EP3948904A2 - Manufacturing flux focused magnet using a changing magnetization - Google Patents

Manufacturing flux focused magnet using a changing magnetization

Info

Publication number
EP3948904A2
EP3948904A2 EP19761771.5A EP19761771A EP3948904A2 EP 3948904 A2 EP3948904 A2 EP 3948904A2 EP 19761771 A EP19761771 A EP 19761771A EP 3948904 A2 EP3948904 A2 EP 3948904A2
Authority
EP
European Patent Office
Prior art keywords
magnetic
molding chamber
magnetic flux
set forth
yoke
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19761771.5A
Other languages
German (de)
French (fr)
Inventor
Ziad Azar
Qingfang HUANG
Hans-joergen Thougaard
Qingkun TONG
Adriana Cristina Urda
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens Gamesa Renewable Energy AS
Original Assignee
Siemens Gamesa Renewable Energy AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens Gamesa Renewable Energy AS filed Critical Siemens Gamesa Renewable Energy AS
Publication of EP3948904A2 publication Critical patent/EP3948904A2/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
    • H01F41/0273—Imparting anisotropy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F13/00—Apparatus or processes for magnetising or demagnetising
    • H01F13/003—Methods and devices for magnetising permanent magnets
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
    • H01F41/0266—Moulding; Pressing
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K1/00—Details of the magnetic circuit
    • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
    • H02K1/22—Rotating parts of the magnetic circuit
    • H02K1/28—Means for mounting or fastening rotating magnetic parts on to, or to, the rotor structures
    • H02K1/30—Means for mounting or fastening rotating magnetic parts on to, or to, the rotor structures using intermediate parts, e.g. spiders
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K15/00—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines
    • H02K15/02—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies
    • H02K15/03—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies having permanent magnets
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/06—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys in the form of particles, e.g. powder
    • H01F1/08—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together
    • H01F1/086—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together sintered
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/18—Structural association of electric generators with mechanical driving motors, e.g. with turbines
    • H02K7/1807—Rotary generators
    • H02K7/1823—Rotary generators structurally associated with turbines or similar engines
    • H02K7/183—Rotary generators structurally associated with turbines or similar engines wherein the turbine is a wind turbine
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/72—Wind turbines with rotation axis in wind direction

Definitions

  • the present invention relates to an apparatus and to a method for manufacturing a permanent magnet. Further, the present invention relates to a magnet being produced with the
  • Permanent magnetic materials are used in a plurality of different fields of application. Probably the technically and economically most important field of applications are
  • electromechanical transducers i.e. electric motors and electric generators.
  • An electric motor being equipped with at least one permanent magnet (PM) converts electric energy into mechanical energy by producing a temporary varying magnetic field by means of windings or coils. This temporary varying magnetic field interacts with the magnetic field of the PM resulting e.g. in a rotational movement of a rotor assembly with respect to a stator assembly of the electric motor.
  • an electric generator converts mechanical energy into electric energy.
  • An electric generator is a core component of any power plant for generating electric energy. This holds true for power plants which directly capture mechanical energy, e.g.
  • hydroelectric power installations tidal power installations, and wind power installations also denominated wind turbines.
  • power plants which (i) first use chemical energy e.g. from burning fossil fuel or from nuclear energy in order to generate thermal energy and which (ii) second convert the generated thermal energy into mechanical energy by means of appropriate thermodynamic processes .
  • the efficiency of an electric generator is probably the most important factor for optimizing the production of electric energy.
  • PM electric generator it is essential that the magnetic flux produced by the permanent magnets (PMs) is strong. This can probably best be achieved with sintered rare earth magnets, e.g. using a FeNdB material composition.
  • EP 3 276 642 A1 discloses a sintered rare earth PM having a focusing magnetic alignment pattern with a single piece PM body.
  • EP 2 762 838 A2 discloses apparatuses and methods for manufacturing PMs, wherein during a sintering process an non-uniform external magnetic field is applied in order to magnetize different regions of a PM in different directions .
  • Magnetic fluxing offers a large increase in the airgap flux density leading to higher torque/power of electromechanical transducers such as electric generators for direct-drive wind turbines. Therefore, already in the near future there will be an increasing demand for Flux Focusing Permanent Magnet (FFPM) pieces/devices.
  • FFPM Flux Focusing Permanent Magnet
  • the desired strength or degree of magnetic focusing which in analogy to optics may be characterized by a so called (magnetic) focal length, depends on the specific field of application.
  • an apparatus for manufacturing a permanent magnet, in particular a sintered permanent magnet comprises (a) a mold having a molding chamber for receiving a powder of a permanent magnet material; (b) a first magnetic device and a second magnetic device for generating a magnetic flux for magnetizing the powder being accommodated within the molding chamber; (c) a die for compacting the powder being accommodated within the molding chamber; and (d) a magnetic element for spatially guiding and/or modifying the magnetic flux.
  • the magnetic element is located and movably supported in a region extending between the first magnetic device and the second magnetic device such that in a first position of the magnetic element there is given a first spatial magnetic flux distribution within at least the molding chamber and in a second position of the magnetic element there is given a second spatial magnetic flux distribution within at least the molding chamber.
  • the second spatial magnetic flux distribution is different from the first spatial magnetic flux distribution.
  • the described apparatus is based on the idea that when placing, during a powder compacting and magnetizing
  • the magnetic element in at least two different positions, the spatial magnetic flux distribution changes during these processes.
  • the spatial magnetic flux distribution changes in such a manner that the powder is subjected to at least one spatial nonhomogeneous or
  • FFPM Flux Focusing Permanent Magnet
  • the magnetic flux focusing characteristics may also be determined by the relative timing between adopting these positions and the progress of the magnetizing and compacting procedures.
  • Such steps may include e.g. a proper shaping e.g. by means of a removal of sintered magnetic material and/or a surface finishing.
  • steps of magnetizing and compacting are typically carried out simultaneously or at least with a certain overlap in time.
  • magnetizing the powder by means of the magnetic flux may be associated with an
  • the actuator mechanism may be configured for moving the magnetic element in a continuous manner. However, in certain applications the actuator mechanism may drive the magnetic element in a stepwise manner to and from discrete positions.
  • the first magnetic device and the second magnetic device are configured to generate, in a virtual absence of the magnetic element, a magnetic flux pattern which comprises, at least within the molding chamber, a spread angular distribution of magnetic flux lines.
  • magnetized compacted block having a focused pattern of magnetic alignment directions can be produced. This means that (the presence of) the movable magnetic element will (only) modify the focusing magnetic flux pattern.
  • the spread angular distribution of magnetic flux lines generated solely by the (at least) two magnetic devices is stationary in time it can be seen as to represent a base magnetic flux pattern.
  • the time varying magnetic flux generated by the moving magnetic element can be seen as to represent an offset to the base magnetic flux pattern.
  • At least one of the two magnetic devices comprises (a) an electro magnetic coil for producing the magnetic flux and (b) a magnetic yoke for guiding and/or for shaping the magnetic flux being produced by the electromagnetic coil.
  • Supporting the electromagnetic coil in producing the magnetic flux by providing a proper magnetic yoke may provide the advantage that the magnetic flux (density) , at least within selected regions of the molding chamber, can be increased significantly. Further, by designing the shape and/or the geometry of the magnetic yoke in a proper manner a desired (base) spread angular distribution of magnetic flux lines can be produced which yields a desired focused flux base
  • the magnetic yoke which may also be denominated a pole piece, may be made from a ferromagnetic material, in
  • the mold may be made from a non-magnetic and in particular from a non
  • ferromagnetic material A (currently) preferred material is stainless steel. However, also other mold materials may be used provided that are mechanical stiff.
  • the magnetic element is supported in such a manner that it is continuously movable along a predefined trajectory. This may provide the advantage that the positions the magnetic element can be and is brought to can be spatially defined in a highly precise manner. This may result in a high accuracy of the
  • the trajectory can be predefined by any mechanical guiding structure comprising e.g. a guide bar or a guide rail.
  • the guiding structure is made from a non-magnetic material such as e.g. stainless steel in order not to disturb the magnetic flux.
  • the continuous movement can even be seen as a discrete movement to and from an infinite number of positions wherein the distance between two neighboring positions is zero.
  • a length of the predefined trajectory determines a magnetic focal distance of the permanent magnet.
  • the magnetic focusing can be seen as an analogon to an optical focusing. This means that an angular spread of magnetic domain alignment directions along one direction, which is sufficient for most applications of a FFPM, results in a one dimensional (ID) magnetic flux
  • Such a magnetic focusing corresponds to an optical focusing by means of a cylindrical optical lens.
  • the magnetic flux within the molding chamber may have an angular spread along two directions being
  • Such a magnetic focusing corresponds to an optical focusing by means of a spherical optical lens.
  • the length may not necessarily be the maximum possible length allowed e.g. by the above identified guiding structure.
  • the length may rather be the actual length the magnetic element is moved during a certain magnetizing and compacting procedure. This means that depending on the actual length with respect to the maximum possible length the magnetic flux focusing characteristic can be adjusted
  • the predefined trajectory is a path along a curved shape, in particular along a circular arc. This may provide the
  • the first magnetic device has a first magnetic yoke and the second magnetic device has a second magnetic yoke.
  • the first magnetic yoke and the second magnetic yoke are located at opposing sides.
  • the first magnetic yoke has a first outer yoke surface facing the molding chamber and the second magnetic yoke has a second outer yoke surface facing the molding chamber.
  • the first outer yoke surface is concave and the second outer yoke surface is convex or planar.
  • the described spatial design of the two magnetic yokes may provide the advantage that a proper and well defined spread angular distribution of magnetic flux lines within the molding chamber can be generated in an easy and effective manner.
  • the bending of the outer yoke surfaces may be regular, i.e. without any corners and edges ("lumps and bumps"), or may be irregular.
  • the first outer yoke surface has a first radius and the second outer yoke surface has a second radius being different from the first radius. This may provide the advantage that a higher alignment angle of the magnetic domain alignment directions at and with regard to side edges of the magnetized compacted block can be realized.
  • the (at least one) magnetic element comprises or is made from a magnetic material, in particular from a ferromagnetic material. This may provide the advantage that with regard to the base magnetic flux pattern caused (solely) by the magnetic devices the (wanted) temporal magnetic perturbation caused by the moving magnetic element will be strong. Hence, higher alignment angles of the magnetic domain alignment directions at and with regard to side edges of the magnetized compacted block can be realized.
  • the ferromagnetic material may be iron or a composition of iron and cobalt. It is mentioned that in embodiments
  • comprising (at least) two magnetic elements of cause all magnetic elements may comprise or may be made from such a magnetic material.
  • the apparatus further comprises a further magnetic element being supported in such a manner that it is continuously movable along a further predefined trajectory. This may provide the advantage that the magnetization procedure can be made more effective with regard to the magnetization strength.
  • the magnetization procedure can be speeded up because (at least) two magnetic elements are "working" simultaneously.
  • the predefined trajectory and the further predefined trajectory are symmetric with respect to each other. This may provide the advantage that FFPMs, which have a symmetric spread angular distribution of magnetic domain alignment directions, can be manufactured in an easy and reliable manner.
  • magnetic symmetry axis of the apparatus may particularly refer to a spatial distribution of magnetic field lines which are produced by means of the two magnetic devices. This holds true for (a) a virtual absence of the two magnetic elements or (b) an operational state of the apparatus where the two magnetic elements are equally spaced apart from this magnetic symmetry axis.
  • the predefined trajectory is a path along a curved or linear shape and the further predefined trajectory is a further path along a further curved or linear shape.
  • the respective curved shape may be a circular arc. This may provide the advantage that both magnetic elements may travel along a geometrically very simple path. Hence, a resulting magnetic flux focusing characteristic can be predicted in an easy and precise manner. This facilitates the magnetic design of FFPM pieces.
  • the first magnetic device has a first magnetic yoke and the second magnetic device has a second magnetic yoke. Further, with regard to the molding chamber, the first magnetic yoke and the second magnetic yoke are located at opposing sides.
  • first magnetic yoke has a first outer yoke surface facing the molding chamber and the second magnetic yoke has a second outer yoke surface facing the molding chamber.
  • the first outer yoke surface is planar and the second outer yoke surface is convex.
  • the described spatial design of the two magnetic yokes may provide the advantage that a proper and well defined spread angular distribution of magnetic flux lines within the molding chamber can be generated in an easy and effective manner.
  • the bending of the convex second outer yoke surface may be regular, i.e. without any corners and edges ("lumps and bumps"), or may be irregular.
  • a method for manufacturing a permanent magnet, in particular a sintered permanent magnet comprises (a) filling a powder of permanent magnet material into a molding chamber of a mold; (b) generating a magnetic flux for magnetizing the powder being accommodated within the molding chamber by means of a first magnetic device and a second magnetic device; (c) compacting the powder being accommodated within the molding chamber by means of a die; (d) moving, within a region extending between the first magnetic device and the second magnetic device, at least one magnetic element, which is spatially guiding and/or modifying the generated magnetic flux, from a first position to at least a second position.
  • the first position of the at least one magnetic element there is given a first spatial magnetic flux distribution within at least the molding chamber and in the second position of the at least one magnetic element there is given a second spatial magnetic flux distribution within at least the molding chamber.
  • the second spatial magnetic flux distribution is different from the first spatial magnetic flux distribution.
  • the described method is based on the idea that when moving the at least one magnetic element the spatial magnetic flux distribution may change in such a manner that a FFPM can be manufactured in an effective and flexible manner.
  • flexible means that depending on the spatial movement of the at least one magnetic element different patterns of magnetic domain alignment directions within the magnetized compacted block can be realized.
  • moving the at least one magnetic element comprises (a) a first movement along a predefined trajectory in a first direction and (b) a second movement along the predefined trajectory in a second direction being opposite to the first direction.
  • permanent magnet material comprises a rare earth material, in particular NdFeB. This may provide the advantage that very strong FFPMs can be manufactured.
  • compositions of the permanent magnet material may include ferrite and/or SmCo .
  • a permanent magnet in particular a permanent sintered magnet, being produced by carrying out a method as described above.
  • an electromechanical transducer in particular an electric generator.
  • the provided electromechanical transducer comprises (a) a stator assembly, and (b) a rotor assembly.
  • the rotor assembly comprises (bl) a support structure and (b2) at least one permanent magnet as described above.
  • the permanent magnet is mounted to the support structure.
  • the provided electromechanical transducer is based on the idea that it can be built up with a rotor assembly comprising at least one (sintered) FFPM which exhibits a proper magnetic flux focusing. Due to the proper magnetic flux focusing the efficiency of the electric generator with regard to the amount of electric power, which can be produced with a certain amount of available "mechanical" power, can be improved .
  • a wind turbine for generating electrical power.
  • the provided the wind turbine comprises (a) a tower; (b) a wind rotor, which is arranged at a top portion of the tower and which comprises at least one blade; and (c) an electro mechanical transducer as described above.
  • the provided wind turbine also denominated a wind energy installation, is based on the idea that the above described electromechanical transducer allows to improve the energy conversion efficiency of a wind turbine. This may contribute for improving the attractiveness of wind turbine technology for regenerative power production as compared to other technologies such as solar plants.
  • FIG. 1 shows a wind turbine in accordance with an
  • Figure 2 shows in a schematic representation the generator of the wind turbine of Figure 1.
  • Figure 3 shows a Flux Focusing Permanent Magnet (FFPM) produced in accordance with an embodiment of the invention .
  • FFPM Flux Focusing Permanent Magnet
  • Figure 4 shows an apparatus for manufacturing a sintered
  • Figure 5 shows an apparatus for manufacturing a sintered
  • FIG. 1 shows in accordance with an embodiment of the invention a wind turbine 100, which comprises a tower 120 being mounted on a non-depicted fundament. On top of the tower 120 there is arranged a nacelle 122. Further, there is provided a yaw angle adjustment device 121 which is capable of rotating the nacelle 122 around a non-depicted vertical axis being aligned with the longitudinal extension of the tower 120. By controlling the yaw angle adjustment device 121 in an appropriate manner it can be made sure that during a normal operation of the wind turbine 100 the nacelle 122 is always properly aligned with the wind direction.
  • the wind turbine 100 further comprises a wind rotor 110 having three blades 114. In the perspective of Figure 1 only two blades 114 are visible.
  • the rotor 110 is rotatable around a rotational axis 110a.
  • the blades 114 which are mounted at a hub 112, extend radially with respect to the rotational axis 110a.
  • a blade angle adjustment device 116 in order to adjust the blade pitch angle of each blade 114 by rotating the respective blade 114 around a non-depicted axis being aligned substantially parallel with the longitudinal
  • the blade angle adjustment device 116 By controlling the blade angle adjustment device 116 the blade pitch angle of the respective blade 114 can be adjusted in such a manner that a maximum wind power can be retrieved from the available mechanical power of the wind driving the wind rotor 110.
  • an optional gear box 124 is provided within the nacelle 122 within the nacelle 122.
  • the gear box 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 in a known manner to an electromechanical transducer 130.
  • the electromechanical transducer is a generator 130.
  • a wind turbine without a gear box is called a Direct Drive (DD) wind turbine .
  • DD Direct Drive
  • a brake 126 is provided in order to stop the
  • the wind turbine 100 further comprises a control system 143 for operating the wind turbine 100 in a highly efficient manner. Apart from controlling for instance the yaw angle adjustment device 121 the depicted control system 153 is also used for adjusting the blade pitch angle of the rotor blades 114 in an optimized manner.
  • the generator 130 comprises a stator assembly 135 and a rotor assembly 140.
  • the generator 130 is realized in a so called “inner stator - outer rotor” configuration. This means that the rotor assembly 140
  • stator assembly 135 surrounds the stator assembly 135 and that non-depicted permanent magnets or PM assemblies of the rotor assembly 140 travel around an arrangement of a plurality of non-depicted coils of the inner stator assembly 135 which coils produce an induced current resulting from picking up a time varying magnetic flux from the traveling permanent magnets.
  • each permanent magnet (PM) assembly comprises at least three sintered permanent magnet pieces which are made from a NdFeB material composition .
  • Figure 2 shows in a cross sectional view a schematic
  • the generator 130 comprises a stator assembly 135.
  • the stator assembly 135 comprises a stator support structure 237 comprising a stack of a plurality of lamination sheets and a plurality of stator windings 239 being accommodated within the stator support structure 237.
  • the windings 239 are interconnected in a known manner by means of non-depicted electrical connections.
  • a rotor assembly 140 of the generator 130 which is separated from the stator assembly 135 by an air gap ag, comprises a rotor support structure 242 providing the mechanical base for mounting a plurality of sintered permanent magnets 250.
  • the sintered magnets are Flux Focusing Permanent Magnets (FFPM) which, when designed with a proper magnetic focal length, allow to increase the magnetic flux density within the airgap ag.
  • FFPM Flux Focusing Permanent Magnets
  • a plurality of FFPMs 250 are mounted to the rotor support structure 242.
  • the FFPMs 250 are preferably arranged in a matrix like structure around a curved surface area of the support structure 242 having a basically cylindrical geometry around the generator axis 240a.
  • the sintered FFPMs 250 are not mounted directly to the rotor support structure 242. Instead, there is provided a back plate 244 made from a ferromagnetic material, e.g. iron.
  • the back plate 244 is provided in order to ensure a proper guidance of magnetic flux.
  • FIG 3 shows a FFPM 350 produced in accordance with an embodiment of the invention.
  • the FFPM 350 is magnetized in such a manner that there is given a spread angular
  • each magnetic domain alignment direction 352 follows a straight
  • the straight lines are angled or inclined with respect to each other in a fan like manner.
  • the spread angular distribution of the straight magnetization lines produces, in the region above a main surface 350a of the FFPM 350, a focal point 354 being
  • the distance between the front surface of the FFPM 350 and the focal point 354 is the magnetic focal distance fd.
  • the depicted magnetic domain alignment pattern is symmetric with respect to a symmetry axis 354a.
  • symmetry axis 354a is also denominated magnetic axis.
  • the magnetic axis 354a is a normal axis to the main surface 350a, which runs through the focal point 354.
  • Figure 4 shows an apparatus 460 for manufacturing a block in the form of pressed magnet powder that can be sintered in an oven and become a sintered permanent magnet.
  • the apparatus 460 is used for compacting and magnetizing a powder of magnetic material 495.
  • a subsequent sintering of a resulting magnetized compacted block is carried out in a non- depicted sintering oven.
  • the apparatus 460 comprises a mold 470 within which a molding chamber 472 is formed.
  • the molding chamber 472 can be closed by at least one non depicted die, which is also used for compacting the powder 495.
  • the movement of the at least one die is along a direction being perpendicular to the plane of drawing .
  • the apparatus 460 further comprises means for producing a magnetic flux which is applied to the compacted powder 495.
  • These magnetic flux production means include a first magnetic device 461 and the second magnetic device 464.
  • the first magnetic device 461 produces a magnetic North pole N and the second magnetic device 464 produces a magnetic South Pole S.
  • the second magnetic device 464 comprises (i) a second
  • the first magnetic yoke 463 being assigned to the North pole and the second magnetic yoke 466 being assigned to the South pole have a different geometry. Specifically, the bending radii of the outer surfaces of the two magnetic yokes 463, 466 is different from each other.
  • the first magnetic yoke 463 has a first outer yoke surface 463a facing the molding chamber 472.
  • the first outer yoke surface 463a is, with respect to the location of the molding chamber 472 a convex surface having a bending radius R1.
  • the second magnetic yoke 466 has a second outer yoke surface 466a facing the molding chamber 472.
  • the second outer yoke surface 466a is, with respect to the location of the molding chamber 472 a concave surface having a bending radius R2.
  • R1 is significantly larger than R2.
  • the difference in geometry of the magnetic yokes 463, 466 has the effect that within the molding chamber 472 there will be provided an inhomogeneous magnetic field respectively
  • inhomogeneous magnetization may result in a spread angular distribution of magnetic domain alignment directions 352 as shown in Figure 3.
  • the apparatus 460 comprises further means for increasing the inhomogeneity of the magnetic flux within the molding chamber. Thereby, a FFPM can be produced which has a short focal distance.
  • the apparatus 460 further comprises a magnetic element 480 which can travel along a predefined trajectory 481.
  • the spatial course of the trajectory 481 is defined by a non-depicted guiding structure.
  • the predefined trajectory is an arc shaped curved path 481 which runs parallel to the concave surface 463a of the first magnetic yoke 463.
  • the magnetic element 480 can be moved forth and back between a first position 480a and a second position 480b. The corresponding movement is actuated by means of a schematically depicted actuator mechanism 482.
  • Figure 5 shows an apparatus 560 for manufacturing a sintered permanent magnet in accordance with another embodiment of the invention.
  • the apparatus 560 has significant structural similarities with the apparatus 460.
  • the second magnetic device which in this embodiment produces the magnetic South Pole for the magnetic powder 495, and the mold 470 are the same as in the apparatus 460.
  • the apparatus 560 comprises not only one but two magnetic
  • first magnetic element 580 and a further or second magnetic element 590.
  • both magnetic elements 580, 590 move along a linear direction.
  • a first trajectory 581 is assigned to the first magnetic element 580 and a further or second trajectory 591 is assigned to the second magnetic element 590.
  • the first trajectory 581 extends between a first position 580a of the first magnetic element 580 (depicted with full lines) and a second position 580b of the first magnetic element 580 (depicted with dashed lines) .
  • the second trajectory 591 extends between a first position 590a of the second magnetic element 590 (depicted with full lines) and a second position 590b of the second magnetic element 590 (depicted with dashed lines) .
  • a first magnetic device 561 producing the North Pole comprises a first electromagnetic coil 562 and a first magnetic yoke 563.
  • the first magnetic yoke 563 comprises a planar first outer yoke surface 563a.
  • the apparatus 560 is operated in a symmetric manner.
  • the "symmetry" relates to the magnetic field (line) pattern which is given between the two magnetic devices 561 and 464.
  • this pattern exhibits an axial symmetry with regard to a magnetic symmetry axis 560a.
  • two magnetic elements move along a non-linear path.
  • a non-linear path may have any other curved shape such as a circular shape as shown in Figure 4.
  • the shape of the magnetic yokes 563, 466 in particular in the regions near the molding chamber 472 may have any shape.
  • the procedure for magnetizing and compacting or compressing the powder 495 carried out with the apparatus 560 may be as follows :
  • the powder 495 is filled into a molding chamber 472.

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Abstract

It is described an apparatus (460) and a method for manufacturing a permanent magnet (250, 350). The apparatus (460) comprises (a) a mold (470) having a molding chamber (472) for receiving a powder of a permanent magnet material (495); (b) a first magnetic device (461) and a second magnetic device (464) for generating a magnetic flux for magnetizing the powder being accommodated within the molding chamber; (c) a die for compacting the powder being accommodated within the molding chamber; and (d) a magnetic element (480) for spatially guiding and/or modifying the magnetic flux. The magnetic element is located and movably supported in a region extending between the first magnetic device and the second magnetic device such that in a first position (480a) there is given a first spatial magnetic flux distribution and in a second position (480b) there is given a second spatial magnetic flux distribution being different from the first spatial magnetic flux distribution. Further described is a magnet (350) produced with the described method and an electromechanical transducer (140) as well as a wind turbine (100) comprising such a magnet (350).

Description

DESCRIPTION
Manufacturing flux focused magnet using a changing
magnetization
Field of invention
The present invention relates to an apparatus and to a method for manufacturing a permanent magnet. Further, the present invention relates to a magnet being produced with the
described method and to an electromechanical transducer and a wind turbine comprising at least one of such a magnet.
Art Background
Permanent magnetic materials are used in a plurality of different fields of application. Probably the technically and economically most important field of applications are
electromechanical transducers, i.e. electric motors and electric generators. An electric motor being equipped with at least one permanent magnet (PM) converts electric energy into mechanical energy by producing a temporary varying magnetic field by means of windings or coils. This temporary varying magnetic field interacts with the magnetic field of the PM resulting e.g. in a rotational movement of a rotor assembly with respect to a stator assembly of the electric motor. In a physically complementary manner, an electric generator converts mechanical energy into electric energy.
An electric generator is a core component of any power plant for generating electric energy. This holds true for power plants which directly capture mechanical energy, e.g.
hydroelectric power installations, tidal power installations, and wind power installations also denominated wind turbines. However, this also holds true for power plants which (i) first use chemical energy e.g. from burning fossil fuel or from nuclear energy in order to generate thermal energy and which (ii) second convert the generated thermal energy into mechanical energy by means of appropriate thermodynamic processes .
The efficiency of an electric generator is probably the most important factor for optimizing the production of electric energy. For a PM electric generator it is essential that the magnetic flux produced by the permanent magnets (PMs) is strong. This can probably best be achieved with sintered rare earth magnets, e.g. using a FeNdB material composition.
However, also the spatial magnetic field distribution
produced by PM devices or PM pieces has an impact on the generator efficiency. In the latter case it is often of advantage when PM devices are used which have a non-uniform magnetic domain alignment pattern resulting in an
intentionally inhomogeneous magnetic field strength or magnetic flux density in particular in an air gap between a rotor assembly and a stator assembly.
It is known to configure a non-uniform magnetic domain alignment pattern in PM devices in order to achieve a so called "magnetic flux focusing". WO 2012/141932 A2 discloses PM magnet arrangements where differently magnetized PM devices are combined such that a "magnetic focusing" is achieved. EP 3 276 642 A1 discloses a sintered rare earth PM having a focusing magnetic alignment pattern with a single piece PM body. EP 2 762 838 A2 discloses apparatuses and methods for manufacturing PMs, wherein during a sintering process an non-uniform external magnetic field is applied in order to magnetize different regions of a PM in different directions .
Magnetic fluxing offers a large increase in the airgap flux density leading to higher torque/power of electromechanical transducers such as electric generators for direct-drive wind turbines. Therefore, already in the near future there will be an increasing demand for Flux Focusing Permanent Magnet (FFPM) pieces/devices. However, the desired strength or degree of magnetic focusing, which in analogy to optics may be characterized by a so called (magnetic) focal length, depends on the specific field of application. Hence,
manufacturing different types of FFPM pieces is costly because for FFPM pieces having different focal lengths different apparatuses for compacting, magnetizing, and sintering magnetic power are needed.
There may be a need for facilitating a manufacture of Flux Focusing Permanent Magnet (FFPM) pieces.
Summary of the Invention
This need may be met by the subject matter according to the independent claims. Advantageous embodiments of the present invention are described by the dependent claims.
According to a first aspect of the invention there is provided an apparatus for manufacturing a permanent magnet, in particular a sintered permanent magnet. The provided apparatus comprises (a) a mold having a molding chamber for receiving a powder of a permanent magnet material; (b) a first magnetic device and a second magnetic device for generating a magnetic flux for magnetizing the powder being accommodated within the molding chamber; (c) a die for compacting the powder being accommodated within the molding chamber; and (d) a magnetic element for spatially guiding and/or modifying the magnetic flux. The magnetic element is located and movably supported in a region extending between the first magnetic device and the second magnetic device such that in a first position of the magnetic element there is given a first spatial magnetic flux distribution within at least the molding chamber and in a second position of the magnetic element there is given a second spatial magnetic flux distribution within at least the molding chamber. The second spatial magnetic flux distribution is different from the first spatial magnetic flux distribution.
The described apparatus is based on the idea that when placing, during a powder compacting and magnetizing
procedure, the magnetic element in at least two different positions, the spatial magnetic flux distribution changes during these processes. Specifically, the spatial magnetic flux distribution changes in such a manner that the powder is subjected to at least one spatial nonhomogeneous or
inhomogeneous distribution of magnetic flux lines. This means that a magnetized compacted block resulting from the
magnetizing and compacting steps will not exhibit a
homogeneous magnetization with a parallel orientation of magnetic domain alignment directions. Instead, there will be produced at least within some regions of the magnetized compacted block a spread angular distribution of magnetic domain alignment directions. This spread angular distribution may result in a focused magnetization of a (sintered)
permanent magnet (PM) piece which will be obtained from the magnetized compacted block by means of a known sintering procedure within an appropriate sintering oven or chamber. Thereby, the degree of focusing and in particular the
location of a focal point or focal region of the (sintered)
PM (piece) depends on the positions the magnetic element has been brought to during the compacting and magnetizing
procedure (s) . This means that, by a proper selection of the positions where the magnetic element is brought to, the magnetic focusing characteristic of the resulting (sintered) and magnetized block can be adjusted.
With the described apparatus different types of Flux Focusing Permanent Magnet (FFPM) pieces can be produced. Specifically, for producing a first type of FFPM with a first magnetic flux focusing characteristic the magnetic element is brought to a first set of at least two positions and for producing a second type of FFPM pieces with a second magnetic flux focusing characteristic the magnetic element is brought to a second set of at least two positions being spatially
different from the positions of the first set.
It is mentioned that the magnetic flux focusing
characteristics may not only be defined by the locations of the positions of the magnetic element but also by the time durations the magnetic element is present within the
respective position. Further, the magnetic flux focusing characteristics may also be determined by the relative timing between adopting these positions and the progress of the magnetizing and compacting procedures.
It is further mentioned that a magnetic flux focusing
characteristic of the magnetized compacted block typically at least partially corresponds to the magnetic focusing
characteristic of a sintered permanent magnet (PM) piece which will be produced from the sintered magnetized compacted block by means of know post processing steps. Such steps may include e.g. a proper shaping e.g. by means of a removal of sintered magnetic material and/or a surface finishing.
Furthermore it is mentioned that the steps of magnetizing and compacting are typically carried out simultaneously or at least with a certain overlap in time.
Furthermore it is mentioned that magnetizing the powder by means of the magnetic flux may be associated with an
alignment of the magnetic domains.
According to a further embodiment of the invention the apparatus further comprises an actuator mechanism for
changing the position of the magnetic element. This may provide the advantage that the position of the magnetic element can be controlled precisely and in an automated manner .
The actuator mechanism may be configured for moving the magnetic element in a continuous manner. However, in certain applications the actuator mechanism may drive the magnetic element in a stepwise manner to and from discrete positions.
According to a further embodiment of the invention the first magnetic device and the second magnetic device are configured to generate, in a virtual absence of the magnetic element, a magnetic flux pattern which comprises, at least within the molding chamber, a spread angular distribution of magnetic flux lines. This may provide the advantage that even in the absence of the magnetic element a FFPM respectively a
magnetized compacted block having a focused pattern of magnetic alignment directions can be produced. This means that (the presence of) the movable magnetic element will (only) modify the focusing magnetic flux pattern.
In case the spread angular distribution of magnetic flux lines generated solely by the (at least) two magnetic devices is stationary in time it can be seen as to represent a base magnetic flux pattern. Hence, the time varying magnetic flux generated by the moving magnetic element can be seen as to represent an offset to the base magnetic flux pattern.
According to a further embodiment of the invention at least one of the two magnetic devices comprises (a) an electro magnetic coil for producing the magnetic flux and (b) a magnetic yoke for guiding and/or for shaping the magnetic flux being produced by the electromagnetic coil.
Supporting the electromagnetic coil in producing the magnetic flux by providing a proper magnetic yoke may provide the advantage that the magnetic flux (density) , at least within selected regions of the molding chamber, can be increased significantly. Further, by designing the shape and/or the geometry of the magnetic yoke in a proper manner a desired (base) spread angular distribution of magnetic flux lines can be produced which yields a desired focused flux base
magnetization design. The magnetic yoke, which may also be denominated a pole piece, may be made from a ferromagnetic material, in
particular from iron or cobalt iron for obtaining a high magnetic saturation. By contrast thereto, the mold may be made from a non-magnetic and in particular from a non
ferromagnetic material. A (currently) preferred material is stainless steel. However, also other mold materials may be used provided that are mechanical stiff.
According to an embodiment of the invention the magnetic element is supported in such a manner that it is continuously movable along a predefined trajectory. This may provide the advantage that the positions the magnetic element can be and is brought to can be spatially defined in a highly precise manner. This may result in a high accuracy of the
respectively produced magnetic focusing characteristic.
The trajectory can be predefined by any mechanical guiding structure comprising e.g. a guide bar or a guide rail.
Preferably, the guiding structure is made from a non-magnetic material such as e.g. stainless steel in order not to disturb the magnetic flux.
It is mentioned that in a "quasi-continuous consideration" a continuous movement corresponds to a sequential movement to a plurality of positions with a small distance between
neighboring positions. The continuous movement can even be seen as a discrete movement to and from an infinite number of positions wherein the distance between two neighboring positions is zero.
According to a further embodiment of the invention a length of the predefined trajectory determines a magnetic focal distance of the permanent magnet.
By moving the magnet along a comparatively long trajectory there will be generated an angular distribution of magnetic domain alignment directions which has a comparatively large or wide spread. Hence, the magnetic focusing will be
comparatively strong and, as a consequence, the focal
distance will be comparatively small.
It is mentioned that the magnetic focusing can be seen as an analogon to an optical focusing. This means that an angular spread of magnetic domain alignment directions along one direction, which is sufficient for most applications of a FFPM, results in a one dimensional (ID) magnetic flux
focusing yielding a linearly extended focal region. Such a magnetic focusing corresponds to an optical focusing by means of a cylindrical optical lens. Alternatively, (in a temporal average) the magnetic flux within the molding chamber may have an angular spread along two directions being
perpendicular to each other (and both being parallel to a main surface of the PM) . This results in a two dimensional (2D) magnetic flux focusing which yields a magnetic focal point or a (small) where the magnetic flux density is
focused. Such a magnetic focusing corresponds to an optical focusing by means of a spherical optical lens.
It is mentioned that the length may not necessarily be the maximum possible length allowed e.g. by the above identified guiding structure. The length may rather be the actual length the magnetic element is moved during a certain magnetizing and compacting procedure. This means that depending on the actual length with respect to the maximum possible length the magnetic flux focusing characteristic can be adjusted
properly. Hence, different types of FFPM can be manufactured simply by changing the actual trajectory length the magnetic element is travelling.
According to a further embodiment of the invention the predefined trajectory is a path along a curved shape, in particular along a circular arc. This may provide the
advantage that the magnetic element travels along a
geometrically very simple path. Hence, a resulting magnetic flux focusing characteristic can be predicted in an easy and precise manner. This facilitates the magnetic design of FFPM pieces .
According to a further embodiment of the invention the first magnetic device has a first magnetic yoke and the second magnetic device has a second magnetic yoke. With regard to the molding chamber the first magnetic yoke and the second magnetic yoke are located at opposing sides. Further, the first magnetic yoke has a first outer yoke surface facing the molding chamber and the second magnetic yoke has a second outer yoke surface facing the molding chamber. Furthermore, the first outer yoke surface is concave and the second outer yoke surface is convex or planar.
The described spatial design of the two magnetic yokes may provide the advantage that a proper and well defined spread angular distribution of magnetic flux lines within the molding chamber can be generated in an easy and effective manner. Depending on the specific application the bending of the outer yoke surfaces may be regular, i.e. without any corners and edges ("lumps and bumps"), or may be irregular.
According to a further embodiment of the invention the first outer yoke surface has a first radius and the second outer yoke surface has a second radius being different from the first radius. This may provide the advantage that a higher alignment angle of the magnetic domain alignment directions at and with regard to side edges of the magnetized compacted block can be realized.
In some embodiments the (at least one) magnetic element comprises or is made from a magnetic material, in particular from a ferromagnetic material. This may provide the advantage that with regard to the base magnetic flux pattern caused (solely) by the magnetic devices the (wanted) temporal magnetic perturbation caused by the moving magnetic element will be strong. Hence, higher alignment angles of the magnetic domain alignment directions at and with regard to side edges of the magnetized compacted block can be realized.
The ferromagnetic material may be iron or a composition of iron and cobalt. It is mentioned that in embodiments
comprising (at least) two magnetic elements of cause all magnetic elements may comprise or may be made from such a magnetic material.
According to a further embodiment of the invention the apparatus further comprises a further magnetic element being supported in such a manner that it is continuously movable along a further predefined trajectory. This may provide the advantage that the magnetization procedure can be made more effective with regard to the magnetization strength.
Alternatively or in combination the magnetization procedure can be speeded up because (at least) two magnetic elements are "working" simultaneously.
According to a further embodiment of the invention, with respect to a magnetic symmetry axis of the apparatus, the predefined trajectory and the further predefined trajectory are symmetric with respect to each other. This may provide the advantage that FFPMs, which have a symmetric spread angular distribution of magnetic domain alignment directions, can be manufactured in an easy and reliable manner.
In this document the term "magnetic symmetry axis" of the apparatus may particularly refer to a spatial distribution of magnetic field lines which are produced by means of the two magnetic devices. This holds true for (a) a virtual absence of the two magnetic elements or (b) an operational state of the apparatus where the two magnetic elements are equally spaced apart from this magnetic symmetry axis.
According to a further embodiment of the invention the predefined trajectory is a path along a curved or linear shape and the further predefined trajectory is a further path along a further curved or linear shape. For the movement at least one of the two magnetic elements the respective curved shape may be a circular arc. This may provide the advantage that both magnetic elements may travel along a geometrically very simple path. Hence, a resulting magnetic flux focusing characteristic can be predicted in an easy and precise manner. This facilitates the magnetic design of FFPM pieces.
According to a further embodiment of the invention the first magnetic device has a first magnetic yoke and the second magnetic device has a second magnetic yoke. Further, with regard to the molding chamber, the first magnetic yoke and the second magnetic yoke are located at opposing sides.
Furthermore, the first magnetic yoke has a first outer yoke surface facing the molding chamber and the second magnetic yoke has a second outer yoke surface facing the molding chamber. The first outer yoke surface is planar and the second outer yoke surface is convex.
Also for the embodiments described above having at least two magnetic elements the described spatial design of the two magnetic yokes may provide the advantage that a proper and well defined spread angular distribution of magnetic flux lines within the molding chamber can be generated in an easy and effective manner. Depending on the specific application the bending of the convex second outer yoke surface may be regular, i.e. without any corners and edges ("lumps and bumps"), or may be irregular.
According to a further aspect of the invention there is provided a method for manufacturing a permanent magnet, in particular a sintered permanent magnet. The provided method comprises (a) filling a powder of permanent magnet material into a molding chamber of a mold; (b) generating a magnetic flux for magnetizing the powder being accommodated within the molding chamber by means of a first magnetic device and a second magnetic device; (c) compacting the powder being accommodated within the molding chamber by means of a die; (d) moving, within a region extending between the first magnetic device and the second magnetic device, at least one magnetic element, which is spatially guiding and/or modifying the generated magnetic flux, from a first position to at least a second position. Thereby, in the first position of the at least one magnetic element there is given a first spatial magnetic flux distribution within at least the molding chamber and in the second position of the at least one magnetic element there is given a second spatial magnetic flux distribution within at least the molding chamber. The second spatial magnetic flux distribution is different from the first spatial magnetic flux distribution.
Also the described method is based on the idea that when moving the at least one magnetic element the spatial magnetic flux distribution may change in such a manner that a FFPM can be manufactured in an effective and flexible manner. In this respect flexible means that depending on the spatial movement of the at least one magnetic element different patterns of magnetic domain alignment directions within the magnetized compacted block can be realized.
According to an embodiment of the invention moving the at least one magnetic element comprises (a) a first movement along a predefined trajectory in a first direction and (b) a second movement along the predefined trajectory in a second direction being opposite to the first direction. This means in descriptive words that during the magnetizing and
compacting procedure there is a forth and back movement of the at least one magnetic element. This may provide the advantage that not only one but several magnetization cycles can be realized with the at least one magnetic element. This may improve the accuracy and the strength of the magnetic flux focusing characteristic of a PM which can be produced from the magnetized compacted block.
In preferred applications of the described method the
permanent magnet material comprises a rare earth material, in particular NdFeB. This may provide the advantage that very strong FFPMs can be manufactured.
In this respect it is mentioned that other compositions of the permanent magnet material may include ferrite and/or SmCo .
According to a further aspect of the invention there is provided a permanent magnet, in particular a permanent sintered magnet, being produced by carrying out a method as described above.
According to a further aspect of the invention there is provided an electromechanical transducer, in particular an electric generator. The provided electromechanical transducer comprises (a) a stator assembly, and (b) a rotor assembly.
The rotor assembly comprises (bl) a support structure and (b2) at least one permanent magnet as described above. The permanent magnet is mounted to the support structure.
The provided electromechanical transducer is based on the idea that it can be built up with a rotor assembly comprising at least one (sintered) FFPM which exhibits a proper magnetic flux focusing. Due to the proper magnetic flux focusing the efficiency of the electric generator with regard to the amount of electric power, which can be produced with a certain amount of available "mechanical" power, can be improved .
According to a further aspect of the invention there is provided a wind turbine for generating electrical power. The provided the wind turbine comprises (a) a tower; (b) a wind rotor, which is arranged at a top portion of the tower and which comprises at least one blade; and (c) an electro mechanical transducer as described above. The electro
mechanical transducer is mechanically coupled with the wind rotor . The provided wind turbine, also denominated a wind energy installation, is based on the idea that the above described electromechanical transducer allows to improve the energy conversion efficiency of a wind turbine. This may contribute for improving the attractiveness of wind turbine technology for regenerative power production as compared to other technologies such as solar 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 as to be disclosed with this document.
The aspects defined above and further aspects of the present 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 Drawing
Figure 1 shows a wind turbine in accordance with an
embodiment of the present invention.
Figure 2 shows in a schematic representation the generator of the wind turbine of Figure 1. Figure 3 shows a Flux Focusing Permanent Magnet (FFPM) produced in accordance with an embodiment of the invention .
Figure 4 shows an apparatus for manufacturing a sintered
permanent magnet with one movable magnetic element.
Figure 5 shows an apparatus for manufacturing a sintered
permanent magnet with two movable magnetic elements.
Detailed Description
The illustration in the drawing is schematic. It is noted that in different figures, similar or identical elements or features are provided with the same reference signs or with reference signs, which are different from the corresponding reference signs only within the first digit. In order to avoid unnecessary repetitions elements or features which have already been elucidated with respect to a previously
described embodiment are not elucidated again at a later position of the description.
Figure 1 shows in accordance with an embodiment of the invention a wind turbine 100, which comprises a tower 120 being mounted on a non-depicted fundament. On top of the tower 120 there is arranged a nacelle 122. Further, there is provided a yaw angle adjustment device 121 which is capable of rotating the nacelle 122 around a non-depicted vertical axis being aligned with the longitudinal extension of the tower 120. By controlling the yaw angle adjustment device 121 in an appropriate manner it can be made sure that during a normal operation of the wind turbine 100 the nacelle 122 is always properly aligned with the wind direction.
The wind turbine 100 further comprises a wind rotor 110 having three blades 114. In the perspective of Figure 1 only two blades 114 are visible. The rotor 110 is rotatable around a rotational axis 110a. The blades 114, which are mounted at a hub 112, extend radially with respect to the rotational axis 110a.
In between the hub 112 and a blade 114 there is respectively provided a blade angle adjustment device 116 in order to adjust the blade pitch angle of each blade 114 by rotating the respective blade 114 around a non-depicted axis being aligned substantially parallel with the longitudinal
extension of the respective blade 114. By controlling the blade angle adjustment device 116 the blade pitch angle of the respective blade 114 can be adjusted in such a manner that a maximum wind power can be retrieved from the available mechanical power of the wind driving the wind rotor 110.
As can be seen from Figure 1, within the nacelle 122 there is provided an optional gear box 124. The gear box 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 in a known manner to an electromechanical transducer 130. The electromechanical transducer is a generator 130. A wind turbine without a gear box is called a Direct Drive (DD) wind turbine .
Further, 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 for instance in case of emergency .
The wind turbine 100 further comprises a control system 143 for operating the wind turbine 100 in a highly efficient manner. Apart from controlling for instance the yaw angle adjustment device 121 the depicted control system 153 is also used for adjusting the blade pitch angle of the rotor blades 114 in an optimized manner.
The generator 130 comprises a stator assembly 135 and a rotor assembly 140. In the embodiment described here the generator 130 is realized in a so called "inner stator - outer rotor" configuration. This means that the rotor assembly 140
surrounds the stator assembly 135 and that non-depicted permanent magnets or PM assemblies of the rotor assembly 140 travel around an arrangement of a plurality of non-depicted coils of the inner stator assembly 135 which coils produce an induced current resulting from picking up a time varying magnetic flux from the traveling permanent magnets.
According to the embodiment described here each permanent magnet (PM) assembly comprises at least three sintered permanent magnet pieces which are made from a NdFeB material composition .
Figure 2 shows in a cross sectional view a schematic
representation of the generator 130. The generator 130 comprises a stator assembly 135. The stator assembly 135 comprises a stator support structure 237 comprising a stack of a plurality of lamination sheets and a plurality of stator windings 239 being accommodated within the stator support structure 237. The windings 239 are interconnected in a known manner by means of non-depicted electrical connections.
A rotor assembly 140 of the generator 130, which is separated from the stator assembly 135 by an air gap ag, comprises a rotor support structure 242 providing the mechanical base for mounting a plurality of sintered permanent magnets 250. The sintered magnets are Flux Focusing Permanent Magnets (FFPM) which, when designed with a proper magnetic focal length, allow to increase the magnetic flux density within the airgap ag. In Figure 2 the rotational axis of the rotor assembly 140 is denominated with reference numeral 230a.
In the exemplary embodiment described here at each angular position of the rotor assembly 140 there are arranged three sintered FFPMs arranged next to each other. It is mentioned that in Figure 2 only three sintered FFPMs 250 (being
assigned to one angular position) are depicted for the sake of ease of illustration. In reality, depending on the
dimension of the generator 130, a plurality of FFPMs 250 are mounted to the rotor support structure 242. The FFPMs 250 are preferably arranged in a matrix like structure around a curved surface area of the support structure 242 having a basically cylindrical geometry around the generator axis 240a.
As can be seen from Figure 2, the sintered FFPMs 250 are not mounted directly to the rotor support structure 242. Instead, there is provided a back plate 244 made from a ferromagnetic material, e.g. iron. The back plate 244 is provided in order to ensure a proper guidance of magnetic flux. This
significantly reduces in a beneficial manner the intensity of magnetic stray fields.
Figure 3 shows a FFPM 350 produced in accordance with an embodiment of the invention. The FFPM 350 is magnetized in such a manner that there is given a spread angular
distribution of magnetic domain alignment directions 352. According to the embodiment described here each magnetic domain alignment direction 352 follows a straight
magnetization line. The straight lines are angled or inclined with respect to each other in a fan like manner.
Specifically, the spread angular distribution of the straight magnetization lines produces, in the region above a main surface 350a of the FFPM 350, a focal point 354 being
characterized by a local maximum of the magnetic field respectively the magnetic flux density produced by the FFPM 350. The distance between the front surface of the FFPM 350 and the focal point 354 is the magnetic focal distance fd.
According to the exemplary embodiment described here the depicted magnetic domain alignment pattern is symmetric with respect to a symmetry axis 354a. In this document the
symmetry axis 354a is also denominated magnetic axis. The magnetic axis 354a is a normal axis to the main surface 350a, which runs through the focal point 354.
Figure 4 shows an apparatus 460 for manufacturing a block in the form of pressed magnet powder that can be sintered in an oven and become a sintered permanent magnet. Specifically, the apparatus 460 is used for compacting and magnetizing a powder of magnetic material 495. A subsequent sintering of a resulting magnetized compacted block is carried out in a non- depicted sintering oven.
The apparatus 460 comprises a mold 470 within which a molding chamber 472 is formed. The molding chamber 472 can be closed by at least one non depicted die, which is also used for compacting the powder 495. The movement of the at least one die is along a direction being perpendicular to the plane of drawing .
The apparatus 460 further comprises means for producing a magnetic flux which is applied to the compacted powder 495. These magnetic flux production means include a first magnetic device 461 and the second magnetic device 464. In the
embodiment shown in Figure 4, the first magnetic device 461 produces a magnetic North pole N and the second magnetic device 464 produces a magnetic South Pole S. In accordance with known apparatuses the first magnetic device 461
comprises (i) a first electromagnetic coil 462 for generating a magnetic flux and (ii) a first magnetic yoke 463 for guiding and/or for shaping the magnetic flux (lines) being present within the molding chamber 472. Correspondingly, the second magnetic device 464 comprises (i) a second
electromagnetic coil 465 and (ii) a second magnetic yoke 466.
According to the exemplary embodiment described here the first magnetic yoke 463 being assigned to the North pole and the second magnetic yoke 466 being assigned to the South pole have a different geometry. Specifically, the bending radii of the outer surfaces of the two magnetic yokes 463, 466 is different from each other. The first magnetic yoke 463 has a first outer yoke surface 463a facing the molding chamber 472. The first outer yoke surface 463a is, with respect to the location of the molding chamber 472 a convex surface having a bending radius R1. The second magnetic yoke 466 has a second outer yoke surface 466a facing the molding chamber 472. The second outer yoke surface 466a is, with respect to the location of the molding chamber 472 a concave surface having a bending radius R2. As can be seen from Figure 4, R1 is significantly larger than R2.
The difference in geometry of the magnetic yokes 463, 466 has the effect that within the molding chamber 472 there will be provided an inhomogeneous magnetic field respectively
magnetic flux which results in an inhomogeneous magnetization of the compacted powder 495 sintered block. This
inhomogeneous magnetization may result in a spread angular distribution of magnetic domain alignment directions 352 as shown in Figure 3.
However, the apparatus 460 comprises further means for increasing the inhomogeneity of the magnetic flux within the molding chamber. Thereby, a FFPM can be produced which has a short focal distance.
Specifically, the apparatus 460 further comprises a magnetic element 480 which can travel along a predefined trajectory 481. The spatial course of the trajectory 481 is defined by a non-depicted guiding structure. According to the exemplary embodiment described here the predefined trajectory is an arc shaped curved path 481 which runs parallel to the concave surface 463a of the first magnetic yoke 463.
As can be seen from Figure 4, during a compacting and
magnetizing process the magnetic element 480 can be moved forth and back between a first position 480a and a second position 480b. The corresponding movement is actuated by means of a schematically depicted actuator mechanism 482.
In should be understood that when changing the (curved) distance respectively the spacing between the two positions 480a, 480b the inhomogeneity of the pattern of magnetic flux lines within the molding chamber 472 changes. This has an effect on the focal distance of a FFPM being produced (a) with the described apparatus 460 and (b) with a sintering oven within which the magnetized compacted block produced with the apparatus 460 is further processed. Specifically, the larger the spacing between the two positions 480a, 480b is the larger will be the inhomogeneity and the smaller will be the focal distance.
Figure 5 shows an apparatus 560 for manufacturing a sintered permanent magnet in accordance with another embodiment of the invention. The apparatus 560 has significant structural similarities with the apparatus 460. Specifically, the second magnetic device, which in this embodiment produces the magnetic South Pole for the magnetic powder 495, and the mold 470 are the same as in the apparatus 460.
By contrast to the apparatus 460 shown in Figure 4, the apparatus 560 comprises not only one but two magnetic
elements, a first magnetic element 580 and a further or second magnetic element 590. During operation of the
apparatus 560 both magnetic elements 580, 590 move along a linear direction. Specifically, a first trajectory 581 is assigned to the first magnetic element 580 and a further or second trajectory 591 is assigned to the second magnetic element 590. The first trajectory 581 extends between a first position 580a of the first magnetic element 580 (depicted with full lines) and a second position 580b of the first magnetic element 580 (depicted with dashed lines) .
Accordingly, the second trajectory 591 extends between a first position 590a of the second magnetic element 590 (depicted with full lines) and a second position 590b of the second magnetic element 590 (depicted with dashed lines) .
As can be taken from Figure 5, a first magnetic device 561 producing the North Pole (for the magnetic powder 495) comprises a first electromagnetic coil 562 and a first magnetic yoke 563. By contrast to the apparatus 460 shown in Figure 4 the first magnetic yoke 563 comprises a planar first outer yoke surface 563a.
According to the exemplary embodiment described here the apparatus 560 is operated in a symmetric manner. Thereby, the "symmetry" relates to the magnetic field (line) pattern which is given between the two magnetic devices 561 and 464.
Specifically, this pattern exhibits an axial symmetry with regard to a magnetic symmetry axis 560a. Although the
magnetic field pattern changes with a movement of the two magnetic elements 580, 590, there is always given a symmetry with regard to the axis 560a. The "symmetry conservation" is given because in this embodiment the movement of the two magnetic elements 580, 590 is always symmetric. This means that at any instance of time a first distance between the first magnetic element 580 and the symmetry axis 560a is the same as a second distance between the second magnetic element 590 and the symmetry axis 560a. Hence, not only the magnetic field line pattern generated by the two magnetic devices 561 and 464 is symmetric but also the "perturbation" to this magnetic field line pattern which is caused by the magnetic elements 580, 590 which spatially move in a symmetric manner.
It is mentioned that in other embodiments two magnetic elements move along a non-linear path. Such a non-linear path may have any other curved shape such as a circular shape as shown in Figure 4. Further, the shape of the magnetic yokes 563, 466 in particular in the regions near the molding chamber 472 may have any shape. The procedure for magnetizing and compacting or compressing the powder 495 carried out with the apparatus 560 may be as follows :
(1) The powder 495 is filled into a molding chamber 472.
(2) Two non-depicted dies acting as a pressing tool are moved into the plane of drawing. Thereby, a lid is formed.
(3) A magnetic field is generated by means of the two
magnetic devices 561 and 464.
(4) The two magnetic elements 580, 590 are moved outwards.
(5) When a required pressure has been applied to the magnetic powder 495 either a lower part or an upper part of the pressing tool will press out a magnet block consisting of the compacted powder 495.
(6) The magnet block is now ready for optional isostatic pressing and for undergoing a usual sintering procedure.
Although the embodiments described above are typically used for manufacturing sintered magnets it is mentioned that with the described apparatuses also bonded magnets or other magnets produced from powders without sintering can be manufactured .
It should be noted that the term "comprising" does not exclude other elements or steps and the use of articles "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 should not be construed as limiting the scope of the claims.

Claims

CLAIMS :
1. An apparatus (460; 560) for manufacturing a permanent magnet (250, 350), in particular a sintered permanent magnet (250, 350), the apparatus (460; 560) comprising
a mold (470) having a molding chamber (472) for
receiving a powder of a permanent magnet material (495);
a first magnetic device (461; 561) and a second magnetic device (464) for generating a magnetic flux for magnetizing the powder (495) being accommodated within the molding chamber (472);
a die for compacting the powder (495) being accommodated within the molding chamber (472); and
a magnetic element (480; 580, 590) for spatially guiding and/or modifying the magnetic flux; wherein
the magnetic element (480; 580, 590) is located and movably supported in a region extending between the first magnetic device (461; 561) and the second magnetic device (464) such that
in a first position (480a; 580a, 590a) of the magnetic element (480; 580, 590) there is given a first spatial magnetic flux distribution within at least the molding chamber (472) and in a second position (480b; 580b, 590b) of the magnetic element (480; 580, 590) there is given a second spatial magnetic flux distribution within at least the molding chamber (472), wherein the second spatial magnetic flux distribution is different from the first spatial magnetic flux distribution.
2. The apparatus (460; 560) as set forth in the preceding claim, further comprising
an actuator mechanism (482) for changing the position of the magnetic element (480) .
3. The apparatus (460; 560) as set forth in any one of the preceding claims, wherein
the first magnetic device (461; 561) and the second magnetic device (464) are configured to generate, in a virtual absence of the magnetic element (480; 580, 590), a magnetic flux pattern which comprises, at least within the molding chamber (472), a spread angular distribution of magnetic flux lines.
4. The apparatus (460) as set forth in any one of the preceding claims, wherein
at least one of the two magnetic devices (461, 464; 561) comprises
an electromagnetic coil (462, 465; 562) for producing the magnetic flux and
a magnetic yoke (463, 466; 563) for guiding and/or for shaping the magnetic flux being produced by the electro magnetic coil (462, 466; 562).
5. The apparatus (460; 560) as set forth in any one of the preceding claims, wherein
the magnetic element (480; 580, 590) is supported in such a manner that it is continuously movable along a predefined trajectory (481; 581, 591).
6. The apparatus (460; 560) as set forth in the preceding claim, wherein
a length of the predefined trajectory (481; 581, 591) determines a magnetic focal distance (fd) of the permanent magnet (250 , 350 ) .
7. The apparatus (460) as set forth in any one of the two preceding claims, wherein
the predefined trajectory (481) is a path along a curved shape, in particular along a circular arc.
8. The apparatus (460) as set forth in any one of the preceding claims 5 to 7, wherein
the first magnetic device (461) has a first magnetic yoke (463) and the second magnetic device (464) has a second magnetic yoke (465), with regard to the molding chamber (472) the first magnetic yoke (463) and the second magnetic yoke (466) are located at opposing sides,
the first magnetic yoke (463) has a first outer yoke surface (463a) facing the molding chamber (472) and the second magnetic yoke (466) has a second outer yoke surface (466a) facing the molding chamber (472), and
the first outer yoke surface (463a) is concave and the second outer yoke surface (466a) is convex or planar.
9. The apparatus (460) as set forth in the preceding claim, wherein
the first outer yoke surface (463a) has a first radius (Rl) and the second outer yoke surface (466a) has a second radius (R2) being different from the first radius (Rl) .
10. The apparatus (560) as set forth in any one of the preceding claims 5 to 7, further comprising
a further magnetic element (590) being supported in such a manner that it is continuously movable along a further predefined trajectory (591).
11. The apparatus (560) as set forth in the preceding claim 10, wherein
with respect to a magnetic symmetry axis (560a) of the apparatus (560) the predefined trajectory (581) and the further predefined trajectory (591) are symmetric with respect to each other.
12. The apparatus (560) as set forth in any one of the preceding claims 10 to 11, wherein
the predefined trajectory (581) is a path along a curved or linear shape and
the further predefined trajectory (591) is a further path along a further curved or linear shape.
13. The apparatus (560) as set forth in any one of the preceding claims 10 to 12, wherein the first magnetic device (561) has a first magnetic yoke (563) and the second magnetic device (464) has a second magnetic yoke (466),
with regard to the molding chamber (472) the first magnetic yoke (563) and the second magnetic yoke (466) are located at opposing sides,
the first magnetic yoke (563) has a first outer yoke surface (563a) facing the molding chamber (472) and the second magnetic yoke (466) has a second outer yoke surface (466a) facing the molding chamber (472), and
the first outer yoke surface (563a) is planar and the second outer yoke surface (466a) is convex.
14. A method for manufacturing a permanent magnet (250, 350), in particular a sintered permanent magnet (250, 350), the method comprising
filling a powder of permanent magnet material (495) into a molding chamber (472) of a mold (470);
generating a magnetic flux for magnetizing the powder (495) being accommodated within the molding chamber (472) by means of a first magnetic device (461) and a second magnetic device (464) ;
compacting the powder (495) being accommodated within the molding chamber (472) by means of a die;
moving, within a region extending between the first magnetic device (461) and the second magnetic device (464), at least one magnetic element (480), which is spatially guiding and/or modifying the generated magnetic flux, from a first position (480a) to at least a second position (480b) , wherein
in the first position (480a) of the at least one magnetic element (480) there is given a first spatial magnetic flux distribution within at least the molding chamber (472) and in the second position (480b) of the at least one magnetic element (480) there is given a second spatial magnetic flux distribution within at least the molding chamber (472), wherein the second spatial magnetic flux distribution is different from the first spatial magnetic flux distribution.
15. The method as set forth in the preceding claim, wherein moving the at least one magnetic element (480) comprises
a first movement along a predefined trajectory (481) in a first direction and
a second movement along the predefined trajectory (481) in a second direction being opposite to the first direction.
16. Permanent magnet (250, 350), in particular a permanent sintered magnet, being produced by carrying out a method as set forth in any one of the two preceding claims.
17. An electromechanical transducer (140), in particular an electric generator (130), the electromechanical transducer (130) comprising
a stator assembly (135), and
a rotor assembly (140) comprising
a support structure (242) and
at least one permanent magnet (250, 350) as set forth in the preceding claim, wherein the permanent magnet (250, 350) is mounted to the support structure (242) .
18. A wind turbine (100) for generating electrical power, the wind turbine (100) comprising
a tower (120) ;
a wind rotor (110), which is arranged at a top portion of the tower (120) and which comprises at least one blade (114); and
an electromechanical transducer (130) as set forth in the preceding claim, wherein the electromechanical transducer (130) is mechanically coupled with the wind rotor (110) .
EP19761771.5A 2019-05-10 2019-08-16 Manufacturing flux focused magnet using a changing magnetization Withdrawn EP3948904A2 (en)

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CN201910389532.1A CN111916282A (en) 2019-05-10 2019-05-10 Manufacturing flux-focused magnets using varying magnetization
PCT/EP2019/072048 WO2019207173A2 (en) 2019-05-10 2019-08-16 Manufacturing flux focused magnet using a changing magnetization

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EP4026631A1 (en) * 2021-01-07 2022-07-13 Siemens Gamesa Renewable Energy A/S Apparatus and method for manufacturing a monolithic permanent magnet with a focused and a parallel magnetic flux region

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US6432158B1 (en) * 1999-10-25 2002-08-13 Sumitomo Special Metals Co., Ltd. Method and apparatus for producing compact of rare earth alloy powder and rare earth magnet
DE102005043874A1 (en) * 2005-09-14 2007-03-22 Mitsubishi Denki K.K. Sintered ring magnet useful in electric motors comprises a stack of annular powder preforms that are sintered together and has a projection or recess at one or both ends
BR112013026357A2 (en) 2011-04-13 2016-12-27 Boulder Wind Power Inc flux focusing arrangement for permanent magnets, methods for making these arrangements, and machines that include these arrangements
EP2722855A1 (en) * 2012-10-19 2014-04-23 Siemens Aktiengesellschaft Nd-Fe-B permanent magnet without Dysprosium, rotor assembly, electromechanical transducer, wind turbine
US9312057B2 (en) 2013-01-30 2016-04-12 Arnold Magnetic Technologies Ag Contoured-field magnets
DE102014105172B4 (en) * 2014-04-11 2023-06-15 Vacuumschmelze Gmbh & Co. Kg PROCESS FOR THE SIMULTANEOUS MANUFACTURE OF AT LEAST TWO PERMANENT MAGNETS
CN111276310A (en) 2015-03-24 2020-06-12 日东电工株式会社 Sintered body for forming rare earth magnet and rare earth sintered magnet

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