Mold and method for making flux-focusing permanent magnets comprising diffuse flux lines

Abstract

A mold for manufacturing a permanent magnet is described. The mold includes: a first mold portion including a first curved surface; a second mold portion including a second curved surface, wherein the first mold portion and the second mold portion are made of a ferromagnetic material. The mold also includes a third mold portion having a molding chamber, wherein the third mold portion is arranged between the first mold portion and the second mold portion, and wherein the first mold portion and the second mold portion are made of a different material than the third mold portion. The first curved surface and the second curved surface are formed so that magnetic flux passing through the first mold portion, the second mold portion, and the third mold portion is guided so that a diffuse magnetic flux can be generated in the molding chamber. Furthermore, a system for manufacturing such a magnet, a method for manufacturing a permanent magnet, and a permanent magnet manufactured using this method are described. Furthermore, an electromechanical transducer and a wind turbine including such a permanent magnet are described.

Description

Technical Field

[0001] The present invention relates to a mold for producing a permanent magnet. The present invention also relates to a system for producing a permanent magnet, a method for producing a permanent magnet, a permanent magnet produced using the method described, an electromechanical transducer, and a wind turbine comprising at least one such permanent magnet. Background Art

[0002] Permanent magnetic materials are used in a wide variety of applications. Perhaps the most technically and economically important application area is in electromechanical transducers, namely electric motors and generators. Electric motors, equipped with at least one permanent magnet, convert electrical energy into mechanical energy by generating a temporarily varying magnetic field via windings or coils. This temporarily varying magnetic field interacts with the magnetic field of the permanent magnet, causing, for example, the rotor assembly of the electric motor to rotate relative to the stator assembly. Generators convert mechanical energy into electrical energy in a physically complementary manner.

[0003] The generator is the core component of any power plant, used to generate electrical energy. This applies to power plants that directly capture mechanical energy, such as hydroelectric power plants, tidal power plants, and wind power plants, also known as wind turbines.

[0004] Generator efficiency is perhaps the most important factor for optimizing electrical energy production. In permanent magnet electric machines (including generators used in direct-drive wind turbines), torque / power production is determined by the air gap flux density generated by the permanent magnets. It is known that the flux density, and therefore torque, can be increased by utilizing flux-focusing permanent magnets.

[0005] Flux focusing provides a substantial increase in the air gap flux density, resulting in higher torque / power for electromechanical transducers, such as generators for direct drive wind turbines.

[0006] It is known that the air gap flux density can be increased by using magnets with a higher magnet grade. However, it is also known that there are physical and technical limitations to increasing the magnet grade of the magnets. Another commonly known way to increase the air gap flux density is to make the magnets used thicker. However, it is also known that there is a limit at which the increase reaches saturation. This is associated with increased cost because more magnetic material is required.

[0007] There may be a need to provide a mold and a method that allow permanent magnets, in particular flux focusing permanent magnets, to be manufactured in an efficient manner. Summary of the Invention

[0008] This need is met by the subject matter according to the independent claim. Advantageous embodiments of the invention are described by the dependent claims.

[0009] According to a first aspect of the present invention, a mold for manufacturing a permanent magnet, particularly a flux-focusing permanent magnet, is provided. The mold includes: (a) a first mold portion including a first curved surface having a first radius; (b) a second mold portion including a second curved surface having a second radius, wherein the first mold portion and the second mold portion are made of a ferromagnetic material. The mold also includes: (c) a third mold portion including a molding chamber, wherein the third mold portion is arranged between the first mold portion and the second mold portion. The first mold portion and the second mold portion are made of a different material than the third mold portion, and the first curved surface and the second curved surface are formed so that magnetic flux passing through the first mold portion, the second mold portion, and the third mold portion is guided so that a diffuse magnetic flux is generated in the molding chamber.

[0010] The described apparatus is based on the concept that by selecting appropriate geometries, in particular appropriate radii, of the first curved surface of the ferromagnetic first mold part and the second curved surface of the ferromagnetic second mold part, the magnetic flux in the molding chamber and, therefore, in the resulting flux-focusing permanent magnet, is a tailored diffuse magnetic flux. Consequently, flux-focusing permanent magnets with magnetic properties that enable flux focusing can be manufactured straightforwardly and cost-effectively. Furthermore, the mold according to the present invention can be placed in a magnetic field that can be provided in a generally known manner.

[0011] The ferromagnetic material used to form the first and second mold sections can be mild steel or an iron-cobalt alloy. It is understood that the first and second mold sections can also be made of different ferromagnetic materials. However, the first and second mold sections are preferably made of the same ferromagnetic material. By providing the first and second mold sections with the same ferromagnetic material, the resulting diffuse magnetic flux in the molding chamber can be precisely adjusted. However, it is understood that the first and second mold sections can be made of different ferromagnetic materials.

[0012] The mentioned first radius and second radius are different from each other. In particular, according to an exemplary embodiment of the present invention, the first radius is smaller than the second radius.

[0013] The third mold section is made of a different material than the first and second mold sections. In other words, the material of the third mold section must be different from each of the materials of the first and second mold sections. By providing a third mold section made of a different material than the first and second mold sections, the first and second curved surfaces can be sufficiently distinguished and defined.

[0014] The mentioned molding chamber is formed by the hollow space inside the third mold part. According to the present invention, the molding chamber is spaced apart from each of the restriction / outer surface of the third mold part. In other words, the molding chamber is away from each of the first mold part and the second mold part.

[0015] The mentioned diffuse magnetic flux is such that a diffuse angular distribution of the magnetic flux lines is provided in the molding chamber.

[0016] The angular distribution of the magnetic flux lines can be particularly useful for inducing a angular distribution of the magnetic flux lines within a permanent magnet block molded in a molding chamber, which can lead to focused magnetization of the flux-focusing permanent magnet block. As a result, a magnetic focusing point or at least a magnetic focusing region can be defined outside the main body of the permanent magnet block. The magnetic flux density caused by the corresponding flux-focusing permanent magnet is increased at this point or in this region compared to points or regions outside of this focusing point or region, respectively.

[0017] By designing the generator so that the focusing point or focusing region is located within the air gap between the stator assembly and the rotor assembly, respectively, the electrical power that can be generated by the generator can be significantly increased.

[0018] According to an exemplary embodiment of the present invention, the second mold portion is a semicircular portion. Additionally or alternatively, the first curved surface of the first mold portion is a semicircular surface. Thus, the first mold portion has a semicircular opening, and the third mold portion and the second mold portion are at least partially positioned in the semicircular opening.

[0019] According to an exemplary embodiment of the present invention, the third mold section includes: a third surface that is curved and has a third radius corresponding to the first radius of the first curved surface; and an additional third surface opposite the third surface, wherein the additional third surface is curved and has an additional third radius corresponding to the second radius of the second curved surface. Furthermore, the third surface of the third mold section is coupled to the first curved surface of the first mold section, and the additional third surface of the third mold section is coupled to the second curved surface of the second mold section.

[0020] By providing a third surface with a shape corresponding to the shape of the first curved surface, and a further third surface with a shape corresponding to the shape of the second curved surface, the outer shape of the third mold section can be formed to correspond to the shapes of the first and second mold sections. Therefore, during the compaction step, in which the magnetic material is compacted within the molding chamber, the compaction force applied to the magnetic material within the molding chamber can be evenly distributed because the entire space between the first and second mold sections is filled with the third mold section, and thus with the material of the third mold section. Consequently, the compaction force can be evenly distributed across the entire first and second curved surfaces.

[0021] According to a further embodiment of the present invention, the first curved surface comprises a first circle of curvature having a first center, and the second curved surface comprises a second circle of curvature having a second center, wherein a center distance between the first center and the second center is adapted such that the alignment (or density) of the diffuse magnetic flux in the molding chamber can be adjusted.

[0022] According to the present invention, the radius of the first circle of curvature corresponds to the first radius of the first curved surface, and the radius of the second circle of curvature corresponds to the second radius of the second curved surface.

[0023] The center of the first circle of curvature and the second center of the second circle of curvature are both located on the mold's axis of symmetry (also referred to as the magnetic axis), which extends through the first, second, and third mold sections. According to an exemplary embodiment of the present invention, the first center and the second center are spaced apart from each other along the axis of symmetry. In other words, a center distance is defined between the first center and the second center.

[0024] Both the first center and the second center are located on the symmetry axis inside the second portion.The first center is located closer to the second curved surface than the second center, and the second center is located farther from the second curved surface.

[0025] The center distance between the first center and the second center is adapted such that the alignment of the diffuse magnetic flux in the molding chamber can be adjusted.

[0026] In other words, by changing the center distance between the first center and the second center, the angular distribution of the magnetic flux lines can be changed, for example, by increasing or decreasing the amount of magnetic flux lines extending through the molding chamber and, therefore, by increasing or decreasing the angle between two adjacent magnetic flux lines. This allows the position of the magnetic focusing point / region of the manufactured flux-focusing permanent magnet to be moved.

[0027] Alternatively or additionally, the angular distribution of the magnetic flux lines can be altered by changing the first radius of the first circle of curvature and / or by changing the second radius of the second circle of curvature. For example, the angular distribution of the magnetic flux lines can be altered by increasing or decreasing the amount of magnetic flux lines extending through the molding chamber and, therefore, by increasing or decreasing the angle between two adjacent magnetic flux lines. This can shift the position of the magnetic focusing point / region of the manufactured flux-focusing permanent magnet.

[0028] According to an exemplary embodiment of the present invention, the center distance is changed so that the magnetic focusing point or magnetic focusing area is located on the symmetry axis together with the first center and the second center. At the same time, the magnetic focusing point is located away from the first center and the second center and is arranged outside the second mold part and at the same time outside the mold.

[0029] According to the present invention, "alignment of diffuse magnetic flux" may refer to the amount and spatial orientation of magnetic flux lines extending through the molding chamber. In other words, "alignment of diffuse magnetic flux" may refer to the angle between adjacent magnetic flux lines inside the molding chamber.

[0030] According to a further embodiment of the invention, the ratio of the first radius to the second radius is adapted such that the alignment of the diffuse magnetic flux in the molding chamber can be adjusted.

[0031] In other words, by changing the ratio of the first radius to the second radius, the angular distribution of the magnetic flux lines can be changed. This increases or decreases the amount of magnetic flux lines extending through the molding chamber, and thus increases or decreases the angle between two adjacent magnetic flux lines. This allows the position of the magnetic focusing point / region of the manufactured flux-focusing permanent magnet to be shifted.

[0032] According to an exemplary embodiment of the present invention, the magnetic focusing point or magnetic focusing area is located on the symmetry axis together with the first center and the second center. At the same time, the magnetic focusing point is far away from the first center and the second center and is arranged outside the second mold part and at the same time outside the mold.

[0033] According to the present invention, "alignment of diffuse magnetic flux" may refer to the amount and spatial orientation of magnetic flux lines extending through the molding chamber. In other words, "alignment of diffuse magnetic flux" may refer to the angle between adjacent magnetic flux lines inside the molding chamber.

[0034] According to a further embodiment of the invention, the third mould part is made of a metal having a hardness higher than 400 HV.

[0035] A hardness above 400 HV according to the present application means that the material has a hardness above 400 HV when tested by means of the Vickers hardness test.

[0036] The basic principle of the Vickers test is to observe the ability of a material to undergo plastic deformation from a standardized source. HV is the Vickers pyramidal number and is calculated from the load on the surface.

[0037] Metals with a hardness exceeding 400 HV are very hard metals. During compaction of the magnetic material within the molding chamber, high loads act on the third mold section. Therefore, forming the third mold section from a metal with a hardness exceeding 400 HV can minimize wear on the third mold section.

[0038] Specifically, the material of the third mold section has a magnetic polarization density of less than 0.6 T (Tesla). The magnetic polarization density characterizes the magnetic state of a material and is calculated as the volume magnetic moment. In other words, the magnetic polarization density describes the density of permanent magnetic dipole moments in a magnetic material.

[0039] Forming the third mould part from a metal having a magnetic polarisation intensity of less than 0.6 T may have the advantage that magnetisation of the third mould part may be minimised during magnetisation of the permanent magnet material contained inside the moulding chamber.

[0040] According to another embodiment of the present invention, the molding chamber includes: a first side surface facing the first curved surface of the first mold section; and a second side surface opposite the first side surface. Furthermore, the molding chamber is positioned in the third mold section such that each of two opposing corners of the first side surface positioned closest to the first curved surface of the first mold section is located within a range of 4 mm to 10 mm from the first curved surface, and / or such that a position of the second side surface positioned closest to the second curved surface of the second mold section is located within a range of 4 mm to 10 mm from the second curved surface of the second mold section.

[0041] The first side surface of the molding chamber is bounded by multiple (preferably four) side edges and multiple corners (particularly four corners). The molding chamber is disposed in the third mold portion, and the first side surface of the molding chamber is positioned adjacent to the first curved surface. Both of the multiple corners positioned closest to the first curved surface are positioned away from the first curved surface. The distance between a point on the first curved surface and the corresponding corner is measured and is within a range of 4 mm to 10 mm. This prevents mold damage and poor electrical conductivity.

[0042] The second side surface of the molding chamber can be spatially shaped. Advantageously, the second side surface is curved. The portion of the second side surface closest to the second curved surface of the second mold portion is spaced apart from the second curved surface by a distance in the range of 4 mm to 10 mm. This prevents mold damage and poor electrical conductivity.

[0043] By providing all three above-defined distances within the range of 4 mm to 10 mm, mold damage and poor electrical conductivity as well as leakage can be even better prevented.

[0044] According to another embodiment of the present invention, the molding chamber includes a first side surface facing the first curved surface of the first mold part; and a second side surface opposite the first side surface. The first side surface is a first curved side surface, and / or the second side surface is a second curved side surface. Furthermore, the first curved side surface and / or the second curved side surface are designed to at least partially compensate for shrinkage of a sintered mass obtained by magnetizing, compacting, and sintering a powder that may be provided in the molding chamber.

[0045] According to the present invention, preferably, the first side surface and the second side surface are curved. Thus, the molding chamber is provided with two curved side surfaces, which will compensate for the shrinkage effect after sintering and reduce the machining of the final magnet block.

[0046] According to an exemplary embodiment of the present invention, the first side surface and the second side surface are curved such that the first side surface is convex and the second side surface is concave as viewed from the inside of the molding chamber.

[0047] According to the present invention, the first and / or second curved side surfaces are designed to at least partially compensate for the shrinkage of the sintered mass obtained by compacting and sintering the magnetic powder that may be provided in the molding chamber. In other words, by means of a suitably shaped molding chamber that differs from the shape of the final flux-focusing permanent magnet, it is possible to pre-compute and compensate for the undesirable deformation effects typically caused by shrinkage during sintering. This offers the advantage that both expected and undesired deformations can be largely compensated. This applies in particular to shrinkage effects that occur as the sintered permanent magnet cools.

[0048] According to another aspect of the present invention, a system for manufacturing permanent magnets, particularly flux-focusing permanent magnets, is provided. The system includes (a) a mold. The mold includes: a first mold portion including a first curved surface having a first radius; and a second mold portion including a second curved surface having a second radius, wherein the first mold portion and the second mold portion are made of a ferromagnetic material. The mold also includes a third mold portion having a molding chamber, wherein the third mold portion is disposed between the first mold portion and the second mold portion, and wherein the first mold portion and the second mold portion are made of a different material than the third mold portion. The system also includes: (b) a first magnetic device positioned adjacent to the first mold portion; and (c) a second magnetic device positioned adjacent to the second mold portion, wherein a linear magnetic field between the first and second magnetic devices can be generated by the first and second magnetic devices, and wherein the first and second curved surfaces are formed such that magnetic flux passing through the first, second, and third mold portions is directed to generate a diffuse magnetic flux in the molding chamber.

[0049] The described system is also based on the idea that permanent magnets, in particular flux-focusing permanent magnets, having magnetic properties enabling flux focusing can be produced directly and cost-effectively in the described system.

[0050] With respect to the moulding chamber, the first magnetic device and the second magnetic device are located at opposite sides. Additionally, both the first magnetic device and the second magnetic device (they are called alignment coils) are positioned outside the mould.

[0051] The first magnetic device and the second magnetic device are configured to provide a linear magnetic field between the first magnetic device and the second magnetic device. The first magnetic device or the second magnetic device may be a magnetic coil. In particular, the first magnetic device may be configured as a north pole, and the second magnetic device may be a south pole. It is understood that the first magnetic device may be configured as a south pole, and the second magnetic device may be configured as a north pole.

[0052] By providing the above mold between the first magnetic device and the second magnetic device, the first curved surface and the second curved surface are formed so that the magnetic flux passing through the first mold part, the second mold part and the third mold part is guided so that a diffuse magnetic flux can be generated in the molding chamber.

[0053] According to another aspect of the present invention, a method for manufacturing a permanent magnet, particularly a flux-focusing permanent magnet, is provided. The method includes (a) providing a mold. The mold includes: a first mold portion including a first curved surface having a first radius; a second mold portion including a second curved surface having a second radius; and a third mold portion having a molding chamber, wherein the third mold portion is disposed between the first mold portion and the second mold portion. The first mold portion and the second mold portion are made of a different material than the third mold portion, and wherein the first curved surface and the second curved surface are formed such that magnetic flux passing through the first mold portion, the second mold portion, and the third mold portion is directed to generate diffuse magnetic flux in the molding chamber. The method also includes: (b) placing powder of a magnetic material into the molding chamber; (c) generating a magnetic field for aligning the powder contained in the molding chamber, wherein the magnetic field includes diffuse magnetic flux in the molding chamber; and (d) compacting the powder contained in the molding chamber in the magnetic field, wherein the magnetization and compaction result in a magnetized compacted mass of the powder having diffuse magnetic flux lines. The method then further comprises: (e) sintering and aging the non-magnetized, merely magnetically aligned compact of the powder.

[0054] The described method is also based on the idea that flux-focusing permanent magnets having magnetic properties enabling flux focusing can be manufactured directly and cost-effectively in the described system.

[0055] Typically, step (c) of generating a magnetic field in order to obtain magnetic alignment and step (d) of compacting the powder are at least partially performed simultaneously.

[0056] Powder of magnetic material is placed in a molding chamber and a magnetic field is applied. The applied magnetic field is adjusted so that the magnetic polarization intensity of the magnetic field inside the molding chamber is in the range of 0.8 T to 1.6 T.

[0057] The magnetic powder contained in the molding chamber is compacted in a magnetic field to a density of 3.7 g / cm 3 to 4.3 g / cm3 density.

[0058] In subsequent steps, the resulting flux focusing permanent magnet block is sintered and aged. Afterwards, the shape of the permanent magnet block is appropriately shaped according to desired requirements, and the alignment direction of the magnetic particles of the flux focusing permanent magnet block is diffused or in other words radial.

[0059] According to another embodiment of the present invention, the compacting may be isostatic pressing.

[0060] According to an embodiment of the invention, the powder contains a rare earth material, in particular NdFeB (neodymium iron boron). This may provide the advantage that very strong permanent magnets may be manufactured with the desired permanent magnet geometry and flux focusing properties.

[0061] In this respect it should be mentioned that other compositions of the permanent magnet material may include ferrite and / or SmCo (Samarium Cobalt).

[0062] According to a further aspect of the present invention, there is provided a permanent magnet, in particular a flux focusing permanent magnet, which is produced by implementing the method as described above.

[0063] According to another aspect of the present invention, an electromechanical transducer, in particular a generator, is provided. The electromechanical transducer comprises (a) a stator assembly and (b) a rotor assembly. The rotor assembly comprises a support structure and at least one flux-focusing permanent magnet as described above.

[0064] The provided electromechanical transducer is based on the idea that it can be built with a rotor assembly comprising straightforward and cost-effectively manufactured flux-focusing permanent magnets having magnetic properties that enable flux focusing.

[0065] According to another aspect of the present invention, a wind turbine for generating electrical power is provided. The provided wind turbine includes: (a) a tower; (b) a wind rotor disposed at a top portion of the tower and including at least one blade; and (c) an electromechanical transducer as described above. The electromechanical transducer is mechanically coupled to the wind rotor.

[0066] The proposed wind turbine (also designated as a wind energy device) is based on the concept that the electromechanical transducer described above allows for a cost-effective implementation of the wind turbine with respect to the flux-focusing permanent magnets used. This can help to increase the attractiveness of wind turbine technology for renewable electricity production compared to other technologies such as solar power plants.

[0067] It should be noted that embodiments of the present invention have been described with reference to different subject matter. In particular, some embodiments have been described with reference to method-type claims, while other embodiments have been described with reference to apparatus-type claims. However, a person skilled in the art will infer from the above and following descriptions that, unless otherwise indicated, any combination of features relating to different subject matter (particularly between features of method-type claims and features of apparatus-type claims) is also considered to be disclosed with this document, in addition to any combination of features belonging to one type of subject matter.

[0068] The aspects defined above and further aspects of the invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to the examples of embodiment.The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 A wind turbine according to an embodiment of the invention is shown.

[0070] Figure 2 The schematic diagram shows Figure 1 generators of wind turbines.

[0071] Figure 3 A flux focusing permanent magnet produced according to an embodiment of the present invention is shown.

[0072] Figure 4 Another flux focusing permanent magnet produced according to an embodiment of the present invention is shown.

[0073] Figure 5 Another flux focusing permanent magnet produced according to an embodiment of the present invention is shown.

[0074] Figure 6 A mold for manufacturing a flux focusing permanent magnet according to an embodiment of the present invention is shown.

[0075] Figure 7 A magnetic field generating structure is shown together with a mold for manufacturing a flux focusing permanent magnet according to an embodiment of the present invention. DETAILED DESCRIPTION

[0076] The illustrations in the drawings are schematic. It should be noted that in different drawings, similar or identical elements or features are provided with the same reference numerals or reference numerals that differ from the corresponding reference numerals only within the first digit. To avoid unnecessary repetition, elements or features that have already been explained with respect to previously described embodiments are not explained again at a later point in the description.

[0077] Figure 1A wind turbine 100 according to an embodiment of the present invention is shown. Wind turbine 100 includes a tower 120 mounted on a foundation (not depicted). A nacelle 122 is arranged atop tower 120. A yaw angle adjustment device 121 is provided between tower 120 and nacelle 122. This yaw angle adjustment device enables nacelle 122 to rotate about a vertical axis (not depicted) aligned with the longitudinal extension of tower 120. By appropriately controlling yaw angle adjustment device 121, it is possible to ensure that nacelle 122 is always correctly aligned with the prevailing wind direction during normal operation of wind turbine 100.

[0078] The wind turbine 100 further includes a rotor 110 having three blades 114. Figure 1 In the perspective view of FIG, only two blades 114 are visible. The wind wheel 110 is rotatable about an axis of rotation 110a. The blades 114 mounted on the hub 112 extend radially relative to the axis of rotation 110a.

[0079] A blade angle adjustment device 116 is provided between the hub 112 and the blades 114, respectively, to adjust the blade pitch angle of each blade 114 by rotating the corresponding blade 114 about an axis (not depicted), which is aligned substantially parallel to the longitudinal extension of the corresponding blade 114. By controlling the blade angle adjustment device 116, the blade pitch angle of the corresponding blade 114 is adjusted so that, at least when the wind is not too strong, maximum wind energy can be recovered from the available mechanical power of the wind driving the wind rotor 110.

[0080] As from Figure 1 As can be seen in FIG, a gearbox 124 is arranged in the nacelle 122. The gearbox 124 is used to convert the number of revolutions of the rotor 110 into a higher number of revolutions of a shaft 125 which is coupled to an electromechanical transducer 130 in a known manner. The electromechanical transducer is a generator 130.

[0081] It should be noted at this point that the gearbox 124 is optional and the generator 140 can also be coupled directly to the rotor 110 via the shaft 125 without changing the number of rotations. In this case, the wind turbine is a so-called direct drive (DD) wind turbine.

[0082] Furthermore, a brake 126 is provided in order to stop the operation of the wind turbine 100 or in order to reduce the rotation speed of the rotor 110, eg in an emergency situation.

[0083] The wind turbine 100 further comprises a control system 143 for operating the wind turbine 100 in an efficient manner. In addition to controlling eg the yaw angle adjustment device 121, the depicted control system 153 is also used for adjusting the blade pitch angles of the rotor blades 114 in an optimized manner.

[0084] According to the basic principles of electrical engineering, generator 130 includes a stator assembly 135 and a rotor assembly 140. In the embodiment described herein, generator 130 is implemented in a so-called "inner stator-outer rotor" configuration, wherein rotor assembly 140 surrounds stator assembly 135. This means that the non-depicted permanent magnets or magnet assembly of rotor assembly 140 travel around an arrangement of multiple non-depicted coils of inner stator assembly 135, which generate an induced current resulting from the time-varying magnetic flux picked up from the traveling permanent magnets.

[0085] According to the embodiments described here, each permanent magnet assembly comprises at least three flux-focusing permanent magnet arrangements, which are in particular made of a NdFeB material composition.

[0086] Figure 2 A schematic diagram of a generator 130 is shown in cross-section. The generator 130 includes a stator assembly 135. The stator assembly 135 includes a stator support structure 237 comprising a stack of a plurality of laminations and a plurality of stator windings 239 housed within the stator support structure 237. The windings 239 are interconnected in a known manner by means of electrical connections, not depicted.

[0087] The rotor assembly 140 of the generator 130, which is separated from the stator assembly 135 by an air gap designated by the reference numerals ag, includes a rotor support structure 242 that provides a mechanical base for mounting a plurality of flux focusing magnet segments 250. Figure 2 , the rotational axis 110a of the rotor assembly 140 is designated by reference numeral 230a.

[0088] In the exemplary embodiment described here, three flux focusing permanent magnets are arranged at each angular position of the rotor assembly 140, which are arranged in close proximity to each other. Figure 2 , for ease of illustration, only three flux-focusing segments 250 of a permanent magnet are depicted assigned to one angular position. In practice, depending on the size of the generator 130, multiple flux-focusing magnet segments 250 are mounted to the rotor support structure 242. These flux-focusing magnet segments 250 are preferably arranged in a matrix-like structure around a curved surface area of ​​the support structure 242, which has a substantially cylindrical geometry around the generator axis 240a.

[0089] As from Figure 2As can be seen in FIG, the flux-focusing magnet segment 250 is not mounted directly to the rotor support structure 242. Instead, a back plate 244 made of a ferromagnetic material (e.g., iron) is provided. The back plate is provided to ensure proper guidance of the magnetic flux. This significantly reduces the strength of the stray magnetic field in a beneficial manner.

[0090] Figure 3 A flux-focusing permanent magnet 350 is shown that is manufactured by using a mold according to an embodiment of the present invention and by a method according to an embodiment of the present invention.

[0091] The flux-focusing permanent magnet 350 is magnetized to provide a diffuse angular distribution of magnetic flux lines 352. According to the embodiments described herein, each magnetic flux line 352 follows a straight magnetization line. The straight magnetization lines are angled or tilted relative to each other in a fan-like manner. In other words, the straight magnetization lines are diffused. Specifically, the diffuse angular distribution of the straight magnetization lines creates a focal point 354 in the area above the main surface 351 of the flux-focusing permanent magnet 350, which is characterized by a local maximum in the magnetic field or flux density generated by the flux-focusing permanent magnet 350.

[0092] According to the exemplary embodiment described herein, the depicted magnetic flux line pattern is symmetrical about an axis of symmetry 349. In this document, the axis of symmetry 349 is also designated as the magnetic axis. The magnetic axis 349 is the normal axis of the major surface 351 and extends through the focal point 354.

[0093] like Figure 3 As depicted, the major surface 351 is planar and Figure 3 In the cross-sectional view of FIG, the flux focusing permanent magnet 350 is rectangular. Therefore, Figure 3 The flux-focusing permanent magnet 350 shown in FIG. 3 is a rectangular parallelepiped in a three-dimensional view.

[0094] Figure 4 A flux-focusing permanent magnet 450 is shown that is manufactured by using a mold according to an embodiment of the present invention and by a method according to an embodiment of the present invention.

[0095] The flux-focusing permanent magnet 450 is pre-magnetized to provide a diffuse angular distribution of magnetic flux lines 452. According to the embodiments described herein, each magnetic flux line 452 follows a straight magnetization line. The straight magnetization lines are angled or tilted relative to each other in a fan-like manner. In other words, the straight magnetization lines are diffused. Specifically, the diffuse angular distribution of the straight magnetization lines creates a focal point 454 in the area above the main surface 451 of the flux-focusing permanent magnet 450, which is characterized by a local maximum in the magnetic field or flux density generated by the flux-focusing permanent magnet 450.

[0096] like Figure 4 As depicted in FIG, the major surface 451 is curved or arcuate and is Figure 4 In the cross-sectional view of FIG, the flux focusing permanent magnet 350 is shaped like a rectangle having one curved main surface 451. Therefore, Figure 4 The flux focusing permanent magnet 450 shown in FIG. 4 is shaped like a slice of bread in a three-dimensional view.

[0097] Figure 5 A flux-focusing permanent magnet 550 is shown that is manufactured by using a mold according to an embodiment of the present invention and by a method according to an embodiment of the present invention.

[0098] The flux-focusing permanent magnet 550 is magnetized to provide a diffuse angular distribution of magnetic flux lines 552. According to the embodiments described herein, each magnetic flux line 552 follows a straight magnetization line. The straight magnetization lines are angled or tilted relative to each other in a fan-like manner. In other words, the straight magnetization lines are diffused. Specifically, the diffuse angular distribution of the straight magnetization lines creates a focal point 554 in an area above the main surface 555 of the flux-focusing permanent magnet 550, which is characterized by a local maximum in the magnetic field or flux density generated by the flux-focusing permanent magnet 550.

[0099] like Figure 5 As depicted in FIG, the main surface 555 is shaped. In particular, the main surface 555 includes three subsections. These three subsections are two additionally inclined curved subsections 556, and a planar subsection 557. Each of the two curved subsections 556 interconnects one side surface 558 of the flux-focusing permanent magnet 550 with the planar subsection 557. Additionally, the planar subsection 557 is parallel to another main surface 559 that delimits the flux-focusing permanent magnet 550 on the opposite side relative to the main surface 555. The planar subsection 557 also intersects the magnetic axis 549, and the main surface 555 is symmetrical about the magnetic axis 549. Furthermore, the flux-focusing permanent magnet 550 is symmetrical about the symmetry axis 549.

[0100] Figure 6 A mold 660 for manufacturing the flux focusing magnet segment 250 is shown in accordance with an embodiment of the present invention.

[0101] Mold 660 includes a first mold portion 661, a second mold portion 662, and a third mold portion 663. Third mold portion 663 includes a molding chamber 664 located inside third mold portion 663. Therefore, molding chamber 664 is located inside third mold portion 663 such that each of the four sides of molding chamber 664 is away from first mold portion 661 and second mold portion 662, respectively.

[0102] The molding chamber 664 includes four side surfaces, specifically a first side surface 665, a second side surface 667, a third side surface 668, and a fourth side surface 669. The first side surface 665 and the second side surface 667 are curved.

[0103] First mold portion 661 includes a first curved surface 681 having a first radius 671, and second mold portion 662 includes a second curved surface 682 having a second radius 672. Third mold portion 663 includes a third (curved) surface 683 having a third radius corresponding to first radius 671, and an additional third (curved) surface 684 having an additional third radius corresponding to second radius 672. Third surface 683 is opposite to additional third surface 684.

[0104] As in Figure 6 , the third surface 683 is coupled to the first surface 681, and the further third surface 684 is coupled to the second surface 682. Thus, the first surface 681 and the third surface 683 are shaped correspondingly to each other, and the second surface 682 and the further third surface 684 are shaped correspondingly to each other.

[0105] First surface 681 includes a first circle of curvature having a first center 685, and second surface 682 includes a second circle of curvature having a second center 686. A center distance 687 is provided between first center 685 and second center 686. Center distance 687 causes the first and second circles of curvature to be non-concentric. Thus, first center 685 is positioned away from second center 686 by center distance 687. Second center 686 is positioned on magnetic axis 649 and on a surface of second mold portion 662 opposite second curved surface 682. First center 685 is also positioned on axis of symmetry 649 and within second mold portion 662.

[0106] The width 689 of the molding chamber 664 is greater than twice the second radius 672. In addition, the center distance 687 is greater than 10 mm.

[0107] Figure 7 Illustrated is a system 790 for fabricating a flux focusing magnet segment 250 in accordance with an embodiment of the present invention.

[0108] System 790 includes reference Figure 6 The mold 760 is described in detail. The system 790 further includes a first magnetic device 791 configured as a north pole and a second magnetic device 792 configured as a south pole. It is understood that the first magnetic device 791 can also be configured as a south pole, and the second magnetic device 792 can also be configured as a north pole.

[0109] The magnetic flux passing through the first mold portion 761, the second mold portion 762, and the third mold portion 763 is directed such that the magnetic flux lines 752 are diffused or aligned in a fan-like manner in the molding chamber 764. The magnetic flux lines 752 in the molding chamber 764 are diffused.

[0110] Specifically, the divergent angular distribution of the linear magnetization lines 752 creates a focal point / region 754 in the area below the second mold portion 762 that is characterized by a local maximum in the magnetic field or flux density.

[0111] According to the exemplary embodiments described herein, the depicted magnetic flux line pattern is symmetrical about an axis of symmetry 749. Magnetic axis 749 is a normal axis to major surface 792a of second magnetic device 792 and major surface 791a of first magnetic device 791. Additionally, magnetic axis 749 extends through focal point 754.

[0112] 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. Elements described in connection with different embodiments may also be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

1. A mold (660, 760) for manufacturing a permanent magnet (350, 450, 550), the mold (660, 760) comprising: a first mold portion (661) comprising a first curved surface (681) having a first radius (671); a second mold portion (662) including a second curved surface (682) having a second radius (672); wherein the first mold part (661) and the second mold part (662) are made of ferromagnetic material, and a third mold section (663) having a molding chamber (664); wherein the third mold part (663) is arranged between the first mold part (661) and the second mold part (662); wherein the molding chamber is formed by a hollow space inside the third mold portion and is spaced apart from each of the limiting portions / outer surfaces of the third mold portion, and the molding chamber includes: a first side surface (665) facing the first curved surface (681) of the first mold portion (661); and a second side surface (667) opposite to the first side surface (665); and wherein the first mold portion (661) and the second mold portion (662) are made of a different material than the third mold portion (663); wherein the first curved surface (681) and the second curved surface (682) are formed so that the magnetic flux passing through the first mold portion (661), the second mold portion (662) and the third mold portion (663) is guided so as to generate a diffuse magnetic flux in the molding chamber (664), wherein the first side surface (665) is a first curved side surface, and / or the second side surface (667) is a second curved side surface; Therein, the first curved side surface and / or the second curved side surface are designed so as to at least partially compensate for the shrinkage of a sintered mass that has been obtained by compacting a powder that can be provided in the molding chamber (664).

2. The mold (660, 760) according to claim 1, in, The third mold portion (663) includes: a third surface (683) that is curved and has a third radius corresponding to the first radius (671) of the first curved surface (681); and a further third surface (684) opposite to the third surface (683); wherein the further third surface (684) is curved and has a further third radius corresponding to the second radius (672) of the second curved surface (682); wherein the third surface (683) of the third mold part (663) is connected to the first curved surface (681) of the first mold part (661), and the further third surface (684) of the third mold part (663) is connected to the second curved surface (682) of the second mold part (662).

3. The mold (660, 760) according to claim 1 or 2, in, The first curved surface (681) includes a first circle of curvature having a first center (685); wherein the second curved surface (682) includes a second circle of curvature having a second center (686); wherein a center distance (687) between the first center (685) and the second center (686) is adapted to enable adjustment of the alignment of the diffuse magnetic flux in the molding chamber (664).

4. The mold (660, 760) according to claim 1 or 2, in, The ratio of the first radius (671) to the second radius (672) is adapted so that the alignment of the diffuse magnetic flux in the molding chamber (664) can be adjusted.

5. The mold (660, 760) according to claim 1 or 2, in, The third mold part (663) is made of a metal having a hardness higher than 400 HV.

6. The mold (660, 760) according to claim 1 or 2, in, The molding chamber (664) is positioned in the third mold part (663), such that each of two opposite corners of the first side surface (665) positioned closest to the first curved surface (681) of the first mold portion (661) is at a distance from the first curved surface (681) in the range of 4 mm to 10 mm, and / or The second side surface (667) is positioned so that the distance from the position closest to the second curved surface (682) of the second mold part (662) to the second curved surface (682) of the second mold part (662) is in the range of 4 mm to 10 mm.

7. The mold (660, 760) of claim 1, wherein the permanent magnet is a flux focusing permanent magnet (350, 450, 550).

8. The mold (660, 760) according to claim 7, in, Undesirable deformation effects, which usually result from shrinkage during sintering, can be compensated by means of a suitably shaped mold chamber which differs from the shape of the finally produced flux-focusing permanent magnet by means of preliminary calculations.

9. A system (790) for manufacturing a permanent magnet (350, 450, 550), the system (790) comprising: The mold (660, 760) according to any one of claims 1 to 8, Wherein, the system (790) further comprises: a first magnetic device (791) positioned adjacent to the first mold portion (661); and a second magnetic device (792) positioned adjacent to the second mold portion (662); wherein a linear magnetic field between the first magnetic device (791) and the second magnetic device (792) can be generated by the first magnetic device (791) and the second magnetic device (792); Wherein, the first curved surface (681) and the second curved surface (682) are formed so that the magnetic flux passing through the first mold part (661), the second mold part (662) and the third mold part (663) is guided so that a diffuse magnetic flux can be generated in the molding chamber (664).

10. The system (790) for manufacturing a permanent magnet (350, 450, 550) according to claim 9, wherein: The permanent magnet is a flux focusing permanent magnet (350, 450, 550).

11. A method for manufacturing a permanent magnet (350, 450, 550), the method comprising: Providing a mold (660, 760) according to any one of claims 1 to 8, The method further comprises: placing powder of magnetic material into the molding chamber (664); generating a magnetic field for aligning the powder contained within the molding chamber (664), wherein the magnetic field includes the diffuse magnetic flux in the molding chamber (664); compacting the powder contained in the molding chamber (664) in the magnetic field; said aligning and compacting resulting in an aligned, compacted mass of said powder having diffuse magnetic flux lines; Thereafter, the aligned compacted blocks of the powders are sintered and aged.

12. The method according to claim 11, in, The powder includes a rare earth material.

13. The method according to claim 12, wherein: The rare earth material is NdFeB.

14. The method according to any one of claims 11 to 13, wherein The permanent magnet is a flux focusing permanent magnet (350, 450, 550).

15. A permanent magnet (350, 450, 550), wherein: The permanent magnet is produced by carrying out the method according to claim 11 or 12 .

16. The permanent magnet (350, 450, 550) according to claim 15, wherein the permanent magnet (350, 450, 550) is a flux focusing permanent magnet (350, 450, 550).

17. An electromechanical transducer (130), comprising: a stator assembly (135), and A rotor assembly (140) comprising: Support structures, and At least one permanent magnet (350, 450, 550) according to claim 15, wherein the permanent magnet (350, 450, 550) is mounted to the support structure.

18. The electromechanical transducer (130) according to claim 17, wherein The electromechanical transducer (130) is a generator.

19. A wind turbine (100) for generating electrical power, the wind turbine (100) comprising: Tower (120), a wind rotor (110) arranged at a top portion of the tower (120) and comprising at least one blade (114), and The electromechanical transducer according to claim 17, wherein the electromechanical transducer (130) is mechanically coupled to the wind wheel (110).

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