Stator for an electric machine comprising: - a stator core having a first and a second face opposite to one another (3, 4) and a circular array of stator slots extending between said faces (3, 4) and distributed around a stator axis (Z-Z); and - a bar winding comprising a plurality of basic conductors and a plurality of special conductors (12, 13, 14, 15, 16, 17) interconnected to one another for forming the bar winding; wherein each basic conductor comprises two basic conductor legs (11A, 11B) and a basic conductor connecting portion between said legs (11A, 11B), each basic conductor leg (11A, 11B) having an end portion connected to the basic conductor connecting portion and an opposite free end portion, wherein the basic conductors are inserted in the stator slots with the free end portions protruding from said second face, the free end portions defining a plurality of circular conductor layers (L1, L2, L3, L4) concentric to one another comprising a radially outer circular end layer and a radially inner circular end layer, wherein the special conductors (12, 13, 14, 15, 16, 17) comprise a jumper (12; 13) of a first type having a first and a second jumper arm (12A, 12B; 13A, 13B) respectively connected to two of said free end portions, and a jumper jointing portion (12C; 13C) between said jumper arms (12A, 12B; 13A, 13B), wherein the jumper jointing portion (12C; 13C) extends radially outer with respect to said radially outer end layer, or radially inner with respect to said radially inner end layer, for passing around at least one of the free end portions respectively of the radially outer end layer or of the radially inner end layer; said stator being characterised in that the jumper of said first type (12; 13) is arranged so that: - the two free end portions to which the first and the second jumper arms (12A, 12B; 13A, 13B) are connected respectively belong to two of said conductor layers (L1, L2, L3, L4) separate from one another; - at least one between the first and the second jumper arms (12A, 12B; 13A, 13B) extends in a respective passage defined in said conductor layers (L1, L2, L3, L4) for connecting to the respective free end portion; wherein said conductor layers (L1, L2, L3, L4) include a first set of free end portions circumferentially bent by a first pitch and a second set of free end portions circumferentially bent by a second pitch differing from the first pitch, and wherein at least one of said conductor layers (L1, L2, L3, L4) comprises a group of free end portions bent by said first pitch that are arranged consecutive and circumferentially adjacent to one another; the jumper of said first type (12; 13) turning around said group of free end portions, and said free end portions whereto the first and the second jumper arm (12A, 12B; 13A, 13B) are connected being bent by said second pitch. - a stator core having a first and a second face opposite to one another (3, 4) and a circular array of stator slots extending between said faces (3, 4) and distributed around a stator axis (Z-Z); and - a bar winding comprising a plurality of basic conductors and a plurality of special conductors (12, 13, 14, 15, 16, 17) interconnected to one another for forming the bar winding; - the two free end portions to which the first and the second jumper arms (12A, 12B; 13A, 13B) are connected respectively belong to two of said conductor layers (L1, L2, L3, L4) separate from one another; - at least one between the first and the second jumper arms (12A, 12B; 13A, 13B) extends in a respective passage defined in said conductor layers (L1, L2, L3, L4) for connecting to the respective free end portion;