SUCH AN APPARATUS

The invention is related to an apparatus for electrically interconnecting two laminated multi-phase busbars, in particular for low voltage or medium voltage installations, according to the preamble of claim 1 and a switchboard arrangement including such an apparatus according to claim 10.

Multi-phase busbars are used in low voltage switchgears to conduct and distribute alternating electrical current to different electrical devices which are installed in switch gear cabinets. In order to conduct all three or even more phases of an alternating current in a single busbar, laminated multi-phase busbars have been developed which comprise a base layer and a cover layer of electrically insulating material between which two or more layers of conducting sheet metal, in particular copper sheets, are arranged which are electrically insulated from each other by means of insulating intermediate layers.

An afore-described busbar in which the different layers are laminated to each other by means of liquid resin is described in DE 10 2005 015 945 B4 of the applicant. The described laminated multi-phase busbar has the advantage that it has a compact design and does not tend to delaminate due to repellant forces which are generated by the alternating electric currents which are conducted in the different conducting layers for each phase and which in case of a short circuit can be in the range of several thousand ampere (kA).

In order to supply electric energy from a power source to a laminated multi-phase busbar, it is known to remove the insulating material in a lateral section of the sandwich of layers and expand the uncoated conducting layers which project from the intermediate insulating layers, so as to provide for four lateral connecting portions, that is one for each phase and one for protective earth, to which the terminals of the electric power source can be connected.

The lateral connecting portions are also used to provide an electrical connection between different busbars in two or more switch gear cabinets which are arranged in a row, in order to efficiently feed the electric energy from a power source to the busbars of a plurality of interconnected switchgear cabinets. Moreover, the lateral connecting portions serve to reduce the lengths of laminated busbars, as long busbars for large switchgear cabinets can be spilt up into a plurality of shorter busbar sections which are joint at the customer site, in order to ease handling and reduce transportation costs.

The electrical connection of the conducting layers of one busbar or busbar section to the conducting layers of an adjoining busbar or bus bar section at the lateral connecting portions is usually done by means of stiff joints or stiff bridging elements each of which has two terminal members which are interconnected by a stiff bridging element and which are clamped to the contact sections of the conducting layers which are to be electrically connected. The conducting layers and the contact sections provided thereat, are preferably made of copper or aluminium and may have a thickness in the range between 0.5 and 5.0 mm or more.

One problem which arises when using a stiff electrical connection between the lateral connecting portions of two adjoining laminated multi-phase busbars which are also referred to as shipping splits, can be seen in that the clamping arrangement for firmly and securely clamping the terminal members of the connecting devices to the lateral connecting portions leads to a compression of the end portions of the busbar. This in turn may lead to a compression of the insulating material which is arranged between the electrically conducting layers.

Another problem which occurs when electrically connecting the lateral connecting portions of two adjoining busbar section to each other by a stiff mechanical connection can be seen in that manufacturing tolerances and assembly tolerances as well as a thermal expansion of the joined busbars due to different electric loads attached to the system may result in the occurrence of internal strain in the material which increases the risk of a mechanical and electrical failure of the busbars. Moreover, a further problem of a rigid connection between two busbars is the occurrence of a creeping of the polymeric or composite insulating material or even the creeping of the adhesive which provides for the bonding of the different layers of a laminated busbar.

However, even another problem which arises when electrically connecting the busbars of two neighboring switch gear cabinets can be seen in that the mechanical vibrations of the different layers of a busbar which are generated in case of a short circuit in one switch gear cabinet are mechanically transmitted via a stiff bridging element to the adjoining busbar in the neighboring switch gear cabinet, where the vibrations may cause a mechanical damage or even a delamination of the different layers, too.

Accordingly, it is an object of the present invention to provide an apparatus for interconnecting the lateral connecting portions of a first and a second adjoining multiphase laminated busbar which overcomes the afore-described problems.

This object is achieved by an apparatus as claimed in claim 1.

Moreover, it is a further object of the present invention to provide a switchboard arrangement with a first busbar, a second busbar and a connecting apparatus which overcomes the afore-described problems. This object is achieved by a switchboard arrangement as claimed in claim 10

The invention is hereinafter described with reference to the accompanying drawings. In the drawings

Fig. 1 is schematic top view of a first and a second busbar which are

interconnected by an apparatus of the invention,

Fig. 2 is 3 dimensional sectional view of an apparatus of the present invention,

Fig. 3 is a cross sectional view of the apparatus and connected busbars of

Figs. 1 and 2, and Fig. 4 is a cross sectional view in a lateral direction of the apparatus of Fig 1 in a plane intersecting the bolt elements.

As it is shown in Figs. 1 to 4, a first laminated multi-phase busbar 2a and a second multi-phase laminated busbar 2b include a plurality of conducting copper layers 6 and intermediate insulating layers 8 which are arranged between the conducting layers 6. The conducting layers 6 of the first laminated multi-phase busbar 2a which may be accommodated in a first switch gear cabinet (not shown) project from the insulating layers 8 and form a first lateral connecting portion 4a with first contact surfaces 6a1 to 6a4. In the same way, the conducting layers 6 of the second laminated multi-phase busbar 2b which may be accommodated in a second switch gear cabinet (not shown) project from the intermediate insulating layers 8 thereof, so as to form a second lateral connecting portion 4b with second contact surfaces 6b1 to 6b4.

As it is further shown in Fig. 3, an apparatus 1 for electrically connecting the first laminated multi-phase busbar 2a with the second multi-phase laminated busbar 2b comprises a first clamping arrangement 10a which includes a plurality of first clamping elements 1 1 a and a plurality of first terminal members 10a1 to 10a4 which are adapted to be clamped to the first contact surfaces 6a1 to 6a4 of the lateral connecting portion 4a of the first bus bar 2a by means of the first clamping elements 11 a. The apparatus 1 further comprises a second clamping arrangement 10b which includes a plurality of second clamping elements 1 1 b and a plurality of second terminal members 10b1 to 10b4 which are adapted to be clamped to the second contact surfaces 6b1 to 6b4 of the second lateral connecting portion 4b of the second busbar 2b by means of the second clamping elements 1 1 b.

As it can further be seen form Figs. 1 and 3, each of the first terminal members 10a1 to 10a4 is electrically interconnected with an associated second terminal member 10b1 to 10b4 by an electrically conducting bridging element 12.1 to 12.4. In this respect, the first terminal member 10a1 and the associated second terminal member 10b1 are connected to the bridging element 12.1 which bridges the upper most conducting layers 6 of both busbars 2a, 2b, whereas the first terminal member 10a2 and the associated second terminal member 10b2 are connected to the bridging element 12.2 which bridges the conducting layers 6 that are arranged below the upper most conducting layer 6 of Fig. 3. The same applies to the first and second terminal members 10a3, 10b3 and 10a4, 10b4 and the associated bridging elements 12.3, 12.4 for electrically interconnecting the two lower conducting layers 6 of the busbars 2a, 2b, respectively.

According to Figs. 2 and 3, each of the bridging elements 12.1 to 12.4 comprises a core 12a of a flat flexible conducting material, which is covered an electrically insulating coating 12b. The coating 12b may be a flexible insulating polymer as it is known from electric cables.

In the preferred embodiment of the invention, the core 12a is a flat strip of braided copper to which a respective pair of first and second terminal members 10a1 , 10b1 ; 10a2, 10b2; 10a3, 10b3 and 10a4; 10b4 is attached at opposing sides, so as to form a corresponding bridging element 12.1 to 12.2 for bridging the associated conducting layers 6 of the two busbars 2a and 2b, which are configured to conduct and distribute the three electric phases and protective earth of an alternating electric current in two interconnected switch gear cabinets (not shown).

According to an alternative embodiment of the invention which is not shown in the drawings, the core 12a of each bridging element 12.1 to 12.4 may be a multi-layer stack of thin copper sheets which are arranged relatively movable to each other on top of each other. In the same way as described herein before with regard to the core 12 of braided copper, the pairs of first and second terminal members 10a1 , 10b1 ; 10a2, 10b2; 10a3, 10b3 and 10a4; 10b4 are attached to the end portions of the multi-layer stack of copper sheets at opposing sides thereof.

As it can be further seen from Figs. 1 and 2, the plurality of first terminal members 10a1 to 10a10 and first clamping elements 1 1 a is arranged in a first housing 16a, whereas the second clamping elements 1 1 b and terminal members 10b1 to 10b4 are accommodated in a second housing 16b of the apparatus 1. The housings are preferably formed of a rigid electrically insulating material, like fiber reinforced resin. In Figs. 1 and 2 it further shown that the housings 16a, 16b may be formed of different housing elements, which may include central T-shaped support elements 17 which are arranged above each other in different layers. The bridging elements 12.1 to 12.4 extend between the first and second housing 16a, 16b, so that the apparatus 1 can be handled and installed as one unit if desired.

As it can best seen from Figs. 2 and 3, the bridging elements 12.1 to 12.4 which connect the corresponding conducting layers 6 of the first and second busbars 2a, 2b are arranged in different layers or levels which are spaced apart from each other at substantially equal distances. The levels extend preferably between two of the afore mentioned T-shaped support elements 17 of the housings 16a, 16b.

In order to provide for an increased mechanical flexibility of the apparatus 1 in the vertical direction (which is indicated by arrow 22 in Fig. 2 and hereinafter referred to as the lateral direction of the busbar) when mounting the first and second busbars 2a, 2b in a vertical plane, the core 12a of each bridging element 12.1 to 12.4 comprises a plurality of core sections which are spaced apart from each other by e.g. 5 mm to 5 cm or more, in order to allow for a movement of the lateral portions 4a, 4b of the first and second busbar 2a, 2b relative to each other, as it is shown in Fig. 1 and 2.

From Fig. 3, it can be taken that one of the first terminal members 10a1 to 10a4 of the first clamping arrangement 10a and a corresponding one of the second terminal members 10b1 to 10b4 of the second clamping arrangement 10b are attached to a core section at opposing ends. In the preferred embodiment of the invention, the core sections correspond to the flat strips of braided copper or the multi-layer stack of copper sheets. Alternatively, instead of copper aluminium may be used also.

From Fig. 3 it can further be seen that the electrically conducting bridging elements 12.1 to 12.4 or its core sections may also be spaced apart from each other in a direction perpendicular to the lateral direction, preferably in equal distances. In order to further allow for a horizontal movement of the lateral end portions 4a, 4b of two busbars 2a, 2b which are interconnected by an apparatus 1 , the planes in which the different core sections of each of the bridging elements 12.1 to 12.4 extend can also be slightly curved or bend, as it is indicated in Fig. 2 and 3. In order to provide for a quick and easy clamping installation of the apparatus 1 , the first clamping elements 1 1 a and/or the second clamping elements 1 1 b may be biased in groups by an associated bolt element 18 which extends in a direction perpendicular to the contact surfaces of the afore mentioned first terminal members 10a1 to 10a4 and/or second terminal members 10b1 to 10b4, respectively, as it can be best seen from Figs. 2 and 3.

In order to provide for a sufficient electrical insulation of the conducting first terminal members 10a1 to 10a4 and second terminal members 10b1 to 10 b4, preferably each of the bolt elements 18 extends through a plurality of sleeves 20 which are aligned to each other in the first clamping arrangement 10a and in the second clamping arrangement 10b, respectively. In order to allow for the bolts 18 to be inserted into the sleeves 20, a plurality of holes may be formed in the housings 16a, 16b and in each clamping element 1 1 a, 11 b, through which the each bolt 18 extends in the vertical direction. Each of the sleeves 20 is preferably made of an insulating material and comprises a shaft which extends through a hole in an abutting contacting element and a collar which contacts an adjoining surface of a clamping element 1 1 a, 1 1 b and a T- shaped support element 17 of the housing 16a, 16b, respectively. In order to tighten the bolts 18 and bias the clamping elements 11 a, 1 1 b with a resilient force which forces the clamping elements against the terminal members 10a1 to 10a4 and 10b1 to 10b4, each bolt 18 may be provided with a threaded end portion to which a nut 18a can be screwed, as it is indicated in Fig. 3.

As it is further shown in Fig. 2 and 3, there may further be arranged ring-shaped spacer elements 19 of an electrically insulating material on the side of the clamping elements 11 a, 1 1 b which is opposite to the collar of the sleeves 20. As it is shown in Fig. 3 and 4, the shafts of the sleeves 20 have an outer diameter which is smaller than the inner diameter of the ring-shaped spacer elements 19, so that the shaft of the sleeves 20 is received in the spacer elements 19 in a sliding manner, so as to allow for a reduction of the distance between the clamping elements 1 1 a, 1 1 b and the T-shaped support elements 17 of the housing when tightening the nuts 18a. Listing of reference numerals

1 apparatus

2a first multi-phase laminated busbar

2b second multi-phase laminated busbar

4a first lateral connecting portion

4b second lateral connecting portion

6 conducting layers of first and second busbar

6.1 first contact surfaces of conducting layers

6.2 second contact surfaces of conducting layers

8 intermediate insulating layers of first and second busbar

10a first clamping arrangement

10b second clampig arrangement

10a1 - 10a4 first terminal members

10b1 - second terminal member

10b4

11 a first clamping elements

11 b second clamping elementes

12.1 - 12.4 electrically conducting bridging element

12a core of bridging elements

12b electrically insulating coating

16a first terminal member housing

16b second terminal member housing

17 T-shaped support elements

18 bolt element

18a nut

10 ring shaped spacer

20 sleeves

22 arrow indicating lateral direction