Transformer cores and assembly methods thereof for high efficiency and high anti-corrosion performance

1. A transformer core, comprising:

a first plurality of laminations stacked together having a first step-lap sequence of laminations including:

a first sub-plurality of the laminations each having a first mean length that extends along a longitudinal axis, which is transverse relative to a width of each of the first sub-plurality of laminations, the first sub-plurality of the laminations each aligned longitudinally with and stacked directly to each other; and

a second sub-plurality of the laminations each having a second mean length that extends along the longitudinal axis, which is transverse relative to a width of the second sub-plurality of laminations, the second sub-plurality of the laminations each aligned longitudinally with and stacked directly to each other, the second sub-plurality of the laminations stacked directly to the first sub-plurality of the laminations;

wherein each respective one of the sub-plurality of the laminations of the first plurality of laminations is interconnected with a corresponding one of a sub-plurality of laminations of a second plurality of laminations having a second step-lap sequence of laminations to form a step-lap joint between the first plurality of laminations and the second plurality of laminations,

wherein respective lengths of the second plurality of laminations extend transversely relative to the longitudinal axis, wherein the first step-lap sequence of laminations and the second step-lap sequence of laminations are complementary with one another;

a third sub-plurality of the laminations each having a third mean length that extends along the longitudinal axis, which is transverse relative to a width of each of the third sub-plurality of laminations, the third sub-plurality of the laminations each aligned longitudinally with and stacked directly to each other, the third sub-plurality of the laminations stacked directly to the second sub-plurality of the laminations;

a fourth sub-plurality of the laminations each having a fourth mean length that extends along the longitudinal axis, which is transverse relative to a width of each of the fourth sub-plurality of laminations, the fourth sub-plurality of the laminations each aligned longitudinally with and stacked directly to each other, the fourth sub-plurality of the laminations stacked directly to the third sub-plurality of the laminations; and

a fifth sub-plurality of the laminations each having a fifth mean length that extends along the longitudinal axis, which is transverse relative to a width of each of the fifth sub-plurality of laminations, the fifth sub-plurality of the laminations each aligned longitudinally with and stacked directly to each other, the fifth sub-plurality of the laminations stacked directly to the fourth sub-plurality of the laminations;

wherein in a first sequential arrangement of a respective plurality of the first plurality of laminations and the second plurality of laminations, the first mean length is longer than the second mean length, the second mean length is longer than the third mean length, the third mean length is longer than the fourth mean length, and the fourth mean length is longer than the fifth mean length,

wherein the first sequential arrangement defines a gradual transition from a respective peak to a respective valley of a plurality of successively alternating peak and valleys defined by plurality of laminations,

wherein the respective peak is defined at least in part by the first sub-plurality of the laminations and the respective valley is defined at least in part by the fifth sub-plurality of the laminations,

wherein in a second sequential arrangement of another respective plurality of the first plurality of laminations and the second plurality of laminations, the first mean length is shorter than the second mean length, the second mean length is shorter than the third mean length, the third mean length is shorter than the fourth mean length, and the fourth mean length is shorter than the fifth mean length,

wherein the second sequential arrangement defines a gradual transition from the respective valley to a further peak of the plurality of successively alternating peak and valleys defined by the plurality of laminations.

2. The transformer core of claim 1 wherein the plurality of successively alternating peak and valleys each comprises at least four laminations.

3. The transformer core of claim 1 wherein each lamination of the plurality of laminations has a diagonally cut longitudinal end.

4. The transformer core of claim 1 wherein the first plurality of laminations comprises a vertical leg of the transformer core.

5. The transformer core of claim 4 wherein each lamination of the first plurality of laminations has a V-shaped longitudinal end.

6. The transformer core of claim 1 wherein the second plurality of laminations comprises a horizontal yoke of the transformer core.

7. The transformer core of claim 6 wherein each lamination of the second plurality of laminations comprises a V-shaped notch.

8. The transformer core of claim 1 wherein each lamination of the first plurality of laminations and each lamination of the second plurality of laminations comprises electrical steel.

9. The transformer core of claim 1 wherein the first mean length is 3 mm to 7 mm longer or shorter than the second mean length.

10. The transformer core of claim 1 wherein each lamination of the plurality of laminations has a same transverse width and the plurality of laminations are aligned transversely.

11. A transformer, comprising:

a transformer core comprising a plurality of legs, a lower yoke, and an upper yoke, each leg interconnected to the lower yoke and to the upper yoke via a step-lap joint; and

a plurality of coils, each coil surrounding a respective leg; wherein:

each leg, the lower yoke, and the upper yoke comprises a respective plurality of laminations stacked together having a step-lap sequence of laminations including:

a first sub-plurality of the laminations each having a first mean length that extends along a longitudinal axis, which is transverse relative to a width of each of the first sub-plurality of laminations, the first sub-plurality of the laminations each aligned longitudinally with and stacked directly to each other; and

a second sub-plurality of the laminations each having a second mean length that extends along the longitudinal axis, which is transverse relative to a width of each of the second sub-plurality of laminations, the second sub-plurality of the laminations each aligned longitudinally with and stacked directly to each other, the second sub-plurality of the laminations stacked directly to the first sub-plurality of the laminations;

a third sub-plurality of the laminations each having a third mean length that extends along the longitudinal axis, which is transverse relative to a width of each of the third sub-plurality of laminations, the third sub-plurality of the laminations each aligned longitudinally with and stacked directly to each other, the third sub-plurality of the laminations stacked directly to the second sub-plurality of the laminations;

a fourth sub-plurality of the laminations each having a fourth mean length that extends along the longitudinal axis, which is transverse relative to a width of each of the fourth sub-plurality of laminations, the fourth sub-plurality of the laminations each aligned longitudinally with and stacked directly to each other, the fourth sub-plurality of the laminations stacked directly to the third sub-plurality of the laminations; and

a fifth sub-plurality of the laminations each having a fifth mean length that extends along the longitudinal axis, which is transverse relative to a width of each of the fifth sub-plurality of laminations, the fifth sub-plurality of the laminations each aligned longitudinally with and stacked directly to each other, the fifth sub-plurality of the laminations stacked directly to the fourth sub-plurality of the laminations; wherein:

wherein in a first sequential arrangement of a respective plurality of the first plurality of laminations and the second plurality of laminations, the first mean length is longer than the second mean length, the second mean length is longer than the third mean length, the third mean length is longer than the fourth mean length, and the fourth mean length is longer than the fifth mean length;

wherein the first sequential arrangement defines a gradual transition from a respective peak to a respective valley of a plurality of successively alternating peak and valleys defined by the plurality of laminations,

wherein the respective peak is defined at least in part by the first sub-plurality of the laminations and the respective valley is defined at least in part by the fifth sub-plurality of the laminations,

wherein in a second sequential arrangement of another respective plurality of the first plurality of laminations and the second plurality of laminations, the first mean length is shorter than the second mean length, the second mean length is shorter than the third mean length, the third mean length is shorter than the fourth mean length, and the fourth mean length is shorter than the fifth mean length,

wherein the second sequential arrangement defines a gradual transition from the respective valley to a further peak of the plurality of successively alternating peak and valleys defined by the plurality of laminations.

12. The transformer of claim 11 wherein the plurality of legs comprises three legs and the plurality of coils comprises three coils.

13. The transformer of claim 11 wherein:

each lamination of the plurality of laminations of a first leg has a diagonally cut longitudinal end;

each lamination of the plurality of laminations of a second leg has a V-shaped longitudinal end; and

each lamination of the plurality of laminations of the upper yoke comprises a V-shaped notch.

14. A method of assembling a transformer core, comprising:

receiving a first plurality of laminations having a first step-lap sequence of laminations;

stacking directly to each other a first sub-plurality of laminations aligned longitudinally with each other and each having a first mean length that extends along a longitudinal axis, which is transverse relative to a width of each of the first sub-plurality of laminations;

stacking directly to each other a second sub-plurality of laminations aligned longitudinally with each other and each having a second mean length that extends along a longitudinal axis, which is transverse relative to a width of each of the second sub-plurality of laminations; and

stacking the second sub-plurality of the laminations directly to the first sub-plurality of the laminations;

interconnecting each respective one of the sub-plurality of the laminations of the first plurality of laminations with a corresponding one of a sub-plurality of laminations of a second plurality of laminations having a second step-lap sequence of laminations to form a step-lap joint between the first plurality of laminations and the second plurality of laminations, wherein respective lengths of the second plurality of laminations are disposed transverse relative to the longitudinal axis, wherein the first step-lap sequence of laminations and the second step-lap sequence of laminations are complementary with one another;

stacking directly to each other a third sub-plurality of the laminations aligned longitudinally with each other and each having a third mean length that extends along the longitudinal axis, which is transverse relative to a width of each of the third sub-plurality of laminations;

stacking the third sub-plurality of the laminations directly to the second sub-plurality of the laminations;

stacking directly to each other a fourth sub-plurality of the laminations aligned longitudinally with each other and each having a fourth mean length that extends along the longitudinal axis, which is transverse relative to a width of each of the fourth sub-plurality of laminations;

stacking the fourth sub-plurality of the laminations directly to the third sub-plurality of the laminations;

stacking directly to each other a fifth sub-plurality of the laminations aligned longitudinally with each other and each having a fifth mean length that extends along the longitudinal axis, which is transverse relative to a width of each of the fifth sub-plurality of laminations; and

stacking the fifth sub-plurality of the laminations directly to the fourth sub-plurality of the laminations,

wherein in a first sequential arrangement of a respective plurality of the first plurality of laminations and the second plurality of laminations, the first mean length is longer than the second mean length, the second mean length is longer than the third mean length, the third mean length is longer than the fourth mean length, and the fourth mean length is longer than the fifth mean length,

wherein the first sequential arrangement defines a gradual transition from a respective peak to a respective valley of a plurality of successively alternating peak and valleys defined by the plurality of laminations,

wherein the respective peak is defined at least in part by the first sub-plurality of the laminations and the respective valley is defined at least in part by the fifth sub-plurality of the laminations,

wherein in a second sequential arrangement of another respective plurality of the first plurality of laminations and the second plurality of laminations, the first mean length is shorter than the second mean length, the second mean length is shorter than the third mean length, the third mean length is shorter than the fourth mean length, and the fourth mean length is shorter than the fifth mean length,

wherein the second sequential arrangement defines a gradual transition from the respective valley to a further peak of the plurality of successively alternating peak and valleys defined by the plurality of laminations.

15. The method of claim 14 further comprising:

cutting diagonally a longitudinal end of each lamination of the first plurality of laminations prior to stacking; and

forming a leg of the transformer core with stacked first and second sub-pluralities of laminations of the first plurality of laminations.

16. The method of claim 14 further comprising:

cutting a V-shape at a longitudinal end of each lamination of the first plurality of laminations prior to stacking; and

forming a center leg of the transformer core with stacked first and second sub-pluralities of laminations of the first plurality of laminations.

17. The method of claim 14 further comprising:

cutting a V-shaped notch into each lamination of the second plurality of laminations prior to stacking; and

forming a yoke of the transformer core with stacked first and second sub-pluralities of laminations of the second plurality of laminations.