US2467824A - Magnetic core - Google Patents

Description

April 19, 1949.

J. C. GRANFIELD MAGNETIC CORE 2 She ets-Sheet 1 Filed Jan. 9, 1947 Inventzon John C. Granfield.

His AbEorney- April 1949- J. c. GRANFIELD MAGNETIC CORE 2 Sheets-Sheet 2 Filed Jan. 9, 1947 Inventor.

John C. Granfield,

H is Atlc ofney.

Patented Apr. 19, 1949 UNITED STATES PATENT OFFICE MAGNETIC com:

John C. Granfield, Pittsfleld, Mass, assignor to General Electric Company, a corporation of New York Application January 9, 1947, Serial No. 721,045

11 Claims.

This invention relates to magnetic cores and more particularly to improvements in stacked cores of the split or divided lamination type.

By split or divided laminations is meant that the legs or yokes or both in certain of the lamination layers consist of a plurality of parallel punchings or lamination pieces. In other words, the total width of the split part of the layer is made up of two or more relatively narrow lamination pieces whose total width is equal to thequires very much more force to insert a wide yoke lamination thanit does to successivel insert two narrow laminations between the ends of the leg laniiriations. A further advantage is that it provides an improved flux path as compared with standard overlapping joints of solid cores in which the laminations are not split without requiringthe additional cost and complexity or mitering the joints. This is particularly important when highly grain oriented magnetic mate rial is used. As the core is split, it is more difficult for flux to travel across the grain or cross wise of the most favorable magnetic direction as the barrier produced by the split prevents such cross migration of the flux. Consequently, the flux travels with the grain throughout a greater percentage of the mean length turn of the core.

- Also, the narrower laminations reduce the eddy current losses in the core.

The invention is characterized by having two of the lamination pieces which form one portion of a core layer make a joint with the same lamination piece which forms another portion of the same layer, in at least alternate layers of the core. It is further characterized by having the butt joints between the laminations in each layer offset or overlapped in contiguous layers so that there are no aligned butt joints throughout the thickness of the core.

Cores made in accordance with the invention have been found to have lower losses than equal size cores in which the laminations are unsplit Thus large cores having relatively 2 and standard square cut overlapping joints are used.

An object of the invention is to provide an improved split core for electric induction apparatus.

Another object of the invention is to reduce the cost and losses of large size stacked cores made of magnetic strip material having a highly favorable magnetic direction parallel to the lengthwise dimension of the strip.

The invention will be better understood from following description taken in connection" with the accompanying drawings and its scope will be pointed out in the appended claims.

In the drawings, Fig. l is a partially exploded perspective view of a three phase core having split legs and solid yokes and in which the adja cent layers are different; Fig. 2 is a similar ar tial view of a three phase core in which both the legs and yokes are split and in which all of the layers are the same; Fig. 3 is a modification of Fig. 2 in which the adjacent layers are differ ent; Fig. 4 is a similar view of a single phase core having solid yokes and split legs in which all of the layers are the same; Fig. 5 is a similar view er a single phase core in which both the legs and yokes are split and the adjacent layers are differ ent; Fig. 6 is a similar view of a three phase ccre in which both the legs and yokes are split three ways and in which adjacent layers are different;

.- Fig. 7 is a similar view of a single phase core in which both the legs and yokes are split three ways and in which adjacent layers are diiierent, and

Fig. 8 is a modification of Fig. 5.

Referring now to the drawings and more partlcularly to Fig. '1, the core is shown as comprising a plurality of superposed lamination layers in which the top layer I has been lifted off 'the stack to reveal the second layer 2. The third layer and all other odd numbered layers are the same as layer l and the fourth layer and all other even numbered layers are the same as layer 2. The layers are, of course, of the same external outline or configuration and each defines two windows 3 and 4 by means of three parallel legs 5, 6 and I and. two yokes 8 and 9 The widths of the correspondingly numbered legs and yokes in each layer are the same and ordinarily the widths of all the legs will be the same and will be equal to the widths of the yokes. In layer I and all odd numbered layers, the outer legs 5 and I are each split into relatively long narrow outer strip l0 and relatively short wide inner strip H. The middle leg 6 is split into a narrow strip [0 and a strip l2 which is of the same width as the strips .and all of the layers are the same. end of the top layer which has been shown lifted H but which is equal in length to strip HI. The yokes 8 and 8 each comprise duplicate strips l3 which are the full width of the yokes. It will be.

observed with each outer corner that the two legged strips l and II each make butt contact with a yoke strip I3. In layer 2 and all the other even numbered layers, the outer legs and I are split into long wide outer strips l2 and long narrow inner strips Hi. The middle leg is split into a wide left hand strip II and narrow right hand strip [4 which is the same width as the strips l0 and the same length as the strips II. The yokes 8 and 9 consist of'one piece strips l5 which are the same width as the yoke pieces l3 but which run from the inside of one outer leg to the width of the other outer leg.

It will be observed that none of the butt joints in layers l and 2 will coincide with each other when the layers are superposed. It will also be observed that due to the reversal of the widths of the strips in the legs of adjacent layers, the split in the legs is also overlapped or offset in adjacent layers.

It will be observed that in layer 2, the outer leg strips l2 do not make butt contact with the yoke strips l5. This could readily be accomplished by cutting off the inner leg strips [0 along the dotted lines and extending the ends of the yoke strips G5 to make contact with the outer leg strips [2. However, if that were done, then the butt joints formed at the dotted lines between the ends of the shortened inner leg strips ill and the yoke strips i5 would be in registration' with the inner portion of the butt joints between the yoke strips l3 and the inner wide leg strips ii in layer I so that, in effect, there would be a partial butt joint throughout the entire thickness of the core.

As has been explained above, the benefits derived from splitting the core increase with the ,size of the core and the width of the leg and yoke portions of the lamination layers. Consequently the core shown in Fig. 1 may either be considered as a single width core or else it may be considered as the wide central portion of a so- ;called stepped or cruciform cross section core in which groups of progressively narrower width -laminations are placed on both sides of the wide stack shown in the drawing so as to form the steps.

The offsetting or overlapping of the steps in .the legs tends to hold the core tightly together and prevent the looseness which might occur if the widths of the two parts of the legs were not reversed in adjacent layers.

In Fig. 2, both the legs and the yokes are split Thus, the

off the stack is the same as the opposite end (not shown) of the second layer which is on the top of the stack. In other words, every other layer is rotated 180 about a central axis perpendicular to the plane of the lamination layer. The left hand leg of the lifted off layer of odd numbered layers is split into a wide strip I6 and a narrow strip I1 and respective duplicates of these strips form the right hand leg of the second and all even numbredlayers. Likewise, the right hand leg of the top and all odd numbered layers and the left hand leg of the second and all even numbered layers are made from wide strips l8 and narrow strips l9 which preferably correspond respectively in width to the strips l6 and. H. The center legs are made of wide full length strips l8 .and narrow short length strips which have the same width as the strips l6 and 20. Strips 20 are preferably the same width as the strips l1 and I9. The right hand and left hand parts of the yokes are different from each other at each end and the two ends are also different from each other so that the layers are not symmetrical. The end of the top lifted off layer and all odd numbered layers which is shown, corresponds with the-left hand end of the second and all even numbered layers, which are not shown, and it is characterized by having wide punchings 2i and 22 on the outside and narrow punchings 23 and 24 on the inside, punchings 2| and 23 being adjacent each other and being of different lengths and the punchings 22 and 24 being adjacent each other and being of the same length. Opposite ends of the layers, one of which is shown in the second layer has narrow punchings 25 and 28 on the outside and has wide punchings 22 and 21 on the inside. It will be observed that the same size punching 22 is used at both ends of each layer. The lengths of the adjacent wide and narrow punchings, which are shown in the second layer, are difierent for each pair.

It will be observed in Fig. 2 that at each corner of each layer either one leg punching makes contact with at least two yoke punchings or else one yoke punching makes contact with at least two leg punchings. Thus, at the right hand corner of the lifted on layer the long strip or punching i9 makes contact with both punchings 22 and 24 while at the opposite corner of the same layer, leg strip ll makes contact with both yoke punchings 2i and 23. Also, in the right hand corner the yoke punching 2d makes contact with both leg punchings i8 and i9 and in the opposite corner the yoke punching 25 makes contact with both leg punchings l6 and ii. Similar relationships exist at the other end of the layers as shown in the illustrated and of the second layer.

In the modification shown in Fig. 3, the adjacent layers are different from each other in internal configuration. That is to say, all the odd numbered layers are of one kind and all the even numbered layers are of another kind. Thus, the odd numbered layers starting with the lifted off layer l have narrow strips as on the outside of both the outer legs and have wide strips 29 on .the inside of those legs whereas the even numbered layers have wide strips 39 on the outside of the outer legs and narrow strips 3! on the inside of the outer legs. The ends of the layers, which are not shown, are identical respectively with the ends of those layers which are shown. Thus, the opposite end of the lifted off layer is the same as the end which is shown and the same is true for the second layer. The odd numbered layers have wide strips 32 on the right in the center leg which strips are not quite as long as the core. The even numbered layers have wide strips 33 on the left which are the full length of the core. Both center legs have narrow strips 343 of the same shape except that they are on the left in the odd numbered layers and on the right in the even numbered layers, as the core is viewed in the drawing. The inside to outside relationship of the widths of the portions of the yokes in each layer correspond to the same relationship for the outer legs of those layers. Thus, in the odd numbered layers, narrow strips 35 and 36 are on the outside and wide strips 31 and 38 are on they inside whereas in the even numbered layers, wide strips 39 and as are on the outside and narrow strips 4i and 42 are on the inside- As in the other figures, the corners of the layers and the core are characterized by multiple contact between one punching or lamination strip and one portion of the core and a plurality of punchings or lamination strips in another portion of the core and the butt Joints do not register in contiguous layers and are overlapped in all such layers.

Fig. 4 is similar to Fig. 1 in that the legs only are split and the yokes are unsplit but this is a single phase core and in addition it differs from Fig. 1 in that the layers are all the same. Furthermore, these layers are symmetrical about a lateral axis or center line. One leg of each layer consists of a full length narrow strip 43 on the outside and a full length wide strip 44 on the inside. The other leg consists of another full length wide strip 44 on the outside and a narrow short strip 45 on the inside. The yokes consist of identical punchings 46 which have a width equal to the combined width of the wide and narrow leg punchings. The layers are not symmetrical about their longitudinal center line or axis, and successive layers are rotated 180 about such axis or about an axis perpendicular to the plane of the laminations so as to provide overlapping of all joints. It will be seen that at each corner at least one layer of each pair of contiguous layers has a yoke punching which makes contact with both leg punchings because yoke punching 46 makes contact with both leg punchings 44 and 45 and as the laminations are successively reversed, this relationship' will occur in each pair of contiguous layers at each corner. g

In Fig. 5, there is a single phase core in which both the legs and yokes are split. In this core, theodd numbered layers are all of one kind and the even numbered layers are all of another kind.

-The legsof the top and all odd numbered layers,

may be made of duplicate wide full length outer punchings 4d, one of which is associated with a short length narrow punching and the other of which is associated with an intermediate length narrow punching ii. The yoke consists of a wide inner punching 48 and a narrow outer punching 49. The opposite end of the top layer has not been shown but isthe same as the endwhich has been shown. In the even numbered layers, the legs comprise full length narrow outer strips 43 A with one of which is associated a short length inner wide strip and the other of which is associated with a medium length wide strip 5 i. The yoke of these layers has a wide outer strip 52 and narrow innerstrip '53. Opposite ends of the even numbered layers are the same as the end which has been shown. a

The core of Fig. l5,"like the other figures, is characterized by complete overlapping of all butt joints and multiple contact between the ends of punchings of the leg and yoke portions. Thus, in the top lifted ofi layer both leg strips 44 and 41 make contact with the same yoke strip 49 and the yoke strip 48 makes contact with both leg strips 44 and 45. In the even numbered layers corresponding relationships exist.

In Fig. 6, there is a three way rather than a two way split three phase core in which both the yokes andthe legs are split into three parallel strips or punchings in each layer. The odd numbered layers are all of one kind and the even numbered layers are all of a different kind. The two opposite ends of any one layer are the same so that only one end of each of the two kinds of layers has been shown. The narrowest strips, which all may be of the same width, are desi nated by the same reference number 54 in all of the legs and yokes. Although, of course, it will be obvious from the drawing that these narrowest length strips are of varying lengths but in view of the descriptions of the previous figures, it is believed the details regarding the differences in lengths of the various pieces will be obvious from the drawing so that it is unnecessary to assign a different number to each different length piece of the same width. The intermediate width strips or punchings in all of the portions of the core are designated by the numeral 55. Likewise, the widest strips in all the portions'of the core are designated by the numeral 56.

' Fig. 6 is characterized by the same complete overlappin of the butt joints in contiguous layers and the multiple contacts of strips or punchings at the corners.

Fig. '7 is a single'phase core which is essentially the same as Fig. 6 except that the middle leg has been omitted and the yoke punchings extend con tinuously between the two outer legs. The different width punchings or strips are designated as in Fig. 6.

In the modification of Fig. 5 shown in Fig. 8, the opposite ends of the same lamination layer are different instead of being the same so that a complete odd numbered layer has been shown lifted off to reveal a complete even numbered layer beneath it. correspondingly numbered parts 51, 58, 59 and are respectively the same in all layers and these constitute what may be called the outer zone of each layer, there being two narrow parts 51 and 58 forming one corner andtwo wide parts 59 and 60 forminga diagonally-opposite corner. f

In the odd numbered layers,..the inner. zone comprises two wide strips Si and 52'and two narrow strips 63 and .54 while in the even numbered layers, the'inner zone comprises two wide strips 65 and 66 which are different in length respectively- The inner 1 length of'members 62 and 68 is the san e. Like-' wise, the length of the members iii and El isthe same and the length of members 63 and 65 is-the same.

The superposition layers causes complete overlapping of all the butt joints in the layers and as will be seen in each layer there is multiple contact at the corners between various lamination pieces of different portions of the core.

While there have been shown and described particular embodiments of the invention, it will be obvious to those skilled in the art that changes and modifications can be made without departing from the invention and therefore it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A core including superposed fiat lamination layers each having at least two leg and two yoke portions, the leg portions being split longitudinally into at least two different width pieces of magnetic strip material, the yoke portions comprising at least one piece of magnetic strip material, the lengths of said pieces in one of every pair of contiguous leg layers being different, said different length pieces being in contact with the same yoke piece.

However, it.will be observed that the lengthof the outer even numbered 2. A core including superposed flat lamination layers each having at least two leg and two yoke portions, the leg portions being split longitudinally into at least two different width pieces of magnetic strip material, the yoke portions comprising at least one piece of magnetic strip material, the lengths of said pieces in one of every pair of contiguous leg portions being different, said different length pieces being in contact with the same yoke piece, one set of alternate layers being similar to each other and different from the remaining set of alternate layers which in turn are similar to each other.

3. A core including superposed 'fiat lamination layers each having at least two leg and two yoke portions, the leg portions being split longitudinally into at least two different width pieces of magnetic strip material, the yoke portions comprising at least one piece of magnetic strip material, the lengths of said pieces in one of every pair of con tiguous leg portions being different, said different length pieces being in contact with the same yoke piece, all of said layers being identical in structure, one alternate set of layers being reversed in" position relative to the remaining set of intermediate layers.

4. A core including superposed flat lamination layers each having at least two leg and two yoke portions, the leg portions being split longitudinally into at least two different width pieces of magnetic strip material, the yoke portions each comprising full width pieces of magnetic strip material, the lengths of said pieces in one of every pair of contiguous leg portions being different, said different length leg pieces being in contact with the same yoke pieces.

5. A core including superposed fiat lamination layers each having at least two leg and two yoke portions each forming four corners by means of butt joints, the leg portions being longitudinally split into parallel strips, the yoke portions being strips of the full width of the yokes, at each corner one alternate set of layers having the leg strips extend out to the edge of the layer with the end of the yoke strip in contact with the inner leg strip only and in the remaining layers the outer leg strip only extending out to the edge of the layer with the end of the with both of the leg strips.

6. A three phase core including superposed lamination layers each having three split legs and two unsplit yokes, the three legs being in the same planeand parallel to each other whereby there are two outer legs and an inner leg, each outer leg comprising an outer strip and an inner strip, the even numbered layers starting at a given layer in the core having full length outer legs between which the yokes extend with a shorter inner leg which extends between the yokes, the odd numbered layers having a full lengthcenter leg from both ends of which the yokes extend laterally in opposite directions with full length outer strips on the outer legs between which the yokes extend and With'shorter inner strips on the outer legs which extend between the yokes.

7. A core including superposed fiat lamination layers each having at least two leg and two yoke yoke strip in contact portions, the leg portions and the yoke portions being split longitudinally into at least two different width pieces of magnetic strip material, the

length of said pieces in one of every pair of contiguous leg portions being different, said diflerent length leg pieces being in contact with the same yoke piece, the lengths of said pieces in one of every pair of contiguous yoke portions being different, said different length yoke pieces being in contact with the same leg piece.

8. A core including superposed flat lamination layers each having at least two leg and two yoke portions, the leg and yoke portions being split longitudinally into three different width pieces of magnetic strip material, the widest piece being between the other two pieces in all the legs and yokes, said widest pieces in each leg and yoke being intermediate in length to the pieces on both sides thereof, the narrowest pieces being on the outside of the legs and on the inside of the yokes in one set of alternate layers and the narrowest pieces being on the inside of the legs and on the outside of the yokes in the remaining set of alternate layers.

9. A three phase core including superposed fiat lamination layers each having three legs and two yokes, the legs and yokes being split longitudinally into three diiferent width pieces of magnetic strip material, the widest strips being between the other strips in all of the legs and yokes, the narrowest strips being on the outside of the outer legs and on the inside of the yokes in one set of alternate layers, the narrowest strips being on the inside of the outer legs and on the outside of the yokes in the other set of alternate layers, the relative positions of the narrowest strips being reversed in the center legs of successive layers.

10. A core including superposed flat lamination layers each having at least two leg and two yoke portions, the leg portions and the yoke portions being split longitudinally into at least two difierent width pieces of magnetic strip material, the lengths of the difierent width pieces in each leg and yoke portion being difierent, the ends of said pieces fitting snugly together in square butt joints.

11. A core including similar superposed flat lamination layers each having at least two leg and two yoke portions, the leg portions and the yoke portions being split longitudinally into at least two different width pieces of magnetic strip material, the lengths of the different width pieces in each leg and yoke portion being different, the ends of said pieces in adjacent portions of each layer fitting snugly together in square butt joints, said layers having four difierent corners one of which has the widest pieces on the inside and the narrowest pieces on the outside, the diagonally opposite corner having the narrowest pieces on the inside and the widest pieces on the outside, the third corner having one wide piece and one narrow piece on the outside and one wide piece and one narrow piece on the inside, the last corner having the same width relationship but having the relative lengths of the different width pieces reversed, alternate layers being reversed.

JOHN C. GRANFIELD.

REFERENCES CITED The following references are file of this patent:

UNITED STATES PATENTS of record in the

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