A method for transposing strands of a stator bar of a turbogenerator

Abstract

A method for transposing strands of a stator bar of a turbogenerator, which relates to the field of turbogenerators. The present invention is to solve the problems of excessive circulating current loss and serious temperature rise caused by uneven distribution of the spatial positions of the transposed strands in the existing stator winding. In the method for transposing strands of a stator bar of a turbogenerator according to the present invention, each strand can be evenly distributed in the entire space of the slot portion, thereby reducing the circulating current loss between the transposed strands caused by the uneven distribution of the leakage magnetic field in the slot, effectively reducing the additional loss and the temperature rise degree of the stator bar, as well as the circulating current between the strands, and improving the working efficiency of the generator.

Description

Technical Field

[0001] The present invention belongs to the field of turbogenerators, and particularly relates to a transposition structure of stator bars of a turbogenerator. Background Art

[0002] The stator winding is an important part of a turbogenerator. The additional losses of the stator winding not only affect the efficiency of the turbogenerator, but also reduce the service life of the turbogenerator. The additional losses of the stator winding are further divided into circulating current losses and eddy current losses. As the capacity of the turbogenerator gradually increases, the degree of saturation becomes more extensive, and the distribution of the leakage magnetic field at various parts of the stator bar becomes more complex. The eddy current losses and circulating current losses caused by the end leakage magnetic field and the slot leakage magnetic field increase accordingly. For eddy current losses, the influence of the slot leakage magnetic field is greater. To reduce the eddy current losses of the stator winding of the turbogenerator, the conductors in the stator slot are generally composed of multiple rows of thin flat copper wires arranged horizontally, and are connected by a tap at the turbine end; for circulating current losses, since each strand in the slot is under the combined influence of the end leakage magnetic field and the slot leakage magnetic field, and the positions are not the same, there is a potential difference between the loops formed by any two strands, thus forming a circulating current in the loop and generating circulating current losses, which seriously affects the working efficiency of the turbogenerator. Summary of the Invention

[0003] The present invention is to solve the problem of excessive circulating current losses and serious temperature rise caused by uneven distribution of the transposed strands in the slot space of the existing stator winding, and provides a method for transposing the strands of the stator bar of a turbogenerator.

[0004] A method for transposing the strands of the stator bar of a turbogenerator, the stator bar of the turbogenerator includes six columns of strands arranged horizontally, each column of strands includes N hollow strands and M solid strands arranged longitudinally, both N and M are positive integers, and the N hollow strands are evenly distributed in the column where they are located;

[0005] The method for transposing the strands of the stator bar of the turbogenerator is as follows:

[0006] When the strands in the first row are solid strands, in the order from right to left,

[0007] The solid strands located in the first and third columns of the first row are respectively moved to the positions of the solid strands in the sixth and fourth columns of the first row. The remaining strands in the first and third columns are all moved a distance equal to the height of one solid strand towards the notch direction. At the same time, the solid strands in the sixth and fourth columns of the last row are respectively moved to the positions of the solid strands in the first and third columns of the last row. The remaining strands in the sixth and fourth columns are all moved a distance equal to the height of one solid strand away from the notch direction; when the solid strands in the first and third columns of the first row are in the middle of the transposition, the solid strand in the second column of the first row is moved to the position of the solid strand in the fifth column of the first row. The remaining strands in the second column are all moved a distance equal to the height of one solid strand towards the notch direction. At the same time, the solid strand in the fifth column of the last row is moved to the position of the solid strand in the second column of the last row. The remaining strands in the fifth column are all moved a distance equal to the height of one solid strand away from the notch direction;

[0008] When the strands in the first row are hollow strands, in the order from right to left,

[0009] the hollow strands located in the first, second, and third columns of the first row are respectively moved to the positions of the hollow strands in the fourth, fifth, and sixth columns of the first row. The remaining strands in the first, second, and third columns are all moved a distance equal to the height of one hollow strand towards the notch direction. At the same time, the hollow strands in the fourth, fifth, and sixth columns of the last row are respectively moved to the positions of the hollow strands in the first, second, and third columns of the last row. The remaining strands in the fourth, fifth, and sixth columns are all moved a distance equal to the height of one hollow strand away from the notch direction.

[0010] Furthermore, during the transposition process of the strands located in the first and third columns, the lifting height of the strands in the first column is higher than that of the strands in the third column.

[0011] Furthermore, all the strands are connected by splicing sleeves at the steam end.

[0012] Furthermore, each strand evenly occupies the space inside the stator slot.

[0013] Furthermore, the above-mentioned stator bar of the turbogenerator includes two short-pitch transposition groups and one long-pitch transposition group. The long-pitch transposition group is located between the two short-pitch transposition groups.

[0014] Furthermore, the outer surface of the strands of the above-mentioned stator bar of the turbogenerator is coated with insulating paint.

[0015] Furthermore, glass ribbon gaskets are provided at the transposition bends of the above-mentioned stator bar of the turbogenerator.

[0016] Furthermore, the ratio of the above-mentioned N to M is 1:2, 1:4, or 1:6.

[0017] A method for transposing strands of a stator bar of a turbogenerator according to the present invention enables each strand to be evenly distributed throughout the space in the slot, thereby reducing the circulating current loss between the transposed strands caused by the uneven leakage magnetic field in the slot, effectively reducing the additional loss and the temperature rise of the stator bar, as well as the circulating current between the strands, and improving the operating efficiency of the generator. At the same time, since the transposition angles of the hollow strands are the same, the hollow strands made of stainless steel material that are not easily deformed can be produced in one go, effectively reducing the production cost of the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FIG. is a perspective view of the stator bar of the turbogenerator according to the present invention.

[0019] Figure 2 FIG. is a top view of the stator bar of the turbogenerator according to the present invention.

[0020] Figure 3 FIG. is an initial cross-sectional view of the stator bar of the turbogenerator of the motor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0022] The slot opening of the turbogenerator is relatively large. If the cross-sectional area of a single wire is too large, a large eddy current loss will be generated. The eddy current loss can be well reduced by reducing the cross-sectional area of a single wire. By designing a stator winding with six rows, the cross-sectional area of a single wire is further reduced compared to the commonly used four-row stator winding, and the eddy current loss can be further reduced. Therefore, the problem is how to arrange the six-row stator winding so that the circulating current is suppressed and at the same time the amplitude of the rising temperature is reduced.

[0023] Refer to Figures 1 to 3 Specifically describing this embodiment, a method for transposing strands of a stator bar of a turbogenerator according to this embodiment, the stator bar of the turbogenerator includes six columns of strands arranged horizontally, and each column of strands includes 4 hollow strands and 16 solid strands arranged longitudinally, and the 4 hollow strands are evenly distributed in the column where they are located.

[0024] The method for transposing strands of the stator bar of the turbogenerator is as follows:

[0025] When the strands in the first row are solid strands, in the stator slot part, in the order from right to left, first the solid strand in the first row of the first column is transposed to the position of the solid strand in the first row of the sixth column, and the remaining strands in the first column all move a distance equal to the height of a solid strand in the direction towards the slot opening. While the solid strand in the first row of the first column is being transposed, the solid strand in the first row of the third column is transposed to the position of the solid strand in the first row of the fourth column, and the remaining strands in the third column all move a distance equal to the height of a solid strand in the direction towards the slot opening.

[0026] When the solid strands in the first and third columns of the first row are transposed to the halfway position, the solid strand in the first row of the second column starts to be transposed. The specific transposition method is that the solid strand in the first row of the second column is transposed to the position of the solid strand in the first row of the fifth column, and the remaining strands in the second column all move a distance equal to the height of a solid strand in the direction towards the slot opening. In this embodiment, the transposition of the solid strands in the second column is delayed because if they were transposed together, the height of the wire bar would become higher, and delaying the transposition will prevent the strands from becoming too high after transposition.

[0027] The strand in the last row of the fourth column is transposed to the position of the strand at the bottom of the third column, and the remaining strands in the fourth column all move a distance equal to the height of a solid strand in the direction away from the slot opening; while the strands in the fourth column are being transposed, the strand in the last row of the sixth column is transposed to the position of the strand in the last row of the first column, and the remaining strands in the sixth column all move a distance equal to the height of a solid strand in the direction away from the slot opening.

[0028] The strand in the last row of the fifth column is transposed to the position of the strand in the last row of the second column, and the remaining strands in the fifth column all move a distance equal to the height of a solid strand in the direction away from the slot opening.

[0029] When the strands in the first row are hollow strands, in the order from right to left,

[0030] The hollow strands in the first, second, and third columns of the first row are respectively moved to the positions of the hollow strands in the fourth, fifth, and sixth columns of the first row. The remaining strands in the first, second, and third columns all move a distance equal to the height of a hollow strand in the direction towards the slot opening. At the same time, the hollow strands in the fourth, fifth, and sixth columns of the last row are respectively moved to the positions of the hollow strands in the first, second, and third columns of the last row. The remaining strands in the fourth, fifth, and sixth columns all move a distance equal to the height of a hollow strand in the direction away from the slot opening.

[0031] Preferably, in this embodiment, during the transposition of the strands located in the first and third columns, the lifting height of the strands in the first column is higher than that of the strands in the third column. All the strands are connected by a splicing sleeve at the steam end. Each strand evenly occupies the space in the stator slot. The stator bar of the turbo-generator includes two short-pitch transposition groups and one long-pitch transposition group, and the long-pitch transposition group is located between the two short-pitch transposition groups. Here, one column of strands in the short-pitch transposition group completes the transposition, and the transposition pitch in the long-pitch transposition group is twice that in the short transposition pitch group. Each of the three transposition pitch groups transposes 180°, and the total transposition in the slot is 540°. The outer surface of the strands of the stator bar of the turbo-generator is coated with insulating paint. A fiberglass tape gasket for strengthening insulation protection is provided at the transposition bend of the stator bar of the turbo-generator.

[0032] In the transposition of the six-row stator bar described in this embodiment, the solid strands in the first, sixth, third, and fourth columns are transposed simultaneously, and the solid strands in the second and fifth columns start to transpose in the middle section of the transposition of the solid strands in the first, sixth, third, and fourth columns, with a certain delay. This not only ensures that the height of the stator bar will not become too high after transposition but also shortens the axial length of the stator bar required for 540° transposition. This transposition method for the six rows of strands is superior to the four-row transposed strands in reducing eddy current loss, and the height of the stator bar after transposition can be the same as that of the four-row transposed strands.

[0033] The higher the height of the transposed stator bar, if the depth of the stator slot remains unchanged, it means that the thickness of the insulation becomes thinner, and there is a risk of insulation breakdown; if the thickness of the insulation remains unchanged, the depth of the stator slot needs to be increased, which means that a new stator core needs to be redesigned. The solid strands in the second and fifth columns with delayed transposition in this embodiment ensure that the height of the stator bar will not be too high after transposition. At the same time, since the transposition of the solid strands in the second and fifth columns starts at the middle position of the transposition of the solid strands in the first, sixth, third, and fourth columns, for the same transposition pitch, the axial distance required to complete 540° transposition using this transposition method is greatly shortened.

[0034] In addition, in the six-row transposition, the hollow strands adopt a different transposition method from the solid strands. This is mainly because the hollow strands made of stainless steel are not easy to roll. The transposition method of transposing the first, fourth, second, fifth, third, and sixth columns simultaneously enables the hollow strands to have the same crossing angle and distance, so that they can be rolled together.

[0035] Although the present invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Accordingly, it should be understood that numerous modifications may be made to the exemplary embodiments, and other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in connection with separate embodiments may be used in other described embodiments.

Claims

1. A method for transposition of strands of a stator bar of a turbogenerator, characterized in that, The stator bar of a turbo-generator comprises six rows of strands arranged horizontally. Each row of strands includes N hollow strands and M solid strands arranged longitudinally, where both N and M are positive integers, and the N hollow strands are evenly distributed in the row where they are located. The method for transposing the strands of the stator bar of a turbo-generator is as follows: When the strands in the first row are solid strands, in the order from right to left, the solid strands in the first and third columns of the first row are respectively moved to the positions of the solid strands in the sixth and fourth columns of the first row, and the remaining strands in the first and third columns are all moved a distance equal to the height of one solid strand towards the slot opening direction. At the same time, the solid strands in the sixth and fourth columns of the last row are respectively moved to the positions of the solid strands in the first and third columns of the last row, and the remaining strands in the sixth and fourth columns are all moved a distance equal to the height of one solid strand away from the slot opening direction. When the transposition of the solid strands in the first and third columns of the first row reaches the halfway position, the solid strand in the second column of the first row is moved to the position of the solid strand in the fifth column of the first row, and the remaining strands in the second column are all moved a distance equal to the height of one solid strand towards the slot opening direction. At the same time, the solid strand in the fifth column of the last row is moved to the position of the solid strand in the second column of the last row, and the remaining strands in the fifth column are all moved a distance equal to the height of one solid strand away from the slot opening direction. When the strands in the first row are hollow strands, in the order from right to left, the hollow strands in the first, second, and third columns of the first row are respectively moved to the positions of the hollow strands in the fourth, fifth, and sixth columns of the first row, and the remaining strands in the first, second, and third columns are all moved a distance equal to the height of one hollow strand towards the slot opening direction. At the same time, the hollow strands in the fourth, fifth, and sixth columns of the last row are respectively moved to the positions of the hollow strands in the first, second, and third columns of the last row, and the remaining strands in the fourth, fifth, and sixth columns are all moved a distance equal to the height of one hollow strand away from the slot opening direction.

2. The method for transposing strands of a stator bar of a turbo-generator according to claim 1, wherein During the transposition process of the strands in the first and third columns, the lifting height of the strands in the first column is higher than that of the strands in the third column.

3. The method for transposing the strands of the stator bar of a turbo-generator according to claim 1, characterized in that all strands are connected by a splicing sleeve at the turbine end.

4. The method for transposing the strands of the stator bar of a turbo-generator according to claim 1, characterized in that each strand evenly occupies the space inside the stator slot.

5. The method for transposing the strands of the stator bar of a turbo-generator according to claim 1, characterized in that the stator bar of the turbo-generator comprises two short-pitch transposition groups and one long-pitch transposition group, and the long-pitch transposition group is located between the two short-pitch transposition groups.

6. A transposition method for strands of a stator bar of a steam turbine generator according to claim 1, characterized in that, The outer surface of the strands of the stator bar of the turbo-generator is coated with insulating paint.

7. A transposition method for strands of a stator bar of a turbogenerator according to claim 1, characterized in that, A fiberglass tape gasket is provided at the transposition bend of the stator bar of the turbo-generator.

8. A transposition method for strands of a stator bar of a turbogenerator according to claim 1, characterized in that, The ratio of N to M is 1:2, 1:4, or 1:6.

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