WO2003005393A1

WO2003005393A1 - Vacuum interrupter for high short circuit currents

Info

Publication number: WO2003005393A1
Application number: PCT/DE2002/002354
Authority: WO
Inventors: Wilfried Haas
Original assignee: Siemens Aktiengesellschaft
Priority date: 2001-06-29
Filing date: 2002-06-27
Publication date: 2003-01-16

Abstract

The invention relates to a vacuum housing, which is provided for use in low-voltage arrangements and comprises contacts that are situated inside the switching space, of which at least one is a fixed contact and at least one is a mobile contact that, together, form a contact pair. For use in the low-voltage region, the invention provides that a number of contact pairs (10a, 20a, ... to 10f, 20f) are provided inside the switching space (8) of the housing (1). These contact pairs are electrically connected in parallel, whereby the area occupied by the contacts (10a - 10f; 20a - 21) equals at least 30 % of the cross-sectional area inside the switching space (8, 48), and the area of the contacts (10a - 10f; 20a - 20f) equals at least 45 % with regard to the maximum area of a single contact (10). This enables a reduction in the contact force that has to be given in the event of a short circuit in order to ensure a selective behavior with regard to switches connected down therefrom.

Description

description

Vacuum holding tube for high short-circuit currents

The invention relates to a vacuum interrupter for high short-circuit currents, with a vacuum housing and contacts arranged therein, at least one of which is a fixed contact and at least one is a moving contact, with a plurality of pairs of contacts which are electrically connected in parallel. Such a vacuum interrupter is the subject of DE 26 00 305 AI, applications in the medium voltage and high voltage range are provided there. The previously known switching tube is not suitable for the low-voltage range.

Low-voltage vacuum switches should be usable and selective at high currents that determine the power range, for which the contacts are often designed as radial field contacts. When using special radial magnetic field contacts, not only does the repulsive force acting as a result of the current flow in the current transition point occur, but also a repulsive current loop force comes into play due to the current flow in the contacts. To ensure that selective behavior is guaranteed for low-voltage circuit breakers with vacuum interrupters, even for short-circuit currents above 70 - 80 kA, closing forces of several 10 kN are necessary when using this type of contact. Since this is very difficult to achieve with the conventional switch lock designs, this problem must be solved in a similar way to conventional low-voltage air switches, where there are several contact points.

In order to reduce the contact closing forces which are necessary for the selective behavior of low-voltage vacuum switches, the use of flexible contacts which have multiple current transitions has already been proposed. However, studies show that such elastic "multi-contacts" can only be implemented to a limited extent and with considerable effort. can be isolated and therefore the use of several individual contacts offers advantages.

A frame for the dimensions of vacuum interrupters in low-voltage applications is, to a certain extent, defined for the various switch sizes due to the usual pole center distances. It is also complied with by the tubes described in the patent documents DE 198 02 893 A1, DE 199 10 148 AI and WO 99/38181 AI, which currently. can be used for low voltage vacuum circuit breakers.

The contact and inner diameter d or D of the latter tubes, which have a spiral contact pair, are approximately determined by the relationships for three-phase limit short-circuit currents in the range I = 50 - 150 kA and mains voltages up to 1000 V.

d D _f = (0.88 ... 0.92) _r : resp. = (1.20 ... 1.24) ₁

[mm] [kA] [mm] [kA]

described.

Proceeding from this, it is an object of the invention to provide a vacuum interrupter which is suitable for high short-circuit currents in the low-voltage range and in which, despite reduced contact-closing forces, a separation of the contacts in the event of a short-circuit is avoided before the switch lock is released.

The object is achieved according to the invention in a low-voltage vacuum interrupter of the type mentioned at the outset by the features of patent claim 1. Developments of the invention are specified in the subclaims.

The invention specifies a technical teaching specifically for low-voltage vacuum switches, switching contacts being able to be arranged closely next to one another in order to achieve high switching powers with low contact forces. According to the invention, that in the case of radial magnetic field or plate contacts instead of the largest possible switching contact - as in the prior art - a plurality of smaller switching contacts increase the switching capacity with lower contact forces, thereby creating a compact switching tube for the low-voltage range.

With the invention, therefore, a switching tube is realized, the switching space, similar to the tubes described in DE 198 02 893 AI, DE 199 10 848 AI and WO 99/38181 AI, is compact, in contrast to medium and high voltage tubes on one Screen that surrounds the contacts potential-free is dispensed with. From DE 26 00 305 AI vacuum interrupters are known for the medium and high voltage level with several pairs of contacts connected in parallel in a tube housing, but have not found their way into practice.

In the latter arrangement, the area utilization of the control room cross section is approximately 10%. In contrast, within the scope of the invention, a lower limit value of approximately 30% is reached, which corresponds to a considerable increase with a corresponding improvement in the switching capacity. If one starts from the area available for the contacts instead of the control room cross-section, there is a limit value of approximately 45%, with area occupancies between 60% and 80% being achieved within the scope of the invention. The control room can advantageously have a predetermined geometry. Conventional tube housings can be used for this, which have a circular cross section in a known manner, or also housings which have a rectangular or square cross section. Such a cross section is not used in medium and high voltage tubes because of the associated field strength increases. The latter rectangular housing can be produced in a simple manner. In the invention, by using n pairs of contacts arranged in parallel in a switching chamber, the closing force can advantageously be reduced approximately to an nth.

In the prior art, AMF contacts are preferably used for high voltage and medium voltage, in which, in addition to the repulsive so-called “current forces,” attractive current loop forces act. In contrast, radial magnetic field contacts which have repulsive current loop forces are preferably used at low voltage. Under these conditions, large contact forces are necessary in the event of short-circuit currents in order to prevent contact separation before the switch lock is released. Here the subdivision of the contacts into partial contacts offers the simple possibility of reducing the total contact forces required.

With the invention, the contact force can thus be reduced in the low-voltage range in vacuum interrupters by the arrangements according to the invention of a plurality of radial magnetic field or plate contact pairs in a tube in the same way as in known air switches. Calculations within the scope of the invention have shown that the geometric dimensions of such tubes need not be larger than those which are equipped with a single contact.

Further details and advantages of the invention result from the following description of figures of exemplary embodiments with reference to the drawing in conjunction with the patent claims. They each show a sectional view

Figure 1 shows the structure of a known from the prior art

Low voltage vacuum holding tube, FIG. 2 shows the top view of the control room from FIG. 1, FIG. 3 shows a control room corresponding to FIG. 2, which is equipped with four contact pairs, 4 shows a graphical representation to illustrate the achievable technical improvements as a function of the number of contacts when the tube is round, FIG. 5 shows a control room with a rectangular cross section, which is equipped with six pairs of contacts, FIG. 6 shows a graphical representation as in FIG Formation of the tube, Figure 7 to Figure 9 alternatives for the individual insulation between moving contact and fixed contact,

10 and 11 the common insulation between moving and fixed contacts with different designs of the fixed contacts and the means for lifting movement of the moving contacts and FIG. 12 the improvement of the housing stability by means of reinforcing ribs.

In the figures, the same or equivalent parts have the same or corresponding reference numerals. Some of the figures are described together.

As is known, a low-voltage vacuum interrupter consists of two hollow cylinders insulated from one another, the end faces of which are closed with metallic surfaces, so that an evacuable housing is formed. The movable contacts are carried out through the end plate that closes off the cylindrical switching space by means of circular-cylindrical bellows or round shaft membrane disks. These each have a centrally arranged power supply bolt. The dimensioning of the membrane disks is described in detail in DE 199 10 148 AI. The fixed contacts are connected to the other end face, in which their common outward current connection is integrated or to which this can be attached.

Specifically, the switching tube 1 shown in FIG. 1 essentially consists of a cylinder 2 connected to it. the ring cylinder insulation 3 and metallic-cylindrical bellows 4, which are each connected to one another in a vacuum-tight manner. This structure is closed on both sides by metallic plates 5 and 6.

The switching tube 1 according to FIG. 1 encloses a switching chamber 8, in which two switching contacts 10, 20 are arranged so as to be movable relative to one another. The switching contacts 10 and 20 are of identical construction and are mirror images of each other and assume the switching function. In detail is

Switching contact 10 is designed as a fixed contact via a switching pin 11 and switching contact 20 is connected to the diaphragm bellows via pins 21 and 22 and is therefore movable. The plan view according to FIG. 2 shows that there is a cylindrical control room between square base plates. The control room 8 contains a pair of contacts with the contacts 10 and 20, with an all-round shielding being unnecessary in such an arrangement. This provides the prerequisites for a contact structure of the switching chamber and the contact arrangement located therein.

The switch contacts 10, 20 in FIG. 2 can be conventional plate contacts. However, they can also be designed as so-called radial field contacts, each with spiral-shaped slots that are assigned to one another in a mirror-image manner, as a result of which the switching capacity is correspondingly increased.

FIG. 3 shows a control room 8 within a cylinder jacket 2 with a diameter D, in which four circular contacts 10a, 10b, 10c and 10d are shown. Each contact 10a to d has the radius r _E , two adjacent contacts each having a distance e tangentially. The circumference of the contacts 10a to 10d touch a circle with a radius d.

The diameter of a contact generally determines the switching capacity. For the geometric design of the contacts However, there must be sufficient insulation distances to the tube cylinder and other metallic parts. If the dimensioning information is taken into account in FIG. 3, it follows that the area covered by the contacts 10a to d is approximately 30% of the area of the control room 8. If the ring-shaped edge region with the width a is not taken into account and a surface contact with a diameter d is used as a comparison variable, the value is more than 45%, in particular with four contacts in FIG. 3, about 65%. This is carried out further below using relationships 4 and 8 to 10 for radial magnetic field contacts.

In the graphical representation according to FIG. 4, the number of contacts is plotted on the abscissa, whereas the ordinate alternatively plots the area utilization on the one hand and the switching switching capacity on the other. A tube with a round cross-section is a prerequisite. In FIG. 4, the graph 41 indicates the area utilization and the graph 43 the increase in switching power. When using the area, a contact number 1 assumes 100% use of the area, since the annular edge in the control room is not included in these considerations.

It can be seen from FIG. 4 that the switching power is first reduced when the number of contacts is doubled, which is explained by the fact that in a round cross section two smaller, contacting round cross sections make poor use of the area. With an increase to three or more contacts, however, the area utilization increases, in particular up to a value of approximately 0.7 for seven contacts, since in the case of an arrangement with six contacts, an additional contact can be arranged in the center of the circle on a circumference. Subsequently, the use of space with higher contact numbers drops again, with arrangements with more than 10

Contacts can result in internal maxima, which is not shown in Figure 4. The switching capacity increases continuously and at least doubles in every case, in order to then asymptotically enter a limit value.

It can be seen that with the arrangement with four contact pairs, which are electrically connected in parallel, a higher switching capacity than the contact arrangement with a single contact pair 10, 20 according to FIG. 1 can be achieved if the sum of the diameters of the individual contact pairs is greater than the diameter of the Arrangement with a pair of contacts is. In particular, however, with such an arrangement there is a reduction in the contact force, which must be provided in the event of a short circuit to ensure selective behavior. In the prior art, the switching power was already limited because in practice it is not possible to implement contacts with a diameter of d, for example.

FIG ^. 5 shows a section of a rectangular housing 42 which has the internal dimensions S and T. In the space 48 enclosed by the rectangular housing 42, six round contacts 10a to 10f are arranged, each of which again has the radius r _E , adjacent contacts being spaced apart by e. A rectangle with dimensions t and s is enclosed by the external tangents to the individual round contacts 10a to 10f.

In FIG. 5, compared to FIG. 3, there is a more favorable area occupancy of the contacts 10a to 10f in the available area of the control room 48. Taking into account the dimensioning information, the area occupancy is approximately 50%.

FIG. 6 shows a representation corresponding to FIG. 4 for a switch housing with a square or rectangular cross section. Graph 61 shows the area utilization and graph 63 the switching capacity. The following apply relationships 4, 8 and 12 dealt with below for radial field contacts.

It can be seen from FIG. 6 that, in principle, the use of the area continuously decreases starting from the number of contacts 1, which can be explained by the fact that, for example, a square area can be optimally filled by a round contact. In the case of several smaller contacts, however, a free space between the contacts must be taken into account, which consequently assumes this proportional value as the number of contacts increases and the space utilization is reduced. Nevertheless, the switching capacity rises continuously to higher values and can, for example, almost triple from the transition from the number of contact pairs 1 to a number of contacts 10.

In the arrangements according to FIGS. 3 and 5, the insulation of the moving contacts from the fixed contacts can either be common for all contact pairs, that is to say as a ring in the housing, as described in DE 198 02 893 AI, or as individual insulation for each contact pair a housing face.

From FIGS. 7 to 9 there are various possibilities for the individual insulation and for carrying out the lifting movement of the moving contacts 20a, 20b, .... The elements are designated in accordance with FIG. 1. As an alternative to the bellows 4 according to FIG. 1, a so-called wave membrane disc 44 is provided in FIGS. 8 and 9. In principle, such a wave membrane disc 44 has the same function as the bellows 4, with the proviso that overall only minor stroke movements are possible. However, these lower lifting movements are sufficient for the low voltage range. The use of a wave membrane disc 44 is particularly advantageous because it allows the switching space to be flatter and the vacuum switch housing to be made more compact, as will become clear below, for example, from the comparison of FIGS. 10 and 11. For the two alternatives of bellows and membrane bellows, the case of a common insulation ring is shown in FIGS. 10 and 11. It is essential here that the end faces 5 and 6 are designed essentially in accordance with FIG. 1 and the insulation ring 3 is interposed. On the basis of the tubular shapes which are alternatively round or rectangular in FIGS. 10 and 11, the insulator can consequently not only be circular, but also rectangular or square. Specifically in FIG. 11, the fixed contact 10 is designed as a common plate contact, while the moving contacts 20a, 20b on the membrane bellows 44a, 44b are individual contacts, which are advantageously designed as radial magnetic field contacts. With such an arrangement, the switching capacity is not as high as that shown in FIG. 10. The reduction in contact force is retained.

In the case of tubes with a single annular insulator, the bellows or membrane disks of the movable individual contacts are connected directly to one end plate.

In the case of radial magnetic field contacts, which should preferably be designed as spiral contacts, the radius r _{RMF of} an individual contact should be in the range 20 mm <Γ _RMF <30 mm (2). The radius r _{P of} a corresponding plate contact should be limited to 1 mm ≤ r _p ≤ 20 mm (3) with regard to the switching capacity of the overall arrangement, which is determined both by the area of a pair of contacts and their number.

Taking into account asymmetries in the current distribution, the available three-phase switching capacity .DELTA.l of an individual contact with radial magnetic field contacts can be determined ΔIRMF _ = _Λ 1.8 ₀ ΓRMF

[kA] [mm] and with plate contacts with

ΔI _T

Specify [kA] [mm]. In all embodiments of the tubes, the smallest distance a between the individual contacts and the shield or the tube housing wall is ^α (0.10 ... 0.15) ^ (6)

[mm] [kA] is given, although the condition a> 8 mm (7) should be fulfilled.

The distance e between the individual contacts should, on the one hand, be as small as possible, so that arcing in all contact gaps is ensured quickly. Given the unavoidable fluctuations in the separation of the contact pairs, an arc initially arises in the gap between the contacts that opened last. The plasma flowing out of it should quickly reach the neighboring column so that arcs can also be ignited quickly and the total current divided into several pairs of individual contacts. Because of the increasing u (i) characteristic of the arc voltage of contracted vacuum arcs, the division into partial currents, the value of which is at least 15-20 kA, is guaranteed for instantaneous currents i above 20-30 kA.

On the other hand, this distance e must also be so large that the contacts do not touch each other due to their melting on the edge over time, and can thus hinder their opening movement. Based on experience, e should therefore typically be at e = 2 ... 5mm - ^■ (8) lie ,

For the interval for the radius of magnetic field contacts specified in (2), the following results from (8):

e (2 * r _RM ) = 3.3 12.5% (8a)

Typically it should be a value

e / (2 * r _FMF ) = 6%: 8b)

If n> 3 individual contact pairs with a radius r _{E are} to be arranged in the round tubes, then a circular area with the diameter d

necessary.

It should be noted that for d

-3 r _E -e> 0 (10)

an additional contact can be made in the center of the tube, and the following applies to the inside diameter D of this tube:

D = d + 2 a. (11)

Based on the dimensioning information, e / 2r _E should be around 5%. Of course, with a large number of small contacts, several contacts can be arranged on a circumference in the center.

In a rectangular tube configuration according to FIG. 5, the individual contact pairs which have a radius r _{E should be} so If the individual contact pairs, which have a radius r _E , are to be arranged in a rectangular tube configuration according to FIG. 5 such that there are contacts in the longitudinal direction p and in the transverse direction q, then the area required for this has the dimensions s = 2-pr _E + (pl ) e or t = 2-qr _E + (ql) e (12). The internal dimensions of the switching chamber then result in: S = 2 pr _E + (pl) e + 2-a or T = 2-qr _E + (ql) -e + 2-a (13)

For the sake of completeness, it should be mentioned that especially the case of the square tube cross-section results from the rectangular switch room according to FIG. 5 when p = q is inserted in the last two relationships. In addition, with regard to low-voltage circuit breakers with nominal current strengths of several kA, single-row arrangements are also particularly suitable.

In the case of the tubes with a rectangular or square cross section, reinforcing ribs 45 can be fitted in the area between two pairs of switch contacts in order to increase the stability of the housing jacket 42. This is shown in detail in FIG. 12. According to Figure 11, the execution of the fixed contacts as a single common round or rectangular plate is possible.

Overall, the examples shown and described in the individual figures show that the division of the contacts into parallel partial contacts results in an increase in the switching power and in particular a reduction in the contact force with a compact construction of the switching tube housing.

Claims

claims

1. Vacuum interrupter for high short-circuit currents, with a vacuum housing and arranged therein, mutually insulated contacts, at least one of which is a fixed contact and at least one is a moving contact, with a plurality of pairs of contacts connected in parallel with one another, characterized in that for use in Low-voltage range, the area occupied by the contacts (10a - lOf; 20a - 20e) in the housing (1) occupies at least 30% of the cross-sectional area in the control room (8, 48) and that the area of the contacts (10a - lOf; 20a - 20f) is covered on the maximum area with a single contact (10) is at least 45%.

2. Vacuum interrupter according to claim 1, so that the switchgear room (8) has a round cross-section and that in a switchgear room (8) with a round cross-section an area utilization of 60 to 70% is selected.

3. Vacuum interrupter according to claim 1, so that the switching space (48) has a rectangular cross-section and that in a switching space with a rectangular, in particular square, cross-section, an area utilization of 90 to 70% is selected.

4. Vacuum interrupter according to one of the preceding claims, that the contact pairs (10a, 20a; ...; lOf, 20f) contain radial magnetic field contacts.

5. Vacuum interrupter according to one of claims 1 to 3, characterized in that the contact pairs (10a, 20a; ...; 10f, 20f) contain plate contacts.

6. Vacuum interrupter according to claim 4, so that the radial magnetic field contacts are spiral contacts whose radius (RRMF) applies:

7. Vacuum interrupter according to claim 5, characterized in that the plate contact has a radius (r _p ) which is in the range:

10 mm <r _p <17.5 mm.

8. Vacuum interrupter according to claim 1, dadurchge - indicates that for a round cross-section of the switching space (8) individual contact pairs (10a, 20a, ... lOf, 20f) with a predetermined radius (r _E ) are available, whereby for the entire diameter ( d)

applies, where

e = (2 ... 5) mm and n> 3 (8).

9. Vacuum interrupter according to claim 1, so that the relationships apply to a rectangular cross-section (42) of the switching space (48):

s = = 2p ^■ ^■ r _E + (pl) ^• ^• e (12a) t = = 2q ^■ ^■ r _E + (ql) • e (12b) where p and q are the dimensions of the rectangle occupied by the contacts (10a - 10f; 20a - 20f) and e is the distance between two adjacent contacts (10 to 10f).

10. Vacuum interrupter according to one of the preceding claims, characterized in that the fixed contacts form a single common round or right ^¬ angular plate (1). (Figure 11)

11. Vacuum interrupter according to one of the preceding claims, that the housing (42) has reinforcing ribs (45) in the area between two pairs of switching contacts (10a, 20a; ...; lOf, 20f) to increase the stability.

12. Vacuum interrupter according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that bellows (4) are present for the lifting movement of the moving contacts (10a, ... lOf).

13. Vacuum interrupter according to claim 12, so that shaft membrane disks (44) are provided for the lifting movement of the moving contacts (20a-20f).

14. Vacuum interrupter according to one of the preceding claims, so that the contact pairs (10a-10f; 20a-20f) are insulated from one another by individual insulation (3).

15. Vacuum interrupter according to claim 14, so that the individual insulation (3) is located between the bellows or membrane bellows (4, 44) and the housing end face (5).

16. Vacuum interrupter according to claim 14, characterized in that the individual insulation (3) is located between the bellows or diaphragm bellows (4, 44) and the movable switching pin (21).