EP0203367B1 - Contact arrangement for a vacuum system - Google Patents

Description

The invention relates to a contact arrangement for vacuum switches, with two contacts arranged coaxially opposite one another and displaceable in their axial direction relative to one another, each consisting of a disk-shaped contact piece with a contact surface and a disk located therebetween, made of electrically highly conductive material, which disks each are directly connected to a central power supply bolt and, due to their shape with circular recesses and slots, implement radial and azimuthal current conductors and thereby means for generating axial magnetic fields, the current from the power supply bolt via the current conductors of the disk and from there via the slots limited laterally Webs is led to the contact piece.

Vacuum switches are becoming increasingly important for high breaking currents. At high switching currents, however, the following problem arises: As a result of the intrinsic magnetic field of the busbar connections and the contact shape, high forces occur against the arc plasma, which push the plasma out of the contact gap to the switching chamber wall and shift the arc attachment points to the outer switching contact circumference, where they can burn there. This fact has the consequence that after-heating or thermal emission as well as thermal emission can cause the arc to re-ignite after the zero crossing of the sinusoidal alternating current due to thermal overloading of the contact surfaces concerned, as a result of which the current can no longer be safely extinguished or switched off . Likewise, a strong local melting of the contact piece is associated with high burn-up losses.

Contact forms have been proposed which generate magnetic fields in the vicinity of the switch contact surface by means of special shaping or current conduction. For example, radial magnetic fields can exert a force on the arc and cause the arc to move rapidly on the contact surface. At the same time, at currents above approximately 20 kA, the arc plasma can be pressed out of the contact gap, which is why axial magnetic fields are advantageous at these high currents.

The parameters of the axial magnetic field are essentially dependent on the design of the associated coil former. Known forms of contact for self-generating axial magnetic fields are usually composed of arc-shaped or hook-shaped coil elements.

For example, a contact arrangement is known from DE-C 2 443 141, in which each contact consists of a contact piece and a coil located behind it, the latter being formed with approximately spoke-shaped arms as first conductor sections and annular regions attached thereto as second conductor sections. The second conductor sections adjoin each other in the area of the greatest distance of the first conductor section from the central axis and run in the same direction on a circular arc that extends approximately parallel to the outer circumference of the one contact piece up to a gap-shaped distance to the respectively adjacent first line section and there in passes over a third conductor section.

In this known arrangement, the bobbins with the conductor sections are aligned with one another in both contacts. The production of the contacts with the associated coil elements is comparatively complex, such an arrangement being mechanically not very stable.

From DE-A 3 215 020 a contact arrangement is also known, in which behind the actual contact piece there are conductor sections in which partial currents are guided in the radial and circumferential directions to generate an axial magnetic field in the contact arrangement, the contacts being lined up in the circumferential direction contain cross-section-reducing recesses and the webs remaining between the recesses form radially extending conductor sections. In this case, the contacts of the same design are installed in a contact arrangement rotated about the longitudinal axis in such a way that in each case a recess in one contact faces a web of the other contact and covers it. This is intended to form contact areas between the cutouts and the periphery of the contacts, a gap leading to the contact edge of each cutout in order to delimit a conductor section in the circumferential direction. The overlapping gaps of the contacts are placed where the cutouts intersect in order to achieve a contact opening in the radial direction. Circular perforations, for example, can be provided as cutouts in this contact arrangement. The mutually facing contact surfaces of the two contacts must be provided with a contact material suitable for vacuum switches, for which purpose a thin disk or a layer of this material is to be applied to the arrangement described.

From the structural design of the contact arrangement according to DE-A 3 215 020 it can be seen that the axial magnetic field loses effectiveness during a switching operation, since the plasma formed in the contact gap can lead to a short circuit between the central, highly conductive current supply bolts.

From DE-A 3 338 254 a contact arrangement for vacuum switches with an axial magnetic field of the type mentioned is also known, in which there are recesses, which can be circular, for example, and slots which each have the recesses from one side to the circumference of the disk continue. For this purpose, the approximately radial slots are sawn from the outside in so that they meet the recesses which were previously drilled as holes. In a vacuum switch constructed in this way, the two contact pieces with the axial magnetic field generating conductors to be completely identical.

In contrast, the object of the invention is to improve the contact arrangement of the type mentioned in the introduction in such a way that it is even more effective than the previously known arrangements with regard to the generation of an axial magnetic field.

The object is achieved according to the invention in a contact arrangement of the type mentioned at the outset in that the slots run at an acute angle with the circumferential tangent from the outside diameter of the disk, tangentially to the circular recesses with the outside edge, and in that the contacts arranged opposite one another are oriented azimuthally in such a way that that the circular recesses of the two opposite disks are congruent in the axial direction, two adjacent tangential slots, however, only face each other on the outer diameter of the disks.

From DE-C 2 363 044 a two-area contact is known, with an outer high current area and an inner, outstanding area for guiding the nominal current or for switching off small switching currents, in which slots in the contact piece run tangentially from the outer circumference to the inner contact area expand circularly at their ends.

This contact arrangement is intended to achieve a radial magnetic field and thus tangential circulation of the arc.

In the invention it is advantageous that the radial and azimuthal conductor elements in the disks change their surface continuously and that there is an optimal cross-sectional change for the coil arms thus formed, which supports the course of the magnetic field in the desired manner. This means that the entire available area for the power line is optimally used. The fact that the adjacent slots face each other on the outer diameter of the disk minimizes the current path. This remains even when the contacts open and the axial magnetic field effective on the outer switching contact circumference is stable. The disc acting as a coil can be produced in a simple manner, for example as a cast part, stamped part or also as a stamped and stamped part.

Depending on the application, the radial and azimuthal current conductors of the disk forming the coil can consist of a different number of conductor elements. For example, for shutdown currents up to approx. 40 kA, at least three, preferably four, elements will be necessary. For switch-off currents above approx. 40 kA, gene preferably needs six or more elements. In the event that, for example, two circular cutouts are lined up directly in the disk, the individual radial and azimuthal current conductors can also consist of at least three, preferably four, elements for switch-off currents above approximately 40 kA.

The webs at the ends of the current conductors can have triangular or square bases. Such webs can be separate, non-cutting sheets made of electrically good conductive material; but they can also be directly molded from the disc. On the other side of the slot, a spacer made of poorly electrically conductive material can be arranged on the disc opposite the web in order to improve the mechanical stability.

A contact piece pad made of electrically highly conductive material can additionally be present between the disk and the actual contact piece. It is advantageous if the contact pieces and the optionally available contact piece supports have at least the same number of radial slots corresponding to the number of circular recesses in the disk, which serve to suppress eddy currents. However, these slots do not coincide with the slots in the coil former, but rather run over the edges of the webs facing away from the slots.

The actual contact piece is made in a known manner from a material based on copper and chrome: the contact piece is preferably rounded at the edges towards the button.

Further details and advantages of the invention result from the following description of figures of exemplary embodiments with reference to the drawing.

• FIG 1 einen Längsschnitt durch einen einzelnen Kontakt der Kontaktanordnung.
• FIG 2 eine Draufsicht auf den Spulenkörper der FIG 1 längs der Linie 11-11 in FIG 1.
• FIG 3 eine Draufsicht auf das Kontaktstück der FIG 1.
• FIG 4 eine perspektivische Darstellung einer Gesamtkontaktanordnung zur Erläuterung der erfindungsgemäßen azimutalen Orientierung beider Kontakte.

They each show a schematic representation

• 1 shows a longitudinal section through a single contact of the contact arrangement.
• 2 shows a plan view of the coil former of FIG. 1 along the line 11-11 in FIG. 1.
• 3 shows a plan view of the contact piece of FIG.
• 4 shows a perspective view of an overall contact arrangement to explain the azimuthal orientation of both contacts according to the invention.

FIGS. 5 to 8 representations corresponding to FIGS. 1 to 4 of a second exemplary embodiment and

9 shows the top view of the coil former of a third exemplary embodiment.

The first exemplary embodiment has a division into four and is designed for currents up to approximately 40 kA, with no contact piece support being present here. The second exemplary embodiment has a six division and is designed for currents above approximately 40 kA, a contact piece support being provided as an example in this embodiment. The third embodiment is also provided for cutoff currents above 40 kA.

In the figures, identical or equivalent parts are provided with the same reference numerals.

In FIG 1, 10 denotes a contact pin which carries two disks 20 and 40 lying one above the other. The upper disk 40 realizes the contact piece, which consists of a material based on copper and chromium (CuCr) and has strongly rounded edges 42 on the outer diameter. For better heat dissipation, the contact piece 40 can be soldered to a copper base, which will be discussed later. The CuCr disk 40 is soldered and electrically connected to the disk 20 underneath, which is designed as a coil for generating an axial magnetic field, via copper webs 50. Spacers 60 are present opposite the web 50. Furthermore, a metallic support body 70 made of electrically poorly conductive material is arranged between the contact pin 10, the coil disk 20 and the contact piece 40. This ensures that the current flow during the switch-off process predominantly flows over the radial and azimuthal current conductors provided for generating the magnetic field as coil arms.

The geometric design of the coil disk 20 is shown in detail in FIG 2. The circular disc 20 has a diameter of approximately 75 mm. Four identical, circular recesses 21, which are offset by 90 _° in each case and have a diameter of approximately 17.5 mm, are introduced on the circular surface approximately symmetrically in the radius center. Tangential slots 22 run from the periphery of the disk 20 to the recesses 21, an angle of less than 90 _° (acute angle) being formed in each case by the slot 22 and the tangent to the periphery of the disk 20. A further recess 23 is made centrally in the disk 20, the diameter of which is adapted to the support body.

By shaping the disk 20 in this way, four identical current conductors 24 are formed, each extending initially radially and then azimuthally starting from the circumference of the recess 23. The special arrangement of the cutouts 21 and the webs 22 means that the current conductors 24 have a continuously changing cross section over the entire area. In FIG. 2, the section end of the current conductors 24 delimited by the slots 22 is designated by 25. The webs 50 according to FIG. 1 are applied, for example soldered, to these approximately triangular regions 25. Spacers 60 according to FIG. 1 are introduced into corresponding recesses 26 on the other side of the slots, thereby ensuring adequate mechanical stability. By choosing the material of the spacers 60, poor electrical conductivity is taken care of.

It is clear from FIG. 3 that there are also slots 41 in the contact disk 40 lying above the coil disk 20. The number of slots 41 corresponds to the number of circular recesses 21 with tangential slots 22, the slots 41 of the contact disk 40 running through corresponding azimuthal orientation of the disks 20 and 40 relative to one another in such a way that they cover the web areas 25 on the slots 22 of the coil disk Limit 20 opposite side. In the described embodiment, there is an angle of 22.5 _° between the radius leading through the center of the recesses 21 and the slot line, which is indicated in FIG. 4 at contact A.

The described design of the coil disk 20 ensures that the current flows in each case with radial and azimuthal components from the contact pin 10 via the disk 20 and the webs 50 into the actual contact piece 40, so that an axial magnetic field component is generated. It has been shown that a high continuous current carrying capacity of the contact arrangement is ensured in the construction of the contacts shown. The formation of eddy currents in the contact pieces 40 is effectively prevented by the slots 41 located therein.

In order to effectively use the axial magnetic field components in a contact arrangement, a suitable azimuthal assignment of the two contacts is required. This becomes clear from the perspective illustration according to FIG. 4: A and B mean two contacts of identical construction according to FIGS. 1 to 3 described above, which are displaceable in the axial direction and can therefore establish or interrupt an electrical contact. The contacts are in turn made up of bolts 10a and b, the coil disk 20a and b, and the contact disk 40a and b, respectively. The contact pin 10a or b tapers here with its portion 11a or b to the disk 20a or b.

The two contacts A and B are oriented azimuthally in FIG. 4 in such a way that the respective circular recesses 21 in the disks 20a and b are congruent with one another in the axial direction, while the associated tangential slots 22 are only opposite one another on the outer diameter of the disks 20a and b. This inevitably means that the slots 41 a and 41 b in the contact pieces 40 of both contacts A and B each enclose an angle.

In FIGS. 5 to 8, the same reference numerals are used in principle as in FIGS. 1 to 4. 5 shows that here, in addition, a contact piece pad 30 is arranged between the coil disk 20 and the contact disk 40, which serves for heat dissipation. The disks 30 and 40 are soldered together.

In the embodiment according to FIG. 6, a larger disk with six sections is selected for higher currents. According to FIG. 2, six circular recesses 21 of approximately 20 mm in diameter are made on a disc 20 of approximately 100 mm in diameter on a circle which is concentric with the circumference and has half the disc diameter, and tangential slots 22 approach from the diameter of the circle. The slots 22 in turn form an acute angle with an amount of less than 90 _° with the tangent to the circumference of the disk 20. Concentrically around the center there is a further recess 23, which in this case is larger than the recesses 21. Such a configuration forms six current conductors 24, each with a radial and an azimuthal region, the surface of the current conductor again continuously changing over the entire region. Before the boundary by the web 22, an angular surface 25 is formed, on which the web 50 according to FIG. 5 is located. In contrast, the spacers 60 made of poorly conductive material are in turn present in order to ensure mechanical stability in recesses 26.

Furthermore, according to FIG. 7, there are slots 41 and 31 in the CrCu contact disk 40 and additionally in the contact piece support 30 present here, the disks 30 and 40 being oriented on the coil disk 20 in such a way that the slots 31 and 41 are each the one Limit slots 22 on the opposite side of the web area 25. In this embodiment, there is an angle of 15 _° between the radii leading through the center of the recesses 21 and the slot lines, which is indicated in FIG. 8 at contact A.

The azimuthal orientation of the contact arrangement with two contacts A and B, which are identical per se, results from FIG. 8. Shown are contact bolts 10a and b, coil disks 20a and b, contact piece support 30a and b, and contact piece 40a and b.

Because of the diameter of the contacts on the one hand and the size and number of recesses on the other hand, the contact arrangements described can be used for currents of different heights. The contact arrangement according to FIGS. 1 to 4 is suitable for currents up to approx. 40 kA and the contact arrangement according to FIGS. 5 to 8 is suitable for currents above approx. 40 kA. 9 shows that two circular cutouts 21 can also be arranged in groups in a coil disk 20. In total, only four total recesses are necessary with a high current carrying capacity. From one side of the cutouts, slots 22 are again brought into the cutouts 21 at an acute angle with the tangent to the circumference of the circle. The end region of the current conductors 24 for the webs 50 results here in an approximately trapezoidal shape with 25. Corresponding support bodies made of electrically poorly conductive material are provided in depressions 26. The overlying contact disk 40 or contact piece support 30 in turn has corresponding slots 31 and 41, which each delimit the other web side.

The azimuthal orientation of a contact arrangement with contacts according to FIG. 9 essentially results in accordance with FIG. 4.

The dimensions of the contacts with the contact piece 40 and the coil disk 20 behind it can be varied. In the case of the coil disk 20, the ratio of the overall diameter to the diameter of the circular recesses 21 is advantageously between 3: 1 and 6: 1. Tests have shown that with such a dimensioning an optimized axial magnetic field is achieved.

Claims (14)

1. Contact arrangement for a vacuum switch, with two contacts (A, B) arranged coaxially with respect to one another and displaceable relative to one another in their axial direction, said contacts each comprising a disc-shaped contact piece with a contact surface and spaced behind it a disc (20) made from a material that is a good electrical conductor, said discs (20a, 20b) each being directly connected to a central current supplying rod (10) and by virtue of being constructed with circular recesses (21 a, 21 b) and slots (22) producing radially and azimuthally extending current conductors and hence means for generating axial magnetic fields, the current passing from the current supplying rod (10) to the contact piece via the current conductors of the disc (20) and from there via lands laterally delimited by said slots (22), characterised in that the slots (22) run at an acute angle « 90_°) to the outermost tangent of the disc (20) and with their outer edges tangential to the circular recesses (21), and that the opposing contacts (A, B) are azimuthally orientated such that the circular recesses (21 a, 21 b) of the two opposing discs (20a, 20b) overlap one another in the axial direction, whereas two adjacent tangential slots (22) only oppose one another on the outer diameter of the discs (20a, 20b).

2. Contact arrangement according to claim 1, characterised in that for breaking currents up to approx. 40 kA the individual radially and azimuthally extending current conductors (26) consist of at least three, preferably four, elements.

3. Contact arrangement according to claim 1, characterised in that for breaking currents above approx. 40 kA the individual radially and azimuthally extending current conductors (24) consist of six or more elements.

4. Contact arrangement according to claim 1, characterised in that to produce the radially and azimuthally extending current conductors two or more circular recesses (21) are ranged alongside one another.

5. Contact arrangement according to claim 4, wherein specifically two circular recesses are ranged alongside one another, characterised in that for breaking currents above approx. 40 kA the individual radially and azimuthally extending current conductors (24) consist of at least three, preferably four, elements.

6. Contact arrangement according to claim 1, characterised in that the lands (50) located at the extremities (25) of the current conductors (24) have a triangular or square base.

7. Contact arrangement according to claim 6, characterised in that the lands (50) are thermoformed sheets of a material that is a good electrical conductor, e.g. copper, which are welded onto the disc (20).

8. Cotact arrangement according to claim 6, characterised in that the lands (50) are compression- moulded from the disc (20).

9. Contact arrangement according to any of the preceding claims, characterised in that on the disc (20) are azimuthally distributed spacers (60), which each lie opposite the lands (50) on the other side of the slots (22).

10. Contact arrangement according to any of the preceding claims, characterised in that the discs (20) having the recesses (21) and slots (22) are castings.

11. Contact arrangement according to claim 1, characterised in that between the disc (20) and the contact piece (40) is disposed a contact piece backing member (30) made from a material that is a good electrical conductor.

12. Contact arrangement according to any of the preceding claims, characterised in that the contact pieces (40a, 40b), and if applicable the contact pieces backing members (30a, 30b), have at least an equal number of radial slots (31, 41) for suppressing eddy currents, according to the number of circular recesses (21) in the disc (20).

13. Contact arrangement according to claim 12, characterised in that the radial slots (31, 41) in the contact piece (40), and if applicable the contact piece backing member (30), extend over the edges of the lands (50) that are remote from the slots (22).

14. Contact arrangement according to any of the preceding claims, characterised in that the contact piece (40) is rounded at the circumference and consists of a material based on copper and chromium (CuCr).

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