Stator for electric motor

1. A stator for an electric motor, the stator comprising:

a stator core defining a rotor receiving hole, the stator core including a plurality of slots and a plurality of teeth that are provided around the rotor receiving hole; and

a stator coil wound around the stator core via the plurality of slots,

wherein the stator coil comprises a plurality of hairpins inserted into the plurality of slots and connected in series with one another, the plurality of hairpins including (i) high voltage distribution hairpins having a high voltage distribution ratio based on receiving power and (ii) low voltage distribution hairpins having a low voltage distribution ratio based on receiving power,

wherein adjacent ones of the plurality of hairpins are spaced apart from each other by a partial discharge suppression distance that is configured to suppress partial discharge between the adjacent ones of the hairpins, and

wherein the partial discharge suppression distance between adjacent high voltage distribution hairpins among the plurality of hairpins is greater than the partial discharge suppression distance between adjacent low voltage distribution hairpins among the plurality of hairpins.

2. The stator of claim 1 , wherein the plurality of hairpins include a plurality of outermost hairpins that are disposed at radially outermost portions of the plurality of slots, at least some of the outermost hairpins being configured to be connected to a power source,

wherein outermost hairpins are separated from an adjacent conductor by a first partial discharge suppression distance, and hairpins disposed at a radially inner side of the outermost hairpins are separated from an adjacent conductor by a second partial discharge suppression distance, and

wherein the first partial discharge suppression distance is greater than the second partial discharge suppression distance.

3. The stator of claim 2 , wherein the first partial discharge suppression distance is 1.2 mm or greater.

4. The stator of claim 2 , wherein the second partial discharge suppression distance is 0.2 mm or greater.

5. The stator of claim 2 , wherein each of the outermost hairpins comprises:

a first insertion part and a second insertion part disposed at an outermost layer of the plurality of slots;

a first crown part having one end connected to the first insertion part; and

a second crown part having one end connected to the first crown part and the other end connected to the second insertion part,

wherein the first crown part of one of the outermost hairpins and the second crown part of an adjacent one of the outermost hairpins are spaced apart from each other by the first partial discharge suppression distance.

6. The stator of claim 5 , wherein the first crown part of each of the outermost hairpins is spaced apart outwardly from the first insertion part along a radial direction of the stator core.

7. The stator of claim 6 , wherein each of the outermost hairpins comprises a first radially-bent part that is curved outwardly from the first insertion part in the radial direction of the stator core and connected to the first crown part.

8. The stator of claim 7 , wherein the second crown part of each the outermost hairpins is spaced apart inwardly from the first crown part along the radial direction of the stator core.

9. The stator of claim 8 , wherein the second crown part of each of the outermost hairpins is disposed at an outer position relative to the second insertion part along the radial direction of the stator core.

10. The stator of claim 9 , wherein the outermost hairpin comprises a second radially-bent part that is curved outwardly from the second insertion part in the radial direction of the stator core and connected to the second crown part.

11. The stator of claim 10 , wherein the first radially-bent part and the second radially-bent part each have a minimum radius of curvature that is 2.0 mm or greater.

12. The stator of claim 10 , wherein the first crown part is disposed to form a first minimum interior angle with respect to a first extension line and the second crown part is disposed to form a second minimum interior angle with respect to a second extension line,

wherein the first extension line and the second extension line are parallel to the first insertion part and the second insertion part, respectively, and

wherein the minimum interior angle is 110 degrees or greater.

13. The stator of claim 10 , wherein the first radially-bent part protrudes from the first insertion part by a first protrusion length and the second radially-bent part protrudes from the second insertion part by a second protrusion length along the radial direction of the stator, and

wherein the first protrusion length is equal to or greater than a value obtained by adding the first partial discharge suppression distance to the second protrusion length.

14. The stator of claim 5 , wherein the stator coil comprises a plurality of phase coils configured to be connected to corresponding phases of the power source, respectively,

wherein the plurality of phase coils comprises a U-phase coil, a V-phase coil, and a W-phase coil that are spaced apart from one another by an 8-slot pitch along a circumferential direction of the stator core,

wherein each of the plurality of phase coils includes a plurality of phase-parallel coils connected in parallel to one another, and

wherein each of the plurality of phase-parallel coils is provided with first to fourth phase-parallel coils spaced apart from one another by a one-slot pitch along the circumferential direction of the stator core.

15. The stator of claim 14 , wherein the stator coil comprises:

a first outermost hairpin having the first insertion part and the second insertion part spaced apart from each other by a 13-slot pitch along the circumferential direction of the stator core, and

a second outermost hairpin having the first insertion part and the second insertion part spaced apart from each other by a 9-slot pitch along the circumferential direction of the stator core.

16. The stator of claim 15 , wherein the U-phase coil comprises a phase-parallel coil of the U-phase coil and the V-phase coil comprises a phase-parallel coil of the V-phase coil,

wherein the second crown part of the first outermost hairpin of the phase-parallel coil of the U-phase coil and the first crown part of the first outermost hairpin of the phase-parallel coil of the V-phase coil are spaced apart by the first partial discharge suppression distance.

17. The stator of claim 15 , wherein the V-phase coil comprises a phase-parallel coil of the V-phase coil and the W-phase coil comprises a phase-parallel coil of the W-phase coil,

wherein the second crown part of the first outermost hairpin of the phase-parallel coil of the V-phase coil and the first crown part of the first outermost hairpin of the phase-parallel coil of the W-phase coil are spaced apart by the first partial discharge suppression distance.

18. The stator of claim 15 , wherein the W-phase coil comprises a phase-parallel coil of the W-phase coil and the U-phase coil comprises a phase-parallel coil of the U-phase coil,

wherein the second crown part of the first outermost hairpin of the phase-parallel coil of the W-phase coil and the first crown part of the first outermost hairpin of the phase-parallel coil of the U-phase coil are spaced apart by the first partial discharge suppression distance.

19. The stator of claim 15 , wherein the plurality of hairpins further comprises:

a plurality of innermost hairpins disposed at an innermost side in the plurality of slots, and

a plurality of middle hairpins disposed between the plurality of innermost hairpins and the plurality of outermost hairpins in the plurality of slots,

wherein an innermost hairpin has the first insertion part and the second insertion part spaced apart from each other by a 12-slot pitch along the circumferential direction of the stator core, and

wherein a middle hairpin has the first insertion part and the second insertion part spaced apart from each other by a 12-slot pitch along the circumferential direction of the stator core.

20. The stator of claim 19 , wherein the innermost hairpin comprises:

a first insertion part and a second insertion part disposed at an innermost layer of the plurality of slots,

a first crown part having one end connected to the first insertion part, and

a second crown part having one end connected to the second insertion part,

wherein the second crown part is disposed at an inner side of the first crown part along a radial direction of the stator core.

21. The stator of claim 20 , wherein the second crown part of the innermost hairpin is disposed at an inner side of the second insertion part along the radial direction of the stator core.

22. The stator of claim 21 , wherein the innermost hairpin comprises a radially-bent part that is curved inwardly from the second insertion part in the radial direction of the stator core and connected to the second crown part.