Patent Publication Number: US-2021194283-A1

Title: Device for a wireless power transfer system

Description:
RELATED APPLICATION DATA 
     This application is a continuation of International Patent Application No. PCT/CN2019/103603, filed Aug. 30, 2019, which claims the benefit of European Patent Application No. 18194133.7, filed Sep. 12, 2018, the disclosures of which are incorporated herein by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The invention relates to a device for a wireless power transfer system, a transmitter and a wireless power transfer system comprising such a device for charging a vehicle. 
     BACKGROUND 
     Electric vehicles and plug in hybrid vehicles can be charged wirelessly through induction coils. Usually a first coil of a transmitter is arranged on the floor or the ground under the vehicle and a second coil of a receiver is arranged at the underside of the vehicle. There is a lot of different coil topologies that can be used for transferring power. In addition to transfer power efficiently, often small sized coils and coils enabling a large positioning tolerance between the transmitter coil and the receiver coil are preferred. This in turn makes the manufacturing and assembling of the coil into a casing relatively complicated. There are various coil topologies used at charging stations for vehicles. This means that the winding pattern of a receiver coil of a vehicle will not always match the winding pattern of a transmitter coil of a charging station. Further, vehicles have various ground clearances and distances between the receiver and the ground. Thus, in some cases it can be difficult to achieve efficient charging due to mismatch of topologies between the transmitter and the receiver. 
     SUMMARY 
     An objective of the invention is to provide a device for a wireless power transfer system, which device can be used for improving wireless charging of vehicles. 
     The objective is achieved by a device for a wireless power transfer system, wherein the device comprises a housing and a conductor wire forming a coil arranged in the housing, the coil has a first topology, and wherein the conductor wire is rearrangeable such that the coil is given a second topology instead of the first topology, and the first topology and the second topology are different from each other. 
     The invention is based on the insight that by such a device, the coil topology of a transmitter can be selected to match the coil topology of a receiver enabling efficient charging of a vehicle for various coil topologies of the receiver of the vehicle. By a first topology and a second topology different from each other is meant that the winding patterns of the coil and/or the levels (positions in a vertical direction) of the coil are different for the first topology and the second topology. Of course, the device can have two or more selectable coil topologies which are different from each other. 
     According to one embodiment of the device, the first topology has a plurality of coil windings arranged in a first pattern and the second topology has the plurality of coil windings arranged in a second pattern different from the first pattern. Hereby, the topology of a transmitter coil for charging vehicles can be changed from a first topology having a first standard pattern, to a second topology having a second standard pattern. Thus, the coil topology of the transmitter can be selected to match the coil topology of a receiver of the vehicle for efficient charging. 
     According to a further embodiment, the first topology has a plurality of coil windings arranged at a first level and the second topology has the plurality of coil windings arranged at a second level different from the first level. Hereby, the level of the transmitter coil can be selected for matching the dimensions and ground clearance of a vehicle to be charged. Thus, the distance between a transmitter coil and a receiver coil can be selected for efficient charging. 
     According to a further embodiment, the device comprises an actuator for moving the conductor wire from the first topology to the second topology, and from the second topology to the first topology. The actuator can be controlled by a control unit. By means of the actuator, the conductor wire can be moved in a rational way for providing various topologies. 
     For example, the actuator can comprise a motor, a spool driven by the motor and a non-conductive thread wound on the spool and mechanically connected to the conductor wire, and preferably the thread on the spool has a first end mechanically connected to a first end of the conductor wire and a second end mechanically connected to a second end of the conductor wire, wherein the first end of the thread is arranged to be wound up on the spool and the second end of the thread is arranged to be unwound from the spool, when the conductor wire is moved from the first topology to the second topology, and the first end of the thread is arranged to be unwound from the spool and the second end of the thread is arranged to be wound up on the spool, when the conductor wire is moved from the second topology to the first topology. 
     The actuator is preferably arranged for moving the conductor wire in the longitudinal direction of the conductor wire. Hereby, the conductor wire can be smoothly moved step by step along a predetermined path. The actuator is preferably arranged for pulling the conductor wire from the first topology to the second topology, and from the second topology to the first topology. Hereby, a conductor wire having a relatively high flexibility can be moved through a pipe or similar with low or no risk of getting stuck at bends of the pipe. 
     According to a further embodiment, the device comprises a first pipe portion for receiving and accommodating the conductor wire inside the first pipe portion, wherein the first pipe portion has a longitudinal extension forming a pattern that gives the conductor wire the first topology when being arranged inside the first pipe portion and/or the device comprises a second pipe portion for receiving and accommodating the conductor wire inside the second pipe portion, wherein the second pipe portion has a longitudinal extension forming a pattern that gives the conductor wire the second topology when being arranged inside the second pipe portion. Hereby, predetermined topologies can be achieved in a non-complicated way. 
     The actuator is preferably arranged for moving the conductor wire from the first pipe portion to the second pipe portion, and from the second pipe portion to the first pipe portion. For facilitating movement of the conductor wire, the device can have a lubricant arranged inside the pipe portion for reducing the friction between the conductor wire and the pipe portion and/or the device can have rolls arranged at the inside of the pipe portion for reducing the friction between the conductor wire and the pipe portion. 
     According to a further embodiment, the device has a first electric contact and a second electric contact, wherein a first end of the conductor wire is electrically connected to the first electric contact and a second end of the conductor wire is electrically connected to the second electric contact, when the coil has the first topology, and wherein the first end of the conductor wire is electrically connected to the second electric contact and the second end of the conductor wire is electrically connected to the first electric contact, when the coil has the second topology. Hereby, the number of requisite connectors and the amount of wire extending between the coil and a power supply equipment can be reduced, since only two electric contacts are required for two different topologies of the coil. 
     According to a further embodiment, the second electric contact has an opening through which the conductor wire extends, wherein the conductor wire is moveable relative to the second electric contact in two opposite direction. Hereby, it can be ensured that the current conductor wire end is positioned at the second electric contact for connection thereto after the conductor wire has been moved from the first coil topology to the second coil topology, or vice versa. 
     According to a further embodiment, at least one of the first topology and the second topology is arranged for wireless power transfer for charging a further apparatus or being charged by a further apparatus, and preferably both the first topology and the second topology are arranged for wireless power transfer for charging the further apparatus. The first topology can be a double-D (DD) coil topology and the second topology can be a circular square (CS) coil topology, or the first topology can be a circular square coil topology and the second topology can be a double-D coil topology. 
     Another aspect of the invention relates to a transmitter, and a further aspect of the invention relates to a wireless power transfer system for charging a vehicle. The advantages of the transmitter and the system are substantially the same as described for the device hereinabove. 
     Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples. 
       In the drawings: 
         FIG. 1  is a schematic view showing a charging station and a vehicle, 
         FIG. 2A  is a perspective view of a device for a wireless power transfer system, 
         FIGS. 2B and 2C  are enlarged views of a part of the device in  FIG. 2A , 
         FIG. 3  is an exploded view of the device in  FIG. 2A , 
         FIG. 4  is a top view of the device in  FIG. 2A , 
         FIG. 5  is a bottom view of the device in  FIG. 2A , 
         FIG. 6  is a perspective view of the device in  FIG. 2A  shown with the bottom side up, and 
         FIG. 7  is a cross-section view taken along the line VII-VII in  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1  a vehicle  1  is positioned at a charging station  2  where a wireless power transfer system  3  is used. The wireless power transfer system  3  includes a transmitter  4  for transferring power to a receiver  6  arranged in the vehicle  1 . Such a transmitter can be arranged on or in the floor  5  or the ground. The receiver  6  is preferably arranged on the underside of the vehicle  1 . The transmitter  4  has a primary coil for generating an electromagnetic field and the receiver  6  has a secondary coil for interacting with the generated electromagnetic field for achieving power transfer from the primary coil to the secondary coil by electromagnetic induction. An electric power input  7  to the transmitter  4  can be wirelessly transferred from the transmitter  4  to the receiver  6  to achieve an electric power output  8  from the receiver  6 . The wireless transfer of energy is schematically illustrated with arrows  11 . 
     In the illustrated example, the transmitter  4  is powered by a power source  9  electrically connected to the transmitter  4 . The power source and the power outlet thereof can be arranged at any suitable position, for example the power source can be arranged on a wall. The receiver  6  can be connected to any arrangement for storing and/or consumption of the energy transferred. In the illustrated example, the receiver  6  is electrically connected to a battery  10  arranged on the vehicle  1  for charging the battery  10 . 
     Before charging of the vehicle  1  is started, the vehicle is positioned for arranging the transmitter  4  and the receiver  6  relative to each other such that energy can be transferred from the transmitter  4  to the receiver  6 . For optimizing the charging, the transmitter  4  and the receiver  6  are suitably arranged at a distance from each other in a vertical direction, which distance should be within a predetermined distance interval. Further, the transmitter  4  and the receiver  6  should suitably be aligned relative each other such that the transmitter and the receiver overlap each other within predetermined limits when looked at in the vertical direction. 
     The device according to the invention can be applied for providing a transmitter and/or a receiver of a wireless power transfer system. For example, such a wireless power transfer system device according to the invention can be used as a component of a transmitter to be arranged at a charging station as illustrated in  FIG. 1 . It should be stressed that when the device is used for a transmitter (or receiver), the complete transmitter (or receiver) may include other components as well, such as electric circuits and electric components. Further, the invention is not in any way limited to the car application. The device can be used in any vehicle or machine application, such as for charging for example cars, busses, trucks, industrial trucks and automated guided vehicles, construction equipment and work machines, and trains. 
       FIG. 2A  shows a device  20  for a wireless power transfer system. The device comprises a housing  21  and a conductor wire  22  forming a coil  23  arranged in the housing  21 .  FIG. 2A  is a partly cut perspective view where a part of the device has been removed for illustrating the coil  22 . See also enlarged part in  FIG. 2B . Further, the housing  21  is also depicted as transparent to show the components arranged inside the housing  21 . 
     As illustrated in  FIGS. 2A and 2B , the device  20  can comprise a first pipe portion  24  for receiving and accommodating the conductor wire  22  inside the first pipe portion  24 . For illustration purposes only, the first pipe portion  24  is white. The coil  23  comprises a plurality of coil windings formed by the conductor wire  22 . The coil  23  has a first topology  25   a . This first topology  25   a  corresponds to the topology  25   b  of the first pipe portion  24 . The first pipe portion  24  has a longitudinal extension forming a pattern that gives the conductor wire  22  the first topology  25   a  when being arranged inside the first pipe portion  24 . Thus, the first pipe portion  24  forms a pattern corresponding to the winding pattern of the coil  23 . The first pipe portion  24  can have a pattern corresponding to a topology of a coil used for charging vehicles, such as a DD coil topology. 
     Further, the device  20  can comprise a second pipe portion  26  for receiving and accommodating the conductor wire  22  inside the second pipe portion  26 . In the enlarged part in  FIG. 2C , the conductor wire  22  is shown when arranged in the second pipe portion  26  instead of the first pipe portion. For illustration purposes only, the second pipe portion  26  is grey. 
     The conductor wire  22  is rearrangeable such that the coil  23  is given a second topology  27   a  instead of the first topology. The first topology  25   a  and the second topology  27   a  are different from each other. By rearrangeable is meant that the conductor wire  22  is moveable from a first position to a second position in a predetermined way for changing the coil topology. In other words; the device has at least two selectable coil topologies which can be achieved by one and the same conductor wire. 
     The second topology  27   a  corresponds to the topology  27   b  of the second pipe portion  26 . The second pipe portion  26  has a longitudinal extension forming a pattern that gives the conductor wire  22  the second topology  27   a  when being arranged inside the second pipe portion  26 . Thus, the second pipe portion  26  forms a pattern corresponding to the winding pattern of the coil  23 . The second pipe portion  26  can have a pattern corresponding to a topology of a coil used for charging vehicles, such as a CS coil topology. 
     Although the first pipe portion and the second pipe portion illustrated herein, each forms a continuous pipe portion with a length corresponding to the conductor wire length, such a pipe portion could comprise two or more separate parts forming an intermittent pipe portion providing the desired pattern. For example, for moving the conductor wire and achieve a pipe portion pattern giving the desired topology, pipe portion parts arranged at the bends may be sufficient. 
     Accordingly, the first topology can have a plurality of coil windings arranged in a first pattern and the second topology can have the plurality of coil windings arranged in a second pattern different from the first pattern. Thus, the coil topology can be changed by changing the configuration of the winding pattern of the coil  23 . The first topology can have a double-D (DD) winding pattern configuration, also called double-D (DD) coil topology, and the second topology can have a circular square (CS) winding pattern configuration, also called circular square (CS) coil topology. Such coil topologies are suitably used in transmitters and receivers for charging vehicles. 
     By providing various winding patterns, a winding pattern configuration matching the winding pattern configuration of a corresponding coil of a further apparatus can be selected. For example, the winding pattern of a transmitter coil used for charging a vehicle can be selected to match a winding pattern of a receiver coil of the vehicle for achieving efficient charging. 
     The first topology can also have a plurality of coil windings arranged at a first level and the second topology can have the plurality of coil windings arranged at a second level different from the first level. Thus, the coil topology can be changed by changing the winding pattern level. This means that there is a distance between the coil position in the first level and the coil position in the second level in a direction that is perpendicular to a main extension plane of the coil  23 . A Cartesian coordinate system is indicated in  FIG. 2A , where the main extension plane of the coil  23  is parallel with the XY-plane and thus the first level and the second level correspond to different positions along the Z-axis. In other words; the distance between the first level and a reference point, in a direction perpendicular to the main extension plane of the coil  23 , is different from the distance between the second level and the reference point. Such a reference point can be a fixed point or surface of the device, such as a point or surface of the housing  21  for instance. 
     By providing various levels for the coil, the position of the coil relative to a corresponding coil of a further apparatus can be varied. For example, the position relative to the floor/ground of a charging station for a transmitter coil used for charging a vehicle, can be varied and adapted to the position of a receiver coil of the vehicle for achieving efficient charging. In such a case, with reference to  FIG. 2A , the device is arranged such that the Z-axis is parallel with a vertical direction and the coil is rearrangeable such that various levels can be selected. 
     The first topology or the second topology can be selected automatically based on the topology type of a receiver coil, which can be sensed, or the first topology or the second topology can be selected by an operator by pushing a button. 
     Other topologies than DD coil topology and CS coil topology are of course possible, and the conductor wire  22  could be rearrangeable to achieve more than two different topologies. In fact, the conductor wire could be arranged to be rearrangeable such that two or more different winding patterns and/or two or more different levels of the conductor wire can be selected. 
     Although in the example embodiment illustrated in  FIG. 2A , the first pipe portion  24  is arranged in a pattern giving the conductor wire a DD coil topology ( 25   a ) and the second pipe portion  26  is arranged in a pattern giving the conductor wire a CS coil topology ( 27   a ), pipe portions having other patterns for achieving other coil topologies could also be used. 
     For facilitating movement of the conductor wire between different topologies, lubricant can be arranged inside the pipe portion for reducing the friction between the conductor wire and the pipe portion. Further, one or more rolls can be arranged inside the pipe portion, preferably at bends of the pipe portion for reducing the friction between the conductor wire and the pipe portion. 
       FIG. 3  shows an example embodiment of the device  20  in an exploded view. The housing  21  comprises a top cover  30  and a bottom cover  31  shown separated from each other. The top cover  30  and the bottom cover  31  are mechanically connectable to each other for forming the housing  21 . The components to be arranged inside the housing  21  are illustrated between the top cover  30  and the bottom cover  31 . The first pipe portion  24  and the second pipe portion  26  arranged for providing the first topology and the second topology, respectively, are arranged on top of each other. The first pipe portion  24  and the second pipe portion  26  are preferably made by a non-conductive material, such as plastic or similar. 
     The conductor wire  22  forming the coil  23  is not shown in  FIG. 3  but should be arranged inside the first pipe portion  24  or the second pipe portion  26  as previously described. Although other types of conductor wire could be used, the conductor wire is preferably a sum of many small strands of individually insulated copper wires, a so called Litz wire for instance. 
     Further, a ferrite plate  32  is arranged below the first pipe portion  24  and the second pipe portion  26 . The number of ferrite plates can be varied, and such a ferrite plate may in turn be divided into a plurality of sub ferrite plates and/or be designed in different shapes. The function and design of such a ferrite plate is well known by the person skilled in the art and will not be further described herein. 
     Between the bottom cover  31  and the ferrite plate  32  a back plate  33  is arranged. The back plate  33  is an insulation plate made by aluminium for instance. 
     In addition, the device  20  suitably comprises an actuator  34  for moving the conductor wire  22  from the first topology to the second topology, and from the second topology to the first topology. The actuator  34  is arranged for moving the conductor wire  22  in the longitudinal direction of the conductor wire  22 . This means that the conductor wire  22  arranged inside the pipe portion can be pushed or preferably pulled through the pipe portion while following the pipe portion configuration. Finally, the device  20  comprises electric contacts  35 ,  36  for connection of an input power cable and an output cable for connecting an external power source to the conductor wire  22 . The actuator can comprise a motor  37 , a spool  38  driven by the motor  37  and a non-conductive thread  39  wound on the spool  38  and mechanically connected to the conductor wire  22 . The non-conductive thread is also shown in  FIGS. 2B and 2C . The actuator  34  will be further described hereinafter with reference to  FIG. 5 . 
       FIG. 4  shows a top view of the device  20  where the top cover has been removed. The first pipe portion  24  is arranged in a pattern giving the conductor wire a DD coil topology and the second pipe portion  26  is arranged in a pattern giving the conductor wire a CS coil topology. In a central part  40  of the housing  21 , the first pipe portion  24  is arranged above the second pipe portion  26 , and in outer parts  41  of the housing  21  the first pipe portion  24  and the second pipe portion  26  are arranged substantially in the same plane with alternating windings of the first pipe portion  24  and windings of the second pipe portion  26  in the plane. 
     A first end  42  of the first pipe portion  24  and a first end  43  of the second pipe portion  26  are mechanically connected to each other for forming a continuous pipe portion. A second end  44  of the first pipe portion  24  and a second end  45  of the second pipe portion  26  extend through the ferrite plate  32  and the back plate  33  to a first connection unit arranged between the back plate  33  and the bottom cover  31 . 
       FIG. 5  shows a bottom view of the device  20  where the bottom cover has been removed. The second end  44  of the first pipe portion  24  extends from a through hole  51  of the back plate  33  to the first connection unit  50 . The second end  45  of the second pipe portion  26  extends from a through hole  52  of the back plate  33  to the first connection unit  50 . The first connection unit  50  provides a first electric contact  35  to which a first end of the conductor wire  22  or a second end of the conductor wire  22  can be connected. The first end of the conductor wire  22  is connected to the first electric contact  35  when the conductor wire  22  is arranged in the first pipe portion  24 , whereas the second end of the conductor wire  22  is connected to the first electric contact  35  when the conductor wire  22  is arranged in the second pipe portion  26 . The first electric contact  35  is in turn connected to a power source by the input power cable  53 . 
     The device  20  also comprises a second connection unit  54  providing a second electric contact  36  to which the first end of the conductor wire  22  or the second end of the conductor wire  22  can be connected. The second connection unit  54  can be arranged at the connection point  70  between the first pipe portion  24  and the second pipe portion  26  for contacting the conductor wire  22  by the second electric contact  36 . See  FIG. 4 . The second connection unit  54  can extend from the pipe portion, for example close to the connection point  70  of the first pipe portion  24  and the second pipe portion  26 , and through the ferrite plate  32  and the back plate  33  to a position between the back plate  33  and the bottom cover  31  of the housing  21 . Here, the second electric contact  36  can be connected to the output cable  55  in a similar way as the first electric contact  35  is connected to the input power cable  53 . See  FIGS. 3 and 4  showing the second electric contact  36  at the connection point  70 . 
     The second end of the conductor wire  22  is connected to the second electric contact  36  when the conductor wire  22  is arranged in the first pipe portion  24 , whereas the first end of the conductor wire  22  is connected to the second electric contact  36  when the conductor wire  22  is arranged in the second pipe portion  26 . 
       FIG. 7  is a cross-section view taken along the line VII-VII in  FIG. 4 . The second electric contact  36  can have an opening  80  through which the conductor wire  22  extends which opening  80  enables the conductor wire  22  to be moved relative to the second electric contact  36  in two opposite directions  81 ,  82 . Thus, when the conductor wire  22  is moved from the first topology to the second topology, the conductor wire  22  moves through the opening  80  of the second electric contact  36  from a position where the second end  63  of the conductor wire  22  is connected to the second electric contact  36  to a position where the first end  61  (not shown in  FIG. 7 ) of the conductor wire  22  is connected to the second electric contact  36 , and vice versa. The conductor wire  22  can have means  83  at the first end  61  and the second end  63  for preventing the conductor wire  22  from being moved further in the same direction when the first end or second end has reached the second electric contact  36 . For example, such a means  83  can be a portion  84  arranged on the conductor wire  22  which portion  84  has a larger size than the opening  80  preventing the portion  84  from passing through the opening  80 . 
     Thus, preferably, the first end of the conductor wire  22  is electrically connected to the first electric contact  35  and the second end of the conductor wire  22  is electrically connected to the second electric contact  36 , when the coil  23  has the first topology, and the first end of the conductor wire  22  is electrically connected to the second electric contact  36  and the second end of the conductor wire  22  is electrically connected to the first electric contact  35 , when the coil  23  has the second topology. Preferably, the portions  84  arranged at the ends of the conductor wire are used for contacting the second electric contact  36  and the first electric contact  35 , respectively. 
       FIGS. 5 and 6  show an example of the actuator  34  which is arranged between the back plate  33  and the bottom cover  31  of the housing  21 .  FIG. 6  is a perspective view of the device  20  shown with the bottom side up. Thus, the device  20  illustrated in  FIGS. 5 and 6  is turned upside down relative to the device illustrated in  FIGS. 2 and 4 . The bottom cover  31  of the housing  21  is partly cut in  FIG. 6  and removed in  FIG. 5  for illustrating the actuator  34 . 
     The actuator  34  comprises the motor  37 , see also  FIG. 3 , the spool  38  driven by the motor  37  and the non-conductive thread  39  wound on the spool  38 . The motor  37  can be arranged in the back plate  33  and attached with any suitable means known by the skilled in the art. The thread  39  and the conductor wire  22  are mechanically connected to each other. The motor  37  can be an electric stepping motor driving the spool  38 . The motor  37  can be controlled by a control unit. As previously described, the conductor wire  22  is arranged inside the pipe portion and the actuator  34  is arranged for moving the conductor wire  22  from the first pipe portion  24  to the second pipe portion  26 , and vice versa. The actuator  34  is arranged for pulling the conductor wire  22  in the longitudinal direction of the conductor wire  22  by driving the spool  38 . When the spool  38  is rotated, the thread  39  will wound up on the spool  38  and pull the conductor wire  22 . This means that the conductor wire  22  can be pulled through the pipe portion step by step while following the pipe portion configuration. 
     In the example embodiment illustrated in  FIGS. 5 and 6 , the thread  39  on the spool  38  has a first end  60  mechanically connected to a first end  61  of the conductor wire  22  and a second end  62  mechanically connected to a second end of the conductor wire  22 . The second end of the conductor wire is not shown here since the first topology is illustrated where the second end of the conductor wire is connected to the second electric contact of the second connection unit. 
     The first end  60  of the thread  39  can suitably be moved through a first opening  64  of the first connection unit  50 , and the second end  62  of the tread  39  can suitably be moved through a second opening  65  of the first connection unit  50 . The first end  60  of the thread is arranged to be wound up on the spool  38  and the second end  62  of the thread is arranged to be unwound from the spool  38 , when the conductor wire  22  is moved from the second topology to the first topology. Further, the first end  60  of the thread is arranged to be unwound from the spool  38  and the second end  62  of the thread is arranged to be wound up on the spool  38 , when the conductor wire  22  is moved from the first topology to the second topology. 
     As further illustrated in  FIGS. 5 and 6 , the first pipe portion  24  and the second pipe portion  26  each has a part  66 ,  67  extending in the space between the back plate  33  and the bottom cover  31 . The back plate  33  constitutes a shield and the conductor wire  22  arranged in these parts  66 ,  67  of the first and second pipe portions is shielded by the back plate  33 . Thus, the length of the conductor wire  22  shielded by the shield  33  is variable by movement or rearrangement of the conductor wire  22 . These shielded conductor wire parts will not contribute to the magnetic field used for charging. 
     This can be utilized for allowing different effective conductor wire lengths for different topologies for one and the same conductor wire length. In the example embodiment illustrated, the first topology (DD coil topology) requires a somewhat longer conductor wire length than the second topology (CS coil topology). In other words; a part of the conductor wire  22  may constitute an excess of conductor wire for one of the first coil topology and the second coil topology due to different conductor wire lengths required for the first topology and the second topology. This conductor wire part can be shielded by the shield. The excess of conductor wire  22  when the shorter CS coil topology is used can be arranged in the part  67  of the second pipe portion  26  that is shielded. For this reason, in the illustrated example embodiment in  FIGS. 5 and 6 , the part  67  of the second pipe portion  26  arranged on the shielded side of the back plate  33  is longer than the part  66  of the first pipe portion  24  arranged on the shielded side of the back plate  33 . 
     In addition to move the conductor wire  22  from one topology to another topology, the actuator  34  could be used for fine-tuning the position of the conductor wire for optimizing the power transfer. Such adjustment of the conductor wire can comprise adjustment of the position of the conductor wire and/or the effective length (non-shielded length) of the conductor wire  22 . 
     It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.