EP1671344B1 - Method for increasing current load capacity and for accelerating dynamic contact opening of power switches and associated switching device - Google Patents

Description

The invention relates to a switching device according to the preamble of claim 1. It is assumed that switching devices having additional means to increase the current carrying capacity and to accelerate the dynamic contact opening, which is particularly important when used as a circuit breaker.

The above switching devices generally have a translatory contact opening movement, wherein the contacts are arranged on a contact bridge and for translational movement, a bridge carrier and a contact force spring are present. In addition, but switching devices may have a rotary contact opening movement, to which the invention also relates.

Electric switchgear for the protection of electrical equipment, but also for the operation of electrical consumers, the requirement is made to run electrical currents up to a predetermined height trouble-free, and higher currents, e.g. Short-circuit currents, turn 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 predetermined contact force and tripping organs (eg n-trigger or electronically actuated actuators), which cause a quick opening of the switch contacts and therefore the rapid construction of a current-limiting arc voltage ,

Since at very high, prospective short-circuit currents (eg I = 50 kA), the dynamic current forces are effective earlier than the momentum transfer of the trigger on the moving contact, the short-circuit switching behavior can be improved by optimizing the driving magnetic fields. However, depending on the current level, the magnetic field strength can already be determined in the operating current range, For example, at motor starting currents, lead to a weakening of the contact force and thereby to a disturbance of the current carrying behavior. To eliminate this problem, the force supplied by the switchgear drive can be increased. However, this leads to larger-sized drives, which increases the equipment costs and the volume of construction. Both are undesirable for economic reasons, which is why a solution is needed which excludes the disadvantages mentioned.

To utilize the dynamic opening forces in electrical switchgear, the current path between moving and fixed contacts is made in a tight loop and / or the magnetic field around the current-carrying contact is distorted by ferromagnetic arrangements (e.g., slot motor) so that strong Lorentz forces act.

From DE 42 16 080 A1 an arrangement for contact force amplification in relay contacts is already known, in which the current path is looped to the moving contact in order to exploit the loop force as an additional contact force. In this case, the current path is additionally associated with a sheet iron at a small distance in order to obtain a further magnetic force for contact force amplification. Furthermore, it is known from DE 199 12 713 A1 to provide a blocking member with good electrical conductivity in the case of current-carrying switching contacts. By parallel, electrical partial currents in the locking member and the moving contact movement is prevented until the current and magnetic force exceeds a predetermined minimum value. Finally, in the biography "Fundamentals of switching device technology" (Springer-Verlag Berlin 1975), in particular pages 257 to 274, ISBN 3-540-06075-B general characteristics of switching devices, especially of shooters described.

However, the above known arrangements are incapable of providing the desired high dynamic current forces without severely weakening the contact force at high operating currents (motor starting current). As a result, the drive and the contact force must be sized larger.

From US 4,454,490 a contactor with a switching bridge of two pairs of contacts, the properties of breaker contacts are also known, in which iron yokes enclose the contact paths of both pairs of contacts and generate a contact opening force. Between the two yokes, another yoke is attached to the bridge girder, which produces a contact closing force. This should already be realized means to increase the current carrying capacity and to accelerate the dynamic contact opening.

On this basis, it is an object of the invention to provide a further improved switching device, in which in particular the contact force at operating currents is not unduly weakened.

The object is achieved by a switching device with the measures specified in claim 1. Further developments of the sound device are the subject of the dependent claims.

In the invention, U-shaped yokes made of ferromagnetic material, preferably of ordinary steel sheet, are utilized for magnetic force amplification. Such yokes are previously known from the prior art. In the invention that the smaller yoke is less wide in its outer dimensions than the width of the air gap of the larger yoke. The air gap is also to be understood as meaning the adjacent air volume which widens the value in its length by the value of the air gap length.

The inventive design of the yokes is achieved that the magnetic force on the moving contact during the rise From small currents (rated operation) to very high currents (short-circuit operation) the sign changes. This means concretely that at low currents a contact force-enhancing effect and at high currents a contact force-weakening effect is generated, resulting in a dynamic opening force. Due to the inventive dimensioning of the ferromagnetic components, a sign changing or an almost balanced magnetic force profile can be adjusted at low currents.

To realize the switching device according to the invention, 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.

Figur 1

ein Schaltgerät mit einer Schaltbrücke und zugehörigem Antrieb,

Figur 2

einen Ausschnitt aus Figur 1 zur Verdeutlichung der beiden der Schaltbrücke zugeordneten Eisenjoche,

Figur 3

perspektivisch die jeweilige Orientierung der beiden u-förmigen Eisenjoche,

Figur 4

eine Kontaktanordnung mit einer Schaltbrücke und dieser zugeordneten Teiljochen und

Figur 5

eine Kontaktanordnung mit daran angebrachten Teiljochen und zwei den Teiljochen zugeordneten Blechen.

Further details and advantages of the invention will become apparent from the following description of an embodiment with reference to the drawing in conjunction with the claims. In a schematic representation:

FIG. 1

a switching device with a switching bridge and associated drive,

FIG. 2

1 shows a section from FIG. 1 to illustrate the two iron yokes associated with the switching bridge;

FIG. 3

in perspective the respective orientation of the two U-shaped iron yokes,

FIG. 4

a contact arrangement with a switching bridge and this associated partial yokes and

FIG. 5

a contact arrangement with partial yokes attached thereto and two sheets associated with the partial yokes.

In Figure 1, the functional components of a known contactor are shown schematically: The contactor consists essentially of a switching chamber 1 with the switching components therein and a magnetic drive 10, with the electromagnetically activated, a mechanical movement of the switching contacts.

In FIG. 1, fixed contacts 3a and 3b are arranged on fixed contact carriers 2a and 2b in the switching chamber, and movable contacts 5a and 5b associated therewith are provided on a movable switching bridge 4. The contact arrangement with the opposing contacts 3a, 5a and 3b, 5b are assigned in a known manner quenching plates 9a and 9b, which are usually part of quenching plate assemblies with a running or guide rail 32. The movable switching bridge 4 is coupled via a contact force spring 7 relatively movable with a bridge support 8, which is moved with the armature 13 from the magnetic drive 10 in the switch-on or switch-off.

The bridge girder may contain further, relatively movable elements which act via actuators driven on the switching bridge and can trigger a bridge movement.

The magnetic drive 10 consists in detail of a magnetic yoke 11 with magnetic coil 12 and a yoke associated armature 13, which is connected to the bridge girder 8 via a support plate 14. On the magnetic yoke 11 acts an opening spring 15, which ensures the open position of the switching bridges in the off state of the magnetic drive 10.

In the switching device described above are ferromagnetic parts for the control of the contact force and in particular in the switching chamber two iron yokes 20 and 30, whose function will be discussed in detail below. It can be seen in Figure 1, only the iron yoke 30 which is connected to the running or guide rail 32.

From Figure 2, the assignment of the two magnetic yokes 20 and 30 results in the contact arrangement of fixed contacts and contact carrier and moving contacts and switching bridge. The dimensioning of the magnetic yokes 20 and 30, which are both formed as U-shaped plates, results from the connection of Figures 1 to 3. In particular, Figure 3 shows the decisive for a magnetization geometry differences of the two yokes.

According to the arrangement shown in Figure 2 reacts the contact force generating U-shaped metal sheet 20 by its geometry and positioning on the switching bridge 4 sensitive to the electrical current in the switching bridge, as the opening force generating U-shaped plate 30. This means concretely, The U-shaped plate 20 is magnetized faster because of its compact dimensions than the U-shaped plate 30 and is due to its small thickness early in the magnetic saturation.

On the other hand, the opening force-generating U-shaped plate 30 completely or completely covers the movable contact or the movable switching bridge 4 with contacts 5a and 5b over its entire length and has a larger inside width and a larger sheet thickness. In comparison to the contact-force generating U-shaped plate 20, its magnetic saturation is therefore only achieved at 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 switching mechanism component or to the switch housing. In the case of a magnetic drive according to Figure 1, the contact-force generating U-shaped plate 20 is fixed to the bridge girder 8 and engages around the switching bridge 4, wherein the bridge girder couples the switching bridge according to Figure 1 with the drive 10 shown there.

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

The opening force-generating U-shaped plate 30 is expediently fastened in both cases to the switching chamber 1, to the housing or to a stationary, mechanical component located in the housing.

In the figures 1 and 2 described above, the switching bridge performs a translational movement, but with a corresponding structure of the switching device but also a rotational movement is possible. In the case of the rotational movement of a switching bridge, a U-shaped plate 20 or 20 '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 'are fixed to the housing or with a connected in the housing resting mechanical component. The two U-shaped plates 20, 20 'can also be firmly connected to the housing, or with a switching bridge carrier, which is in non-positive engagement with the switching device drive (mechanical and / or electromagnetic drive) and turns off during switch-off with the switching bridge in the off position ,

The u-shaped sheets 20 and 20 'and 30 and 30' are positioned at a predetermined distance from each other, so that a magnetic short circuit between the u-shaped plate 20 and the u-plate 20 'and between the u-shaped plate 30th and the U-shaped plate 30 'is avoided. As a distance, the clear width of the respective u-gap is given as about.

In a simple interrupting, rotary moving contact only 1 u-sheet 20 and 1 u-sheet 30 are associated with the moving contact, wherein as in the figure 2 and / or 3 by a suitable arrangement of the two U-shaped plates each have a contact-opening and a kontaktschließende Magnetic force is generated on the current-carrying moving contact, the resulting force in the transition from small currents to high short-circuit currents can change the sign.

Upon dynamic contact opening due to large current forces, the moving contact or the movable contact bridge moves out of the gap of the contact-force generating U-shaped plate and enters the gap of the opening force generating U-plate 30. 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 region of the dynamic contact opening movement, ie before the moving contact or the movable switching bridge can leave the gap of the U-shaped metal sheet 20, the magnetic flux striking the moving contact can be regarded as a flux difference Φ ₂ -φ _{1 of} the second and first u-metal sheet become. Due to the different sheet thicknesses, the saturation fluxes will adjust approximately in relation to the sheet thicknesses. If the sheet thickness of the contact-force generating U-shaped sheet 20 is about (10 to 20%) that of the opening force generating U-shaped sheet 30, the resultant magnetic field is reduced to about 80 to 90% of the field portion of the second μ sheet 30 for the transition region , In the same way, the magnetic force contributing to the contact opening is reduced.

In the figure 3 it is indicated that the second U-shaped plate 30 may be part of a usually present in such switching devices running or guide rail 32.

In the following table, a dimensioning example for the U-shaped plates 20 and 30 is given. The dimensions can vary in a predetermined range, which essentially depends on the mutual agreement. contact-energizing opening-energizing U-shaped sheet metal in the carrier, 8.5 mm in length, 0.1 mm sheet thickness U-shaped sheet metal as part of the track, 19.5 mm length, 0.8 mm sheet thickness clear width 5 mm clear width 10 mm Cover full (= switching bridge in the u-gap) Coverage - 2mm (= switching bridge in front of the u-gap) S _L1 ≈ 5 mm S _L2 ≈ 13 mm (S _L = air path of the magnetic field lines) (S _L = air path of the magnetic field lines) K _magn = μ ₀ * i ² * 8,5 / S _L1 = μ ₀ * i ² * 1.7 K _magn = μ ₀ * i ² * 19.5 / S _L2 = μ ₀ * i ² * 1.5

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

By dimensioning the length and the clear width of the U-shaped plates 20 and 30, and by the selected coverage of the switching bridge, the contact force generating and the opening force generating magnetic force component can be adjusted over a larger range.

In a further embodiment according to Figure 4, instead of the small yoke 20, which is embedded in the switching bridge carrier 8 at a suitable location, two small yokes 21 and 22 mounted laterally adjacent to the switching bridge support 8 to a stationary component of the switching chamber 1 or the switch housing frictionally. These two yokes are respectively positioned between the switching bridge carrier 8 and the switching contacts 3a, 5a and 3b, 5b. By their predetermined distance in the millimeter or submillimeter range to the switching bridge support 8 hinder the two yokes 21 and 22, the translational movement of the switching bridge carrier 8 not.

When replacing the yoke 20 by the two yokes 21 and 22, the two yokes 21 and 22 are positioned so that in the closed position of the switch contacts 3a, 3b and 5a, 5b of Bewegkontaktträger 4 in the u-column of the two yokes 21 and 22 completely or partially immersed. For this, the yokes 21 and 22 appropriated location on a stationary component of the switching chamber 1 or the housing are frictionally mounted.

In the latter modification, the magnetic force generated by the two small yokes 21 and 22 - in contrast, in particular to Figure 2 - is not based on the magnetic drive of the switching device. As a result, the drive can not be impaired in its function.

In a further preferred embodiment corresponding to Figure 5, two plates 25, 26 are provided in place of the two small yokes, which occupy about the position and the position of the transverse legs of the yokes 21, 22 of Figure 4 with their flat side and accordingly to a dormant component of Switching chamber 1 or the housing are mounted non-positively.

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

The yokes or U-shaped plates 20 or 21, 22 or the plates 25, 26 with associated U-shaped plates 28, 29 are each made of ferromagnetic material and generate the large yoke 30 of ferromagnetic material oppositely directed, magnetic closing force the switching bridge 4.

The invention described with reference to the individual figures is realized in particular in a switching device with translational movement of the moving contact. This can be a contactor as in the example of FIG. However, the invention can also be realized without restriction for circuit breakers with mechanical or with mechanical / electrical drive.

As mentioned above, however, the invention can also be used in a switching device with rotational switching movement to bear, in which case the first yoke or U-shaped plate 20, the movable rotary contact of the contact piece facing the front side of the contact carrier, while the second yoke or U-shaped plate 30 surrounds the opening region of the rotary contact on the back of the contact carrier.

Claims (12)

1. Switching device, containing a switching chamber having at least one fixed contact and at least one movable contact, to which are assigned at least two ferromagnetic U-shaped yokes (20, 30; 21, 22; 25, 26, 28, 29) for generating at least two electrodynamic magnetic forces which are opposite to one another in terms of their force vectors and in which the ferromagnetic yokes (20, 30; 21, 22; 25, 26, 28, 29) are in each case positioned in relation to the at least one movable contact (5a, 5b) so that the force vector generated by the one ferromagnetic yoke onto the at least one movable contact (5a, 5b) points towards the at least one fixed contact (3a, 3b) and the force vector of the other ferromagnetic yoke points away from the at least one fixed contact (3a, 3b), whereby the size of the two yokes (20, 30) is dimensioned such that the smaller yoke (20) can be disposed at least partially in the air gap of the larger yoke (30), to which purpose the external dimensions of the smaller yoke (20) are less wide than the width of the air gap of the larger yoke (30).
2. Switching device according to claim 1, characterised in that the lateral limbs of the U-shaped yokes (20, 30) of the at least one large yoke (30) and of the at least one small yoke (20) point in opposing directions to one another, so that the lateral limbs of the small yoke (20) point towards the transverse limb of the large yoke (30).
3. Switching device according to claim 2, characterised in that the large U-shaped yoke (20) is connected to the bridge support (8) in a friction-locked manner.
4. Switching device according to claim 2, characterised in that the first U-shaped yoke is formed of two partial yokes (21, 22) which are assigned to the movable contacts (5a, 5b) and are affixed to a stationary component of the switching chamber (1).
5. Switching device according to claim 1, characterised in that the components for generating at least a magnetic contact closing force are formed by two U-shaped yokes (18, 29) and iron plates (25, 26) assigned thereto.
6. Switching device according to claim 5, characterised in that the yokes (28, 29) are assigned to the movable contacts (5a, 5b) and are connected in a friction-locked manner to the switching bridge (4).
7. Switching device according to claim 5, characterised in that the iron plates (25, 26) assigned to the yokes (28, 29) are affixed to stationary components of the switching chamber (1).
8. Switching device according claim 2, characterised in that a second U-shaped yoke (30) is connected in a friction-locked manner to the switching chamber (1) and is used to generate a magnetic opening force.
9. Switching device according to claim 2, whereby a control bus is present at the switching chamber, characterised in that the second U-shaped yoke (30) is connected to the control bus (32).
10. Switching device according to claim 10, characterised in that the control bus (32) consists of iron.
11. Switching device according to claim 9 and 10, characterised in that the control bus (32) and the second yoke (30) comprise one component.
12. Switching device according to claim 2 and 8, characterised in that the first yoke (20) is considerably smaller than the second yoke (30), preferably approximately twice as small in terms of longitudinal dimensions.

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