CN112421805A

CN112421805A - Mold and method for manufacturing flux-focusing permanent magnet including diffused flux lines

Info

Publication number: CN112421805A
Application number: CN201910769774.3A
Authority: CN
Inventors: Z.阿扎; H-J.托加德; A.C.乌尔达; D.易
Original assignee: Siemens Gamesa Renewable Energy AS
Current assignee: Siemens Gamesa Renewable Energy AS
Priority date: 2019-08-20
Filing date: 2019-08-20
Publication date: 2021-02-26
Also published as: WO2019238981A3; WO2019238981A2

Abstract

A mold for manufacturing a permanent magnet is described. The mold comprises: a first mold portion comprising a first curved surface; a second mold portion comprising a second curved surface, wherein the first mold portion and the second mold portion are made of a ferromagnetic material. The mold further 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 different materials relative to the third mold portion. The first and second curved surfaces are formed such that magnetic flux passing through the first, second and third mold portions is directed such that a diffuse magnetic flux may be generated in the molding chamber. Furthermore, a system for manufacturing such a magnet, a method for manufacturing a permanent magnet, a permanent magnet which has been manufactured with such a method are described. Furthermore, an electromechanical transducer and a wind turbine comprising such a permanent magnet are described.

Description

Mold and method for manufacturing flux-focusing permanent magnet including diffused flux lines

Technical Field

The present invention relates to a mold for manufacturing a permanent magnet. Furthermore, the invention relates to a system for manufacturing a permanent magnet, a method for manufacturing a permanent magnet, a permanent magnet manufactured with the described method, and an electromechanical transducer as well as a wind turbine comprising at least one such permanent magnet.

Background

Permanent magnetic materials are used in a number of different fields of application. Perhaps the most technically and economically important application areas are electromechanical transducers, i.e. electric motors and generators. An electric motor equipped with at least one permanent magnet converts electrical energy into mechanical energy by generating a temporarily varying magnetic field by means of windings or coils. This temporarily varying magnetic field interacts with the magnetic field of the permanent magnets, causing for example a rotational movement of a rotor assembly of the electric motor relative to a stator assembly of the electric motor. In a physically complementary manner, the generator converts mechanical energy into electrical energy.

A generator is a core component of any power plant for the production of electrical energy. This applies to power plants that capture mechanical energy directly, such as hydroelectric power plants, tidal power plants and wind power plants, also named wind turbines.

The efficiency of the generator is probably the most important factor for optimizing the production of electrical energy. In permanent magnet electrical machines (including generators for direct drive wind turbines), torque/power generation is determined by the air gap flux density produced by the permanent magnets. It is known to increase the magnetic flux and thus the torque by using flux-focusing permanent magnets.

Flux focusing provides a substantial increase in air gap flux density, resulting in higher torque/power of an electromechanical transducer (such as a generator for a direct drive wind turbine).

It is known that the air gap flux density can be increased by using magnets with higher magnet grades. However, it is also known that there are physical and technical limitations to increasing the magnet grade of a magnet. Another generally 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 in which the increase becomes saturated. This is associated with increased costs, since more magnetic material is required.

There may be a need to provide a mould and a method which allow permanent magnets, in particular flux-focusing permanent magnets, to be manufactured in an efficient manner.

Disclosure of Invention

This need may be met by the subject matter according to the independent claims. Advantageous embodiments of the invention are described by the dependent claims.

According to a first aspect of the invention, a mold for manufacturing a permanent magnet, in particular a flux-focusing permanent magnet, is provided. The mold comprises: (a) a first mold portion comprising a first curved surface having a first radius; (b) a second mold portion comprising 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 mould still includes: (c) 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 and second mold portions are made of a different material relative to the third mold portion, and the first and second curved surfaces are formed such that magnetic flux passing through the first, second, and third mold portions is directed such that a diffuse magnetic flux may be generated in the molding chamber.

The described device is based on the following idea: by choosing an appropriate geometry, in particular an appropriate radius, of the first curved surface of the ferromagnetic first mould part and of the second curved surface of the ferromagnetic second mould part, the magnetic flux in the moulding chamber and thus in the resulting flux-focusing permanent magnet is an adapted diffused magnetic flux. Therefore, a flux focusing type permanent magnet having magnetic properties that achieve flux focusing can be directly and cost-effectively manufactured. Additionally, the mold according to the invention may be placed in a magnetic field which may be provided in a generally known manner.

The mentioned ferromagnetic material forming the first and second mould parts may be a low carbon steel or an iron cobalt alloy. It will be appreciated that the first and second mould parts may also be made of different ferromagnetic materials. However, the first and second mould parts are preferably made of the same ferromagnetic material. By providing the first and second mold portions made of the same ferromagnetic material, the resulting diffused magnetic flux in the molding chamber can be precisely adjusted. However, it will be appreciated that the first and second mould parts may be made of different ferromagnetic materials.

The first and second radii mentioned 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.

The mentioned third mould part is made of a different material than the first and second mould parts. In other words, the material of the third mold portion must be a different material than each of the materials of the first and second mold portions. By providing a third mould part made of a different material than the first and second mould parts, the first and second curved surfaces can be sufficiently distinguished and defined.

The mentioned molding chamber is formed by a hollow space inside the third mold part. According to the invention, the moulding chamber is spaced apart from each of the restrictions/outer surfaces of the third mould part. In other words, the molding chamber is remote from each of the first mold portion and the second mold portion.

The mentioned diffusing magnetic flux is such as to provide a diffusing angular distribution of the flux lines in the molding chamber.

The angular spread of the flux lines may be particularly useful for inducing an angular spread of flux lines within a permanent magnet block molded in the molding chamber, which may result in focused magnetization of the flux-focused permanent magnet block. Thereby, outside the body of the permanent magnet block, a magnetic focusing point or at least a magnetic focusing area may be defined. The magnetic flux density caused by the respective flux-focusing permanent magnet is increased in this point or in this region compared to a point or region outside this focus point or focus region, respectively.

By designing the generator such that the focal point or area is located within the air gap between the stator and rotor assemblies, respectively, the electrical power that can be generated by the generator can be significantly increased.

According to an exemplary embodiment of the invention, the second mould part is a semicircular part. Additionally or alternatively, the first curved surface of the first mold portion is a semicircular surface. Thus, the first mould part has a semi-circular opening in which the third mould part and the second mould part are at least partially placed.

According to an exemplary embodiment of the invention, the third mould part comprises: a third surface that is curved and has a third radius corresponding to the first radius of the first curved surface; and a further third surface opposite the third surface, wherein the further third surface is curved and has a further third radius corresponding to the second radius of the second curved surface. Further, a third surface of the third mold portion is coupled to the first curved surface of the first mold portion, and another third surface of the third mold portion is coupled to the second curved surface of the second mold portion.

By providing a shape of the third surface corresponding to the shape of the first curved surface and a shape of the further third surface corresponding to the second curved surface, an outer shape of the third mould part corresponding to the shape of the first mould part and the second mould part may be formed. Thus, during the compaction step, in which the magnetic material is compacted inside the moulding chamber, the compaction force applicable to the magnetic material inside the moulding chamber may be evenly distributed, since the entire space between the first and second mould parts is filled with the third mould part and thus with the material of the third mould part. Thus, the compaction force may be evenly distributed over the entire first curved surface and the entire second curved surface.

According to a further embodiment of the 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 an alignment (or density) of the diffusing magnetic flux in the molding chamber can be adjusted.

According to the invention, the radius of the first circle of curvature corresponds to a first radius of the first curved surface and the radius of the second circle of curvature corresponds to a second radius of the second curved surface.

The center of the first circle of curvature and the second center of the second circle of curvature are both located on a symmetry axis (also denoted as the magnetic axis) of the mold that extends through the first, second, and third mold portions. According to an exemplary embodiment of the invention, the first center and the second center are distant from each other along the symmetry axis. In other words, a center distance is given between the first center and the second center.

Both the first center and the second center are located on the symmetry axis inside the second portion. The first center is positioned at a position closer to the second curved surface than the second center, and the second center is positioned at a position farther from the second curved surface.

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

In other words, by varying the centre distance between the first centre and the second centre, the angular spread of the flux lines may be varied, for example by increasing/decreasing the amount of flux lines extending through the mould chamber and thus by increasing/decreasing the angle between two adjacent flux lines. Thereby, the position of the magnetic focusing point/region of the manufactured flux focusing permanent magnet can be moved.

Alternatively or additionally, the angular spread of the flux lines may also be changed by changing a first radius of the first circle of curvature and/or by changing a second radius of the second circle of curvature. The angular spread of the flux lines may be varied, for example by increasing/decreasing the amount of flux lines extending through the molding chamber and thus by increasing/decreasing the angle between two adjacent flux lines. Thereby, the position of the magnetic focusing point/region of the manufactured flux focusing permanent magnet can be moved.

According to an exemplary embodiment of the present invention, the center distance is changed such that the magnetic focus point or the magnetic focus area is located on the symmetry axis together with the first center and the second center. At the same time, the magnetic focus point is remote from the first and second centers and is disposed outside the second mold portion and simultaneously outside the mold.

The "alignment of the diffused magnetic flux" according to the invention may represent the amount of magnetic flux lines and the spatial orientation of the magnetic flux lines extending through the molding chamber. In other words, "alignment of the diffusing magnetic flux" may represent an angle between adjacent flux lines inside the molding chamber.

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

In other words, by changing the ratio of the first radius and the second radius, the angular spread of the flux lines can be changed, and this will increase/decrease the amount of flux lines extending through the mold chamber, and thus will increase/decrease the angle between two adjacent flux lines. Thereby, the position of the magnetic focusing point/region of the manufactured flux focusing permanent magnet can be moved.

According to an exemplary embodiment of the present invention, the magnetic focus point or the magnetic focus area is located on the symmetry axis together with the first center and the second center. At the same time, the magnetic focus point is remote from the first and second centers and is disposed outside the second mold portion and simultaneously outside the mold.

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

A hardness higher than 400 HV according to the application means that the material has a hardness higher than 400 HV when tested by the vickers hardness test.

The rationale for the vickers test is to observe the ability of a material to undergo plastic deformation from a standardized source. HV is the Vickers hardness number and is calculated from the load on the surface.

Metals with a hardness higher than 400 HV are very hard metals. During compaction of the magnetic material inside the moulding chamber, high loads act on the third mould part. Thus, forming the third mould part from a metal having a hardness higher than 400 HV may have the advantage that wear of the third mould part may be minimised.

In particular, the material of the third mould part has a magnetic polarisation strength of less than 0.6T (tesla). The magnetic polarization density characterizes the magnetic state of the material and is calculated as the magnetic moment of the volume. In other words, magnetic polarization density describes the density of permanent magnetic dipole moments in a magnetic material.

Forming the third mold portion from a metal having a magnetic polarization strength of less than 0.6T may have the following advantages: during the magnetization of the permanent magnet material accommodated inside the moulding chamber, the magnetization of the third mould part can be minimized.

According to a further embodiment of the invention, the molding chamber comprises: a first side surface facing the first curved surface of the first mold portion; and a second side surface opposite to the first side surface. Furthermore, the moulding chamber is positioned in the third mould part such that the distance of each of the two opposite corners of the first side surface positioned closest to the first curved surface of the first mould part to the first curved surface is in the range of 4 mm to 10 mm and/or such that the distance of the position of the second side surface positioned closest to the second curved surface of the second mould part is in the range of 4 mm to 10 mm.

The first side surface of the molding chamber is bounded by a plurality of, preferably four, side edges and a plurality of corners, particularly four corners. A molding chamber is disposed in the third mold portion, and a first side surface of the molding chamber is positioned adjacent to the first curved surface. Both of the plurality of corners positioned closest to the first curved surface are distal from the first curved surface. The distance between a point on the first curved surface and the corresponding corner is measured and is in the range of 4 mm to 10 mm. Thus, the mold can be prevented from being damaged and the conductivity can be prevented from being poor.

The second side surface of the molding chamber may be spatially shaped. Advantageously, the second side surface is curved. The second side surface is located closest to the second curved surface of the second mold section at a distance from the second curved surface in the range of 4 mm to 10 mm. Thus, the mold can be prevented from being damaged and the conductivity can be prevented from being poor.

By providing all three above defined distances in the range of 4 mm to 10 mm, mould damage and poor conductivity and leakage can be prevented even better.

According to a further embodiment of the invention, the molding chamber comprises: a first side surface facing the first curved surface of the first mold portion; and a second side surface opposite to 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 such that shrinkage of a sintered mass which has been obtained by magnetizing, compacting and sintering a powder which may be provided in the molding chamber is at least partially compensated.

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 that will compensate for the shrinkage effect after sintering and reduce machining of the final magnet block.

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 seen from the inside of the molding chamber.

According to the invention, the first curved lateral surface and/or the second curved lateral surface are designed such as to at least partially compensate for shrinkage of a sintered cake that has been obtained by compacting and sintering a magnetic powder that can be provided in the molding chamber. In other words, it is possible to compensate for the undesired deformation effects that are usually produced by shrinkage during sintering, with pre-accounting, by means of a suitably shaped moulding chamber that is different from the shape of the finally produced flux-focusing permanent magnet. This may provide the following advantages: the intended and undesired deformation can be compensated for to a large extent. This applies in particular to the shrinkage effect which occurs when the sintered permanent magnet cools down.

According to a further aspect of the invention, a system for manufacturing a permanent magnet, in particular a flux-focused permanent magnet, is provided. The system includes (a) a mold. The mold comprises: a first mold portion comprising a first curved surface having a first radius; a second mold portion comprising 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 further comprises 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 different materials relative to the third mold portion. The system further comprises: (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 magnetic device and the second magnetic device is producible by the first magnetic device and the second magnetic device, and wherein the first curved surface and the second curved surface are formed such that a magnetic flux through the first mold portion, the second mold portion, and the third mold portion is directed such that a diffuse magnetic flux is producible in the molding chamber.

The described system is also based on the following idea: permanent magnets, particularly flux-focused permanent magnets, having magnetic properties that achieve flux focusing can be directly and cost-effectively manufactured in the described system.

With respect to the molding chamber, the first and second magnetic means are located at opposite sides. Additionally, both the first magnetic means and the second magnetic means (which are referred to as alignment coils) are positioned outside the mold.

The first and second magnetic means are configured such that a linear magnetic field can be provided between the first and second magnetic means. The first magnetic means or the second magnetic means may be a magnetic coil. In particular, the first magnetic arrangement may be configured as a north pole and the second magnetic arrangement may be a south pole. It will be appreciated that the first magnetic means may be configured as a south pole and the second magnetic means may be configured as a north pole.

By providing the above-described mould between the first and second magnetic means, the first and second curved surfaces are formed such that the magnetic flux through the first, second and third mould parts is directed such that a diffuse magnetic flux may be generated in the moulding chamber.

According to a further aspect of the invention, a method for manufacturing a permanent magnet, in particular a flux-focused permanent magnet, is provided. The method includes (a) providing a mold. The mold comprises: a first mold portion comprising a first curved surface having a first radius; a second mold portion comprising a second curved surface having a second radius; and 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, wherein the first mold portion and the second mold portion are made of different materials with respect to the third mold portion, and wherein the first curved surface and the second curved surface are formed such that a magnetic flux passing through the first mold portion, the second mold portion, and the third mold portion is guided such that a diffuse magnetic flux can be generated in the molding chamber. The method further comprises the following steps: (b) placing a powder of a magnetic material into a molding chamber; (c) generating a magnetic field for aligning the powder contained within the molding chamber, wherein the magnetic field comprises a diffuse magnetic flux in the molding chamber; (d) compacting the powder contained within the moulding chamber in a magnetic field, wherein the magnetisation and compaction results in a magnetised compacted mass of powder having diffuse magnetic flux lines. The method further comprises the following steps: (e) the unmagnetized, only magnetically aligned compacted mass of the sintered and aged powder.

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

Typically, step (c) of generating a magnetic field to obtain magnetic alignment and step (d) of compacting the powder are at least partially accomplished simultaneously.

Powder of a magnetic material is put into a molding chamber, and a magnetic field is applied. The applied magnetic field is adjusted so that the magnetic polarization strength of the magnetic field inside the molding chamber is in the range of 0.8T to 1.6T.

The magnetic powder contained inside the molding chamber was compacted in a magnetic field to have a density of 3.7 g/cm³To 4.3 g/cm³The density of (c).

In the subsequent step, the resulting flux-focusing permanent magnet block is sintered and aged. Thereafter, the permanent magnet blocks are appropriately shaped according to desired requirements, and the alignment directions of the magnetic particles of the flux focusing permanent magnet blocks are diffused or in other words, radial.

According to another embodiment of the invention, the compaction may be isostatic pressing.

According to an embodiment of the invention, the powder comprises a rare earth material, in particular NdFeB (neodymium iron boron). This may provide the following advantages: very strong permanent magnets can be manufactured with the desired permanent magnet geometry and flux focusing properties.

In this respect, it should be mentioned that other compositions of permanent magnet material may include ferrite and/or SmCo (samarium cobalt).

According to a further aspect of the invention, a permanent magnet, in particular a flux-focusing permanent magnet, is provided, which is produced by carrying out the method as described above.

According to a further aspect of the invention, an electromechanical transducer, in particular a generator, is provided. The electromechanical transducer includes (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.

The electromechanical transducer provided is based on the following idea: it may be constructed with a rotor assembly that includes a flux focusing permanent magnet with magnetic properties that achieve flux focusing, directly and cost effectively manufactured.

According to a further aspect of the invention, a wind turbine for generating electrical power is provided. The provided wind turbine comprises: (a) a tower; (b) a wind rotor (wind rotor) arranged at a top part of the tower and comprising at least one blade; and (c) an electromechanical transducer as described above. The electromechanical transducer is mechanically coupled to the wind rotor.

The provided wind turbine (also named wind energy plant) is based on the following idea: the electromechanical transducer described above allows to realize a wind turbine in a cost-effective manner with respect to the flux-focusing permanent magnets used. This may help to increase the attractiveness of wind turbine technology for regenerative power production compared to other technologies, such as solar power plants.

It has to be noted that embodiments of the invention have been described with reference to different subject-matters. In particular, some embodiments have been described with reference to method type claims, whereas other embodiments have been described with reference to apparatus type claims. However, a person skilled in the art will gather from the above and the following description that, unless other notified, in addition to any combination of features belonging to one type of subject-matter also any combination between features relating to different subject-matters, in particular between features of the method type claims and features of the apparatus type claims, is considered to be disclosed with this document.

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.

Drawings

FIG. 1 shows a wind turbine according to an embodiment of the invention.

Fig. 2 shows a generator of the wind turbine of fig. 1 in a schematic view.

Fig. 3 illustrates a flux-focusing permanent magnet produced according to an embodiment of the present invention.

Fig. 4 shows an additional flux-focusing permanent magnet produced according to an embodiment of the present invention.

Fig. 5 illustrates an additional flux-focusing permanent magnet produced according to an embodiment of the present invention.

Fig. 6 shows a mold for manufacturing a flux-focusing permanent magnet according to an embodiment of the present invention.

Fig. 7 illustrates a magnetic field generating structure along with a mold for manufacturing a flux focusing permanent magnet according to an embodiment of the present invention.

Detailed Description

The illustration in the drawings is schematically. It should be noted that in different figures, similar or identical elements or features are provided with the same reference signs or with reference signs which differ from the corresponding reference signs only within the first digit. To avoid unnecessary repetition, elements or features that have been elucidated with respect to previously described embodiments are not again elucidated at a later position in the description.

FIG. 1 shows a wind turbine 100 according to an embodiment of the invention. Wind turbine 100 includes a tower 120 mounted on a foundation (fundamental), not depicted. On top of the tower 120 a nacelle 122 is arranged. Between the tower 120 and the nacelle 122, a yaw angle adjustment device 121 is provided, which is capable of rotating the nacelle 122 about a vertical axis, not depicted, which is aligned with the longitudinal extension of the tower 120. By controlling the yaw angle adjustment arrangement 121 in a suitable manner, it may be ensured that the nacelle 122 is always correctly aligned with the current wind direction during normal operation of the wind turbine 100.

The wind turbine 100 also includes a rotor 110 having three blades 114. In the perspective view of fig. 1, only two vanes 114 are visible. The wind rotor 110 is rotatable about a rotational axis 110 a. Blades 114 mounted at hub 112 extend radially with respect to rotational axis 110 a.

A blade angle adjustment device 116 is respectively provided between hub 112 and blades 114 for adjusting a blade pitch angle (blade pitch angle) of each blade 114 by rotating the respective blade 114 about a non-depicted axis aligned substantially parallel to a longitudinal extension of the respective blade 114. By controlling the blade angle adjustment devices 116, the blade pitch angle of the respective blades 114 is adjusted such that the maximum wind energy can be recaptured from the available mechanical power of the wind driving the wind rotor 110, at least when the wind is not too strong.

As can be seen from fig. 1, a gearbox 124 is provided within nacelle 122. The gearbox 124 serves to convert the number of revolutions of the wind rotor 110 into a higher number of revolutions of the shaft 125, which is coupled to an electromechanical transducer 130 in a known manner. The electromechanical transducer is a generator 130.

At this point it should be noted that the gearbox 124 is optional and that the generator 140 may also be coupled directly to the wind rotor 110 via the shaft 125 without changing the number of revolutions. In this case, the wind turbine is a so-called Direct Drive (DD) wind turbine.

Furthermore, a brake 126 is provided in order to stop the operation of the wind turbine 100 or in order to reduce the rotational speed of the rotor 110, e.g. in case of an emergency.

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

According to the basic principles of electrical engineering, the generator 130 includes a stator assembly 135 and a rotor assembly 140. In the embodiment described herein, the generator 130 is implemented in a so-called "inner stator-outer rotor" configuration, wherein the rotor assembly 140 surrounds the stator assembly 135. This means that the not depicted permanent magnet or magnet assembly of the rotor assembly 140 travels around an arrangement of a plurality of not depicted coils of the inner stator assembly 135, which coils generate an induced current that results from picking up a time varying magnetic flux from the traveling permanent magnet.

According to embodiments described herein, each permanent magnet assembly comprises at least three flux-focusing permanent magnet arrangements, in particular made of an NdFeB material composition.

Fig. 2 shows a schematic view of the generator 130 in a cross-sectional view. The generator 130 includes a stator assembly 135. Stator assembly 135 includes a stator support structure 237 that includes a stack of a plurality of laminations and a plurality of stator windings 239 housed within stator support structure 237. The windings 239 are interconnected in a known manner by means of electrical connections not depicted.

The rotor assembly 140 of the generator 130 (which is separated from the stator assembly 135 by an air gap designated with reference ag) includes a rotor support structure 242 that provides a mechanical base for mounting a plurality of flux focusing magnet segments 250. In fig. 2, the axis of rotation 110a of the rotor assembly 140 is designated with reference numeral 230 a.

In the exemplary embodiment described herein, three flux-focusing permanent magnets are disposed in close proximity to each other at each angular position of the rotor assembly 140. It should be mentioned that in fig. 2, for ease of illustration, only three flux-focusing sections 250 of one permanent magnet are depicted assigned to one angular position. Indeed, depending on the size of the generator 130, a plurality of 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 configuration around the curved surface area of the support structure 242, which has a substantially cylindrical geometry about the generator axis 240 a.

As can be seen in fig. 2, the flux focusing magnet sections 250 are not directly mounted to the rotor support structure 242. Instead, a back plate 244 made of a ferromagnetic material (e.g., iron) is provided. A back plate (back plate) is provided to ensure correct guidance of the magnetic flux. This significantly reduces the strength of the stray magnetic field in a beneficial way.

Fig. 3 shows a flux-focusing permanent magnet 350 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.

The flux-focusing permanent magnet 350 is magnetized such that a spread angle distribution of flux lines 352 is given. According to the embodiments described herein, each flux line 352 follows a straight magnetization line. The linear magnetization lines are angled or inclined with respect to each other in a fan-like manner. In other words, the straight magnetization line is diffused. Specifically, the spread angle distribution of the straight magnetization lines creates a focal point 354 in a region 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.

According to the exemplary embodiments described herein, the depicted pattern of magnetic flux lines is symmetric about an axis of symmetry 349. In this document, the axis of symmetry 349 is also named magnetic axis. Magnetic axis 349 is a normal axis to major surface 351 and extends through focal point 354.

As depicted in fig. 3, the major surface 351 is planar, and in the cross-sectional view of fig. 3, the flux-focusing permanent magnet 350 is rectangular. Therefore, the flux-focusing permanent magnet 350 shown in fig. 3 is a rectangular parallelepiped in a three-dimensional view.

Fig. 4 shows a flux-focusing permanent magnet 450 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.

The flux-focusing permanent magnet 450 is pre-magnetized so as to give a diffuse angular distribution of flux lines 452. According to the embodiments described herein, each flux line 452 follows a straight line of magnetization. The linear magnetization lines are angled or inclined with respect to each other in a fan-like manner. In other words, the straight magnetization line is diffused. Specifically, the spread angle distribution of the straight magnetization lines creates a focal point 454 in a region above the primary 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.

As depicted in fig. 4, the major surface 451 is curved or arcuate, and in the cross-sectional view of fig. 4, the flux-focusing permanent magnet 350 is shaped like a rectangle having one curved major surface 451. Thus, the flux-focusing permanent magnet 450 shown in fig. 4 is shaped to image a slice of bread in a three-dimensional view.

Fig. 5 shows a flux-focusing permanent magnet 550 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.

The flux-focusing permanent magnet 550 is magnetized so as to give a divergent angular distribution of the flux lines 552. According to the embodiments described herein, each flux line 552 follows a straight line of magnetization. The linear magnetization lines are angled or inclined with respect to each other in a fan-like manner. In other words, the straight magnetization line is diffused. Specifically, the spread angle distribution of the straight magnetization lines creates a focal point 554 in the region above the primary surface 555 of the flux focusing permanent magnet 550 that is characterized by a local maximum in the magnetic field or flux density generated by the flux focusing permanent magnet 550.

As depicted in fig. 5, major surface 555 is shaped. In particular, major surface 555 includes three sub-portions. These three sub-portions are two curved sub-portions 556, which are additionally tilted, and a planar sub-portion 557. Each of the two curved sub-portions 556 interconnects one side surface 558 of the flux-focusing permanent magnet 550 with a planar sub-portion 557. Additionally, the planar sub-portion 557 is parallel to another major surface 559 that delimits the flux-focusing permanent magnet 550 on the opposite side with respect to the major surface 555. The planar sub-portion 557 also intersects the magnetic axis 549, and the major surface 555 is symmetric about the magnetic axis 549. Further, the flux focusing permanent magnet 550 is symmetrical with respect to the symmetry axis 549.

Fig. 6 illustrates a mold 660 for manufacturing a flux-focused magnet section 250, according to an embodiment of the invention.

The mold 660 includes a first mold portion 661, a second mold portion 662, and a third mold portion 663. The third mold portion 663 includes a molding chamber 664 located inside the third mold portion 663. Thus, the molding chamber 664 is located inside the third mold portion 663 such that each of the four sides of the molding chamber 664 are distal from the first and

second mold portions

661, 662, respectively.

The molding chamber 664 includes four sides, and in particular, a first side surface 665, a second side surface 667, a third side surface 668, and a fourth side surface 669. First side surface 665 and second side surface 667 are curved.

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. The third mold portion 663 includes: a third (curved) surface 683 having a third radius corresponding to the 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 additional third surfaces 684.

As can be seen in fig. 6, a third face 683 is coupled to the first face 681, and an additional third face 684 is coupled to the second face 682. Thus, the first surface 681 and the third surface 683 are shaped to correspond to each other, and the second surface 682 and the further third surface 684 are shaped to correspond to each other.

The first surface 681 includes a first circle of curvature having a first center 685, and the second surface 682 includes a second circle of curvature having a second center 686. A center distance 687 is disposed between first center 685 and second center 686. The center distance 687 is such that the first and second circles of curvature are non-concentric. Thus, the first center 685 is located a center distance 687 away from the second center 686. The second center 686 is positioned on the magnet axis 649 and on a surface of the second mold portion 662 opposite the second curved surface 682. First center 685 is also positioned on axis of symmetry 649 and is positioned inside second mold portion 662.

The width 689 of the molding chamber 664 is greater than twice the second radius 672. Furthermore, the center distance 687 is greater than 10 mm.

Fig. 7 illustrates a system 790 for manufacturing a flux-focusing magnet segment 250, in accordance with an embodiment of the invention.

The system 790 includes a mold 760 as described in detail with reference to fig. 6. The system 790 further comprises: a first magnetic device 791 configured as a north pole; and a second magnetic device 792 configured as a south pole. It will be appreciated that the first magnetic device 791 may also be configured as a south pole and the second magnetic device 792 may also be configured as a north pole.

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

In particular, the spread angle distribution of the straight magnetized lines 752 produces a focal point/region 754 in the region below the second mold portion 762 that is characterized by a local maximum in the magnetic field or flux density.

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

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. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.

Claims

1. A mold (660, 760) for manufacturing a permanent magnet (350, 450, 550), in particular a flux-focusing permanent magnet (350, 450, 550), the mold (660, 760) comprising:

a first mold portion (661) including 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 a ferromagnetic material, and

a third mold portion (663) having a molding chamber (664);

wherein the third mold portion (663) is arranged between the first mold portion (661) and the second mold portion (662);

wherein the first mould part (661) and the second mould part (662) are made of different materials with respect to the third mould part (663);

wherein the first curved surface (681) and the second curved surface (682) are formed such that magnetic flux passing through the first mold portion (661), the second mold portion (662), and the third mold portion (663) is directed such that a diffuse magnetic flux can be generated in the molding chamber (664).

2. The mold (660, 760) of claim 1,

wherein the third mold portion (663) comprises: a third surface (683) that is curved and has a third radius that corresponds to the first radius (671) of the first curved surface (681); and a further third surface (684) opposite to said 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 portion (663) is coupled to the first curved surface (681) of the first mold portion (661), and the further third surface (684) of the third mold portion (663) is coupled to the second curved surface (682) of the second mold portion (662).

3. The mold (660, 760) of claim 1 or 2,

wherein the first curved surface (681) comprises a first circle of curvature having a first center (685);

wherein the second curved surface (682) comprises 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 an alignment of the diffusive magnetic flux in the molding chamber (664).

4. The mold (660, 760) according to any of claims 1 to 3,

wherein a ratio of the first radius (671) and the second radius (672) is adapted to enable adjustment of an alignment of the diffusive magnetic flux in the molding chamber (664).

5. The mold (660, 760) according to any of claims 1 to 4,

wherein the third mould part (663) is made of a metal having a hardness higher than 400 HV.

6. The mold (660, 760) according to any of claims 1 to 5,

wherein the molding chamber (664) comprises: a first side surface (665) facing the first curved surface (681) of the first mold portion (661); and a second side surface (667) opposite the first side surface (665);

wherein the molding chamber (664) is positioned in the third mold portion (663),

such that a distance of each of two opposite corners of the first side surface (665) located closest to the first curved surface (681) of the first mould part (661) to the first curved surface (681) is in the range of 4 mm to 10 mm, and/or

Such that a position of the second side surface (667) that is closest to the second curved surface (682) of the second mold portion (662) is within a distance of 4 mm to 10 mm from the second curved surface (682) of the second mold portion (662).

7. The mold (660, 760) according to any of claims 1 to 6,

wherein the molding chamber (664) comprises: a first side surface (665) facing the first curved surface (681) of the first mold portion (661); and a second side surface (667) opposite the first side surface (665); and is

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;

wherein the first curved side surface and/or the second curved side surface are designed such as to at least partially compensate for shrinkage of a sintered cake that has been obtained by compacting a powder that can be provided in the moulding chamber (664).

8. A system (790) for manufacturing a permanent magnet (350, 450, 550), in particular a flux-focusing permanent magnet (350, 450, 550), the system (790) comprising:

a mold (660, 760) comprising:

a third mold portion (663) having a molding chamber (664);

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 means (791) and the second magnetic means (792) is generatable by the first magnetic means (791) and the second magnetic means (792);

9. A method of manufacturing a permanent magnet (350, 450, 550), in particular a flux-focusing permanent magnet (350, 450, 550), the method comprising:

providing a mold (660, 760), the mold comprising:

a second mold portion (662) including a second curved surface (682) having a second radius (672); and

a third mold portion (663) having a molding chamber (664);

wherein the first curved surface (681) and the second curved surface (682) are formed such that magnetic flux through the first mold portion (661), the second mold portion (662), and the third mold portion (663) is directed such that a diffuse magnetic flux can be generated in the molding chamber (664);

wherein the method further comprises:

placing a 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 comprises the diffuse magnetic flux in the molding chamber (664);

compacting the powder contained within the molding chamber (664) in the magnetic field;

the aligning and compacting results in aligned compacted masses of the powder having diffuse magnetic flux lines;

thereafter, the aligned compacted cake of powder is sintered and aged.

10. The method of claim 9, wherein the first and second light sources are selected from the group consisting of,

wherein the powder comprises a rare earth material, in particular NdFeB.

11. Permanent magnet (350, 450, 550), in particular a flux-focusing permanent magnet (350, 450, 550), which is manufactured by carrying out the method according to claim 9 or 10.

12. An electromechanical transducer (130), in particular a generator, the electromechanical transducer (130) comprising:

a stator assembly (135), and

a rotor assembly (140) comprising:

a support structure, and

the at least one permanent magnet (350, 450, 550) according to claim 11, wherein the permanent magnet (350, 450, 550) is mounted to the support structure.

13. A wind turbine (100) for generating electrical power, the wind turbine (100) comprising:

a tower (120) having a plurality of towers,

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 12, wherein the electromechanical transducer (130) is mechanically coupled with the wind rotor (110).