A stator assembly including an electrical insulation device having an outer surface with a raised surface portion

Abstract

A stator assembly is described, comprising (a) a frame structure having a plurality of stator teeth circumferentially distributed around a longitudinal axis, wherein a stator slot is formed between two adjacent stator teeth respectively; (b) a winding system having a plurality of electrical windings, wherein, respectively, an electrical winding is wound around at least one stator tooth and partially received in two stator slots, and each electrical winding includes an end winding portion axially protruding from the frame structure; and (c) an insulation arrangement structure having a plurality of electrical insulation devices, each insulation device surrounding a part of an electrical winding. Each insulation device includes: (c1) an inner insulation portion received in a corresponding stator slot and an outer insulation portion protruding from the frame structure and surrounding a part of the corresponding end winding portion. The outer insulation portion includes an outer surface which includes a raised surface portion.

Description

Technical Field

[0001] The present invention generally relates to the technical field of electromechanical transducers such as electric motors or generators. Such generators can be used, for example, in wind turbines to convert mechanical power provided by the wind into electrical power to be fed into, for example, the public power grid. Specifically, the present invention relates to electrical insulation measures within a stator assembly for an electromechanical transducer. Background Art

[0002] An electromechanical transducer, such as a generator installed in a wind turbine, includes a rotor assembly that rotates relative to a stator assembly. The stator assembly includes a frame structure having a plurality of stator teeth circumferentially distributed around a longitudinal axis. Stator slots extend in an axial direction parallel to the longitudinal axis. This longitudinal axis is also the rotational axis of the rotor assembly.

[0003] The stator assembly further includes an electrical winding system having a plurality of electrical windings, which are typically made of copper and are also commonly simply referred to as coils. The electrical windings are partially received within two corresponding stator slots. So-called end winding portions project axially from the frame structure.

[0004] To prevent short circuits within the stator assembly, the electrical winding portions received within the stator slots are electrically insulated from the frame structure. The frame structure is typically a stack of a plurality of metal plates that are insulated from each other by means of insulating paint.

[0005] Depending on the voltage class of the electrical transducer, different types and / or designs of insulation means can be used. The insulation means includes, for example, insulating tapes and slot linings, which are also referred to as "slot insulation".

[0006] The end winding portion, also referred to as the "coil overhang", is defined as such a portion of the electrical winding or coil that is located outside the stator slot and is required to connect the "two sides" of the coil. To avoid a high electric field stress intensity at the outlet of the stator slot, it is important that the insulation means projects from the stator slot by a minimum distance, which is referred to as the creepage distance in the stator insulation arrangement.

[0007] The minimum creepage distance necessary for the reliable operation of the electromechanical transducer depends on (a) the root mean square (RMS) value of the voltage given between an electrical phase conductor and the frame structure or between two phase conductors, (b) the type of insulating material, (c) the size of the insulation means, and (d) the operating environment of the electromechanical transducer. Thus, for electromechanical transducers of higher voltage classes, an increased creepage distance is required, resulting in an increased length of the end winding portion, which in turn will increase the resistance losses in the electromechanical transducer and reduce the performance of the electromechanical transducer.

[0008] Of course, the necessary creepage distance can be achieved by simply extending the slot insulation on the end winding portion with an increased voltage level. However, such an extension also increases the length of the end winding portion because (i) the end winding portion is bent and (ii) the insulating device needs to end before the start of the bending of the end winding. Thus, the elongation of the insulating device is accompanied by an increased length of the end winding portion, which, as described above, reduces the performance of the electromechanical transducer.

[0009] Improvement of the performance of the electromechanical transducer may be required. Summary of the Invention

[0010] This need can be met by the subject matter of the independent claims. Advantageous embodiments of the invention are described by the dependent claims.

[0011] According to a first aspect of the invention, there is provided a stator assembly for an electromechanical transducer and in particular for a generator. The provided stator assembly comprises: (a) a frame structure having a plurality of stator teeth circumferentially distributed around a longitudinal axis, wherein a stator slot is formed between two adjacent stator teeth; (b) a winding system having a plurality of electrical windings, wherein (b1) respectively, an electrical winding is wound around at least one stator tooth and partially received in two stator slots, and (b2) each electrical winding includes an end winding portion protruding axially from the frame structure; and (c) an insulating arrangement structure having a plurality of electrical insulating devices, each insulating device surrounding a portion of an electrical winding. Each insulating device comprises (i) an inner insulating portion received in a corresponding stator slot for preventing direct electrical contact between the corresponding electrical winding and the frame structure, and (ii) an outer insulating portion protruding from the frame structure and surrounding a portion of the corresponding end winding portion. The outer insulating portion includes an outer surface which includes raised surface portions (and of course also non-raised surface portions).

[0012] The described stator assembly is based on the idea that by providing raised surface portions for the outer surface of the outer insulating portion, the creepage length between the electrically non-insulated portion of the end winding portion and the frame structure will be increased. This means that the resistance of the unwanted creepage current traveling between (i) the (metal) conductor material of the end winding portion and (ii) the frame structure will be increased, and thus, the amperage of such a creepage current will be reduced.

[0013] The described reduction in the amperage of the creepage current can provide the advantage that, for a given voltage rating of the electromechanical transducer, the overhang length of the outer insulation part can be reduced. Thereby, the end winding length can be shortened. This in turn reduces the resistive losses in the entire winding. Consequently, the performance of the electromechanical transducer will be improved. In addition, the reduction in the overhang length of the end winding part allows the electromechanical transducer to be realized within a space-compact design and / or with a reduced amount of (metal) conductor material necessary for the end winding part.

[0014] In this document, the term "raised surface part" can particularly relate to the height level of a part of the outer surface of the outer insulation part, which is different and particularly lower than the height level of another non-raised surface part and / or another surface part that is raised to a lesser extent. Thus, the "height" is not the height that is usually referred to as the z coordinate in three-dimensional space. Instead, the term "height" refers to the distance between (i) the corresponding raised surface part and (ii) the conductor material of the corresponding end winding part.

[0015] In the case where the outer insulation part is made of solid insulating material and does not include a cavity, the term "height" can also be regarded as describing the thickness of the insulating material of the outer insulation part. In this case, the presence of a raised (and of course also non-raised) surface part may mean that the insulating material of the outer insulation part surrounding the conductor material of the corresponding end winding has an uneven thickness.

[0016] In the described stator assembly, the axial protrusion of the end winding part is given in a direction parallel to the longitudinal axis of the frame structure. Only for the sake of clarity, it is noted that this longitudinal axis can be collinear with the rotational axis of the rotor assembly of the electromechanical transducer.

[0017] Regarding the insulation part, the terms "outer" and "inner" refer to the direction parallel to the longitudinal axis. In contrast, the outer surface of the outer insulation part is the surface that faces away from the conductor material of the corresponding end winding part.

[0018] It is mentioned that typically, an electric winding includes two end winding parts, which protrude from the frame structure in opposite directions, both of which are parallel to the longitudinal axis. This means that, in addition to the inner insulation part and the mentioned outer insulation part, the (electrical) insulation means usually also includes additional outer insulation parts. Thereby, one of the two outer insulation parts is assigned to one end winding part.

[0019] In addition, it is mentioned that in order to electrically insulate an electric winding accommodated in two stator slots from the frame structure, two insulation means can be used. Thereby, one insulation means is assigned to one of the two stator slots.

[0020] According to an embodiment of the present invention, the raised surface portion of the outer insulation portion is spatially distributed and formed such that along the protruding direction, there is a change in the thickness of the insulating material of the outer insulation portion that surrounds the corresponding portion of the corresponding end winding portion. Thus, the protruding direction is parallel to the longitudinal axis of the entire stator assembly.

[0021] According to another embodiment of the present invention, the raised surface portion forms a ring, and each ring surrounds the corresponding portion of the corresponding end winding portion in a ring shape. This can provide the outer insulation portion and in particular a three-dimensionally formed or curved outer surface of the outer insulation portion including a relatively simple spatial design, which can be formed in a simple and easy manner.

[0022] According to another embodiment of the present invention, the raised surface portion forms at least one elongated raised structure that surrounds the corresponding portion of the corresponding end winding portion in a spiral manner. This embodiment can also provide the advantage that it can be achieved in a simple and easy manner, for example, by twisting an initially tubular or sleeve-shaped member made of insulating material.

[0023] According to another embodiment of the present invention, the outer insulation portion is made of two parts, an inner part having a tubular shape with a uniform wall thickness, and an outer part having a non-uniform wall thickness or a corrugated shape. This embodiment can also provide the advantage that the outer insulation portion can be manufactured in a simple and easy manner.

[0024] According to another embodiment of the present invention, the outer part is a corrugated member.

[0025] The corrugations can be pre-formed or can be generated during processing, where the outer part is applied over the inner part. Due to the mechanical friction between the outer surface of the inner part and the inner surface of the outer part, the formation of the corrugations can be given during application.

[0026] According to another embodiment of the present invention, the inner part is integrally formed with the inner insulation portion. Moreover, such a structural design feature can allow for further simplification of the formation or manufacture of the entire insulation device.

[0027] According to another embodiment of the present invention, the stator assembly includes the following feature: with respect to the outer insulation portion having a flat outer surface and no raised surface portion, the raised surface portion results in an increase in the creepage length of the creepage current traveling from the uninsulated conductor material of the corresponding end winding portion to the frame structure.

[0028] As already mentioned above, the increase in the creepage length can allow for the realization of a stator assembly (of a specific voltage class) having a shorter end winding.

[0029] According to another embodiment of the present invention, the creepage length is increased to at least 1.2 times, preferably to 1.4 times, more preferably to 1.5 times.

[0030] According to another embodiment of the present invention, an electric winding is received in two adjacent stator slots. This means that the electric winding is wound only around one stator tooth, and the winding system is implemented in a so-called concentrated winding design. Therefore, the above-mentioned increase in creepage length can also be used for a concentrated winding stator assembly.

[0031] According to another embodiment of the present invention, an electric winding is received in two stator slots that are circumferentially spaced apart such that at least one other stator slot is arranged between the two stator slots. This means that the corresponding electric winding is wound around at least two stator teeth. This type of winding system configuration is generally referred to as a distributed winding design. Therefore, the above-mentioned increase in creepage length can also be used for a distributed winding stator assembly.

[0032] According to another aspect of the present invention, there is provided an electromechanical transducer for converting mechanical energy into electrical energy or vice versa to convert electrical energy into mechanical energy. The provided electromechanical transducer includes (a) a stator assembly as described above and (b) a rotor assembly rotatable about a longitudinal axis.

[0033] The provided electromechanical transducer is based on the concept that by utilizing the above-mentioned improved creepage current characteristics of the stator assembly, the performance of the electromechanical transducer can be improved in a relatively simple and easy manner. In addition, as already mentioned above, the entire electromechanical transducer can be implemented in a compact manner and / or, particularly with respect to the amount of conductor material required for forming the end windings, in an efficient and economical manner.

[0034] The rotor assembly may include permanent magnets that interact electromagnetically with the electric windings of the winding system during operation. The rotor assembly and the stator assembly may be spatially designed such that an air gap is formed between the permanent magnets and the electric windings.

[0035] The described electromechanical transducer may be a synchronous machine and, in particular, a synchronous generator.

[0036] According to another aspect of the present invention, there is provided a wind turbine for generating electric power. The provided wind turbine includes (a) a tower; (b) a nacelle arranged at the top of the tower; (c) a wind rotor arranged at the front end of the nacelle and including at least one blade; and (d) an electromechanical transducer as described above.

[0037] According to another aspect of the present invention, there is provided a method for manufacturing a stator assembly. The stator assembly may be the stator assembly as described above. The provided method includes (a) forming a frame structure having a plurality of stator teeth circumferentially distributed around a longitudinal axis, wherein a stator slot is formed between two adjacent stator teeth respectively; (b) forming a winding system having a plurality of electrical windings, wherein (b1) respectively, an electrical winding is wound around at least one stator tooth and partially received in two stator slots, and (b2) each electrical winding includes an end winding portion protruding axially from the frame structure; and (c) forming an insulation arrangement structure having a plurality of electrical insulation devices, each insulation device surrounding a part of an electrical winding. Each insulation device includes (i) an inner insulation portion received in a corresponding stator slot for preventing direct electrical contact between the corresponding electrical winding and the frame structure, and (ii) an outer insulation portion protruding from the frame structure and surrounding a part of the corresponding end winding portion. The outer insulation portion includes an outer surface, which includes raised surface portions (and non-raised surface portions).

[0038] It must be noted that embodiments of the present invention have been described with reference to different subjects. In particular, some embodiments have been described with reference to method-type claims, while other embodiments have been described with reference to device-type claims. However, those skilled in the art will understand from the above and following descriptions that, unless otherwise stated, any combination between features related to different subjects, in particular any combination between the features of method-type claims and the features of device-type claims, is also considered to be disclosed with this document, in addition to any combination of features belonging to one type of subject.

[0039] The above and other aspects of the present invention are apparent from the examples of the embodiments to be described below and are explained with reference to the examples of the embodiments. The present invention will be described in more detail below with reference to the examples of the embodiments, but the present invention is not limited to the examples of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A wind turbine including a generator according to an embodiment of the present invention is shown.

[0041] Figure 2 Shown is Figure 1 an enlarged cross-sectional view of the stator assembly and the rotor assembly of the generator of the wind turbine.

[0042] Figure 3 The stator assembly implemented in a concentrated winding design is shown in a circumferential view.

[0043] Figure 4 The stator assembly implemented in a distributed winding design is shown in a circumferential view.

[0044] Figure 5 Shows the stator winding insulation design according to the first embodiment of the present invention.

[0045] Figure 6 Illustrates an exemplary increase in the creepage length of the outer insulation portion having a curved raised surface portion.

[0046] Figure 7 Illustrates an exemplary increase in the creepage length of the outer insulation portion having a trapezoidal raised surface portion.

[0047] Figure 8 Shows the stator winding insulation design according to the second embodiment of the present invention.

[0048] Figure 9 Illustrates an exemplary increase in the creepage length of the outer insulation portion having a raised surface portion implemented with an annular ring. Detailed Description

[0049] The illustrations in the drawings are schematic. Note that in different figures, similar or identical elements or features are provided with the same reference numerals or reference numerals that differ only in the first digit from the corresponding reference numerals. To avoid unnecessary repetition, elements or features that have been described with reference to the foregoing embodiments will not be described again in a later part of the specification.

[0050] Figure 1 Shows a wind turbine 180 according to an embodiment of the present invention. The wind turbine 180 includes a tower 182 mounted on a base (not shown). A nacelle 184 is disposed on top of the tower 182. A yaw angle adjustment device 183 is provided between the tower 182 and the nacelle 184, which is capable of rotating the nacelle 184 about a vertical axis (not shown) that is aligned with the longitudinal extension of the tower 182.

[0051] The wind turbine 180 further includes a wind rotor 190 having three blades 192. In Figure 1 the perspective view, only two blades 192 are visible. The wind rotor 190 is rotatable about a rotational axis 190a. This allows the nacelle to be aligned with the direction of the wind that drives the wind rotor. The blades 192 mounted at the hub 194 extend radially with respect to the rotational axis 190a.

[0052] Blade adjustment devices 193 are respectively provided between the hub 194 and the blades 192 to adjust the blade pitch angle of each blade 192 by rotating the corresponding blade 192 about an axis (not shown) that is aligned substantially parallel to the longitudinal extension of the blade 192. By controlling the blade adjustment devices 193, the blade pitch angle of the corresponding blade 192 can be adjusted to control the energy capture from the wind that drives the wind rotor 190.

[0053] In the nacelle 184, a generator 100 is provided. According to the basic principles of electrical engineering, the generator 100 includes a stator assembly 110 and a rotor assembly 120. According to the embodiments described herein, the generator 100 is implemented in a so-called inner stator - outer rotor configuration. The permanent magnets attached to the rotor assembly 120 travel around the stator segments attached to the stator assembly 110. An air gap is formed between the stator segments including the stator windings or coils for picking up the time-varying magnetic induction and the permanent magnets. According to the embodiments described herein, the stator assembly 110 is implemented in a concentrated winding design. Further details are given below.

[0054] The wind rotor 190 is rotatably coupled to the rotor assembly 110 by means of a rotatable shaft 196. A bearing assembly 198, schematically shown, is provided to hold the wind rotor 190 and the rotor assembly 120 in place. As can be seen from Figure 1 it, the shaft 196 extends along the axis of rotation 190a. The axis of rotation 190a is the same as the central axis of the stator assembly 110.

[0055] It is mentioned that the wind turbine 180 is a so-called direct drive wind turbine, in which no gearbox is provided between the wind rotor 190 and the rotor assembly 120. However, it is mentioned that the generator 100 can also be indirectly driven by the wind rotor 190 via a gearbox, which can be used to generally convert the number of revolutions of the wind rotor 190 into a higher number of revolutions of the rotor assembly 120.

[0056] To provide an AC power signal that is electrically matched to the power signal of the public power grid receiving the electrical power from the wind turbine 180, the electrical output of the stator assembly 110 is electrically connected to a power converter 186. The power converter 186 includes 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 include a number of high-power semiconductor switches (not shown), which are arranged in a known manner in a bridge configuration for each phase of the AC current provided by the generator 100. Although not shown in the drawings, it should be noted that the power converter 186 is generally connected to the public power grid via a common transformer. The wind turbine 180 is not a so-called stand-alone wind turbine 180.

[0057] The wind turbine 180 further includes a control system 188 for operating the wind turbine 100 in an efficient manner. In addition to controlling, for example, the yaw angle adjustment device 183, the shown control system 188 is also used to adjust the blade pitch angle of the blades 192 of the wind rotor 190 in an optimized manner.

[0058] Figure 2 is shownFigure 1 An enlarged cross-sectional view of the stator assembly 110 and the rotor assembly 120 of the generator 100 schematically shown in []. The stator assembly 110 includes a stator frame structure 212 and a plurality of stator teeth 212a. The frame structure 212 and the stator teeth 212a represent the stator yoke. Due to the inner stator - outer rotor configuration, the stator teeth 212a point radially outward from the central axis, which in [[]] Figure 1 is denoted by the reference numeral 190a.

[0059] A recess is formed between two adjacent teeth 212a, which is defined as a slot 212b in this document. According to the concept of concentrated windings, one slot 212b is occupied by two stator windings 214. One of the two stator windings 214 wraps around one tooth 212a, and the other wraps around the adjacent tooth 212a. According to the basic electrical principle of the generator, the stator windings 214 are subdivided into different groups of stator windings 214, where each group is assigned to one electrical phase. To avoid obscuring the understanding of this specification, in [[]] Figure 2 the corresponding circuitry for such "grouping" is not shown.

[0060] Radially outward relative to the stator assembly 110 and rotatable about the central axis 190a (see [[]] Figure 1 ) the rotor assembly 120 includes a rotor frame structure 222 and a plurality of permanent magnets 224. These permanent magnets 224 are attached to the inner side of the rotor frame structure 222, which faces the stator assembly 110. A circumferential air gap 226 is provided between the stator assembly 110 and the rotor assembly 120.

[0061] Each stator tooth 212a has a length measured in a direction perpendicular to the Figure 2 drawing plane. The width of each stator tooth 212a is measured in the circumferential direction (around the central axis), which is in the Figure 2 drawing plane. Obviously, in order to complete the stator windings 214 around the stator teeth 212a, so-called end winding portions or coil heads that are not located within the corresponding slots must be provided. The end winding portions or coil heads of the stator windings 214 ( Figure 2 not shown in [[]]) project from the Figure 2 drawing plane.

[0062] Figure 3The stator assembly 310 implemented in a so-called concentrated winding design is shown in a circumferential view. Each slot 212b houses a section of two windings 314. With respect to the corresponding slot 212b, one of the two windings 314 is wound individually around the "left" tooth 212a, and the other of the two windings 314 is wound individually around the right tooth 212a. In addition to the portion directly received within the slot 212b, each winding 314 includes a so-called end winding portion 314a that axially protrudes from the stator teeth 212a from the frame structure.

[0063] The stator end windings 314a made of solid and mechanically rigid material are entirely located in air. Therefore, there is no need to provide electrical insulation for the end windings. Of course, this is not the case for the sections of the windings 314 received within the slots 212b. In the region of the slots 212b, electrical insulation ( Figure 3 not shown in the figure) is necessary. As already mentioned in the introduction section of this document, this electrical insulation protrudes from the stator slots 212b to a certain extent.

[0064] Figure 4 The stator assembly 410 implemented in a so-called distributed winding design is shown in a circumferential view. In this design, one stator winding is wound around several stator teeth 212a. In addition, one slot 212b houses only a part of one winding 414. According to the exemplary embodiment described herein, the three windings 414 respectively assigned to one electrical phase are arranged in a staggered manner with respect to each other in space.

[0065] Figure 5 A stator winding insulation design according to a first embodiment of the present invention is shown in a cross-sectional view. For the sake of clarity, only the sections of the stator windings 314 (and the sections of the stator end windings 314a) are shown. The section of the stator winding 314 directly received between two stator teeth 212a is denoted by reference numeral 514b.

[0066] The stator winding 314 is surrounded by an insulation device 530. The insulation device 530 includes an inner insulation portion 532. The inner insulation portion 532 is directly located within the stator slot formed between two stator teeth 212a.

[0067] The insulating device 530 further includes an outer insulating portion 534 which (a) axially projects from a stator yoke including two shown stator teeth 212a, and (b) covers an outer surface of a section of the (metal) stator end winding 314a. The outer surface 535 of the outer insulating portion 534 has a corrugated shape with raised surface portions 536. This corrugated shape results in an increase in the length that an unwanted creepage current must "travel" when "traveling" along the surface of the outer insulating portion 534 between the "uncovered portion" of the end winding 314a and the stator yoke. With this increase in the creepage length, the resistance for the creepage current will increase. This results in a decrease in the amperage of this unwanted creepage current.

[0068] As can be generally seen from Figure 5 In the basic aspect of the invention described in this document, by using the raised surface portion, the creepage length at the stator slot exit will increase without increasing the (axial) length of the outer insulating portion. Accordingly, the voltage rating of the corresponding stator assembly will increase.

[0069] According to Figure 5 In the described embodiment, the outer insulating portion 534 is made of two parts. The inner portion 534a has a generally tubular shape with a uniform wall thickness, and the outer portion 534b has a corrugated shape. This allows the inner portion 534a of the insulating device 530 to be preformed in shape to form the inner dimensions of the slot between two adjacent stator teeth 212a. The outer corrugated portion 534b can be made of the same material as the inner cylindrical portion 534a. The material can be paper. The outer portion 534b can be attached to the inner portion 534b, for example, by means of a two-component adhesive.

[0070] Figure 6 and Figure 7 illustrates examples of possible corrugated shapes with an estimated increase in creepage length. From the dimensions given in these figures, it can be easily calculated that Figure 6 the design shown in Figure 7 where the raised surface portion is a curved surface portion increases the creepage length by 49%.

[0071] Figure 8 shows another stator winding insulation design with an insulating device 830. Similarly, the inner insulating portion 832 of the insulating device 830 is directly located within the stator slot formed between two adjacent stator teeth 212a. The outer insulating portion 834 of the insulating device 830 projects axially from the stator yoke.

[0072] In Figure 8In the cross-sectional view, the outer surface 835 of the outer insulation portion 834 includes a stepped shape. The upper part or more precisely the radially flat portion represents the raised surface portion 836. It can be easily understood that this type of outer surface 835 also results in an increase in the creepage length.

[0073] The stepped shape of the outer surface 835 can be achieved by means of an annular ring extending around the inner cylindrical portion of the outer insulation portion 834. This results in a design as Figure 8 illustrated. However, in other embodiments not shown, the raised surface portion can be achieved by an elongated raised structure that spirally wraps around the inner cylindrical portion of the outer insulation portion 834.

[0074] According to a very specific exemplary embodiment, the raised surface portion 836 can be achieved by a roving rope knot formed on the cylindrical inner portion of the outer insulation portion 834.

[0075] Figure 9 Illustrated Figure 8 is an exemplary increase in the creepage length of the design shown. From the dimensions given in this figure, it can be easily calculated that this design with a stepped outer surface increases the creepage length by 57%.

[0076] It should be noted that the term "comprising" does not exclude other elements or steps, and the use of the article "a" or "an" does not exclude a plurality. In addition, elements described in connection with different embodiments can be combined. It should also be noted that the reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

1. A stator assembly (110) for an electromechanical transducer, the stator assembly comprising: A frame structure (212) having a plurality of stator teeth (212a) circumferentially distributed around a longitudinal axis (190a), wherein a stator slot (212b) is formed between two adjacent stator teeth (212a); A winding system having a plurality of electrical windings, wherein, Respectively, an electrical winding is wound around at least one stator tooth (212a) and partially received within two stator slots (212b), and Each electrical winding includes an end winding portion that axially protrudes from the frame structure (212); and An insulation arrangement structure having a plurality of electrical insulation devices (530, 830), each electrical insulation device (530, 830) surrounding a portion of an electrical winding; Wherein each electrical insulation device (530, 830) includes: An inner insulation portion received within a corresponding stator slot (212b) for preventing direct electrical contact between the corresponding electrical winding and the frame structure (212), and An outer insulation portion protruding from the frame structure (212) and surrounding a portion of the corresponding end winding portion; Wherein the outer insulation portion includes an outer surface (535, 835), the outer surface including a raised surface portion, The outer insulation portion is made of two parts, an inner part (534a) having a tubular shape with a uniform wall thickness and an outer part (534b) having a non-uniform wall thickness or a corrugated shape.

2. The stator assembly according to claim 1, wherein, The raised surface portion of the outer insulation portion is spatially distributed and formed such that a thickness variation of the insulation material of the outer insulation portion is given along the protruding direction, the insulation material surrounding the corresponding portion of the corresponding end winding portion.

3. The stator assembly according to any one of the preceding claims 1 to 2, wherein, The raised surface portion forms a ring, each ring circumferentially surrounding the corresponding portion of the corresponding end winding portion in a ring shape.

4. The stator assembly according to any one of the preceding claims 1 to 2, wherein, The raised surface portion forms at least one elongated raised structure, the elongated raised structure spirally surrounding the corresponding portion of the corresponding end winding portion.

5. The stator assembly according to claim 1, wherein, The outer part (534b) is a corrugated member.

6. The stator assembly according to claim 1 or 5, wherein, The inner part (534a) is integrally formed with the inner insulation portion.

7. The stator assembly according to claim 1 or 2, wherein, The raised surface portion causes an increase in the creepage length of the creepage current traveling from the uninsulated conductor material of the corresponding end winding portion to the frame structure (212).

8. The stator assembly according to claim 7, wherein, The creepage length is increased to at least 1.2 times.

9. The stator assembly according to claim 8, wherein, The creepage length is increased to 1.4 times.

10. The stator assembly according to claim 8, wherein, The creepage length is increased to 1.5 times.

11. The stator assembly according to claim 1 or 2, wherein, An electric winding is received within two adjacent stator slots (212b).

12. The stator assembly according to claim 1 or 2, wherein, An electric winding is received within two stator slots (212b), the two stator slots being circumferentially spaced apart such that at least one other stator slot (212b) is disposed between the two stator slots (212b).

13. The stator assembly according to claim 1 or 2, wherein, The electromechanical transducer is a generator (101).

14. An electromechanical transducer (100) for converting mechanical energy into electrical energy or vice versa to convert electrical energy into mechanical energy, the electromechanical transducer (100) comprising: The stator assembly (110) according to any one of claims 1 to 13, and A rotor assembly (120) that is rotatable about a longitudinal axis (190a).

15. A wind turbine (180) for generating electrical power, the wind turbine (180) comprising: A tower (182); A nacelle (184) disposed at a top end of the tower (182); A wind rotor (190) disposed at a front end of the nacelle (184) and including at least one blade (192); and The electromechanical transducer (100) as claimed in claim 14, wherein the rotor assembly (120) of the electromechanical transducer (100) is mechanically coupled to the wind rotor (190).

16. A method for manufacturing a stator assembly (110), the method comprising: Forming a frame structure (212) having a plurality of stator teeth (212a) circumferentially distributed about a longitudinal axis (190a), wherein a stator slot (212b) is formed between two adjacent stator teeth (212a); Forming a winding system having a plurality of electric windings, wherein, Respectively, an electric winding is wound around at least one stator tooth (212a) and partially received within two stator slots (212b), and Each electric winding includes an end winding portion that axially protrudes from the frame structure (212); and Forming an insulation arrangement structure having a plurality of electrical insulation devices (530, 830), each electrical insulation device (530, 830) surrounding a portion of an electric winding; Wherein each electrical insulation device (530, 830) comprises: An inner insulation portion received within a corresponding stator slot (212b) for preventing direct electrical contact between the corresponding electric winding and the frame structure (212), and An outer insulation portion protruding from the frame structure (212) and surrounding a portion of the corresponding end winding portion; Wherein the outer insulation portion includes an outer surface (535, 835), the outer surface including raised surface portions (536, 836), The outer insulation portion is made of two parts, an inner part (534a) having a tubular shape with a uniform wall thickness and an outer part (534b) having a non-uniform wall thickness or a corrugated shape.

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