WO2010043487A1

WO2010043487A1 - Low voltage circuit breaker

Info

Publication number: WO2010043487A1
Application number: PCT/EP2009/062558
Authority: WO
Inventors: Ivan Paleari; Andrea Villani; Matteo Chiaravalli; Marco Tinelli; Tommaso Abbattista; Alberto Antoniazzi
Original assignee: Abb S.P.A.
Priority date: 2008-10-15
Filing date: 2009-09-28
Publication date: 2010-04-22
Also published as: CN102187416B; ITMI20081826A1; CN102187416A; IT1391125B1; EP2335260B1; RU2505876C2; EP2335260A1; RU2011119485A

Abstract

There is described a low voltage circuit breaker which comprises a case housing at least one fixed contact and a movable contact engageable with and disengageable from the fixed contact, an actuating mechanism operatively associated with said movable contact, at least a first and a second connection terminal electrically connected respectively to the fixed contact and to the movable contact, and an arc chamber. The arc chamber is positioned between the fixed contact and a conducting element having a first end electrically connected to the second connection terminal and a second end terminating with a bottom side. The arc chamber comprises a plurality of shaped conducting plates interposed between the fixed contact and the second end of the conducting element. Moreover, a body comprising a second insulating case which encloses an element made of ferromagnetic material is positioned adjacent to the plurality of shaped conducting plates, and defines a space for passage of the movable contact during movement thereof between the closed position and the open position.

Description

LOW VOLTAGE CIRCUIT BREAKER DESCRIPTION

The present invention relates to a low voltage circuit breaker, for example for domestic environments.

It is known that low voltage circuit breakers usually comprise a case containing one or more poles, associated with each of which are at least one pair of contacts reciprocally engageable with and disengageable from one another. Prior art circuit breakers also comprise control means which cause the relative movement of said pairs of contacts so that they can assume at least a first engaged position (circuit closed) and a second separated position (circuit open).

Generally the pairs of reciprocally engageable/disengageable contacts are composed of first elements, substantially fixed (fixed contacts) and second movable elements (movable contacts). The control means instead comprise actuating mechanisms which terminate, for example, in a main shaft operatively connected to said movable contacts.

Moreover, at least one arc chamber is generally associated with each pole of the circuit breaker, i.e. a region of space made particularly suitable to facilitate interruption of the electrical arc. Arc chambers can be simple regions produced in the circuit breaker case, or can comprise various modular elements, for example structured as cases made of insulating material provided with arc splitter plates.

As it is known, during the useful life of a circuit breaker, phenomena which expose the circuit breaker and the network to particularly heavy stresses can occur. This happens in the first place when the circuit breaker is required to withstand, even for short periods, currents greater than the rated values. The time during which the circuit breaker and the electrical network are exposed to an overcurrent (i.e. an overload or short circuit) generally depends on the time required by protection devices to effectively make the circuit breaker safe, i.e. to interrupt the overcurrent.

As it is known, in order to limit the occurrence of damages both to the electrical network and to the actual circuit breaker or parts thereof (contact plates, extinguishing chamber, control, insulating elements), many methods have been tried and established to make opening as rapid and effective as possible. Different solutions include, for example, the use of appropriate control springs and materials suitable to withstand high stresses and temperatures.

Other solutions provide for the use of gasifter means and/or materials, capable of releasing extinguishing substances in proximity of the area in which the electric arc is formed; these means and/or materials are typically triggered by the temperature reached when an electric arc occurs.

Yet other solutions tend to make advantageous use of, or to control in various ways, electromagnetic phenomena which occur in the area of formation and interruption of the electric arc.

Solutions of this type, although being relatively effective from a functional viewpoint, present one or more drawbacks linked to the constructional complexity and/or to insufficient opening speed and/or insufficient control of the electric arc phenomenon.

The main aim of the present invention is therefore to provide a circuit breaker, in particular a low voltage circuit breaker, which overcomes the aforesaid drawbacks.

Within this aim, an object of the present invention is to provide a circuit breaker, in particular a low voltage circuit breaker, which combines relatively simple structure with high performances in terms of opening speed and control of the electric arc phenomenon.

Another object of the present invention is to provide a circuit breaker, in particular a low voltage circuit breaker, in which wear phenomena caused by the electric arc, in particular on the movable contact, are minimized.

A further object of the present invention is to provide a circuit breaker, in particular a low voltage circuit breaker, in which the opening speed of the movable contact is high.

Last but not least object of the present invention is to provide a circuit breaker, in particular a low voltage circuit breaker, which is highly reliable and relatively easy to manufacture at competitive prices.

Therefore, the subject matter of the present invention is a low voltage circuit breaker comprising a first case, housing: at least one fixed contact and a corresponding movable contact engageable with and disengageable from said fixed contact between a first closed position and a second open position; an actuating mechanism operatively associated with said movable contact; at least a first and a second connection terminal electrically connected respectively to said fixed contact and to said movable contact; an arc chamber. The circuit breaker according to the invention is characterized in that said arc chamber is positioned between said fixed contact and a conducting element having a first end electrically connected to said second connection terminal and a second end terminating with a bottom side, said arc chamber comprising a plurality of shaped conducting plates interposed between said fixed contact and the second end of said conducting element; the circuit breaker according to the present invention is also characterized in that a body comprising a second insulating case which encloses an element made of ferromagnetic material is positioned adjacent to said plurality of shaped conducting plates, said body defining a space for passage of said movable contact during movement thereof between said first closed position and second open position.

In this manner, according to mechanisms which will be better described below, the opening speed of the circuit breaker (i.e. the speed with which the movable contact moves from the first closed position to the second open position) is increased due to the electromagnetic effects generated by the element made of ferromagnetic material (similar to the effects generated by poles). Moreover, the particular positioning of the arc chamber between the fixed contact and the conducting element provide a preferential path for the electric arc, moving it away from the movable contact and thus limiting potential damages thereto.

Preferably, said shaped conducting plates are substantially mutually parallel; in particular, the shaped conducting plates preferably present a substantially quadrangular plan with a first base side and a second top side opposite said first side, a notch being produced in said top side, the bottom points of the notches of each shaped conducting plate lying in a same plane orthogonal to the planes in which said shaped conducting plates lie. Even more preferably, the bottom points of the notches of each shaped conducting plate are connected by a broken line.

Preferably, the shaped conducting plates comprise a first plurality of shaped conducting plates the base sides of which lie in a same base plane, and a second plurality of shaped conducting plates the base sides of which are disposed scaled with respect to said base plane in the direction of the bottom side of said second end of the conducting element. More preferably, the top sides of the shaped conducting plates of said first plurality of plates lie in a same top plane parallel to said base plane, the top sides of the shaped conducting plates of said second plurality of plates being disposed scaled with respect to said top plane in the direction of the bottom side of said second end of the conductor element. In this manner, moving of the electric arc away from the movable contact is greatly facilitated.

Preferably, a seat to house an arc chamber is defined in said first case, said seat having a bottom wall with a first surface contiguous to said fixed contact and a second surface contiguous to said first surface and inclined with respect thereto in the direction of the bottom side of said second end of the conducting element.

Advantageously, at least one channel is defined in said first case, which places the inside of the case in communication with the outside, the inlet section of said channel being located in proximity of the second end of said conducting element.

Preferably, the body comprising the element made of ferromagnetic material is substantially U-shaped, with a first and second arm mutually parallel and connected by a third arm perpendicular thereto, the space for passage of said movable contact being defined between said first and second arm and being open in the direction of said fixed contact, while said third arm is facing said conducting element. Advantageously, the body comprising the element made of ferromagnetic material presents a supporting surface to support on the top side at least some of said shaped conducting plates, said supporting surfaces presenting a projection suitable to be inserted in the space defined by the notches produced in the top sides of said shaped conducting plates.

Preferably, said movable contact in said first closed position is located in proximal position with respect to said plurality of shaped conducting plates and with respect to said fixed contact, and in said second open position is located in distal position with respect to said plurality of shaped conducting plates and with respect to said fixed contact. In other words, according to this embodiment the movable contact, in movement thereof between the first closed position and the second open position, tends to move away both from the movable contact and from the shaped conducting plates of the arc chamber, decreasing the risk of providing a preferential path for the electric arc.

Further characteristics and advantages of the present invention will be more apparent from the description of preferred, but not exclusive, embodiments of the present invention shown by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 shows a perspective sectional view of a portion of low voltage circuit breaker according to the present invention.

- Figure 2 shows some components of the arc chamber of the circuit breaker of Figure 1;

- Figure 3 shows in detail some components of Figure 2;

- Figure 4 shows in detail some components of Figure 3.

With reference to the accompanying figures, there will now be described an embodiment of a low voltage circuit breaker according to the invention, identified with the reference numeral 1.

With reference to Figure 1, the circuit breaker 1 comprises a first case 10 which houses at least one fixed contact 20 and a corresponding movable contact (not shown) engageable with and disengageable from said fixed contact 20 between a first closed position and a second open position, and an actuating mechanism (not shown) operatively associated with said movable contact. The actuating mechanism can be of the type normally used in these applications and therefore will not be described in detail below. Moreover, at least a first connection terminal (not shown), electrically connected to said fixed contact 20, for example through the connection terminal 21 of the fixed contact 20, and a second connection terminal 30, electrically connected to said movable contact, are positioned in the case.

One of the peculiar characteristics of the circuit breaker 1 according to the invention is that it comprises an arc chamber 40 which is positioned between said fixed contact 20 and a conducting element 50 (arc guide element) having a first end 51 electrically connected to said second connection terminal 30 and a second end 52 terminating with a bottom side 53. As will be more apparent below, the conducting element 50 forms a preferential circuit element for the electric arc, preventing the arc from closing on the movable contact during the opening step.

The arc chamber 40 comprises a plurality of shaped conducting plates 41 which are interposed between said fixed contact 20 and the second end 52 of said conducting element 50. The circuit breaker 1 according to the present invention also presents a body 60, comprising a second insulating case 61 which encloses poles made of ferromagnetic material (not shown as enclosed inside the case 61). The body 60 is positioned adjacent to said plurality of shaped conducting plates 41 and defines a space 65 for passage of said movable contact during movement thereof between said first closed position and second open position.

In practice, the movable contact, during movement thereof between the closed position and the open position (and vice versa), moves inside the space 65. In closed circuit conditions or in the presence of electric arc, the electromagnetic effect due to the currents which flow in the circuit and to the presence of the poles (ferromagnetic element of the body 60) attracts the movable contact towards the open position, thereby contributing towards speeding up the opening operation.

With reference to Figures 3 and 4, the shaped conducting plates 41 are preferably substantially mutually parallel. More preferably, according to the embodiment shown, the shaped conducting plates 41 present a substantially quadrangular plan, with a first base side 411 and a second top side 412, which is opposite said first side 411. A notch 413, which in the embodiment shown in the figure is substantially V-shaped, is advantageously produced in said top side 412.

The configuration of the notches 413 in the various shaped conducting plates 41 is such that preferably the bottom points 414 of the notches 413 of each shaped conducting plate 41 lie in a same orthogonal plane to the planes on which said shaped conducting plates 41 lie. In other words, in the case in which the notches 413 are V-shaped, the lower vertices of the V-shaped notches, regardless of the opening and depth of the notch, all lie in a same plane which is orthogonal to the planes in which the plates 41 lie.

With reference to Figures 1 and 2, the positioning of the plates and/or the depth of the notches are preferably such that the bottom points 414 of the notches 413 of each shaped conducting plate 41 do not all lie in a straight line, but are connected by a broken line. As can be seen from the accompanying figures, this broken line is descending, in the sense that, at least from a certain point onwards, the bottom points 414 of the notches 413 are progressively spaced along a first direction (said distance corresponding to the pitch with which the shaped conducting plates 41 are positioned) and progressively spaced along a second direction orthogonal to the first direction.

This can be achieved by varying the depth of the notches 413 and/or the relative position of the shaped conducting plates 41. With reference to the accompanying figures, in this latter case, particularly advantageous, the shaped conducting plates 41 comprise a first plurality of shaped conducting plates 41a the base sides 411 of which lie in a same base plane, and a second plurality of shaped conducting plates 41b the base sides 411 of which are disposed scaled with respect to said base plane in the direction of the bottom side 53 of said second end 52 of the conducting element 50. Preferably, also the top sides 412 of the shaped conducting plates of the first plurality of plates 41a lie in a same top plane parallel to said base plane, while the top sides 412 of the shaped conducting plates of the second plurality of plates 41b are disposed scaled with respect to said top plane in the direction of the bottom side 53 of said second end 52 of the conducting element 50.

From a practical viewpoint, this can be achieved by using for the first plurality of plates 41a, shaped conducting plates (identical in dimension to one another) positioned in succession in the same relative position, and for the second plurality of plates 41b, shaped conducting plates positioned at a constant pitch but at different heights, i.e. disposed scaled along the same direction.

For example, with reference to the accompanying figures, starting from the position closest to the fixed contact 20, a first sub-assembly of plates 41 (for example the first three plates 41) of the first plurality of plates 41a have the same dimensions and shape (including the dimension and shape of the notch 413). This is followed by a second sub-assembly of plates 41 (i.e. the subsequent four plates 41) of the first plurality of plates 41a, which have the same dimension but a different shape, i.e. with progressively deeper notches 413. Finally, this is followed by plates of the second plurality of plates 41b (three plates in the example) which are disposed at different heights, i.e. scaled at a distance progressively closer to the bottom side 53 of the second end 52 of the conductor element 50.

In this manner, starting from the movable contact 20 the space defined by the notches 413 of the shaped conducting plates 41 is progressively curved in the direction of the bottom side 53 of the second end 52 of the conducting element 50. In fact, as can be seen from Figures 1 and 2, the movable contact 20 and the terminal part (bottom side 53) of the second end 52 of the conducting element 50 are positioned at different heights, with respect to a transverse view of the circuit breaker 1. This contributes considerably towards providing a preferential path for the electric arc, preventing it from closing on the movable contact with consequent problems of wear thereof.

Conveniently, the plates 41 are preassembled together through packing them between a first 45 and a second 46 insulating plate, provided with first coupling means (for example holes) coup lab Ie with corresponding second coupling means (for example protrusions) positioned on opposite lateral edges of said shaped conducting plates 41. However, other forms of assembly are also possible.

With reference to Figure 1 , a seat for housing an arc chamber 40 is preferably defined in said first case 10, said seat presenting a bottom wall with a first surface (not visible as hidden by the insulating plate 45) contiguous to said fixed contact and a second surface 12 contiguous to said first surface and inclined with respect thereto in the direction of the bottom side 53 of the second end 52 of the conducting element 50. This allows advantageous and convenient positioning of the shaped conducting plates 41 in the housing seat.

Moreover, at least one channel 15 is preferably defined in the first case 10, placing the inside of the case in communication with the outside, the inlet section 16 of said channel 15 being located in proximity of the second end 52 of the conducting element 50. In this manner, the gases which develop subsequent to the occurrence of electric arcs are easily released to the outside of the case 10, decreasing the risks of damage to the circuit breaker 1 and to the devices housed inside the case 10.

With reference in particular to Figure 3, the body 60 is preferably substantially U- shaped, with a first 63 and second 62 arm, mutually parallel and connected by a third arm 64 perpendicular thereto. The space 65 for passage of said movable contact is therefore in this case defined between said first 63 and second 62 arm and is open in the direction of said fixed contact 20, while the third arm 64 is facing said conducting element 50.

Moreover, the body 60 preferably presents a supporting surface 66 to support on the top side 412 at least some of said shaped conducting plates 41; the supporting surface 66 conveniently presents a projection 67 suitable to be inserted in the space defined by the notches 413 produced in the top sides 412 of said shaped conducting plates 41.

It has in fact been found experimentally that this structure is particularly advantageous in terms of opening speed of the movable contact, due to the electromagnetic effects described previously.

From an operational viewpoint, the movable contact in the first closed position is located in proximal position both with respect to the plurality of shaped conducting plates 41 and with respect to the fixed contact 20, while in the second open position it is located in distal position both with respect to said plurality of shaped conducting plates 41 and with respect to said fixed contact 20. In other words, during the opening movement (i.e. passage from the first closed position to the second open position), the movable contact moves away both from the fixed contact 20 and from the plurality of shaped conducting plates substantially according to the direction of the arrow 100 of Figure 1. As the particular structure of the arc chamber (shape, dimensions and positioning of the shaped conducting plates 41) and the reciprocal positioning of the fixed contact 20 and of the second end 52 of the conducting element 50 tend to guide the electric arc in the opposite direction with respect to that of the arrow 100, the risks of the electric arc closing on the movable contact are further decreased.

As can be seen from the description above, the low voltage circuit breaker according to the present invention fully achieves the intended aim and objects.

In particular, the presence of the body 60 comprising a ferromagnetic element allows the opening movement of the contacts to be speeded up. The risks of the arc closing on the movable contact, and consequent progressive or immediate damage thereto, are minimized by the structure of the arc chamber 40 and by the shape and positioning of its components.

It must also be emphasized that the system is essentially composed of a series of sub- assemblies (body 60; shaped conducting plates 41, and insulating plates 45 and 46; fixed contact 20 and movable contact; conducting element 50) which are relatively easy to manufacture and assemble.

On the basis of the description provided, other characteristics, modifications or improvements are possible and evident to a person skilled in the art. These characteristics, modifications and improvements should therefore be considered a part of the present model. In practice, the materials used and the contingent dimensions and forms can be any, according to requirements and to the state of the art.

Claims

1. Low voltage circuit breaker (1) comprising a first case (10) housing at least one fixed contact (20) and a corresponding movable contact engageable with and disengageable from said fixed contact (20) between a first closed position and a second open position, an actuating mechanism operatively associated with said movable contact, at least a first and a second (30) connection terminal electrically connected respectively to said fixed contact (20) and to said movable contact, an arc chamber (40), characterized in that said arc chamber (40) is positioned between said fixed contact (20) and a conducting element (50) having a first end (51) electrically connected to said second connection terminal (30) and a second end (52) terminating with a bottom side (53), said arc chamber (40) comprising a plurality of shaped conducting plates (41) interposed between said fixed contact (20) and the second end (52) of said conducting element (50), a body (60) comprising a second insulating case (61) which encloses an element made of ferromagnetic material being positioned adjacent to said plurality of shaped conducting plates (41), said body (60) defining a space (65) for passage of said movable contact during movement thereof between said first closed position and second open position.

2. Low voltage circuit breaker (1) as claimed in claim 1, characterized in that said shaped conducting plates (41) are substantially mutually parallel.

3. Low voltage circuit breaker (1) as claimed in claim 2, characterized in that said shaped conducting plates (41) present a substantially quadrangular plan with a first base side (411) and a second top side (412) opposite said first side (411), a notch (413) being produced in said top side (412), the bottom points (414) of the notches (413) of each shaped conducting plate (41) lying in a same plane orthogonal to the planes in which said shaped conducting plates (41) lie.

4. Low voltage circuit breaker (1) as claimed in claim 3, characterized in that the bottom points (414) of the notches (413) of each shaped conducting plate (41) are connected by a broken line.

5. Low voltage circuit breaker (1) as claimed in claim 3 or 4, characterized in that said shaped conducting plates (41) comprise a first plurality of shaped conducting plates (41a) the base sides (411) of which lie in a same base plane, and a second plurality of shaped conducting plates (41b) the base sides (411) of which are disposed scaled with respect to said base plane in the direction of the bottom side (53) of said second end (52) of the conducting element (50).

6. Low voltage circuit breaker (1) as claimed in claim 5, characterized in that the top sides (412) of the shaped conducting plates of said first plurality of plates (41a) lie in a same top plane parallel to said base plane, the top sides (412) of the shaped conducting plates of said second plurality of plates (41b) being disposed scaled with respect to said top plane in the direction of the bottom side (53) of said second end (52) of the conductor element (50).

7. Low voltage circuit breaker (1) as claimed in one or more of the preceding claims, characterized in that a seat for housing an arc chamber (40) is defined in said first case (10), said seat having a bottom wall with a first surface contiguous to said fixed contact and a second surface (12) contiguous to said first surface and inclined with respect thereto in the direction of the bottom side (53) of said second end (52) of the conducting element (50).

8. Low voltage circuit breaker (1) as claimed in one or more of the preceding claims, characterized in that at least one channel (15) is defined in said first case (10), which places the inside of the case in communication with the outside, the inlet section (16) of said channel (15) being located in proximity of the second end (52) of said conducting element (50).

9. Low voltage circuit breaker (1) as claimed in one or more of the preceding claims, characterized in that said body (60) is substantially U-shaped, with a first (63) and second (62) arm, mutually parallel and connected by a third arm (64) perpendicular thereto, said space (65) for passage of said movable contact being defined between said first (63) and second (62) arm and being open in the direction of said fixed contact (20), said third arm (64) facing said conducting element (50).

10. Low voltage circuit breaker (1) as claimed in one or more of claims 3 to 9, characterized in that said body (60) presents a supporting surface (66) to support on the top side (412) at least some of said shaped conducting plates (41), said supporting surface (66) presenting a projection (67) suitable to be inserted in the space defined by the notches (413) produced in the top sides (412) of said shaped conducting plates (41).

11. Low voltage circuit breaker (1) as claimed in one or more of the preceding claims, characterized in that said movable contact in said first closed position is located in proximal position with respect to said plurality of shaped conducting plates (41) and with respect to said fixed contact (20), and in said second open position it is located in distal position with respect to said plurality of shaped conducting plates (41) and with respect to said fixed contact (20).