Rotor for motor

Abstract

A rotor for an electric motor, particularly a generator for a direct-drive wind turbine (19), the rotor comprising a cylindrical rotor housing (2) having a plurality of magnet devices (4) arranged on an inner housing surface (3), wherein each magnet device (4) comprises a plurality of magnet elements (5) arranged in rows (6) parallel to the axis of rotation, wherein the inner housing surface (3) is provided with at least one groove-shaped recess (7) extending parallel to the axis of rotation, wherein each recess (7) is covered by the magnet elements (5) in the rows (6), and wherein at least two magnet elements (5) in at least some rows (6) are arranged with at least one gap (14) extending in the circumferential direction, the gap (14) communicating with the corresponding recess (7).

Description

Technical Field

[0001] The present invention relates to a rotor for an electric motor (especially a generator for a direct-drive wind turbine), the rotor comprising a cylindrical rotor housing having a plurality of magnetic devices arranged on an inner housing surface. Background Technology

[0002] As is generally known, a wind turbine includes a tower, with a nacelle disposed at the top of the tower. The wind turbine further includes a plurality of turbine blades attached to a hub of the nacelle. These blades interact with the wind, causing the hub to rotate. A generator is coupled to the hub and is driven by the rotating hub. The hub is coupled to a rotor of the generator, which rotates about a stator in a direct-drive arrangement. The rotor includes a cylindrical rotor housing. On the surface of the inner housing, a plurality of magnetic devices are arranged in a uniformly distributed manner along the circumferential direction, wherein these magnetic devices are typically arranged in a single row extending parallel to the rotor's axis of rotation. As the rotor rotates about the stator, the rotor's magnetic devices interact with the corresponding stator windings, thereby inducing current in the stator windings, as is generally known.

[0003] On the other hand, eddy currents are induced in the magnet components or, respectively, the rotor housing. These eddy currents cause the temperature of the magnet components to rise, especially in concentrated winding generators. The temperature rise can negatively affect the magnetic properties of the magnet components, and thus negatively affect the performance of the motor or generator.

[0004] To counteract this undesirable temperature problem, electric motors or generators (especially those used in direct-drive turbines) employ forced air cooling systems. Airflow passes through the air gap between the rotor and stator, thereby flowing along the magnetic elements. While some cooling is provided at the axial ends of the rotor (where the airflow enters the gap between the rotor and stator), the cooling effect decreases towards the center as the air temperature rises. Therefore, this forced air cooling system does not provide sufficient cooling because the magnetic components still experience higher temperatures in the middle or central regions than on the axial sides. Consequently, each magnetic component exhibits a temperature gradient, rather than providing a uniform temperature distribution. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide an improved rotor and improved cooling for the magnet device.

[0006] To address this objective, the present invention proposes a rotor for an electric motor, particularly a generator for a direct-drive wind turbine, the rotor comprising a cylindrical rotor housing having a plurality of magnetic devices arranged on the surface of an inner housing, characterized in that each magnetic device comprises a plurality of magnetic elements arranged in a row parallel to the axis of rotation, wherein the surface of the inner housing is provided with at least one groove-shaped recess extending parallel to the axis of rotation, wherein each recess is covered by the magnetic elements in the row, and wherein at least two magnetic elements in at least some rows are arranged with at least one gap extending in the circumferential direction, the gap communicating with the corresponding recess.

[0007] The rotor housing is designed with several recessed grooves extending along the longitudinal direction of the rotor housing or parallel to the axis of rotation. These recessed grooves are preferably evenly distributed around the inner circumference of the rotor housing. Individual magnetic devices, also extending along the longitudinal direction of the housing or parallel to the axis of rotation, are each implemented by a number of individual magnetic elements arranged in a row to form a corresponding row. The magnetic elements in each row are arranged such that, viewed radially, they cover the recessed grooves, providing a separate air chamber or channel beneath each individual row, realized through the corresponding recess. Furthermore, at least two magnetic elements in at least some rows are arranged with a small gap between them, while all other magnetic elements in each row are directly adjacent to each other, making the corresponding row closed except for the gap extending circumferentially. This gap communicates with the recess beneath that row. Since the gap is open towards the air gap between the rotor and stator on the inner side and the recess on the outer side, airflow from the air gap on the stator side through slits into the recess or vice versa is possible. This airflow allows for a certain amount of airflow or convection within the recess, thus undergoing a constant change, enabling a specific airflow through the recess, which opens to the surrounding environment at least at one point. Therefore, cooling air can enter from the air gap between the rotor and stator into the gap between the magnetic elements, then through this gap into the recess, flowing through the recess and exiting at its opening into the surrounding environment. Alternatively, the airflow can proceed in the reverse direction, where cooling air first enters the recess through the opening, flows through the recess, exits through the gap between the magnetic elements, and enters the gap between the rotor and stator.

[0008] Therefore, a device for active airflow cooling of the magnet elements is provided by an inventive arrangement on the bottom side of the magnet elements (i.e., on the side where the magnet elements are arranged in the rotor housing, inducing eddy currents in the rotor housing). Due to the constant airflow, adequate cooling is provided not only on the open side of the magnet elements facing the stator, but also on the opposite side or on the bottom side arranged in or facing the rotor housing. Furthermore, since a certain airflow is achieved through the recess, active cooling can also be provided in areas where cooling is impossible under prior art arrangements, especially in the middle or central region of the rotor. Thus, forced convection through the recess allows for increased heat transfer between the rotor housing or magnet elements and the cooling air, thereby mitigating or preventing temperature hotspots or uneven temperature distribution along each row of magnet elements.

[0009] As mentioned, each recess opens to the surrounding environment at at least one point, such that at least one opening of the recess opens to the surrounding environment. This opening can be a radial opening, such that the recess opens towards the stator. This can be achieved through a suitable arrangement of magnetic elements that do not completely cover the recess, but leave a small opening or slit at at least one axial end of the recess. Alternatively, two corresponding radial openings can be provided at the two axial ends of the recess, allowing cooling air to enter or exit the recess at the two longitudinal ends. In a preferred embodiment, as an alternative to these openings, the invention proposes that each recess opens to the surrounding environment at one or both longitudinal ends. Thus, the recessed groove is provided with one or two axial openings that open along the axial direction at one or two opposite axial recess ends, allowing air to enter or exit the recess from the axial side of the rotor housing or the arrangement of the magnetic elements. This arrangement is advantageous because cooling air preferably flows into the air gap between the rotor and stator from both axial sides, making it entirely possible for air to enter the respective recesses in parallel from both axial sides. After passing through the recesses, the air exits through at least the gap or slit between at least one pair of magnet elements in the corresponding row, and flows to or through the stator. Thus, a circulating airflow is achieved, wherein cooling air enters synchronously into the gap between the rotor and stator and into all the recesses from the same side.

[0010] Such forced convection or airflow is possible because the at least one gap or slit within the arrangement of the magnet elements creates a flow channel between the recess and the gap between the rotor and stator, thus allowing airflow to circulate from the spaced openings of the recess to the gaps or slits in the row of magnet elements. Since temperature hotspots are present in the central region of the rotor housing or each longitudinal magnet device in a known arrangement, the invention further proposes that, viewed longitudinally, the at least one gap is arranged in the central region of the row. This confirms that cooling air, preferably entering the recess from both ends, flows completely through the recess and exits in the gap or slit in the central region, thereby also allowing for proper cooling of the central region.

[0011] While a positive cooling effect is already recognized using only a single gap or slit in the corresponding row of magnet elements (which requires separating only one pair of adjacent magnet elements to achieve the gap), it is certainly possible to provide more than one gap in the corresponding row. According to this embodiment, for example, two or three gaps or slits are provided at different longitudinal locations in the corresponding row, allowing cooling air to exit the recess at different locations, thus allowing for greater flow. Providing more gaps within the corresponding row requires separating even more pairs of adjacent magnet elements to achieve the corresponding gaps or slits. Finally, it is, of course, possible to provide such gaps or slits between each pair of magnet elements in the corresponding row.

[0012] According to a preferred embodiment of the invention, at least one gap or slit is provided in each row. While it is certainly possible, for example, to provide such a gap or slit only in each second row (which already has a positive effect on the overall cooling or tempering of the rotor), it is certainly advantageous to provide at least one gap or slit in each row so that all the magnetic elements arranged on the inner circumference of the rotor housing can be actively cooled by forced airflow circulation through the recesses. Of course, also according to this embodiment, more than one gap or slit may be provided in each row.

[0013] When all rows are provided with one or the same number of gaps or slits, it is preferable that, viewed in the longitudinal direction, the slits of all rows are arranged at the same one or more longitudinal positions. According to this embodiment, viewed in the circumferential direction, the arrangement of the magnetic elements in all rows is identical, such that, for example, the position of a single gap in the central region of each row is also identical in each row. Therefore, the single gaps in all rows are arranged in a common circumferential plane. Of course, if, for example, two or three gaps are provided in each row, then these three gaps in all rows are also arranged in two or three separate circumferential planes. This confirms that the distribution of magnetic elements within each row is identical, such that, viewed in both the circumferential and longitudinal directions, the overall magnetic properties of the rotor are also largely uniform.

[0014] Viewed along the longitudinal direction of the respective row, the width of each gap is preferably between 0.5 and 10 mm, and most preferably between 1 and 6 mm. The gap or slit is small, but wide enough to achieve forced convection or airflow. It also does not negatively affect the magnetic field generated by the respective magnetic device or row of magnetic elements.

[0015] As mentioned, the magnet elements are arranged and fixed on the surface of the inner housing. To simplify this fixing, each magnet element preferably includes a base plate and a magnet arranged on the base plate, wherein the rotor housing is provided with grooves arranged on two longitudinal sides of each recess, and each row of base elements engages in these grooves. This tongue-and-groove connection allows for simple arrangement of the magnet elements, as it only requires inserting the sides or edges of the opposing tongues of the base plate (i.e., their side edges) into the axially open and opposing grooves of the rotor housing and moving them into the desired longitudinal position. A simple form-fit arrangement is achieved, wherein the corresponding magnet elements are definitively fixed in their final longitudinal position such that movement is impossible after they are finally fixed.

[0016] Each recess itself preferably has a rectangular cross-section, but it may of course also have a convex cross-section, etc.

[0017] In the first alternative, each row provides only one recess, and this recess is covered by the magnetic elements of that row. According to the second alternative, two or more parallel groove-shaped recesses are provided, and these groove-shaped recesses are covered by the magnetic elements in the row.

[0018] Furthermore, the length of the gap between two adjacent magnetic elements can correspond to the circumferential width of the magnetic element. In this case, the adjacent magnetic elements or their base plates are not adjacent. Alternatively, the length of the gap can be less than the circumferential width of the adjacent magnetic elements. Here, the adjacent magnetic elements or their base plates are only partially adjacent, rather than adjacent along the entire length of their side surfaces, thus leaving the corresponding gap open.

[0019] In a further embodiment of the alternative width, the smaller or shorter the gap, the more likely it is to provide two or more gaps between two adjacent magnet elements. Here, two or more short gaps are provided between adjacent magnet elements or base plates in a circumferential row.

[0020] The present invention further relates to an electric motor comprising a rotor as described above and a stator disposed within the rotor.

[0021] Finally, the present invention also relates to a wind turbine comprising an electric motor as mentioned above, which serves as a generator. Attached Figure Description

[0022] Other objects and features of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. However, the drawings are merely schematic diagrams, intended only for illustrative purposes and not to limit the invention. The drawings show:

[0023] Figure 1 It is a creative partial view of the rotor viewed longitudinally along the axis of rotation.

[0024] Figure 2 yes Figure 1 The principle perspective and cut view of the rotor,

[0025] Figure 3 It is a schematic diagram of an inventive motor including the inventive rotor of the first embodiment.

[0026] Figure 4 This is a schematic diagram of an inventive motor including the inventive rotor of the second embodiment.

[0027] Figure 5 It is a schematic diagram of an inventive motor including the inventive rotor of the third embodiment, and

[0028] Figure 6 It is a schematic diagram of a creative wind turbine. Detailed Implementation

[0029] Figure 1 A partial view of a rotor 1 according to the present invention is shown. The rotor 1 includes a cylindrical rotor housing 2 having an inner housing surface 3, and a plurality of magnetic devices 4, including a number of magnetic elements 5, are arranged on the inner housing surface in a row, such as... Figure 2 As shown in the diagram, the corresponding row 6 extends along the longitudinal direction of the rotor housing 2 or parallel to the rotation axis of the rotor 1.

[0030] The corresponding rows 6 are evenly distributed around the circumference of the inner housing surface 3, so that a certain number of magnetic element rows 6 are provided, which are spaced apart by the same circumferential angle, wherein when the rotor 1 rotates relative to the stator, the magnetic device 4 interacts with the stator or stator winding (not shown) to induce a current.

[0031] The rotor 1 or the inner housing surface 2 is provided with a plurality of groove-shaped recesses 7, which extend from one front surface 8 to the opposite front surface 8. All the recesses 7 (which have a rectangular cross-section in this example) are parallel to each other and parallel to the axis of rotation. They have axial openings 9 at both ends, allowing cooling air to enter or exit each recess from the front surface.

[0032] like Figure 1 and Figure 2As shown, magnet devices 4 or magnet elements 5 are arranged on the inner housing surface 3 to cover the recessed recesses 7, such that each recess 7 is a longitudinal airflow channel open at both axial ends. To secure each magnet element 5, the rotor housing 2 has corresponding recesses 10 on its inner housing surface 3, wherein the two recesses are opposite each other and axially open. A tongue-and-groove connection is implemented to secure the magnet elements 5. Each magnet element 5 includes a base plate 11 having two longitudinally extending tongues 12. A magnet 13 is attached to the base plate 11. To secure the corresponding magnet element 5 to the rotor housing 2, the tongues 12 of the base plate 11 are axially inserted into the longitudinally extending recesses 10 (e.g., ...). Figure 1 and Figure 2 As shown in the diagram, this provides a conformal fit. The magnet element 5 is pushed along the groove 10 until it reaches its final longitudinal position, where it is finally fixed. Since each row 6 includes a fixed and identical number of individual magnet elements arranged in a row, the recess 7 is radially closed on its inner side, making it effectively an airflow channel defined by the rotor housing 2 and the base plate 11. Instead of one recess 7 per row 6, it is also possible to provide two or more parallel but smaller recesses 7 per row, which are covered by the base plate 11 of the magnet elements 5 of the corresponding row 6, thus forming several parallel but smaller channels.

[0033] Figure 2 A perspective cut-out view of rotor 1 is shown, in which rotor housing 2 is cut in a plane extending radially through rotor housing 2. It shows a recessed recess 7 and a corresponding row 6 comprising a plurality of magnetic elements 5 arranged at rotor housing 2 by tongue-groove connection and covering recess 7, which, as mentioned, has axial openings 9 at both ends.

[0034] like Figure 2 As shown, the magnetic elements 5 are arranged in a row, but they are arranged such that they are not adjacent to each other with respect to their base plate 11 and magnet 13, but are spaced apart from each other, thereby creating a corresponding gap 14 between two adjacent magnetic elements 5. This gap 14 (which may also be referred to as a slit) extends in the circumferential direction and also communicates with the recess 7 because the magnetic element 5 covers the recess 7. In the illustrated embodiment, such a gap 14 is provided between each pair of magnetic elements 5. It should be noted that this is optional, and in practice, at least one such gap 14 will be implemented according to the invention.

[0035] The gap 14 not only leads to the recess 7 but also radially inward toward the stator (not shown), such that when viewed radially outward, the gap 14 communicates with the recess 7, and when viewed radially inward, the gap 14 also communicates with the gap between the rotor and the stator. Since the recess 7 has openings 9 at both axial ends, forced airflow or air circulation is possible, as air can enter the recess 7 through one or both openings 9 and flow along the recess 7 or the channel, allowing cooling of the magnet elements 5 from the base plate side, while simultaneously cooling the rotor housing 2. Since cooling air can flow through the entire recess 7, or when it enters from both sides, it can flow from both sides until it exits the recess at any gap 14, complete air cooling of all magnet elements 5, as well as complete air cooling of the magnet elements 5 located in the central region when viewed along the axis of rotation, is possible.

[0036] The width of the corresponding gap 14 is between 0.5 and 10 mm, preferably between 1 and 6 mm. If several of these gaps 14 are provided per row 6, the width of each gap 14 may be small, for example, 1 to 2 mm, while if, for example, only one gap 14 is provided, the width of the gap 14 may be larger, for example, 4 to 6 mm. Viewed circumferentially, the length of the gap in the illustrated embodiment corresponds to the width of the adjacent substrate, but may also be smaller than the substrate width up to approximately 25% of the substrate width. When the gap length is less than the substrate width, the substrates are only partially abutted along their adjacent side surfaces. Multiple gaps may also be provided between two adjacent substrates, each of which is, of course, less than the substrate width.

[0037] Preferably, each row 6 is provided with one or more of these gaps 14. If each row is provided with, for example, only one gap, then each gap 14 is positioned at the same longitudinal location, such that the airflow in each recess is the same in terms of exiting or entering through the corresponding gap 14. If each row 6 is provided with several gaps 14, then these several gaps 14 in each row 6 are also positioned at the same longitudinal location.

[0038] Figure 3 A schematic diagram of motor 15 is shown, in which only a portion of motor 15 is shown. It includes an inventive rotor 1 that surrounds an inner stator 16, which is shown only in principle. As is generally known, the stator includes corresponding stator teeth and windings (preferably, concentrated windings arranged at the stator teeth).

[0039] The rotor housing 2 also surrounds the stator 16 on the axial side, such as Figure 3 As shown, this results in radial clearances 17, which merge with the circumferential clearances 18 between the rotor 1 and the stator 16, as... Figure 3 As shown in the image.

[0040] exist Figure 3 In the embodiment shown, the cutting plane extends through the corresponding recess 7, which in Figure 3 As shown, it is covered by corresponding magnetic elements 5, wherein, in this embodiment, seven magnetic elements 5 are arranged by tongue-and-groove connections. In this embodiment, a corresponding gap 14 with a width of, for example, 1–2 mm is provided between each adjacent pair of magnetic elements. As shown, these gaps 14 communicate with the recess 7 or the channel realized through the recess 7, and with the gap 18 between the rotor 1 and the stator 16.

[0041] During operation, air is forced radially through gap 17, as indicated by arrow P1. A portion of this air then enters gap 18 between rotor 1 and stator 16, as indicated by arrow P2. A certain amount of this cooling air also enters recess 7 or channel through corresponding opening 9, as indicated by arrow P3. This cooling air flows through recess 7 and can exit recess 7 through corresponding gap 14, such that the cooling air, heated while flowing through recess 7, exits recess 7 towards stator 16 and circulates back, as indicated by arrow P4.

[0042] Clearly, all the magnet elements 5 in each row 6 can be cooled by forced air circulation through the recess 7. Cooling performance is enhanced because cooling of the magnet elements located in the central region is also possible, allowing the temperature of all the magnet elements 5 in row 6 to be controlled and maintained at a uniform or near-uniform temperature level. In particular, the magnet temperature (especially the highest temperature) in the concentrated winding generator can thus be efficiently controlled, resulting in improved generator efficiency and better performance.

[0043] Figure 4 A second embodiment of the inventive motor 15 is shown, again having a rotor 1 and a stator 16. Again here, each row includes a plurality of magnetic elements 5, which cover recesses 7 realized in the rotor housing 2. Figure 3 Unlike the first embodiment, only one gap 14 is implemented in the central region (in this embodiment, counted from left to right, between the third and fourth magnet elements 5). In this embodiment, the axial width of the gap 14 is greater than... Figure 3 The width of several gaps 14. According to Figure 4 The width of the gap 14 was measured to be, for example, 4–6 mm, while Figure 3 The width of the gap was measured to be 1–2 mm. It is evident that, counting from the left, the three magnet elements are adjacent to each other, followed by gap 14, and then the four magnet elements thereafter are again adjacent to each other.

[0044] In this embodiment, as indicated by arrow P1, air enters the radial gap 17 and then flows through the gap 18 between the rotor 1 and the stator 16 according to arrow P2. A certain amount of air also enters the recess 7 or through a channel formed by the recess 7 and the base plate 11. As indicated by arrow P3, cooling air enters the recess 7 from both sides. It flows along the recess 7 and may exit only at a single gap 14 located in the central region. The exiting air then flows to or through the stator 16, as indicated by arrow P4, and is recirculated.

[0045] exist Figure 4 In one embodiment, seven magnet elements 5 are provided, resulting in the gap 14 not being positioned in the axial center of the arrangement. Figure 5 An alternative, inventive embodiment is shown, in which eight magnet elements 5 are provided, wherein only a central gap 14 is again achieved between the fourth and fifth magnet elements 5, such that the gap 14 is exactly in the middle of the arrangement. Airflow is again as previously described. Air enters (see arrow P1) into the radial gap 17. A first volume of air enters into the gap 18 between the rotor 1 and the stator 16 (see arrow P2). A second volume of air (see arrow P3) enters into the recess 7 and flows through the recess to the central gap 14, from which it exits toward and through the stator 16, as indicated by arrow P4.

[0046] Figure 5 The diagram shows magnet elements with different axial lengths. While the first, second, third, sixth, seventh, and eighth magnet elements 5 all have the same axial length, the fourth and fifth magnet elements 5 are slightly shorter to achieve the corresponding center gap 14. It should be noted that, of course, all magnet elements 5 could have the same axial length.

[0047] Regardless of the embodiment implemented, each embodiment allows for improved temperature control, resulting in a nearly uniform temperature for the magnet elements 5 in each row 6, or a uniform temperature distribution along the row 6. This is advantageous considering the uniform magnetic properties of the magnet elements or individual magnet devices, and consequently, improves the overall performance of the motor. The overall temperature is also reduced compared to prior art arrangements.

[0048] at last, Figure 6 A wind turbine 19 is shown, comprising a tower 20 and a nacelle 21 disposed on top of the tower. An electric motor 15 according to the invention is arranged in the nacelle, which functions as a generator. The rotor 1 of the motor 15 is coupled to a hub 22 carrying rotor blades 23, which interact with the wind and cause the hub 22 to rotate. Due to the rotational coupling, the rotor 1 also rotates, thereby inducing a current in the stator windings, as is commonly known.

[0049] Although the invention has been described in detail with reference to preferred embodiments, the invention is not limited to the disclosed examples, and those skilled in the art can derive other variations from the disclosed examples without departing from the scope of the invention.

Claims

1. A rotor for an electric motor, the rotor comprising a cylindrical rotor housing (2) having a plurality of magnetic devices (4) arranged on an inner housing surface (3), characterized in that, Each magnet device (4) includes a plurality of magnet elements (5) arranged in rows (6) parallel to the axis of rotation, wherein the inner housing surface (3) is provided with at least one groove-shaped recess (7) extending parallel to the axis of rotation, wherein each recess (7) is covered by the magnet elements (5) in the row (6), and wherein at least two magnet elements (5) in at least some of the rows (6) are arranged with at least one gap (14) extending in the circumferential direction, the gap (14) communicating with the corresponding recess (7); In the longitudinal direction of the row, the width of each gap (14) is between 0.5 and 10 mm.

2. The rotor according to claim 1, characterized in that, Each recess (7) opens to the surrounding environment at one or both longitudinal ends.

3. The rotor according to claim 1 or 2, characterized in that, Viewed in the longitudinal direction, the at least one gap (14) is arranged in the central region of the row (6).

4. The rotor according to claim 1 or 2, characterized in that, More than one gap (14) is achieved in the corresponding row (6).

5. The rotor according to claim 4, characterized in that, A gap (14) is provided between each pair of magnet elements (5) in the corresponding row.

6. The rotor according to claim 1 or 2, characterized in that, At least one gap (14) is provided in each row (6).

7. The rotor according to claim 6, characterized in that, Viewed along the longitudinal direction, the gaps (14) of all rows (6) are arranged at the same longitudinal position.

8. The rotor according to claim 1 or 2, characterized in that, Each magnet element (5) includes a base plate (11) and a magnet (13) arranged on the base plate (11), wherein the rotor housing (2) is provided with grooves (10) arranged in parallel to the two longitudinal sides of each recess (7), and the base plate (11) of each row (6) is engaged in the groove (10).

9. The rotor according to claim 1 or 2, characterized in that, Each recess (7) has a rectangular cross section.

10. The rotor according to claim 1 or 2, characterized in that, Two or more parallel groove-shaped recesses (7) are provided, and the groove-shaped recesses are covered by the magnetic elements (5) in the row (6).

11. The rotor according to claim 1 or 2, characterized in that, The length of the gap (14) between two adjacent magnet elements (5) corresponds to the circumferential width of the magnet element (5), or the length of the gap (14) is less than the circumferential width of the adjacent magnet element (5).

12. The rotor according to claim 11, characterized in that, Two or more gaps (14) are provided between two adjacent magnetic elements (5).

13. The rotor according to claim 1, characterized in that, The motor is a generator for a direct-drive wind turbine (19).

14. The rotor according to claim 1, characterized in that, Looking along the longitudinal direction of the row, the width of each gap (14) is between 1 and 6 mm.

15. An electric motor comprising a rotor (1) according to any one of the preceding claims and a stator (16) disposed within the rotor (1).

16. A wind turbine comprising an electric motor (15) according to claim 15, the electric motor being used as a generator.

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