effect is partly caused by an electromagnetic force exerted on the electric arc, under the effect of the magnetic field created by the flow of electric current in the electric arc itself. However, in the presence of an electric current of less intensity, for example less than or equal to ten amps or to one ampere, the magnetic field generated by the electric arc itself is not sufficient to move it by blowing towards the interrupting chamber. The electric arc can thus persist for a long time between the two electric contact zones. This is undesirable, as the circuit breaker does not quickly interrupt the flow of current, which can cause an unsafe situation.

We know of FR 2 632 772 B1 a circuit breaker in which a permanent magnet is placed on an arc horn at the input of the interrupting chamber, so as to generate a constant magnetic field to move an electric arc towards the chamber cut-off whatever the value of the electric current. However, such a device is not entirely satisfactory and, moreover, is complicated to produce industrially and sometimes requires significant modifications to existing circuit breakers for its integration.

EP 2 980 821-A1 discloses an electric circuit breaker according to the preamble of claim 1. Also known are the devices described in documents DE 10 2014 015 061-A1 , US 2014/061160-A1 and US 2013/105444-A1 .

It is these drawbacks that the invention more particularly intends to remedy by proposing an electric circuit breaker with direct current and with reversible polarity and in which an electric arc can be interrupted reliably even for low values of intensity of electric currents. , and which can be produced industrially in a simple manner.

To this end, the invention relates to a direct current electric circuit breaker according to claim 1.

Thanks to the invention, the magnetic field created by the magnet and by the magnetic circuit exerts a force on the electric arc which first displaces the latter away from the electric contact zones and perpendicular to the longitudinal plane. Due to the configuration of the magnetic field lines, the force exerted on the electric arc then changes direction, so as to then direct the electric arc towards the interrupting chamber. Due to the symmetrical configuration with respect to the longitudinal plane, the electric arc is displaced towards the interrupting chamber regardless of the direction of flow of the electric current in the circuit breaker. In addition, the magnetic circuit can be easily integrated into existing circuit breakers, without imposing significant structural modifications on them.

• L'aimant présente un axe magnétique orienté parallèlement à une direction longitudinale contenue dans le plan longitudinal.
• L'espacement entre l'aimant et l'extrémité du noyau magnétique est inférieure ou égale à 2mm ou, de préférence, inférieure ou égale à 1mm, ou encore de préférence nulle.
• L'aimant est un aimant permanent.
• L'aimant est réalisé dans un alliage synthétique contenant un élément de la famille des terres rares, par exemple un alliage de Samarium-Cobalt.
• Le noyau magnétique est réalisé en acier ou en fer.
• Les parois latérales sont réalisées en un matériau ferromagnétique.

According to advantageous but not mandatory aspects of the invention, such a circuit breaker can incorporate one or more of the following characteristics, taken in any technically admissible combination:

• The magnet has a magnetic axis oriented parallel to a longitudinal direction contained in the longitudinal plane.
• The spacing between the magnet and the end of the magnetic core is less than or equal to 2mm or, preferably, less than or equal to 1mm, or even preferably zero.
• The magnet is a permanent magnet.
• The magnet is made of a synthetic alloy containing an element of the rare earth family, for example a Samarium-Cobalt alloy.
• The magnetic core is made of steel or iron.
• The side walls are made of a ferromagnetic material.

• la figure 1 est une représentation schématique selon une vue en perspective d'une portion interne d'un disjoncteur électrique à courant continu conforme à l'invention ;
• la figure 2 est une représentation schématique, d'une portion du disjoncteur de la figure 1, selon la vue illustrée par la flèche F2 de la figure 1 ;
• les figures 3 et 4 représentent schématiquement des lignes de champ magnétique créées par le circuit magnétique du disjoncteur de la figure 1, selon des vues en coupe longitudinale dans le plan P1 et transversale dans le plan P2 de la figure 1 ;
• la figure 5 est une représentation schématique d'une portion du disjoncteur de la figure 1, selon le plan de coupe P2 de la figure 1 ;
• les figures 6 et 7 représentent schématiquement la direction d'une force électromagnétique exercée sur un arc électrique pour deux sens opposés de circulation du courant électrique dans le disjoncteur de la figure 1.

The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of an embodiment of a circuit breaker given solely by way of example and made with reference to accompanying drawings in which:

• the figure 1 is a schematic representation according to a perspective view of an internal portion of a direct current electric circuit breaker according to the invention;
• the figure 2 is a schematic representation of a portion of the circuit breaker figure 1 , according to the view illustrated by the arrow F2 of the figure 1 ;
• the figures 3 and 4 schematically represent magnetic field lines created by the magnetic circuit of the circuit breaker of the figure 1 , according to views in longitudinal section in the plane P1 and transverse in the plane P2 of the figure 1 ;
• the figure 5 is a schematic representation of a portion of the circuit breaker figure 1 , according to the cutting plane P2 of the figure 1 ;
• the figures 6 and 7 schematically represent the direction of an electromagnetic force exerted on an electric arc for two opposite directions of flow of the electric current in the circuit breaker of the figure 1 .

The figure 1 represents a part of a circuit breaker 1 with direct current and breaking in the air. The circuit breaker 1 here comprises a closed case, inside which are placed components of this circuit breaker 1. This case is for example made of thermoformed plastic. For clarity, the box of circuit breaker 1 is not shown in the figure 1 .

The circuit breaker 1 comprises electrical terminals 2 and 2 'for input and output of an electric current. Terminals 2 and 2 'are configured to electrically connect circuit breaker 1 to an electrical circuit that is to be protected. The terminals 2 and 2 'are made of an electrically conductive material, for example a metal such as copper. These terminals 2 and 2 'are here accessible from outside the box in order to connect the circuit breaker 1 to the circuit to be protected.

In this example, the polarities of the circuit breaker 1 are reversible, that is to say that the terminals 2 and 2 'can alternately and indifferently serve as input or output terminals of the electric current in the circuit breaker 1.

The circuit breaker 1 here comprises two sub-assemblies 1a and 1b each associated with a terminal 2, 2 '. The first sub-assembly 1a comprises the following elements: a first electrical contact 21 connected to the terminal 2, an arc breaking chamber 4 and a magnetic circuit 5. The second sub-assembly 1b comprises the following elements: an electrical contact 21 'connected to terminal 2', an arc breaking chamber 4 'and a magnetic circuit 5'.

Each of these two sub-assemblies 1a and 1b described operates in a similar fashion. Also, only the first subset is described in detail in what follows.

In this example, the elements of the second sub-assembly 1b are identical and have a function similar to those of the first sub-assembly 1a. The elements of the second sub-assembly 1b bear the same numerical reference as those of the first sub-assembly 1a, increased by the symbol "'". For example, contact 21 ′ is similar to contact 21, and differs from it here only by its position in circuit breaker 1.

The circuit breaker 1 further comprises a movable part 3, movable in rotation about a fixed axis X1 of the circuit breaker 1. For example, the movable part 3 is mounted to pivot about an axis around a shaft integral with the circuit breaker housing. 1. The movable part 3 is here electrically conductive between opposite contact zones 30 and 30 '.

We denote by “P1” a longitudinal geometric plane of the circuit breaker 1. In this example, the plane P1 forms a plane of symmetry of the circuit breaker 1. Here, the elements of the circuit breaker 1 are also arranged symmetrically with respect to the axis X1. . The axis X1 is perpendicular to the plane P1. We denote “Z1” a geometric axis perpendicular to the axis X1 and contained in the plane P1 and which here defines a vertical direction.

The electrical contact 21 is provided with a contact zone 22 intended to be brought into contact with the corresponding zone 30 of part 3. For example, the contact zones 22 and 30 each comprise an electrically conductive contact pad, for example. made of a metallic material, such as silver or copper.

The electrical contact 21 is electrically connected to the terminal 2, while the mobile part 3 is electrically connected to the terminal 2 ', as explained below.

Here, contact 21 is fixed relative to circuit breaker 1.

In this example, the electrical contact 21 is in the form of a bar made of an electrically conductive material, for example copper, which extends parallel to a fixed axis Y1 of the circuit breaker. The axis Y1 here extends longitudinally with respect to the plane P1 and in a horizontal direction. In this illustrative example, the electrical contact 21 is formed integrally with the terminal 2. More precisely, the bar comprises two straight portions superimposed, extending parallel to one another along the axis Y1 and connected. between them by a portion 20 of this bar, this portion 20 being curved in the shape of a "U". The contact zone 22 is provided on one of the straight portions of the electrical contact 21. The part of the terminal 2 intended to be connected to the outside is provided on the opposite right portion of the electrical contact 21. More precisely, the contact area 22 is provided on an upper part of the electrical contact 21 facing the corresponding contact zone 30 of the mobile part 3.

The mobile part 3 here plays the role of electrical contact vis-à-vis the electrical contact 21.

The movable part 3 and the electrical contact 21 are movable relative to one another, selectively and reversibly between closed and open positions. In the closed position, the contact zones 22 and 30 are in direct contact with one another to allow the flow of electric current between the movable part 3 and the electric contact 21. In the open position, the contact zones 22 and 30 are distant from each other, which prevents the flow of electric current when no electric arc is present between the contacts 22 and 30. For example, in this open position, the contact zones 22 and 30 are at least 5 mm apart, preferably at least 15 mm apart.

The arrows F1 illustrate the direction of movement of the movable part 3 from the closed position to the open position.

In this example, the movement of the movable part 3 between the closed and open positions is carried out along the plane P1, that is to say that the trajectory of the contact zone 30 during the movement is parallel to the plane P1. In the open position, the contact areas 21 and 30 are essentially aligned along an axis parallel to the Z1 axis.

Part 3 is here indirectly connected to terminal 2 ', in particular by means of electrical contact 21' of second sub-assembly 1b.

In a similar fashion, open and closed positions of the movable part 3 relative to the electrical contact 21 'are defined. The electrical contact 21 'extends here along a fixed axis Y1' parallel to the axis Y1.

The circuit breaker 1 is arranged such that the part 3 is simultaneously either in the open position or in the closed position, vis-à-vis the electrical contacts 21 and 21 '. Thus, by symmetry, the displacement towards the open position takes place simultaneously for each of these two sub-assemblies 1a and 1b. When the mobile part 3 is in the closed position, the electric current can flow between the terminals 2 and 2 'passing through the contact areas 21 and 21', through the moving part 3 and through their respective contact areas. The movement of the movable part 3 towards its open position aims to prevent the flow of this electric current between the terminals 2 and 2 '. When the mobile part 3 is in the open position, in the absence of an electric arc between the respective contact zones of the electrical contacts 21, 21 'and the mobile part 3, the electric current is prevented from flowing between the terminals 2 and 2 '.

In a known manner, when the movable part 3 is moved to the open position while an electric current flows between the terminals 2 and 2 ', an electric arc can form between the two contact zones 22 and 30. This electric arc allows electric current to continue to flow and must be turned off to interrupt this electric current.

The circuit breaker 1 also includes a trip circuit, not shown, configured to automatically move the mobile part 3 to the open position when an operating anomaly is detected, such as an overcurrent of the electric current flowing between the terminals 2. and 2 '.

For example, the chamber 4 is at least partly delimited by walls of the circuit breaker box.

In a known manner, the interrupting chamber 4 comprises a stack of arc interrupting plates 41, electrically conductive and superimposed with one another. These plates are intended to extinguish the electric arc once this electric arc has penetrated inside the interrupting chamber 4. In this example, these plates are identical to each other and have a planar shape, inscribed in a quadrilateral is in which an essentially "V" -shaped incision is made on an edge facing the zones 22 and 30. The stack of plates 41 is surmounted by an upper horn 43 of an arc disposed above a plate 42 d end of the stack.

In this example, the circuit breaker 1 comprises an arcing chamber. This chamber is, for example, at least partially defined by internal walls of the circuit breaker housing 1. The contact zones 22 and 30 are located inside this arcing chamber. The arcing chamber is in communication with the interrupting chamber 4 and opens inside the latter. The arcing chamber and the interrupter chamber 4 are both filled with air.

We denote by “P2” a geometric plane perpendicular to the plane P1 and extending in the direction Z1. The plane P2 here forms a plane of longitudinal section of the arc-forming chamber.

By way of example, the arc-forming chamber has the shape of a prism with a parallelepiped base, the lateral faces of which are parallel to the plane P1 and are formed by the lateral walls 31, 32.

In this example, the circuit breaker further comprises side walls 31 and 32, which delimit opposite faces of this arcing chamber parallel to the plane P1. Here, the walls 31 and 32 have an essentially planar shape and parallel to the plane P1. The opposing walls 31 and 32 are arranged on either side of the contact 22 and 30 facing each other. For example, the walls 31 and 32 are made of a ferromagnetic material, such as steel or iron.

By way of illustration, the walls 31 and 32 are each placed at a distance of between 10 mm and 100 mm from the contact zone 22, this distance being measured in a direction parallel to the axis X1.

The magnetic circuit 5 is configured to generate a magnetic field capable of guiding, in the direction of the interrupting chamber 4, an electric arc 6 forming between the contact zones 22 and 30 following the displacement, towards the open position, of the part. mobile 3. Due to the arrangement of the contact zones 22 and 30 in the open position, the electric arc 6 extends essentially along a direction parallel to the plane P1 and to the axis Z1.

All that is described with reference to the magnetic circuit 5 also applies to the magnetic circuit 5 'with respect to the corresponding elements of the sub-assembly 1b.

The figure 2 shows the arcing chamber and the interrupting chamber, in a top view along arrow F2 of the figure 1 . Reference 51 designates the magnetic field lines associated with the magnetic field created by the magnetic circuit 5.

We denote "R2" a central region of the arc-forming chamber, here delimited on either side by geometric planes parallel to the plane P1 on either side of the contact 22 and extending along the axis. Z1.

The central region R2 includes the contact zones 22 and 30. It has here the shape of a prism, the lower base of which is formed by a part of the upper surface of the electrical contact 21, and extends in height essentially parallel to the direction. vertical Z1.

We denote “R1” and “R3” two lateral regions of the arc forming chamber which are disposed laterally on either side of the central region R2. Here, these lateral regions R1 and R3 are delimited laterally on the outside by the walls 31 and 32. The regions R1 and R3 do not contain the contact zones 22 and 30.

• dans les régions latérales R1 et R3, les lignes de champ 51 s'étendent essentiellement perpendiculairement aux parois latérales 31 et 32, et
• dans la région centrale R2, les lignes de champ 51 s'étendent essentiellement parallèlement au plan P1 en convergeant vers la chambre de coupure 4. Par exemple, dans la région centrale, le flux magnétique est tel que le champ magnétique vu par l'arc est supérieur ou égal à 20 microTeslas.

The magnetic circuit 5 is shaped so that:

• in the side regions R1 and R3, the field lines 51 extend essentially perpendicular to the side walls 31 and 32, and
• in the central region R2, the field lines 51 extend essentially parallel to the plane P1, converging towards the interrupting chamber 4. For example, in the central region, the magnetic flux is such that the magnetic field seen by the arc is greater than or equal to 20 microTeslas.

The figures 3 and 4 represent these field lines 51 according to views in the planes P1 and P2 respectively.

The figure 5 represents the arcing chamber and the interrupting chamber 4 in the cutting plane P2, according to the viewing angle illustrated by the arrow F3 at the figure 1 . The movable part 3 is shown in the open position.

In this example, field lines 51 of the figure 2 are calculated by means of a finite element numerical simulation program, such as the software known under the trade name "Flux" and marketed by the company CEDRAT.

The magnetic circuit 5 here comprises a permanent magnet 50 and a ferromagnetic core 23 which has the function of at least partly guiding the magnetic field created by the magnet 50. The core 23 extends at least partly along the electrical contact. 21, along the Y1 axis. The walls 31 and 32 here form part of the magnetic circuit 5 and participate in guiding the magnetic flux created by the magnet 50 in particular to obtain the spatial arrangement of the field lines 51.

In this example, the core 23 has the shape of a rectilinear bar which extends between the two straight portions of the electrical contact 21. This core 23 is produced here in the form of a stack of ferromagnetic metal sheets. As a variant, the core 23 is formed by a single piece.

The magnet 50 is fixed here, for example by gluing, on one end of this part 23, here on the end located opposite the U-shaped part 20.

The magnet 50 is capable of generating a magnetic field greater than or equal to 0.5 tesla or, preferably greater than or equal to 1 tesla and here has a magnetic axis of magnetization M oriented parallel to the axis Y1.

Preferably, the magnet 50 is a permanent magnet, for example made from a synthetic alloy containing an element of the rare earth family. Here, we use a Samarium-Cobalt alloy. Advantageously, the magnet 50 is surrounded by a protective shell made of a non-magnetic material, such as plastic.

Here, the spacing between the magnet 50 and the end of the core 23 on which it is placed is less than or equal to 2 mm or, preferably, less than or equal to 1 mm, or even preferably zero, that is, that is to say equal to 0 mm. This spacing is here measured as being the distance between the adjacent edges of the magnet 50 and the end of the core 23. By reducing as much as possible the gap between the magnet 50 and this end of the core 23, the l 'air gap between the magnet 50 and the core 23, which ensures better channeling of the magnetic flux generated by the magnet 50.

The figure 6 represents the directions of the magnetic field created by the magnetic circuit 5 according to a view in the plane P2 from the interrupting chamber 4.

• « B1 », « B2 » et « B3 » les vecteurs d'induction magnétique dans les régions, respectivement R1, R2 et R3 de la chambre de formation d'arc ;
• « J » le vecteur densité de courant électrique associé à l'arc électrique 6 ;
• « E1 », « E2 » et « E3 » la force électromagnétique exercée sur l'arc électrique 6 sous l'action du champ magnétique créé par le circuit magnétique 5, pour chacune de ces régions R1, R2 et R3.

We notice :

• “B1”, “B2” and “B3” the magnetic induction vectors in the regions, respectively R1, R2 and R3 of the arcing chamber;
• "J" the electric current density vector associated with the electric arc 6;
• “E1”, “E2” and “E3” the electromagnetic force exerted on the electric arc 6 under the action of the magnetic field created by the magnetic circuit 5, for each of these regions R1, R2 and R3.

The vector J is here parallel to the direction Z1.

The electromagnetic forces E1, E2 and E3 are Lorentz forces and are proportional to the cross product between the vector J and to the magnetic induction, respectively, B1, B2 and B3 in the corresponding region R1, R2 or R3. In this example, due to the orientation of the field lines 51 and the direction of the current J, the forces E1 and E3 have directions parallel to the axis Y1 and are in opposite directions. The force E2 is directed parallel to the axis X1.

Thus, when an electric arc 6 forms between the contact zones 22 and 30, it is subjected to a force E2 which first directs it towards one of the lateral regions, in this case here the lateral region R3. Due to the perpendicular orientation of the vector B3 with respect to the vector B2 and the direction of the vector J, the force E3 exerted on the electric arc 6, when it is located in the lateral region R3, is directed towards the inside the interrupting chamber 4 and therefore towards the stack of interrupting plates 41. The electric arc 6 is therefore moved towards the chamber 4 by the force E3.

The figure 7 is analogous to figure 6 and differs only by the direction of circulation of the electric current J in the electric arc 6, this direction being reversed compared to that illustrated in the figure 6 . In this case, it can be seen that the force E2 exerted on the electric arc 6, when it is in the region R2 between the contact zones 22 and 30, is such that the electric arc 6 is displaced towards the lateral region R1 opposite to the lateral region R3. However, due to the relative orientation of vector B1 with respect to vector B2 and due to the change in sign of vector J with respect to the case of figure 6 , the force E1 directs the electric arc 6 towards the interrupting chamber 4.

Thus, thanks to the magnetic circuit 5, in particular due to the spatial arrangement of the field lines 51, the electric arc 6 is moved towards the interrupting chamber 4 whatever the direction of flow of the electric current and whatever its value. intensity. Even if the intensity of the electric arc current 6 is small, the electric arc 6 will be moved to a region where the electromagnetic force E1 or E3 is sufficient to move it towards the interrupting chamber 4. The operation of the circuit breaker 1 is thereby improved.

The magnetic circuit 5 can be made differently.

As a variant, the mobile part 3 is directly connected to the terminal 2 ', the second sub-assembly 1b then being omitted.

The embodiments and the variants considered above can be combined with one another to generate new embodiments.

Claims (7)

1. DC electrical circuit breaker (1), comprising:

   - first (2) and second (2') input and output terminals for a direct electric current,

   - first (21; 21') and second (3) electrical contacts which are connected to the first and second terminals, respectively, and are selectively displaceable relative to one another along a longitudinal plane (P1) of the circuit breaker, between:

   • a closed position, in which respective contact zones (22, 30) of the first and second electrical contacts are in contact with one another in order to allow the direct electric current to flow between the first and second electrical contacts, and

   • an open position, in which the contact zones are remote from one another,

   - a formation chamber for an electric arc (6), in which the contact zones (22, 30) are positioned;

   - a breaking chamber (4) for an electric arc (6);

   - a magnetic circuit (5) which includes a magnet (50, 50') and generates a magnetic field which is capable of guiding, in the direction towards the breaking chamber (4), an electric arc (6) that forms between the contact zones (22, 30) in the open position, the magnetic field generated by the magnetic circuit (5) having for that purpose curved field lines (51) which extend substantially perpendicularly to opposing side walls (31, 32) of the electric arc formation chamber, the side walls being arranged on either side of the contact zones (22, 30) substantially parallel to the longitudinal plane (P1), the field lines (51) converging, at the level of a central region (R2) of the arc formation chamber containing the contact zones (22, 30), towards the breaking chamber (4) while extending parallel to the longitudinal plane (P1),

   the magnetic circuit (5) further comprises a magnetic core (23, 23') made of ferromagnetic material and which extends at least in part along the first electrical contact (21),
   the circuit breaker being characterised in that the first electrical contact (21) has the form of a bar made of an electrically conducting material and comprising two superposed straight portions which extend parallel to one another and are connected together by a curved "U"-shaped portion (20), the contact zone (22) of the first electrical contact (21) being formed on one of the straight portions,
   in that the magnetic core (23) has the form of a rectilinear bar which extends between the two superposed straight portions of the first electrical contact (21), parallel to the two straight portions,
   and in that the magnet (50, 50') is positioned at one of the ends of the magnetic core (23, 23') and is capable of generating a magnetic field greater than or equal to 0.5 tesla or, preferably, greater than or equal to 1 tesla.
2. Circuit breaker according to claim 1, characterised in that the magnet (50, 50') has a magnetic axis which is oriented parallel to a longitudinal direction (Y1) contained in the longitudinal plane (P1), the straight portions of the first electrical contact (21) and the magnetic core (23) being arranged parallel to the longitudinal direction (Y1).
3. Circuit breaker according to claim 2, characterised in that the spacing between the magnet (50, 50') and the end of the magnetic core (23, 23') is less than or equal to 2 mm or, preferably, less than or equal to 1 mm, or yet more preferably zero.
4. Circuit breaker according to any one of the preceding claims, characterised in that the magnet (50, 50') is a permanent magnet.
5. Circuit breaker according to any one of the preceding claims, characterised in that the magnet (50, 50') is made of a synthetic alloy containing an element of the rare earth family, for example a samarium-cobalt alloy.
6. Circuit breaker according to any one of the preceding claims, characterised in that the magnetic core (23, 23') is made of steel or of iron.
7. Circuit breaker according to any one of the preceding claims, characterised in that the side walls (31, 32) are made of a ferromagnetic material.

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