Electrical circuit breaker

This electrical circuit breaker includes at least one first fixed land, a support assembly equipped with at least one second land rotationally mobile, about a main axis, between a first position in which the second land is in contact with the first land and a second position in which the second land is separated from the first land and an arc-extinguishing chamber including a stacking of plates, a top arc-guiding horn, a bottom arc-guiding horn, equipped with at least one tab and a screen made of insulating material surrounding the bottom arc-guiding horn. The circuit breaker also includes two protuberances produced in a gas-producing material, which are mounted on the screen, arranged between the bottom horn and the top arc-guiding horn and facing the tab of the bottom arc-guiding horn, the protuberances having a prismatic or pseudo-prismatic form.

The present invention relates to an electrical circuit breaker.

In the field of low-voltage electrical circuit breakers, it is known practice to use an electrical arc-extinguishing chamber equipped with a stacking of metal plates and a pair of bottom and top horns, in order to absorb electrical energy associated with an electrical arc. In particular, upon the switching of an electrical current passing between a fixed contact and a mobile contact of the circuit breaker, the opening of the contacts is generally accompanied by the formation of an electrical arc, called inter-electrode arc, because it is generated between the contacts of the circuit breaker. Thus, the horns are configured to guide the electrical arc towards the interior of the extinguishing chamber, in which the electrical arc is first elongated and successively broken up, using the metal plates. However, the opening of the contacts can also be accompanied by a partial reclosing through mechanical bounce. This promotes a repeat flashover between the contacts without absorption of the electrical energy of the electrical arc in the extinguishing chamber and can lead to circuit breaker switching failure.

In this regard, it is known practice, for example from EP-A-0 306 382, to equip the quenching chamber with a pair of electrical arc guiding cheeks. These cheeks each have a profile which closely follows the form of the metal plates and are configured to switch the electrical arc from a central zone towards a lateral zone of the extinguishing chamber. The electrical arc is thus displaced onto colder surfaces of the circuit breaker, which promotes the extinguishing thereof. However, the guiding cheeks have a large surface area, which can lead to significant pressures, in switching, in the extinguishing chamber. Furthermore, each guiding cheek constitutes a screen between the mobile contact and the steel parts of the circuit breaker.

In this respect, it is also known practice, for example from EP-A-0 410 902, to equip the bottom arc-guiding horn with a lip, or boss, in order to speed up the displacement of the electrical arc along this bottom horn towards the extinguishing chamber. However, this approach cannot avoid the repeat flashover between the contacts upon a partial reclosure.

It is these drawbacks that the invention seeks more particularly to remedy, by proposing a novel electrical circuit breaker which makes it possible to avoid any repeat flashover and not to generate overpressures inside the extinguishing chamber.

To this end, the invention relates to an electrical circuit breaker comprising at least one first fixed land, a support assembly equipped with at least one second land and rotationally mobile, about a main axis, between a first position in which the second land is in contact with the first land and a second position in which the second land is separated from the first land and an arc-extinguishing chamber comprising a stacking of plates, a top arc-guiding horn, a bottom arc-guiding horn, equipped with at least one tab and a screen made of insulating material surrounding the bottom arc-guiding horn. The circuit breaker also comprises two protuberances produced in a gas-producing material, which are mounted on the screen, arranged between the bottom arc-guiding horn and the top arc-guiding horn and facing the tab of the bottom arc-guiding horn, the protuberances having a prismatic or pseudo-prismatic form.

By virtue of the invention, the protuberances make it possible to recentre the electrical arc while cooling it by gas generation. The cooling of the space between the contacts avoids any repeat flashover despite a mechanical bounce of the contact finger. In practice, the space between the contacts has a greater than normal electrical capacity. Furthermore, the protuberances have a reduced size, in order not to adversely affect the switching efficiency of the electrical circuit breaker, and its electrical endurance.

According to advantageous but non-mandatory aspects of the invention, such an electrical circuit breaker comprises one or more of the following features, taken in any technically admissible combination:the bottom arc-guiding horn is equipped with two parallel tabs forming an edge and the two protuberances are arranged on either side of the tabs of the bottom arc-guiding horn;the protuberances are symmetrical relative to a central plane of the extension chamber;at least one protuberance has a height of between 12 and 30 mm, preferably equal to 18 mm, a width of between 18 and 30 mm, preferably equal to 28 mm, and a maximum thickness of between 3 and 13 mm, preferably equal to 11 mm;at least one protuberance has a minimum thickness of between 0 and 5 mm, preferably equal to 3 mm;the gas-producing material of at least one protuberance is synthetic, notably a glass fibre-filled polyamide, of type 66;the top arc-guiding horn comprises at least one orifice for discharging a gas generated by at least one protuberance;the support assembly comprises a plurality of second lands, between 4 and 12 thereof, preferably 10;the top and bottom arc-guiding horns are made of steel;the protuberances form an integral part of the screen.

FIGS. 1 and 2show an electrical circuit breaker1. The electrical circuit breaker1is configured to stop an electrical current in an electrical circuit. In practice, the electrical circuit breaker1is configured to stop all the currents and in particular the short-circuit currents in the electrical circuit. For example, the electrical circuit breaker1is a low-voltage high-rating circuit breaker configured to switch a current of intermediate level, for example between 10 and 35 kilo amperes (rms), and an electrical voltage of between, for example, 400 and 700 V.

The electrical circuit breaker1comprises an insulating casing2. The casing2comprises a base3. The base3defines a plane P3of the casing2. Inside the insulating casing2, there are arranged a device4with separable contacts, an arc-extinguishing chamber6, a first fixed contact region8and a second fixed contact region10.

The first and second contact regions8and10are electrical connection contact regions configured to electrically link the electrical circuit with lands of the circuit breaker1. The first and second contact regions8and10are fixed onto the base3of the casing2.

The device with separable contacts4is configured to open or close the electrical circuit on which the circuit breaker1is installed. The device4of the electrical circuit breaker1comprises a contact mechanism12, a support assembly14and a fixed main contact16.

The contact mechanism12is configured, as is known per se, to displace the support assembly14between a first position of closure of the electrical circuit breaker1and a second position of opening of the electrical circuit breaker1. The mechanism12is thus capable of displacing the support assembly14between its first position and its second position using an arm20and based on an electromagnetic and/or mechanical control. The contact mechanism12comprises, among other items, a spring device.

For this, the circuit breaker1comprises an electromagnetic actuator and a mechanical actuator, which are not represented in the figures.

The electromagnetic actuator comprises a core, a coil and a system of cams. In practice, when the electrical circuit is passed through by an overload current or a short-circuit current, the electromagnetic actuator transmits a command to open the circuit breaker1to the contact mechanism12.

The mechanical actuator comprises a lever that can be displaced between a high position and a low position by a user. Thus, when the user wants to bring about the closure or the opening of the circuit breaker1, the mechanical actuator transmits a command to the contact mechanism12.

The main contact16of the electrical circuit breaker1is connected to the first contact region8of the casing2and comprises a first land18, which is thus called fixed land. The first land18of the fixed main contact16is thus electrically connected to the first contact region8. The first land18has a planar and elongate rectangular form, as can be seen inFIG. 3.

As a variant, the main contact16comprises a number of lands18.

The main contact16also comprises an arc land17. The arc land17is electrically connected to the first contact region8and thus to the first land18. The arc land17is called fixed arc land. The arc land17has a rectangular and elongate form. Its length is, for example, less than the length of the land18.

Finally, the main contact16comprises a recess40and two stages41. The recess40extends parallel to the lands17and18opposite the land18relative to the land17. The stages41are positioned on either side of the recess40.

The support assembly14is made of insulating material. The assembly14defines a first axis X14of rotation and is equipped with a plurality of mobile contacts15.

The mobile contacts15are parallel and of equal length. In practice, the mobile contacts15extend transversely relative to the lands17and18, in a direction at right angles to the axis X14. Each mobile contact15comprises an extension21and a second land22. The extension21of each mobile contact15comprises an arc land23. The arc lands23of the mobile contacts15are configured to cooperate with the fixed arc land17.

In practice, the assembly14comprises a plurality of second lands22, between 4 and 12 thereof, preferably 10.

As a variant, the assembly14comprises a single mobile contact15.

The mobile contacts15of the assembly14are mobile, relative to the assembly14and about a second axis X15parallel to the first axis X14, between a so-called low position, in which the mobile contacts15are close to the fixed main contact16, and a so-called high position in which the mobile contacts15are separated from the fixed main contact16.

The spring device of the mechanism12bears on the mobile contacts15and is thus configured to stress the mobile contacts15in rotation about the axis X15in the anti-clockwise direction inFIG. 1.

The support assembly14also comprises an internal electrical connection, which is not represented in the figures and which is configured to electrically link the lands22and23of the mobile contacts15to the second contact region10of the circuit breaker1.

The assembly14, and thus the mobile contacts15, are mobile relative to the casing2and in rotation, about the axis of rotation X14, between the first position of closure in which the second lands22are in contact with the first land18and the second position of opening in which the second lands22are separated from the first land18. Thus, the arc lands23and the second lands22are said to be mobile.

In particular, the assembly14and the mobile contacts15are arranged in such a way that the rotations about the respective axes X14and X15have reverse directions. For example, when the assembly14passes from the position of closure to the position of opening, the assembly14is rotated about the axis X14in the clockwise direction, whereas the mobile contacts15pass from the high position to the low position and are rotated about the axis X15in the anti-clockwise direction.

The arc-extinguishing chamber6is configured to absorb an electrical energy generated by an electrical arc which is generated between the first land18and the second lands22when the mobile contacts15are displaced from their first position to their second position, that is to say when the second lands22are separated from the first land18. In practice, the extinguishing chamber6is configured to provoke, first of all, the elongation and, in succession, the breaking up and extinguishing of the electrical arc.

The extinguishing chamber6comprises a stacking of plates24, a top horn26, a bottom horn28and a screen30made of insulating material. The chamber6further comprises two lateral walls25and a bottom wall27. The walls25and27define, using the horns26and28and the screen30, a cage of the chamber6. P denotes the central plane of the extinguishing chamber6, which is at right angles to the plane P3of the base3of the casing2. The plane P thus defines a central main plane for the circuit breaker1.

The bottom wall27is provided with a porous filtering system which makes it possible to cool a gas present in the chamber6. The cooling of the gas makes it possible to maintain a correct pressure inside the chamber6and thus avoid an overpressure, which could reduce the switching efficiency of the extinguishing chamber6. As a variant, the bottom wall27has no filtering system. The plates24are metal and are configured to provoke the de-ionization of the electrical arc, when the latter is present in the extinguishing chamber6. Each plate24of the chamber6comprises a V-shaped central notch32arranged between two intermediate electrical arc collection edges34. The edges34are symmetrical relative to the plane P of the chamber6and can be rectilinear or dished. In practice, the plane P of the chamber6passes through the notches32of the plates24.

The top26and bottom28horns are made of steel and configured to guide the electrical arc from its original position between the first land18and the second lands22towards the interior of the extinguishing chamber6.

The top horn26comprises a bent portion36. The portion36is equipped with a tab38which is folded back downwards in a direction substantially at right angles to the plane P3of the base3of the casing2. The tab38of the top horn26is arranged transversely to the plates24. The top horn26is provided with an orifice29allowing for the evacuation of an ionized gas generated in the chamber6during the stopping of the short-circuit currents. The discharging of the gas through this orifice29makes it possible to facilitate the regeneration of a gaseous medium between the mobile contacts15and the fixed contact16. The discharging of the gas also makes it possible to maintain a correct pressure inside the chamber6and thus avoid an overpressure, which could reduce the switching efficiency of the extinguishing chamber6. As a variant, the top horn26is provided with a number of discharge orifices.

The bottom horn28extends between the fixed main contact16, which is attached to the first land8, and the extinguishing chamber6. In practice, the bottom horn28is electrically linked with the fixed main contact16. The bottom horn28constitutes one of the end plates24of the extinguishing chamber6and comprises a tongue42and two tabs44arranged on either side of a notch46.

The tongue42of the bottom horn20is positioned in a housing43of the screen made of insulating material30. In practice, the tab42is surrounded by and secured to the screen30and is located inside the extinguishing chamber6.

The tabs44are parallel to one another and extend, in a direction parallel to the plane P3, between the fixed arc land17of the fixed main contact16and the tongue42. In particular, they protrude, in a direction at right angles to the plane P3, towards the top horn26. In the assembled configuration of the circuit breaker1, an edge45of the tabs44is arranged in the recess40of the fixed main contact16. The tabs44are symmetrical relative to the central plane P of the chamber6. The notch46faces the fixed arc land17of the main contact16and of the mobile contacts15of the electrical circuit breaker1.

As a variant, the bottom horn28comprises a single tab44.

The screen made of insulating material30is configured to electrically insulate the base3of the casing2from the extinguishing chamber6. The screen30comprises the housing43and two planar portions50. The planar portions are situated on either side of the housing43and each comprise an end52. The ends52define, between them, an opening54. The opening54is provided to receive the main contact16. In practice, in the assembled configuration of the circuit breaker1, the main contact16is arranged in the opening54of the screen30, the ends52of the screen30being arranged on the stages41of the main contact16.

Two protuberances48are mounted on the planar portions50of the screen30, on either side of the housing43and of the opening54, in which the main contact16is arranged.

As a variant, the circuit breaker1comprises a single protuberance48.

The protuberances48form an integral part of the screen30.

The protuberances48are produced in a gas-producing material. Gas-producing should be understood to mean that the material is capable of generating a gas when it is subjected to a certain temperature. In practice, the protuberances48are configured to generate a cooling gas, such as hydrogen, when their surfaces are subjected to a very high temperature, notably of the order of 800° C. The gas-producing material of the protuberances48is, for example, synthetic, notably of polyamide, of type 66, with between 10% and 30% glass fibre filling.

Thus, in the assembled configuration of the circuit breaker1, the protuberances48are arranged at the input of the extinguishing chamber6, between the bottom horn28and the top horn26, and facing the lips44of the bottom horn28. In practice, the protuberances48are arranged, in a direction parallel to the axis X14, on either side of the tabs44of the bottom horn28. Furthermore, the protuberances48are symmetrical relative to the central plane P of the extinguishing chamber6.

The protuberances48have a prismatic or pseudo-prismatic form. In particular,56denotes the base of the prism forming a protuberance48. The base56is, for example, of trapezoidal form.

H denotes the height of the protuberances48. The height H is between 12 and 30 mm, preferably equal to 18 mm.

Also, L denotes the width of the protuberances48. The width L is between 18 and 30 mm, preferably equal to 28 mm.

Finally, E denotes the maximum thickness andedenotes the minimum thickness of the protuberances48. The maximum thickness E is between 3 and 13 mm, preferably equal to 11 mm, whereas the minimum thicknesseis between 0 and 5 mm, preferably equal to 3 mm.

The operation of the circuit breaker1is as follows:

When the circuit breaker1is in the closed configuration, the support assembly14is in the position of closure and ensures the passing of an electrical current. The mobile contacts15are in the high position. The mobile lands22of the mobile contacts15are bearing against the land18of the fixed main contact16. The pressure of the mobile lands22on the land18is ensured by the spring device of the mechanism12. The arc lands23of the mobile contacts15are separated from the fixed arc land17of the fixed main contact16. A non-zero distance, defined at right angles to the axis X14, exists between the arc lands17and23. Thus, the electrical current passes exclusively between the lands18and22.

When the electromagnetic actuator or the mechanical actuator of the circuit breaker1commands the electrical circuit to open, the support assembly14is rotated, about the axis X14, from the first position of closure towards the second position of opening of the lands18and22. Furthermore, the mobile contacts15are rotated, about the axis X15, from the high position towards the low position. In practice, the respective rotations of the assembly14and of the mobile contacts15are in opposite directions. Because of these opposing rotations, before the mobile lands22of the mobile contacts15can be separated from the fixed land18of the main contact16, the arc lands23of the contacts15come to bear on the fixed arc land17of the main contact16. The distance that exists between the lands17and23in the position of closure of the assembly14is cancelled.

When the support assembly14continues its rotation towards the position of opening and the mobile lands22of the mobile contacts15are separated from the fixed land18of the main contact16, the arc lands17and23still bear on one another. In practice, the opening of the lands18and22is performed without the generation of an electrical arc and the electrical current passes through the lands17and23.

Finally, in the continuation of the rotation of the support assembly14, the arc lands17and23separate and an electrical arc is generated between the latter. Thus, the presence of the arc lands17and23avoids the erosion of the main lands18and22.

The form of the fixed arc land17makes it possible to obtain a centring of the arc relative to the central plane P of the chamber6. This reduces the wear of the lateral walls25of the chamber6and the result thereof is a notable improvement in the electrical endurance of the circuit breaker1.

Because of the proximity of the tabs44of the bottom horn28to the fixed arc land17, the electrical arc is forced to migrate towards the bottom horn28. In particular, the electrical arc is set up between the lip45of the bottom horn28and the tab32of the top horn26.

As is known per se, the form of the bottom28and top26horns guides the electrical arc towards the interior of the extinguishing chamber6. The electrical energy associated with the electrical arc is dissipated as heat and provokes a very significant increase in the temperature which reaches, for example, 4000° C. at the core of the electrical arc. Such a temperature provokes the vaporization of the surfaces of the protuberances48and thus the production of the cooling gas. The cooling action of the electrical arc produced by the gas produced by the protuberances48is thus improved.

The gas generated by the protuberances48is then discharged through the discharge orifice positioned on the top horn26of the extinguishing chamber6.

The embodiment and the variants envisaged above can be combined together to generate new embodiments of the invention.