US3428930A

US3428930A - Laminated magnetic core structures for transformers or choke coils of great power

Info

Publication number: US3428930A
Application number: US698319A
Authority: US
Inventors: Antonius H Th J Sliepenbeek
Original assignee: Smit Nijmegen Electrotechnische Fabrieken NV
Current assignee: Smit Nijmegen Electrotechnische Fabrieken NV
Priority date: 1967-01-26
Filing date: 1968-01-16
Publication date: 1969-02-18
Anticipated expiration: 1986-02-18
Also published as: GB1217903A; CH460940A; FR1554995A; DE1638647A1; SE332456B; AT281980B; BE709737A; NL6701226A; NO121219B

Description

3,428,930 STRUCTURES FOR TRANSFOR MERS Feb. 18, 1969- A. H. TH. J. SLIEPENBEEK' LAMINATED MAGNETIC CORE OR CHOKE COILS OF GREAT POWER Filed Jan. 16, 1968 INVENT'OR Amomus H. T. J. SLFEPENBEEK 9009-162.

B y k ATTORNEYS United States Patent ()ffice 3,428,930 Patented Feb. 18, 1969 6701226 US. Cl. 336-212 2 Claims Int. Cl. H01f 27/24 ABSTRACT OF THE DISCLOSURE A laminated magnetic core has three leg members extending with their central longitudinal axes in the longi; tudinal edges of an equilateral prism, two star-shaped yoke members, each of which consists of three abutting yoke arms enclosing angles of 120, and coupling members, each of which connects an end of a leg member with the free end of a yoke arm. Each yoke arm has a central longitudinal axis which intersects, at a common point, the longitudinal axes of the remaining two yoke arms of a yoke member. In at least a part of the total number of layers of laminations of the yoke members, each yoke arm abuts the two other yoke arms with two straight end edges enclosing an angle of 120. The projections of said end edges on a line extending in the direction of the width of the yoke arm have unequal lengths. In the said layers each yoke arm consists of two laminations extending sideby-side and abutting each other with longitudinal edges which are parallel to the central longitudinal axis of the relevant yoke arm. Each one of said laminations is bounded at its end facing another yoke arm by a straight edge only, so that said laminations have widths which are equal to the said projections of said end edges, and the abutting longitudinal edges of the said two laminations of each yoke arm are in offset relation to each other in the direction of said longitudinal edges.

The invention relates to a laminated magnetic core structure for a transformer or a choke coil of great power, comprising three leg members extending with their central longitudinal axes in the longitudinal edges of an equilateral prism, two star-shaped yoke members, each of which consists of three abutting yoke arms enclosing angles of 120 and having central longitudinal axes, which intersect in a common point, and coupling members, each of which connects an end of a leg member with the free end of a yoke arm, and in which core structure in at least a part of the total number of layers of laminations of the yoke members each yoke arm abuts the two other yoke arms with two straight end edges enclosing an angle of 120, the projections of said end edges on a line extending in the direction of the width of the yoke arm having unequal lengths.

A magnetic core structure of this kind is disclosed in the US. patent specification 3,195,090 (FIGS. 4, 5a, b, c). In this known core structure each yoke arm consists in each of the said layers of a single lamination, of which the width is equal to that of the relevant yoke arm and the end edges abutting the laminations of the two other yoke arms meet in a salient angular point of 120. The yoke arms cannot be made broader than the broadest available laminations. The cutting of the laminations in the required shape causes a considerable loss of material, since the laminations cannot be fitted together to form an uninterrupted area due to their salient angular points of 120.

The invention has the object to provide a similar magnetic core structure, which has some advantages over the known core structure owing to its special construction of the yoke members. It is characterized in that in the said layers each yoke arm consists of two laminations extending side by side and abutting each other with longitudinal edges which are parallel to the central longitudinal axis of the relevant yoke arm, each one of said laminations being bounded at its end facing another yoke arm by a straight'end edge only, so that said laminations have widths which are equal to the said projections of said end edges, and the angular points defined by said end edges and the abutting longitudinal edges of the said two laminations of each yoke arm lying in offset relation to each other in the direction of said longitudinal edges. Since in this construction of the magnetic core structure each yoke arm may consist in each layer of two laminations extending side by side in respect of its longitudinal axis, said yoke arms may be made broader than the broadest laminations available. Owing to the dilferent widths and to the offset relation of the angular points at the ends of the individual sets of laminations facing the common point of intersection, the longitudinal joints between the adjacent laminations in each one of the yoke arms and the joints between the end edges of the abutting laminations of different yoke arms are overlapped in a favourable manner, if layers or groups of layers having a given arrangement of the laminations alternate with layers or groups of layers having the symmetrical arrangement of the laminations. Moreover, the yoke members can be stacked of laminations which have only two different shapes. Furthermore it is easily possible to obtain between the free ends of the yoke arms and the coupling members of the core structure a connection, in which the joints between the yoke arms and the coupling members are favourably overlapped. An important advantage is also that the laminations can be cut from strips of appropriate widths without any loss of material.

The structure constructed in accordance with the invention permits to so rotate the two end edges directed at an angle of to one another and bounding the end of a layer of a yoke arm facing the common point of intersection in respect of the longitudinal direction of said yoke arm as to make them equally long. This has the advantage that the laminations of different yoke arms abutting each other with their end edges are in contact with one another for the longest possible length and the magnetic flux is led from one lamination into the other in the most favourable way. Cavities in the magnetic core structure due to unequal lengths of said abutting end edges are then avoided.

The invention will be further elucidated with the aid of the drawing. In the drawing is:

FIG. 1 in perspective a laminated magnetic core structure according to the invention,

FIG. 2 on a larger scale a plan view of a layer of laminations of a yoke member for a magnetic core struc ture shown in FIG. 1, and

FIG. 3 on a larger scale a plan view of a layer of laminations of a variant of the yoke member shown in FIG. 2.

In FIG. 1 of the drawing three vertical leg members extending with their central longitudinal axes in the longitudinal edges of an equilateral prism are designated by 1, three horizontal yoke arms, of which the longit-udinal axes intersect in a common point 3 of intersection and enclose angles of 120 are indicated by 2 and circlecylindrically curved coupling members extending between said leg members and said yoke members are designated by 4, said leg, yoke and coupling members constituting the magnetic core structure of a transformer or a choke coil of-large power.

In each layer the leg members and the coupling members consist of two laminations of equal widths separated by a cooling gap 5 from one another. From FIG. 2 it appears that the yoke members consist in each layer of two

different laminations

6, 7 per yoke arm 2 and that said laminations have unequal widths and are each bounded by a

straight end edge

8, 9 at their ends facing the other yoke arms. Each lamination 6 of a yoke arm abuts with its end edge 8 the end edge 9 of a lamination 7 of another yoke arm 2 and vice versa. The

laminations

6 and 7 of each yoke arm abut each other with longitudinal edges 10, 11 parallel to the longitudinal axis of said yoke arm and their

end edges

8 and 9 are directed at an angle of 120 to one another and define together with said longitudinal edges 10, 11 angular points of 60, which lie in offset relation in the direction of the longitudinal axis. It will be apparent that in the core structure layers, in which the laminations of each yoke arm are arranged in a given way, alternate with layers, in which said laminations are arranged in the symmetrical way. Such a symmetrically arranged layer is indicated in FIG. 2 by dotted lines. Owing to this alternation of the layers the joints between the

end edges

8 and 9 and those between the longitudinal edges 10 and 11 of the

different laminations

6 and 7 of any layer are overlapped by

laminations

7 and 6 of adjacent layers. If, moreover, the

laminations

6 and 7 are made so long, that their

end edges

12, 13 at the free ends of the yoke arms lie in offset relation, also the joints lying in any layer between the laminations of the yoke arms 2 and those of the coupling members 4 will be overlapped by laminations of adjacent layers, so that a good mechanical connection between the yoke arms and the coupling members is possible.

In the embodiment illustrated in FIGS. 1 and 2 the

end edges

8 and 9 of the

laminations

6 and 7 do not have the same lengths. This is caused in that the angles enclosed by

said end edges

8 and 9 and said longitudinal edges 10 and 11 of those

laminations

6 and 7 are both 60, that means equal, whereas said

laminations

6 and 7 have unequal widths. The result thereof is that in the magnetic core structure there are cavities between the layers, which locally force the magnetic field from a layer into the adjacent layers. These cavities have been avoided in the construction of the yoke members shown in FIG. 3. Therein each yoke arm consists of a narrower lamination 14 having

end edges

15 and 16 and

longitudinal edges

17 and 18 and a broader lamination 19 having

end edges

20 and 21 and

longitudinal edges

22 and 23. The angle enclosed by the end edge 15 and the longitudinal edge 17 of the lamination 14 is so much smaller than 60 and the angle enclosed by the end edge 20 and the longitudinal edge 22 of the lamination 19 is so much greater than 60, as to form together an angle of 120 and to make the

end edges

15 and 20 of equal lengths. In that case also the

longitudinal edges

17 and 22 and the

longitudinal edges

18 and 23 of laminations of different yoke arms abutting each other with their

end edges

15 and 20 meet, so that the cavities are suppressed and in each layer the transition from a lamination of any given yoke arm to a lamination of another yoke arm is as favorable as possible.

It is observed, that not all layers of the yoke members need be constructed in the manner suggested in accordance with the invention. Such layers may be locally alternated in the core structure by layers, which are quite differently constructed.

What I claim is:

1. A laminated magnetic core structure for a transformer or a choke coil of great power, comprising three leg members extending with their central longitudinal axes in the longitudinal edges of an equilateral prism, two star-shaped yoke members, each of which consists of three abutting yoke arms enclosing angles of and having central longitudinal axes, which intersect in a common point, and coupling members, each of which connects an end of a leg member with the free end of a yoke arm, and in which core structure in at least a part of the total number of layers of laminations of the yoke members each yoke arm abuts the two other yoke arms with two straight end edges enclosing an angle of 120, the projections of said end edges on a line extending in the direction of the width of the yoke arm having unequal lengths, characterized in that in the said layers each yoke arm consists of two laminations extending side by side and abutting each other with longitudinal edges which are parallel to the central longitudinal axis of the relevant yoke arm, each one of said laminations being bounded at its end facing another yoke arm by a straight end edge only, so that said laminations have widths which are equal to the said projections of said end edges, and the angular points defined by said end edges and the abutting longitudinal edges of the said two laminations of each yoke arm lying in offset relation to each other in the direction of said longitudinal edges.

2. A laminated magnetic core structure according to claim 1, characterized in that in the said layers of the yoke members each yoke arm consists of two laminations, of which the end edges abutting the two other yoke arms have the same lengths.

References Cited UNITED STATES PATENTS 2,367,927 1/ 1945 Chubb 336219 XR 2,456,459 12/ 1948 Somerville 336-217 XR 2,594,001 4/1952 Ellis et a1 336-210 X R 3,195,090 7/1965 Burkhardt et al. 3362l7 XR LEWIS H. MYERS, Primary Examiner.

T. J. KOZMA, Assistant Examiner.

US. Cl. X.R. 336-217