US3688233A - Electrical inductive apparatus having serially interconnected coils - Google Patents

Electrical inductive apparatus having serially interconnected coils Download PDF

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US3688233A
US3688233A US123548A US3688233DA US3688233A US 3688233 A US3688233 A US 3688233A US 123548 A US123548 A US 123548A US 3688233D A US3688233D A US 3688233DA US 3688233 A US3688233 A US 3688233A
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conductor
finish
coils
groups
coil
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US123548A
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Harold R Moore
Harral T Robin
William B Wallace
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CBS Corp
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Westinghouse Electric Corp
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00Details of transformers or inductances, in general
    • H01F27/28Coils; Windings; Conductive connections
    • H01F27/2871Pancake coils

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  • This invention relates, in general to electrical inductive apparatus and, more specifically, to electrical inductive apparatus having serially interconnected coils.
  • the impedance of the loops aids in reducing circulating currents, but it is still important to obtain a highly efficient transposition of the conductive strands. In practice, however, ideal transpositions are impractical and undesirable circulating currents exist.
  • Circulating currents are particularly troublesome in shell-form type power transformers having a plurality of individual coils connected in series.
  • interconnection of the coils requires that the conductors forming each coil have their strands brazed together at each end of each coil. This permits currents to circulate within the individual coils. Therefore, it is desirable to provide a method whereby the circulating currents in serially interconnected coils may be reduced.
  • This invention provides a new and useful concept for reducing the total circulating current losses in a transformer winding having serially interconnected coils.
  • the conductors which form the coils of the winding are divided into at least two conductor groups.
  • the coils are connected together by alternate start-start and finish-finish connections.
  • the finish-finish connection is made in such a manner that the induced voltage due to the leakage flux in one coil group opposes the induced voltage due to the leakage flux in another coil group.
  • the resulting opposition of leakage flux voltages substantially reduces the circulating currents flowing between the conductor groups. The heat generated in the winding is reduced and the efficiency of the apparatus is improved.
  • FIG. 1 is an orthographic view of the winding and core structures of a shell form type power transformer
  • FIGS. 1A, 1B, and 1C are sectional views taken at the area A of FIG. 1 illustrating conductor strand grouping arrangements which are taught by this invention
  • FIG. 2 is a schematic diagram of a coil interconnection arrangement as taught by this invention.
  • FIG. 3 is a schematic diagram illustrating the relationship between the leakage flux induced voltages for the coils of FIG. 2;
  • FIG. 4 is a diagram illustrating an arrangement for interconnecting coils having six strands as taught by this invention
  • FIG. 5 is a diagram illustrating an arrangement for interconnecting coils having five strands as taught by this invention
  • FIG. 6 is a diagram illustrating an arrangement for interconnecting a winding having four strands as taught by this invention
  • FIG. 7 is a partial orthographic view of coils inter connected according to this invention.
  • FIG. 8 is a partial plane view illustrating the finishfrnish connection between two coils as taught by this invention.
  • FIG. 9 is a partial elevational view illustrating the finish-finish connection between two coils as taught by this invention.
  • the laminated magnetic core 10 includes the legs 12, 14 and 16 and the yokes 18 and 20.
  • the legs and yokes are formed from a plurality of laminations which are assembled around the winding structure 22.
  • the winding structure 22 includes a low voltage winding group 24, a high voltage winding group 26 and a low voltage winding group 28.
  • Each winding group comprises substantially flat rectangular coils wound with conductors spirally disposed around the core leg 14.
  • the coils of the low voltage winding group 24 are separated from each other by the insulating washers 30.
  • the coils of the low voltage winding group 28 are separated from each other by the insulating washers 32.
  • the coils of the high voltage winding group 26 are separated from each other by the insulating washers 34.
  • the conductors forming the coils may comprise one or more insulated strands or layers of strands.
  • the strands may be transposed within the coil to reduce the effects of leakage flux. Interconnection between coils and/or other winding groups.
  • the leads 36 and 38 of the winding group 24, the leads 40 and 42 of the winding group 26, and the leads 44 and 46 of the winding group 28 are all used for connecting their respective winding groups to other groups or circuits.
  • the leads 38 and 44 are brazed together at position 50 to form a series connection 48 between the low voltage winding groups 24 and 28.
  • the conductors forming the series connection 48 are divided into at least two groups. Four groups are shown in FIG. 1 to illustrate the possible methods of dividing.
  • the group 52 is brazed to the conductor group 54
  • the conductor group 56 is brazed to the conductor group 58
  • the conductor group 51 is brazed to the conductor group 53
  • the conductor group 55 is brazed to the conductor group 57.
  • Each conductor group may contain one or more conductor strands.
  • FIG. 1A is a cross-sectional view of the series connection 48 at the area A in FIG. 1 and illustrates the division of the conductor strands to reduce the effects of both the horizontal and vertical components of the leakage flux.
  • FIG. 13 illustrates a division of the conductor strands which would be used to reduce the effects of the vertical component of the leakage flux.
  • the conductor is divided into the conductor groups 59 and 61 and are brazed to similar conductor groups from the lead 44.
  • FIG. 1C illustrates a division of the conductor strands which would be used to reduce the effects of the horizontal component of the leakage flux.
  • the conductor is divided into the conductor groups 63 and 65 and are brazed to similar conductor groups from the lead 44.
  • the conductors are bent as shown so that the conductor groups of the low voltage winding group 24 are electrically connected to the conductor groups of the low voltage winding group 28 which are at opposite radial and axial positions. This effectively provides a transposition of the conductor groups by the series connection 48. The result is that the voltages which are developed in the conductor groups of each low voltage winding group due to the leakage flux oppose each other. This reduces the circulating currents, the heating of the winding, and the losses of the transformer.
  • FIG. 2 Electrical connections for serially interconnected winding groups are illustrated in FIG. 2.
  • the coils 60, 62, 64 and 66 are shown moved to the side of each otherfor clarity. Physically, the coils would be aligned over each other. This can be visualized by moving the coil 62 to the left so that is is directly over the coil 60, by moving the coil 64 so that it is directly over the coils 62 and 60, and by moving the coil 66 so that it is directly over the coils 64, 62 and 60.
  • the coils 60 and 62 are interconnected by the start-start connection 68
  • the coils 64 and 66 are interconnected by the start-start connection 70
  • the coils 62 and 64 are interconnected by the finish-finish connection 72.
  • the coils 60, 62, 64 and 66 are shown wound with the conductors 74, 76, 78 and 80, respectively.
  • Each conductor may comprise a plurality of insulated strands or layers of strands.
  • the coils of FIG. 2 each have six strands.
  • the coils may contain conductor strand transpositions. Methods for making the transpositions within the coils are described in U.S. Pat. No. 3,283,280, patented Nov. 1, 1966, and in pending application Ser. No. 876,769, filedNov. l4,
  • the coils 60, 62, 64 and 66 may comprise more than one coil turn. However, the single coil turn shown in FIG. 2 is sufficient to illustrate the invention.
  • the conductor strands 90, 92, 94, 96, 98 and 100 of the coil 60 are electrically connected at the braze position 102, to which is connected a winding lead 104.
  • the conductor strands 106, 108, 110, 112, 114 and 116 of the coil 66 are electrically connected at the braze position 118, to which is connected a winding lead 120.
  • the braze positions 122 and 124 electrically divide the conductor 74 into two conductor groups, 126 and 128, respectively.
  • the braze positions 130, 132, 134 and 136 electrically divide the conductor 76 into two conductor groups 138 and 140.
  • the braze positions 142, 144, 146 and 148 electrically divide the conductor 78 into two conductor groups, 150 and 152.
  • the braze positions 154 and 156 electrically divide the conductor 80 into two conductor groups, 154 and 156 respectively.
  • conductor strand transpositions such as described in U.S. Pat. No. 3,283,280, would eliminate the circulating currents due to one component of the leakage flux and the pattern of the remaining component would result in negligible losses.
  • the transpositions cannot be placed at the ideal location for zero losses due to one component of the leakage flux and the pattern of the other component deviates considerably from the ideal case. Therefore, the voltages induced in the conductor groups 126 and 128 of the conductors 74 are not equal.
  • a similar relation exists between the conductor groups 138 and of the conductor 76, the conductor groups and 152 of the conductor 78, and the conductor groups 154 and 156 of the conductor 80.
  • FIG. 3 schematically represents the conductors of FIG. 2.
  • the conductor group 128 may, at an instant of time, have an induced voltage with an amplitude different than the voltage induced in the conductor group 126. The difference is denoted by e, with the polarity as shown.
  • similar voltages are induced in the conductor groups 138, 150 and 160 and denoted as e e;, and e, respectively. Since e e e and e are substantially equal in amplitude, the reversal characteristic furnished by the finish-finish connection 72 causes the closed loop voltage to be approximately equal to zero. Thus, circulating currents between the conductor groups are effectively reduced.
  • FIG. 4 illustrates, in abbreviated form, an interconnection arrangement for coils having conductors comprising six strands or strand groups.
  • the leads 162 and 164 are connected to the finish conductor turns of the coils 166 and 172, respectively.
  • the coils 166 and 168 are interconnected by the start-start connection 174 and the coils 170 and 172 are interconnected by the start-start connection 176.
  • the start-start connections 174 and 176 are made so that the conductor groups of adjacent coils are electrically connected to each other at the same radial position within the conductor.
  • the finish-finish connection 178 interconnects the coils 168 and 170 so that the conductor groups are transposed.
  • FIG. 5 illustrates, in abbreviated form, an interconnection arrangement for coils having conductors comprising five strands or strand groups.
  • the leads 180 and 182 are connected to the finish conductor turns of the coils 184 and 190, respectively.
  • the coils 184 and 186 are interconnected by the start-start connection 192 and the coils 188 and 190 are interconnected by the start-start connection 194.
  • the start-start connections 192 and 194 are made so that the conductor groups of adjacent coils are electrically connected to each other at the same radial position within the conductor.
  • the finish-finish connection 196 interconnects the coils 186 and 188 so that the conductor groups are transposed.
  • FIG. 6 illustrates, in abbreviated form, an interconnection arrangement for coils having conductors comprising four strands or strand groups.
  • the leads 198 and 200 are connected to the finish conductor turns of the coils 202 and 216, respectively.
  • the coils 202 and 204 are interconnected by the start-start connection 218, the coils 206 and 208 are interconnected by the startstart connection 220, the coils 210 and 212 are interconnected by the start-start connection 222, and the coils 214 and 216 are interconnected by the start-start connection 224.
  • the start-start connections 218, 220, 222 and 224 are made so that the conductor groups of adjacent coils are electrically connected to each other at the same radial position within the conductor.
  • the coils 204 and 206 are interconnected by the finishfinish connection 226 and the coils 212 and 214 are interconnected by the finish-finish connection 230.
  • the coils 208 and 210 are interconnected by the connection 228, which may be either a finish-finish connection or a series connection.
  • the connection 228 would be a finish-finish connection if the coils 202, 204, 206, 208, 210, 212, 214 and 216 are all contained within the same winding group.
  • the connection 228 would be a series connection if the coils 208 and 210 are contained in different winding groups.
  • FIG. 7 is a simplified view of four coils which are interconnected as taught by this invention. All insulating members are eliminated from the figure to show the interconnections more clearly. For the same reason, the coils are shown having a larger separation distance than they would normally have in a' power transformer windmg.
  • the coil 232 is shown wound with four turns of the conductor 234.
  • the conductor is electrically divided into the conductor groups 236 and 238. Each conductor group may contain more than one insulated strand.
  • the coils 232 and 234 are interconnected by a startstart connection which is not shown in the figure.
  • a similar start-start connection interconnects the coils 236 and 238.
  • the conductor groups 240 and 242 of the coil 234 are electrically connected to the conductor groups 244 and 246 of the coil 236 at the positions 248 and 250.
  • This finish-finish connection serially interconnects the four coils 232, 234, 236 and 238 and transposes the conductor groups according to this invention.
  • FIG. 8 is a plane view of an arrangement for making the finish-finish connection between adjacent coils.
  • the conductor forming the upper coil 251 as shown in FIG. 8 consists of the insulated strands 252, 254, 256 and 258.
  • the conductor forming the lower coil consists of the strands 260, 262, 264 and 266.
  • the conductors are grouped into pairs and are brazed as pairs at the positions 268 and 270.
  • the strands which are near the braze positions are secured by a means such as the tie 272.
  • the spacer blocks 276 are attached to the insulating washer 274, which is notched to make the interconnection of the conductor groups more convenient.
  • FIG. 9 is an elevational view of the interconnecting arrangement of FIG. 8.
  • the conductor groups from the upper coil 251 and the lower coil 253 are bent and pulled toward each other and brazed at the positions 268 and 270.
  • the exposed braze positions 268 and 270 may be wrapped with an insulating material.
  • interconnection arrangements which may be used to reduce the circulation currents in a winding. This is accomplished by interconnecting the winding groups and/or the coils within a winding group so that the leakage flux induced voltages oppose each other.
  • a power transformer comprising a shell-form type laminated magnetic core, a pancake-type winding structure disposed in inductive relationship with said laminated magnetic core, said winding structure having a plurality of winding groups which are physically separated by at least one other winding group, said separated winding groups each having first, second, third and fourth pancake-type coils, each of said coils having at least one conductor spirally wound for a plurality of coil turns, said conductor having a plurality of insulated strands, said insulated strands being grouped together to form a plurality of conductor groups with the conductor groups positioned at different radial positions in said conductor, each of said conductor g groups having a plurality of insulated strands said conductor groups having said strands electrically connected together at the beginning position of the start turn of said coil and at the ending position of the finish turn of said coil, said second and third coils being electrically interconnected by a finish-finish connection, said first and second coils being electrically interconnected by a start-start connection, said
  • winding groups are electrically interconnected by a series connection which electrically connects together conductor groups which are at radially opposite positions within the conductors of the winding groups.
  • the power transformer of claim 1 including an insulating washer which separates coils that are electrically interconnected by a finish-finish connection, said insulating washer having at least one notch therein, the conductor groups of the finish-finish connection ex- 5 tending through said notch with selected conductor groups being electrically connected together.

Abstract

Electrical inductive apparatus having pancake-type coils which are serially interconnected to form a winding group. The conductors forming the coils in the winding group are divided into at least two conductor groups by unique lead brazing techniques. Adjacent coils are interconnected by alternate startstart and finish-finish connections. The transposition furnished by the finish-finish connection reduces the circulating currents in the coils due to leakage flux.

Description

United States Patent Moore et al. Aug.x29, 1972 [54] ELECTRICAL INDUCTIVE 3,023,386 2/1962 Wentz et a1 ..336/187 APPARATUS HAVING SERIALLY 1,872,247 8/1936 Cole et al ..336/187 N INTERCONNECTED COILS 3,348,182 10/1967 Baker et a1. ..336/187 [721 a g i" $323??? 153?? 512$;siiiiiiiiiiiiia iif i 3' 3,467,931 9/1969 Dotton ..336/87 x [7 Assigneer Westinghouse Electric Corporation, Pn'mary Examiner-Thomas J. Kozma Plttsburgh, Attorney-AT. Stratton and F. E Browder [22] Filed: March 12, 1971 ABSTRACT [21] Appl. No.: 123,548
Electrical inductive apparatus having pancake-type coils which are serially interconnected to form a wind [52] US. Cl ..336/183, 336/187 ing group The conductors mi h c l i [51] hit. Cl ..H01t 27/28 winding group are divided into at least two conductor [58] Field of Search, ..336/186l87, 69, 703, 180, groups by unique lead brazing techniques Adjacent 36/182 185 coils are interconnected by alternate start-start and fmish-finish connections. The transposition furnished [56] References Cmd by the finish-finish connection reduces the circulating UNITED STATES PATENTS currents in the coils due to leakage flux.
3,183,465 5/1965 Moore ..336/187 3 Claims, 12 Drawing Figures ELECTRICAL INDUCTIVE APPARATUS HAVING SERIALLY INTERCONNECTED COILS CROSS REFERENCE TO RELATED APPLICATION In copending application Westinghouse Case No. 42,664, Ser. No. 123,590, filed Mar. 12, 1971, and assigned to the same assignee as this application, there is disclosed an arrangement for serially interconnecting the windings of electrical inductive apparatus.
BACKGROUND OF THE INVENTION 1 Field of the Invention This invention relates, in general to electrical inductive apparatus and, more specifically, to electrical inductive apparatus having serially interconnected coils.
2. Description of the Prior Art Electrical inductive apparatus operating at high power levels exhibits various effects which reduce the efficiency and reliability of the apparatus. Prominent among these is the heating of the conductors due to eddy-current losses. Eddy-current losses in a conductor of a transformer winding are proportional to the square of the dimension of the conductor which is at right angles to the leakage flux. Eddy-current losses may thus be reduced by subdividing the required conductor area into two or more parallel connected conductive elements or strands, which are insulated from each other. To prevent an offsetting increase in losses due to circulating currents between the parallel connected strands, the relative position of the strands are transposed with respect to the leakage flux, in an attempt to obtain the same net flux linkages for each strand. If the parallel loops are long, the impedance of the loops aids in reducing circulating currents, but it is still important to obtain a highly efficient transposition of the conductive strands. In practice, however, ideal transpositions are impractical and undesirable circulating currents exist.
Circulating currents are particularly troublesome in shell-form type power transformers having a plurality of individual coils connected in series. According to the prior art, interconnection of the coils requires that the conductors forming each coil have their strands brazed together at each end of each coil. This permits currents to circulate within the individual coils. Therefore, it is desirable to provide a method whereby the circulating currents in serially interconnected coils may be reduced.
SUMMARY OF THE INVENTION This invention provides a new and useful concept for reducing the total circulating current losses in a transformer winding having serially interconnected coils. The conductors which form the coils of the winding are divided into at least two conductor groups. The coils are connected together by alternate start-start and finish-finish connections. The finish-finish connection is made in such a manner that the induced voltage due to the leakage flux in one coil group opposes the induced voltage due to the leakage flux in another coil group. The resulting opposition of leakage flux voltages substantially reduces the circulating currents flowing between the conductor groups. The heat generated in the winding is reduced and the efficiency of the apparatus is improved.
2 BRIEF DESCRIPTION OF THE DRAWING Further advantages and uses of this invention will become more apparent when considered in view of the following detailed description and drawing, in which:
FIG. 1 is an orthographic view of the winding and core structures of a shell form type power transformer;
FIGS. 1A, 1B, and 1C are sectional views taken at the area A of FIG. 1 illustrating conductor strand grouping arrangements which are taught by this invention;
FIG. 2 is a schematic diagram of a coil interconnection arrangement as taught by this invention;
FIG. 3 is a schematic diagram illustrating the relationship between the leakage flux induced voltages for the coils of FIG. 2;
FIG. 4 is a diagram illustrating an arrangement for interconnecting coils having six strands as taught by this invention;
FIG. 5 is a diagram illustrating an arrangement for interconnecting coils having five strands as taught by this invention;
FIG. 6 is a diagram illustrating an arrangement for interconnecting a winding having four strands as taught by this invention;
FIG. 7 is a partial orthographic view of coils inter connected according to this invention;
FIG. 8 is a partial plane view illustrating the finishfrnish connection between two coils as taught by this invention; and
FIG. 9 is a partial elevational view illustrating the finish-finish connection between two coils as taught by this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Throughout the following description similar reference characters refer to similar members in all figures of the drawing.
Referring now to the drawing, and FIG. 1 in particular, there is shown the electric and magnetic structures of a shell-form type power transformer. The laminated magnetic core 10 includes the legs 12, 14 and 16 and the yokes 18 and 20. The legs and yokes are formed from a plurality of laminations which are assembled around the winding structure 22.
The winding structure 22 includes a low voltage winding group 24, a high voltage winding group 26 and a low voltage winding group 28. Each winding group comprises substantially flat rectangular coils wound with conductors spirally disposed around the core leg 14. The coils of the low voltage winding group 24 are separated from each other by the insulating washers 30. The coils of the low voltage winding group 28 are separated from each other by the insulating washers 32.
The coils of the high voltage winding group 26 are separated from each other by the insulating washers 34.
The conductors forming the coils may comprise one or more insulated strands or layers of strands. The strands may be transposed within the coil to reduce the effects of leakage flux. Interconnection between coils and/or other winding groups. The leads 36 and 38 of the winding group 24, the leads 40 and 42 of the winding group 26, and the leads 44 and 46 of the winding group 28 are all used for connecting their respective winding groups to other groups or circuits.
The leads 38 and 44 are brazed together at position 50 to form a series connection 48 between the low voltage winding groups 24 and 28. The conductors forming the series connection 48 are divided into at least two groups. Four groups are shown in FIG. 1 to illustrate the possible methods of dividing. The group 52 is brazed to the conductor group 54, the conductor group 56 is brazed to the conductor group 58, the conductor group 51 is brazed to the conductor group 53, and the conductor group 55 is brazed to the conductor group 57. Each conductor group may contain one or more conductor strands.
FIG. 1A is a cross-sectional view of the series connection 48 at the area A in FIG. 1 and illustrates the division of the conductor strands to reduce the effects of both the horizontal and vertical components of the leakage flux. FIG. 13 illustrates a division of the conductor strands which would be used to reduce the effects of the vertical component of the leakage flux. The conductor is divided into the conductor groups 59 and 61 and are brazed to similar conductor groups from the lead 44. FIG. 1C illustrates a division of the conductor strands which would be used to reduce the effects of the horizontal component of the leakage flux. The conductor is divided into the conductor groups 63 and 65 and are brazed to similar conductor groups from the lead 44.
The conductors are bent as shown so that the conductor groups of the low voltage winding group 24 are electrically connected to the conductor groups of the low voltage winding group 28 which are at opposite radial and axial positions. This effectively provides a transposition of the conductor groups by the series connection 48. The result is that the voltages which are developed in the conductor groups of each low voltage winding group due to the leakage flux oppose each other. This reduces the circulating currents, the heating of the winding, and the losses of the transformer.
Electrical connections for serially interconnected winding groups are illustrated in FIG. 2. The coils 60, 62, 64 and 66 are shown moved to the side of each otherfor clarity. Physically, the coils would be aligned over each other. This can be visualized by moving the coil 62 to the left so that is is directly over the coil 60, by moving the coil 64 so that it is directly over the coils 62 and 60, and by moving the coil 66 so that it is directly over the coils 64, 62 and 60. The coils 60 and 62 are interconnected by the start-start connection 68, the coils 64 and 66 are interconnected by the start-start connection 70, and the coils 62 and 64 are interconnected by the finish-finish connection 72.
The coils 60, 62, 64 and 66 are shown wound with the conductors 74, 76, 78 and 80, respectively. Each conductor may comprise a plurality of insulated strands or layers of strands. The coils of FIG. 2 each have six strands. Although not illustrated, the coils may contain conductor strand transpositions. Methods for making the transpositions within the coils are described in U.S. Pat. No. 3,283,280, patented Nov. 1, 1966, and in pending application Ser. No. 876,769, filedNov. l4,
1969, now U.S. Pat. No. 3,602,860, both being assigned to the same assignee as this invention. The coils 60, 62, 64 and 66 may comprise more than one coil turn. However, the single coil turn shown in FIG. 2 is sufficient to illustrate the invention.
The conductor strands 90, 92, 94, 96, 98 and 100 of the coil 60 are electrically connected at the braze position 102, to which is connected a winding lead 104. The conductor strands 106, 108, 110, 112, 114 and 116 of the coil 66 are electrically connected at the braze position 118, to which is connected a winding lead 120. The braze positions 122 and 124 electrically divide the conductor 74 into two conductor groups, 126 and 128, respectively. The braze positions 130, 132, 134 and 136 electrically divide the conductor 76 into two conductor groups 138 and 140. The braze positions 142, 144, 146 and 148 electrically divide the conductor 78 into two conductor groups, 150 and 152. The braze positions 154 and 156 electrically divide the conductor 80 into two conductor groups, 154 and 156 respectively.
Ideally, conductor strand transpositions, such as described in U.S. Pat. No. 3,283,280, would eliminate the circulating currents due to one component of the leakage flux and the pattern of the remaining component would result in negligible losses. In reality, the transpositions cannot be placed at the ideal location for zero losses due to one component of the leakage flux and the pattern of the other component deviates considerably from the ideal case. Therefore, the voltages induced in the conductor groups 126 and 128 of the conductors 74 are not equal. A similar relation exists between the conductor groups 138 and of the conductor 76, the conductor groups and 152 of the conductor 78, and the conductor groups 154 and 156 of the conductor 80. By transposing the finsh-finish connection 72, as shown, the difference voltages substantially cancel each other.
FIG. 3 schematically represents the conductors of FIG. 2. The conductor group 128 may, at an instant of time, have an induced voltage with an amplitude different than the voltage induced in the conductor group 126. The difference is denoted by e, with the polarity as shown. At the same instant of time, similar voltages are induced in the conductor groups 138, 150 and 160 and denoted as e e;, and e,, respectively. Since e e e and e are substantially equal in amplitude, the reversal characteristic furnished by the finish-finish connection 72 causes the closed loop voltage to be approximately equal to zero. Thus, circulating currents between the conductor groups are effectively reduced.
FIG. 4 illustrates, in abbreviated form, an interconnection arrangement for coils having conductors comprising six strands or strand groups. The leads 162 and 164 are connected to the finish conductor turns of the coils 166 and 172, respectively. The coils 166 and 168 are interconnected by the start-start connection 174 and the coils 170 and 172 are interconnected by the start-start connection 176. The start- start connections 174 and 176 are made so that the conductor groups of adjacent coils are electrically connected to each other at the same radial position within the conductor. The finish-finish connection 178 interconnects the coils 168 and 170 so that the conductor groups are transposed.
FIG. 5 illustrates, in abbreviated form, an interconnection arrangement for coils having conductors comprising five strands or strand groups. The leads 180 and 182 are connected to the finish conductor turns of the coils 184 and 190, respectively. The coils 184 and 186 are interconnected by the start-start connection 192 and the coils 188 and 190 are interconnected by the start-start connection 194. The start- start connections 192 and 194 are made so that the conductor groups of adjacent coils are electrically connected to each other at the same radial position within the conductor. The finish-finish connection 196 interconnects the coils 186 and 188 so that the conductor groups are transposed.
FIG. 6 illustrates, in abbreviated form, an interconnection arrangement for coils having conductors comprising four strands or strand groups. The leads 198 and 200 are connected to the finish conductor turns of the coils 202 and 216, respectively. The coils 202 and 204 are interconnected by the start-start connection 218, the coils 206 and 208 are interconnected by the startstart connection 220, the coils 210 and 212 are interconnected by the start-start connection 222, and the coils 214 and 216 are interconnected by the start-start connection 224. The start- start connections 218, 220, 222 and 224 are made so that the conductor groups of adjacent coils are electrically connected to each other at the same radial position within the conductor. The coils 204 and 206 are interconnected by the finishfinish connection 226 and the coils 212 and 214 are interconnected by the finish-finish connection 230. The coils 208 and 210 are interconnected by the connection 228, which may be either a finish-finish connection or a series connection. The connection 228 would be a finish-finish connection if the coils 202, 204, 206, 208, 210, 212, 214 and 216 are all contained within the same winding group. The connection 228 would be a series connection if the coils 208 and 210 are contained in different winding groups.
FIG. 7 is a simplified view of four coils which are interconnected as taught by this invention. All insulating members are eliminated from the figure to show the interconnections more clearly. For the same reason, the coils are shown having a larger separation distance than they would normally have in a' power transformer windmg.
The coil 232 is shown wound with four turns of the conductor 234. The conductor is electrically divided into the conductor groups 236 and 238. Each conductor group may contain more than one insulated strand. The coils 232 and 234 are interconnected by a startstart connection which is not shown in the figure. A similar start-start connection interconnects the coils 236 and 238. The conductor groups 240 and 242 of the coil 234 are electrically connected to the conductor groups 244 and 246 of the coil 236 at the positions 248 and 250. This finish-finish connection serially interconnects the four coils 232, 234, 236 and 238 and transposes the conductor groups according to this invention.
FIG. 8 is a plane view of an arrangement for making the finish-finish connection between adjacent coils. The conductor forming the upper coil 251 as shown in FIG. 8 consists of the insulated strands 252, 254, 256 and 258. The conductor forming the lower coil consists of the strands 260, 262, 264 and 266. The conductors are grouped into pairs and are brazed as pairs at the positions 268 and 270. The strands which are near the braze positions are secured by a means such as the tie 272. The spacer blocks 276 are attached to the insulating washer 274, which is notched to make the interconnection of the conductor groups more convenient.
FIG. 9 is an elevational view of the interconnecting arrangement of FIG. 8. The conductor groups from the upper coil 251 and the lower coil 253 are bent and pulled toward each other and brazed at the positions 268 and 270. Although not shown, the exposed braze positions 268 and 270 may be wrapped with an insulating material.
In summary, there has been described interconnection arrangements which may be used to reduce the circulation currents in a winding. This is accomplished by interconnecting the winding groups and/or the coils within a winding group so that the leakage flux induced voltages oppose each other.
We claim as our invention:
1. A power transformer comprising a shell-form type laminated magnetic core, a pancake-type winding structure disposed in inductive relationship with said laminated magnetic core, said winding structure having a plurality of winding groups which are physically separated by at least one other winding group, said separated winding groups each having first, second, third and fourth pancake-type coils, each of said coils having at least one conductor spirally wound for a plurality of coil turns, said conductor having a plurality of insulated strands, said insulated strands being grouped together to form a plurality of conductor groups with the conductor groups positioned at different radial positions in said conductor, each of said conductor g groups having a plurality of insulated strands said conductor groups having said strands electrically connected together at the beginning position of the start turn of said coil and at the ending position of the finish turn of said coil, said second and third coils being electrically interconnected by a finish-finish connection, said first and second coils being electrically interconnected by a start-start connection, said third and fourth coils being electrically interconnected by a start-start connection, said finish-finish connection serially interconnecting said coils, said finish-finish connection electrically connecting together all of the conductor groups from said second coil to the conductor groups from said third coil which are at radially opposite positions within the conductors when the conductors have an even number of conductor groups, said finish-finish connection electrically connecting together all of the conductor groups from said second coil, except a middle conductor group, to the conductor groups from said third coil which are at radially opposite positions within the conductors when the conductors have an odd number of conductor groups, said start-start connections electrically connecting together all of the conductor groups from one coil to the conductor groups from the other coil which are radially at the same position within the conductors.
2. The power transformer of claim 1 wherein the winding groups are electrically interconnected bya series connection which electrically connects together conductor groups which are at radially opposite positions within the conductors of the winding groups.
3. The power transformer of claim 1 including an insulating washer which separates coils that are electrically interconnected by a finish-finish connection, said insulating washer having at least one notch therein, the conductor groups of the finish-finish connection ex- 5 tending through said notch with selected conductor groups being electrically connected together.

Claims (3)

1. A power transformer comprising a shell-form type laminated magnetic core, a pancake-type winding structure disposed in inductive relationship with said laminated magnetic core, said winding structure having a plurality of winding groups which are physically separated by at least one other winding group, said separated winding groups each having first, second, third and fourth pancake-type coils, each of said coils having at least one conductor spirally wound for a plurality of coil turns, said conductor having a plurality of insulated strands, said insulated strands being grouped together to form a plurality of conductor groups with the conductor groups positioned at different radial positions in said conductor, each of said conductor groups having a plurality of insulated strands said conductor groups having said strands electrically connected together at the beginning position of the start turn of said coil and at the ending position of the finish turn of said coil, said second and third coils being electrically interconnected by a finish-finish connection, said first and second coils being electrically interconnected by a start-start connection, said third and fourth coils being electrically interconnected by a start-start connection, said finish-finish connection serially interconnecting said coils, said finish-fInish connection electrically connecting together all of the conductor groups from said second coil to the conductor groups from said third coil which are at radially opposite positions within the conductors when the conductors have an even number of conductor groups, said finish-finish connection electrically connecting together all of the conductor groups from said second coil, except a middle conductor group, to the conductor groups from said third coil which are at radially opposite positions within the conductors when the conductors have an odd number of conductor groups, said start-start connections electrically connecting together all of the conductor groups from one coil to the conductor groups from the other coil which are radially at the same position within the conductors.
2. The power transformer of claim 1 wherein the winding groups are electrically interconnected by a series connection which electrically connects together conductor groups which are at radially opposite positions within the conductors of the winding groups.
3. The power transformer of claim 1 including an insulating washer which separates coils that are electrically interconnected by a finish-finish connection, said insulating washer having at least one notch therein, the conductor groups of the finish-finish connection extending through said notch with selected conductor groups being electrically connected together.
US123548A 1971-03-12 1971-03-12 Electrical inductive apparatus having serially interconnected coils Expired - Lifetime US3688233A (en)

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US3925743A (en) * 1974-10-23 1975-12-09 Westinghouse Electric Corp Interleaved winding for electrical inductive apparatus
US4460885A (en) * 1981-07-29 1984-07-17 Westinghouse Electric Corp. Power transformer
US4859978A (en) * 1988-04-29 1989-08-22 Electric Power Research Institute, Inc. High-voltage windings for shell-form power transformers
US4864266A (en) * 1988-04-29 1989-09-05 Electric Power Research Institute, Inc. High-voltage winding for core-form power transformers
US5304767A (en) * 1992-11-13 1994-04-19 Gas Research Institute Low emission induction heating coil
US5508674A (en) * 1992-03-25 1996-04-16 Electric Power Research Institute, Inc. Core-form transformer
US5786575A (en) * 1995-12-20 1998-07-28 Gas Research Institute Wrap tool for magnetic field-responsive heat-fusible pipe couplings
US20070057753A1 (en) * 2005-09-14 2007-03-15 Kuo Shu F Apparatus and method for modifying properties of a substance
US20120325806A1 (en) * 2010-01-06 2012-12-27 Sumitomo Metal Industries, Ltd. Induction heating coil, and an apparatus and method for manufacturing a worked member

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3925743A (en) * 1974-10-23 1975-12-09 Westinghouse Electric Corp Interleaved winding for electrical inductive apparatus
US4460885A (en) * 1981-07-29 1984-07-17 Westinghouse Electric Corp. Power transformer
US4859978A (en) * 1988-04-29 1989-08-22 Electric Power Research Institute, Inc. High-voltage windings for shell-form power transformers
US4864266A (en) * 1988-04-29 1989-09-05 Electric Power Research Institute, Inc. High-voltage winding for core-form power transformers
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US5508674A (en) * 1992-03-25 1996-04-16 Electric Power Research Institute, Inc. Core-form transformer
US5304767A (en) * 1992-11-13 1994-04-19 Gas Research Institute Low emission induction heating coil
US5786575A (en) * 1995-12-20 1998-07-28 Gas Research Institute Wrap tool for magnetic field-responsive heat-fusible pipe couplings
US20070057753A1 (en) * 2005-09-14 2007-03-15 Kuo Shu F Apparatus and method for modifying properties of a substance
US20120325806A1 (en) * 2010-01-06 2012-12-27 Sumitomo Metal Industries, Ltd. Induction heating coil, and an apparatus and method for manufacturing a worked member
US9604272B2 (en) * 2010-01-06 2017-03-28 Nippon Steel & Sumitomo Metal Corporation Induction heating coil, and an apparatus and method for manufacturing a worked member
US10406581B2 (en) 2010-01-06 2019-09-10 Nippon Steel Corporation Method for manufacturing a worked member using an induction heating coil

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AU3861472A (en) 1973-08-09
BE780468A (en) 1972-09-11

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