US2594001A - Three-phase core - Google Patents

Description

April 22, 1952 B. B. ELLIS EIAL THREE-PHASE CORE 2 SHEETSSHEET 2 Filed July 9, 1949 Fig. 8. r

Fig. 7.

s R O T N E V m Belvin B. Ellis, Clifford C. Horsrmon 8 Charles E Burkhordl WITNESSES:

Patented Apr. 22, 1952 THREE-PHASE CORE Belvin B. Ellis, Sharon, and

and Charles E. Burkhardt, signors to Westinghouse East Pittsburgh, Pa., a

sylvania Clifford C. Horstman Sharpsville, Pa., as- Electric Corporation,

corporation of Penn Application July 9, 1949, Serial No. 103,863

2 Claims. (Cl. 175356) This invention relates to three-phase core structures;

Heretofore, Y and T-core structures have been produced having low sound level characteristics and satisfactory magnetic values. Numerous joint structures have been developed in attempts to lower the magnetic losses but such joint structures, particularly in the yoke area, have not enabled the reduction of magnetic losses to a value approaching the losses of the magnetic material without joints therein.

An object of this invention is the production or three-phase core structures having excellent sound level characteristics and low magnetic losses.

Another object of this invention is to provide a three-phase core structure having inserts of magnetic materials in the yoke areas thereof for increasing the amount of magnetic material in the yoke joint areato thereby effect a reduction in the induction at the joints.

A further object of this invention is to provide inserts of magnetic material alternately with the laminations of a three-phase core structure in the yoke area thereof to substantially double the amount of magnetic material in the yoke joint area over that in any one of the winding legs of the core structure;

Other objects of this invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which:

Figure 1 is a view in perspective of a threephase Y-core structure embodying the teachings of this invention;

Figs. 2, 3, 4 and 5 are plan views of the assembly of successive layers'of laminations in the yoke area of'the core structure of Fig. 1;

Fig. 6 is a view in perspective of a three-phase T-core structure embodying the teachings of this invention; and

Figs. 7, 8 and 9 are plan view of the assembly of successive layers of laminations in the yoke area of the core structure of Fig. 6.

Referring to Figure 1 of the drawings, this invention is illustrated by reference to a threephase Y-core structure l0 formed of bundles l2, I4 and I6 of laminations of magnetic material, the magnetic material being preferably silicon iron alloy strip material processed to have a preferred orientation of the grain structure in the direction of the strips or laminations. Each bundle I2, I 4 and I6 is similarly formed, being bent flatwise of the laminations so that when assembled in nested relation the bundles are provided with winding legs [8, 20 and 22, respectively, and turned end portions 24-46, 28-30 and 32- 34, respectively.

Each of the winding legs I3, 23 and 22 is provided with offset joints 36 and 38 in the alternate laminations thereof to facilitate separation of the upper core section from the lower core section when the windings (not shown) are to be positioned in assembled relation with the Winding legs. Each of the bundles l2, l4 and iii is provided with the same number of laminations so that corresponding laminations of the end portions will form a layer in the'yoke area.

As illustrated more clearly in Figs. 2, 3 and 4, one of the end portions of each layer of laminations is cut or otherwise formed to have a pointed end 39, the edges of the pointed end being cut at angles of 30 to the direction of the lamination to provide a pointed end. Thus in Fig. 2, the end portion 32 is provided with the pointed end 39, whereas end portions 24 and 28 are provided with square out edges at an angle of to the direction of thelaminations to butt against the cut edges of the pointed end 39 of end portion 32. The end portions 24, 28 and 32 thus extend outwardly from the yoke joint area thus formed at angles of from each other to provide a symmetrical pattern for the core structure.

The second layer of end portion laminations is similarly formed except that the end portion lamination having the pointed end 39 is disposed 120 away from the pointed end lamination of the first or external layer. Thus, as shown in Fig. 3, the end portion lamination 24 of the second layer is provided with the pointed end 39 for cooperating with the square cut ends of the end portion laminations of the second layer of end portions 28 and 32 to provide a symmetrical yoke area.

Similarly, the third layer of end portion laminations is formed of two square cut end portions 24 and 32, the third end portion lamination 28 being provided with the pointed end 39 for butting against the square out edges of end portions 24 and 32. Thus, in the third layer illustrated in Fig. 4, the pointed end portion 28 is disposed 120 from the pointed end portions of the first and second layer of end portion laminations.

Where the bundles l2, l4 and I6 are thus formed with certain of the end portion laminations having pointed ends and being offset relative to adjacent end portion laminations so that when assembled the layers of the end portion laminations are successively formed of yoke areas shown in Figs. 2, 3 and 4 repeated a required number of times, it is seen that the pointed end 39 of one of the end portion laminations of each layer overlaps one of the butt joints between two of the end portion laminations of adjacent layers.

In order to introduce more magnetic material in theyoke core area to decrease the induction at the joint area, an insert 40 of magnetic material, preferably silicon iron alloy strip material, is positioned between adjacent layers of the end portion laminations in interleaved relation therewith to overlap the joints formed in each of the adjacent layers. The inserts 40 preferably have a thickness equal to that of the laminations forming bundles l2, l4 and 16 so that when assembled with respect to the joints between the laminations of the cooperative end portions 242B32 and 26--30--34, each of the yoke areas thus formed has a height substantially equivalent to twice the thickness of a winding leg of one of the bundles l2, M or I6.

In practice, the inserts 40 for the Y-core structure ID are formed into the shape of an equilateral triangle as illustrated in Figs. 1 and 5, the triangular inserts 40, being so cut from magnetic strip material having a preferred grain orientation that the preferred direction is in a direction perpendicular to one of the sides of the triangle and that the inserts are of a size to overlap the joints. In assembling the inserts 40, each successive insert is progressively turned or displaced 120 from the preceding insert so that the magnetic directions of the successive inserts are symmetrically oriented to give good magnetic properties in three directions disposed 120 with respect to each other throughout the height of the yoke area. Thus the grain orientation of each of the inserts 40 is in the same direction as the grain orientation of one of the end portion laminations of the two adjacent layers between which the insert is disposed, the pointed ends 39 of the end portion laminations of the two layers being disposed 120 apart. Such structure gives an efiicient overlap joint structure resulting in a lowered induction with a resulting reduction in iron loss.

This invention may also be applied to T-core structures as illustrated in Figs. 6, 7, 8 and 9. In this embodiment, two of the bundles 42 and 44 of the flatwise bent and nested laminations formed as described in connection with the Y- core of Fig. 1 to have winding legs 46 and end portions 5052 and 54-56, respectively, have alternate end portion laminations offset relative to each other, as shown in Figs. 7 and 8, and are disposed in a vertical plane taken through the winding legs thereof with the end portions 50 and 52 facing the end portions 54 and 56, respectively. A third bundle 58 having a winding leg 60 and end portions 62 and 64 is disposed perpendicular to the other two bundles, the end portions 62 and 64 of bundle 53 being formed of laminations which are alternately cut at the ends thereof at 45 to the direction of the laminations so that the adjacent laminations thereof have pointed ends 63 and 65 which are offset relative to each other.

Thus referring to Fig. '7, the external lamination of end portion 50 is square cut whereas the external lamination of end portion 54 is cut at an angle of 45 to the direction of the lamination, whereby the cut edge forming pointed end 63 of the external lamination of end portion 62 will cooperate therewith to form a closed butt joint yoke area layer.

The second layer of the end portion laminations is illustrated in Fig. 8, the lamination of end portion 54 in this instance being square cut across its end whereas the end of the lamination of end portion 50 is cut at an angle of 45 to the direction of the lamination. In this layer, the cut of the end of the lamination of end portion 62 is reversed to the cut of the first layer whereby the pointed end 65 of the second lamination of the end portion 62 cooperates with the second lamination of each of end portions 50 and 54 to form a closed butt joint yoke area layer, the joints of which are in overlapped relation with the butt joints of the first layer of the yoke area as illustrated in Fig. 9.

In the embodiment illustrated in Figs. 6 and 9, square cut inserts 66 are disposed between adjacent layers of the laminations of the end por-- tions in the yoke areas, the inserts being of a size to overlap the butt joints in such yoke areas. The inserts 66 are formed of oriented silicon iron sheet, the direction of orientation preferably be ing in the direction of the aligned end portions of bundles 42 and 44 whereby two of the laminations of adjacent layers will have an orientation in the same direction as the orientation of the inserts. However, where desired, the alternate inserts 66 may be turned so that the orientation of every second insert is aligned with the grain orientation of the laminations of end portion 62.

When assembled with the inserts 66 disposed in the yoke area between adjacent laminations of the end portions of bundles 42, 44 and 58, the common yoke areas have a height or thickness substantially equivalent to twice the thickness of one of the winding legs of the bundles 42, 44 and 58. The bundles 42, 44 and 58 are maintained in assembled relation by means of steel bands 68 and 10 which extend about the winding legs and end portions of the assembled bundles, the bands crossing at the yoke core areas and being held in position by coupling members 12 in a wellknown manner.

This invention makes possible the construction of Y and T-core structures which have excellent sound level characteristics together with 7 low magnetic losses. The addition of the inserts having a preferred orientation interleaved between the adjacent layers of end portion laminations as described hereinbefore permits the flux produced in such core structures when used as transformer cores, to flow or pass through the critical yoke joints formed in the common yoke areas at a lower flux density thereby keeping the iron loss of the core at a value more nearly that value found in testing overlap Epstein samples of the magnetic material. The increase in the magnetic material in the yoke joint area and the overlap joints thereby formed effectively lowers the induction at the joint correspondingly and the losses decreased in accordance with the lower induction.

While reference has been made herein to lami tive in that they are shown relatively thicker than would normally be used in practice in order to clearly illustrate this invention.

We claim as our invention:

1. A three-phase magnetic core comprising, three generally U-shaped bundles of laminations of magnetic strip material having a preferred grain orientation in the direction of the laminations and bent flatwise of the laminations to form a winding leg and turned end portions for each of the bundles, the corresponding end portions of the bundles having the ends of certain of the laminations thereof offset with respect to the others and shaped whereby the ends fit together to form butt and lap joints in adjacent layers with the end portions positioned to form common Y-shaped yoke areas, and inserts of magnetic sheet material disposed between adjacent layers of the corresponding end portion laminations to overlap the butt joints of the corresponding adjacent layers in the common yoke areas, the inserts having a preferred grain orientation to provide a most favorable magnetic direction therein, the inserts between the successive ad jaoent layers of the laminations being progressively turned 120 apart in assembled relation with the layers of laminations whereby the most favorable magnetic direction of the inserts between the successive adjacent layers of laminations is progressively rotated 120, the inserts between the adjacent layers of the laminations being of substantially the same thickness as that of each of the end portion laminations to give each of the common yoke areas a height substantially equivalent to twice the thickness of the winding leg of one of the individual bundles.

2. A three-phase magnetic core comprising, three generally U-shaped bundles of laminations of magnetic strip material having a preferred grain orientation in the direction of the laminations and bent fiatwise of the laminations to form a winding leg and turned end portions for each of the bundles, corresponding layers of the corresponding end portion laminations of the three bundles having their ends cut to fit together in butt joint relation with each other in common yoke areas, and inserts of magnetic sheet material disposed between adjacent layers of the corresponding end portion laminations to overlap the butt joints of the corresponding adjacent layers in the common yoke areas, the inserts having a preferred grain orientation to provide a most favorable magnetic direction therein, the inserts between the successive adjacent layers of the laminations being progressively turned apart in assembled relation with the layers of laminations whereby the most favorable magnetic direction of the inserts between the successive adjacent layers of laminations is progressively rotated 120, the inserts being of substantially the same thickness as that of each of the end portion laminations to give each of the common yoke areas a height substantially equivalent to twice the thickness of the winding leg of one of the individual bundles.

BELVIN B. ELLIS. CLIFFORD C. HORSTMAN. CHARLES E. BURKHARDT.

REFERENCES CITED The following references are of record in the file of this patent:

108,862 Austria Feb. 10, 1928

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