A stator core that includes electrical insulation between a small conductor segment and large conductor segment which forms stator coils inserted into slots of the stator core of a driving motor for a automobile vehicle. The axial length of the curved head of the small conductor segment is shorter than that of the curved head of the large conductor segment. A distance between slanted portions of the curved heads is greater than the difference between an amount of contraction due to bending of the large segment and the small segment.