Rotary electric machine with improved slot insulation

1) An electric machine (1) comprising:

• a shaft (2), which is mounted so as to rotate around a central rotation axis (3);
• a rotor (4) with permanent magnets (23), which is fitted to the shaft (2) so as to rotate together with the shaft (2);
• a stator (5) with a tubular, cylindrical shape, which is arranged around the rotor (4) so as to enclose, on the inside, the rotor (4) and has a magnetic core (6), which consists of a series of laminations made of a ferromagnetic material and is longitudinally crossed by a plurality of stator slots (7);
• and
• a stator winding (8) comprising a plurality of copper rigid bars (9), which are inserted in corresponding stator slots (7) and are covered, on the outside, with an insulating coating (14);
• wherein each stator slot (7) is completely free from an insulating element interposed between the ferromagnetic material making up the laminations of the magnetic core (6) and the corresponding bars (9), so that an outer surface (18) of the corresponding bars (9) is in direct contact with an inner surface (19) of the stator slot (7) made of the ferromagnetic material of the stator slot (7);
• wherein the insulating coating (14) which covers on the outside each bar (9) has an inner layer (20) that is in direct contact with the copper and an outer layer (21) that is arranged above the inner layer (20) and is in direct contact with the ferromagnetic material making up the laminations of the magnetic core (6);
• and
• wherein the inner layer (20) consists of a first material and the outer layer (21) consists of a second material that differs from the first material, it is mechanically stronger than the first material and is electrically less insulating than the first material.