Impedance balancing in multi conductor system

Abstract

The invention relates to a multi conductor system comprising at least two conductors. At least one conductor of the at least two conductors comprising multiple grooves forming multiple branches, wherein the multiple branches are designed to facilitate sharing of a phase current, among the multiple branches, when said conductor is conducting the phase current. The design of the multiple branches furthermore is configured to maintain the sharing of said phase current when an electromagnetic coupling effect from an additional conductor of said at least two conductors impacts the conductor.

Description

IMPEDANCE BALANCING IN MULTI CONDUCTOR SYSTEMField of the invention

[0001] The invention relates to a multi conductor system with impedance balancing.Background of the invention

[0002] In the technical field of current conductors, the design of the, typically copper or aluminium, conductors have typically been spheric, square or rectangular, twisted or braided. The different designs have been chosen for the application in which current has to be conducted from one component to the other. Uninsulated solid square busbars have been used in high power electric cabinets to conduct +1000 A of current. Insulated cables, having twisted or solid conductors, have been used to supply such cabinets. Braided conductors have been used where e.g. flexibility between two components has been needed.

[0003] It is known that in high frequency multiphase systems adjacent conductors are having an effect on each other in terms of coupling impedances therebetween. One way to mitigate the resistive losses caused by such coupling impedances is to use a so-called Litz wire. However, a Litz wire design is problematic in high power systems such as systems where a current above e.g. a 100A has to be conducted.

[0004] In that art of high-power current conductors twisted and flexible conductors are known. Such conductors are disclosed in WO2024199598 and comprises two bases between which twisted conductor branches are formed.

[0005] In systems conducting current where skin effect and heat dissipation is a problem, a conductor as described in prior art document CN114141405 can be used. CN114141405 discloses a conductor for eliminating skin effect and improve heat dissipation capacity without the need for additional equipment. The conductor comprises a pair of conductive bases which are oppositely arranged, and a plurality of conductive rods which are conductively connected between the pair of conductive bases. The rods and starting positions thereof in the base are numbered and theconductor is designed according to the following bending principles: the rods are numbered according to a pre-set sequence, taking the cross section of each conducting rod along the direction vertical to the current, moving each conducting rod cross section from the current position to the cross section position of the conducting rod with the next number, and moving the cross section of the conducting rod with the last number to the cross section position of the first conducting rod. In this way, because the conductor is split in 6 or 8 rods, the problem with skin effect and heat dissipation is mitigated, and because the 6 or 8 individual conductive rods traverse all 6 or 8 positions, the 6 or 8 individual conductive rods have the same equivalent impedance. CN114141405 further teach that in case of higher currents, the number of rods can be extended and illustrates this by extending the two bases to allow 18 rods positioned in two rows along the bases.

[0006] A conductor as disclosed in CN114141405 is problematic to use in a high-power / high-current electric cabinet in that the footprint required for a high-current version of the CN114141405 conductor is typically not available in an electric cabinet.Summary of the invention

[0007] The inventors have identified the above-mentioned problems and challenges related to high current cables and solved these problems by the present invention as described below.

[0008] In an aspect, the invention relates to a multi conductor system comprising at least two conductors, wherein at least one conductor of the at least two conductors comprising multiple grooves forming multiple branches, wherein the multiple branches are designed to facilitate sharing of a phase current, among the multiple branches, when said conductor is conducting the phase current, and wherein the design of the multiple branches furthermore is configured to maintain the sharing of said phase current when an electromagnetic coupling effect from an additional conductor of said at least two conductors impacts the conductor.

[0009] According to an embodiment of the invention, the distance between the at least one conductor and the additional conductor is equal to or less than 50 times thewidth of the at least one conductor, such as 25 times the width of the at least one conductor, such as 10 times width of the at least one conductor.

[0010] Advantageous in that an electrical current takes a predetermined path through the conductor. By taking the predetermined path it may be leading to optimized material usage which further may lead to change from copper to aluminium. The change from copper to aluminium may be preferred to save cost on material.

[0011] It is advantageous to have grooves in a conductor of a multi conductor system to facilitate distribution of a phase current, or simply just an electrical current, distributed through and across a conductor to increase the lifespan on the conductor, optimise material utilisation and mitigate electric loses in terms of heat generation. By distributing the electrical current more evenly through the conductor hot spots occurring from electromagnetic coupling effect may be prevented and it may not be necessary to cool down the conductor as much as compared to a conductor with unevenly current distribution. A sharing of a phase current may be understood as an evenly distribution of an electrical current through a conductor. The sharing of the phase current may still be shared when the conductor is affected by the skin effect and the proximity effect. The sharing may be facilitated by branches of the conductor. The branches are designed to maintain the sharing of the phase current when the conductor is affected by an electromagnetic coupling effect. The electromagnetic coupling effect is to be understood as the effect on the conductor from neighbouring or nearby electromagnetic fields. The branches on the conductor are designed to share the phase current and maintain the sharing of the phase current when a current is being conducted through the conductor (skin effect) and the conductor is being affected by electromagnetic fields (proximity effect).

[0012] The grooves establish branches which may be used to guide, control, and distribute the current more evenly through the conductor which prevents parts of the material of the conductor from not being used. Such control of current sharing / distribution between branches are made by designing the branches with respect to at least ohmic resistance.

[0013] When material is removed from the conductor to form grooves it may be done at predefined parts of the conductor to optimize the combination of material used and current flow. When predefining paths for the current through a conductor it may be possible to have the same conductivity even when using a less conductive material which is cheaper or easier to get. It may be possible to use e.g., aluminium instead of copper and have the same current running through the conductor without adding further additional cooling.

[0014] It may further be advantageous to have conductors with grooves to save on materials for making the conductors. The conductors may be created with grooves e.g. by extrusion, or the grooves may be made by removing material. When the material is removed it may be reused for other conductors or purposes. When material have been removed from the conductor, the conductor may still be capable of leading the same amount of current as prior to removing the material. The conductor with removed material may guide the current through the branches defined by the grooves of removed material to optimally use the remaining material in the conductor.

[0015] It may further be advantageous to have conductors where grooves are carved into the conductor after the conductor has been made. It may be difficult to make the conductors by e.g., adaptive manufacturing when the conductors become too big or long for a printing area although possible. The grooves may also be implemented in already existing conductors or busbars. A busbar is an example of a conductor

[0016] It may be advantageous to have grooves in conductors when two or more conductors are located near each other in a multi-phase conductor system to form a more uniform current distribution along the conductors. The electromagnetic coupling effect will affect the current distribution from one conductor to another when conductors are near each other. The electromagnetic coupling effect may force the current to run through the conductor either closest or furthest away from the other conductor and thereby making an uneven current density in the conductors.

[0017] The term conductor may be understood as electrical conductor which is used to electrically connect two electrical components or terminals. The conductor may bea busbar, power tube or any other kind of conductor for conducting an electrical current. The conductor may typically be made of copper or aluminium but may be made of any other electrically conductive material.

[0018] The term width may be understood as the distance from one side to another of a conductor. The width may be understood as from either a top or bottom of a groove to a corresponding top or bottom of a groove on the other side. The width may in some embodiments be understood as a diameter when a conductor may be round or oval shaped.

[0019] The term branch(es) may be understood as a part of a conductor where an electrical current typically is being conducted from one terminal to another terminal of the conductor. The branches may be designed to approximately share the current in the conductor evenly.

[0020] The term designed may be understood as how a conductor may be shaped or formed. The design may be referred to as a number of branches for the conductor or the number of grooves for the conductor. The design may further refer to the path of the branches or grooves along the conductor. The path of the branches may be designed along the conductor to have every position in the inner or outer perimeter of the conductor. A path may also only travel 90 or 180 degrees of the perimeter. The design of a branch may be a continuously path which changes constantly changes position in the perimeter of the conductor along the length of the conductor. The design may further be a discrete change in position of the perimeter of the conductor along the length of the conductor.

[0021] The term groove(s) is to be understood as a part of a conductor which is lowered compared to the surface of the conductor. The conductor may be created with a groove, or an existing conductor may have material removed afterwards to form one or more grooves.

[0022] The term first direction may be understood as the direction the electrical current is running through a conductor. The first direction may typically be understood as the direction along the conductor from a first terminal to a second terminal.

[0023] The term longitudinal circumferential outer part is to be understood as the part outside of a circumferential defined by phase branches and the space between phase branches. The space between the branches may be understood as the shortest distance from a branch to an additional branch. The circumferential defines an area outside and inside of a conductor.

[0024] According to an embodiment of the invention, the at least one electric conductor comprises a first end, a second end and a middle section provided between the first end and the second end, wherein the middle section comprises said multiple grooves.

[0025] Hence, a conductor is described comprising a first end, a second end and a middle section provided between the first end and the second end, wherein the middle section comprises at least one groove defining at least one branches extending between the first and the second ends. The electric conductor is a three-dimensional conductor. The middle section extend between the two conductor ends. The middle section comprises grooves. The grooves can extend all the way between the two conductor ends or the grooves can start and stop anywhere along the middle section. In this way the middle section may comprise one or more groove sections between the two conductor ends. Hence, the invention related to part, such as a middle section, of an electric conductor comprising at least one groove defining for forming at least one branches in the middle section.

[0026] An electric conductor with one or more grooves is advantageous in that it has the effect, that the current through such conductor is divided into each of the plurality of branches formed by these grooves. Hence, by design of these grooves (which could also be referred to as control elements for controlling consequences of electromagnetic phenomenon’s) it is possible to design / control how the current is conducted / guided through the part of the middle segment having grooves. Controlling where in the conductor the current is actually conducted can be done this way due to the electromagnetic phenomenon referred to as skin effect, that causes current to seek towards the perimeter of the conductor. Thus, when first the current has entered a branch, the current will stay in this branch.

[0027] By this opportunity to design control elements in the form of a groove and thereby control where in the conductor the current is actually conducted, it is possible to design a conductor with an equal distribution of current (also referred to as current density) across the cross-sectional area of the conductor. In this way, the amount of material of the conductor that is actually used for conducting current can be optimized. Such optimization may e.g. lead to a reduction of the cross-sectional area of the conductor and / or to choice of material that has a higher volumetric resistivity alternatively it allows to conduct higher current with the same current conducting cross-sectional area.

[0028] According to an embodiment of the invention, said at least one conductor is a tubular conductor.

[0029] It is advantageous to have conductors as tubular conductors also referred to as tubular busbars when having more than one conductor to balance skin and proximity effect. This is especially advantageous to optimize the conductor with respect to material usage in that due to the skin effect, only a limited part of the current is conducted in the center part of a conductor. Therefore the center part of the conductor can be removed forming a tubular conductor.

[0030] In some embodiments one conductor may be a tubular busbar but in a preferred embodiment multiple conductors of the multi conductor system are tubular busbars, preferably all of the conductors are tubular busbars.

[0031] The term tubular busbar may be understood as a hollow cylinder, square, rectangular, pipe or tube as a conductor. A tubular busbar may have grooves is applied. The hollow design may be advantageous for compensation for the skin effect. The tubular busbar may typically be used in high voltage environments.

[0032] According to an embodiment of the invention, all of said at least two conductors in said multi conductor system are tubular conductors.

[0033] It is advantageous to have conductors formed, shaped or designed as hollow conductors, such as tubes or pipes due to the skin effect of the electrical current. Thecurrent density of a normal massive conductor may have a high current density near the surface of the conductor. The normal massive conductor may have a small current density along the centre of the conductor and the cost of removing the material along the centre may be very small. The savings in removing the material along the centre may be advantageous since approximately the same current can be conducted with less material used for the conductor.

[0034] The term power tube may be understood as a conductor formed as a pipe or a tube with a hollow centre along the longitudinal centre axis. The power tube may have multiple grooves along its outer perimeter. A tubular conductor may have one geometry of its inner perimeter (such as oval) and another of its outer perimeter (such as circular).

[0035] According to an embodiment of the invention, said at least one conductor is angled according to a longitudinal direction of said at least one conductor, wherein said angle is different from zero.

[0036] It may be advantageous to have a conductor who can bend or be turned to fit into different electric systems. The conductor may be able to electrical connect items which are located next to each other and not just in a straight line from one to another.

[0037] According to an embodiment of the invention, the width of each of said multiple grooves are between 0,1mm and 5mm.

[0038] A minimum width of an individual groove depends e.g. on the difference between the voltage measured over two neighbouring branches. The closer these voltages are, the smaller groove width is required. Small groove width, e.g. from 1mm going towards 0.05mm, is advantageous in that more of the perimeter of the conductor is available for current conduction. Lager groove width, e.g. from 1mm going towards 6mm, is advantageous in that the conductor is able to be more flexible before edges of the grooves short due to e.g. bending of the conductor.

[0039] In principle, the width of the groove can be as small as allowed by method of producing the conductor with grooves / the grooves in the conductor.

[0040] According to an embodiment of the invention, said multiple grooves extends between said first end of the at least one conductor and a second end of the at least one conductor in said middle segment.

[0041] According to an embodiment of the invention, the depth of at least one of said multiple grooves is between 5% and 100% of the skin depth of the current conducted by the at least one conductor.

[0042] A groove depth between 25% and 100%, such as between 30% and 100%, such as between 35%-50% of the skin depth may be sufficient to control the most of the current through the conductor by controlling the branch through the conductor.

[0043] Note that perimeter and circumference are both ways of referring to the outer distance around a conductor. Circumference is typically used when the conductor is spheric and perimeter is typically used when the conductor has a geometry that is different from spheric.

[0044] The skin effect is caused by currents induced by the changing electromagnetic fields resulting from the alternating current conducted by a conductor. The skin effect results in a tendency for the current conducted by the conductor to seek towards the outer edge of the conductor. Most current is conducted closest to the perimeter of the conductor. Hence, as the distance increases from the perimeter towards the center of the conductor, the current density decreases.

[0045] The proximity effect is caused by the presence of electromagnetic fields generated by alternating currents conducted by nearby conductors. The proximity effect results in a tendency for the current conducted in two nearby conductors to flow in other undesirable patterns, such as loops or concentrated distributions e.g. in the side, of the two nearby conductors, facing each other or is facing away from each other.

[0046] According to an embodiment of the invention, at least one of said multiple grooves has a varying depth.

[0047] A varying depth should be understood as a depth of the groove changing between 0mm and maximum, where maximum is all the way through the conductor in a crosse sectional view. Thus, an example of varying depth is a depth between 0mm and distance between outer and inner perimeter of a hollow conductor.

[0048] A varying depth can be implanted in a system where two conductors are provided next to each other for e.g. 90cm and for a further 90cm the second conductor does not have any nearby conductors. In that situation, the grooves are provided in the two conductors during the first 90cm and not in the second conductor for the last 90cm. Further, it would be advantageous if the helix of the two conductors during the first 90cm takes one full turn around the conductor.

[0049] Further, varying depth is advantageous in that it has the effect that it can be used to determine the strength of the conductor such as the yield point between elastic and plastic deformation of the conductor. Accordingly, where mechanical stability of the conductor is prioritized over current control through the conductor the depth of the grooves can be reduced. In one extreme the reduction can lead to what is referred to as a virtual groove i.e. a groove that is not made into the perimeter of the conductor at least part of the way.

[0050] According to an embodiment of the invention, the slope of at least one of said multiple grooves is varying.

[0051] A varying slope of e.g. two grooves will shape the branch accordingly. Hence a slope of 0 is considered a straight slop whereas a slope of 90 is considered a slop going perpendicular to the direction of the aforementioned straight slope. As mentioned above with respect to the depth of the groove the slope of the groove may also vary along the length of the conductor. The effect of a varying slope is that the length of the electric path along the conductor may be controlled and the mechanical structure / strength along the conductor may be controlled. Continuous grooves should be understood as the slope of the groove is continuous increasing or decreasing or the slope may be constant

[0052] According to an embodiment of the invention, said multiple grooves has a width equal to or less than the width of said multiple branches.

[0053] According to an embodiment of the invention, said multiple grooves have a width equal to or greater than the width of said multiple branches.

[0054] According to an embodiment of the invention, at least one of said multiple grooves has extended at least 50% of the total perimeter of said conductor between said first groove point of said conductor and the second groove point of said conductor.

[0055] 50% of the perimeter along the length of said conductor may be understood as 180 degrees when stacking all cross-sectional views of the conductor in a longitudinal direction.

[0056] According to an embodiment of the invention, said sharing is a sharing of said total electrical current through said at least one conductor divided by the number of said multiple branches.

[0057] A sharing of a total electrical current may be shared with an equal amount of current through each conductor or each branch. The sharing may further be shared according to a sharing that is 50% - 100% such as 60%-100%, such as 70%-100% of total current / number of branches. The sharing is facilitated or controlled by the design of the grooves / branches.

[0058] According to an embodiment of the invention, said multiple grooves is forming the multiple branches so that the resistance of the multiple branches is the same.

[0059] The same resistance here should be understood as substantially the same resistance in that it may be extremely difficult to ensure a 100% equal resistance between e.g. 5 branches of a conductor. Thus, the same resistance here should be within a margin of e.g. 5%.

[0060] A non-limiting example for explanation of branch design with the same resistance is branches of the same dimensions (length and cross-sectional area) andmaterial. If for some reason (e.g. a bending conductor) the length of two branches is not the same, the cross-sectional area of one or both of the branches may be modified to ensure same resistance and thereby ensure equal current sharing between these two branches. The designing of the branches may include a trial-and-error process or simulation, wherein an electric conductor with grooves is provided, an AC current is conducted, and the electric losses are measured or calculated; after a first iteration, the number of grooves, the depth of the grooves, the width of the grooves, or other parameters may be changed and the change in electric losses is determined, thereby allowing preferred design parameters of the conductor to be found.

[0061] According to an embodiment of the invention, at least one branch of said multiple branches has a different length compared to the rest of said multiple branches.

[0062] It may be advantageous to have a branch with a different length compared to the rest of the branches to facilitate or maintain an equal sharing of an electrical current e.g. if the conductor bends.

[0063] According to an embodiment of the invention, at least one of said multiple grooves are uniform.

[0064] According to an embodiment of the invention, said multiple grooves are airgaps in said conductor.

[0065] According to an embodiment of the invention, said multiple grooves extend from one terminal of said at least one conductor to a second terminal of said conductor.

[0066] According to an embodiment of the invention, said plurality branches meet towards at least one of the first end and the second end of said at least one conductor.

[0067] This is advantageous in that it has the effect, that mechanical stability is added to the conductor that may otherwise be too flexible due to the grooves. This is especially true as the depth of the grooves gets close to or equal to the distance between the inner and outer perimeter of a hollow conductor and between the two opposing perimeter points of a massive conductor. As an example, where it is especially true isif more than half, such as all of the grooves, are having a depth that is equal to the distance between the inner and outer perimeter.

[0068] This is furthermore advantageous in that the total current conducted by the conductor is not restricted by grooves and thus can flow freely in the entire cross-sectional area of the conductor before it is divided into the branches formed by the grooves. It is preferred that an area of the conductor not having grooves is an area which do not have a neighbouring conductor and thus not exposed to the proximity effect.

[0069] It should be noted that the meeting of the branches may also be implemented in an end piece in which the branches are mounted e.g. for commonly being connected to an electric component.

[0070] According to an embodiment of the invention, at least two neighbouring branches of said multiple branches are connected by a branch connector, the branch connector establishes a connection across at least one of said multiple grooves from the first groove side to the second groove side of the groove.

[0071] According to an embodiment of the invention, the branch connector is connecting the first and second groove sides at the location along the middle section, where an open voltage potential difference between the first branch and the second branch is 0V.

[0072] This is advantageous in that it has the effect, that mechanical stability is added to the conductor that may otherwise be too flexible due to the grooves. This is especially true as the depth of the grooves gets close to or equal to the distance between the inner and outer perimeter of a hollow conductor and between the two opposing perimeter points of a massive conductor. As an example, where it is especially true is if more than half, such as all of the grooves, are having a depth that is equal to the distance between the inner and outer perimeter.

[0073] This is furthermore advantageous in that the total current conducted by the conductor is not restricted by grooves and thus can flow freely in the entire cross-sectional area of the conductor before it is divided into the branches formed by the grooves. It is preferred that an area of the conductor not having grooves is an area which do not have a neighbouring conductor and thus not exposed to the proximity effect.

[0074] It should be noted that the meeting of the branches may also be implemented in an end piece in which the branches are mounted e.g. for commonly being connected to an electric component.

[0075] An open voltage potential difference should be understood as the voltage difference between two branches that are not electrically connected. Once connected, the voltage difference becomes 0.

[0076] Branch connectors are advantageous in that they have the effect, that they add mechanical stability to the conductor. Especially, in the situation where the depth of the grooves forms individual air insulated branches or where the grooves are so deep that the branches are only connected / short towards the center of the conductor with less than e.g. 10mm of material.

[0077] A non-limiting example for explanation could be if the depth of the grooves is 10mm and the distance between inner and outer perimeter is between 10 and 15mm, then branch connectors could be one way of increasing mechanical strength of the conductor. Further, it may be advantageous to obtain a desired mechanical strength by implementing two branch connectors with a small diameter instead of one branch connector with a larger diameter.

[0078] The closer the position of the branch connector is to where the open voltage difference is 0V, the smaller difference in the open voltage potential between the two branches is where the branch connector is position. The closer to 0A the current conducted between the two branches is, when they are connected by the branch connector.

[0079] Further, the thinner the branch connector is, the less current is conducted. Hence, the diameter of the branch connector should be a trade-off between its diameter and the required mechanical support from the branch connector.

[0080] According to an embodiment of the invention, the diameter of the branch connector is below 10mm, such as below 5mm, preferably below 2mm.

[0081] By reducing the diameter of the branch connector as much as possible the risk of current conducted by the branch connector between two branches is reduced. This would help reducing the effect of a misplacing of the branch connector from the position of the zero open voltage.

[0082] According to an embodiment of the invention, all of said multiple branches are connected by branch connectors.

[0083] According to an embodiment of the invention, said multiple grooves travels around the outer perimeter of the at least one conductor, thereby forming the multiple branches as spiral branches.

[0084] A conductor with spiral branches is advantageous in that it has the effect, that the current conducted in the individual of the plurality of branches travels around the conductor perimeter. This is particularly relevant in AC multi-phase systems and in AC multi -conductor systems where an electromagnetic fields is created around the individual conductor. An electromagnetic coupling effect, in this context referred to as proximity effect, is associated with the electromagnetic fields, an effect that impact the current conducted in a neighbouring conductor. The closer the two conductors are, the higher impact. Hence, due to the proximity effect, the current is either dragged towards or pushed away from the neighbouring conductor. If no spiral was established, this would cause the current to run in undesirable patterns, such as in loops or concentrated in one side of the conductor and thus not use the material in the other side of the conductor for current conduction. By forming spiral branches, the current is forced around the perimeter of the conductor and thus material around the conductor perimeter is used for current conduction.

[0085] According to an embodiment of the invention, at least one groove of said multiple grooves is traveling between 90 degrees and 360 degrees around the outer perimeter of the at least one conductor between the first groove point and the second groove point.

[0086] The closer to 360 degrees the grooves travel around the conductor, the better with respect to optimal usage of material for current conduction. However, effects may occur also if the grooves only travel 90 degrees. Hence, it is preferred, that the grooves travel between 90 degrees and 360 degrees. Note that over 360 degrees i.e. more than one turn could also have effect. It should be noted that one turn of the groove is sufficient to sufficiently eliminate the consequence of the proximity effect. In some designs of the conductor, one continuous groove of one turn is not possible and thus one or more than one turn may be provided by one or more groove parts. However, it should be noted that the longer groove, the longer current path and thus higher resistance to the current through the conductor. Accordingly, the number of turns of the helix should not be increased without considering this aspect.

[0087] According to an embodiment of the invention, at least one groove of said multiple grooves is formed as a continuous groove or as a stepwise groove in the outer perimeter of the at least one conductor.

[0088] The implementation of the groove may not be important from an electric perspective, the current carrying capacity of the conductor would typically not change significantly. Relevant is that the groove is provided and both with respect to production and current conduction a continuous groove with not too many changes of directions is preferred. A stepwise groove may still be used; however, the angles of the steps should be above 90 degrees.

[0089] The length of the spiral groove between the first and second groove points may be coincident with the length of the conductor between its two ends i.e. between its first and second ends. If however, the conductor is short relative to its diameter, a spiral grove less than 360 degrees may be provided. In an embodiment a lower limit for a conductor length where it is advantageous to include a spiral groove is aconductor length that is at least 2,5 or 3 times the diameter of the conductor. As an example, % (90 degrees) of a complete spiral may be provided in a conductor that has a diameter of 50mm if its length is 150mm. from this lower limit relationship of length and diameter, the spiral groove may increase it way towards a full spiral i.e. 360 degrees.

[0090] According to an embodiment of the invention, at least one groove of said multiple grooves only partly extends between the first and second ends of the at least one conductor.

[0091] As the electric path through the conductor is increased with the spiral branch, the resistance of the electric path is increased. Thus, the advantage gained by reducing the consequence of the proximity effect have to be compared to the disadvantage of the longer electric path.

[0092] If the conductor is to be positioned without a neighbouring conductor, the conductor is not exposed to the proximity effect form a neighbouring conductor and thus do not need spiral grooves for controlling the current.

[0093] According to an embodiment of the invention, the step of establishing the electric conductor with the electromagnetic effect control element is implemented by one of the list comprising milling, casting, and additive manufacturing.

[0094] Additive manufacturing however is not the preferred method of establishing a conductor with electromagnetic effect control element. This is because such conductors often are required to be more than 40cm and above that size most additive manufacturing machines are not possible to use. Further, it is expensive to produce electric conductors by additive manufacturing and it is time consuming. Hence, contrary to other types of electric conductors, where additive manufacturing is advantageous, additive manufacturing is not always the preferred manufacturing method for producing the electric conductor according to the present invention.

[0095] According to an embodiment of the invention, said at least one conductor comprises as at least two individual phase conductors, wherein said at least two individual phase conductors comprises multiple grooves forming multiple branches.

[0096] The term comprises or implemented as at least two individual phase conductors may be understood as individual phase conductors used for conducting a current. All of the individual connected individual phase conductors may be understood as a conductor in a multi conductor system. The individual phase conductors may conduct a shared current or a shared phase current of the total current conducted by the conductor.

[0097] The individual phase conductors may be designed or placed in different configurations to form the conductor. The individual phase conductors may also be generated / made while the conductor is being made. The individual phase conductors may typically be approximately identical regarding mechanical and electrical design. The individual phase conductors may be designed to facilitate sharing of an electrical current with respect to electromagnetic fields from each other and other conductors. It may in some embodiments be advantageous to design individual phase conductors differently. One individual phase conductor may be designed with different mechanical grooves compared to a second individual phase conductor of the same conductor. The difference in e.g., grooves between two individual phase conductors may be advantageous to facilitate a sharing of an electrical current in the two individual phase conductors.

[0098] Other configurations of individual phase conductors may depend on the number of individual phase conductors of a conductor. When three individual phase conductors are used it may be advantageous to have a triangular design with approximately an equilateral triangle with an individual phase conductor in each corner. The triangular design may be advantageous for sharing the current between the individual phase conductors by equalizing the proximity and skin effect. When using three individual phase conductors it may be advantageous to locate the three individual phase conductors in a triangular design (seen from end perspective) where three lines of symmetry may be drawn.

[0099] It may in some configurations be more advantageous to have three individual phase conductors placed along a line due to space optimization. When located along a straight line it may be necessary for some of the individual phase conductors to switch place alone the length of the conductor to facilitate a sharing of an electrical current. It could be two conductors on the sides switching place halfway through the length of the conductor.

[0100] Other configurations may comprise four, five or more individual phase conductors where the design of the configuration may typically be designed to facilitate the sharing of an electrical current. The configuration with four individual phase conductors may be designed like the four-marking point on a normal six-sided dice with one individual phase conductor in each comer of the total conductor. In case of four or more individual phase conductors, the individual phase conductors should switch places along the conductor to facilitate the sharing of an electrical current. The individual phase conductors would typically switch places two and two. In the configuration with five individual phase conductors, it may be advantageous to have approximately the same as with four individual phase conductors with the additional phase conductor in the middle between the four. Further configuration with multiple individual phase conductors may be used and designed to facilitate a sharing of current with respect to skin and proximity effect from the individual phase conductors and other conductors. In some configurations it may be advantageous to have similar types of individual phase conductors with respect to mechanical design where e.g., grooves may be similar and form similar branches. Other configurations may be designed to have different mechanical designs where e.g., a different number of grooves are used for each individual phase conductor or the number of turns for the grooves are different. All configuration may be designed with respect to the sharing of the electrical current of the conductor where the individual phase conductors are implemented. The configurations of the individual phase conductors may also be designed with respect to space optimization in different settings.

[0101] According to an embodiment of the invention, said at least two individual phase conductors are arranged in a side-by-side configuration.

[0102] The term side by side may be understood as an over and under configuration when seen from a different perspective. The side-by-side term may be understood as one individual phase conductor located either above or below a second individual phase conductor. It may be understood as seen from an end view of the individual phase conductors. It may also be understood as with respect to another specific embodiment like an additional conductor or according to a base line.

[0103] It may be advantageous to have more individual conductors when a higher current is being conducted since the individual conductors may share the current more evenly.

[0104] The term over-under configuration may be understood as two conductors placed with one above the other. The two conductors may have their centre along the same axis forming a symmetry and thereby reducing the proximity effect for the two conductors.

[0105] It may be advantageous to have two conductors in an over-under configuration when conducting a phase current next to other conductors. It may optimize the space required for a multi conductor system to have two conductors located side-by-side.

[0106] According to an embodiment of the invention, said at least two conductors are electrically connected and positioned side by side.

[0107] It may be understood that the conductor and the additional conductor mentioned above is connected and positioned side by side. The two conductors may be positioned within a distance therebetween of less than 25cm, such as within 20cm, such as within 10cm, such as within 8cm, such as within 5 cm. The side-by-side configuration of the two conductors may in an embodiment be twisted along the length of the at least two conductors in order to facilitate a sharing of an electrical current. When more current may be conducted an additional third conductor may be added to the embodiment of the invention.

[0108] According to an embodiment of the invention, said multi conductor system is a multi-phase conductor system, wherein said at least one conductor is configured to conduct a first phase current and said additional conductor is configured to conduct a second phase current.

[0109] According to an embodiment of the invention, said additional conductor comprises at least two individual phase conductors.

[0110] According to an embodiment of the invention, said multi -phase conductor system comprises a third conductor wherein said third conductor comprises at least two individual phase conductors, wherein said third conductor configured to conduct a third phase current.

[0111] Some systems require three or more phase currents. In such multiphase systems the multi conductor multi-phase system of the present invention is advantageous in that it mitigates the impact of the proximity effect of neighbouring phase currents.

[0112] It may be advantageous to have three conductors in a triangle configuration with two side-by-side and the last conductor placed above or below, where the three conductors are approximately the same distance apart. It may be advantageous in reducing the skin and / or proximity effect of the other conductors.

[0113] It may be advantageous to have more phases in a system, where potentially 6, 9, 12 or 18 phases could be used. Typically, the more phases may be used when guiding a current in a one-way direction. The system may also include 3 times 2 phases with three phases in and three phases out.

[0114] According to an embodiment of the invention, the individual phase conductors of said at least one conductor, said additional conductor and said third conductor are placed side by side.

[0115] According to an embodiment of the invention, said at least one conductor, said additional conductor and said third conductor each comprises three individual phase conductors.

[0116] According to an embodiment of the invention, said at least one conductor, said additional conductor and said third conductor each comprises three individual phase conductors, wherein the distances between the centers of said three individual conductors are the same.

[0117] A conductor comprising at least three individual phase conductors may have the three individual phase conductors in different configurations. A typical configuration may be understood as an approximately equilateral triangle seen from an end perspective. It may be advantageous to have the three individual phase conductors as a triangle to facilitate a sharing of an electrical current by minimizing the skin and proximity effect.

[0118] The three individual phase conductors may also be in a configuration on a line next to each other. In that configuration it may be necessary to have the two outer individual phase conductors to switch location along the length of the at least one conductor for optimizing the facilitation of an electrical current.

[0119] According to an embodiment of the invention, the at least individual phase conductors in one of said at least two conductors, are having different length.

[0120] According to an embodiment of the invention, said at least two individual phase conductors of said at least one conductor are grouped into a plurality of subgroups.

[0121] According to an embodiment of the invention, said plurality of sub-groups is changing positions along the longitudinal length of said at least one conductor.

[0122] The term sub-group may be understood as multiple individual phase conductors of a conductor leading the same phase current. The sub-groups may share similar geometry, turning, twisting or angle along the length of the conductor.

[0123] It may be understood that four conductors placed in a double side-by-side and double over-under may be an approximately symmetrical configuration. The configuration may be symmetrical in multiple planes going through a centre-axis of the phase.

[0124] The individual phase conductors in a sub-group may share the same electrical properties as branches for a conductor comprising grooves. The individual phase conductors may be twisted like branches or may be formed by grooves in a conductor to facilitate a sharing of an electrical current between the individual phase conductors.

[0125] According to an embodiment of the invention, the at least two individual phase conductors of said additional conductor and said third conductor are grouped into a plurality of sub-groups.

[0126] According to an embodiment of the invention, said plurality of sub-groups of said at least one conductor, said additional conductor, and said third conductor are changing positions along the longitudinal length of said at least one conductor, said additional conductor, and said third conductor.

[0127] It may be advantageous to have sub-groups of individual phase conductors where a group of individual phase conductors may act as one conductor. The subgroups may share mechanical and / or electrical properties similar to branches formed by grooves in a conductor.

[0128] According to an embodiment of the invention, said at least two conductors are designed with multiple grooves, where said design is different for at least two of said at least two conductors.

[0129] The term design of multiple grooves may be understood as the number of grooves in a conductor. It may be two grooves in a first conductor and three grooves in a second conductor, which may be advantageous to facilitate a sharing of an electrical current.

[0130] The term design of multiple grooves may in some embodiments be understood as the dimension of grooves e.g., length, width or depth. The difference in the design of grooves relating to the dimension of grooves may be just one of width, length or depth or may in other embodiments be a any combination of them.

[0131] The different design of at least two conductors may be understood as two conductors are having a different design of grooves. If more than two conductors arepresent it may be understood that only two conductors have different designs and the rest of the conductors share the design with one of the two conductors. It may also be understood that all of the conductors are designed differently to each other. It may also be any kind of combination of different designs and equal designs of grooves which may be advantageous to e.g., facilitate a sharing of an electrical current or save material in the conductors.

[0132] Different design may be understood as the number of grooves for a conductor, where different settings or configurations may need different number of grooves for the conductor. The design of the conductor may also be understood as where a groove may start and / or end at positions located on the conductor. It may in some embodiments be advantageous to have a groove starting from the edge of the end of the conductor to the opposite end of the conductor. It may in some embodiments be advantageous to have a groove length in a middle section of the conductor.

[0133] Another design parameter, beside the above mentioned length, depth, width, etc., of a conductor may be the number of turns grooves / branches take around the perimeter of the conductor. Typically, it may be from one quarter, half or full turn (90, 180, 360 degrees) around the conductor to multiple turns. It may also be understood as a design parameter what direction the grooves / branches are turning around the conductor, e.g., clockwise or counter clockwise.

[0134] According to an embodiment of the invention, a first of said at least two individual phase conductors is designed to comprise a second of said at least two individual phase conductors inside at some point along the at least one conductor.

[0135] According to an embodiment of the invention, said first and second individual phase conductors are designed to switch place with each other at said middle section

[0136] The term designed to have an individual phase conductor inside another individual phase conductor may be referred to as multi-layered busbar. A multi-layered busbar may e.g. have a square or tubular geometry where the different layers switches radial position at one or more points along the length of the conductor. The switch is typically done at a middle section, where the inner individual phase conductor switchesplace with the outer individual phase conductor. In this way the distance of the length of the conductor both of the first and second individual phase conductors are inside the other is the same and thereby from the currents perspective both to the first and second individual phase conductors are equally attractive with respect to skin effect.

[0137] The multi-layered busbar may be three or more layers, where each layer (individual phase conductor) may switch to all other radial position at least once along the length of the conductor. The design of having all individual phase conductors at each radial position along the length of the conductor may facilitate a sharing of an electrical current. It may further be advantageous to optimize the space for the conductor.

[0138] According to an embodiment of the invention, the at least one groove is a virtual groove. A virtual groove should be understood as a groove that is not made into the perimeter of the conductor at least part of the way. This is advantageous because of the option to optimize for mechanical and / or electrical properties and / or cost in different sections of the conductor.

[0139] According to an embodiment of the invention, at least a first of a plurality of grooves start a first distance from the first end of the conductor, wherein at least a second of the plurality of grooves start a second distance from the first end of the conductor and wherein the first and second distance are different. Different start positions of the grooves is advantageous in that it has the effect, that hereby it is possible to provide a desired mechanical strength to the conductor by varying the start position of the plurality of grooves.

[0140] According to an embodiment of the invention, at least one of the multiple of branches defined between two grooves has a width between -30% of the skin depth of the current conducted by the conductor and +30% of the skin depth of the current conducted by the conductor. A theoretic optimal width of a branch may correspond to the skin depth. Hence if the skin depth is 10mm, the width of the branch could be 10mm. Thereby, the current density in the branch is equally distributed. Obviously, a width not exactly corresponding, such as equal to, the skin depth would also in manyimplementations be sufficient. Therefore, referring to the example above if the width is + / - 30% of the skin depth, the width could be between 7mm and 13mm. The width may alternatively be below + / - 50% of the skin depth.

[0141] According to an embodiment of the invention, the at least one groove is filled with a filling material. The filling material may be selected from the list comprising: epoxy, polymer, coating and varnish. Beside using air to fill the groove and thereby separate the branches other types of filling material may be used. If the conductor is made of Aluminium, the surface tends to oxidize and the oxidation layer may be considered a filling material in that it has an electric isolating effect. Obtaining an electric isolating effect is advantageous especially if the conductor needs to bend. At the inside of such bend, the edges of the groove tend to approach each other and in that situation, a filling material in the groove would reduce risk of electric contact between the two edges / sides of the groove.

[0142] According to an embodiment of the invention, the at least one groove has a width of at least 0,1% of the total perimeter of the electric conductor, wherein the width is measured as the length of a straight line between a first groove side and a second groove side. Alternatively, the width may be measured between two groove points along an outer perimeter or of a bottom of a groove of the conductor.

[0143] According to an embodiment of the invention, the distance between the first end and one of the first groove point and the second groove point is at least 1cm. A distance of at least 1cm from the first end of the conductor to where the grooves start is advantageous in that a fixed end of the conductor is provided. Such fixed end can be used for mounting an end piece or similar used to connect the conductor to other components. A fixed end may also be used for current to distribute between the branches formed by the grooves.

[0144] According to an embodiment of the invention, the electric conductor comprises a center conductor part having a center perimeter partly defined by bottoms of a plurality of grooves, and wherein the plurality of grooves is forming the plurality of branches so that the width of at least part of the plurality of branches is larger at theouter perimeter surface than at the center perimeter. A conductor may be formed with branches having a width measured between groove sides which towards the outer perimeter of the conductor has a first measure and towards the center perimeter has a second measure where the first measure is larger than the second measure. Such conductor is advantageous in that the cross-sectional area of the part of the branch where most current is conducted due to skin depth is largest.The drawings

[0145] For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts. The drawings illustrate embodiments of the invention and elements of different drawings can be combined within the scope of the invention:Fig. 1 illustrates a single phase multi conductor system,Fig. 2 illustrates two prior art conductors,Fig. 3a, 3b, 3c and 4 illustrates conductors with grooves that may be used to balance the multi conductor systemFig. 5 illustrates a two phase multi conductor system,Fig. 6 illustrates a three phase multi conductor system,Fig. 7 illustrates a three phase multi conductor where each phase comprises three individual phase conductors, andFig. 8a and 8b, 9 and 10 illustrates alternative multi conductor systems,Detailed description

[0146] The present invention is described in view of exemplary embodiments only intended to illustrate the principles and implementation of the present invention. Theskilled person will be able to provide several embodiments within the scope of the claims which may not be directly illustrated in the figures or directly described below.

[0147] Fig. 1 illustrates a multi conductor system MC according to an embodiment of the invention with two individual phase conductors IPC. The multi conductor system MC has a first end (IE) and a second end (2E) with a middle section (MS) in between the two ends. The individual phase conductors IPC are illustrated with multiple grooves (G) that are forming multiple branches (B). The individual phase conductors IPC is illustrated with 7 grooves (G) but may in other embodiments of the invention be any number of grooves from 2 and up to 100. In the illustrated embodiment of the invention the number of branches (B) correspond to the number of grooves (G). The number of branches may in other embodiments of the invention vary from 2 and up to 100. In the illustrated embodiment of the invention in fig. 1 the number of grooves corresponds to the number of branches but may in other embodiments of the inventions not necessarily be the same number.

[0148] In fig. 1 the two individual phase conductors IPC are illustrated similar conductor type and design with the same number of grooves (G) and branches (B). In other embodiments of the invention one of them may be a more standard or typical conductor which does not necessarily comprise grooves and branches. The multi conductor system is illustrated as a system designed for equally sharing a total electrical current between the two individual phase conductors IPC. The sharing of the electrical current in the two conductors of the system may be approximately the same in this embodiment of the invention. In other embodiments the system may facilitate a sharing of the electrical current with a more preferred conductor which may vary from 50-100% current through one of the at least two conductors.

[0149] The two individual phase conductors IPC illustrated in fig. 1 is shown made of copper but may in other embodiments be made of other electrical conducting materials e.g., aluminium or an alloy. The at least two conductors may in some embodiments be coated (not shown) with an isolating material.

[0150] In an embodiment of the invention one of the individual phase conductors IPC may be a simple conductor without grooves (not shown), e.g. like a standard solid busbar or rod conductor. The conductor with grooves would still be affected by the proximity effect from the electromagnetic fields from the more standard conductor, but the grooves would reduce the effect and provide a more even current distribution in the conductor with grooves. Furthermore, the solid conductor (or more standard conductor) may not necessarily conduct the same phase current as the conductor with grooves in the multi -conductor system.

[0151] From the above it is now clear that this embodiment of the invention relates to multi conductor system with grooves forming branches. The grooves G provided in the current conducting material of the conductors are made to control the consequences of electromagnetic phenomenon’s from the conductor itself and or from a neighbouring conductor. Thus, the grooves may also be referred to as electromagnetic fields control element.

[0152] No matter type of conductor material, it is obviously preferred to utilize the conductor material best possible. It is known that current conducted through a cable / conductor is influenced by electromagnetic forces. This influence can be divided into impact from electromagnetic fields origin from the conductor which in this document is referred to an internal impact and, impact from electromagnetic filed origin from a nearby conductor which in this document is referred to as an external impact.

[0153] The internal impact results in a tendency of the current that is conducted, to be conducted towards the perimeter of the conductor. The electromagnetic phenomenon causing this tendency is referred to as skin effect. The extend to which this tendency is dominant i.e. how deep into the conductor, from the outer perimeter towards the center of the conductor, the current is conducted, is depending on the resistivity of the conductor and the frequency of the current.

[0154] The skin depth is calculated by equation 1 :£ J — — f ~ Frequencyp ~ Resistivity ™ 4?rx 10

[0155] EQ1: "

[0156] The skin effect is a fact in AC systems and is undesired in that it may cause heating in the conductor and uneven current density across the cross-sectional area of the conductor, leading to conductor material not being used for conducting current.

[0157] The external impact occurs when a first conductor is conducting an AC current, and that conductor is located next to a second conductor or other current conducting elements that is conducting a current (AC or DC). The external impact results in a tendency of the current that is conducted in the second conductor, to be pushed away from the first conductor or dragged towards the first conductor. Whether the current is pushed or dragged depends on the direction of the current in the first and or in the second conductor. The electromagnetic phenomenon causing this tendency is referred to as proximity effect. The extend to which this tendency is dominant i.e. how much the current is pushed or dragged is depending on the distance between the first and second conductors and the magnitude of the current. The higher current and the closer distance the stronger proximity effect.

[0158] Summing up, when conducting an AC current in a conductor, the current will have a tendency to seek to the perimeter of the conductor leading to increased losses and unused material in the center of the conductor. Further, if the same conductor is located next to another current conducting element such as a conductor, the current in that conductor will have a tendency to displace the current towards one of the sides of the conductor.

[0159] Fig. 2 illustrates two prior art massive conductors without grooves conducting a current PC that is influenced by both the skin effect and the proximity effect. As illustrated, the current is concentrated at the perimeter of the conductors and towards the side of the nearby conductor. Because a conductor is positioned nearby, the current would displace in the cross-sectional view, e.g. as indicated in fig. 2 due to theproximity effect. To avoid this, the inventors have provided helix grooves G in the conductors as illustrated in fig. 3a and 3b.

[0160] When the current conducted by a conductor, with a plurality of branches B as the conductors of fig. 3a and 3b, is not influenced by the proximity effect from a neighbouring conductor and when the resistivity in the branches B is the same, an equal share of the total current hot is conducted in the 6 branches of the conductor of fig. 3a. Assuming that all of the current was conductor in the branches (i.e. the conductor only comprises branches that are not electrically connected between the ends), each branch would conduct hot / 6 current.

[0161] If the branches / grooves were not helix branches / grooves and a conductor was positioned nearby, the current would displace in the cross-sectional view, e.g. as indicated in fig. 2 due to the proximity effect. To avoid this, the inventors modified the grooves G. The modification consists in letting the grooves G spin around the perimeter of the conductor as illustrated in fig. 3a and 3b forming a helix groove also referred to as a spiral in this document. In this way, the branches may be referred to as electromagnetic effect control elements. Such modified electromagnetic effect control element may result in a spiral groove encircling the perimeter of the conductor. In an embodiment, each branch B would encircle the perimeter of the conductor once i.e., a 360 degrees encircling.

[0162] The skin effect causes the current to be conducted in the branches (even in a massive conductor). When the branches are turning in a helix around the perimeter of the conductor, the current in the branches on the opposite side of the conductor, with respect to the nearby conductor causing the proximity effect, cannot “flow out of the branch” and the proximity effect is thus eliminated. The reason why the helix around the perimeter works is because in this way all branches experience the same average field from nearby conductor(s). Hence, induced voltages in all branches equal out, thereby eliminating the possibility of electromagnetic force driving eddy currents in the branches.

[0163] In this way, contrary to the conductor illustrated in fig. 2, the material of the conductor on the opposite side of the nearby conductor, is also used for conducting current. Thereby, a conductor optimized with respect to usage of conductor material is provided.

[0164] The effect of the spiral grooves i.e. the optimized material usage may have the effect that the cross-sectional area of the conductor can be reduced. Hence, compared to copper conductors without spiral grooves, the current conducting cross-sectional area of a copper conductor with spiral grooves can be reduce with more than 50%. Simulations have shown that in large systems where five to six 10mm x 100mm copper conductors (alternatively conductors with a cross-sectional aera up to and above 5.000mm2 just to mention two examples) are used to conduct a phase current, a reduction of up to 70% of the copper material can be saved. If the frequency is higher e.g. in electric systems comprising reactors, semiconductor switches such as IGBT, the frequency is higher and thus the savins on material can be higher. In such systems the phase current conducted may be 1000A to 6000A or up to 10.000A or higher.

[0165] As mentioned, the conductor illustrated in fig. 3a and 3b may be square massive (fig. 3a) or tubular conductor i.e. a conductor where the center part is removed and thus the cross-sectional area is defined between an outer perimeter OP and an inner perimeter IP (fig. 3b). As indicated, the grooves can be implemented in massive conductors or in other not mentioned types of conductors having the effect describe in this document.

[0166] The interior space defined by the inner perimeter of a tubular conductor can be used for guiding of a cooling fluid. Hence, if a flow of air is directed through the interior space, heat from the conductor can be removed.

[0167] Note that even though grooves are mentioned, protrusions may be used to have the same or a similar effect. And note that the grooves may be provided in from the inner perimeter and outwards and not as illustrated in fig. 3b from the outer perimeter and inwards.

[0168] In general, the grooves may be defined by at least two design parameters one being the depth and one being the width and by a modification design parameter being the slope of the spiral / helix along the length of the conductor.

[0169] The branches defined by the grooves, should preferably have the same impedance / ohmic resistance to ensure an equal current density sharing between the branches.

[0170] The shape of the grooves can in principle have any geometry including V, U square formed geometries, etc. most important is that they are provided to establish branches that has a spiral shape. The shape of the groove may thus be determined by the method used to produce the conductor.

[0171] The multiple grooves may extend at least 95% such as at least 100% of the total perimeter of said conductor (C) between the first position of the conductor (C) and the second position of the conductor (C). It is advantageous to have grooves in a conductor which along the length of the conductor has every position in the perimeter seen in cross-sectional views. When the grooves have every position, it may help to distribute the current more evenly when the conductor is affected by an electromagnetic coupling from another conductor. The grooves may ensure that multiple branches may also have every position in perimeter along the length of the conductor in cross sectional views. It may be advantageous for the electrical current to run through a part of a branch at some point along the conductor and another branch at another part of the conductor. It is advantageous when each branch has approximately the same number of parts where the current is more disposed to run than other parts, which will lead to a more evenly current distribution over the branches for the conductor.

[0172] The position of the groove may be understood as a spiral -like shape of the grove along the length of the conductor. The groove may at the start of the conductor start at one point of the perimeter. At the end of the conductor the groove has been approximately 360 degrees around the perimeter and back to its origin position in the perimeter.

[0173] A groove G may have a depth that is shorter than the distance between the outer perimeter surface and an inner perimeter surface. Such groove that does not go all the way through the material between the outer perimeter surface and the inner perimeter surface is advantageous in that it leaves material towards the inner perimeter surface for mechanical support and creates a closed cavity which may be used for other purposes, e.g. cooling effect. Mechanical support may be prioritized over the consequences of the proximity effect on the free flow of current in the conductor e.g. when the depth of the groove corresponds to or is shorter than the skin depth of the conducted current.

[0174] A groove may extend in the middle section between a first groove point and a second groove point. The first and second groove points should be understood as cross-sections of the conductor. These cross-sections may be coincident with the first and second ends of the conductor or located a distance from these first and second ends.

[0175] The distance between a first groove point and a second groove point may be at least 2.5 times the diameter of the conductor. As the establishing of the groove increases the current path through the conductor, the relationship between the length of the conductor and the diameter of the conductor and thus the perimeter of the conductor should be considered before implementing spiral grooves. Below, the benefit of the spiral groove may be present but may not be significant enough compared to the added DC resistance added by extending the current path to implement the spiral groove.

[0176] One of the plurality of branches defined between two grooves has a width between -30% of the skin depth of the current conducted by the conductor and +30% of the skin depth of the current conducted by the conductor. A theoretic optimal width of a branch may correspond to the skin depth. Hence if the skin depth is 10mm, the width of the branch could be 10mm. Thereby, the current density in the branch is equally distributed. Further, if the depth of the groove and thereby of the branch is also 10mm. Thereby, the branch dimensions is 10mm x 10mm, the current density acrossthe cross-sectional area of the branch is the same and thereby material usage is optimized according to skin depth.

[0177] Obviously, a width not exactly corresponding, such as equal to, the skin depth would also in many implementations be sufficient. Therefore, referring to the example above if the width is + / - 30% of the skin depth, the width could be between 7mm and 13mm. The width may alternatively be below + / - 50% of the skin depth.

[0178] As mentioned, the middle section may be divided in groove sections separated by a short area. A short area separating the two groove sections are advantageous in that it provides mechanical strength to the conductor. The short area may be positioned along the length of the middle segment / conductor where at the optimal location. The optimal location is where the grooves has traveled one time around the conductor perimeter before starting a new spiral. However, only one 360 degrees spiral along the entire length of the conductor is preferred. Thus, having two or more spirals along the length of the conductor increases the current path and thereby increases the resistance. However, for some reason mechanical strength of the conductor may be prioritized over the electric optimum. Such reason could be connection / attachment of the connector in the electric system such as in an electric cabinet. A short area can be established at the same length of a conductor and covering the complete perimeter in a given length. This will provide mechanical strength and stiffness and provide an area which can be used for mounting of the conductor onto external structures via brackets. A short area can also be used for splitting the conductor into two conductors. In this way a long conductor can be manufactured with the intention of subsequent splitting the conductor.

[0179] Fig. 3c illustrates a cross-sectional view of a tubular conductor having grooves G. As mentioned, the depth D can be determined by skin depth caused by the skin effect i.e. based on the percentage of current that is desired to be conducted in the branches and desired to be conducted in center part CP of the conductor. The center part CP is defined by a center perimeter CPE and the inner perimeter IP, where the center perimeter CPE being defined by a virtual line connecting the bottom BO of thegrooves G. In the center part CP the current is in principle free flowing and thus can be pushed or dragged by the proximity effect.

[0180] With reference to fig. 3 c, the cross-sectional area of the conductor material that is conducting current is defined between the inner and outer perimeter IP, OP illustrated as distance DIS in fig. 3 c. With respect to current conducting cross-sectional area, the outer perimeter is defined by what on fig. 3c is referred to as outer perimeter OP, first and second groove sides 1GS, 2GS and groove bottom BO. With respect to the footprint of the conductor the cross-sectional area is defined by what on fig. 3c is referred to as outer perimeter OP. The outer perimeter in this context is defined by the outer perimeter of the conducting material and a virtual line over the grooves as illustrated by a stipulated line in fig 3c.

[0181] The conductor may be designed giving priority to different aspects including flexibility and electric losses. The design of the conductor may be depending on the electric system in which the conductor is to be used, specifically if the conductor has neighbouring conductors or not.

[0182] As mentioned, the depth of the grooves may not need to be deeper than the skin depth to guide sufficient current to achieve the advantages of the present invention. In fact, the depth may be 50%, 60%, 70%, 80% or 90% of the skin dept and still control the current through the conductor sufficiently to achieve the advantages of the present invention.

[0183] Regarding flexibility, this can be added to the conductor by increasing the depth of the groove D. In one extreme, the depth of the groove D equals the distance DIS between inner and outer perimeter. In this situation, the branches B are completely separated by the grooves G and thus isolated from each other by air. In such embodiment the conductor could be extremely flexible and not considered selfsupported. A self-supported conductor would require a diameter of the branches of a certain size. This diameter would be determined e.g. based on length of the conductor, distance between conductor support, requirements in case of shot circuit, etc. Of cause this diameter increases with the length of the conductor. A high degree of flexibilitymay be critical with respect to short of the branches (two neighbouring branches may touch each other) and thereby uncontrolled flow of current between branches could occur which is not desired. Support may be provided by additional brackets and holders.

[0184] To change between flexibility, optimized material usage and mechanic stability, the depth of the grooves may change along the length of the conductor. The deeper groove, the more mechanically flexible conductor. Typically, it is desired to maintain a center part CP, as illustrated in fig. 3c, to maintain mechanical stability of the conductor. It may however, be desired to increase the depth of the groove so that at least part of groove goes through the center part CP. This may be relevant in case a slight tolerance adjustment should be allowed to the diameter of the conductor. The more grooves that are cut all the way through, the higher degree of flexibility / adjustment is allowed. The other way around, some parts of the groove may not be formed into the perimeter of the conductor, such part may be referred to as a virtual groove and may facilitate increased mechanic strength and also the possibility to connect other conductors or components.

[0185] Fig. 4 illustrates an example of a conductor C according to an embodiment of the invention, one or more of such conductors may be used in a multi conductor / multiphase current system. This particular conductor illustrates various variations or features of which some or all may be relevant to implement depending on the system in which the conductor C is to be used.

[0186] Firstly, a short area SA is illustrated dividing the conductor in two groove sections GS. Such short area SA could be located at the ends of grooves that has traveled one turn (360 degrees) or part of one turn around the perimeter of the conductor as illustrated in fig. 4. A short area would typically be located at the first and second ends IE, 2E of the conductor. Short areas SA may also be located between the first and second ends as illustrated. Again, it is preferred if the short areas are located where the spiral grooves have traveled one turn around or part of one turn around the perimeter of the conductor. However, it should be noted, that if mechanicalstrength is prioritized, short areas may be located where required independent on the impact on electric losses uncontrolled location of short areas would cause.

[0187] Branches may be short, by connecting them with a branch connector BC, at predetermined locations along the length of the conductor to provide mechanical strength to the conductor. Alternatively, or in addition, the so-called short areas may be provided along the length of the conductor and / or at the ends IE, 2E of the conductor. It should be mentioned that short of branches may also be provided if a groove does not separate the branches completely. In this case if such short is deeper than the skin dept, the short does not have significant impact on the current flow.

[0188] Branch connectors BC may be provided between two branches like illustrated in fig. 4 and fig. 8. A branch connector BC is preferably located where the open voltage potential is zero or close to zero voltage between the specific physical points of the two branches that are to be connected. In this way, as there is no or very limited voltage different between two branches, no current will flow therebetween. To reduce a current flow between two connected branches further, the diameter or cross-section area of the branch connector could be reduced to a minimum that still provide the required mechanic stability.

[0189] The optimal locations of the branch connectors can be found by calculations, simulations or experiments e.g. based on driving a current through the branches and measure. As mentioned, the currents are high and the voltages between the branches are small (in the range of mA or uA). According, the experimental approach with physical measurements of voltage may be difficult due to access and noise (related to the measure).

[0190] If access through the center of a conductor is required only neighboring branches should be connected with branch connectors. If mechanical stability is prioritized, all zero voltages locations between to branches may be connected.

[0191] A groove may be extending in the middle section MS between a first groove point FGP and a second groove point SGP. The first and second groove points may be points of the conductor or cross-sections of the conductor. These cross-sections maybe coincident with the first and second ends of the conductor or located a distance from these first and second ends.

[0192] Between the two groove points is a distance DIS is found which may be shorter than the distance between the two ends IE, 2E of the conductor. Further, this distance between the two groove points may be longer than 2,5 times the diameter DIA of the conductor.

[0193] To change between flexibility and optimized material usage, the depth of the grooves may change along the length of the conductor. The deeper groove, the more mechanically flexible conductor

[0194] Another way to control flexibility of the conductor is to start the grooves at different distance from an end or from a short area. In this way, wider branches may be divided into sub-branches which will lead to variable flexibility throughout the length of the conductor that could benefit bending and tolerances when connecting to brackets or terminals.

[0195] A depth of a groove between 1% and 100% of the length of a straight line starting at a point of the perimeter, crossing the center of the conductor and ends at an opposing point of the perimeter may be selected, depending on how much of the current that should be allowed to flow freely in the conductor. By flow freely should be understood as allowed to be pulled or pushed e.g. by electromagnetic coupling phenomenon (proximity effect) from one side or part of the conductor to another side or part of the conductor.

[0196] The width W of a groove may not be important with respect to control the current in the branches. In principle, a groove can be as thin as possible to manufacture. However, in practice, to ensure that branches on each side of the groove do not short in case of movement of the conductor, the groove may be between 0,5mm and 5mm such as 1mm to 2mm.

[0197] In some cases, the conductor i.e. the outer perimeter as explained above may be provided with an isolating material. This is especially relevant if the conductorwhen mounted is able to flex so much that there is a risk of two branches could touch and thereby short. Insulation material may be applied to the conductor itself, or it may be in the shape of a separate body / part being placed or adapted onto the conductor. Such part may be applied only into the groove to ensure separation of the branches during flexing of the conductor, while not isolating the rest of the outer perimeter.

[0198] A conductor according to the invention may be provided by extrusion and may be optimized for mechanical strength and cooling. Hence the grooves are spaced all the way to the center of these conductors facilitating improved cooling.

[0199] An example is a conductor that comprises a center conductor part having a center perimeter CPE defined by the bottoms of a plurality of grooves. The width of branches defined by the grooves is larger at the outer perimeter surface than at the center perimeter CPE. Also, the conductor is able to conduct a cooling fluid inside the center defined by the inner perimeter.

[0200] In an embodiment, the electric conductor comprises a center conductor part having a center perimeter partly defined by bottoms of a plurality of grooves. Further in an embodiment, the plurality of grooves is forming the plurality of branches so that the width of at least part of the plurality of branches is larger at the outer perimeter surface than at the center conductor perimeter. A conductor may be formed with branches having a width W measured between groove sides (measure in a cross-sectional cut see fig. 3c.) which towards the outer perimeter of the conductor has a first measure and towards the center perimeter has a second measure where the first measure is larger than the second measure. Such conductor is advantageous in that the cross-sectional area of the part of the branch where most current is conducted due to skin depth is largest.

[0201] A conductor may have a hollow center without a center part. Instead the branches are partly hollow and no center part that can conduct a current. If the conductor has a hollow center part, the grooves or protrusions may be provided into / onto the inner perimeter or in combination with grooves provided into / onto the outer perimeter. The preferred implementation to date is as a groove.

[0202] As mentioned, the branches are defined by the grooves. Thus, when the grooves are spiral / helix grooves along the length of the conductor, the branches also become spiral / helix branches along the length of the conductor.

[0203] The grooves may design the branches with an equal resistance to ensure as uniform voltage over each branch as possible and thereby as equal current distribution between the branches as possible. In many cases an equal resistance / impedance would also result in a similar design or geometry. With this said, it may be relevant to design the branches with different geometry to ensure same resistance / impedance. This may be the situation e.g. if the conductor should bend. In such bend an outer branch is longer than an inner branch and the same applies for the outer perimeter compared the inner perimeter of bend branches. Hence, to compensate for this difference in current path, the geometry may be different to maintain the same resistance / impedance.

[0204] The grooves may be provided into the perimeter of the conductor e.g. by extrusion, removal or addition of material. As the impedance in a branch / conductor is decreasing towards its perimeter the branch can be made with a larger cross-sectional area towards the outer perimeter of the total cross-section of the conductor. The grooves may be designed to provide a branch that is oval or drop-shaped.

[0205] A conductor with branches can be manufactured by adding material as mentioned above. Addition of material could be to a thin pipe thereby forming the branches onto this pipe. Thereby no removal of material is needed, and thus higher utilisation of material is obtained.

[0206] A conductor with grooves according to the present invention may be used in high power / high current systems where currents above 100A, such as above 500A, such as above 1000A are used and even above 10.000A. Further, the physical distances in such system should exceed 30cm i.e. a conductor of at least 30cm should be needed to connect two components of the system. Alternatively, or in addition, a routing distance from a terminal to a component in such system should be at least 30cm. This 30cm limit is not fixed, it is an example of a relationship between length and diameter of the conductor. Hence, a typical minimum distance for a conductor of the presentinvention could be a length of three times the diameter of the current conducting diameter of the conductor.

[0207] Examples of systems requiring conducing e.g. +1000 A over a routing distance of + 30cm include electric systems such as or including power converter, reactors, switch gear, power distribution systems, etc. Also power supply to e.g. electrolysis stacks that need high power to produce hydrogen may be supplied at least partly from conductors according to the present invention.

[0208] The conductor of the present invention may, as indicated above, have one or more middle sections with spiral grooves. As mentioned, it may be advantageous if the spiral takes one 360 degrees turn over a predetermined distance, however as also mentioned, less (or more) can do. With knowledge of the system in which the conductor of the present invention is to be used, it is possible to design the different parts of the conductor with 90, 180, 360 or whatever degree turn of the spiral branches / groves over a given length of the conductor / middle section. The location of the conductor in the system is determining for the design of the branches. Hence, if two conductors are within a range of e.g. 1cm to 50cm such as within 40cm, 30c, 20cm or 10cm of each other, the spiral grooves are preferred. Also, the length the two conductors are having this mutual distance is determining for the design of the branches. Hence, if one conductor turns and thus have no immediate neighbour, the branches may not be needed. Fixture and end piece

[0209] The conductor may be self-supported and thus be mounted in an electric system by simple connection of its ends to electric components. Between its ends, the conductor may be configured for being fastened to a support structure at one or more fastening areas.

[0210] The conductor may as mentioned end in a short area. Such short areas may provide a fixed structure to which an end piece can be connected. Such end piece may facilitate connection of the conductor to an electric component. The end piece facilitating this should have means such as surfaces, holes, thread part or the like to facilitate connection to an electric. The end piece and the conductor end to which it isto be connected may comprise divergent portions. Divergent portions should be understood as a non-planer structure. When both the end piece and the conductor end has matching divergent portions, an improved electric connection therebetween is established due to the engagement between these divergent portions.

[0211] It should be noted that the individual branches may be terminated individually or in groups of two or more individual branches. Such termination could be similar to what has been described above.

[0212] According to an embodiment, the step of establishing the design parameter and / or the modified design parameter include establishing a digital representation of the design parameter and / or the modified design. A digital representation of these parameters is advantageous in that it has the effect, that a 3D visualisation of the electric conductor can be established. Further, it is advantageous in that it becomes possible to simulate the effect of controlling the internal and external electromagnetic effects i.e. the skin and proximity effects. Further it is advantageous in that it becomes possible to provide an apparatus for producing the electric conductor with 3D information of the electromagnetic effect control elements i.e. in embodiments the grooves.

[0213] Different methods of manufacturing a conductor with grooves according to the present invention exists. One would be extrusion, another one would be laser or waterjet cutting and yet another would be milling. Grooves may be applied to a tube or to a sheet material, which is then formed into a tube by e.g. rolling and welding. Additive manufacturing is of course a possibility however, it is not the preferred to the length of the conductor.

[0214] Fig. 5 illustrates an embodiment of the invention where two phase currents are conducted in a multi-phase conductor system, where a first phase current (FPC) is being conducted by at least one conductor (C) and a second phase current (SPC) is being conducted by an additional conductor (2C). The phase current of the two conductors are shared between the individual phase conductors thereof.

[0215] The at least one conductor (C) is illustrated with a first end (IE) and a second end (2E) with a middle section (MS) in between the two ends. The at least one conductor (C) is shown with two individual phase conductors (IPC), where each individual phase conductor (IPC) comprises 7 grooves (G) and 7 branches (B). The individual phase conductors (IPC) are mechanically and electronically connected at the first end (IE) and the second end (2E) of the at least one conductor (C). The number of grooves and branches of the individual phase conductors may in other embodiments of the invention be any kind of number of grooves and branches from 2 and up to 100, especially 5-20.

[0216] As long as the number of grooves is considerable such as around 50 or below 35 or between 10 and 20 the direction of the rotation of the grooves is not of high importance. When the number of grooves is limited such as below 10 the direction of rotation of the grooves may have impact. However, when only a few grooves are present and two conductors are located nearby each other it may optimize the effect of the grooves if the grooves in one of the conductors is rotated clockwise and in the other counter clockwise. Depending on the direction of the current and the direction of rotation, the electromagnetic field may be angled or parallel to each other. If angled and going towards perpendicular, the coupling effect is limited compared to a parallel situation. Thus, it is desired to facilitate angled / perpendicular directions of current to reduce coupling.

[0217] The additional conductor (2C) is, as the conductor C, illustrated with two individual phase conductors (IPC) with a first end (IE) and a second end (2E) and with a middle section (MS) in between the two ends.

[0218] The individual phase conductors (IPC) are illustrated as longitudinal pipes but may in other embodiments be rectangular or other shapes which fits the space available. The individual phase conductors (IPC) are illustrated as straight conductors but may in some embodiments be angled (not shown) according to electrically connect two parts. The individual phase conductors may in some embodiments switch place with each other be twisting or turning the individual phase conductors of the same conductor around each other. It may be advantageous to switch place for the individualphase conductors to optimize the sharing of an electrical current due to skin and proximity effect. This is to maintain sharing of the phase current i.e. to mitigate the consequences of the electromagnetic coupling effect.

[0219] The conductors may not be limited to two individual phase conductors but may in other embodiments comprise three or more individual phase conductors when higher phase currents are to be conducted.

[0220] Each conductor is illustrated with two individual phase conductors IPC due to an amount of electrical current which is to be conducted. The number of individual phase conductors may be adjusted depending on the amount of electrical current the conductor has to be able to conduct.

[0221] One individual phase conductor of the conductor may affect the other individual phase conductor of the same conductor by the proximity effect. The other individual phase conductor may similarly affect the one individual phase conductor at the same time by the proximity effect. The individual phase conductors of the at least one conductor may also affect the individual phase conductors of the additional conductor by the proximity effect and vice versa. One individual phase conductor may be affected by multiple electromagnetic fields from other individual phase conductors in the multi -conductor system. The grooves provide a more even current distribution for the individual phase conductors despite being influenced by multiple electromagnetic, fields from other individual phase conductors.

[0222] The conductors may be mechanically and electrically connected to electrical components to conduct a first phase current and a second phase current. Further, if the electric system in which the at least two conductors are implemented requires more phase currents, more conductors are provided.

[0223] Fig. 6 illustrates three conductors implemented as tubular busbars also referred to as power tubes. The tubular busbars are illustrated as similar to the individual phase conductors of fig. 5 with multiple grooves (G) and multiple branches (B). The tubular busbars have a first end (IE) and a second end (2E) with a middle section (MS) in between. The tubular busbars are illustrated with a hollow inner partand the branches (B) connected at the first end (IE) and the second end (2E). The three tubular busbars may be setup in a multi conductor system, where the same phase current is being conducted by the three illustrated tubular busbars, but may also be used in a multi-phase conductor system where each of the illustrated tubular busbars is conducting an individual phase current. No matter implementation of the conductors in the sysetm, the current conducted therethrough is shared between individual branches of the conductors. The tubular busbars may in a configuration (not shown) be placed conducting a phase current where the three tubular busbars are stacked as a pyramid or triangle with one busbar on top of the other two seen from an end perspective.

[0224] Electromagnetic coupling effect from the three illustrated tubular conductors mutually influences each other. Hence, the first is influenced by proximity effect from the second and third and so on. To further reduce the proximity effect it may be advantageous to have the first conductor and the third conductor to twist 180 degrees around the second conductor in the middle. The electrical current may be more evenly distributed along the three conductors by having the two outer conductors shift place.

[0225] To mitigate the drawback of the proximity effect i.e. the uneven distribution of current in the conductors they are equipped with helix grooves. Thereby it is ensured that a more even distribution of the electrical current through the three conductors are achieved.

[0226] The tubular busbars illustrated in fig. 6 may be used similarly as in the multi conductor system illustrated in e.g., fig. 1 or multi-phase conductor system in e.g., fig.5.

[0227] Fig. 7a illustrates three conductors, where each conductor comprises three individual phase conductors (IPC). The conductor 2C in the middle of the three conductors is turned upside down compared to the other two conductors to minimize the proximity effect from neighbouring conductors. By turning the conductor 2C 180 degrees seen from an end perspective it reduces the proximity effect from the neighbouring conductors. At the same time the proximity effects the conductor 2C inthe middle affects the additional conductors by is also reduced. The proximity effect is reduced due to a more symmetric conductor system MC because the total sum of proximity effect pulls less in the electrical current. Some of the proximity effects may have opposite directed coordinates in one direction which may reduce the total proximity effect. When seeing the three conductors from an end perspective the multi conductor system is illustrated in fig. 7b with five individual phase conductors on top of four individual phase conductors in the bottom when the conductor 2C in the middle is turned 180 degrees. In an embodiment where the conductor 2C in the middle would be placed like the other two conductors (not shown) the ratio would be six individual phase conductors on top and three individual phase conductors in the bottom. The middle conductor is illustrated as an additional conductor (2C).

[0228] The individual phase conductors are illustrated in approximately an equilateral triangle for minimizing the proximity effect along the phase conductor. The proximity effect from the electromagnetic fields from two neighbouring individual phase conductors (from same conductor) may be more efficiently reduced when all three individual phase conductors share the same distance to one another. This is because the total sum of the proximity effects a conductor is pulled by from other conductors has a tendency to cancels each other more out.

[0229] The conductors are all illustrated with grooves (G) and branches (B) to optimize and maintain a sharing of the electrical current in the branches (B) and thus in the individual phase conductors (IPC). The number of grooves and branches may vary depending on the setup of the multi-phase conductor system e.g., more grooves may be added when more flexible conductors may be used.

[0230] In other embodiments of the invention the three conductors may comprise four or more individual phase conductors each (not shown) e.g. if a higher electrical current is to be conducted. The number of individual phase conductors may typically depend on the need for conducting a specific electrical current. Further it may also depend on how much space is available where the three conductors are to be used.

[0231] Fig. 8a illustrates a multi conductor system MC according to an embodiment of the invention. This multi conductor system MC comprise four sub-groups SG each of which comprises four individual phase conductors IPC. These sub-groups SG are comparable to the conductor C / second conductor 2C, each comprising individual phase conductors IPC, illustrated e.g. in fig. 5 and 7. Hence, with reference to fig. 7, the illustrated multi conductor system MC of fig. 8a is comparable to the conductor C of fig. 7. The individual phase conductors IPC of each sub-group SG are twisted along the length of the longitudinal axis of the multi conductor system MC from a first end IE to a second end 2E.

[0232] The number of sub-groups is illustrated as four each with a terminal TE comprising terminal holes TH for connection of the sub-group SG to an electric component of an electrical system in which the multi conductor system is connectable to. The number of sub-groups SG and the number of individual phase conductors IPC may vary according to the embodiment of the invention depending on e.g., the magnitude of the phase current to be conducted in the multi conductor system MC.

[0233] The sub-groups may in an embodiment be twisted around both themselves and a centre axis along the length of the conductor as illustrated in fig. 9.

[0234] As mentioned, the multi conductor system MC of fig. 8a comprises four subgroups SG (also referred to as conductors C) each of which comprising four individual phase conductors IPC. The multi conductor system MC comprises a displaced first end i.e. two of the sub-groups SG ends a distance longer away from the second end 2E than two other of the sub-groups SG. This is because, this particular multi conductor system MC at its first end is connectable to two electric components e.g. in the form of busbars. Thus, the phase current from the two parallel busbars is collected and conducted by the illustrated multi conductor system MC to an electric component connected to its second end 2E. Such electric component could be a switchgear, power module, breaker or similar.

[0235] The connection of the multi conductor system MC to the busbars is made via the terminal holes TH in the terminals TE. Accordingly, the busbars may havematching holes through which bolts can be provided for fastening the multi conductor system MC to the busbars.

[0236] Fig. 8b illustrates an end view of the multi conductor system MC illustrated in fig. 8a. From this figure it is possible to see the four second end terminals TE of the four sub-groups and two of the first end terminals TE. The illustrated multi conductor system MC design is advantageous in that mounting of the second end terminals can be made through the center of the multi conductor system MC. Thus, the internal terminals and access hereto via the center of the multi conductor system MC results in that the footprint of the multi conductor system MC is reduced i.e. a compact multi conductor system MC is provided.

[0237] Returning to fig. 8a it should be mentioned that the individual phase conductors IPC of the sub-groups may not have the same dimensions. Hence, in case the phase current should be run from the second end 2E and into the busbars connected to the first end IE. In that case it may be advantageous to change the ohmic resistance in the sub-groups to thereby control by design the amount of the phase current that is running into each individual of the four sub-groups. This is especially relevant when, as illustrated in fig. 8a, the length of the sub-groups between first and second ends IE, 2E in that the length is one element in determining the ohmic resistance of a current path and thereby how much of a total current that is conductor therein.

[0238] The grooves G of the multi conductor system MC of fig. 8a is provided as the distance / air gap between the individual phase conductors IPC of the sub-groups. As with other designs of the multi conductor system MC, these air gaps ensure that once current has entered one of the individual phase conductors IPC, it stays in that phase conductor IPC from the first end IE to the second end 2E.

[0239] With this said, the individual phase conductors IPC of the sub-groups SG and individual phase conductors of different sub-groups may be connected with branch connectors BC. The main purpose of the branch connectors BS is to provide mechanical stability to the multi conductor system MC and to ensure that theindividual phase conductors IPC do not make uncontrolled contact and thereby allow current to “jump” from one individual phase conductor to another.

[0240] In fig. 9 another embodiment of the invention is illustrated which is comparable to the embodiment illustrated in fig. 8a. The difference is that in fig. 9, the individual phase conductors of a sub-group are also twisted while the sub-groups are twisted around each other. Hence, in fig. 9, the individual phase conductors (IPC) are twisted and turned along the length of the conductor from a first end (IE) to a second end (2E) and the individual phase conductors (IPC) are twisted around themselves along the same direction. The four sub-groups SGI, SG2, SG3, SG4 of the illustrated multi conductor system MC i.e. the four conductors Cl, C2, C3, C4, comprises with four terminals TE at the first end (IE) and two terminals TE at the middle section (MS) and two terminals TE at the second end (2E). Note, that the two terminals TE at the middle section MS of fig. 9 are in fig. 8 refereed to a displaced end terminal. The number of conductors, individual phase conductors, sub-groups, terminals and twist / turns may be design according to different mechanically and electrically setups, where a system may facilitate a sharing of an electrical current.

[0241] It should be noted, that the multi conductor system MC illustrated in fig 8a and 9 are conducting the same phase current. Hence, a three phased system would require three multi conductor system MC as the one illustrated.

[0242] Further, the multi conductor system MC of fig. 8a and 9 are examples of the proximity effect also applies among conductors of the same phase current.

[0243] Fig. 10 illustrates a conductor C with two individual phase conductors IPC1, IPC2. The conductor C is illustrated with a first end IE, a second end 2E and a middle section MS between the first end IE and the second end 2E. The conductor C has a centre axis CA in the middle of the two individual phase conductors IPC extending from the first end IE to the second end 2E. In the middle section MS the first individual phase conductor IPC1 and the second individual phase conductor IPC2 is illustrated with branches B and grooves G. The first individual phase conductor IPC1 is in the second end 2E surrounding the second individual phase conductor IPC2. In the middlesection MS the first individual phase conductor IPC1 branches from an outside position related to the second individual phase conductor IPC2 to an inside position when seen from the second end 2E to the first end IE. In the middle section MS the second individual phase conductor IPC2 branches off from and inside position related to the first individual phase conductor IPC1 to an outside position when seen from the second end 2E to the first end IE. In the second end 2E of the conductor C the second individual phase conductor IPC2 is surrounding the first individual phase conductor IPC1. The first conductor FC has a second radial distance SRD to the centre axis CA at the first end IE and the second individual phase conductor IPC2 has a first radial distance FRD to the centre axis CA at the second end 2E (not illustrated). The first radial distance FRD may in some embodiments be measured at the first end, the second end or at the middle section (not shown). In some embodiments the first radial distance and the second radial distance may have the same length. The first radial distance may be measured from the centre axis CA to the inner surface / perimeter of the second individual phase conductor IPC2. Similar, the second radial distance SRD may be measured from the centre axis CA to the inner surface / perimeter of the first individual phase conductor IPC1. The first and second radial distance may in other embodiments be measured from the centre axis to the outer surface / perimeter of the individual phase conductor or a point between the surfaces of the individual phase conductor. When the individual phase conductors are roundly shaped the radial distance may be the same in any direction from the centre to the individual phase conductor. For other shapes / geometries like a square or oval individual phase conductor the first radial distance may be measured as an average value to e.g., the inner surface of the individual phase conductor in a 360 degrees turn.

[0244] The first individual phase conductor and the individual phase second conductor are illustrated enclosing the same centre axis along the conductor. The two individual phase conductors are isolated from each other at all the way along the conductor to ensure two individual current paths. The individual phase conductors have to be isolated from each other to facilitate a sharing of an electrical current due to the effect of the skin effect. To facilitate such sharing, the two individual phaseconductors should have the same resistance which then can facilitate an optimal current path in both of the two individual phase conductors.

[0245] The conductor may be implemented in different kinds of setups. Depending on whether the conductor is used in a stable or more turbulent environment the radial distance of the individual phase conductor may vary. Typically, the radial distance may be longer, e.g., the radius of the individual phase conductor may be enlarged to increase stability of the individual phase conductor. The individual phase conductors may vary in radius from 3mm to 20cm. The individual phase conductors may be monolithically made in one piece. When being made in one piece the individual phase conductors may e.g., be made by additive manufacturing, moulding, extrusion or casted.

[0246] In some embodiments of the invention the individual phase conductor being enclosed by another individual phase conductor may be a massive individual phase conductor. The massive individual phase conductor may at some part of the conductor be aligned with the centre axis. The enclosed massive individual phase conductor may be made with or without grooves in the surface. The massive individual phase conductor could be a solid rod made of copper or aluminium.

[0247] In the middle section MS in fig. 10 the two individual phase conductors are illustrated with multiple branches BR with airgaps G between the branches BR. The airgaps G between the branches BR of the first conductor FC are used for the branches BR of the second individual phase conductor IPC2 and vice versa for the branches BR of the first individual phase conductor IPC1 in the airgaps between the branches BR of the second individual phase conductor IPC2. When referring to used for, a reference is made to used for changing radial position of the two individual phase conductors. The number of branches for each individual phase conductor may vary from two and up depending on the mechanical or electrical design needed for the conductor.

[0248] The change in radial position for the individual phase conductors along the conductor may help facilitate an equal sharing of an electrical current through the conductor. When changing the positions of the individual phase conductors it mayreduce the effect of the skin effect occurring from the electromagnetic fields from the individual phase conductors. The individual phase conductors affect each other with their respective electromagnetic fields along the conductor. The electromagnetic fields are generated when an AC current is conducted in a conductor.

[0249] If the individual phase conductors did not change position i.e. change radial positions the outermost individual phase conductor would be preferred by the electrical current due to the skin effect occurring from the electromagnetic fields of the individual phase conductors. Hence, with a conductor of the present invention having individual phase conductors changing radial position relative to the center axis of the conductor this problem is solved. At the first end of the conductor the electromagnetic fields and thereby the skin effect will have the electrical current to prefer the first one of the individual phase conductors most far away from the center axis i.e. the first individual phase conductor IPC1. When looking at the second end of the conductor, due to the changing the positions of the individual phase conductors in the middle section, the electrical current would in the second end prefer to be conducted in the other individual phase conductor of the conductor i.e. in the second individual phase conductor IPC2. Therefore, due to the changing of position, the electrical current will not prefer one individual phase conductor over the other individual phase conductor when the electrical current is to be conducted through the entire conductor from the first end to the second end.

[0250] In an embodiment of the invention, the number of grooves in a cross-sectional area of the electric conductor is below 125, such as below 100, such as between 3 and 50. A preferred number of grooves in the electric conductor is closely related to the perimeter of the electric conductor and to the frequency of the current that is conducted. The higher frequency the smaller skin depth and thus a higher number of grooves could be made. On the other hand, if the grooves are made by removing material of the conductor, then the higher number of grooves, the higher waste of material (depending om manufacturing method). Accordingly, the number of grooves may be a trade-off between utilization of conductor material and conductor material waste.

[0251] In an embodiment of the invention, the depth of the groove is measured along a straight line perpendicular to a tangent of an outer perimeter of the conductor. In case the conductor is spheric, including e.g. a tubular geometry, the depth could be measured along a straight line from the circumference of the conductor to the centre of the conductor (i.e. as part of the radius). In case the conductor is square or rectangular, the depth could be measured along a straight line from the perimeter of the conductor to a centre axis of the conductor.

[0252] In an embodiment of the invention, the depth of the grooves is at least equal to a calculated skin depth of the current conducted by the conductor. A groove depth equal to the skin depth is advantageous in that a limited amount of the total current conducted by the conductor is able to flow freely in the conductor and thereby exposed to the proximity effect from a neighbouring conductor.

[0253] In an embodiment of the invention, the depth of the grooves exceeds the skin depth of the current conducted by the conductor. A groove depth exceeding the skin depth is advantageous in that it reduces the consequence of the proximity effect from a neighbouring conductor in that no current at all can flow from one branch to another.

[0254] In an embodiment of the invention, the at least one groove has a first depth, wherein at least a second groove has a second depth, and wherein the first depth and the second depth are different.

[0255] In an embodiment of the invention, the at least one groove has a depth larger than the distance between an outer perimeter surface and an inner perimeter surface in a cross-sectional view of the electric conductor. Providing grooves that go all the way through the conductor is advantageous in that it has the effect that the perimeter of this part of the conductor can be flexed upon being applied to by an external force. Hence, this part may be elastically deformable so that it is easier to meet tolerance e.g. when connecting the conductor to an end piece, connection piece, or to a component.

[0256] In an embodiment of the invention, the at least one groove has a depth corresponding to the distance between the outer perimeter surface and an inner perimeter surface. A groove depth corresponding to the distance between inner andouter perimeter is advantageous in that it has the effect that no current flows freely between the two branches separated by the groove in that these two branches are separated by an air gap.

[0257] In an embodiment of the invention, at least two grooves have different geometry. Different geometry of grooves may result in different geometry of the branches formed by these grooves. This may be advantageous to ensure same resistance in the branches if e.g. the conductor is bending thereby increasing the distance at the outer curve of the bend compared to the inner curve of the bend.

[0258] In an embodiment of the invention, the distance between a first groove point and a second groove point is at least 25% of the distance between the first end and the second end.

[0259] In an embodiment of the invention, the slope of the at least one groove is determined by the distance between a first groove point and a second groove point so that the at least one groove travels at least 90 degrees around the outer perimeter of the conductor between the first groove point and the second groove point, wherein the distance between the first groove point and the second groove point is at least 2.5 times the diameter of the conductor.

[0260] In an embodiment of the invention, the geometry of the electric conductor is selected from the list comprising: tubular, cylindrical, rectangular, square and oval.

[0261] In an embodiment of the invention, the electric conductor comprises a contact surface. A contact surface such as a planar surface of a circular conductor is advantageous in that it has the effect that other conductors, terminals, components, etc. can be connected at the contact surface.

[0262] In an embodiment of the invention, the thickness of a rectangular conductor is at least 10mm. Such current conducting thicknesses are advantageous in that currents of above 100A such as above 250A can be conducted by the conductor.

[0263] In an embodiment of the invention, a part of the conductor comprises a divergent portion. A divergent portion is advantageous in that if it matches anothercomponent such as an end part, the connection between the end part and the divergent portion is optimized from an electric point of view.

[0264] In an embodiment of the invention, the first and second branches are neighbouring branches. This is advantageous in that it has the effect that the center of the conductor is free of branch connectors allowing a tool to be used through the center of the conductor.

[0265] In an embodiment of the invention, the branch connector is of an electric conductive material. The branch connector may be of the same material as the branches, thereby establishing an electric current path across the groove.

[0266] In an embodiment of the invention, the step of establishing the electric conductor with the electromagnetic effect control element is implemented by extrusion. Extrusion is advantageous in that it is a fast, cheap and proven method of establishing electric conductors. The electromagnetic effect control element can be provided in the perimeter by protrusions at the extrusion outlet.ListC. ConductorIE. First conductor end2E. Second conductor end IPC. Individual phase conductor MS. Middle sectionMC. Multi conductor system PC. Phase currentG. GrooveBO. Bottom (of groove)D. Depth (of groove)1GS. First groove side2GS. Second groove sideB. BranchCP. Center partCPE. Center perimeterIP. Inner perimeterOP. Outer perimeterBC. Branch connectors DIS. DistanceCA. Centre AxisFGP. First Groove Point SGP. Second Groove Point DIA. Diameter of Conductor W. WidthGS. Groove SectionSA Short areaFPC First phase currentSPC Second phase current TE TerminalTH Terminal holesSG Sub-group

Claims

Claims1. A multi conductor system (MC) comprising at least two conductors,wherein at least one conductor (C) of the at least two conductors comprising multiple grooves (G) forming multiple branches (B), wherein the multiple branches (B) are designed to facilitate sharing of a phase current (PC), among the multiple branches (B), when said conductor (C) is conducting the phase current (PC), andwherein the design of the multiple branches (B) furthermore is configured to maintain the sharing of said phase current (PC) when an electromagnetic coupling effect (ECE) from an additional conductor (2C) of said at least two conductors impacts the conductor (C).

2. A multi conductor system (MC) according to claim 1, wherein a distance between the at least one conductor (C) and the additional conductor (2C) is equal to or less than 50 times a width of the at least one conductor (C), such as 25 times the width of the at least one conductor (C), such as 10 times width of the at least one conductor (C).

3. A multi conductor system according to any one of claims 1 and 2, wherein the at least one electric conductor (C) comprises a first end (IE), a second end (2E) and a middle section (MS) provided between the first end (IE) and the second end (2E), wherein the middle section (MS) comprises said multiple grooves (G).

4. A multi conductor system according to any of the preceding claims, wherein said at least one conductor (C) is a tubular conductor.

5. A multi conductor system according to any of the preceding claims, wherein all of said at least two conductors in said multi conductor system (MC) are tubular conductors.

6. A multi conductor system according to any of the preceding claims, wherein said at least one conductor (C) is angled according to a longitudinal direction of said at least one conductor (C), wherein said angle is different from zero.

7. A multi conductor system according to any of the preceding claims, wherein the width of each of said multiple grooves (G) are between 0,1mm and 5mm.

8. A multi conductor system according to claim 3, wherein said multiple grooves (G) extends between said first end (IE) of the at least one conductor (C) and a second end (2E) of the at least one conductor (C) in said middle section (MS).

9. A multi conductor system according to any of the preceding claims, wherein the depth of at least one of said multiple grooves (G) is between 5% and 100% of the skin depth of the current conducted by the at least one conductor (C).

10. A multi conductor system according to any of the preceding claims, wherein at least one of said multiple grooves (G) has a varying depth.

11. A multi conductor system according to any of the preceding claims, wherein the slope of at least one of said multiple grooves (G) is varying.

12. A multi conductor system according to any of the preceding claims, wherein said multiple grooves (G) has a width equal to or less than the width of said multiple branches (B).

13. A multi conductor system according to any of the preceding claims, wherein said multiple grooves (G) have a width equal to or greater than the width of said multiple branches (B).

14. A multi conductor system according to any of the preceding claims, wherein at least one of said multiple grooves (G) has extended at least 50% of the total perimeter of said conductor (C) between a first groove point (FGP) of said conductor (C) and a second groove point (SGP) of said conductor (C).

15. A multi conductor system according to any of the preceding claims, wherein said sharing is a sharing of said total electrical current through said at least one conductor (C) divided by the number of said multiple branches (B).

16. A multi conductor system according to any of the preceding claims, wherein said multiple grooves (G) is forming the multiple branches (B) so that the resistance of the multiple branches (B) is the same.

17. A multi conductor system according to any of the preceding claims, wherein at least one branch of said multiple branches (B) has a different length compared to the rest of said multiple branches (B).

18. A multi conductor system according to any of the preceding claims, wherein at least one of said multiple grooves (G) are uniform.

19. A multi conductor system according to any of the preceding claims, wherein said multiple grooves (G) are airgaps in said conductor (C).

20. A multi conductor system according to any of the preceding claims, wherein said multiple grooves (G) extend from one terminal of said at least one conductor (C) to a second terminal of said conductor (C).

21. A multi conductor system according to any of the preceding claims, wherein said plurality branches (B) meet towards at least one of the first end (IE) and the second end (2E) of said at least one conductor (C).

22. A multi conductor system according to any of the preceding claims, wherein at least two neighbouring branches of said multiple branches (B) are connected by a branch connector (BC), the branch connector (BC) establishes a connection across at least one of said multiple grooves (G) from the first groove side to the second groove side of the groove.

23. A multi conductor system according to any of the preceding claims, wherein the branch connector (BC) is connecting the first and second groove sides at the location along the middle section, where an open voltage potential difference between a first branch and a second branch is 0V.

24. A multi conductor system according to any of the preceding claims, wherein the diameter of the branch connector (BC) is below 10mm, such as below 5mm, preferably below 2mm.

25. A multi conductor system according to any of the preceding claims, wherein all of said multiple branches (B) are connected by branch connectors (BC).

26. A multi conductor system according to any of the preceding claims, wherein said multiple grooves (G) travels around the outer perimeter of the at least one conductor (C), thereby forming the multiple branches (B) as spiral branches.

27. A multi conductor system according to any of the preceding claims, wherein at least one groove of said multiple grooves (G) is traveling between 90 degrees and 360 degrees around the outer perimeter of the at least one conductor (C) between a first groove point (FGP) and a second groove point (SGP).

28. A multi conductor system according to any of the preceding claims, wherein at least one groove of said multiple grooves (G) is formed as a continuous groove or as a stepwise groove in the outer perimeter of the at least one conductor (C).

29. A multi conductor system according to any of the preceding claims, wherein at least one groove of said multiple grooves (G) only partly extends between the first and second ends (IE, 2E) of the at least one conductor (C).

30. A multi conductor system according to any of the preceding claims, wherein the electric conductor with the electromagnetic effect control element is produced by one of the list comprising casting, milling, and additive manufacturing.

31. A multi conductor system according to any of the preceding claims, wherein said at least one conductor (C) comprises at least two individual phase conductors (IPC), wherein said at least two individual phase conductors (IPC) comprises multiple grooves (G) forming multiple branches (B).

32. A multi conductor system according to any of the preceding claims, wherein said at least two individual phase conductors (IPC) are arranged in a side-by-side configuration.

33. A multi conductor system according to any of the preceding claims, wherein said at least two conductors are electrically connected and positioned side by side.

34. A multi conductor system according to any of the preceding claims, wherein said multi conductor system (MC) is a multi-phase conductor system, wherein said at least one conductor (C) is configured to conduct a first phase current (FPC) and said additional conductor (2C) is configured to conduct a second phase current (SPC).

35. A multi conductor system according to any of the preceding claims, wherein said additional conductor (2C) comprises at least two individual phase conductors (IPC).

36. A multi conductor system according to any of the preceding claims, wherein said multi-phase conductor system comprises a third conductor (3C) wherein said third conductor (3C) comprises at least two individual phase conductors (IPC), wherein said third conductor (3C) is configured to conduct a third phase current (TPC).

37. A multi conductor system according to any of the preceding claims, wherein the individual phase conductors (IPC) of said at least one conductor (C), said additional conductor (2C) and said third conductor (3C) are placed side by side.

38. A multi conductor system according to any of the preceding claims, wherein said at least one conductor (C), said additional conductor (2C) and said third conductor (3C) each comprises three individual phase conductors (IPC).

39. A multi conductor system according to any of the preceding claims, wherein said at least one conductor (C), said additional conductor (2C) and said third conductor (3C) each comprises three individual phase conductors (IPC), wherein the distances between the centers of said three individual conductors are the same.

40. A multi conductor system according to any of the preceding claims, wherein the at least individual phase conductors (IPC) in one of said at least two conductors, are having different length.

41. A multi conductor system according to any of the preceding claims, wherein said at least two individual phase conductors (IPC) of said at least one conductor (C) are grouped into a plurality of sub-groups (SG).

42. A multi conductor system according to any of the preceding claims, wherein said plurality of sub-groups (SG) is changing positions along the longitudinal length of said at least one conductor (C).

43. A multi conductor system according to any of the preceding claims, wherein the at least two individual phase conductors of said additional conductor (2C) and said third conductor (3C) are grouped into a plurality of sub-groups (SG).

44. A multi conductor system according to any of the preceding claims, wherein said plurality of sub-groups (SG) of said at least one conductor (C), said additional conductor (2C), and said third conductor (3C) are changing positions along the longitudinal length of said at least one conductor (C), said additional conductor (2C), and said third conductor (3C).

45. A multi conductor system according to any of the preceding claims, wherein said at least two conductors are designed with multiple grooves (G), where said design is different for at least two of said at least two conductors.

46. A multi conductor system according to any of the preceding claims, wherein a first of said at least two individual phase conductors (IPC1) is designed to comprise a second of said at least two individual phase conductors (IPC2) inside at some point along the at least one conductor (C).

47. A multi conductor system according to any of the preceding claims, wherein said first and second individual phase conductors (IPC1, IPC2) are designed to switch place with each other at said middle section (MS)48. A multi conductor system according to any of the preceding claims, wherein the at least one groove is a virtual groove.

49. A multi conductor system according to any of the preceding claims, wherein at least a first of a plurality of grooves start a first distance from the first end of the conductor, wherein at least a second of the plurality of grooves start a second distance from the first end of the conductor and wherein the first and second distance are different.

50. A multi conductor system according to any of the preceding claims, wherein at least one of the multiple branches defined between two grooves has a width between -30% of the skin depth of the current conducted by the conductor and +30% of the skin depth of the current conducted by the conductor.

51. A multi conductor system according to any of the preceding claims, wherein the at least one groove is filled with a filling material selected from the list comprising: epoxy, polymer, coating and varnish.

52. A multi conductor system according to any of the preceding claims, wherein the at least one groove has a width of at least 0,1% of the total perimeter of the electric conductor.

53. A multi conductor system according to any of the preceding claims, wherein the distance between the first end and one of the first groove point and the second groove point is at least 1cm.

54. A multi conductor system according to any of the preceding claims, wherein the electric conductor comprises a center conductor part having a center perimeter partly defined by bottoms of a plurality of grooves, and wherein the plurality of grooves is forming the plurality of branches so that the width of at least part of the plurality of branches is larger at the outer perimeter surface than at the center perimeter.

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