Abstract
The invention relates to a method and a device for cutting off electric current. The device comprises at least one fixed contact and at least one moving contact that can move between a closed position and an open position, and at least one permanent magnet mounted together with the moving contact, such that the permanent magnet and the moving contact are able to move at the same time. The magnetic field of the magnet interferes with the area where the arc occurs and moves with the moving contact along its path, so with a small number of magnets, arc quenching capacity increases. The method of the invention comprises moving a permanent magnet through the area where an electrical arc occurs between a moving contact and a fixed contact, such that the generated magnetic field runs through at least part of the area where the arc occurs.
Claims
1. A device for cutting off an electric current comprising at least one fixed contact and at least one moving contact that can move between a closed position in which it establishes electrical continuity with the fixed contact and an open position in which it prevents current circulation, and at least one permanent magnet placed to generate a magnetic field that interferes with an area where an electrical arc occurs between the fixed contact and the moving contact to help in quenching an electrical arc, characterized in that the permanent magnet is mounted together with the moving contact, such that the permanent magnet and the moving contact are able to move at the same time.
2. The device according to claim 1, comprising two fixed contacts and a moving contact arranged for coming into contact with the fixed contacts, and in that it has two permanent magnets mounted in the moving contact such that the magnetic field of each of them, interferes respectively with an area where an electrical arc occurs between each of the fixed contacts and the moving contact.
3. The device according to claim 1, where the permanent magnet or magnets are positioned in the moving contact, such that in the electrically closed position, the permanent magnets are proximal to an end of each fixed contact and the magnetic field passes through the space between the fixed contact and the moving contact.
4. The device according to claim 2, further comprising a support made of an electrically isolating material fixed to the moving contact, and where the permanent magnet or magnets are mounted in said support such that they are electrically isolated from the moving contact.
5. The device according to claim 4, where said support has two clamp-shaped ends, and where each of the magnets is housed in one of the ends of the support.
6. The device according to claim 1, further comprising a moving actuator made of an isolating material, where the at least one moving contact is mounted in the actuator, and where the magnets are housed at least partly inside the actuator.
7. The device according to claim 1, further comprising a moving actuator made of an isolating material, where the at least one moving contact is mounted in the actuator, and where the magnets are mounted in the actuator and housed at least partly inside the actuator.
8. The device according to claim 6, where the actuator is a linear slide that slides with respect to a longitudinal axis, or where the actuator is a rotor rotating on one and the same plane with respect to an axial axis, or where the actuator is a rotor that can move in a helicoidal manner with respect to an axial axis.
9. The device according to claim 1, where the magnets are cylindrical and have diametric polarization.
10. The device according claim 1, having two or more poles, where each pole is formed by a pair of fixed contacts, a moving contact and two permanent magnets.
11. A method for cutting off an electric current that comprises moving a moving contact with respect to a fixed contact to interrupt electric current circulation, and, by means of a permanent magnet, to apply a magnetic field that interferes with an area where an electrical arc occurs between the fixed contact and the moving contact, to help in quenching the electrical arc, characterized in that it further comprises moving the permanent magnet through the area where an electrical arc occurs, such that the generated magnetic field runs through at least part of the area where the arc occurs.
12. The method according to claim 11, which comprises moving the permanent magnet and the moving contact together.
13. The method according to claim 11, where the permanent magnet and the moving contact move linearly with respect to a longitudinal axis, or rotationally on one and the same plane with respect to an axial axis, or helicoidally with respect to an axial axis.
Description
DESCRIPTION OF THE DRAWINGS
[0027] Several preferred embodiments of the invention are described below in reference to the attached drawings, where:
[0028] FIG. 1 shows several perspective views of an embodiment of a linear breaker according to the invention, where drawing (A) corresponds to a one-pole breaker; drawing (B) shows the breaker with several poles; drawing (C) is a depiction similar to that of drawing (B) but incorporating a slide; drawing (D) is an enlarged detail in the closed position of the breaker; and drawing (E) is an enlarged detail of the dynamic blow-out process by means of a magnetic field in an open position of the moving contact. In drawings (A, B, C) the arrows indicate the linear movement of the moving contacts. In drawings (D, E), the multiple arrows starting from the magnet represent the magnetic field (B). The movement of the magnetic field “B” along with the magnet can be seen in drawings (D, E).
[0029] FIG. 2 shows two perspective views of the set of permanent magnets. In drawing (A) they are separated from the isolating support, and in drawing (B) they are coupled in the support.
[0030] FIG. 3 shows several perspective views of an embodiment of a rotating breaker according to the invention, where drawing (A) shows the breaker with the rotor; drawing (B) is the same as the previous depiction but without a rotor so that the position of the magnets can be seen; drawing (C) is an enlarged detail in the closed position of the breaker; and drawing (D) is an enlarged detail of the dynamic blow-out process by means of a magnetic field. In drawing (A), the arrow around the “X” axis indicates the rotational movement of the rotor. In drawings (C, D), the multiple arrows starting from the magnet represent the magnetic field (B).
[0031] FIG. 4 shows a perspective view of another embodiment similar to that of FIG. 3, but in which the rotor moves in a helicoidal manner.
[0032] FIG. 5 depicts common general knowledge about the behavior of an electrical arc in a magnetic field according to the Lorentz force law and the left-hand rule.
PREFERRED EMBODIMENT OF THE INVENTION
[0033] FIG. 1A shows an embodiment of a one-pole linear breaker (1) according to the invention, formed by two facing fixed contacts (2a, 2b) and one moving contact (6) arranged between the fixed contacts (2a, 2b) that can move linearly and reciprocally along an “X” axis. The moving contact (6) is the one that can move between a closed position in which it establishes electrical continuity with the fixed contacts (2a, 2b), and an open position such as the one shown in FIG. 1A, in which it prevents current circulation.
[0034] The breaker (1) has two cylindrical permanent magnets (4a, 4b), which are mounted together with the moving contact (6) on one of its faces by means of a support (5) made of an isolating material. This support (5) is clamp-shaped at the ends thereof, such that the magnets (4a, 4b) are retained by elastic pressure at said ends, as depicted with more detail in FIG. 2.
[0035] The permanent magnets (4a, 4b) have diametric polarization, i.e., a semi-cylinder of the magnet has one polarity, and the other semi-cylinder has the opposite polarity, as shown in FIG. 2. The position of the magnets in reference to their polarity is chosen depending on the current circulation direction in the case of direct current, and on the direction towards which the arc is to be elongated.
[0036] The support (5) is fixed on the moving contact (6), such that the magnetic field generated by each of the magnets (4a, 4b) interferes respectively with each area where an electrical arc occurs (7a, 7b) between each of the fixed contacts and the moving contact. Both the moving contact (6) and the fixed contacts (2a, 2b) are metal flats with a generally rectangular shape with upper and lower faces. As seen in the drawing, the permanent magnets (4a, 4b) are arranged on the upper face of the moving contact (6) which is also the face intended for coming into contact with the lower face of the fixed contacts (2a, 2b).
[0037] In the embodiment of FIG. 1B, the breaker (1) is multi-pole, in which each of its poles (1a, 1b, 1c, 1d) is an individual breaker like the one depicted and described above in relation to FIG. 1A. A particularity of this embodiment is that the relative position between the moving contact and the fixed contacts of each pole alternate from one pole to the adjacent poles. It can be seen in this embodiment that, as in the case of the poles (1a, 1c), the upper face of the moving contacts (6) is the one that has the magnets and is intended for coming into contact with the lower face of the corresponding fixed contacts. In the case of the poles (1b, 1d), the position of the magnets and moving contacts is the opposite with respect to the poles (1a, 1c).
[0038] As shown in FIG. 10, the breaker (1) has an actuator, in this case a slide (8) having reciprocal linear movement along the “X” axis. The moving contacts (2a, 2b) with their respective magnets (4a, 4b) are mounted in the slide (8), such that the magnets are housed inside the slide (8) but are visible from outside the slide (8) which has side windows for that purpose.
[0039] FIG. 1D depicts the magnetic blow-out process which is obtained with the arrangement of magnets of this embodiment. It is known that the behavior of an electrical arc in a magnetic field obeys the Lorentz force law and forms a three-vector orthogonal system (FIG. 5B). As a practical method for determining the direction of the force, the left-hand rule is used (FIG. 5A), where: “B” is the direction of the magnetic field generated by a magnet, “I” is the direction of the electric current, and “F” is force driving the electrical arc due to the effect of the magnetic field. If the direction of B or I changes, the direction of the resulting movement F changes on the same Z axis.
[0040] FIG. 1E shows a permanent magnet (4a) placed to generate a magnetic field (B) which interferes with the electrical arc occurring between the fixed contact (2a) and the moving contact (6), such that taking into account the direction of the field (B) and the current (I), a force (F) is generated in the direction orthogonal to a plane on which the moving contacts (2a, 2b) move, so that force (F) elongates the arc towards the upper part of the figure until it breaks. Since the magnet (4a) moves at the same time as the moving contact (6) and the slide (8), the magnetic field (B) also moves along with the moving contact (6).
[0041] The embodiment of FIG. 3 consists of a rotating breaker in which instead of being a slide, the actuator is a rotor (9) made of an isolating material that can rotate reciprocally on one and the same plane around its “X” axis. The moving contact (6) and the permanent magnets (4a, 4b), are mounted in the rotor (9) and therefore move together with the rotor (9) between the opened and closed positions of the breaker.
[0042] The embodiment of FIG. 4 is similar to the embodiment of FIG. 3, but the rotor (9) moves in a helicoidal manner with respect to the axial axis “X” of the rotor, also reciprocally between the opened and closed positions of the breaker.
[0043] The blow-out process of the embodiments of FIGS. 3 and 4 is similar to that of FIG. 1, but the magnets move rotationally and helicoidally, respectively.
[0044] As an alternative to the use of a support (5) for mounting the magnets (4a, 4b) with the moving contact (6), the magnets can be fixed to the actuator, i.e., to the slide (8) in the embodiment of FIG. 1 or to the rotor (9) in the embodiments of FIGS. 3 and 4, such that the magnets (4a, 4b) are mounted together with the moving contact (6) through the slide or of the rotor.
[0045] The method of the invention is depicted, for example, in FIGS. 1D, 1E, 3C and 3D. It can particularly be seen in FIGS. 1D and 3C how both in the device and in the method of the invention a magnetic field (B) is being applied to the space between the fixed contacts and the moving contact at all times, even before starting the process of opening the breaker by starting to move the moving contact (6), so in the very instant the electrical arc starts to occur there is already a magnetic field applied in that area making the formation thereof complicated, thereby increasing the breaking capacity of the breaker and reducing the quenching time.
[0046] It is also seen in FIGS. 1D, 1E, 3C, and 3D how at the same time the moving contact (6) moves with respect to the fixed contacts (2a, 2b) to open the breaker and interrupt an electric current circulation, the magnet or permanent magnets (4a, 4b) mounted together with the moving contact (6) also move, so the generated magnetic field (B) also moves, performing the same movement as the fixed contacts, and running through the area where the arc occurs between the fixed contact and the moving contact to help in quenching the electrical arc.
