Abstract:
The coupling coil structure, which is provided with a plurality of primary coils formed by winding a conductor wire and a plurality of secondary coils provided so as to generate mutual inductance with the plurality of primary coils and in which, among the plurality of primary coils, one primary coil is tapped at an intermediate portion thereof by another primary coil at right angles, is characterized in that, among the plurality of secondary coils, a secondary coil in mutual inductance with the one primary coil is constituted into a coupling coil by one conductor having a width at least the size in the axial direction of the primary coil.

Description:
TECHNICAL FIELD 
       [0001]    An embodiment of the present invention relates to a coupling coil structure and a transformer. 
       BACKGROUND ART 
       [0002]    Conventionally, in a Scott-connected transformer or the like, for example, a coupling coil has been employed for the following reason: That is, a Scott-connected transformer  10  shown, for example, in  FIG. 5  includes an iron core  11 , a main-phase primary coil  12 , a teaser primary coil  13 , a main-phase secondary coil  14 , and a teaser secondary coil  15 . Each of the coils  12 ,  13 ,  14 , and  15  is configured such that a conductor wire is wound around the iron core  11 . One end of the teaser primary coil  13  intersects and is connected to the main-phase primary coil  12  at a middle point N thereof, which is a midway portion thereof. A three-phase power supply that is not shown is connected to a terminal V of the teaser primary coil  13  and terminals U and W of the main-phase primary coil  12 . 
         [0003]    A first single-phase load  91  is connected to terminals  1   u  and  1   v  of the main-phase secondary coil  14 , which is one of the secondary coils  14  and  15 . A second single-phase load  92  is connected to terminals  2   u  and  2   v  of the teaser secondary coil  15 . The voltage outputted from the main-phase secondary coil  14  and the voltage outputted from the teaser secondary coil  15  are shifted from each other by a phase difference of 90°. In this case, mutual induction occurs between the main-phase primary coil  12  and the main-phase secondary coil  14  and between the teaser primary coil  13  and the teaser secondary coil  15 . 
         [0004]      FIG. 6  shows current flowing through the Scott-connected transformer  10  in  FIG. 5  in a state in which only the first single-phase load  91  is connected to the terminals  1   u  and  1   v  of the main-phase secondary coil  14  but the second single-phase load  92  is not connected to the terminals  2   u  and  2   v  of the teaser secondary coil  15 . Current i 1   m  flowing through the main-phase primary coil  12  and current i 2   m  flowing through the main-phase secondary coil  14  flow in such a way that the ampere-turns of the two coils  12  and  14  cancel each other out. In this case, the short-circuit impedance in the main-phase primary coil  12  and the main-phase secondary coil  14  is the leakage impedance between the two coils  12  and  14 . 
         [0005]    In contrast,  FIG. 7  shows current flowing through the Scott-connected transformer  10  in  FIG. 5  in a state in which only the second single-phase load  92  is connected to the terminals  2   u  and  2   v  of the teaser secondary coil  15  but the first single-phase load  91  is not connected to the terminals  1   u  and  1   v  of the main-phase secondary coil  14 . Current i 1   t  flowing through the teaser primary coil  13  flows so as to cancel the ampere-turns of current i 2   t  flowing through the teaser secondary coil  15  and then splits at the middle point N into current i 1   t   1  and current i 1   t   2 , which flow through the main-phase primary coil  12 . 
         [0006]    In this case, the short-circuit impedance on the teaser side is the sum of the leakage impedance between the teaser primary coil  13  and the teaser secondary coil  15  and the leakage impedance between a U-side main-phase primary coil  121  and a W-side main-phase primary coil  122 . Therefore, to reduce the short-circuit impedance on the teaser side, it is necessary to reduce the leakage impedance between the U-side main-phase primary coil  121  and the W-side main-phase primary coil  122 . 
         [0007]    In the configuration described above, employing the structure of a coupling coil as the structure of the main-phase secondary coil  14 , as shown in  FIGS. 8 and 9 , allows reduction in the leakage impedance between the U-side main-phase primary coil  121  and the W-side main-phase primary coil  122 . A coupling coil refers to a structure having a function of improving magnetic coupling between a plurality of windings set apart from each other. 
         [0008]    The structure of the coupling coil is configured, for example, as follows: That is, the main-phase secondary coil  14  is divided at a middle portion into two coils, a U-side main-phase secondary coil  141  and a W-side main-phase secondary coil  142 . The U-side main-phase secondary coil  141  and the W-side main-phase secondary coil  142  are connected in parallel to each other. The U-side main-phase secondary coil  141  faces the U-side main-phase primary coil  121 , and the W-side main-phase secondary coil  142  faces the W-side main-phase primary coil  122 . 
         [0009]    In this configuration, the second single-phase load  92  is connected to the terminals  2   u  and  2   v  of the teaser secondary coil  15 , and the current i 1   t  having flowed through the teaser primary coil  13  splits into current flowing through the U-side main-phase primary coil  121  and current flowing through the W-side main-phase primary coil  122 , as shown in  FIG. 8 . As a result, mutual induction between the main-phase primary coil  12  and the main-phase secondary coil  14  induces electromotive force in the main-phase secondary coil  14 . Current i 2   t   1  therefore flows through the U-side main-phase secondary coil  141  so as to cancel the ampere-turns of the current lit′ flowing through the U-side main-phase primary coil  121 . Similarly, current i 2   t   2  flows through the W-side main-phase secondary coil  142  so as to cancel the ampere-turns of the current i 1   t   2  flowing through the W-side main-phase primary coil  122 . 
         [0010]    The current i 2   t   1  and the current i 2   t   2  circulate through the path formed of the U-side main-phase secondary coil  141  and the W-side main-phase secondary coil  142 . The circulating current i 2   t   1  and current i 2   t   2  cancel the ampere-turns of the current flowing through the U-side main-phase primary coil  121  and the current flowing through the W-side main-phase primary coil  122 , into which the current i 1   t  flowing through the teaser primary coil  13  splits. As a result, the magnetic coupling between the U-side main-phase primary coil  121  and the W-side main-phase primary coil  122  is improved, whereby the leakage impedance between the U-side main-phase primary coil  121  and the W-side main-phase primary coil  122  can be reduced. 
       CITATION LIST 
     Patent Literature 
       [0011]    Patent Literature 1: Japanese Patent Laid-Open No. 8-335520 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0012]    In the structure of the coupling coil of related art shown in  FIGS. 8 and 9 , however, the following problem exists: First, the main-phase secondary coil  14 , which is originally formed of a single coil, needs to be divided into a plurality of coils, for example, the two coils  141  and  142 , which then need to be connected in parallel to each other, resulting in increases in time and effort for formation of the two coils  141  and  142  and hence a decrease in productivity. Second, since the main-phase secondary coil  14  is formed of the divided U-side main-phase secondary coil  141  and W-side main-phase secondary coil  142 , the number of turns of conductor wires increases as compared with the case where the main-phase secondary coil  14  is formed of a single coil. The space factor of the main-phase secondary coil  14  with respect to the overall cross-sectional area of the transformer therefore decreases so that the size of the main-phase secondary coil  14  increases, resulting in an increase in the overall size and weight of the transformer. 
         [0013]    An object of the present invention is to provide a coupling coil structure that allows improvement in productivity and reduction in size and weight and a transformer using the coupling coil structure. 
       Solution to Problem 
       [0014]    A coupling coil structure according to an embodiment of the present invention includes a plurality of primary coils formed by winding a conductor wire and a plurality of secondary coils provided such that mutual induction occurs between the plurality of primary coils and the plurality of secondary coils. One of the plurality of primary coils intersects and is connected to another primary coil at a midway portion of the one primary coil, and one of the plurality of secondary coils that allows mutual induction to occur between the one primary coil and the one secondary coil forms a coupling coil formed of a single conductor having a width greater than or equal to an axial dimension of the one primary coil. 
         [0015]    A transformer according to the present embodiment includes the secondary coil that forms the coupling coil described above. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]      FIG. 1  shows the configuration of a Scott-connected transformer using a coupling coil structure according to an embodiment. 
           [0017]      FIG. 2  shows the configuration of a main-phase primary coil and a main-phase secondary coil in  FIG. 1  and therearound. 
           [0018]      FIG. 3  is a perspective view showing the configuration of the main-phase secondary coil in  FIG. 1 . 
           [0019]      FIG. 4  is a development of the main-phase secondary coil in  FIG. 3 . 
           [0020]      FIG. 5  shows the configuration of a Scott-connected transformer of related art. 
           [0021]      FIG. 6  shows a state in which a first single-phase load is connected to a main-phase secondary coil of the Scott-connected transformer in  FIG. 5 . 
           [0022]      FIG. 7  shows a state in which a second single-phase load is connected to a teaser secondary coil of the Scott-connected transformer in  FIG. 5 . 
           [0023]      FIG. 8  shows that a coupling coil structure of related art is employed in the Scott-connected transformer. 
           [0024]      FIG. 9  shows the configuration of the main-phase primary coil and the main-phase secondary coil in  FIG. 8  and therearound. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0025]    An embodiment will be described below with reference to the drawings. 
         [0026]      FIG. 1  shows the Scott-connected transformer  10  shown in  FIG. 5  to which a coupling coil structure according to the present embodiment is applied. A Scott-connected transformer  20  shown in  FIGS. 1 and 2  includes the iron core  11 , the main-phase primary coil  12 , the teaser primary coil  13 , and the teaser secondary coil  15 , as in the Scott-connected transformer  10  shown in  FIG. 5 . The Scott-connected transformer  20  shown in  FIGS. 1 and 2  further includes a main-phase secondary coil  30  which is a coupling coil in place of the main-phase secondary coil  14  shown in  FIG. 5 . The Scott-connected transformer  20  shown in  FIGS. 1 and 2  is the same as the Scott-connected transformer  10  shown in  FIG. 5  in terms of configuration except the main-phase secondary coil  30 . 
         [0027]    That is, the teaser primary coil  13  and the teaser secondary coil  15  are each formed by winding a conductor wire around the iron core  11  and are configured concentrically with each other. The Scott-connected transformer  20  is configured such that the main-phase primary coil  12 , which is one of the plurality of primary coils  12  and  13 , intersects the teaser primary coil  13 , which is the other primary coil, in a T-like shape in such a way that the teaser primary coil  13  is connected to the main-phase primary coil  12  at a midway portion of the main-phase primary coil  12 , that is, a middle point N between a U-side main-phase primary coil  121  and a W-side main-phase primary coil  122 . Each of the U-side main-phase primary coil  121  and the W-side main-phase primary coil  122  is formed by winding a conductor wire around the iron core  11 . The U-side main-phase primary coil  121  and the W-side main-phase primary coil  122  are arranged side by side along the axial direction of the coils. 
         [0028]    The main-phase secondary coil  30  is provided so as to face the main-phase primary coil  12 . Mutual induction occurs between the main-phase secondary coil  30  and the main-phase primary coil  12 . The main-phase secondary coil  30  arranged concentrically with the main-phase primary coil  12 , which is formed of the U-side main-phase primary coil  121  and the W-side main-phase primary coil  122 . The main-phase secondary coil  30  is formed by winding a single sheet-shaped conductor having conductivity, for example, a single thin plate  31  made of a metal, such as aluminum or copper, around the iron core  11 , as also shown in  FIGS. 3 and 4 . 
         [0029]    The axial dimension H of the main-phase secondary coil  30 , that is, the width of the main-phase secondary coil  30  is set to be greater than or equal to the axial dimension L of the main-phase primary coil  12 , that is, the sum of the axial dimension L 1  of the U-side main-phase primary coil  121  and the axial dimension L 2  of the W-side main-phase primary coil  122 , as shown in  FIG. 2 . In the present embodiment, the width H of the main-phase secondary coil  30  is roughly equal to the axial dimension L of the main-phase primary coil  12 . The main-phase secondary coil  30  has lead wires  32  and  33  located at the opposite ends thereof, as shown in  FIGS. 3 and 4 . Each of the lead wires  32  and  33  is, for example, a rod made of a metal, such as aluminum or copper. The lead wires  32  and  33  are welded or otherwise connected to the thin plate  31 . End portions of the lead wires  32  and  33  function as the terminals  1   u  and  1   v , to which the first single-phase load  91  is connected. 
         [0030]    A description will next be made of current flowing through the Scott-connected transformer  20  in a state in which only the second single-phase load  92  is connected to the terminals  2   u  and  2   v  of the teaser secondary coil  15  but the first single-phase load  91  is not connected to the terminals  1   u  and  1   v  of the main-phase secondary coil  30 , as shown in  FIG. 1 . In this case, the current lit having flowed through the teaser primary coil  13  splits into the current i 1   t   1  flowing through the U-side main-phase primary coil  121  and the current i 1   t   2  flowing through the W-side main-phase primary coil  122 . As a result, the current i 2   t   1 , which flows so as to cancel the ampere-turns of the current i 1   t   1  flowing through the U-side main-phase primary coil  121 , flows through a portion of the main-phase secondary coil  30 , that is, a portion thereof facing the U-side main-phase primary coil  121 , as shown in  FIG. 2 . Similarly, the current i 2   t   2 , which flows so as to cancel the ampere-turns of the current i 1   t   2  flowing through the W-side main-phase primary coil  122 , flows through a portion of the main-phase secondary coil  30 , that is, a portion thereof facing the W-side main-phase primary coil  122 . 
         [0031]    The current i 2   t   1  and the current i 2   t   2  flowing through the main-phase secondary coil  30  circulate in the main-phase secondary coil  30  to cancel the ampere-turns of the current i 1   t   1  flowing through the U-side main-phase primary coil  121  and the current i 1   t   2  flowing through the W-side main-phase primary coil  122 , as shown in  FIG. 4 . Therefore, in the main-phase primary coil  12 , the magnetic coupling between the U-side main-phase primary coil  121  and the W-side main-phase primary coil  122  can be improved, whereby the leakage impedance between the main-phase primary coils  121  and  122  can be reduced. 
         [0032]    According to the configuration, the main-phase secondary coil  30  is formed by winding the single thin plate  31  around the iron core  11 . The main-phase secondary coil  30  therefore does not need to be divided into a plurality of coils or connected in parallel to each other in order to form a coupling coil, unlike the main-phase secondary coils  141  and  142  having the configuration of related art. The coupling coil can therefore be configured with no increase in time or effort, whereby a decrease in productivity is avoided. 
         [0033]    Further, since the main-phase secondary coil  30  is formed of a sheet-shaped thin plate  31 , it is unnecessary to wind a large number of conductor wires. The main-phase secondary coil  30  according to the present embodiment can therefore provide a higher proportion of the conductor with respect to the cross section of the coil than in a case where a large number of conductor wires are wound. That is, according to the present embodiment, a decrease in the space factor of the conductor with respect to the overall cross-sectional area of the main-phase secondary coil  30  can be avoided even when the structure of a coupling coil is employed, whereby an increase in the size of the main-phase secondary coil  30  can be avoided. 
         [0034]    Further, in the present embodiment, the width H of the main-phase secondary coil  30  is set to be roughly equal to the axial dimension L of the main-phase primary coil  12 . Since the main-phase secondary coil  30  is thus allowed to face the entire main-phase primary coil  12 , the current i 2   t   1  and i 2   t   2  circulating in the main-phase secondary coil  30  can cancel the ampere-turns of the current i 1   t   1  flowing through the U-side main-phase primary coil  121  and the current i 1   t   2  flowing through the W-side main-phase primary coil  122 . As a result, the magnetic coupling between the U-side main-phase primary coil  121  and the W-side main-phase primary coil  122  can be further improved, whereby the leakage impedance between the main-phase primary coils  121  and  122  can be more efficiently reduced. 
         [0035]    The main-phase secondary coil  30  has the lead wires  32  and  33  located at the opposite ends thereof, which serve as a winding start and a winding end of the thin plate  31 , which serves as a conductor. The lead wires  32  and  33  allow the terminals  1   u  and  1   v  to be readily provided even when the thin plate  31  is used as the conductor of the main-phase secondary coil  30 . 
         [0036]    The main-phase secondary coil  30  may be configured such that a large number of conductor wires are woven in a cloth-like shape to form a single conductor as a whole. 
         [0037]    The coupling coil structure according to the embodiment described above is not necessarily applied to a Scott-connected transformer and is generally applicable to a coupling winding structure for improving the magnetic coupling between a plurality of coils set apart from each other and a transformer using the coupling winding structure. 
         [0038]    As described above, the coupling coil structure according to the embodiment includes a plurality of primary coils formed by winding a conductor wire and a plurality of secondary coils provided such that mutual induction occurs between the plurality of primary coils and the plurality of secondary coils, and one of the plurality of primary coils intersects and is connected to another primary coil at a midway portion of the one primary coil, and one of the plurality of secondary coils that allows mutual induction to occur between the one primary coil and the one secondary coil forms a coupling coil formed of a single conductor having a width greater than or equal to the axial dimension of the one primary coil. 
         [0039]    As a result, the secondary coil corresponding to the one primary coil forms a coupling coil formed of the single conductor having a width greater than or equal to the axial dimension of the one primary coil. The secondary coil corresponding to the one primary coil therefore does not need to be divided into a plurality of coils or connected in parallel to each other in order to form a coupling coil. The coupling coil can therefore be configured with no increase in time or effort, whereby a decrease in productivity is avoided. Further, since the secondary coil configured as a coupling coil is formed of a single conductor, it is unnecessary to wind a large number of conductor wires to form the secondary coil, whereby the space factor of the conductor is reduced and an increase in the size of the secondary coil is therefore avoided. 
         [0040]    An embodiment of the present invention has been described. The embodiment is presented by example and is not intended to limit the scope of the invention. The novel embodiment can be implemented in a variety of other forms, and a variety of types of omission, replacement, and change can be made to the embodiment to the extent that the changes do not depart from the substance of the invention. The embodiment and the changes fall within not only the scope and substance of the invention but also the invention set forth in the claims and equivalents thereto.