Abstract:
In a rotating machinery having armature windings constituted by a lot of strands, when the armature winding is constituted by four layers, a step number of the strands becomes half with respect to two layers of armature windings so as to facilitate manufacturing an armature winding of 540 degree transposition in which a transposition pitch is elongated and a circulating current loss is reduced, but since an output voltage becomes twice, for securing a voltage limit value caused by an isolation resisting force, one layer of armature windings are constituted by sub windings separated into at least two layers in a vertical direction, a transposition is independently applied to each of the sub windings, the sub windings are connected to the armature windings of the other slot while keeping an isolation of the sub winding at an armature winding end region by at least two connecting methods, and the sub winding constructs a parallel circuit by the armature windings of a plurality of slots.

Description:
FIELD OF THE INVENTION 
   The present invention relates to an armature winding of a rotating machinery. 
   DESCRIPTION OF RELATED ART 
   In a rotating machinery, a lot of slots extending in an axial direction are provided in an inner circumferential portion of a stator core, and an armature winding is accommodated within the slots. In the case that an alternating current flows through the armature winding, an alternating current loss is generated in the armature winding by a magnetic flux forming a linkage with the armature winding within the slot and in an end region of the winding. The alternating current loss causes a temperature rise of the armature winding and an efficiency reduction of the rotating machinery, and it is a purpose for reducing the alternating current loss so as to improve a reliability of the rotating machinery and to improve the efficiency. With respect to the purpose, the alternating current loss is reduced by constructing the armature winding by a plurality of insulated strands and twisting the strands of the armature winding in an axial direction of the rotating machinery so as to apply a transposition (for example, see “Herstellung der Wicklungen electrischer Maschinen” by H. Sequentz, Japanese Translation, Published. 1990 Jan. 1, Kaihatsusha). The alternating current loss can be divided into an eddy current loss generated by the magnetic flux forming the linkage with the strand itself, and a circulating current loss circulating the strand by the magnetic flux forming the linkage between the strands. 
   The reduction of the eddy current loss can be achieved by making a thickness of the strand thin and increasing a stage number of the strands constituting the armature winding. 
   The circulating current loss depends on an angle transposing the strand. An angle of transposition of the strand is called as a 360 degree transposition in the case that the strand is twisted at one rotation between both ends of the slot, and is called as a 540 degree transposition in the case that the strand is twisted at one and half rotation between both the ends of the slot. In the 360 degree transposition, since a linkage flux of the winding end portion of the armature is applied in both end portions, a circulating current is generated more than a little. In the 540 degree transposition, since the linkage flux formed by its own armature winding remains, the circulating current flows, however, since the linkage fluxes formed by the other armature windings are canceled, the circulating current becomes smaller in comparison with the 360 degree transposition. As mentioned above, in order to reduce the circulating current loss, it is effective to employ the 540 degree transposition. However, the 540 degree transposition has a portion in which a pitch of transposition is shorter in comparison with the 360 degree transposition. 
   Two layers of armature windings are provided in one slot, and the armature winding in an inner diameter side and the armature winding in an outer diameter side are electrically connected at the end region of the armature winding by a connector so as to be connected to the armature winding in the other slot. 
   In the rotating machinery having the structure mentioned above, in order to reduce the eddy current loss, it is effective to make the thickness of the strand thin and increase the stage number of the strands constituting the armature winding, however, since the pitch of the transposition becomes shorter on the basis of the increase of the stage number of the strand, it is not easy to manufacture the armature winding of the 540 degree transposition, and the circulating current loss is increased in the 360 degree transposition having the longer pitch of the transposition. As mentioned above, the eddy current loss and the circulating current loss are in a trade-off relation, and there exists a problem that it is hard to simultaneously reduce both of the eddy current loss and the circulating current loss. 
   With respect to the problem, there is a structure in which four layers of armature windings are formed in a vertical direction within one slot (for example, see JP-A-2001-69707, page 13, and  FIG. 4 , and JP-A-2002-199633, page 7,  FIG. 2 ). Accordingly, since the stage number of the strand becomes half in comparison with the armature winding constituted by two layers, the pitch of transposition becomes twice, and it is possible to apply the armature winding of 540 degree transposition. 
   In the rotating machinery having the structure mentioned above, since the four layers of armature windings are connected in series, the winding number becomes twice in comparison with the structure constituted by two layers, and a voltage is output twice. Further, since a cross section area of one winding becomes half, a current density is identical between the two-layers structure and the four-layers structure although a current value is half. 
   In the armature winding, a maximum voltage is limited by a dielectric strength of an insulator, and a maximum current density is limited by a temperature of the winding. In this case, if the voltage and the current density are designed by limit values in the structure in which the armature winding is constituted by two layers, the current density is the limit value but the voltage becomes twice the limit value in the four-layers structure, so that there is a problem that the four-layers structure is not established. 
   BRIEF SUMMARY OF THE INVENTION 
   In order to solve the problem mentioned above, in accordance with the present invention, it is characterized in that one layer of armature machinery is constituted by at least two layers of sub windings in a vertical direction, and these sub windings are structured by a parallel circuit. 
   In the present invention, since two layers or more of sub windings constitute the parallel circuit, it is possible to secure the same limit value of the voltage value as that of the one-layer armature winding. Further, since the stage number of the sub windings becomes equal to or less than a half of the one-layer armature winding, the 540 degree transposition can be applied even if the thickness of the strand is made thin so as to increase the stage number, whereby it is possible to reduce both of the eddy current loss and the circulating current loss. Further, since a height of the sub winding in a radial direction becomes equal to or less than half, the magnetic flux forming the linkage with the sub winding becomes small, and the circulating current loss can be further reduced. 
   Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is a perspective view of an armature winding end portion showing a first embodiment in accordance with the present invention; 
       FIG. 2  is a perspective view of the armature winding end portion showing the first embodiment in accordance with the present invention; 
       FIGS. 3A-3C  illustrate an example of a wire connection view in the case of being constructed by the sub windings existing in a plurality of slots in accordance with the present invention. 
       FIG. 4  is a loss distribution view of a strand in accordance with a conventional example; 
       FIG. 5  is a loss distribution view of a strand in accordance with the first embodiment of the present invention; 
       FIG. 6  is a comparative view of a loss between the conventional example and the present invention; 
       FIG. 7  is a cross sectional view showing a structure of an armature winding in an inner portion of a slot in accordance with the present invention; 
       FIG. 8  is a perspective view of an armature winding end portion showing a conventional example; 
       FIG. 9  is a perspective view of an armature winding end portion showing a second embodiment in accordance with the present invention; 
       FIG. 10  is a perspective view of an armature winding end portion showing the second embodiment in accordance with the present invention; 
       FIG. 11  is a perspective view of an armature winding end portion showing a third embodiment in accordance with the present invention; 
       FIG. 12  is a perspective view of an armature winding end portion showing the third embodiment in accordance with the present invention; 
       FIG. 13  is a perspective view of an armature winding end portion showing a fourth embodiment in accordance with the present invention; 
       FIG. 14  is a perspective view of an armature winding end portion showing the fourth embodiment in accordance with the present invention; 
       FIG. 15  is a perspective view of an armature winding end portion showing a fifth embodiment in accordance with the present invention; 
       FIG. 16  is a perspective view of an armature winding end portion showing a sixth embodiment in accordance with the present invention; 
       FIG. 17  illustrates a rotating machinery in accordance with the invention; and 
       FIG. 18  illustrates a transposition angle of a strand. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A description will be in detail given below of a rotating machinery in accordance with the present invention on the basis of illustrated embodiments. 
     FIG. 8  shows a perspective view of a conventional armature winding end portion. A lot of armature winding end portions exist in a rotating machinery, and  FIG. 8  shows one of them. The armature winding is constituted by an armature winding  1  on an inner diameter side  10  and an armature winding  2  on an outer diameter side  11 , and the armature winding  1  and the armature winding  2  are constituted by a plurality of strands  3 . Each of the strands  3  is electrically short circuited by brazing or the like in the armature winding end portion, and the armature winding  1  and the armature winding  2  are electrically connected by a connector  18  in accordance with the brazing or the like. 
   Embodiment 1 
     FIGS. 1 ,  2  and  3  show a first embodiment in accordance with the present invention. 
   The armature winding is constituted by the armature winding  1  on the inner diameter side  10  and the armature winding  2  on the outer diameter side  11 , and the armature winding  1  and the armature winding  2  in accordance with the present embodiment are structured such that the strands are arranged in two rows. The armature winding  1  is separated into two layers so as to comprise a sub winding  4   a  and a sub winding  4   b  in a vertical direction. Further, the armature winding  2  is also separated into two layers so as to comprise a sub winding  5   a  and a sub winding  5   b  in a vertical direction. It is desirable that stage numbers of the strands of the sub winding  4   a  and the sub winding  4   b  are equal to each other, however, the stage numbers of the strands may be different. In the same manner, it is desirable that stage numbers of the strands of the sub winding  5   a  and the sub winding  5   b  are equal to each other, however, the stage numbers of the strands may be different. The sub winding  4   a  and the sub winding  4   b  are electrically isolated via a spacer (not shown). Further, the sub winding  5   a  and the sub winding  5   b  are also electrically isolated via a spacer (not shown). Further, the sub winding  4   a , the sub winding  4   b , the sub winding  5   a  and the sub winding  5   b  independently transpose the strands, respectively. An angle of transposition is set to be equal to or more than 360 degrees, however, it is preferably effective for reducing a loss that the sub winding is set to 540 degree transposition, as shown in  FIG. 18 . Further, each of the sub winding  4   a  and the sub winding  4   b , and the sub winding  5   a  and the sub winding  5   b  applies a current as a parallel circuit. 
   In the armature winding end portion, if the armature winding  1  and the armature winding  2  are connected by the conventional connector, the sub winding  4   a  and the sub winding  4   b  are electrically short circuited. In the connection mentioned above, since the transposition is not formed between the sub winding  4   a  and the sub winding  4   b , a great circulating current flows between the sub winding  4   a  and the sub winding  4   b , and a circulating current loss is increased. In the same manner, a great circulating current loss is generated in the sub winding  5   a  and the sub winding  5   b.    
   In the present invention, there is employed a system of connecting while keeping the electrical isolation between the sub winding  4   a  and the sub winding  4   b  and between the sub winding  5   a  and the sub winding  5   b , for connecting the armature winding  1  and the armature winding  2 . 
   In  FIG. 1 , the sub winding  4   a  of the armature winding  1  on the inner diameter side  10  is connected to the sub winding  5   a  of the armature winding  2  on the inner diameter side  10  by a connector  6   a . The connector  6   a  is set to a stepped structure so as to prevent the sub winding  4   a  and the sub winding  4   b  from being short circuited. In order to further secure the isolation, a spacer (not shown) may be provided between the connector  6   a  and the sub winding  4   b . Further, the sub winding  4   b  of the armature winding  1  on the outer diameter side  11  is connected to the sub winding  5   b  of the armature winding  2  on the outer diameter side  11  by a connector  6   b . The connector  6   b  is also set to the stepped structure so as to prevent the sub winding  5   a  and the sub winding  5   b  from being short circuited. In order to further secure the isolation, a spacer (not shown) may be provided between the connector  6   b  and the sub winding  5   a . A linkage flux (not shown) between the sub winding  4   a  and the sub winding  4   b  and a linkage flux (not shown) between the sub winding  5   a  and the sub winding  5   b  have the same direction, and the connection in  FIG. 1  is called as a positive connection. 
   In  FIG. 2 , the sub winding  4   a  of the armature winding  1  on the inner diameter side  10  is connected to the sub winding  5   b  of the armature winding  1  on the outer diameter side  11  via a connector  6   c . The connector  6   c  is set to a stepped structure so as to prevent the sub winding  4   a  and the sub winding  4   b , and the sub winding  5   a  and the sub winding  5   b  from being short circuited. In order to further secure the isolation, a spacer (not shown) may be provided between the connector  6   c  and the sub winding  4   b , and between the connector  6   c  and the sub winding  5   a . Further, the sub winding  4   b  of the armature winding  1  on the outer diameter side  11  is connected to the sub winding  5   a  of the armature winding  2  on the inner diameter side  10  by a connector  6   d . The connector  6   d  may not be set to the stepped structure. A linkage flux (not shown) between the sub winding  4   a  and the sub winding  4   b  and a linkage flux (not shown) between the sub winding  5   a  and the sub winding  5   b  have the inverse direction, and the connection in  FIG. 2  is called as a negative connection. 
   The magnetic flux (not shown) forming the linkage between the sub windings of the armature winding  1  is different from that of the armature winding  2 . Further, the magnetic flux forming the linkage between the sub windings of the armature windings  2  has almost the same value in all the slots, however, the linkage flux in an in-phase slot (not shown) is different from that in an out-of-phase slot (not shown) in the armature winding  1 . Then, it is possible to reduce the circulating current between the sub windings by constructing the sub windings existing in a plurality of slots by a parallel circuit, and combining the positive connection in  FIG. 1  and the negative connection in  FIG. 2  so as to cancel the linkage flux between the sub windings. 
     FIGS. 3A and 3B  illustrate an example of a wire connection view in the case of being constructed by the sub windings existing in a plurality of slots. On a circumferential direction  24  side in  FIG. 3A , the armature winding  1  on the inner diameter side is indicated by a solid line, and on a circumferential direction  25  side, the armature winding  2  in the outer diameter side is indicated by the broken line. Armature winding  1  and armature winding  2  each form a circuit, with circuit  1  being parallel to circuit  2 . Each of the sub windings  4   a ,  4   b  of the armature core  1  has seven sub windings, respectively that is,  4   a   1  to  4   a    7 ,  4   b    1  to  4   b   7 , and each of the sub windings  5   a ,  5   b  of the armature core  2  has seven sub windings, respectively, that is  5   a   1  to  5   a   7 ,  5   b   1  to  5   b   7 . Each of the sub winding  4   a , the sub winding  4   b , the sub winding  5   a  and the sub winding  5   b  are respectively connected at the armature winding end portions by using the positive connection  7   a  and the negative connection  7   b . A combination between the positive connection  7   a  and the negative connection  7   b  may be determined in such manner that a total value of the linkage fluxes  8   a   1  to  8   a   7  and  8   b   1  to  8   b   7  between the sub windings becomes small. As a concrete connecting example, as shown in  FIG. 3B , the first connected portion  1  of the first parallel circuit is made up of  4   a   1 ,  5   b   1 ,  4   a   2 ,  5   b   2 ,  4   a   3 ,  5   b   3 ,  4   a   4 ,  5   b   4 ,  4   a   5 ,  5   b   5 ,  4   a   6 ,  5   b   6 ,  4   b   7 , and  5   b   7 , and the second connected portion  2  of the second parallel circuit is made up of  4   b   1 ,  5   a   1 ,  4   b   2 ,  5   a   2 ,  4   b   3 ,  5   a   3 ,  4   a   4 ,  5   a   4 ,  4   b   5 ,  5   a   5 ,  4   b   6 ,  5   a   6 ,  4   a   7 , and  5   a   7 . Further, an endmost portion  9   a  of the armature winding  1  electrically connects the sub winding  4   a   1  and the sub winding  4   b   1 , and the sub winding  5   a   1  and the sub winding  5   b   1  are electrically connected by an endmost portion  9   b  of the armature winding  2 , whereby the sub windings form the parallel circuit between the endmost portion  9   a  and the endmost portion  9   b . A combination between the positive connection  7   a  and the negative connection  7   b  may be determined in such a manner that a total value of the linkage fluxes  8   a  and  8   b  between the sub windings constructing the parallel circuit existing between the endmost portions  9   a  and  9   b  becomes small. 
   A way of selecting a plurality of slots constructing one parallel circuit is optional, however, if the slots are selected from an in phase neutral point side to a line side, the circulating current between the sub windings is in common in all the armature windings from the neutral point side to the line side, and an advantage is obtained in the respect that the loss is easily balanced. 
     FIG. 4  shows a data of a loss obtained by summing up the direct load loss and the circulating current loss of the conventional armature winding. An abscissa axis corresponds to a position of each of the strands, and shows a loss distribution with respect to the positions of the strands. The loss is small in a center portion in the radial direction of the strand, however, the losses on the inner diameter side and the outer diameter side become greater due to an influence of the circulating current. 
     FIG. 5  shows a data of the loss of the present invention in the structures shown in  FIGS. 1 ,  2  and  3 . It is understood that a height of the armature winding becomes half, whereby the linkage flux becomes small and the circulating current loss is reduced. 
     FIG. 6  shows a data of a loss total value of a direct load loss, a circulating current loss and an eddy current loss of the armature winding. If the conventional loss is set to 100%, the loss becomes 78% in the present invention, and 22% loss reduction effect can be obtained. In  FIG. 6 , a thickness of the strand is set identical between the conventional structure and the present invention, however, since the present invention can make the thickness of the strand thin, the eddy current loss can be reduced by thinning the strand, and it is possible to expect a further loss reduction. 
     FIG. 7  is a cross sectional view showing a structure of the armature winding in an inner portion of a slot  14  provided in a tooth  15 . The sub winding  4   a  and the sub winding  4   b  are electrically isolated via a spacer  12   a . Since the sub winding  4   a  and the sub winding  4   b  form the parallel circuit and have a small potential difference, the spacer  12   a  does not require such an isolating resistance as a wall insulation  13   a . Further, the sub winding  4   a , the sub winding  4   b  and the spacer  12   a  are applied an insulation to the earth by the wall insulation  13   a  so as to construct the armature winding  1 . In the same manner, the sub winding  5   a  and the sub winding  5   b  are electrically isolated via the spacer  12   b , and the sub winding  5   a , the sub winding  5   b  and the spacer  12   b  are applied an insulation to the earth by a wall isolation  13   b  so as to construct the armature winding  2 . The armature winding  1  and the armature winding  2  are accommodated in a slot  14  together with spacers  16   a ,  16   b  and  16   c , and are structured such as to be fixed by a wedge  17 . 
   In  FIG. 7 , two layers of armature windings are accommodated in one slot, however, the present invention can be applied to a rotating machinery in which one layer of armature winding is accommodated in one slot, and a rotating machinery in which two or more layers of armature windings are accommodated in one slot. 
     FIG. 17  illustrates a rotating machinery  100 , which includes a rotor shaft  50 , a rotor body  51 , and a stator core  30  inside of a stator frame  60 . The stator core  30  has a plurality of slots extending in an axial direction in an inner circumferential portion. The rotating machinery further includes armature winding  1  and armature winding  2 , each winding having a plurality of strands  3  within a slot  14 . The rotating machinery further includes a clamping plate  31 . 
   Embodiment 2 
     FIGS. 9 and 10  are perspective views of an armature winding end portion showing a second embodiment in accordance with the present invention. 
   The embodiment in  FIGS. 9 and 10  is different in a shape of the connector from the embodiment in  FIGS. 1 and 2 . The embodiment in  FIGS. 1 and 2  is formed in the stepped structure in such a manner as to prevent the connector from being brought into contact with the other sub windings to which the connector is not connected. 
   The embodiment in  FIG. 9  shows a second embodiment of the positive connection, and is structured such that a connector  19   a  is formed in a flat plate shape, a connection spacer  20   a  is provided between the connector  19   a  and the sub winding  4   a , a connection spacer  20   a  is also provided between the connector  19   a  and the sub winding  5   a , and the connector  19   a , the connection spacer  20   a  and the sub winding  4   a , and the connector  19   a , the connection spacer  20   a  and the sub winding  5   a  are respectively electrically connected by brazing or the like. With the structure mentioned above, the sub winding  4   a  and the sub winding  4   b  keep an electrical isolation. In order to more securely isolate, a spacer (not shown) may be provided between the connector  19   a  and the sub winding  4   b . In the same manner, a connection spacer  20   b  is provided between the connector  19   b  and the sub winding  4   b  and between the connector  19   b  and the sub winding  5   b , respectively, and these elements are respectively electrically connected by brazing or the like. In order to more securely isolate, a spacer (not shown) may be provided between the connector  19   b  and the sub winding  5   a.    
   The embodiment in  FIG. 10  shows a second embodiment of the negative connection, and is structured such that a connector  19   c  is formed in a flat plate shape, a connection spacer  20   c  is respectively provided between the connector  19   c  and the sub winding  4   a  and between the connector  19   c  and the sub winding  5   b , and the connector  19   c , the connection spacer  20   c , the sub winding  4   a  and the sub winding  5   b  are respectively electrically connected by brazing or the like. With the structure mentioned above, the sub winding  4   a  and the sub winding  4   b , and the sub winding  5   a  and the sub winding  5   b  respectively keep an electrical isolation. In order to more securely isolate, a spacer (not shown) may be provided between the connector  19   c  and the sub winding  4   b  and between the connector  19   c  and the sub winding  5   a , respectively. Further, the sub winding  4   b  and the sub winding  5   a  are connected by a connector  19   d . A connection spacer is not necessary for the connector  19   d.    
   The same effects as those of  FIGS. 1 and 2  can be expected in this embodiment. 
   Embodiment 3 
     FIGS. 11 and 12  are perspective views of an armature winding end portion showing a third embodiment in accordance with the present invention. 
   The embodiment in  FIGS. 11 and 12  is different in a shape of the connector and a shape of the sub winding from the embodiment in  FIGS. 1 and 2 . The embodiment shown in  FIGS. 1 and 2  is formed as the stepped structure in such a manner as to prevent the connector from being brought into contact with the other sub windings to which the connector is not connected. 
   The embodiment in  FIG. 11  shows a third embodiment of the positive connection, and is structured such that a connector  21   a  is formed in a flat plate shape, and the sub winding  4   a  and the sub winding  5   a  are circumferentially bent in a direction of the connector  21   a  so as to be electrically connected to the connector  21   a  by brazing or the like. With the structure mentioned above, the sub winding  4   a  and the sub winding  4   b  keep an electrical isolation. In order to more securely isolate, a spacer (not shown) may be provided between the connector  21   a  and the sub winding  4   b . In the same manner, the sub winding  4   b  and the sub winding  5   b  are circumferentially bent in a direction of a connector  21   b  so as to be electrically connected to the connector  21   b  by brazing or the like. In order to more securely isolate, a spacer (not shown) may be provided between the connector  21   b  and the sub winding  5   a.    
   In the embodiment in  FIG. 11 , the sub winding  4   a  and the sub winding  5   a  are bent in the direction of the connector  21   a , and the sub winding  4   b  and the sub winding  5   b  are bent in the direction of the connector  21   b , however, the same effect can be obtained by bending any one of the sub winding  4   a  and the sub winding  5   a  or the sub winding  4   b  and the sub winding  5   b.    
   The embodiment in  FIG. 12  shows a third embodiment of the negative connection, and is structured such that a connector  21   c  is formed in a flat plate shape, and the sub winding  4   a  and the sub winding  5   b  are circumferentially bent in a direction of the connector  21   c  so as to be electrically connected to the connection piece  21   c  by brazing or the like. With the structure mentioned above, the sub winding  4   a  and the sub winding  4   b , and the sub winding  5   a  and the sub winding  5   b  keep an electrical isolation. In order to more securely isolate, a spacer (not shown) may be provided between the connector  21   c  and the sub winding  4   b  and between the connector  21   c  and the sub winding  5   a . Further, the sub winding  4   b  and the sub winding  5   a  are electrically connected by a connector  21   d  in accordance with brazing or the like. 
   In the embodiment shown in  FIG. 12 , the sub winding  4   a  and the sub winding  5   b  are circumferentially bent in the direction of the connector  21   c , however, the same effects can be obtained by circumferentially bending the sub winding  4   b  and the sub winding  5   a  in the direction of the connector  21   d.    
   The same effects as those of  FIGS. 1 and 2  can be expected in this embodiment. 
   Embodiment 4 
     FIGS. 13 and 14  are perspective views of an armature winding end portion showing a fourth embodiment in accordance with the present invention. 
   The embodiment in  FIGS. 13 and 14  is different in a layout of the connector from the embodiment in  FIGS. 1 and 2 . In the embodiment shown in  FIGS. 1 and 2 , the connector is provided in both sides. 
   The embodiment in  FIG. 13  shows a fourth embodiment of the positive connection, and is structured such that a connector  22   a  and a connector  22   b  are shifted back and forth in an axial direction, and the connectors are arranged on one side. The connector  22   b  is formed as a stepped structure, however, may be structured such that a connection spacer is provided as shown in  FIG. 9 , or a sub winding is bent as shown in  FIG. 11 . The back and forth positions of the connector  22   a  and the connector  22   b  may be set opposite to that of  FIG. 13 . In this case, the connector  22   a  is structured such that the isolation between the sub winding  4   a  and the sub winding  4   b  can be kept, for example, the stepped structure or the like. Further, in  FIG. 13 , the sub winding  4   b  and the sub winding  5   b  are set short in correspondence to the position of the connector  22   b , however, may keep the same length as the sub winding  4   a  and the sub winding  5   a.    
   The embodiment in  FIG. 14  shows a fourth embodiment of the negative connection, and is structured such that a connector  22   c  and a connector  22   d  are shifted back and forth in the axial direction, and the connectors are arranged on one side. The connector  22   c  is formed as a stepped structure, however, may be structured such that a connection spacer is provided as shown in  FIG. 10 , or a sub winding is bent as shown in  FIG. 12 . The back and forth positions of the connector  22   c  and the connector  22   d  may be set opposite to that of  FIG. 14 . Further, in  FIG. 14 , the sub winding  4   a  and the sub winding  5   b  are set short in correspondence to the position of the connector  22   c , however, may keep the same length as the sub winding  4   b  and the sub winding  5   a.    
   The same effects as those of  FIGS. 1 and 2  can be expected in this embodiment. 
   Embodiment 5 
     FIG. 15  is a perspective view of an armature winding end portion showing a fifth embodiment in accordance with the present invention. The embodiment shown in  FIG. 15  is different in a separating number of the armature winding from the embodiment shown in  FIG. 1 . In the embodiment shown in  FIG. 1 , the armature winding is separated into two sections in the vertical direction, and is constituted by two layers of sub windings. 
   The embodiment in  FIG. 15  shows a fifth embodiment of the positive connection, and is structured such that the armature winding is separated into three sections in the vertical direction, and is constituted by three layers of sub windings. The armature winding  1  is constituted by a sub winding  4   a , a sub winding  4   b  and a sub winding  4   c , and the armature winding  2  is constituted by a sub winding  5   a , a sub winding  5   b  and a sub winding  5   c . The sub winding  4   a  and the sub winding  5   a  are electrically connected by a connector  23   a , the sub winding  4   b  and the sub winding  5   b  are electrically connected by a connector  23   b , and the sub winding  4   c  and the sub winding  5   c  are electrically connected by a connector  23   c , respectively. In the structure of the two-layers sub winding, the connecting method is constituted by two kinds comprising the positive connection in  FIG. 1  and the negative connection in  FIG. 2 , however, the structure of the three-layers sub winding in  FIG. 15  has six kinds of connection methods (not shown). Since a combination of the connecting method is increased, it is possible to more cancel the linkage flux (not shown) between the sub windings in comparison with the case of the two-layers sub winding, and the loss reduction can be further expected. 
   The connector  23   a , the connector  23   b  and the connector  23   c  are formed as the stepped structures in the same manner as those of  FIG. 1 , however, the structure may be made such that the connection spacer is provided as shown in  FIG. 9 , or the sub winding is bent as shown in  FIG. 11 . 
   The present embodiment is constituted by the three-layers sub winding, however, may be constituted by four or more layers of sub windings, or the separating number of the sub winding in the armature winding  1  may be different from that in the armature winding  2 . 
   Embodiment 6 
     FIG. 16  is a perspective view of an armature winding end portion showing a sixth embodiment in accordance with the present invention. The embodiment shown in  FIG. 16  is different in a row number of the strands of the armature winding from the embodiment shown in  FIG. 1 . In the embodiment shown in  FIG. 1 , the armature winding is constituted by two rows of strands. 
   The embodiment in  FIG. 16  shows a sixth embodiment of the positive connection, and is structured such that the armature windings  1  and  2  are constituted by four rows of strands. In a large capacity of rotating machinery, there is a structure in which some of the strands are constituted by a hollow strand (not shown), and a cooling medium is passed therethrough. In  FIG. 16 , the armature winding  1  is constituted by a sub winding  4   a , a sub winding  4   a ′, a sub winding  4   b  and a sub winding  4   b ′, and the armature winding  2  is constituted by a sub winding  5   a , a sub winding  5   a ′, a sub winding  5   b  and a sub winding  5   b ′. The sub windings  4   a  and  4   a ′ and the sub windings  5   a  and  5   a ′ are electrically connected by a connector  26   a , and the sub windings  4   b  and  4   b ′ and the sub windings  5   b  and  5   b ′ are electrically connected by a connector  26   b . A negative connection (not shown) can be achieved by electrically connecting the sub windings  4   b  and  4   b ′ and the sub windings  5   a  and  5   a ′ by the connector, and electrically connecting the sub windings  4   a  and  4   a ′ and the sub windings  5   b  and  5   b ′ by the connector. 
   The connector  26   a  and the connector  26   b  are respectively formed as the stepped structure in the same manner as  FIG. 1 , however, may be structured such that the connection spacer is provided as shown in  FIG. 9 , or the sub winding is bent as shown in  FIG. 11 . 
   The present embodiment is structured by the armature winding constituted by four rows of strands, however, the same effects can be obtained by the armature winding constituted by six or more rows of strands. 
   It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.