WO2003001549A1

WO2003001549A1 - Miniature circuit breaker pole

Info

Publication number: WO2003001549A1
Application number: PCT/EP2002/007041
Authority: WO
Inventors: Alberto Antoniazzi; Franco Rinco
Original assignee: Abb Service S.R.L.
Priority date: 2001-06-22
Filing date: 2002-06-21
Publication date: 2003-01-03
Also published as: CN1465084A; EP1399940B1; CN1320582C; DE60209126D1; EP1399940A1; ATE317589T1; DE60209126T2; ITMI20011326A1; IT1325891B; ITMI20011326A0

Abstract

A single-pole miniature circuit breaker, comprising:-- a casing on which there are two terminals for connection, in input and in output from the circuit breaker, to a phase of a low-voltage electric circuit, said casing having a front wall from which an actuation lever protrudes, a rear wall for coupling to a supporting element, two side walls that are substantially mutually parallel and whose distance is equal to a base module M, an upper wall and a lower wall, inside the casing there being provided:--fixed and moving contact means that can be mutually separated in order to interrupt the flow of current in said phase;-- a kinematic mechanism that is operatively connected to said actuation lever and is suitable to move said moving contact means;--electric are quenching means;--a device for protection against short-circuits, which comprises a coil and a moving striker suitable to interact operatively with said kinematic mechanism;-- a device for protection against overloads, which comprises a heat-sensitive element that is suitable to interact operatively with the kinematic mechanism; characterized in that said fixed and moving contact means comprise a first pair of contacts, having a first fixed contact and a first moving contact, and a second pair of contacts, having a second fixed contact and a second moving contact, a first arc quenching chamber and a second arc quenching chamber being respectively associated with said first and second pairs of contacts, said first and second pairs of contacts being electrically series-connected to each other and being crossed by currents that have the same direction.

Description

MINIATURE CIRCUIT BREAKER POLE DESCRIPTION

The present invention relates to a miniature circuit breaker pole for low- voltage applications, i.e., with operating voltages up to 1000 volts. As is known, low- voltage electrical systems use appropriate protection devices, generally designated in the art as modular circuit breakers or miniature circuit breakers.

These circuit breakers are dimensionally characterized in that their width is equal to, or a multiple of, the width of a standard module, depending on the number of poles used, as prescribed by relevant international standards, and are normally used by mounting them on appropriate supporting elements, for example DIN rails, which are in turn usually placed within appropriately provided electrical cabinets. One of the main requirements of modular circuit breakers, be they of the residual-current or magnetothermal type, is the ability to ensure adequate levels of protection against any faults or malfunctions occurring in the system with rapid tripping times while occupying the smallest possible space. Specifically because of the type of application for which they are meant, it is particularly appreciated that the space they occupy is as small as possible, so that for an equal space available it is possible to increase the number of devices that can be used or to reduce the space required for an equal number of devices. This need is particularly important in the case of miniature or magnetothermal modular circuit breakers of the kind to which the present invention relates, because these devices are conceived so as to provide an adequate level of protection both against possible overload conditions and, most of all, against currents caused by short-circuit faults; in the case of a short circuit, the currents involved in fact usually reach very high values and their interruption requires adequate electrical and mechanical strength characteristics, which require, in order to be obtained, the use of components having adequate dimensions and arranged according to specific configurations, ultimately affecting the overall dimensions of the circuit breaker and particularly its width. Currently, in known types of miniature circuit breaker, in order to achieve an acceptable compromise between the size requirement and the performance provided, particularly as regards the breaking capacity in short-circuit conditions, on the one hand solutions have been developed in which the breaking capacity has been increased by increasing the dimensions of the components used and by adopting particular constructive configurations, accordingly increasing the width of the circuit breaker with respect to the width of a standard base module, and on the other hand said standard width has been maintained but circuit breakers with a reduced breaking capacity have been marketed. The aim of the present invention is to provide a low- voltage miniature circuit breaker pole that allows to obviate the drawbacks of the known art and which in particular, with respect to known modular circuit breakers having a standard width, allows to increase considerably its performance, more specifically its breaking capacity in short-circuit conditions, without thereby requiring a corresponding increase in dimensions and particularly in width. This aim and other objects that will become apparent hereinafter are achieved by a single-pole miniature circuit breaker, comprising:

-- a casing on which there are two terminals for connection, in input and in output from the circuit breaker, to a phase of a low- voltage electric circuit, said casing having a front wall from which an actuation lever protrudes, a rear wall for coupling to a supporting element, two side walls that are substantially mutually parallel and whose distance is equal to a base module M, an upper wall and a lower wall, inside the casing there being provided: ~ fixed and moving contact means that can be mutually separated in order to interrupt the flow of current in said phase;

-- a kinematic mechanism that is operatively connected to said actuation lever and is suitable to move said moving contact means;

— electric arc quenching means; — a device for protection against short-circuits, which comprises a coil and a moving striker suitable to interact operatively with said kinematic mechanism;

~ a device for protection against overloads, which comprises a heat-sensitive element that is suitable to interact operatively with the kinematic mechanism; characterized in that said fixed and moving contact means comprise a first pair of contacts, having a first fixed contact and a first moving contact, and a second pair of contacts, having a second fixed contact and a second moving contact, a first arc quenching chamber and a second arc quenching chamber being respectively associated with said first and second pairs of contacts, said first and second pairs of contacts being electrically series-connected to each other and being crossed by currents that have the same direction.

In this manner, the circuit breaker according to the invention is capable of providing a functional performance that is distinctly improved with respect to the known art while providing optimized space requirements.

Further characteristics and advantages of the invention will become apparent from the description of preferred but not exclusive embodiments of the circuit breaker according to the invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein:

Figure 1 is a perspective view of the circuit breaker according to the invention;

Figure 2 is another perspective view, illustrating in detail the components of the circuit breaker of Figure 1 ;

Figure 3 is a perspective view of the components of the circuit breaker according to the invention, taken from the opposite side with respect to Figure

2; Figure 4 is a schematic view of the arrangement of the lines of flux of the magnetic fields outside the arc in overcurrent conditions when the contacts separate;

Figure 5 is an electrical diagram of the circuit breaker according to the invention.

With reference to the cited figures, the miniature circuit breaker pole according to the invention comprises a casing 1, which has: a front wall 2, from which an actuation lever 3 protrudes, said lever being coupled to the casing so that it can rotate about an appropriately provided pivot; a rear wall 4, which is conveniently shaped so as to facilitate coupling with a supporting guide, not shown, for example a DIN rail; two side walls 5 and 6, which are substantially mutually parallel and whose distance, equal to a base module M, defines the width of the circuit breaker; an upper wall 7 and a lower wall 8. Furthermore, on the casing there are two corresponding terminals 9, only one of which is partially visible in Figure 1, with corresponding clamping terminals, for connection in input and in output from the circuit breaker with the phase of a low- voltage electric circuit that said pole is meant to protect; the terminals 9 can be provided at the upper and lower walls, as shown in Figure 1, or can be arranged differently. In particular, said base module, taking into account normal manufacturing

+ 0.5 tolerances, is equal to 17,5 ( ) mm, as prescribed by the DIN 43880

standard.

The functional components of the circuit breaker are arranged inside the casing 1, in the manner that will become apparent from the description that follows, and comprise: fixed and moving contact means, which can be mutually separated in order to interrupt the flow of current in the phase of the circuit; a kinematic mechanism, per se known, generally designated by the reference numeral 10, which is operatively connected to the actuation lever 3 and is suitable to move the moving contact means; electric arc quenching means; a device for protection against any short-circuit faults; and a device for protection against overloads. In particular, according to embodiments that are widely known in the art and are therefore not described in detail, the device for protection against short- circuit faults is a device of the electromagnetic type and comprises a coil 11, which is wound around a supporting element 12, and a striker 13, which is operatively associated with the coil 11 and is shown only partially in Figures 2 and 3; said striker 13 is arranged inside the winding of the coil 11 and can move along the direction connecting the upper wall 7 and the lower wall 8, so that in short-circuit conditions it interacts operatively with the kinematic mechanism 10, actuating it and ultimately causing the separation of the contacts and the interruption of the flow of current in the phase to be protected. In turn, the device for protection against overloads comprises a heat-sensitive element 14, for example a bimetallic lamina, which is electrically connected to the connection terminal 9; said element 14 can interact operatively with the kinematic mechanism 10, so as to cause it to trip when an overload exceeding a preset limit occurs and thus also cause separation of the contacts and interruption of the flow of current in the phase. Advantageously, in the embodiment of the circuit breaker according to the invention, the fixed and moving contact means comprise a first pair of contacts, provided with a first fixed contact 15 and a first moving contact 16, which is electrically connected to the element 14 by means of a suitable conductor, typically a flexible braid 19, and a second pair of contacts, which provides a second fixed contact 17 and a second moving contact 18, the two pairs of contacts 15-16 and 17-18 being electrically connected in series to each other in the manners described in detail hereinafter. In particular, as shown in Figures 2 and 3, the first fixed contact 15 and the second fixed contact 17 are arranged side by side at a suitable distance along the line that connects the side walls 5 and 6, i.e., along the shortest dimension of the circuit breaker, i.e., the width M; furthermore, the contacts 15 and 17 are arranged so that the surfaces that they offer to electrical coupling to the corresponding moving contacts face the wall 8 and therefore lie transversely to the front wall and rear wall of the casing, as well as to the side walls. In turn, the first moving contact 16 and the second moving contact 18 are advantageously provided by means of two contoured conducting bodies, which are structurally mutually separated and are mounted so as to be spaced on a contact holder 29 of the kinematic mechanism 10, at a distance that corresponds to the distance between the fixed contacts 15 and 17; said moving contact holder 29 is arranged inside the casing and rotates about an axis 20 that is directed along a line that connects the side walls 5 and 6 and is therefore substantially parallel to the rotation shaft 21 of the actuation lever 3. In combination, in the embodiment of the circuit breaker according to the invention the electric arc quenching means comprise two arc quenching chambers 22 and 23, each of which is operatively associated with a pair of contacts, designated by the reference numerals 15-16 and 17-18 respectively; said arc quenching chambers 22 and 23 are arranged mutually side by side proximate to the rear wall 4, so that each one is adjacent to the corresponding side wall 5 and 6, and are separated by a partition 24 made of plastic material that is interposed between them. In order to optimize the guide and quenching of any electric arcs, two corresponding arc guide conductors, designated by the reference numerals 25-26 and 27-28 respectively, are furthermore associated with each chamber 22 and 23. In particular, a first arc guide conductor 25 is connected electrically to the connection terminal 9 and is shaped so that it has a free end arranged at the base of the chamber 22, while a second arc guide conductor 26, on which the first fixed contact 15 is fixed, is connected electrically to the coil 11 at one end and has another end that is free and arranged at the upper part of the chamber 22. In turn, the two arc guide conductors associated with the chamber 23 are constituted by a third conductor 27, which is electrically connected by means of a second flexible braid 19 to the second moving contact 18 and is configured so as to have a free end arranged at the base of the chamber 23, and by a fourth conductor 28, on which the second fixed contact 17 is fixed, said second fixed contact being electrically connected to the second terminal 9 and having a portion arranged at the upper part of the chamber 23. Advantageously, the circuit breaker according to the invention uses a supplemental conductor 30, which has a first end connected to the coil 11 and a second end connected to the arc guide conductor 27 associated with the chamber 23; in particular, in the embodiment shown in Figures 2 and 3, the supplemental conductor has a first portion 31, in which one end is free and connected to the coil and lies at right angles to the axis of said coil, and a second portion, which is contiguous to the first portion 31 and perpendicular thereto, lies along the line that connects the walls 7 and 8, and is arranged so that a portion thereof is laterally adjacent to the coil 11, its free end being connected to the conductor 27. Accordingly, the first fixed contact 15 and the second moving contact 18 are electrically series-connected, with the interposition of the coil 11, the supplemental conductor 30, the arc guiding conductor 27, and the second flexible braid 19, providing the circuit of Figure 5. In this manner, therefore, by virtue of the arrangement of the various components and of the configuration of the electrical connections among the parts, the two pairs of contacts 15-16 and 17-18 are electrically series- connected and are arranged close to each other and so that in normal operating conditions they are crossed by currents that have the same direction. Accordingly, when the contacts separate due to a short-circuit condition, two electric arcs, schematically designated by the reference numeral 40 in Figure 4 and electrically in series to each other, are generated between the pairs of contacts 15-16 and 17-18; accordingly, the pairs of arc guide conductors on which the roots of said arcs 40 move are affected by corresponding magnetic fields whose lines of flux 41 have the same direction and at least partially overlap. In this manner, the magnetic fields cooperate synergistically to generate a force that acts on the arcs and allows their faster and more effective quenching. In particular, by virtue of the presence of the two pairs of contacts and of the overlap of the magnetic fields, the circuit breaker according to the invention is capable of interrupting the flow of current in the phase in two regions that are arranged electrically in series, with a breaking capacity which, indeed by virtue of the synergistic effect mentioned above, is surprisingly high, in some cases even higher than twice the value of the breaking capacity of a single pair of contacts that is part of the pole according to the present invention. In practice it has been found that the circuit breaker according to the invention fully achieves the intended aim, since by virtue of the arrangement of the various components and of the configuration of their mutual electrical connections, it allows to obtain a functional performance that is improved considerably with respect to known circuit breakers of equal dimensions and particularly of equal width. Furthermore, in addition to the above cited advantages, the possibility to have two moving contacts that are structurally mutually separated allows to have protection trippings, albeit limited ones, even when one of the moving contacts has welded itself to the corresponding fixed contact.

The circuit breaker thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept; all the details may furthermore be replaced with other technically equivalent elements. In practice, the materials and the dimensions may be any according to the requirements and the state of the art.

Claims

1. A single-pole miniature circuit breaker, comprising:

- a casing on which there are two terminals for connection, in input and in output from the circuit breaker, to a phase of a low- voltage electric circuit; said casing having a front wall from which an actuation lever protrudes, a rear wall for coupling to a supporting element, two side walls that are substantially mutually parallel and whose distance is equal to a base module M, an upper wall and a lower wall, inside the casing there being provided: ~ fixed and moving contact means that can be mutually separated in order to interrupt the flow of current in said phase;

~ a kinematic mechanism that is operatively connected to said actuation lever and is suitable to move said moving contact means;

~ electric arc quenching means;

~ a device for protection against short-circuits, which comprises a coil and a moving striker suitable to interact operatively with said kinematic mechanism;

~ a device for protection against overloads, which comprises a heat- sensitive element that is suitable to interact operatively with the kinematic mechanism; characterized in that said fixed and moving contact means comprise a first pair of contacts, having a first fixed contact and a first moving contact, and a second pair of contacts, having a second fixed contact and a second moving contact, a first arc quenching chamber and a second arc quenching chamber being respectively associated with said first and second pairs of contacts, said first and second pairs of contacts being electrically series-connected to each other and being crossed by currents that have the same direction.

2. The circuit breaker according to claim 1, characterized in that said base module M is equal to approximately 17.5 mm.

3. The circuit breaker according to claim 1 or 2, characterized in that said first moving contact and said second moving contacts are provided by means of two contoured conducting bodies which are structurally mutually separated.

4. The circuit breaker according to claim 3, characterized in that said first and second moving contacts are mounted so as to be mutually spaced on a contact holder of the kinematic mechanism, said contact holder being arranged in the casing so that it rotates about an axis that lies along a line that connects said side walls.

5. The circuit breaker according to one or more of the preceding claims, characterized in that two corresponding arc guide conductors are associated with said first and second arc quenching chambers, a first one of said arc guide conductors being connected electrically to a first connection terminal and having a free end arranged at an end of the first chamber, a second one of said arc guiding conductors, on which said first fixed contact is fixed, having a first end that is electrically connected to said coil and a second end that is arranged at a second end of the first chamber, a third arc guide conductor being electrically connected, by means of a connection conductor, to the second moving contact and having a free end that is arranged at one end of the second chamber, a fourth guide conductor, on which the second fixed contact is fixed, being connected electrically to a second connection terminal and having a portion arranged at a second end of the second chamber.

6. The circuit breaker according to claim 5, characterized in that said first and second pairs of contacts are arranged close to each other, so that when the respective contacts separate, two corresponding electric arcs form which are arranged electrically in series to each other, said arcs inducing, on said arc guide conductors, corresponding magnetic fields whose lines of flux have the same direction and at least partially overlap.

7. The circuit breaker according to one or more of the preceding claims, characterized in that it comprises a supplemental conductor, which has a first portion, which lies along the line that connects said upper and lower walls and is partially laterally adjacent to the coil, one end being connected to the third arc guide conductor, and a second portion, which is contiguous to the first one and perpendicular thereto and has an end that is connected to said coil.

8. The circuit breaker according to claim 7, characterized in that the first fixed contact and the second moving contact are electrically connected in series, said coil, said supplemental conductor, said third arc guide conductor and said conductor for connection between said third arc guide conductor and said second moving contact being interposed between said first fixed contact and said second moving contact.