EP0468272B1 - Electrical switching device - Google Patents

Description

The invention relates to a switch drive, in particular a circuit breaker drive, with a detachable latching device comprising a plurality of links for opening or closing the electrical contact system, at least one link being lockable for a short time in a predetermined position or detachable therefrom, cf. DE-A 22 36 584.

In the case of electrical switching devices including contactors, the above-mentioned elements are important in order to carry out opening or closing operations and to achieve defined on or off operating states. Such devices have, for example, a mechanical locking element for the switch lock, for example in the form of a half-wave. Furthermore, damping elements are necessary for braking the elements moving during the switching-off process or their masses, as well as suitable locks, in order to prevent the rebounding and thus the undesired brief closing again. Finally, locking members are a necessary component for auxiliary release devices such as undervoltage releases. Finally, it is a matter of locking the operating state, which has hitherto been done by a power coil that consumes a relatively high power during the entire operating time, it being possible for two contactors to be mechanically latched to one another in order to preclude their simultaneous operation.

In all of the above cases, suitable locking or damping elements are required, which were previously unsatisfactory in the following points: The main disadvantage is the movement of the mechanical parts that is too slow in time. The positional dependency of the elements in operative connection, which fluctuates within narrow limits, has a lasting negative impact on reliability. These links are also not electronically controllable, because the previous mechanical solution requires a much higher power requirement for tripping than the control electronics can deliver. Finally, the previous mechanics require the production of expensive and very precisely dimensioned links.

An example is provided by the subject matter of the German design specification 2236 584 mentioned at the beginning relating to a rebound block for a switching device, the trigger of which is from a short-circuit current level from about 30 kA to 50 kA. However, modern switches have switching capacities up to over 100 kA, which means that this area is difficult to control due to the bouncing conditions. At higher short-circuit currents there is in particular the problem that the blocking function can no longer be guaranteed with safety, ie there is a risk that the switch closes again. So far, no possibility is known to match the bounce conditions to the respective short-circuit current that actually occurs. The range from 3o to 100 kA given by way of example is too wide to be optimally covered by conventional means.

Furthermore, GB-A-2 111 171 discloses a controllable shock absorber with electroviscous liquid in a container. However, this state of the art does not give any indication of electrical switching devices. There is also no indication that the use of the electroviscous damping element for damping and for locking the switch drive means that only one component is used.

The invention has for its object to simplify a switch drive, in particular a circuit breaker drive with damping and locking elements. This object is achieved by the features characterized in claim 1.

Further preferred embodiments are characterized in the subclaims.

The invention is described below with reference to two exemplary embodiments, from which further features and advantages of the invention result.

Figur 1

das Schema eines Schaltschlosses mit elektronischer Verklinkung;

Figur 2

eine Rückprellsperre für ein Schaltgerät.

In the accompanying drawing:

Figure 1

the diagram of a key switch with electronic latching;

Figure 2

a rebound lock for a switching device.

Figures 1 and 2 consistently show a contact system with the contact mechanism of a circuit breaker of higher nominal current. In detail, the fixed main contact or the main contact is designated by 10, the movable main contact by 11. This is in turn pivotally mounted in the switching lever 12 and is pressurized by the contact pressure spring 13 in the ON position. The selector shaft 14 is rotatably mounted in the housing, not shown, and has a conventional clamp 15 which is fixed on the selector shaft 14 and is connected to a coupling rod 16, which in turn moves the shift lever 12.

Furthermore, the selector shaft 14 has a stuck driving lever 18 (sometimes called a crank), which with the Lock mechanism is connected. The lock mechanism includes, in particular, the knee joint consisting of the same parts 19a and 19b, the roller lever 20 with rotatably attached roller 20a and the ratchet lever 21, which in the case of FIG. 2 is supported on the half shaft 22.

Both figures show the contact system and the associated lock mechanism in the ON position, the link rod 24 together with the associated deflection lever 25, which is rotatably mounted on the deflection shaft 26 and rests on the stop 28, in a defined position. In the OFF position, the driving lever 18 lies on the stop buffer 27.

Furthermore, FIG. 2 shows a current sensor 30 and a trigger 31 electrically connected to it, which controls the level of the field strength and thus the degree of the viscosity of the liquid.

The parts essential to the invention now relate to the link 1, which acts directly or indirectly on a suitable point of the contact mechanism, in particular on the latch lever 21 (as shown in FIG. 1) or on the selector shaft 14 (as shown in FIG. 2). The member 1 comprises a piston 1a with overflow openings, which extends into a closed container 2, which in turn is filled with an electroviscous liquid 3. The electrodes can be divided, for example, in the axial direction as the upper and lower electrodes 4a and 4b in the case of FIG. 1. Likewise, a half-shell division is easy to implement, as indicated in FIG.

The function is explained in more detail below, initially in the case of a switch lock with electronic latching according to FIG. 1.

Figure 1 shows the latched position ON. If triggering is now to take place for the purpose of opening the contact system, be it by means of a protective release or by specific operational control signals, the voltage at the electrodes 4a, 4b is switched off. This means that the lifting cylinder 1a locked in the ON position by the solidified electroviscous liquid 3 is released and moves downward under the action of the contact forces (including spring 13) or, in the case shown, dips deeper into the container. Thus, the pawl lever 21 releases the roller 20a and the roller lever 20 moves counterclockwise in such a way that the knee joint 19a, 19b is brought into the unstable position via the extended dead center. The driving lever 18 together with the switching shaft 14 thus rotates counterclockwise under the pressure of the contact system and opens the movable main switching element 11 via the coupling rod 16 and the switching lever 12.

The movement described ends when the driving lever 18 comes to rest against the elastic stop buffer 27 in accordance with the OFF position.

The main advantage of replacing conventional latching elements, in particular the half-wave shown in FIG. 2, by the arrangement according to the invention according to FIG. 1 is that this new latching device can be controlled electronically. The related advantages have already been mentioned above.

The function of the rebound barrier according to the invention is explained in more detail below in connection with FIG. 2.

It is interesting here that the triggering takes place at higher, impact-critical currents. This means that correspondingly higher electrodynamic forces occur in the system and have an accelerating effect on the opening movement including rotation of the selector shaft etc. The stop of the driving lever 18 on the stop buffer 27 is relatively violent and can have the undesirable consequence that recoil forces of such magnitude occur that the movement of the selector shaft 14 and the coupling rod 16 are reversed, so that the shift lever 12 swings back to the left in the picture Neighboring the main contact piece 10. Since there are still ionized gases in its area, there is a considerable risk of reignition.

The rebound lock according to the invention serves to prevent this undesirable rebound process. If the current to be switched off, in particular a short-circuit current, reaches the order of magnitude that is critical to bounce, the sensor 30 automatically detects this order of magnitude and acts on the electrodes 4a, 4b via the trigger 31 in such a way that the viscosity of the liquid 3 increases to the extent that the movement of the link 1 or the lifting cylinder 1a in the liquid 3 is correspondingly strongly damped, if necessary until complete blocking in the region of the end position of the cylinder 1a corresponding to the OFF position. The feared rebound is thus reliably prevented.

Compared to known mechanical rebound locks, there are the following major advantages: controllable viscosity and thus damping, which can be controlled electronically directly until locked; Suitability for the inexpensive expansion of existing electronic protection modules.

The container 2 and the reciprocating piston 1a immersed therein can be designed in different ways, in particular the arrangement of the electrodes. As already mentioned, the electrodes can be divided, for example, in a radial or axial respect. The overflow openings of the piston 1a can be formed in a conventional manner. This applies to the design in general, the sealing against the member 1 and the isolation of the electrodes from each other and to the outside. In a special embodiment, a membrane can be provided at the end in the container 3, which delimits a compressed air cushion 5 from the electroviscous liquid. In the case of complete solidification of the liquid 3, this compressed air cushion 5 is intended to dampen the mechanical shock pulses and thus reduce the wear on the parts concerned.

In a preferred design, the two electrodes 4a and 4b can be arranged on both sides of the overflow openings in the piston 1a in such a way that even when a low field strength is applied, the viscosity change only occurs in the area of the overflow openings and the piston is thus damped very precisely.

Electrical switchgear Reference list

1

element

1a

piston

2nd

container

3rd

liquid

4a, 4b

interacting electrodes

5

Air cushion

10th

fixed main contact (main contact)

11

movable main contact

12th

Shift lever in which part 11 is mounted

13

Contact pressure spring

14

Control shaft, rotatably mounted in the housing

15

Clamp, sits firmly on selector shaft 14

16

Coupling rod, acts on shift lever 12

18th

Driving lever (usually called crank), sits firmly on selector shaft 14

19a, 19b

Knee joint

20th

Roller lever

20a

roller rotatably attached to the roller lever 20

21

Ratchet lever

22

Half wave

24th

Link rod

25th

Bell crank

26

Deflection shaft

27

Buffer for part 18 in the OFF position

28

Stop for part 25 in the ON position

30th

Current sensor

31

trigger

Claims (5)

1. Switch drive, in particular a circuit breaker drive, with a releasable latching equipment comprising several members for the opening or closing of the electrical contact system (10, 11), wherein at least one member (1) is arrestable in a preset position for a short time or releasable from this, characterised thereby, that the member (1) extends either directly or by means of an articulated additional member as damping and blocking member into a closed container (2), which is filled with an electroviscous liquid (3) and displays electronically controllable electrodes (4a, 4b) for the production of an electric field, by which the viscosity of the liquid (3) is variable or controllable.
2. Switch drive according to claim 1, characterised thereby, that the electrodes (4a, 4b) are drivable by electronic trigger devices (31), the sensors (30) of which detect the height of the current and effect the increase in the field strength in the region critical for bouncing.
3. Switch drive according to claim 2, characterised thereby, that the entering member (1) is constructed in the shape of a piston and that the piston (1a) displays openings for the passage of the electroviscous liquid.
4. Switch drive according to claim 3, characterised thereby, that the container (2) consists of two half shells which are one insulated form the other and constructed as electrodes (4a, 4b).
5. Switch drive according to claim 3, characterised thereby, that the electrodes (4a, 4b) are arranged in the region of the piston openings (excess current openings).

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