APPARATUS

The invention is related to an apparatus for electrically interconnecting two laminated multi-phase busbars according to the preamble of claim 1 and a switchgear cabinet including such an apparatus according to claim 9.

Multi-phase busbars are used for example 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 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 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 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.

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 joined 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 a bridging element which has substantially the same laminated sandwich structure as the busbars and which is mounted in a free space provided between the connecting portions of two neighboring busbars.

One problem which arises when using an electrical bridging elements for connecting the lateral connecting portions of two adjoining laminated multi-phase busbars which are also referred to as shipping splits, can be seen in that when connecting the shipping splits of the busbars and bridging element by means of a bolt element which directly extends through a hole in the different laminated layers, a high local pressure is exerted to the outer surface layers of insulating material which cover and sandwich the different conducting layers. These high local pressure is likely to mechanically damage the insulating material, thereby creating cracks in the insulating material which allow ambient air to penetrate into the sandwich of layers. Thus, no gas-tight clamping can be obtained which in turn reduces the long-term stability of the electrical connection.

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 laminated multiphase busbar which allows for an improved long-term stability of the mechanical and electrical connection.

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 switch gear cabinet with a first busbar, a second busbar and a connecting apparatus which overcomes the afore-described problems. This object is achieved by a switchgear cabinet as claimed in claim 9.

Further objects of the invention are included in the sub claims.

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

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

interconnected by a first embodiment of an apparatus according to the present invention,

Fig. 2 is a 3-dimensional view of an apparatus according to the first

embodiment of the present invention,

Fig. 3 is a schematic cross-sectional side view of a second embodiment of the invention, Fig. 4 is a 3-dimensional view of the clamping arrangements used in an

apparatus according to a third embodiment of the invention, and

Fig. 5 is a schematic cross-sectional view of the third embodiment of the

invention mounted at two laminated multi-phase busbars.

As it is shown in Fig. 1 , a first laminated multi-phase busbar 2a and a second laminated multi-phase busbar 2b include a plurality of conducting copper layers 6, wherein alternatively aluminium layers may be provided, and insulating layers 8 which are arranged above and below as well as 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 or the same switch gear cabinet (not shown) project from the insulating layers 8 thereof, so as to form a second lateral connecting portion 4b with second contact surfaces 6b1 to 6b4.

As it can be further seen from Figs. 1 to 5, the apparatus 1 comprises a bridging element 10 which comprises a plurality of laminated insulating layers 8 and conducting layers 6 having contact surfaces which are adapted to contact the associated contact surfaces 6a1 - 6a4; 6b1 - 6b4 of the first and second lateral connecting portions 4a, 4b of the first and second busbars 2a, 2b. To do so, the busbars 2a, 2b and the bridging element 10 may have mating steplike end sections as it shown in Fig. 1.

According to the invention, the apparatus 1 comprises a first clamping arrangement 100a; 200a; 300a with clamping plates 102a1 , 102a2; 202a1 , 202a2; 302a1 , 302a2 which are adapted to mechanically contact and urge associated opposing first outer clamping sections 10a1 , 10a2 of said first busbar 2a and said bridging element 10 towards each other, as it is shown in Figs. 1 to 5. The apparatus 1 further comprises a second clamping arrangement 100b; 200b; 300b with clamping plates 102b1 , 102b2; 202b1 , 202b2; 302b1 , 302b2 which are adapted to mechanically contact and urge associated opposing second outer sections 10b1 , 10b2 of the second busbar 2b and the bridging element 10 towards each other.

In the following description, reference numerals 100 to 130 are related to a first embodiment of the invention which is shown in Figs. 1 and 2, reference numerals 200 to 228 concern a second embodiment which is illustrated in Fig. 3 and reference numerals 302 to 328 concern a third embodiment which is shown in Figs. 4 and 5.

According to the first embodiment of the invention which is shown in Fig. 1 and 2, the first and second clamping arrangement 100a, 100b comprises a pressure transfer element 104a, 104b which has a first end portion 106a, 106b to which a first clamping plate 102a1 , 102b1 is pivotally connected.

The pressure transfer elements 104a, 104b comprise a second end portion 108a, 108b to which a transversal tension bolt 1 10a, 110b is pivotally connected and a third end portion 1 12a, 1 12b which faces away from the bridging element 10, to which a first and a second expansion bolt 114a, 1 14b with threaded end portions are pivotally connected. As it can be seen from Fig. 1 and 2, the first and second pressure transfer elements 104a, 104b are arranged on a first outer side of the bridging element 10 at a distance to each other with the first end portions 106a, 106b facing away from each other.

According to another object of the present invention, the pressure transfer elements 104a, 104b preferably have a substantially triangular cross section with the first, second and third end portions 106a, 106b, 108a, 108b, 1 12a, 112b being tip portions of said triangular cross section.

The expansion bolts 1 14a, 1 14b which extend in a direction parallel to the outer surface of the flat bridging element 10 are coupled to each other by a turnbuckle nut 1 16 and can be extended and retracted by turning the turnbuckle nut 1 16 clock wise or anti clock wise. As it can be further seen from Figs. 1 and 2, each of the transversal tension bolts 1 10a, 1 10b extends through a transversal opening 1 18a, 1 18b which is formed in the bridging element 10 in a direction which is perpendicular to the longitudinal axis of the third expansion bolts 1 14a, 1 14b. Each transversal tension bolt 1 10a, 1 10b is connected to a common lateral pressure beam 120 which extends across a second outer side of the bridging element 10. The pivotable coupling of the expansion bolts 114a, 1 14b and transversal tension bolts 1 10a, 1 10b which are preferably eye bolts, is done by pins which are illustrated in Fig. 2.

The common lateral pressure beam 120 which is made of a stiff and/or rigid material like metal, carries a fixed clamping plate 102a2, 102b2 at each of its opposing end portions which is adapted to contact an associated clamping section 10a1 , 10b1 of the first and second busbar 2a, 2b that is arranged opposite to the afore-mentioned clamping sections 10a2, 10b2 of the bridging element 10. This embodiment of the invention provides for the advantage that the through holes 118a, 1 18b have only to be formed in the laminated layers 4, 6 of the bridging element 10 which significantly reduces the production costs of the bus bars 2a, 2b. Moreover, the clamping forces can easily be adapted to a desired value, in order to account for different embodiments of busbars and clamping plates by simply changing the position where the pins for pivotally connecting the expansion bolts 1 14a, 1 14b and/or transversal tension bolts 1 10a, 1 10b are arranged at the pressure transfer elements 104a, 104. To do so, there may be provided a couple of different holes (not shown) which are spaced apart from each other, into which the pins may be inserted, in order to change the distance of the pivot axes of the bolts relative to each other, respectively.

As it is indicated by dotted lines in Fig. 1 , a reinforcing element 130 may optionally be coupled to the transversal tension bolts 1 10a, 1 10b in a releasable manner, in order to avoid that the free end portions of the bolts 1 10a, 1 10b which extend out of the transversal openings 1 18a, 118b, are bent away from each other upon expanding the expansion bolts 1 14a, 1 14b. The reinforcing element may also be adjustable in length by means of a turnbuckle nut (not shown) as described herein before with regard to the expansion bolts 1 14a, 1 14b.

Moreover, the fixed clamping plates 102a2, 102b2 may also be pivotally mounted to the common lateral pressure beam 120.

According to another object of the present invention, the transversal tension bolts 110a, 110b extend through openings formed in said common lateral pressure beam 120 in a direction which is perpendicular to the first and second outer clamping sections

10a1 , 10b1 of the busbars 2a, 2b and the first and second outer clamping sections 10a2, 10b2 of the bridging element 10 as it is illustrated in Fig. 1 and 2. In this embodiment, each of the transversal tension bolts 1 10a, 1 10b comprises a threaded end portion to which a clamping nut may be screwed after inserting the bolts 1 10a, 110b through the openings 1 18a, 118b when mounting the apparatus 1 to the busbars 2a, 2b. According to another second embodiment of the present invention, which is shown in Fig. 3, each of the first and second clamping arrangements 200a, 200b of the apparatus 1 comprises a first pressure transfer element 204a, 204b and a second pressure element 220a, 220b which is arranged on a side opposite to the bridging element 10. The first pressure transfer element 204a, 204b comprises a first end portion 206a, 206b to which a first clamping plate 202a1 , 202b1 is pivotally connected, a second end portion 208a, 208b to which a connecting rod 209a, 209b is pivotally coupled and a third middle portion 212a, 212b to which a contractible tension bold 210a, 210b is pivotally connected. In the same way, the second pressure transfer element 220a, 220b comprises a first end portion 222a, 222b to which a second clamping plate 202a2, 202b2 is pivotally connected, a second end portion 224a, 224b to which the first connecting rod 209a is pivotally coupled and a third middle portion 226a, 226b to which the contractible tension bold 210a, 210b is connected.

This second embodiment of the invention provides for the advantage that due to the lever-type construction of the clamping arrangement 200a, 220b the clamping pressure can be easily adjusted to a desired value. Moreover, due to the short length and direct coupling of the contractible tension bolts 210a, 210b and the connecting rods 209a, 209b to the first and second pressure transfer elements 204a, 204b and 220a, 220b, the backlash of the clamping arrangement is minimized.

According to another aspect of the invention, the connecting rod 209a of the first clamping arrangement 200a and/or the connecting rod 209b of the second clamping arrangement 200b may extend through an opening in the middle section 226a, 226b of the second pressure transfer element 220a, 220b and comprises a threaded end portion to which a clamping nut 228a, 228b may be screwed which abuts the outer surface of the second pressure transfer element 220a, 220b, respectively, which faces away from the bridging element 10. This provides for the advantage of a compact design and a further reduction of backlash.

In a third embodiment of the invention which is shown in Figs. 4 and 5, each of the first and second clamping arrangement 300a, 300b of the apparatus 1 includes a pair of cooperating clamping plates 302a1 , 302a2, 302b1 , 302b2. Each clamping plate 302a1 , 302a2, 302b1 , 302b2 comprises an even base plate 303a, 303b for contacting an associated outer clamping section 10a1 , 10a2 10b1 ,10b2, respectively, and a dome shaped pressure transfer element 304a, 304b, the base of which abuts the even base plate 303a, 303b. As it can be seen from Fig. 4 and 5, a through hole is formed in the bridging element 10 and/or in the first and second lateral connecting portions 4a, 4b which matches with the through holes in the even base plates 303a, 303b and the dome-shaped pressure transfer elements 304a, 304b, so as to receive an associated first and second transversal tension bolt 310a, 310b, respectively. The first and second transversal tension bolts 310a, 310b comprise a threaded end portion to which a screw nut 328a, 328b can be screwed which abuts an outer surface of the first and second dome-shaped pressure transfer elements 304a, 304b.

By rotating the first and second transversal tension bolt 310a, 310b or tightening the screw nuts 328a, 328b, the outer clamping section 10a1 , 10a2 10b1 and 10b2 can be pressed against each other with a clamping force which is evenly distributed into the associated even base plates 303a, 303b by the specific dome-shaped form of the abutting dome-shaped pressure transfer element 304a, 304b. The dome-shaped pressure transfer elements 304a, 304b may also have the shape of a truncated cone or a truncated pyramid.

According to yet another object of the present invention which is not shown in the drawings, a switch gear cabinet which includes a first and a second laminated multi phase busbar 2a, 2b is characterized in that the busbars 2a, 2b are electrically connected by an apparatus 1 as it is described herein before.

Listing of reference numerals

1 apparatus

2a first laminated multi-phase busbar

2b second laminated multi-phase busbar

4a first lateral connecting portion

4b second lateral connecting portion

6 conducting layers of first and second busbar

6a1 -6a4 first contact surfaces of conducting layers

6b1 -6b4 second contact surfaces of conducting layers

8 insulating layers of first and second busbar

10 bridging element

10a1 first outer clamping section at first busbar

10a2 first outer clamping section at bridging element

10b1 second outer clamping section at second busbar

10b2 second outer clamping section at bridging element

100a first clamping arrangement of first embodiment

100b second clamping arrangement of first embodiment

102a1 , 102a2, clamping plates of first clamping arrangement

102b1 , 102b2, clamping plates of second clamping arrangement

104a, 104b pressure transfer element

106a, 106b first end portion of pressure transfer element

108a, 108b second end portion of pressure transfer element

1 10a, 1 10b transversal tension bolt

1 12a, 1 12b third end portion of pressure transfer element

1 14a, 1 14b expansion bolt

1 1 6 turnbuckle nut interconnecting expansion bolts

1 18a, 1 18b transversal opening

120 common lateral pressure beam

130 reinforcing element 200a first clamping arrangement of second embodiment

200b second clamping arrangement of second embodiment

202a1 , 202a2, clamping plates of first clamping arrangement

202b1 , 202b2, clamping plates of second clamping arrangement

204a, 204b first pressure transfer element at first and second clamping element

206a, 206b first end portion at first pressure transfer element

208a, 208b second end portion at first pressure transfer element

209a, 209b connecting rod

210a, 210b contractible tension bolt

212a, 212b third intermediate portion of first pressure transfer element 220a, 220b second pressure transfer element at first and second clamping element

222a, 222b first end portion of second pressure transfer element

224a, 224b second end portion of second pressure transfer element

226a, 226b third intermediate portion of second pressure transfer element 228a, 228b nut element for tensioning connecting rod

300a first clamping arrangement of third embodiment

300b second clamping arrangement of third embodiment

302a1 , 302a2 clamping plates of first clamping arrangement

302b1 , 302b2 clamping plates of second clamping arrangement

303a, 303b base plate of clamping plate

304a, 304b dome-shaped pressure transfer element

310a first transversal tension bolt

310b second transversal tension bolt

328a, 328b screw nut