slot 12 which is defined by a third area surrounded from the surface section in between the second local slot distance minimum 442 and a third local slot distance minimum 462 a line segment limited by 461 and 462 and a third projected slot lobe line segment determined by a line segment limited by 441 and 461 fig4 furthermore illustrates an exemplary embodiment of the invention with increasing maximum root and slot distances as can be seen in fig4 the maximum root distance of the first root lobe 41 which is determined by the length of the line segment limited by 411 and 412 is smaller than the maximum root distance of the second root lobe 43 which is determined by the length of the line segment limited by 431 and 432 which in turn is smaller than the maximum root distance of the third root lobe 45 which is determined by the length of the line segment limited by 451 and 452 analogously the maximum slot distance of the first slot lobe 42 which is determined by the length of the line segment limited by 423 and 424 is smaller than the maximum slot distance of the second slot lobe 44 which is determined by the length of the line segment limited by 443.