WO2005034162A1

WO2005034162A1 - Method for increasing current load capacity and for accelerating dynamic contact opening of power switches and associated switching device

Info

Publication number: WO2005034162A1
Application number: PCT/EP2004/010213
Authority: WO
Inventors: Ludwig Niebler; Fritz Pohl; Alf Wabner
Original assignee: Siemens Aktiengesellschaft
Priority date: 2003-09-17
Filing date: 2004-09-13
Publication date: 2005-04-14
Also published as: HK1094089A1; CN100481298C; DE10343005B4; CN1849686A; DE502004003078D1; DE10343005A1; EP1671344A1; EP1671344B1

Abstract

Disclosed is a power switch comprising a current path, in addition to at least one moving contact and at least one fixed contact. The current path is guided between the moving contact and the fixed contact in the form of a narrow loop. A dynamic contact closing force and a dynamic contact opening force are produced from a flowing electric current in order to improve current load capacity. As a result, the magnetic force on the moving contact can be altered from small flows to a very high flows. Advantages during transition from operation in normal rating to short-circuit operation are produced. In order to produce said dynamic forces, ferromagnetic parts (20, 30; 21, 22; 25, 26, 28, 29) are dimensioned in a suitable manner and are associated with the allocated device of the switching bridge (4) provided with moving contacts (5a, 5b).

Description

description

Process for increasing the current carrying capacity and for accelerating the dynamic contact opening of circuit breakers and associated switchgear

The invention relates to a method for increasing the current carrying capacity and for accelerating the dynamic contact opening of circuit breakers according to the preamble of claim 1. In addition, the invention relates to an associated switching device with at least one fixed contact and at least one moving contact and with a track and associated splitters.

Such switching devices generally have a translational contact opening movement, the contacts being arranged on a contact bridge and a bridge carrier and a contact force spring being present for the translational movement. In addition, switching devices can have a rotary contact opening movement, to which the invention also relates.

Electrical switching devices for the protection of electrical systems, but also for the operation of electrical consumers, are required to carry electrical currents up to a predetermined level without interference, and higher currents, e.g. Short-circuit currents to switch off in the shortest possible time. For this purpose, they have a switching device drive (mechanical switch lock and / or magnetic drive), which closes the contacts with a specified contact force, and tripping devices (e.g. n-releases or electronically operated actuators), which allow the switching contacts to be opened quickly and therefore the current to be quickly set up Cause arc tension.

Since at very high, prospective short-circuit currents (e.g. I = 50 kA), the dynamic current forces take effect earlier than the momentum transfer of the release element to the moving contact, the short-circuit switching behavior can be improved by optimizing the driving magnetic fields. However, the magnetic field strength, which is dependent on the current level, can already weaken the contact force in the operating current range, for example in the case of motor starting currents, and thus lead to a disturbance in the current carrying behavior. In order to eliminate this problem, the force supplied by the switchgear drive can be increased. However, this leads to larger drives, which increases device costs and construction volume. Both are undesirable for reasons of economy, which is why a solution is required which eliminates the disadvantages mentioned.

To use the dynamic opening forces in electrical switching devices, the current path between the moving and fixed contacts is guided in the form of a tight loop and / or the magnetic field around the current-carrying moving contact is distorted by ferromagnetic arrangements (e.g. slot motor) so that strong Lorenz forces act.

From DE 42 16 080 AI an arrangement for contact force amplification in relay contacts is already known, in which the current path to the moving contact is looped in order to utilize the loop force as an additional contact force. Here, the current path is additionally assigned an iron sheet at a short distance in order to obtain a further magnetic force for increasing the contact force. Furthermore, it is known from DE 199 12 713 AI to provide a blocking element with good electrical conductivity in the case of current-carrying switch contacts. Movement is prevented by parallel, electrical partial currents in the blocking element and in the moving contact until the current and magnetic force exceed a predetermined minimum value. Finally, in the biography "Fundamentals of Switchgear Technology" (Springer-Verlag Berlin 1975), in particular pages 257 to 274, ISBN 3-540-06075-8, general properties of switchgear, in particular also of contactors, are described. However, the arrangements known from the prior art are unable to deliver the desired high, dynamic current forces without sensitively weakening the contact force in the case of large operating currents (motor starting current). As a result, the drive and the contact force must be dimensioned larger.

Proceeding from this, it is the object of the invention to propose a method for increasing the current carrying capacity and for accelerating the dynamic contact opening and to create an associated device which does not unduly weaken the contact force during operating currents.

The object is achieved by the measures specified in claim 1. An associated device is specified in claim 5. Developments of the method on the one hand and the associated device on the other hand are the subject of the dependent claims.

The method according to the invention advantageously uses u-shaped yokes made of ferromagnetic material, preferably made of ordinary steel sheet, for magnetic force amplification. The magnetic force on the moving contact is specifically changed in sign when there is an increase from small currents (rated operation) to very high currents (short-circuit operation). Specifically, this means that a contact-strengthening effect is generated for small currents and a contact-force-weakening effect is generated for high currents, which results in a dynamic opening force. By suitable dimensioning of the ferromagnetic components, a change in the sign or an almost balanced magnetic force curve can be set for small currents.

To implement the invention in terms of the device, a first, U-shaped plate for generating the magnetic closing force and a second, U-shaped plate for generating the magnetic opening force are used as magnetic yokes, which are suitably positioned on the contact arrangement.

Further details and advantages of the invention emerge from the following description of the figures of an exemplary embodiment with reference to the drawing in conjunction with the patent claims. In a schematic representation:

1 shows a switching device with a switching bridge and associated drive,

FIG. 2 shows a detail from FIG. 1 to illustrate the two iron yokes assigned to the switching bridge,

3 shows in perspective the respective orientation of the two U-shaped iron yokes, FIG. 4 shows a contact arrangement with a switching bridge and partial yokes and

Figure 5 shows a contact arrangement with attached partial yokes and two sheets assigned to the partial yokes.

In Figure 1, the functional components of a known

Schützes shown schematically: The contactor consists essentially of a switching chamber 1 with the switching components contained therein and a magnetic drive 10, with the electromagnetically activated mechanical movement of the switching contacts.

In FIG. 1, fixed contacts 3a and 3b are arranged in the switching chamber on fixed contact carriers 2a and 2b and there are associated moving contacts 5a and 5b on a movable switching bridge 4. The contact arrangement with the opposing contacts 3a, 5a and 3b, 5b are assigned in a known manner extinguishing plates 9a and 9b, which are usually part of extinguishing plate arrangements with a running or guide rail 32. The movable switching bridge 4 is coupled via a contact force spring 7 so as to be relatively movable with a bridge support 8 which is moved with the armature 13 by the magnetic drive 10 into the switch-on or switch-off position. Further, relatively movable elements can be contained in the bridge girder, which act on the switching bridge via actuators and can trigger a bridge movement.

The magnetic drive 10 consists in detail of a magnetic yoke 11 with a magnetic coil 12 and a magnetic armature 13 assigned to the yoke, which is connected to the bridge girder 8 via a carrier plate 14. An opening spring 15 acts on the magnetic yoke 11 and ensures the open position of the switching bridges when the magnetic drive 10 is switched off.

In the switching device described above, ferromagnetic parts are present for controlling the contact force, in particular in the switching chamber, two iron yokes 20 and 30, the function of which will be discussed in more detail below. Only the iron yoke 30, which is connected to the running or guide rail 32, can be seen in FIG.

The assignment of the two magnet yokes 20 and 30 to the contact arrangement of fixed contacts and contact carrier, as well as moving contacts and switching bridge, results from FIG. The dimensions of the magnet yokes 20 and 30, both of which are designed as U-shaped sheets, result from the connection of FIGS. 1 to 3. In particular, FIG. 3 shows the geometrical differences of the two yokes that are decisive for magnetization.

In accordance with the arrangement shown in FIG. 2, the geometry and positioning of the U-shaped plate 20 which generates the contact force reacts more sensitively to the electrical current in the switching bridge 4 than the U-shaped plate 30 which generates the opening force. Due to its compact dimensions, the U-shaped sheet 20 is magnetized more quickly than the U-shaped sheet 30 and, due to its small sheet thickness, goes into magnetic saturation at an early stage. In contrast, the entire length of the opening-force-generating U-shaped sheet metal 30 covers the movable contact or the movable switching bridge 4 with contacts 5a and 5b, and has a larger internal width and a larger sheet thickness. In comparison to the contact-force-generating U-shaped sheet 20, its magnetic saturation is therefore only achieved with higher electrical currents.

In the case of a mechanical switching device drive, the contact-force-generating U-shaped plate 20 is fastened either to a switch lock component or to the switch housing. In the case of a magnetic drive in accordance with FIG. 1, the contact-force-generating U-shaped plate 20 is fastened to the bridge support 8 and engages around the switching bridge 4, the bridge support coupling the switching bridge in accordance with FIG. 1 with the drive 10 shown there.

The possibilities for positioning and fastening the contact-force-generating U-shaped plate 20 are not limited to these two cases, as is shown in a further example.

In both cases, the opening-force-generating U-shaped sheet metal 30 is expediently fastened to the switching chamber 1, to the housing or to a resting mechanical component located in the housing.

In FIGS. 1 and 2 described above, the switching bridge carries out a translatory movement, but a rotational movement is also possible if the switching device is designed accordingly. In the case of the rotary movement of a switching bridge, a U-shaped plate 20 or ^20λ and a U-shaped plate 30 or 30 are assigned to the switching bridge on both sides of the axis of rotation, corresponding to a point-symmetrical arrangement. The two U-shaped sheets 30, 30 ^Λ are fixed to the housing or with one connected mechanical component in the housing connected. The two U-shaped plates 20, 20 can also be firmly connected to the housing, or with a switching bridge support which is in positive engagement with the switching device drive (mechanical and / or electromagnetic drive) and rotates with the switching bridge in the switched-off position during the switching-off process.

The u-shaped sheets 20 or 20 and 30 or 30 ^λ are positioned at a predetermined distance from one another so that a magnetic short circuit between the u-shaped sheet 20 and the u-sheet 20 ^x or between the u-shaped sheet 30 and the U-shaped sheet 30 is avoided. The clear width of the respective u-gap is specified as the distance.

In the case of a single-interrupting, rotary moving contact, only 1 u-plate 20 and 1 u-plate 30 are assigned to the moving contact, wherein, as in FIG. 2 and / or FIG. 3, a contact-opening and a contact opening and a suitable arrangement of the two u-shaped plates A contact-closing magnetic force is generated on the current-carrying moving contact, the resulting force of which can change sign when small currents are transferred to high short-circuit currents.

In the case of dynamic contact opening as a result of large current forces, the moving contact or the movable contact bridge moves out of the gap of the U-shaped sheet which generates contact force and dips into the gap of the U-sheet 30 which generates opening force. As a result, the force effect of the first u-plate 20 disappears and the opening force of the second u-plate 30 acts without loss.

In the transition area of the dynamic contact opening movement, ie before the moving contact or the movable switching bridge can leave the gap of the U-shaped plate 20, the magnetic flux striking the moving contact can be regarded as a flux difference Φ ₂ - Φi of the second and first u-plate become. Due to the different sheet thicknesses, the saturation flows will occur in relation to the sheet thickness. If the sheet thickness of the contact-force-generating u-shaped sheet 20 is approximately (10 to 20%) that of the opening-force-generating u-shaped sheet 30, the resulting magnetic field for the transition region becomes approximately 80 to 90% of the field portion of the second u-sheet 30 reduced. In the same way, the resulting magnetic force that contributes to the opening of the contact is reduced.

It is indicated in FIG. 3 that the second U-shaped plate 30 can be part of a running or guide rail 32 which is usually present in such switching devices. The table below shows a dimensioning example for the U-shaped sheets 20 and 30. The dimensions can vary within a predetermined range, whereby the mutual coordination is essential.

It can be seen from the table that the contact force-generating component is only slightly larger than the opening force-generating component until the magnetic saturation of the first u-plate 20 is reached.

By dimensioning the length and the clear width of the U-shaped plates 20 and 30, as well as by the selected covering of the switching bridge, the contact force-generating and the opening force-generating magnetic force components can be set over a larger range.

In a further embodiment according to FIG. 4, instead of the small yoke 20, which is embedded in the switching bridge support 8 at a suitable point, two small yokes 21 and 22 are attached to the side of the switching bridge support 8 on a stationary component of the switching chamber 1 or the switch housing in a force-fitting manner. These two yokes are each positioned between the switching bridge support 8 and the switching contacts 3a, 5a and 3b, 5b. Due to their predetermined distance in the millimeter or submillimeter range from the switching bridge carrier 8, the two yokes 21 and 22 do not hinder the translational movement of the switching bridge carrier 8.

When the yoke 20 is replaced by the two yokes 21 and 22, the two yokes 21 and 22 are to be positioned such that in the closed position of the switching contacts 3a, 3b and 5a, 5b the moving contact carrier 4 is completely in the u-column of the two yokes 21 and 22 or partially submerged. For this purpose, the yokes 21 and 22 are appropriately attached to a stationary component of the switching chamber 1 or the housing.

In the latter modification, the magnetic force generated by the two small yokes 21 and 22 - in contrast to FIG. 2 in particular - is not supported on the magnetic drive of the switching device. This means that the function of the drive cannot be impaired. In a further preferred embodiment according to FIG. 5, two sheets 25, 26 are provided instead of the two small yokes, the flat side of which approximately occupies the position and position of the transverse legs of the yokes 21, 22 in FIG Switching chamber 1 or the housing are non-positively attached.

In the closed position of the switching contacts 3a, 5a or 3b, 5b, the movable contact carrier has a smallest, predetermined distance from the two sheets 25, 26, i.e. a distance in the submillimeter to millimeter range. On the movable contact carrier two U-shaped plates 28, 29 are attached, each with their side legs pointing to one of the two plates 25, 26, so that two magnetic circles are formed, which are magnetized by the electric current in the movable contact carrier, thereby creating a magnetic Holding force is generated on the movable contact carrier.

The yokes or u-shaped sheets 20 or 21, 22 or the sheets 25, 26 with associated u-shaped sheets 28, 29 each consist of ferromagnetic material and generate a magnetic closing force that is directed opposite the large yoke 30 made of ferromagnetic material the switching bridge 4.

The invention described with reference to the individual figures is implemented in particular in a switching device with translatory movement of the moving contact. As in the example in FIG. 1, this can be a contactor. However, the invention can also be implemented without limitation for circuit breakers with a mechanical or with a mechanical / electrical drive.

As mentioned above, however, the invention can also be applied to a switching device with a rotary switching movement, in which case the first yoke or U-shaped plate 20 is the movable rotary contact of the contact piece grips the facing front of the contact carrier, while the second yoke or U-shaped plate 30 encompasses the opening area of the rotary contact on the back of the contact carrier.

Claims

claims

1. A method for increasing the current carrying capacity and for accelerating the dynamic contact opening of circuit breakers with at least one current path and at least one moving contact and at least one fixed contact, the current path being guided in the form of a tight loop between moving and fixed contact and / or the magnetic field around the current-carrying moving contact is distorted by ferromagnetic arrangements in such a way that strong Lorentz forces act as an electrodynamic force with the following measures:

in the switched-on position of the at least one moving contact, the electrodynamic force generated by the ferromagnetic arrangement is formed from an electrodynamic closing force and an electrodynamic opening force,

- The electrodynamic force on the moving contact returns when small currents rise, i.e. during nominal operation, up to very high currents, i.e. in the event of short-circuit operation, the direction around, the magnetic induction (B) of the ferromagnetic arrangement changing the sign,

- With small currents, a ferromagnetic arrangement produces a contact-strengthening effect and with high currents, a contact-force-weakening effect.

2. The method according to claim 1, characterized in that the transition of the magnetic force from a dynamic contact closing force to a dynamic contact opening force is achieved at a predetermined current value by dimensioning the ferromagnetic arrangement.

3. The method according to claim 1, characterized in that a contact-force-weakening effect is permitted for small currents and is limited to a predetermined value.

4. The method according to claim 3, characterized in that the contact force-weakening effect is less than about 50% of the contact force.

5. Switching device containing a switching chamber with at least one fixed contact and at least one moving contact, characterized in that the at least one moving contact (5a, 5b) has at least two ferromagnetic parts (20, 30; 21, 22; 25, 26, 28, 29) for generating at least two dynamic magnetic forces, which are directed opposite to each other in their direction of force, and that the ferromagnetic parts form u-shaped yokes (20, 30) which form the switching bridge (4) for the moving contacts (5a, 5b) are positioned appropriately.

6. Switching device according to claim 5, characterized in that a first, U-shaped yoke (20) for generating a magnetic closing force is associated with the contact bridge (4) with the moving contacts (5a, 5b).

7. Switching device according to claim 5, characterized in that the first U-shaped yoke (20) with the bridge support (8) is non-positively connected.

8. Switching device according to claim 5, characterized in that the first u-shaped yoke from two partial yokes (21, 22) which are associated with the moving contacts (5a, 5b) and are attached to a stationary component of the switching chamber (1) ,

9. Switching device according to claim 5, characterized in that the parts for generating at least one magnetic contact closing force are formed by two U-shaped yokes (28, 29) and associated iron sheets (25, 26).

10. Switching device according to claim 9, characterized in that the yokes (28, 29) are assigned to the moving contacts (5a, 5b) and are non-positively connected to the switching bridge (4).

11. Switching device according to claim 9, characterized in that the iron plates (25, 26) assigned to the yokes (28, 29) are attached to stationary components of the switching chamber (1).

12. Switching device according to claim 5, characterized in that a second, U-shaped yoke (30) for generating a magnetic opening force with the switching chamber (1) is non-positively connected.

13. Switching device according to claim 5, wherein a guide rail is present on the switching chamber, characterized in that the second U-shaped yoke (30) is connected to the guide rail (32).

14. Switching device according to claim 13, characterized in that the guide rail (32) consists of iron.

15. Switching device according to claim 13 and 14, characterized in that the guide rail (32) and the second yoke (30) consist of one part.

16. Switching device according to one of claims 5 to 15, characterized in that the first yoke (20) is substantially smaller than the second yoke (30), preferably about 2x smaller in length.