EP0082801B1 - Vacuum switch with a ring to create an axial magnetic field - Google Patents

Description

The invention relates to a vacuum interrupter with two relatively movable, arranged on carrier pins switching element arrangements of cylindrical disk-shaped form, each having a closed contact surface for the arc and a contact body arranged on the back of this contact body, on its circumference galvanically interrupted only once to produce a have axially directed magnetic field, the connection of each ring with the associated carrier bolt and the associated contact body taking place directly starting from the point of galvanic interruption of the ring.

A vacuum interrupter of this type is known from US-A-3 818 164. The ring is arranged between two disc-shaped bodies, one of which is fastened to the carrier bolt and the other of which carries a contact body. The ring has an extension immediately adjacent to the location of the galvanic interruption, with which it is conductively connected to the one disk-shaped body fastened to the carrier bolt. The ring is conductively connected to the further disk-shaped body, which carries the contact body, through an extension of this disk-shaped body, and likewise directly adjacent to the separation point of the ring. The annular sector-shaped regions remaining between the ring and the disk-shaped bodies are filled with poorly conductive or insulating ring pieces. The actual contact body has a small diameter compared to the diameter of the contact piece arrangement, as a result of which the current carrying capacity of the contact piece arrangement is limited.

Another known contact arrangement (GB-A-2038098) also has two disk-shaped bodies, between which there is a field-generating conductor. This has the shape of a ring with diametrically opposite galvanic separation points and a central web connecting the two half rings, which is connected centrally to a carrier bolt. For the current transfer to the actual disk-shaped contact body, the ends of the two half rings are bent out of the ring plane.

The most recently described, as well as the previously described contact piece arrangement, has the property that the current transfer to the contact body takes place at its edge. As a result, contact bodies which are already available and are provided for central fastening to carrier bolts cannot be used. The invention has for its object to design a contact piece arrangement so that a field-generating ring can be used in connection with such a contact body provided for central attachment and power supply and this is exposed to an axially directed magnetic field as effectively as possible.

According to the invention, this object is achieved in a vacuum interrupter of the type mentioned in that the contact body is designed as a pot contact piece with oblique slots, the outer diameter of the pot contact piece corresponding approximately to the inner diameter of the ring and that for connecting each ring with the associated carrier bolt and associated pot contact piece a radially extending conductor piece is provided.

Obliquely slotted pot contact pieces, as z. B. are described in DE-A-26 38 700, are well-developed and tested components of vacuum interrupters with regard to their properties and their manufacturability. It is therefore a significant relief for the development of a high-performance switching arrangement if one of the components can be taken over practically unchanged. In this way, switching piece arrangements with a high specific switching capacity are obtained, since the oblique slots located within the race of the pot contact pieces cause the arc to circulate on the ring surface. Since the axial magnetic field is already available at the outer edge of the contact body and penetrates the entire annular running surface, the arc does not contract at high currents, so that burn-off and metal vapor formation remain low. It is essential that the axial magnetic field is already available at the outer edge of the contact piece and penetrates the entire running surface of the contact body. Since the field windings of both interacting contact pieces are flowed through in the same direction by the current, attractive forces act when the switch is closed, which prevent the contact pieces from lifting under the influence of surge currents.

It proves to be advantageous to design the conductor pieces triangular in cross section, such that together fill a rectangle with conductor pieces. If the spreading current forces occurring between the conductor pieces form a problem, the conductor pieces can also be arranged such that there is a distance in the circumferential direction between the junction points in the ring. It is also recommended to fill the parting line of the ring at least locally with non-conductive or poorly conductive support bodies in order to increase the mechanical stability.

To increase the mechanical stability, it is also advisable to place between the ring and. to arrange the contact body at least locally non-conductive or poorly conductive support body. A further increase in the mechanical strength of the arrangement is in this To achieve connection by a support ring made of non-conductive or poorly conductive material between the support bolt. and the ring is arranged on the side facing away from the contact body.

Advantages for the assembly of the contact system result from the use of a central fastening element through which the contact body and the ring are connected together with the carrier bolt. In order not to disturb the desired current distribution, this fastening element can be made from a non-conductive or poorly conductive material.

The invention is explained in more detail below with reference to the exemplary embodiments shown in the figures.

Figure 1 shows a vacuum interrupter schematically in a longitudinal section.

Details of the contact piece arrangements shown in FIG. 1 can be found in FIGS. 2 and 3, which show an axial section, specifically in FIG. 2 transversely to the radial conductor pieces of the ring and in FIG. 3 in the longitudinal direction of these guide pieces. Figure 4 is a plan view of a ring as a single part.

FIG. 5 shows a switching piece arrangement with an associated ring pulled apart in a perspective view. The ring, which differs from FIGS. 2, 3 and 4, is shown separately in the top view in FIG. 6.

FIG. 7 shows an axial sectional view, corresponding approximately to FIG. 3, of a switching element arrangement which additionally has a support ring.

The vacuum interrupter 1 according to FIG. 1 has a vacuum-tight housing 2 which comprises two end-side, essentially hollow cylindrical insulating bodies 3 and 4 made of a ceramic material and a central hollow metal cylinder 5. A movable carrier pin 6 protrudes upward from the housing 2 and is sealed off from the housing 2 by a bellows 7. A second carrier bolt 10, which is arranged in alignment with the carrier bolt 6 but is fixedly connected to the housing 2, protrudes from the insulating body 4 of the housing 2 on the opposite side.

The carrier bolts 6 and 10 serve as carriers of a movable contact piece arrangement 11 and a fixed contact piece arrangement 12, the corresponding structure of which is described in more detail below.

Each of the contact piece arrangements 11 and 12 has the structure shown in FIG. 2 on the basis of the contact piece arrangement 12. The contact body 14 is a so-called pot contact with a closed running surface, as described for example in DE-A-26 38 700. Essential components of the contact body 14 are a pot-shaped body 15 made of copper, which is provided with oblique slots 16 on its edge. The annular edge of the body 15 is covered with an unslit ring 17, which consists of a chrome-copper composite.

A field winding is assigned to the contact carrier 14 and has the shape of a ring 20, the inside diameter of which corresponds approximately to the outside diameter of the contact body 14. This ring is provided with a parting line 21 running obliquely to the ring plane, on the two sides of which two radial conductor pieces in the form of spokes 22 and 23 open into the ring. In the center of the ring 20, the spokes 22 and 23 are electrically insulated from one another (FIG. 3). Arrows indicate that the current flowing through the carrier bolt 10 first enters the ring 20 through the spoke 22, flows through the ring and is then conducted back through the spoke 23 to the center of the ring. At this point there is an electrical connection to the bottom 24 of the contact body 14, through which the current reaches the actual ring-shaped contact area.

As can be seen when looking at FIG. 2, the current flowing through the galvanically open ring 20 generates an axially directed magnetic field which, due to the coordination of the diameters of the contact body 14 and the ring 20, is already effective on the outer edge of the race 17. This magnetic field has the effect of counteracting the contraction of a diffuse arc discharge into a concentrated arc channel. The switching capacity of a vacuum interrupter can be increased considerably as a result of the fact that the race 14 is heated less locally and less metal vapor is released. The arrangement of the oblique slots 16 also contributes to this, which, in conjunction with corresponding opposite slots of the associated further switching element arrangement 11, not shown in FIG. 2, causes the arc to move rapidly over the contact surface of the race 17.

A particularly favorable interaction between the slotted contact body 14 and the ring 20 occurs when the slits 16 are designed such that they extend as far as possible into the pot bottom 24 into the center. Then eddy currents, which cause a phase-shifted and thus disturbing magnetic field in the zero crossing of the current, are largely suppressed. The arrangement of the slots can be seen in particular in FIG. 5, where they are designated by 42.

As can be seen, the contact body 14 and the ring 20 are arranged axially immediately adjacent. In the region of the mutually facing edges, support bodies 25 are arranged, which are made of a poorly conductive or non-conductive material, for. B. ceramic, can be used to support the two parts against each other. and electrically isolate. Similar support bodies 26 are located in the parting line 21 between the spokes 22 and 23, which start from the parting line 21 of the ring 20. An areal In contrast, there is contact between the spoke 23 and the bottom 24 of the contact body 14 because the current is transferred to the contact body here. The assembly is held together by a screw 27 which extends through the bottom 24 of the contact body 14 and the central part of the spokes 22 and 23, and _'in a threaded blind hole 30 of the support bolt 10 is screwed. The corresponding lower end 31 of the screw 27 is designed to be thickened such that there is no contact on the remaining length between the screw 27 and the spokes and the blind hole of the support bolt 10. Thus, only a small part of the current can flow directly from the carrier bolt 10 to the contact body 14, which is lost for the generation of the desired axial magnetic field. If the screw 27 is made of a material with poor electrical conductivity, the loss mentioned can be reduced further.

The spokes 22 and 23 are traversed by the current in the opposite direction. This leads to repulsive forces that can be absorbed in a suitable manner. For example, this can be done by arranging one or more screws or similar fasteners 32, which is shown in FIG.

The current forces acting on spokes 22 and 23 can be made even more manageable if, instead of the triangular cross-sectional shapes according to FIG. 3, which together form a rectangle, at least part of the radial length of the spokes is designed with a rectangular shape according to FIG. 5 , with the joint between them lying parallel to the contact level. The repulsive forces then only act in the axial direction, while in the shape of the spokes shown in FIG. 3 they also have a tangential component, which act in the sense of an expansion of the ring. In both cases, however, the spokes are superimposed on one another in accordance with FIG. 4.

If, on the other hand, one arranges the spokes in a contact piece arrangement 33 according to FIGS. 5 and 6 in such a way that they open into the ring at a distance in the circumferential direction, the repulsive forces are compensated for in the correct design and a ring arrangement largely free of current forces is created. In this variant, the ring serving as a field winding is designated by 35, the upper spoke to be connected to the bottom of the contact body by 36 and the lower spoke by 37. The operation of this arrangement consists in the fact that on a part of the circumference, namely over the length of the separating joint 40, the same direction of the current exists on both sides thereof, and attractive forces thereby arise. At the same time, the repulsive forces between the oppositely flowing spokes 36 and 37 are relatively low due to their increased distance. This distribution of the current i entering through the carrier bolt 34 is indicated by arrows both in FIG. 5 and in FIG. 6.

In the perspective view of the contact piece arrangement 33 according to FIG. 5, the contact body 41 and the ring 35 are shown pulled apart. This contact body corresponds essentially to the already explained contact body 14 according to FIG. 2. In addition, it can be seen that the obliquely arranged slots 42, which serve to drive the switching arcs in the circumferential direction by forming a current loop, are extended into the bottom 43 and are extended extend to close to the center.

The switching element arrangements of vacuum interrupters, in particular those for higher nominal currents and switching capacities, are exposed to considerable mechanical stress during operation. If there should therefore be a reason to make the contact piece arrangements described so far mechanically particularly robust, this can be done by a support ring as shown in FIG. The contact piece arrangement as such corresponds to Figures 2 and 3. In addition, the support pin 45 is provided with a shoulder 46 on which a z. B. from a ceramic material support ring 47 rests. On its outer circumference, the support ring 47 is provided with a recess 50 on which the ring 20 serving as a field winding rests. The impact forces acting on the contact body and the ring 20 when switched on do not therefore need to be absorbed by these parts alone, but rather are guided via the support ring 47 onto the carrier bolt 45. Under certain circumstances, it may be sufficient to use a supporting body which acts in the same way instead of a closed supporting ring and, starting from an annular hub, has radial arms on which the ring serving as a field winding rests at individual points.

Claims (9)

1. A vacuum switch (1) comprising two contact arrangements (11, 12; 33) which can be moved relative to one another and which are arranged on carrier bolts (6, 10 ; 34), which have the basic shape of a cylindrical disc, and which in each case have a contact body (14; 41) which has a closed contact surface for the arc, and a ring (20 ; 35) which is arranged on the rear of said contact body and is only conductively interrupted once at its periphery and serves to produce an axially directed magnetic field, the connection of each ring to its assigned carrier bolt (6, 10 ; 34) and its assigned contact body (14 ; 41) being directly effected from the position of the conductive interruption of the ring, characterised in that the contact body is formed as a cup-shaped contact member (14 ; 41) with oblique slots, the outer -diameter of the cup-shaped contact member corresponding approximately to the inner diameter of the ring (20 ; 35) ; and that, in order to connect each ring (20 ; 35) to its assigned carrier bolt (6, 10 ; 34) and its assigned cup-shaped contact member (14 ; 41), there is in each case arranged a radially-extending conducting member (22, 23 ; 36, 37).

2. A vacuum switch as claimed in Claim 1, characterised in that the separating line (21, 40) is arranged obliquely to the plane of the ring (20, 35) (Figures 2, 5).

3. A vacuum switch as claimed in Claim 1, characterised in that each conducting member (22, 23) has a triangular cross-section and both conducting members together form a rectangle (Figure 2).

4. A vacuum switch as claimed in Claim 1, characterised in that there is a gap between the discharge points of the conducting members (36, 37) in the peripheral direction.

5. A vacuum switch as claimed in Claim 1, characterised in that the separating line (21 ; 40) of the ring (20 ; 35) is at least locally filled with non-conducting or poorly conducting supporting bodies (25).

6. A vacuum switch as claimed in Claim 1, characterised in that at least locally non-conducting or poorly conducting supporting bodies (24) are arranged between the ring (20) and the contact body (14) (Figure 3).

7. A vacuum switch as claimed in Claim 1, characterised by a supporting ring (47) which is arranged between the carrier bolt (45) and the ring (20) on the side facing away from the contact body (14), and which consists of a non-conducting or poorly conducting material.

8. A vacuum switch as claimed in Claim 1, characterised in that the contact body. (14) and the ring (20) are commonly connected to the carrier bolt (10) by means of a central fastening element (27) which passes through the conducting members (22, 23) and consists of a non-conducting or poorly conducting material (Figure 3).

9. A vacuum switch as claimed in Claim 1, characterised in that the slots (16 ; 42) extend into the base (24) of the cup-shaped contact members (14 ; 41) to near the centre.

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