Bar wound stator winding layout with long-pitched and short-pitched coils

1. A stator assembly comprising:

a plurality of stator slots defining a plurality of slot layers;

a plurality of hairpins each having a respective first leg positioned in one of the plurality of slot layers and a respective second leg positioned in another of the plurality of slot layers, each of the plurality of hairpins being configured to allow a current to flow from the respective first leg to the respective second leg;

wherein each of the plurality of hairpins is one of a short-pitched coil, a long-pitched coil and a full-pitched coil;

wherein the short-pitched, long-pitched and full-pitched coils are configured to extend over a first, second and third number of the plurality of stator slots, respectively, the first number being less than the second number and the third number being between the first and second numbers;

wherein the plurality of hairpins is divided into a plurality of hairpin layers;

wherein one of the first, second, third, fourth, fifth and sixth hairpin layers includes at least one of the short-pitched coils;

wherein another of the first, second, third, fourth, fifth and sixth hairpin layers includes at least one of the long-pitched coils;

wherein the plurality of hairpin layers includes first, second, third, fourth, fifth and sixth hairpin layers and the plurality of slot layers includes first, second, third, fourth, fifth and sixth slot layers;

wherein the plurality of hairpins form first, second and third winding sets;

wherein the first winding set is formed from the plurality of hairpins in the first and second hairpin layers;

wherein the second winding set is formed from the plurality of hairpins in the third and fourth hairpin layers; and

wherein the third winding set is formed from the plurality of hairpins in the fifth and sixth hairpin layers.

2. The stator assembly of claim 1 , wherein the assembly is characterized by an absence of respective hairpin-to-hairpin slot liners between the plurality of hairpins.

3. The stator assembly of claim 1 , wherein:

a first set of three adjacent slots of the plurality of stator slots is configured to accommodate the plurality of hairpins carrying the current with a first phase;

a second set of three adjacent slots of the plurality of stator slots is configured to accommodate the plurality of hairpins carrying the current with a second phase; and

a third set of three adjacent slots of the plurality of stator slots is configured to accommodate the plurality of hairpins carrying the current with a third phase.

4. The stator assembly of claim 1 , wherein:

the first hairpin layer is defined by the plurality of hairpins with the respective first leg in the first slot layer and the respective second leg in the second slot layer;

the second hairpin layer is defined by the plurality of hairpins with the respective first leg in the second slot layer and the respective second leg in the first slot layer;

the third hairpin layer is defined by the plurality of hairpins with the respective first leg in the third slot layer and the respective second leg in the fourth slot layer;

the fourth hairpin layer is defined by the plurality of hairpins with the respective first leg in the fourth slot layer and the respective second leg in the third slot layer;

the fifth hairpin layer is defined by the plurality of hairpins with the respective first leg in the fifth slot layer and the respective second leg in the sixth slot layer; and

the sixth hairpin layer is defined by the plurality of hairpins with the respective first leg in the sixth slot layer and the respective second leg in the fifth slot layer.

5. The stator assembly of claim 1 , wherein:

the first, third and fifth hairpin layers each include at least two short-pitched coils; and

the second, fourth and sixth hairpin layers each include at least two long-pitched coils.

6. The stator assembly of claim 1 , wherein the first, second, third, fourth, fifth and sixth hairpin layers each include at least one full-pitched coil extending over a third number of the plurality of stator slots, the third number being greater than the first number and less than the second number.

7. The stator assembly of claim 6 , wherein the first, second and third numbers are 8, 10 and 9, respectively.

8. The stator assembly of claim 1 , wherein:

the first winding set includes 12 of the plurality of hairpins from the first hairpin layer connected in series with 12 of the plurality of hairpins from the second hairpin layer;

the second winding set includes 12 of the plurality of hairpins from the third hairpin layer connected in series with 12 of the plurality of hairpins from the fourth hairpin layer; and

the third winding set includes 12 of the plurality of hairpins from the fifth hairpin layer connected in series with 12 of the plurality of hairpins from the sixth hairpin layer.

9. The stator assembly of claim 1 , wherein each of the first, second and third winding sets defines an identical number of multiple phases; and the plurality of stator slots includes exactly 72 slots.

10. An electric machine comprising:

a stator assembly;

a rotor assembly rotatable relative to the stator assembly;

wherein the stator assembly includes:

a plurality of stator slots defining first, second, third, fourth, fifth and sixth slot layers;

a plurality of hairpins each having a respective first leg positioned in one of the first, second, third, fourth, fifth and sixth slot layers and a respective second leg positioned in another of the first, second, third, fourth, fifth and sixth slot layers;

wherein each of the plurality of hairpins is configured to allow a current to flow from the respective first leg to the respective second leg;

wherein each of the plurality of hairpins is one of a short-pitched coil, a long-pitched coil and a full-pitched coil;

wherein the short-pitched, long-pitched and full-pitched coils are configured to extend over a first, second and third number of the plurality of stator slots, respectively, the first number being less than the second number and the third number being between the first and second numbers;

wherein the plurality of hairpins is divided into first, second, third, fourth, fifth and sixth hairpin layers;

wherein the first, third and fifth hairpin layers each include at least two of the short-pitched coils; and

wherein the second, fourth and sixth hairpin layers each include at least two of the long-pitched coils;

wherein the first hairpin layer is defined by the plurality of hairpins with the respective first leg in the first slot layer and the respective second leg in the second slot layer;

wherein the second hairpin layer is defined by the plurality of hairpins with the respective first leg in the second slot layer and the respective second leg in the first slot layer;

wherein the third hairpin layer is defined by the plurality of hairpins with the respective first leg in the third slot layer and the respective second leg in the fourth slot layer;

wherein the fourth hairpin layer is defined by the plurality of hairpins with the respective first leg in the fourth slot layer and the respective second leg in the third slot layer;

wherein the fifth hairpin layer is defined by the plurality of hairpins with the respective first leg in the fifth slot layer and the respective second leg in the sixth slot layer; and

wherein the sixth hairpin layer is defined by the plurality of hairpins with the respective first leg in the sixth slot layer and the respective second leg in the fifth slot layer.

11. The machine of claim 10 , wherein the first, second, third, fourth, fifth and sixth hairpin layers each include at least one of the full-pitched coils.

12. The machine of claim 10 , wherein the first, second and third numbers are 8, 10 and 9, respectively.

13. The machine of claim 12 , wherein the first, second and third numbers are 5, 7 and 6, respectively; and wherein the plurality of stator slots includes exactly 48 slots.

14. The machine of claim 10 , wherein the assembly is characterized by an absence of respective hairpin-to-hairpin slot liners between the plurality of hairpins.

15. The machine of claim 10 , wherein:

a first set of three adjacent slots of the plurality of stator slots is configured to accommodate the plurality of hairpins carrying the current with a first phase;

a second set of three adjacent slots of the plurality of stator slots is configured to accommodate the plurality of hairpins carrying the current with a second phase; and

a third set of three adjacent slots of the plurality of stator slots is configured to accommodate the plurality of hairpins carrying the current with a third phase.

16. An electric machine comprising:

a stator assembly;

a rotor assembly rotatable relative to the stator assembly;

wherein the stator assembly includes:

a plurality of stator slots defining first, second, third, fourth, fifth and sixth slot layers;

a plurality of hairpins each having a respective first leg positioned in one of the first, second, third, fourth, fifth and sixth slot layers and a respective second leg positioned in another of the first, second, third, fourth, fifth and sixth slot layers;

wherein each of the plurality of hairpins is configured to allow a current to flow from the respective first leg to the respective second leg;

wherein the plurality of hairpins is divided into first, second, third, fourth, fifth and sixth hairpin layers;

wherein the plurality of hairpins form first, second and third winding sets, each of the first, second and third winding sets being parallel to one another;

wherein the first winding set is formed from the plurality of hairpins in the first and second hairpin layers;

wherein the second winding set is formed from the plurality of hairpins in the third and fourth hairpin layers;

wherein the third winding set is formed from the plurality of hairpins in the fifth and sixth hairpin layers;

wherein the first, third and fifth hairpin layers each include at least two short-pitched coils configured to extend over a first number of the plurality of stator slots; and

wherein the second, fourth and sixth hairpin layers each include at least two long-pitched coils configured to extend over a second number of the plurality of stator slots; the second number being greater than the first number.