FORMATION OF STATOR COILS FOR USE IN CONCENTRATED WINDING ELECTRICAL MACHINE

Abstract

A stator assembly, a wind turbine and a method for manufacturing a stator assembly for an electrical machine with a concentrated winding stator design is provided. The method includes (a) providing a stator coil having a first coil axis and a first spatial design with, a first length along a first direction and a first width along a second direction; (b) exerting on the stator coil a tension force along the first direction and/or a compressive force along the second direction such that the first spatial design transforms into a second spatial design with a second length and a second width, wherein the second length is larger than the first length and the second width is smaller than the first width; and (c) placing the stator coil having the second spatial design around a single stator tooth of a stator yoke of the stator assembly.

Claims

1. A method for manufacturing a stator assembly for an electrical machine, for an electrical generator and further for an electrical generator in a wind turbine, wherein the stator assembly is realized with a concentrated winding stator design, in which respectively one stator coil is wound exclusively around one stator tooth, the method comprising providing a stator coil having a first coil axis and a first spatial design width, within a plane being perpendicular to the first coil axis, a first length along a first direction and a first width along a second direction, the second direction being different from the first direction; exerting on the stator coil a tension force along the first direction and/or a compressive force along the second direction such that the first spatial design transforms into a second spatial design with a second coil axis and a second length along the first direction and a second width along the second direction, wherein the second length is larger than the first length and the second width is smaller than the first width; and placing the stator coil having the second spatial design around a single stator tooth of a stator yoke of the stator assembly.

2. The method as set forth in claim 1, further comprising electrically insulating the provided stator coil with an electric insulation material.

3. The method as set forth in claim 1, wherein electrically insulating comprises wrapping an insulating tape around at least a portion of the stator coil.

4. The method as set forth in claim 1, wherein the first coil axis is oriented parallel to the second coil axis.

5. The method as set forth in claim 1, wherein the first coil axis is collinear with the second coil axis.

6. A stator assembly for an electrical machine, the stator assembly comprising a stator yoke with a plurality of stator teeth; and a plurality of stator coils, each being manufactured by a process in which a tension force along a first direction and/or a compressive force along a second direction is exerted on the stator coil such that a first spatial design of the stator coil transforms into a second spatial design of the stator coil, wherein (a) in the first spatial design the stator coil has a first coil axis and a first length along the first direction and a first width along the second direction, wherein the first direction and the second direction are within a plane being perpendicular to the first coil axis, (b) in the second spatial design the stator coil has a second coil axis and a second length along the first direction and a second width along the second direction, the second length being larger than the first length and the second width being smaller than the first width, and (c) respectively one stator coil is located around one single stator tooth.

7. An electrical machine, the electrical machine comprising a stator assembly as set forth in claim 6; and a rotor assembly being rotatably supported at the stator assembly.

8. The electrical machine as set forth in claim 7, wherein the rotor assembly is located radially outward from the stator assembly or the rotor assembly is located radially inward from the stator assembly.

9. The electrical machine of claim 7, wherein the electrical machine is an electrical generator.

10. A wind turbine for generating electrical power, the wind turbine comprising a tower; a wind rotor, which is arranged at a top portion of the tower and which comprises at least one blade; and an electrical machine as set forth in claim 8 and configured as an electrical generator, which is mechanically coupled with the wind rotor.

Description

BRIEF DESCRIPTION

[0033] Some of the embodiments will be described in detail, with references to the following Figures, wherein like designations denote like members, wherein:

[0034] FIG. 1 shows a wind turbine comprising an electrical generator in accordance with embodiments of the invention;

[0035] FIG. 2 shows an enlarged cross-sectional view of the stator assembly and the rotor assembly of the generator 12 of a first embodiment of the electric generator of the wind turbine of FIG. 1;

[0036] FIG. 3 illustrates a formation process for a stator coil in a first spatial design (for distributed winding);

[0037] FIG. 4 illustrates a formation process for a stator coil is carried out by means of a compression tool and a tension tool in both of which the stator coil is inserted; and

[0038] FIG. 5 illustrates a second design in the formation process for a the stator coil which has a second length and a second width.

DETAILED DESCRIPTION

[0039] The illustration in the drawing is schematic. It is noted that in different figures, similar or identical elements or features are provided with the same reference signs or with reference signs, which are different from the corresponding reference signs only within the first digit. To avoid unnecessary repetitions elements or features which have already been elucidated with respect to a previously described embodiment are not elucidated again at a later position of the description. FIG. 1 shows a wind turbine 180 according to embodiments of the invention. The wind turbine 180 comprises a tower 182, which is mounted on a non-depicted fundament. On top of the tower 182 there is arranged a nacelle 184. In between the tower 182 and the nacelle 184 there is provided a yaw angle adjustment device 183, which is capable of rotating the nacelle 184 around a not depicted vertical axis, which is aligned with the longitudinal extension of the tower 182. By controlling the yaw angle adjustment device 183 in an appropriate manner it can be made sure that during a normal operation of the wind turbine 180 the nacelle 184 is always properly aligned with the current wind direction.

[0040] The wind turbine 180 further comprises a wind rotor 190 having three blades 192. In the perspective of FIG. 1 only two blades 192 are visible. The wind rotor 190 is rotatable around a rotational axis 190a. The blades 192, which are mounted at a hub 194, extend radially with respect to the rotational axis 190a.

[0041] In between the hub 194 and a blade 192 there is respectively provided a blade adjustment device 193 to adjust the blade pitch angle of each blade 192 by rotating the respective blade 192 around a not depicted axis being aligned substantially parallel with the longitudinal extension of the blade 192. By controlling the blade adjustment device 193 the blade pitch angle of the respective blade 192 can be adjusted in such a manner that at least when the wind is not so strong a maximum wind power can be retrieved from the available wind power. However, the blade pitch angle can also be intentionally adjusted to a position, in which only a reduced wind power can be captured.

[0042] Within the nacelle 184 there is provided an electric generator 100. In accordance with basic principles of electrical engineering the electric generator 100 comprises a stator assembly 110 and a rotor assembly 120. According to the embodiment described here the electric generator 100 is realized with a so-called inner statorouter rotor configuration. Permanent magnets being attached to the rotor assembly 120 travel around stator segments being attached at the stator assembly 110. In between the stator segments, which comprise stator coils for picking up a time alternating magnetic induction, and the permanent magnets, there is formed an air gap. The stator assembly 110 is realized in the concentrated winding design. Further details are given below.

[0043] The wind rotor 190 is rotationally coupled with the rotor assembly 110 by means of a rotatable shaft 196. A schematically depicted bearing assembly 198 is provided to hold in place both the wind rotor 190 and the rotor assembly 120. As can be seen from FIG. 1, the shaft 196 extends along the rotational axis 190a. The rotational axis 190a is identic with a center axis of the stator assembly 110.

[0044] It is mentioned that the wind turbine 180 is a so-called direct drive wind turbine wherein between wind rotor 190 and rotor assembly 110 there is not provided a gear box. However, it is mentioned that the electric generator 100 could also be driven indirectly via a gear box, which may be used to convert the number of revolutions of the wind rotor 190 typically into a higher number of revolutions of the rotor assembly 120.

[0045] To provide an AC power signal being electrically matched with a power signal of a utility grid the electric output of the stator assembly 110 is electrically connected to a power converter 186. The power converter 186 comprises a generator side AC-DC converter 186a, an intermediate DC bridge 186b, and a grid side DC-AC converter 186c. The AC-DC converter 186a and the DC-AC converter 186c comprise several not depicted high power semiconductor switches, which in a known manner are arranged in a bridge configuration for each phase of an AC current provided by the electric generator 100.

[0046] The wind turbine 180 further comprises a control system 188 for operating the wind turbine 100 in a highly efficient manner. Apart from controlling for instance the yaw angle adjustment device 183 the depicted control system 188 is also used for adjusting the blade pitch angle of the blades 192 of the wind rotor 190 in an optimized manner.

[0047] FIG. 2 shows an enlarged cross-sectional view of the stator assembly 110 and the rotor assembly 120 of the generator 100, which is depicted schematically in FIG. 1. The stator assembly 110 comprises a stator frame structure 212 which itself includes a stator yoke 212 and a plurality of stator teeth 212a. Due to the inner statorouter rotor configuration the stator teeth 212a are directed radially outward from a center axis, which in FIG. 1 is denominated with reference numeral 190a. In between two neighboring teeth 212a there are formed recesses. According to the nomenclature used here one recess corresponds to two neighboring slots 212b (in between two neighboring teeth 212a). Respectively two slots 212b are adjacent to one tooth 212a. This means that one recess is occupied by two slots 212b, wherein each slot 212b is assigned to one stator tooth 212a. Further, in accordance with the concept of concentrated winding two slots 212b being adjacent to one tooth 212a are occupied by exactly one stator coil 214. In accordance with basic electric principles of an electrical generator the stator coils 214 are subdivided into different groups of stator coils 214, wherein each group is assigned to one electric phase. The corresponding electric circuitry for such a grouping is not depicted in FIG. 2 to not to obscure an understanding of this description.

[0048] The rotor assembly 120, which is radially external with respect the stator assembly 110 and which is rotatable about the center axis 190a (see FIG. 1), comprises a rotor frame structure 222 and a plurality of permanent magnets 224. These permanent magnets 224 are attached to an inner side of the rotor frame structure 222, which inner side faces the stator assembly 110. A circumferential air gap 226 is provided between the stator assembly 110 and the rotor assembly 120.

[0049] Each of the stator teeth 212a has a length, which is measured along a direction being perpendicular to the plane of drawing of FIG. 2. The width of each stator tooth 212a is measured along the circumferential direction (around the center axis), which circumferential direction is within the plane of drawing of FIG. 2. It is obvious that to complete a stator coil 214 around a stator tooth 212a it is necessary to provide so called end winding portions or coil heads which are not located within the respective slot. A not depicted front end winding portion or front coil head of the stator coils 214 protrudes out from the plane of drawing of FIG. 2.

[0050] FIGS. 3 to 5 illustrate a formation process for a stator coil from a first spatial design (for distributed winding) to a second spatial design (for concentrated winding). FIG. 3 shows the stator coil 314a when being in the first spatial design. The stator coil 314a comprises several turns, which are arranged in a spiral manner around a first coil axis 315. An upper turn of the coil (above the plane of drawing) comprises a first terminal 319a. A lower turn of the coil (below the plane of drawing) comprises a second terminal 319b. All (not depicted) intermediate turns are connected in serious between the upper most turn with the first terminal 319a and the lower most turn with the second terminal 319b.

[0051] The first spatial design of the stator coil 314a is characterized by a first length L1 (measured along an X axis) and a first with W1 (measured along an Y axis). Although the stator coil 314a already has an elongated shape, the first width W1 is sufficiently large such that dedicated tooling equipment being used for producing the stator coils 314a can be used. Specifically, the inner region of the stator coil 314a (where the first coil axis 315 is depicted) is big enough (along the Y direction) to allow the use of such (known) tooling equipment.

[0052] The turns of the stator coil 314a comprise an electric conductive material 317, copper. To insulate neighboring coils from each other an electric insulation material 318 is provided around the coil (a bundle of turns). According to the embodiment described here the electric insulation material 318 comprises a synthetic tape which is wrapped around the complete stator coil 314a. The above mentioned (known) tooling equipment is used for wrapping this tape around the complete stator coil in an automatic manner.

[0053] To make the stator coil 314a suitable for concentrated winding the spatial design of the stator coil 314a has to be modified towards a more elongated shape. According to the embodiment described here, the corresponding formation of the stator coil 314a is carried out by means of a compression tool 332 and a tension tool 334, in both of which the stator coil 314a is inserted. This is illustrated in FIG. 4.

[0054] In the depicted embodiment the compression tool 332 has a length (along the X direction) such that two portions of the stator coil 314a, which portions are not inserted into the compression tool 332, correspond to so-called end windings or coil heads. In an assembled state of a corresponding stator assembly, these end windings or coil heads are not located within the stator slots (see reference number 212b in FIG. 2). In the first spatial design of the stator coil 314a the length of the end windings or coil heads (along the X direction) is denominated with X0 in FIG. 4.

[0055] To form the stator coil 314a compression forces Fc are exerted on and via the compression tool 332 and tension forces Ft are exerted on and via the tension tool 334. The final state of the stator coil is depicted in FIG. 5. The formed stator coil, which is now suitable for concentrated winding, is denominated with reference numeral 314b. As can be taken from FIG. 5, the stator coil 314b has a second length L2 (along the X direction) and a second width W2 (along the Y direction). Further, due to the formation process the length of the end windings respectively the length of the coil heads is increased. According to the embodiment described here this increased length is double as compared to the corresponding initial length. The corresponding double coil head length is 2X0.

[0056] In the depicted embodiment the compression force Fc and the tension force F are applied in a symmetric manner. This means that in the formation process the second coil axis of stator coil 314b is the same as the first coil axis of the stator coil 314a. In other words, there is a common coil axis for both spatial designs, which common coil axis is denominated with reference numeral 315.

[0057] Using the described stator coil formation process for producing concentrated winding stator coils may provide in particular the following advantages:

(a) A manufacture of narrow stator coils (for concentrated winding) can be carried out with a combination of common electric insulation taping techniques and the described stator coil formation procedure.
(b) There is no more a need for using a small role of insulation tape to insulate the stator coil manually.
(c) In the (broader) first spatial design a coil insulation can be realized with a simple and known electric insulation taping machine.
(d) A high quality of electric insulation can be achieved because the insulation procedure does not depend on manual skill.
(e) An automated production of appropriate stator coils is possible. Hence, production time will be reduced.

[0058] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0059] For the sake of clarity, it is to be understood that the use of a or an throughout this application does not exclude a plurality, and comprising does not exclude other steps or elements.