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(11) | EP 2 690 639 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method and device for breaking electric currents with arc quenching |
| (57) The invention relates to a method and a device for breaking electric currents with
arc quenching by means of applying constant magnetic fields, whereby the electric
arc quenching is performed more quickly and effectively. The electric switch and/or
circuit breaker device comprises at least two connectable electrical contacts which
can be connected between an electric circuit-breaking position and an electric circuit-making
position, and it incorporates at least one permanent magnet arranged such that at
least part of the magnetic field generated by said permanent magnet passes through
the electric arcing space between said contacts, interfering with said arc to lead
to its quenching.
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Object of the Invention
[0001] The invention relates to a method and a device for breaking electric currents with arc quenching which allows breaking direct or alternating currents regardless of the direction of circulation and device configuration.
[0002] More specifically, the invention relates to a method and to a switch disconnector type breaker device in which constant magnetic fields are applied so that electric arc quenching is performed more quickly and effectively.
Background of the Invention
[0003] Switches of any type or model are devices serving for connecting and disconnecting a load to/from a power supply source. The operation of these switches is based on the application of an external force causing the movement of moving contacts with respect to other fixed contacts. When the circuit is to be closed, the moving contacts are contacted with the fixed contacts, connecting the load and energy source and starting up the corresponding installation. When the circuit is to be opened and the load of the energy source insulated, the opposite process is followed such that the moving contacts are moved away from the fixed contacts, opening the circuit and shutting down the installation as a result.
[0004] Switch disconnectors which are characterized by performing electric circuit-breaking by means of knife-type contacts with self-cleaning action, i.e., the physical contact takes place between surfaces sliding over one another, therefore it tends to mill the imperfections resulting from the arc-over in each opening or closing operation, are known. This contact is reinforced as a result of the joint action of the electromagnetic field generated by the passage of current through the active parts and the action of the springs immobilizing the moving contacts on the fixed contacts. Both effects aid in increasing the pressure between the contacting surfaces improving the electrical performance of the switch, for example, in environments subjected to vibrations.
[0005] Each breaking point is configured by a fixed central contact and two moving contacts immobilizing the central contact. Therefore, there are two breaking points per pole or four breaking points per phase, if preferred. The relative movement between these contacts is generated by means of a jumping mechanism, not depicted in the drawings, responsible for applying the necessary force and pulse to perform the breaking or opening operation.
[0006] An electric arc is produced during the closing or opening process when electric current circulates through the air between the contacts, which damages said contacts. To increase the closing or opening power of the device, the contact reliability must be assured reducing the effects of the electric arc thereon.
[0007] The lesser the wear, the more durable the contacts will be and the more power they withstand. One of the variables to be taken into account for reducing the wear or for increasing the closing and opening power is the duration of the electric arc.
[0008] The shorter the duration of the arc, the less damage will be produced in the apparatus since less energy would have been released during said operation. The duration of the arc does not depend exclusively on the closing or opening speed of the system of moving contacts since the length of the arc itself is another factor to be taken into account for increasing said breaking capacity. The greater the air mass forced to travel though the arc, the greater the insulation offered by the air and, therefore, it will be quenched more quickly.
[0009] There are currently several options to lengthen the arc such as: using arc quenching chambers or deionizing chambers, increasing the physical distance between the fixed contact and the moving contact or using electromagnetic fields. The inclusion of arc quenching chambers in apparatuses is the most widely used system since it meets the most common needs for alternating current, as well as for direct current in conditions of large volumes of air. The second option is normally accompanied by the first, i.e., increasing or maintaining a physical barrier between the moving contacts and the fixed contacts and including arc quenching chambers. Finally, the last alternative is usually preferred for more severe conditions such as in automatic switches and contacts for high level applications in automatic breaking for protection.
[0010] The switches have therein arc quenching chambers in each of the arc quenching areas. There are two chambers in each pole of the switch, demarcated by the space confined between the two casings, the separating partitions and the shuttle. The chambers are in turn made up of an arcing area and a stack of deionizing plates also known as arc quenching chambers. The plates are separated from one another by exchange spaces the function of which is to divide the arc-over voltage.
[0011] The position of the plates is defined so that during the opening operation, the arc preferably jumps between the fixed contact and the closest deionizing plate. This occurs because as the moving contact is gradually separated from the fixed contact, it reaches an instant in which the insulation distance between the fixed contact and the first deionizing plate is less and, therefore, the arc jumps between them since there would be less dielectric resistance. The arc then continues to be transmitted from plate to plate and thus travelling over a longer path.
[0012] The arc is thus more effectively quenched, in addition to being moved further away from the moving contact, since the final insulation obtained is proportional to the length traveled by the arc.
[0013] On the other hand, electric breaker devices are known which use electromagnetic fields for quenching the arc, such that these fields only appear when coils are excited with energy. One of the drawbacks of the coils is their slow response for generating the magnetic field for the blowout, whereas the permanent magnet already generates its own magnetic field and does not need connection for generating a magnetic field. Another drawback of the coils is the possible breakdown of the coil itself or of the connection and disconnection system leading to the failure of the coil to work and not quenching the arc with the consequences that it entails.
Description of the Invention
[0014] The present invention satisfactorily solves the problems described above by means of the subject-matter defined in the attached independent claims.
[0015] The invention relates to a method and a load breaker device for breaking electric currents with arc quenching which allows breaking direct or alternating currents regardless of the direction of circulation and apparatus configuration.
[0016] More specifically, the invention relates to a method and to a switch device, preferably a circuit breaker, in which constant magnetic fields are applied so that the electric arc quenching is performed more quickly and effectively.
[0017] Permanent magnets, i.e., a material continuously generating a magnetic field over time, are used for applying constant magnetic fields. Unlike the switches using electromagnetic fields which only appear when their coils are excited with energy, the use of permanent magnets has the advantage that the application of the magnetic field is constant, regardless of the operation status of the device.
[0018] The material and position of these magnets are chosen so that they do not negatively interfere in the normal operation of the switch disconnector.
[0019] The magnetic field in the arc-over area generates repulsive and or attractive forces over the arc depending on the apparatus configuration. This lengthens the arc due to the magnetic blowout effect and therefore quenches it more quickly and effectively. The arc lengthening direction depends on the direction of circulation of the current in the electric arc and on the polarity of the magnets. Nevertheless, the side towards which it is led is not important since the desired lengthening effect is obtained in both situations.
[0020] Therefore, one aspect of the invention relates to an electric switch and/or circuit breaker comprising at least two connectable electrical contacts which can be connected between an electric circuit-breaking position and an electric circuit-making position in which the two contacts are connected providing electrical continuity. The device incorporates at least one permanent magnet arranged in the device such that at least part of the magnetic field generated by said permanent magnet passes through the electric arcing space between said contacts to interfere with said arc leading to its quenching.
[0021] Another aspect of the invention relates to a method for breaking an electric current by means of an electric breaker switch and/or disconnector which comprises applying a permanent magnetic field in the electric arcing space in the electric circuit-breaking area such that said magnetic field interferes with said arc and leads to its quenching.
Description of the Drawings
[0022] To complement the description that is being made and for the purpose of aiding to better understand the features of the invention according to a preferred practical embodiment thereof, a set of drawings is attached as an integral part of said description in which the following has been depicted with an illustrative and non-limiting character:
Figure 1 shows a perspective view of a 4-pole or phase switch disconnector, with its upper and lower casing coupled together.
Figure 2.- Figure 2A shows a top plan view of the inside of the lower casing of the switch, i.e., with the upper casing removed, in an electric circuit-breaking position of the device, and with the magnets centered with respect to the electrical contacts; Figure 2B shows a plan view of the inside of the upper casing, in which the arrow indicates the direction of movement of the slide in the electric circuit-making direction of the switch disconnector to allow current circulation.
Figure 3.- Figure 3A shows a schematic depiction of an elevational view (according to the direction of the arrow A in Figure 1) of the main elements of the disconnector in an electric circuit-breaking position and with a single magnet centered with respect to the contacts; Figure 3B is a depiction similar to the preceding figure but with a pair of facing magnets; Figure 3C is a depiction similar to that of the preceding figure but in an electric circuit-making position. The dashed and dotted line in this figure schematically depicts the location of the magnetic field with respect to the fixed contacts.
Figure 4.- Figure 4A is a plan view depicting the inside of the lower casing in an electric circuit-making position and with centered magnets; Figure 4B is a plan view depicting the inside of the upper casing in the same operative situation.
Figure 5.- Figures 5A and 5B are depictions similar to those of Figures 2A and 2B respectively, but with the magnets off-centered with respect to the electrical contacts.
Figure 6.- Figures 6A and 6B are depictions similar to those of Figures 3A and 3B respectively, but with the magnets off-centered with respect to the electrical contacts.
Figure 7 is a depiction similar to that of Figure 5 but in an electric circuit-making position of the contacts of the device.
Figure 8.- Figure 8A is a cross-section view of the device taken approximately through the mid plane of a fixed contact, and in the electric circuit-making position; Figure 8B is a cross-section view of the device where the location of the arc quenching chambers with respect to the contacts can be seen; Figure 8C is another cross-section view where the location of the magnets with respect to the contacts by means of positioning parts is seen.
Figure 9 shows two plan views of the inside of the lower casing and a plan view of the upper casing, where the pair of fixed contacts has been removed from the left pole to better illustrate the vertically aligned or overlapping position of the magnets with respect to the fixed contacts. Figure 9A shows the contacts in an open position, where the arrow indicates the direction of movement for closing the slide; and Figures 9B and 9C show the contacts in a closed position, where the arrow indicates the direction of movement for opening the slide.
Figure 10 shows two perspective views of the switch device provide with side ventilation openings. Figure (a) depicts the device with its two casings coupled together, whereas Figure (b) only depicts the lower casing.
Preferred Embodiment of the Invention
[0023] Figure 1 shows an outer view of an embodiment of a 4-pole or phase switch disconnector device which is made up of a casing (7) formed by a top cover (1 a) and a bottom cover (1b) made of insulating material, coupled to one another.
[0024] The electrical connection contacts for connecting the device to an external circuit emerge from the casing (7). Each pole of the device is formed by a fixed contact of a first group of fixed contacts (2, 3, 4 and 5), a second fixed contact of a second group of fixed contacts (2', 3', 4', and 5'), and a moving contact (2", 3", 4", and 5") which can move between an electric circuit-breaking position in which it is not contacting the fixed contacts (corresponding to the position depicted in Figure 2a) and therefore makes current circulation impossible, and an electric-circuit making position in which it electrically connects the two fixed contacts with which it is associated (corresponding to the position depicted in Figure 4A) providing electrical continuity.
[0025] The moving contacts (2", 3", 4", and 5") are assembled equidistantly in a shuttle or slide (6) made of insulating material such that the moving contacts move simultaneously and together with said slide (6).
[0026] At least part of the fixed contacts and the slide (6) having the moving contacts are housed inside the casing (7) such that the pair of fixed contacts of one and the same pole are facing one another.
[0027] The slide (6) can be moved linearly inside the casing between two end positions defined by the internal shape of the casing itself, and is assembled in the central space between the two said groups of fixed contacts such that it moves transversely with respect to them. The top cover (1a) has an opening through which an external control (not depicted) is attached with the slide (6) to drive it manually. Alternatively, the slide can, for example, be moved by means of an automatically operated device.
[0028] The fixed contacts are internally assembled in one of the portions of the casing, for example, in the bottom cover (1 a) by means of screws (8). The moving contacts (2", 3", 4", and 5") are in turn knife-type contacts, i.e., they are made up of two pairs of overlapping flat bars (9,9') forming a space therebetween sized for tightly receiving a fixed contact, such that each moving contact contacts the corresponding fixed contact from the top and the bottom, as seen particularly in the drawings of Figure 8. These moving contacts (2", 3", 4", and 5") are dual contacts, since each of them is made up of two pairs of electrically connected flat bars (9,9'), where each pair is arranged on one side of the slide to contact a fixed contact of one and the same pole or phase.
[0029] Based on this already known structure of a switch disconnector device, one of the features defining the present invention comprises the application of a constant magnetic field in the electric circuit-breaking area between the fixed contacts and the moving contacts. To obtain that magnetic field, there is arranged at least one permanent magnet (10) as shown in Figure 3A, suitably positioned so that the magnetic field generated by the magnet interferes with the electric arc generated between the fixed contact (2) and the moving contacts (9,9'), lengthening the arc due to the magnetic blowout effect and, therefore, more quickly and effectively quenching the arc.
[0030] One pair of magnets per breaking point is preferably arranged, but the invention also includes the possibility of positioning a single magnet per breaking point, such that the magnetic field is not complemented by another magnet located opposite. This embodiment is preferred depending on the conditions of the electric circuit and the corresponding considerations of maximum electric circuit-making and breaking power, as well as the desired electrical contact durability.
[0031] Figures 3B and 3C show a pair of permanent magnets (10, 10') placed facing one another, i.e., with their axes aligned as indicated by the permanent magnetic field line (A). Furthermore, the magnets (10, 10') are spaced and positioned such that the moving contacts (9,9') and the fixed contact (2) are placed between the two magnets (10, 10') in an electric circuit-making position, i.e., when they are overlapping one another as shown in Figure 3C. The lines of force of the permanent magnetic field (A) cross the fixed and moving contacts in a manner substantially orthogonal to their surfaces, or in other words, perpendicular to the relative plane of movement (B) or plane of contact between the moving contacts (9, 9') and the fixed contact (2), such that the magnetic field generated interferes with or crosses the arc formed between the corresponding fixed and moving contacts.
[0032] The direction of the lengthening of the arc depends on the direction of circulation of the current in the electric arc and on the polarity of the magnets. Nevertheless, the side to which it is led is not important since the desired lengthening effect is obtained in any situation.
[0033] According to the embodiment schematically depicted in Figure 3, the set of magnets is positioned approximately centered with respect to the mid plane (B) of the fixed contact which it influences, therefore the area of the magnetic field generated having the greatest influence is around the mid plane (B) passing through the fixed contact.
[0034] There is a set of magnets for each breaking point the polarity of which is defined so that the magnetic field is reinforced regardless of the chosen orientation. The position of the magnets with respect to their polarity is chosen depending on the intended application and on the requirements of the switch/disconnector version, in terms of size, amperage, wiring, etc., and can therefore vary in each switch, the polarities: "North/North" - "North/South" - "South/North" - "South/South" being able to be provided for each pair of permanent magnets (10, 10').
[0035] The neutral plane of each set of magnets is preferably parallel to the plane of movement (B) of the contacts, the field lines thus traverse the contacts in the most favorable direction with respect to the blowout effect.
[0036] At least one magnet is preferably arranged per fixed contact, be it centered with respect to same or off-centered as will be described below.
[0037] In the preferred embodiment of Figure 2, one pair of magnets is arranged per fixed contact of the device, therefore since there are four poles or phases with two fixed contacts each, eight pairs of permanent magnets are arranged. Figure 2A shows how these magnets (10, 10') are located in a centered or overlapping manner, i.e., vertically aligned with respect to the fixed contact with which they are associated to aid in arc quenching.
[0038] The distance and position between magnets of the same pair is chosen so that the effect of the magnetic field that they generate is optimally complemented for arc quenching.
[0039] Specifically, the plan view of Figure 2A shows how each of the magnets (10'), i.e., the magnets coupled in the bottom cover (1b), are vertically aligned on the inner end of the fixed contacts (2-5),(2'-5') intended for contacting the corresponding moving contact (2"- 5"). Even though the outline of the magnets has been highlighted in Figure 2A in order to better see their position, these lower magnets (10') are in reality located behind the fixed contacts.
[0040] On the other hand, as seen in Figure 1, the upper magnets (10) complementing the pairs of permanent magnets when the two covers are coupled are arranged in a similar position in the top cover (1a) such that the two magnets (10, 10') and the corresponding fixed contact are aligned in a vertical axis.
[0041] In a preferred embodiment of the invention, the magnets are assembled inside the casing by means of positioning parts made of non-conductive material. In the case of Figure 2, the upper magnets (10') are coupled to the bottom cover (1b) through positioning parts (11'), whereas Figure 2B shows upper positioning parts (11), providing each magnet (10) with one of these parts (11), such that these parts (11) are configured for receiving a magnet and for coupling to an inner surface of one of the covers.
[0042] The effect or advantage of those positioning parts (11, 11') is that they keep the sets of magnets as close as possible to the electrical contacts, thus maximizing the influence exerted by the magnetic field generated on the electric arc. Furthermore, those positioning parts (11, 11') housing the sets of magnets assure that the correct positioning of the magnets can be reproduced during the manufacturing process, i.e., they assure the correct position of the magnets at all times regardless of the action of the assembly operator.
[0043] The positioning parts (11, 11') are parts which are independent from one another, they are not structural parts nor do they form part of the body of the apparatus and do not have an insulating function, such that they can be used independently increasing the flexibility in different apparatus configurations.
[0044] Alternatively, the permanent magnets (10,10') can be directly assembled on the inner surface of the corresponding cover, for which purpose that inner surface can be configured for receiving the corresponding magnets in a fixed position.
[0045] Figure 4 shows the same preferred embodiment of Figure 2, but in the electric circuit-making position of the device, corresponding to the situation of the contacts shown in Figure 3C.
[0046] In other embodiments of the invention, the permanent magnets do not overlap one another in correspondence with the vertical axis of the fixed contacts, rather they can be moved by a certain distance with respect to said vertical. This is the case of the embodiment depicted in Figures 5 and 6, where each pair of associated magnets (10, 10') are still facing one another (the axes of the two magnets (10, 10') are aligned according to the magnetic field line (A)), but each pair of magnets are slightly moved with respect to the position of the fixed contact (2) as seen in Figures 6A and 6B, such that the set of magnets is positioned outside the vertical axis (C) passing through the corresponding fixed contact (2).
[0047] It is interesting to highlight that the movement of the position of the magnets with respect to the vertical axis (C) is such that the magnets are closer to the area of movement of the moving contacts (9,9'), in the case of Figure 6A, to the right, therefore the area of the field having the maximum influence is slightly in front with respect to the arc-over area in the fixed contact.
[0048] By locating the magnets closer to the position of the moving contacts, the area of the magnetic field having the maximum influence on the arc is modified, which is advantageous for some specific requirements of the switch. For example, for less demanding requirements (lower electric currents) it is easier to quench the arc at its start, in which case it is recommendable to arrange the magnets centered with respect to the electrical contacts as shown, for example, in Figure 3. For more demanding requirements (higher electric currents), the blowout of the arc in the central area, i.e., off-centered with respect to the fixed contacts as shown, for example, in Figure 6, allows directing the arc to the arc quenching chambers more easily to divide the arc with greater ease when the device is used for breaking high currents.
[0049] The two plan views of Figure 7 clearly show the position of the permanent magnets (10, 10') slightly moved with respect to the position of the corresponding fixed contacts, i.e., with respect to the fixed contacts with which they are associated for quenching the arc, therefore these fixed contacts do not overlap the magnets completely. The movement of the magnets with respect to the vertical axis of the fixed contact is such that in the circuit-making position of the device shown in Figure 5, when the slide is moved in its right end position, the magnets (10, 10') are located between the fixed contacts and the moving contacts of the slide.
[0050] This Figure 7 also shows how each permanent magnet (10, 10') is assembled in a positioning part (11, 11') which is in turn fixed to the inner face of the top or bottom cover.
[0051] Figure 8A shows the position of the magnets with respect to the fixed contacts and moving contacts in the electric circuit-making position of the device when the magnets are aligned with the fixed contacts.
[0052] Complementary to the magnets, arc quenching chambers can be provided in the breaking points. Figure 8B shows the position of these arc quenching chambers (12) located in correspondence with the fixed contacts. These arc quenching chambers (12) can be used together with magnets centered with respect to the fixed contacts such as those of Figure 2 or 4, or with moved magnets such as those of Figure 5 or 7, resulting in different device configurations or versions.
[0053] Figure 9 shows a group of deionizing plates (13) located adjacent to the position of the magnets to aid in arc quenching.
[0054] For specific applications and requirements of the device, the invention has envisaged the incorporation of ventilation openings (14) communicating the inside of the device with the exterior to allow the exit of gases. These openings make preventing the damage of internal contacts possible in more demanding requirements in terms of the current breaking capacity, the high pressure and temperature of gases generated inside the device. These openings facilitate the release of gases to the exterior, whereby prolonging the service life of the contacts and eliminating the risk of explosion due to the high pressure that can be reached by the gases inside the device.
[0055] The casing of the switch device is rectangular and the fixed contacts (2-5), (2'- 5') are arranged on and protrude from the side faces of the casing. As seen in Figure 10, the ventilation openings (14) are housed on the side faces of the front and rear ends of the device, i.e., on the two side faces of the casing not having fixed contacts. The advantage of that location of the openings is that the gases are prevented from escaping through the upper face in which the operating control is located, thus eliminating the risk of impact on parts of the operator's body (hand/face) when he performs the breaking operation. With that arrangement of the openings on the side faces, the gases escape from the sides, and it further allows a more indirect and less abrupt gas release.
[0056] An additional advantage of that arrangement of the openings (14) is that the bagging-off of ionized gases of different polarities between the external contacts which could cause short circuits in the outer part of the contacts is prevented.
[0057] The number of ventilation openings (14) and their size are conveniently chosen depending on the requirements of each model of the switch. In terms of the shape of those openings, it has been found to be particularly advantageous to provide these openings (14) with a triangular shape, as depicted in Figure 10.
1. Electric switch and/or circuit breaker device comprising at least two connectable
electrical contacts which can be connected between an electric circuit-breaking position
and an electric circuit-making position wherein the two contacts are connected providing
electrical continuity, characterized in that it incorporates at least one permanent magnet arranged in the device such that at
least part of the magnetic field generated by said permanent magnet passes through
the electric arcing space between said contacts to interfere with said arc leading
to its quenching.
2. Device according to claim 1, comprising at least one pair of permanent magnets arranged
facing one another and such that there is established therebetween a magnetic field
passing through the electric arcing space between said contacts.
3. Device according to claim 1 or 2, wherein said connectable electrical contacts are
configured such that they can move in relation to one another on a plane of movement
to perform the electric circuit-breaking and electric circuit-making operations of
the device, and wherein said at least one permanent magnet is positioned such that
at least part of the lines of force of the magnetic field generated are substantially
orthogonal to said relative plane of movement between electrical contacts.
4. Device according to any of the preceding claims including at least one pole or electric
circuit-breaking phase formed by a first and a second stationary flat contact and
a movable flat contact, such that the moving contact can be moved on a plane of movement
between an electric circuit-breaking position and an electric circuit-making position
in which the moving contact electrically connects said first and second contacts and
in that there is arranged a first pair of magnets to quench the arc in the breaking
space of the first fixed contact and a second pair of magnets to quench the arc in
the breaking space of the second fixed contact.
5. Device according to any of the preceding claims, wherein the permanent magnets of
a pair of magnets overlap the fixed contact with which they are associated for arc
quenching in a manner such that a vertical axis passes through said magnets and fixed
contact.
6. Device according to any of claims 1 to 4, wherein the permanent magnets of a pair
of magnets are moved with respect to the fixed contact with which they are associated
for arc quenching in a manner such that a vertical axis passing through said magnets
is parallel to the vertical axis passing through the fixed contact.
7. Device according to claim 6, wherein the permanent magnets of a pair of magnets are
displaced towards the position furthest away from the moving contact with respect
to the fixed contact of the same pole.
8. Device according to any of the preceding claims, comprising at least one positioning
part made of non-conductive material configured for receiving a permanent magnet and
for maintaining it in a fixed position with respect to the fixed contact with which
it is associated.
9. Device according to any of the preceding claims, comprising a casing made of electrically
insulating material which houses, at least partially, the fixed contacts and the moving
contacts and wherein the permanent magnets are fixed on the inner surfaces of said
casing.
10. Device according to claims 8 and 9, wherein the permanent magnets are fixed on inner
surfaces of said casing by means of said positioning parts.
11. Device according to any of claims 1 to 10, wherein each pair of magnets is approximately
centered with respect to the mid plane of the fixed contact with which it is associated.
12. Device according to any of claims 9 to 11, wherein the casing is rectangular and the
fixed contacts are arranged on and protrude from opposing side faces of the casing
and the casing incorporates ventilation openings located in the other two side faces
of the front and rear ends of the casing.
13. Method for breaking an electric current by means of an electric switch and/or circuit
breaker which comprises applying a permanent magnetic field in the electric arcing
space in the electric circuit-breaking area such that said magnetic field interferes
with said arc and leads to its quenching.