an embodiment of the present invention will now be described with reference to fig1 to 6 . fig1 schematically shows a wind turbine 71 . the wind turbine 71 comprises a tower 72 , a nacelle 73 and a hub 74 . the nacelle 73 is located on top of the tower 72 . the hub 74 comprises a number of wind turbine blades 75 . the hub 74 is mounted to the nacelle 73 . moreover , the hub 74 is pivot - mounted such that it is able to rotate about a rotation axis 79 . a generator 76 is located inside the nacelle 73 . the wind turbine 71 is a direct drive wind turbine . fig2 schematically shows a comparative illustration of multi - turn and single turn wave windings for one phase and four poles . the upper part of fig2 shows the distributed winding with slots per pole and phase equal to 1 for a 3 - phase machine , phases a , b and c . a , b and c correspond to go direction of the phases and a ′, b ′ and c ′ correspond to return direction , i . e . opposite direction , of the phases . in the middle part of fig2 two poles 4 representing the first phase are shown . each of the poles 4 comprises a number of conductor windings 5 with multiple - turns per pole 4 . the strokes 6 indicate the more than one series turns . the conductors 5 are connected in series . this is indicated by the dashed line 7 . due to the series turns each of the poles 4 or coils comprises a number of go paths 17 and a number of return paths 18 . the lower part of fig2 schematically shows the inventive single turn wave windings for one phase of an inventive generator . the pole set belonging to the first phase a comprises a number of poles 4 , from which four poles 4 a , 4 b , 4 c and 4 d are shown . generally , the poles 4 may comprise a lamination . each pole 4 comprises a right side 10 , a left side 11 , a front side 12 and a back side 13 . a conductor 8 is wave - like turned about the poles 4 . the conductor 8 comprises a first half turn 8 a , a second half turn 8 b , a third half turn 8 c and a fourth half turn 8 d . the first half turn 8 a represents a return path a ′, the second half turn 8 b represents a go path a , the third half turn 8 c represents a return path a ′ and the fourth half turn 8 d represents a go path a . the first half turn 8 a proceeds along the right side 10 of the first pole 4 a and proceeds further along the back side 13 of the first pole 4 a . then it proceeds further along the left side 11 of the first pole 4 a and at the same time along the right side 11 of the second pole 4 b . this means , that the conductor passes a slot between the first pole 4 a and the second pole 4 b . then the conductor 8 further proceeds along the front side 11 of the second pole 4 b , then along the left side 11 of the second pole 4 b and at the same time along the right side 10 of the third pole 4 c . the conductor 8 further proceeds along the back side 13 of the third pole 4 c and along the left side of the third pole 4 c and at the same time along the right side 10 of the fourth pole 4 d . in this wave - like configuration the first half a turn 8 a is associated to the first pole 4 a , the second half a turn 8 b is associated to the second pole 4 b , the third half a turn 8 c is associated to the third pole 4 c and the fourth half a turn 8 d is associated to the fourth pole 4 d . fig3 schematically shows part of the single turn wave windings of the lower part of fig2 in a perspective view . the poles 4 are separated from each other by slots 19 . a number of conductors 8 are connected in parallel and are turned about the poles in such a way that only half a single turn of each conductor is associated to each pole , as shown in the lower part in fig2 and in fig3 . the optimal number of parallel conductors to give a low value of proximity and skin effect loss can be chosen analytically or experimentally or by simulation . an example is shown in fig4 . fig4 schematically shows the ac loss factor for single turn windings versus the number of parallel conductors which are always assumed to be fully transposed . the x - axis represents the number n of parallel and fully transposed conductors . the y - axis represents the ac loss factor l for a single turn winding in arbitrary units . the ac loss factor is caused by proximity and skin effect losses . the obtained curved 14 in fig4 shows a maximum ac loss factor for about two parallel conductors . with a further increasing number of parallel conductors the ac loss factor decreases nearly exponentially . for eight and more parallel conductors the ac loss factor l decreases only minimally . the curve 14 shows for ten and more parallel conductors a nearly straight line which is nearly parallel to the x - axis . this means , that the optimal number of parallel conductors to give a low value of proximity and skin effect loss is ten and more . fig5 schematically shows an arrangement of fully transposed 5 parallel conductors belonging to one phase . in the shown arrangement the first pole 21 is followed by a second pole 22 , followed by a third pole 23 , followed by a fourth pole 24 , which is followed by a fifth pole 25 and so forth . each of the poles 21 , 22 , 23 , 24 and 25 comprises an upper side 15 and a bottom side 16 . the different conductors are designated by numbers 1 to 5 . each pole 21 , 22 , 23 , 24 and 25 comprises five positions , a first position 31 , a second position 32 , a third position 33 , a fourth position 34 and a fifth position 35 , which follow each other from the upper side 15 to the bottom side 16 . in the first pole 21 the first conductor 1 is located at the first position 31 , the second conductor 2 is located at the second position 32 , the third conductor 3 is located at the third position 33 , the fourth conductor 4 is located at the forth position 34 and the fifth conductor 5 is located at the fifth position 35 . in the second pole 22 the next half a turn of the first conductor 1 changes to the second position 32 , the next half a turn of the second conductor 2 changes to the third position , the next half a turn of the third conductor 3 changes to the fourth position 34 and the next half a turn of the fourth conductor 4 changes to the fifth position 35 . the next half a turn of the fifth conductor 5 changes from the fifth position 35 in the first pole 21 to the first position 31 in the second pole 22 . this pattern is continued for the next poles as shown in fig5 . by arranging the conductors as shown in fig5 the 5 parallel conductors are completely transposed . in the present embodiment the generator comprises three phases , which means that it comprises three pole sets . each pole set comprises ten poles . the pattern which is shown in fig5 is cyclically repeated for the other 5 poles which are not shown in fig5 . generally , the generator comprises a rotor 26 , a stator 27 and an airgap 28 between the rotor 26 and the stator 27 . the stator 27 comprises the poles shown in fig5 . alternatively , the rotor 26 may comprise the poles shown in fig5 . fig6 schematically shows as an example the insulation between the parallel conductors 55 of a pole 53 . the conductors are numbered from 1 to 5 . they are connected in parallel , as previously described . because of the connection in parallel and the parallel assembly none or only very thin conductor insulation 55 is necessary between the different conductors . generally , the generator 76 can comprise an inner stator , which means that the stator is located radially inside of the rotor of the generator related to the rotation axis 79 of the rotor . alternatively , the generator can comprise an outer stator , which means that the stator is located radially outside of the rotor of the generator related to the rotation axis 79 of the rotor . in both cases the rotor and / or the stator can comprise the described single turn wave winding . based on the described transposed single turn wave winding configuration , it is theoretically clear that the parallel conductors in the slot may need no insulation or only some varnish as there is none or very small voltage difference between these parallel conductors . furthermore , using the described single turn wave - like winding the manufacturing of the coils and the winding process becomes significantly easier and less costly than for conventional multi - turn windings .