Low voltage electrical contact system with enhanced arc blow effect

Abstract

Electrical contact system with a first and a second contact (1, 5), each having a contact surface (4, 8). The first electric contact (1) has a mesostructured electric contact portion (14) with a plurality of slots (15) and ridges (16) formed between neighboring slots (16) of the plurality of slots (16). These slots (15) and ridges (16) extend in a direction running transversely to said switching plane (X-Z) form a plurality of current paths (16). The current paths (16) are inclined to the first contact surface (4) at a first angle (17) measuring less than 60 degrees such that an interruption current (12) flowing through the mesostructured electric contact portion (14) and through an electric arc (11) extending in between the first contact surface (4) after lifting the first contact surface (4) off the second contact surface (8) pushes said electric arc (11) in the direction of the apex of said first angle (17) from a first position (18) to a second position (19).

Claims

1. An electrical contact system comprising a first electric contact with a first contact surface, a second electric contact with a second contact surface, and a set of splitter plates, wherein the first electric contact and the second electric contact are movable relative to one another along a switching path extending in a switching plane (X-Z) such that the first contact surface and the second contact surface touch each other in a closed state of the electrical contact system, and wherein the first contact surface is displaced by an insulating distance to the second contact surface in an open state of the electrical contact system, and wherein the first contact surface and the second contact surface extend transversely to said switching plane (X-Z), wherein at least one of the first electric contact and the second electric contact comprises a structured electric contact portion with a plurality of slots and ridges formed between neighboring slots of the plurality of slots, wherein the plurality of slots and ridges extend in a direction running transversely to said switching plane (X-Z) form a plurality of current paths leading through the structured electric contact portion, and wherein the plurality of current paths is inclined to the first contact surface and the second contact surface, respectively, at a first angle measuring less than 60 degrees such that an interruption current flowing through the structured electric contact portion and through an electric arc extending in between the first contact surface and the second contact surface, respectively, after lifting the first contact surface off the second contact surface pushes said electric arc in the direction of the splitter plates and off the first and second electric contacts.

2. The electrical contact system according to claim 1, wherein the first angle is less than 45 degrees.

3. The electrical contact system according to claim 1, wherein the plurality of current paths extends parallel to one another in the at least one of a first electric contact and the second electric contact.

4. The electrical contact system according to claim 1, wherein the plurality of slots has a strip-shaped cross section extending in the switching plane (X-Z) each, wherein a major axis of that strip-shaped cross section each extends in a direction of the current paths, an average slot width extending in the switching plane along a minor axis of the cross-section and running perpendicularly to the major axis is in a range of 50 micrometers to 0.5 millimeters.

5. The electrical contact system according to claim 4, wherein an aspect ratio of a slot length extending in the direction of the major axis to a slot width extending in the direction of the minor axis is at least 4:1.

6. The electrical contact system according to claim 1, wherein an overall slot-to-ridge ratio along at least one of the first contact surface and the second contact surface, respectively, in the switching plane (X-Z) is in a range of 30% to 70%.

7. The electrical contact system according to claim 1, wherein a minimal spacing of two neighboring slots in the direction of the first contact surface in the switching plane (X-Z) is at least one third of a calculated arc impact area diameter, wherein the arc impact area diameter extends in the first contact surface and delimits a region of the first contact where the electric arc melts the first contact surface in an operating state of the electric contact system.

8. The electrical contact system according to claim 1, wherein the plurality of slots extending in the switching plane (X-Z) such that their proximal ends pointing towards the at least one of the first contact surface and the second contact surface, respectively, are located at a distance under the first contact surface and the second contact surface, respectively, such that an arcing contact layer is formed.

9. The electrical contact system according to claim 8, wherein the arcing contact layer has a thickness of about 50 micrometers to 2 millimeters.

10. The electrical contact system according to claim 1, wherein at least one of the first electric contact and the second electric contact comprises a contact piece that is mechanically and electrically connected to a contact carrier, wherein said contact piece is designed to act as arcing contact layer, and wherein the structured electric contact portion is provided in one of a) the contact piece of the at least one of the first electric contact and the second electric contact, b) the contact carrier connected to the at least one of the first electric contact and the second electric contact, c) both of a) and b), wherein the contact piece and the contact carrier are arranged relative to one another such that the current paths of the contact piece continue in the current paths of the carrier.

11. The electrical contact system according to claim 1, wherein the first electric contact as well as the second electric contact have a structured electric contact portion each, wherein the slots of the structured electric contact portion in the second electric contact are oriented such that an angle leg of first angle intersects with an angle leg of first angle of the structured electric contact portion in the second electric contact in an area of the switching plane (X-Z) located between the first contact surface and the second contact surface.

12. The electrical contact system according to claim 1, wherein at least one of the first electric contact and the second electric contact comprises a notch arranged proximate to the structured electric contact portion, wherein said notch is designed and arranged such that the interruption current is guided towards the current paths.

13. The electrical contact system according to claim 1, wherein at least some slots of the plurality of slots are filled with a filler material having electrical conducting or electrical insulating properties being lower than the electrical conducting of the ridges.

14. The electrical contact system according to claim 13, wherein the filler material comprises at least one element of the group comprising a) polymer material, b) tungsten material, c) a material that releases a carbonaceous gas when exposed to the electric arc, d) metal oxide.

15. A low or medium voltage switchgear, comprising an electrical contact system according to claim 1.

16. The electrical contact system according to claim 2, wherein a minimal spacing of two neighboring slots in the direction of the first contact surface in the switching plane (X-Z) is at least one third of a calculated arc impact area diameter, wherein the arc impact area diameter extends in the first contact surface and delimits a region of the first contact where the electric arc melts the first contact surface in an operating state of the electric contact system.

17. The electrical contact system according to claim 2, wherein the plurality of current paths extends parallel to one another in the at least one of a first electric contact and the second electric contact.

18. The electrical contact system according to claim 2, wherein the plurality of slots has a strip-shaped cross section extending in the switching plane (X-Z) each, wherein a major axis of that strip-shaped cross section each extends in a direction of the current paths, an average slot width extending in the switching plane along a minor axis of the cross-section and running perpendicularly to the major axis is in a range of 50 micrometers to 0.5 millimeters.

19. The electrical contact system according to claim 18, wherein an aspect ratio of a slot length extending in the direction of the major axis to a slot width extending in the direction of the minor axis is at least 4:1.

20. The electrical contact system according to claim 2, wherein the plurality of slots extending in the switching plane (X-Z) such that their proximal ends pointing towards the at least one of the first contact surface and the second contact surface, respectively, are located at a distance under the first contact surface and the second contact surface, respectively, such that an arcing contact layer is formed.

21. The electrical contact system according to claim 1, wherein the structured electric contact portion is a porous compound material.

22. The electrical contact system according to claim 1, wherein the ridges of the structured electric contact portion have dimensions between 50 micrometers and 2 millimeters.

23. An air-insulated switchgear comprising the electrical contact system according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The description makes reference to the annexed drawings, which are schematically showing in

(2) FIG. 1 a side view of a conventional electrical contact system;

(3) FIG. 2 a side view of a first embodiment of an electrical contact system according to the present invention;

(4) FIG. 3 a side view of a second embodiment of an electrical contact system according to the present invention;

(5) FIG. 4 a top view on the lower electric contact along plane II-II of FIG. 3;

(6) FIG. 5 a top view on the lower electric contact of a third embodiment along plane II-II of FIG. 3;

(7) FIG. 6 a bottom view on the upper electric contact of the third embodiment shown in combination with FIG. 5;

(8) FIG. 7 a side view of the second embodiment of FIG. 3;

(9) FIG. 8 a side view of a fourth embodiment of an electrical contact system according to the present invention;

(10) FIG. 9 a side view of a fifth embodiment of an electrical contact system according to the present invention;

(11) FIG. 10 a side view of a sixth embodiment of an electrical contact system according to the present invention; and

(12) FIG. 11 a side view of a seventh embodiment of an electrical contact system according to the present invention.

(13) In the drawings identical or at least functionally identical elements and currents are given identical reference characters.

WAYS OF WORKING THE INVENTION

(14) A side view of a side view of a first embodiment of an electrical contact system 10 according to the present invention is shown in FIG. 2. In fact the side view is a cross-section of the electrical contact system whereas any cross-hatching has been omitted for the sake of better visibility and enhanced clarity. That electrical contact system 10 comprises a first electric contact 1 shown as an upper contact as well as a second electric contact 3 shown as a lower contact in an open state of the electrical contact system. The first electric contact and the second electric contact are made form a copper alloy. In contrast to the electrical contact system of FIG. 1, there is no contact piece such that the first contact surface 4 is provided directly at the end region of the first electric contact 1. The second contact surface 8 is provided directly at the end region of the second electric contact 5. The first electric contact 1 and of the second electric contact 5 are movable relative to one another along a switching path extending in a switching plane X-Z. The switching path can be linear or arcuate.

(15) The first contact surface 4 and the second contact surface 8 touch each other in a closed state of the electrical contact system. The first contact surface 4 is displaced by an insulating distance 9 to the second contact surface 8 in an open state of the electrical contact system such that the desired interruption and safe electric insulation between the first and second contact is achieved. The first contact surface 4 and the second contact surface 8 extend transversely, i.e. perpendicularly to said switching plane X-Z in the direction of virtual plane X-Z. Once this electrical contact system is opened, an electric arc 11 evolves between the first contact surface 4 and the second contact surface 8. Since the current path of the nominal as well as of the interruption current path 12 lead through the first electric contact 1 and the second electric contact 5 in a loop when seen in plane X-Z, the natural magnetic field of the interruption current 12 pushes the electric arc 11 from the left to the right.

(16) The first electric contact 1 comprises a mesostructured electric contact portion 14 with a plurality of slots 15 and ridges 16 formed between neighboring slots of the plurality of slots 15. The plurality of slots 15 and ridges 16 extend in a direction running transversely/perpendicularly to the switching plane X-Z and form a plurality of current paths 12 leading through the ridges 16 of the mesostructured electric contact portion 14. The current paths 16 are inclined to the first contact surface at a first angle 17 measuring less than 60 degrees such that an interruption current flowing through the mesostructured electric contact portion 14 and through an electric arc 11 extending in between the first contact surface 4 and the second contact surface 8 after lifting the first contact surface 4 off the second contact surface 8 pushes said electric arc 11 in the direction of the apex of said first angle 17 from a first position 18 (here located at the left) to a second position (here located at the tip end of the first electric contact 1).

(17) The inclined current paths 16 (of which only a single current path of the plurality of current paths is shown in FIG. 2 for the sake of clarity) guide and direct the interruption current 12 such that compared to the conventional set up shown in FIG. 1 the current is prevented or at least substantively hampered from leaving the first contact surface 4 in a perpendicular direction relative to the first contact surface 4. As a result, the force 13 acting on the electric arc 11 is bigger in the embodiment according to FIG. 2 than in the embodiment according to FIG. 1. Some quantification of the force difference has been made in that the arrow of force 13 is illustrated bigger than in FIG. 1.

(18) The slots 15 have been cut into the first electric contact 1 by way of laser-cutting at a first angle of about 45? such that the plurality of current paths extends parallel to one another. The slots have a strip-shaped cross section extending in the switching plane X-Z each, wherein a major axis 21 of that strip-shaped cross section each extends in a direction of the current paths 16, i.e. the ridges 16. The average slot width 34 extending in the switching plane along a minor axis 22 of the cross-section and running perpendicularly to the major axis 21 is about 0.3 millimeters for use in a low voltage switchgear.

(19) An aspect ratio of a slot length 35 extending in the direction of the major axis 21 to a slot width 34 extending in the direction of the minor axis 22 is about 5:1. An overall slot-to-ridge ratio along at least one of the first contact surface 4 (say along line III-III in FIG. 2 in the slotted area only) is about 40% to 60%.

(20) Next, a side view of a second embodiment of an electrical contact system 20 according to the present invention is described with reference to FIG. 3 and FIG. 4 and FIG. 7. Hereinafter, only differences in effect and elements compared to the first embodiment 10 shall be addressed.

(21) In this embodiment 20, the second electric contact 5 is shaped exactly the same way as the first electric contact 1. Hence, the slots 15 of the mesostructured electric contact portion 14 in the second electric contact 5 are oriented such that an angle leg of first angle 17 intersects with an angle leg of first angle 17 of the mesostructured electric contact portion 14 in the second electric contact 5 in an area of the switching plane X-Z located between the first contact surface 4 and the second contact surface 8 at an intersection angle 23 of about 90?.

(22) In FIG. 3, the electric arc 11 is shown more realistic than in FIG. 1 as an arc column (indicated in a dotted pattern) extending between the first contact surface 3 and the second contact surface 8. The column to the left represents the first position 18 of the electric arc 11 after ignition whereas the column to the right represents the second position 19 of the electric arc 11 shortly before extinction. Note, that although the electric arc 11 is shown both in the first position 18 and in the second position 19 in FIG. 3, it will not be at both positions at the same moment in time in real life of the switchgear. The arc travel direction is indicated by arrow 24. Again, the interruption current 12 is indicated only in a representative location for displaying its new shape compared to FIG. 2 embodiment 10.

(23) FIG. 4 reveals that a minimal spacing of two neighboring slots 15 in the direction of the first contact surface 4 and the second contact surface 8 in the switching plane X-Z is at least one third of a calculated arc impact area diameter 25 such that the arc 11 can start always from at least two ridges 16.

(24) As shown in figure, the desired force 13 on the electric arc is bigger than in the first embodiment 10.

(25) A third embodiment 30 to the embodiment 20 shown in FIG. 3 is shown and explained with respect of FIG. 5 and FIG. 6. The only modification relies in that the slots 15 are not only inclined about the first angle 17 but also about a second angle 26 in case of the lower electric contact seen along plane II-II as shown in of FIG. 3. Likewise, the slots 15 are not only inclined about the first angle 17 but also about a third angle 26 in case of the upper electric contact seen along plane I-I as shown in of FIG. 3. The provision of the second angle 26 and the third angle 27 are advantageous as their contribute to a smoother continuous, i.e. a less staggered travel of the electric arc 11 in the arc travel direction 24 compared to the second embodiment 20.

(26) A fourth embodiment 40 of the electrical contact system is shown and explained with respect of FIG. 8. The only modification compared to the third embodiment resides in that relies in that the first electric contact 1 comprises a first contact piece 3 that is mechanically and electrically connected to a contact carrier 28 of the first electric contact 1. The contact carrier 28 has essentially the same function as the first contact carrier 2 and the second contact carrier 6. Said contact piece 3 comprises the first contact surface 4 and is thus designed to act as arcing contact layer for the electric arc 11. The arcing contact layer formed by said contact piece 3 has a thickness of about 0.5 mm for use in a low voltage switchgear.

(27) The fifth embodiment 50 of the electrical contact system shown and explained with respect of FIG. 9 differs to the fourth embodiment 40 in that a second contact piece 7 that is mechanically and electrically connected to a contact carrier 28 of the second electric contact 5 the same way as in the first electric contact 1.

(28) The sixth embodiment 60 of the electrical contact system shown and explained with respect of FIG. 10 differs to the fifth embodiment 50 in that all slots 15 are filled with a filler material 29 comprising Aluminum oxide for enhancing the overall mechanical stability and durability of the mesostructured electrical contact portion 14.

(29) The seventh embodiment shown and explained with respect to FIG. 11 has a first electric contact 1 that is formed differently than the second electric contact 5. Compared to the fifth embodiment 50 the first electric contact 1 comprises a notch 31 arranged proximate to the mesostructured electric contact portion 14. Said notch 31 is designed and arranged such that the interruption current 12 is guided towards the current paths extending in between the ridges 16. Moreover, the first contact piece 3 is formed such that is has a mesostructured electric contact portion 14 as well. The first angle of both about 45? but the slots 15 and ridges 16 in the first contact piece 3 are thinner than in the contact carrier 28. In addition extend the slots 15 in the first contact piece 3 not to the first contact surface 4. In the contrary, the plurality of these slots 15 extend in the switching plane X-Z only such that their proximal ends pointing towards the first contact surface 4 are located at a distance 32 under the first contact surface 4 and such that an arcing contact layer 33 (shown in dotted lines in FIG. 11) is formed. In FIG. 11, the arcing layer has a thickness that is comparatively small in the Z-direction, i.e. about 0.4 mm.

(30) Compared to the first embodiment 10 shown in FIG. 1 and the fifth embodiment 50 shown in FIG. 9, the second contact piece 7 shown as lower contact of the seventh embodiment 70 has a second contact piece 7 that is mechanically and electrically connected to its contact carrier 28. The second contact piece 7 has the very same geometry as the first contact piece 3 but is mounted in a mirrored fashion compared to the first contact piece 3 such that the first angles of the first electric contact 1 and of the second electric contact 5 intersect at an intersection angle as described earlier on.

(31) The seventh embodiment 70 is purely schematically and shows a possible variation to profit from the present invention. Where required, further embodiments of the electrical contact system can comprise a second electric contact that is formed the same way as the first electric contact above. Likewise it is possible to form the first contact the same way as the second electric contact above.

(32) The skilled reader will recognize that a plurality of combinations of any first electric contacts and second electric contacts disclosed in this description and the figures is achievable such that one will arrive at the desired effect of the magnetic pressure on the electric arc.

LIST OF REFERENCE NUMERALS

(33) 1 first electric contact 2 first contact carrier 3 first contact piece 4 first contact surface 5 second electric contact 6 second contact carrier 7 second contact piece 8 second contact surface 9 insulating distance; isolating distance; insulating gap 10, 20, 30, 40, 50, 60, 70 electrical contact system 11 electric arc 12 interruption current; 13 pressure/force acting on the electric arc 14 mesostructured electric contact portion 15 slot 16 ridge; current path 17 first angle 18 first position of the arc 19 second position of the arc 21 major axis 22 minor axis 23 intersection angle 24 arc travel direction 25 arc impact area diameter 26 second angle 27 third angle 28 contact carrier 29 filler material 31 notch 32 distance 33 arcing contact layer 34 slot width 35 slot length