LOW-VOLTAGE CIRCUIT BREAKER

Abstract

A low-voltage circuit breaker, including: at least one fixed contact, for each pole, which is electrically connected to a terminal for connection to an electric circuit and a corresponding moving contact which is associable/separable with respect to the fixed contact by means of a rotation of the moving contact; an arc chamber positioned in correspondence of the fixed contact; a rotating contact supporting shaft common to all poles, which is functionally connected to an actuation mechanism of the circuit breaker, the actuation mechanism including a kinematic system operatively connected to an actuation lever for opening/closing operations and provided with opening springs and a tripping shaft for releasing the kinematic system and allowing its movement from a closed to an open position. The low-voltage circuit breaker includes for each pole a quick acting trip device including a plunger inserted in a first channel connected to an arc chamber of the corresponding pole, the first channel being positioned proximate to the at least one fixed contact with its longitudinal axis perpendicular to the axis of the rotating contact supporting shaft, the plunger having a first operative surface subjected to the pressure of the arc chamber and a second operative surface, the quick acting trip device further includes a trip lever having a first portion cooperating with the tripping shaft and a second portion cooperating with the second operative surface of the plunger.

Claims

1. A low-voltage circuit breaker, comprising at least one fixed contact, for each pole, which is electrically connected to a terminal for connection to an electric circuit and a corresponding moving contact which is associable/separable with respect to said fixed contact by means of a rotation of said moving contact; an arc chamber positioned in correspondence of said fixed contact; a rotating contact supporting shaft common to all poles, which is functionally connected to an actuation mechanism of the circuit breaker, said actuation mechanism comprising a kinematic system operatively connected to an actuation lever for opening/closing operations and provided with opening springs and a tripping shaft for releasing said kinematic system and allowing its movement from a closed to an open position, wherein for each pole a quick acting tip device comprising a plunger inserted in a first channel connected to an arc chamber of the corresponding pole, said first channel being positioned proximate to said at least one fixed contact with its longitudinal axis perpendicular to the axis of said rotating contact supporting shaft, said plunger having a first operative surface subjected to the pressure of said arc chamber and a second operative surface, said quick acting trip device further comprises a trip lever having a first portion cooperating with said tripping shaft and a second portion cooperating with the second operative surface of said plunger.

2. The low-voltage circuit breaker, according to claim 1, wherein said plunger is slidingly movable in said first channel under the action of an overpressure within said arc chamber between a first resting position and a second operating position in which it urges against the second portion of said trip lever determining the movement thereof from a normal-operating position to a tripping position in which said trip lever acts on said tripping shaft determining the release of said kinematic system.

3. The low-voltage circuit breaker, according to claim 2, wherein said plunger is slidingly movable in said first channel under the action of said trip lever between said second operating position and said first resting position when said kinematic system is moved from an open position to a closed position.

4. The low-voltage circuit breaker, according to claim 3, wherein said arc chamber comprises a second, venting, channel separated from said first channel.

5. The low-voltage circuit breaker, according to claim 4, wherein for each pole, a first and a second fixed contacts and respective corresponding first and second moving contacts which are associable/separable with respect to said fixed contacts by means of a rotation of said first and second moving contacts, a first and a second arc chambers being respectively positioned in correspondence of said first and second fixed contacts, said plunger being inserted in said first channel which is connected to one of said first and second arc chambers.

6. The low-voltage circuit breaker, according to claim 5, wherein said trip lever is pivotally secured on a fixed part of said circuit breaker.

7. The low-voltage circuit breaker, according to claim 6, wherein said trip lever has a central body pivotally secured on a fixed part of said circuit breaker, the first portion of said trip lever being a shaped surface of said central body, the second portion of said trip lever being an arm protruding from said central body.

8. The low-voltage circuit breaker, according to claim 7, wherein under the action of said plunger on the arm protruding from said central body, said trip lever rotates in a first direction and the shaped surface of said central body urges on said tripping shaft.

9. The low-voltage circuit breaker, according to claim 8, wherein under the action of said tripping shaft on the shaped surface of said central body, said trip lever rotates in a second direction opposite to said first direction, the arm protruding from said central body pushing on the second operative surface of said plunger and moving it from said second operating position to said first resting position.

10. The low-voltage circuit breaker, according to claim 9, wherein said plunger has a substantially cylindrical body.

11. The low-voltage circuit breaker, according to claim 10, wherein said trip lever and said trip shaft are rotatably mounted on a respective rotation axis, the rotation axis of said trip lever, of said trip shaft and of said rotating contact supporting shaft being parallel to each other and perpendicular to the longitudinal axis of said first channel.

12. The low-voltage circuit breaker, according to claim 1, wherein said arc chamber comprises a second, venting, channel separated from said first channel.

13. The low-voltage circuit breaker, according to claim 1, wherein for each pole, a first and a second fixed contacts and respective corresponding first and second moving contacts which are associable/separable with respect to said fixed contacts by means of a rotation of said first and second moving contacts, a first and a second arc chambers being respectively positioned in correspondence of said first and second fixed contacts, said plunger being inserted in said first channel which is connected to one of said first and second arc chambers.

14. The low-voltage circuit breaker, according to claim 1, wherein said trip lever is pivotally secured on a fixed part of said circuit breaker.

15. The low-voltage circuit breaker, according to claim 1, wherein said trip lever has a central body pivotally secured on a fixed part of said circuit breaker, the first portion of said trip lever being a shaped surface of said central body, the second portion of said trip lever being an arm protruding from said central body.

16. The low-voltage circuit breaker, according to claim 15, wherein under the action of said plunger on the arm protruding from said central body, said trip lever rotates in a first direction and the shaped surface of said central body urges on said tripping shaft.

17. The low-voltage circuit breaker, according to claim 16, wherein under the action of said tripping shaft on the shaped surface of said central body, said trip lever rotates in a second direction opposite to said first direction, the arm protruding from said central body pushing on the second operative surface of said plunger and moving it from said second operating position to said first resting position.

18. The low-voltage circuit breaker, according to claim 1, wherein said plunger has a substantially cylindrical body.

19. The low-voltage circuit breaker, according to claim 1, wherein said trip lever and said trip shaft are rotatably mounted on a respective rotation axis, the rotation axis of said trip lever, of said trip shaft and of said rotating contact supporting shaft being parallel to each other and perpendicular to the longitudinal axis of said first channel.

Description

[0046] Further features and advantages of the present invention will be more clear from the description of preferred but not exclusive embodiments of the low-voltage power circuit breaker of the present invention, shown by way of examples in the accompanying drawings, wherein:

[0047] FIG. 1 is a perspective view of a low voltage power circuit breaker, according to the invention;

[0048] FIG. 2 is a section view of a pole of a low voltage power circuit breaker, according to the invention, in a first operative condition;

[0049] FIG. 3 is a section view of a pole of a low voltage power circuit breaker, according to the invention, in a second operative condition;

[0050] FIG. 4 is an enlarged view of a quick acting trip device of a low voltage power circuit breaker, according to the invention, in the second operative condition shown in FIG. 3;

[0051] FIG. 5 is a section view of a pole of a low voltage power circuit breaker, according to the invention, in a third operative condition;

[0052] With reference to the attached figures, the low voltage power circuit breaker of the present invention, designated by the reference numeral 1, in its more general definition, comprises a casing 2 housing a number of poles 3, 4, 5. On the front side of the circuit breaker 1, there is provided an actuation lever 6 for carrying out the opening and closing operations of the circuit breaker 1.

[0053] Each pole 3, 4, 5 of the circuit breaker 1 comprises at least one fixed contact which is electrically connected to a terminal for connection to an electric circuit and a corresponding moving contact which is associable/separable with respect to said fixed contact by means of a rotation of said moving contact.

[0054] Each pole 3, 4, 5 further comprises an arc chamber which is positioned in correspondence of said fixed contact.

[0055] In the embodiment shown in FIGS. 2-5, the low-voltage circuit breaker is a double-interruption circuit breaker and comprises, for each pole 3, 4, 5, a first 20 and a second 30 fixed contacts and respective corresponding first 21 and second 31 moving contacts which can be connected to and separated form said fixed contacts 20 and 30 by means of a rotation of said first 21 and second 31 moving contacts.

[0056] Correspondingly, the circuit breaker 1 further comprises a first 40 and a second 41 arc chambers which are respectively positioned in correspondence of said first 20 and second 30 fixed contacts.

[0057] The low voltage power circuit breaker 1 of the present invention further comprises a rotating contact supporting shaft 50 which is common to all poles 3, 4, 5 and which supports and imparts motions to the moving contacts. The rotating contact supporting shaft 50 is functionally connected to an actuation mechanism of the circuit breaker 1.

[0058] According to known embodiments of a low-voltage circuit breaker, said actuation mechanism typically comprises a kinematic system which is operatively connected to the actuation lever 6 for opening/closing operations and provided with opening springs and a tripping shaft 60 for unlatching said kinematic system and allowing its automatic movement from a closed to an open position. The functioning of the actuation mechanism and of the various element thereof (e.g., its kinematic system with opening springs and a tripping shaft) are well known in the art and will not be described in further details.

[0059] An essential feature of the low voltage power circuit breaker 1 of the present invention is given by the presence—in each pole 3, 4, 5 thereof—of a quick acting trip device 100 having previously undisclosed characteristics and performances.

[0060] In the following description, the quick acting trip device 100 will be described with reference to the pole 3 of the circuit breaker, but the set-up for poles 4, 5 of the circuit breaker 1 is the same. Also, the circuit-breaker 1 of FIG. 1 is a three-pole circuit breaker, but the present invention is also applicable to circuit breakers having a different number of poles.

[0061] With reference to FIGS. 2-5, the quick acting trip device 100 of the circuit breaker 1 of the present invention comprises a plunger 101 which is inserted in a first channel 102 connected to an arc chamber 40 of the corresponding pole 3.

[0062] As shown in the attached figures, the first channel 102 is positioned proximate to a fixed contact 20 and its longitudinal axis is perpendicular to the axis of said rotating contact supporting shaft 50. In this way, a prompt response of the plunger 101 to the overpressure created by an electrical arc is ensured.

[0063] The plunger 102 has a first operative surface 103 which faces toward the arc chamber 40 and is subjected to the pressure of said arc chamber 40, and a second operative surface (104), opposite to said first operative surface 103.

[0064] The quick acting trip device 100 further comprises a trip lever 110 which has a first portion 111 cooperating with said tripping shaft 60 and a second portion 112 cooperating with the second operative surface 104 of said plunger 101, according to operating principles better described hereinafter.

[0065] In practice, in the low-voltage circuit breaker 1 of the present invention, the plunger 101 is slidingly movable inside said first channel 102 under the action of an overpressure created within said arc chamber 40 as a consequence of an electrical arc. The movement of the plunger 101 takes place between a first resting position and a second operating position in which it is pushed in the first channel 101 and urges against the second portion 112 of said trip lever 110.

[0066] In turn, under the action of the plunger 101, the trip levers 110 moves from a non-operating position to a tripping position in which said trip lever 110 acts on the tripping shaft 60 of the kinematic system of the circuit breaker determining the unlatching of said kinematic system and its automatic passage from a closed position to an open position.

[0067] According to a very effective design solution, the trip lever 110 and the trip shaft 60 are rotatably mounted on a respective rotation axis. In particular, the rotation axis of said trip lever 110, of said trip shaft 60 and of said rotating contact supporting shaft 50 are parallel to each other and perpendicular to the longitudinal axis of said first channel 102, thereby achieving a very compact and simple design structure that allows minimizing mechanical stresses on the kinematic chain: plunger 101—trip lever 110—trip shaft 60 and ensuring a fast response thereof.

[0068] In practice, according to this solution the plunger 101 moves inside the first channel 102 in a direction which is perpendicular to the rotation axis of said trip lever 110, of said trip shaft 60 and of said rotating contact supporting shaft 50. Being the first channel 102 positioned on the top of the arc chamber, close to the fixed contact, it is also close to the trip lever 110, thereby minimizing the design complexity of the whole system and increasing its reliability.

[0069] In order to restore the normal operating conditions, the plunger 101 is also slidingly movable in said first channel 102 under the action of said trip lever 110 between said second operating position and said first resting position when said kinematic system is moved from an open position to a closed position.

[0070] In practice, when an electrical arc occurs and an overpressure is created inside the arc chamber 40, the plunger 101 is pushed against the trip lever 110 which therefore acts on the on the tripping shaft 60 determining the unlatching of the kinematic system of the circuit breaker 1.

[0071] Conversely, when the circuit breaker 1 is closed by acting on the actuation lever 6, the kinematic system is moved from the open position to the closed position and so is the tripping shaft 60 and the trip lever 110. During such movement, the trip lever 110 acts on the plunger 101 bringing it back to its first resting position.

[0072] As shown in the attached figures, the arc chamber 40 advantageously comprises a second, venting, channel 45 which is separated from said first channel 102. In practice, the second, venting, channel 45 is the main venting opening of the arc chamber 40 toward the exterior of the circuit breaker 1 and is conveniently kept separated from the first channel 102 which is just an operating channel for the quick acting trip device 100. Shape and dimensioning of the second, venting, channel 45 can be designed according to the needs. Also, more venting channels are possible depending on the needs.

[0073] As previously said, in the embodiment shown in the attached FIGS. 2-5, the low-voltage circuit breaker 1 comprises, for each pole 3, 4, 5, a first 20 and a second 30 fixed contacts and respective corresponding first 21 and second 31 moving contacts which can be coupled to and uncoupled form said fixed contacts 20, 30 by means of a rotation of said first 21 and second 31 moving contacts.

[0074] A first 40 and a second 41 arc chambers are also present and are respectively positioned in correspondence of said first 20 and second 30 fixed contacts. The quick acting trip device 100 is conveniently associated with only one of the arc chambers, in particular with the arc chamber 40, which is the one closer to the tripping shaft 60. Therefore, the plunger 101 of the quick acting trip device 100 is inserted in the first channel 102, which is connected to said first arc chamber 40.

[0075] From a mechanical standpoint, the trip lever 110 in the embodiment shown is pivotally secured on a fixed part of said circuit breaker 1.

[0076] In particular, the trip lever 110 has a central body 113, which is pivotally secured on a fixed part of the circuit breaker 1. The first portion 111 of said trip lever 110 is a shaped surface, in the embodiment shown a cam-shaped surface, of the central body 113, while the second portion 112 of the trip lever 110 is an arm protruding from said central body 113.

[0077] The functioning of the circuit breaker 1, and in particular of the quick acting trip device 100 in a typical embodiment of the invention, will be now described with reference to the attached FIGS. 2-5.

[0078] With reference to FIG. 2, in the closed conditions of the circuit breaker 1 the moving contacts 21 and 31 are coupled to the corresponding fixed contacts 20, 30 and current flows into the circuit. For each pair of contacts the current flows in the movable contact in an opposite direction with respect to fixed contact.

[0079] In case of a short circuit the current increase abruptly and the repulsion forces generated by the current flowing in two opposite directions in the fixed and moving contacts brings about separation of the moving contact 21 and 31 from the corresponding fixed contact 20 and 30. Under such conditions, an arc is generated inside the arc chambers 40 and 41 with a corresponding sharp increase of pressure inside them.

[0080] In particular, with reference to FIGS. 3 and 4, the overpressure inside the arc chamber 40 starts the tripping action of the quick acting tripping device 100 positioned in correspondence of said arc chamber 40.

[0081] In practice, the plunger 101 is pushed inside the channel 102 by the action exerted by the overpressure on the first operative surface 103 thereof. Then, as a consequence of the action of said plunger 101 on the arm 112 protruding from the central body 113 of the trip lever 110, said trip lever 110 rotates in a first direction (i.e., counterclockwise in the embodiment shown). During such rotation, the cam-shaped surface 111 of the central body 113 of the trip lever 110 urges on the tripping shaft 60, determining its clockwise rotation and the unlatching of the kinematic system of the circuit breaker.

[0082] FIG. 5 shows the position of the system when the tripped action of the circuit breaker 1 is completed.

[0083] When the low-voltage circuit breaker 1 is closed, e.g. by acting on actuation lever 6, the kinematic system is operated so as to rotate the rotating contact supporting shaft 50 counterclockwise and put the moving contacts 21 and 31 in contact with the corresponding fixed contacts 20 and 30. At the same time, the tripping shaft is rotated counterclockwise to latch the mechanism.

[0084] During such rotation, the tripping shaft 60 urges on the cam-shaped surface 111 of the central body 113 of the trip lever 110. Under the action of the tripping shaft 60 on the cam-shaped surface 111 of the central body 113, said trip lever 110 rotates in a second direction (i.e., clockwise in the embodiment shown) which is opposite to said first direction. During such rotation, the arm 112 protruding from the central body 113 of the trip lever 110 pushes on the second operative surface 104 of said plunger 101 and moving it back from said second operating position to said first resting position (i.e. the situation of FIG. 2).

[0085] It is clear from the above description that the low voltage power circuit breaker of the present invention, fully achieve the intended aims and solved the above-highlighted problems of the existing electrical cabinets.

[0086] In practice, as previously explained, in the low voltage power circuit breaker of the present invention, the operation quick acting trip device is directly linked to an arc formation in the chamber and linearly dependent upon it. Moreover, the device is substantially free from aging phenomena, much more reliable than the existing systems and makes complicated calibration processes unnecessary.

[0087] Several variations can be made to the low voltage power circuit breaker thus conceived, all falling within the scope of the attached claims. In practice, the materials used and the contingent dimensions and shapes can be any, according to requirements and to the state of the art.