ENERGY AND METHOD OF MANUFACTURING THE SAME

The invention is related to a multi-phase busbar and a method of manufacturing the same according to the preamble of claims 1 and 10.

Multi-phase busbars are used in switchboards and/or switchgears in particular low voltage switchgears, to conduct and distribute alternating electrical current to different electrical devices which are usually installed in switch gear cabinets. In order to provide for the possibility to conduct all three phases or even more phases of an alternating current in a single busbar, 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, are arranged that 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 laminated busbar has the advantage that it is compact and does not tend to delaminate due to repellant forces which are generated by the alternating electric currents that 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). One problem of the busbars as described in DE 10 2005 015 945 B4 are the costs involved in the lamination process itself in which the different layers are bond to each other by means of a liquid resin, like epoxy resin, which is applied to the upper and lower side of each layer and cured afterwards. As the laminating resins used for the laminating process are usually toxic and are said to cause allergic reactions, specific safety precautions for the staff are required in the production process which significantly raise the production costs.

Accordingly, it is a problem of the present invention to provide for a multi-phase busbar which can be manufactured at reduced efforts and costs without the extensive application of a liquid resin to each layer for bonding the layers to each other.

This problem is solved by a multi-phase busbar and a method of manufacturing the same as claimed in claims 1 and 10.

Further objects of the present invention are included in the dependent claims.

The invention has the following technical advantages:

^■ High reliability as all copper plates are coated before the resin is cast around the pins. No additional machining or cover/coating on the pins and shipping splits are required.

^■ High flexibility on the arrangement of the pins as only the area around the pins is casted and no complex mold is required.

^■ The busbar according to the inventions provides for the same size and loss reduction as a conventionally laminated busbar,

^■ The combined layer and casting concept of the invention allows a highly

automated processing of multi-phase busbars

Moreover, the invention has the following economical advantages:

^■ Reduced handling steps as no complex mold is required. Especially, no tight sealing around the pins and shipping split areas are needed as the local clamping proved to be sufficient.

^■ The casting can be performed without the use of vacuum if an appropriate resin is used.

^■ No cleaning of the mold is required.

^■ Reduced tooling costs as the machined/molded area around the pins itself is used as a mold.

^■ In general lower production costs and faster assembly of the busbar compared to currently used systems.

Accordingly, the claimed invention relates to a multi-phase busbar for conducting electric energy, comprising a first conducting layer made of a sheet metal, a first conducting pin mounted to said first conducting layer which extends in a direction preferably perpendicular to the first conducting layer, a first insulating layer of a rigid insulating material arranged on said first conducting layer, said first insulating layer having an opening through which the first conducting pin projects, a second conducting layer made of a sheet metal which is coated with an electrically insulating material, said second conducting layer comprising a first pinhole through which said first conducting pin projects and a second conducting pin which extends in a direction parallel to said first conducting pin, wherein said opening in said first insulating layer and said first pinhole in said second conducting layer define a common recess through which said first conducting pin projects, said recess being filled with a resin which forms a material bridge between the first conducting layer and the second conducting layer, said material bridge mechanically clamping said first conducting layer, said first rigid insulating layer and said second conducting layer together.

In a further embodiment of said invention at least one conductive layer is coated with an electrically insulating material, wherein the coating comprises a thickness between 0.1 and 0.5 mm and/or includes an epoxy resin and/or wherein the resin is a thermosetting resin, and/or that the resin includes a photoinitiator. In another embodiment one or more of the conducting layers are copper or aluminium layers and/or the layers of rigid insulating material comprises and/or is made of fiber reinforced plastics or SMC material or polyester resin glass mats, like for example GPO-3 or UP GM 203 or HM 2471 , and/or the layers of rigid insulating material have the shape of an elongated cuboid

In a further embodiment a second insulating layer of a rigid insulating material is arranged on said second conducting layer, said second layer of rigid insulating material having an opening which matches said first pinhole, said first pinhole in said second conducting layer and said openings in said first and second layers of insulating material defining a common recess in which the first and the second conducting pin are located and which is filled with resin forming a material bridge which mechanically clamps said first and second conducting layers and said first and second rigid insulating layers together.

Furthermore, in another embodiment a third and a fourth layer of a conducting material and a third layer of a rigid insulating material are arranged above each other on said second layer of rigid insulating material, wherein said third conducting layer comprises a first and second pinhole, said fourth conducting layer comprises a first, second and third pinhole and said third layer of rigid insulating material comprises an opening, wherein the first, second and third pinholes in the conducting layers and the openings in the first, second and third layers of rigid insulating material are in communication with each other and form a common recess in which the first, second and third conducting pins are located, said common recess being filled with a resin forming a material bridge which mechanically clamps said conducting layers and said layers of rigid insulating material. Moreover, in a further embodiment a fourth layer of rigid insulating material having an opening which matches the first second and third pinholes in said second and third and fourth conducting layers are arranged on said fourth insulating layer, said opening communicating with said openings in said first, second and third layer of insulating material and said pinholes in said conducting layers, thereby forming a common recess which is filled with a resin which forms a material bridge that mechanically clamps the stack of conducting layers and layers of rigid insulating together.

In a further embodiment at least one layer of rigid insulating material comprises thickness variations (washer, edge cover, shipping split) and/or may be made out of one piece by use of SMC (sheet moulding component plastics) or prepreg, wherein in case of flat plates GPO-3 parts may be glued to each other.

Furthermore, at least the first pinholes in the second, third and fourth conducting layers and/or the openings in the first and/or second and/or third layer of insulating material may be aligned with each other.

In another embodiment, the at least one opening formed in the first layer of rigid insulating material comprises a continues edge which surrounds at least the first and the second conducting pins and/or the at least one opening in the first layer of rigid insulating material comprises an area which is larger, preferably at least four times as large as the area of the cross section of the first pinhole.

Furthermore, the first and second and/or the third layers of rigid insulating material may be substantially identical. In another embodiment at least one of the layers of rigid insulating material may comprise electrically conductive surface layers made of sheet metal, preferably copper or aluminium, said surface layers in particular comprising a thickness between 0.01 mm to 0.5 mm. In a further embodiment the end portions of conducting layers comprise conducting edge portions in which no insulating coating is applied to the sheet metal.

In a further embodiment the respective conducting pin is built as solid or hollow cylinder or cup, which cylinder or cup when mounted is in electrical contact with one conductive layer of the busbar, wherein the conducting pin is detachably and/or mechanically attached to and/or mounted on, in particular by screwing to or clamping, the multiphase bus and in particular at one conductive layer and/or the base layer.

In a further embodiment more than one conducting pin, in particular three or four or five or more pins, are electrically connected to and detachably and/or mechanically connected to one conducting layer and in particular the same conducting layer. In a further embodiment, the conducting pins may be arranged in groups in a line, in particular within a group in vertical or horizontal arrangement, or may be arranged in an array.

In another embodiment the respective conducting pin may comprise further mounting means, like internal screw threads or external screw threads, in particular for the attachment of switchgear modules, in particular low voltage switchgear modules, electrical devices as well as for the attachment to the bus bar.

Pursuant to yet another aspect of the present invention, a multi-phase busbar as described herein before is arranged in a switchboard cabinet for distributing electric energy to a plurality of electric or electronic devices which are contained in or provided outside the switchboard cabinet, like in particular low voltage switchgear modules.

In this respect, a very efficient, in particular cost efficient, and compact design of the switchboard cabinet may be obtained when the busbar according to the invention forms a rear panel of the switchboard cabinet, or at least a part of the rear panel of the switch board cabinet.

Further advantageously a section or cabinet, comprising a housing, whereas the housing comprises at least a rear side, comprises at least one multi-phase busbar as described above which is arranged on the rear side of the section or cabinet and/ or forms at least a part of a back wall of the housing. Hereby is ensured an easy arrangement of modules and devices, especially withdrawable modules or plug-in modules within a section or cabinet. The modules can be plugged on the conducting pins and the busbar can be designed as a replacement part. The busbar can be designed according to the types and to the number of modules to be used.

Advantageously several multi-phase busbars may be arranged on the rear side of the section or cabinet and/ or form at least a part of a back wall of the housing, whereas the busbars are on top of each other and whereas each busbar is formed as a band. Thereby a laminated main busbar system can be located at the back side of a low voltage switchgear cabinet or section. The multi-phase busbar system can be split in four rows of horizontal laminated busbars of the same size and cross section.

Furthermore a method of manufacturing a multi-phase busbar according to any of the preceding embodiments is claimed comprising the following method steps:

- forming a stack including a) a first conducting layer b) first layer of a rigid insulating material loosely arranged on said first conducting layer,

c) a second conducting layer loosely arranged on said first layer of rigid

insulating material and

d) a second insulating layer loosely arranged on said second conducting layer, wherein said second conducting layer comprises a first pin hole and said first conducting layer comprises a first conducting pin projecting through said first pinhole and a second conducting pin arranged at a distance to said first conducting pin and extending in a direction parallel to said first conducting pin, and

wherein said first layer of a rigid insulating material comprises an opening having a larger size than said first pinhole and extending between said first and second conducting layers so as to communicate with said first pinhole and form a common recess, pressing said first and second conducting layers against each other so as to mechanically clamp the first layer of rigid insulating material between said conducting layers, filling up said common recess with a curable resin and curing said resin while pressing said first and second conducting layers against each other.

The invention is hereinafter described with reference to the accompanying drawings and following description.

In the drawings is a schematic view of a first uncoated conducting layer, is a schematic view of the conducting layer of Fig. 1 after positioning a first layer of rigid insulating material on the electrically conducting surface,

Fig. 3 is a schematic view of the busbar of Fig. 2 after positioning second

conducting layer and a second layer of rigid insulating material on the second conducting layer and filling up the common recess through with curable resin, to provide a minimum-configuration of a busbar having only two conducting layers,

Fig. 4 is a schematic view of the busbar of Fig. 3 after arranging a third and fourth conducting layer and a second, third and fourth intermediate layer of rigid insulating material on the second conducting layer according to another preferred embodiment of the invention while pressing the layers together and casting resin into the common recesses around the first conducting pins,

Fig. 5 is a schematic view of the final product of a busbar of Fig. 4 after curing the resin.

As it is shown in Fig. 1 , a multi-phase busbar 1 for conducting electric energy, comprises a first conducting layer 4a which is made of a sheet metal, preferably copper or aluminium, which can have a thickness of 0.5 to 5 mm or even more. The first conducting layer 4a comprises at least one first conducting pin 1 6a, which extends in a direction perpendicular to the first conducting layer 4a and which is either integrally formed with the conducting layer 4a when manufacturing the same or which is soldered or mechanically attached to the sheet metal by screwing or clamping. Optionally a coating of an electrically insulating material , preferably epoxy resin may be applied to the first conducting pins 1 6a except at the contacting portions at the tops of the first conducting pins 1 6a which in the final product serves for electrically connecting the first conducting layer 4a to shipping splits and to electric devices (not shown).

On the first conducting layer 4a, a first insulating layer 6a of a ridged insulating material is loosely positioned as it is shown in Fig. 2. The layer 6a is preferably a machined GPO-3 plate material or an other known composite material which is composed of reinforcing fibers and a cured resin. The first insulating layer 6a which may have a thickness of 1 mm to 5 mm or more depending on the specific operational purpose and design of the busbar, comprises an opening 10 which extends at least around the area of the first conducting pin 1 6a and preferably also underneath the area, where the second conducting pin 1 6b is positioned when positioning a second conducting layer 4b on the first insulating layer 6a as it is shown in Fig. 3. As it is further indicated by dashed lines in Fig. 4, further openings 10 may be formed in the first insulating layer 6a of rigid insulating material in the sections where further first and second conducting pins 1 6a, 16b are mounted to the first conducting layers 4a, 4b, so that there may be formed four or even more of such openings 10 each of which is having a continues edge 10a which surrounds at least the first and the second conducting pins 1 6a, 16b.

As it can further be seen from Fig. 4, the second conducting layer 4b comprises a first pinhole 14a around each of the conducting pins 1 6a through which the first conducting pins 1 6a project, respectively. This first pinhole 14a communicates with the opening 10 in the first insulating layer 6a and thereby defines a common recess 15 through which the first conducting pins 1 6a project. As a next step for producing a multi-phase busbar 1 having two conducting layers 4a, 4b which represents the minimum configuration of a busbar according to the present invention, the entire stack including the two conducting layers 4a, 4b and also the first insulating layer 6a is aligned. This alignment may be done by means of a mask (not shown) which comprises holes at the positions where the first and second conducting pins 1 6a, 1 6b are located, and stops (not shown) against which the edges of the layers may abut.

In a next step the common recesses 15 are filled up with a curable resin 17 which is injected into the first pinholes 1 6a and penetrates into the openings 10, as it will be described hereinafter with reference to Figs 6a and 6b, in which the preferred embodiment of a busbar 1 is shown which comprises four conducting layers 4a to 4d.

While filling the recesses 15 with the curable resin 17, pressure is applied to the upper and lower layers of the stack as it is indicated by arrows F in Figs. 6a and 6b. The pressure F which is preferably applied as a clamping force by vises (not shown) avoids that the resin 17 penetrates from the common recesses 15 into gaps which may be formed between the different layers. The resin 17 may be a 2-component resin formulation which is prepared by mixing the two components right before filling up the common recesses 15, but may also be a thermosetting resin. The resin 17 may optionally include a photoinitiator, in particular a UV-initiator which can be activated by applying UV-light from a light source (not shown) in order to provide for an initial bonding of the layers 4a, 4b and 6a prior to a final curing of the resin. This advantageously allows the positioning masks to be removed right after the initial UV-curing of the resin in the first pinholes 14a which can then be used for the production of a next busbar 1 .

After the curing of the resin 17, which may also be accelerated by putting the stack into an oven, the resin 17 in the common recesses 15 forms a material bridge 12 between the first conducting layer 4a, the first insulating layer 6a and the second conducting layer 4b which mechanically clamps said first conducting layer 4a, said first rigid insulating layer 6a and said second conducting 4b layer together. According to another embodiment of a busbar 1 having two conducting layers 4a, 4b, a second insulating layer 6b of a ridged insulating material is arranged on the second conducting layer 4b, as it is shown in Fig. 3. The second ridged insulating layer 6 is preferably identical to the first rigid insulating layer 6a and comprises an opening 10 which surrounds the first and second conducting pins 1 6a, 1 6b and matches the first pinhole 14a, so that the first pinhole 14a in the second conducting layer 4b and the openings 10 in the first rigid insulating layers 6a, 6b are in fluid communication and define a common recess 15 in which the first and the second conducting pins 1 6a, 16b project in parallel to each other.

In order to permanently clamp the four layers 4a, 4b, 6a and 6b together, the stack of loosely superposed layers is aligned and mechanically pressed together while filling the liquid curable resin 17 into the common recess 15. As it can be seen from Fig. 3, the liquid resin 17 is fed into the common recess 15 until the entire opening 10 in the second rigid insulating layer 6b which forms a part of the common recess 15 is entirely filled up with resin. After the curing of the resin, the resin in the filled up recess 10 also forms part of the material bridge 12 which advantageously comprises an enlarged clamping area.

According to the preferred embodiment of a busbar 1 which comprises altogether 4 electrically conducting layers 4a, 4b, 4c and 4d, a third and a fourth layer 4c, 4d of a conducting material and a third layer 6c of a rigid insulating material are arranged above each other on the second layer 6b of rigid insulating material, as it is shown in Fig. 4. The third conducting layer 4c comprises a first and second pinhole 14a, 14b, whereas the fourth conducting layer comprises a first, second and third pinhole 14a, 14b, 14c, in the centers of which the three conducting pins 1 6a to 1 6c are preferably centrally arranged, respectively. The third layer 6c of rigid material which is preferably identical to the other layers 6a and 6b comprises an opening 10 (indicated in dashed lines) which is in fluid communication with the first, second and third pinholes 14 in the conducting layers 4b to 4d as well as the openings 10 in the first, second and third layers 6a 6b, 6c of rigid insulating material and forms part of a common recess 15 in which the first, second and third conducting pins 1 6a, 1 6b and 16c project. In the same way as described herein before the stack of layers is aligned and clamped together before filling in the liquid resin 17. The resin 17 is preferably injected into the openings 14a which extend through all layers except the lower conducting layer 4a. After the curing of the resin which may also include

reinforcing fibers (not shown) the hardened resin forms a material bridge 12 which mechanically clamps the conducting layers 4a, 4b and the layers 6a to 6c of rigid insulating material together as it is shown in Fig. 5.

As the applicant has found, the clamping of the layers by the material bridges 12 of cured resin also increase the shear resistance of the stack in a lateral direction, that is in the plane of the layers, due to the frictional forces generated. This in turn reduces the danger of a delamination of the busbars 1 by the repellant magnetic forces which are generated in case of a short circuit.

According to an even more sophisticated embodiment of the invention which is shown in Fig. 6b and 7b, a fourth layer of rigid insulating material 6d is arranged on said fourth insulating layer 4d. The fourth insulating layer 4d comprises an opening 10 which matches the first second and third pinholes 14a, 14b and 14c in said first second and third conducting layers 4a to 4c and is in fluid communication with the openings 10 which are formed in the first, second and third layers 6a to 6c of rigid insulating material and the pinholes 14a to 14c in the conducting layers 4a to 4c. The opening 10 in the fourth layer 6d of rigid insulating material forms part of a common recess 15 which is filled up with a curable resin as shown in Fig. 6b, in order to generate a material bridge 12 which mechanically clamps the sandwich of conducting layers 4a to 4d and rigid insulating layers 6a to 6d in the final busbar 1 as it is shown in Fig. 5.

In the afore-described embodiments of the invention, the layers 4 and 6 are advantageously mechanically attached to each other by the material bridges of the cured resin 12 only, without employing additional adhesives between the layers. In the preferred embodiments of the invention, the openings 10 in the first layer 6a and/or second layer 6b and/or third layer 6c and/or fourth layer 6d of rigid insulating material cover an area which is larger, preferably at least four times as large, as the area which is covered by the cross section of the first, second and third pinhole 14 a to 14c which are preferably identical in shape. By means of this, a toothing interaction of the material bridges 12 is generated which further increases the mechanical stability of the busbar 1 .

In a further embodiment additional adhesives may be applied between the layers to further increase the mechanical stability and to facilitate the production process.

Furthermore, all layers and insulating materials or sheets may be fixed and/ or coated by any possible mechanical or chemical method, especially with or without cast- ing, with or without glueing or with or without epoxy coating.

A module described here may be embodied as a withdrawable module, a plug-in module or a fixed module or fixed device. The scope of the respective claim covers all the aforementioned embodiments of a module.

Listing of reference numerals

busbar

4a first conducting layer

4b second conducting layer

4c third conducting layer

4d fourth conducting layer

6a first intermediate layer

6b second intermediate layer

6c third intermediate layer

6d fourth intermediate layer opening

a continuous edge of opening material bridges

a first pinholes

b second pinholes

c third pinholes

common recess

a first conducting pinsb second conducting pinsc third conducting pinsd fourth conducting pins

resin

compressive force