PERMANENT MAGNET MODULE FOR A PERMANENT MAGNET MACHINE

Abstract

A method of manufacturing a permanent magnet module for a permanent magnet machine includes the steps of: providing at least a permanent magnet, manufacturing a cover for covering the permanent magnet, the cover including a stainless steel, wherein the cover includes at least a top side and two lateral sides, the magnetic permeability of the top side being higher than the magnetic permeability of the lateral sides, the lateral sides being respectively attached to a first and a second edge of the top side, the lateral sides being angled with respect to the top side, attaching the cover to the permanent magnet.

Claims

1. A method of manufacturing a permanent magnet module for a permanent magnet machine, the method comprising: providing at least a permanent magnet; manufacturing a cover for covering the permanent magnet, the cover comprising a stainless steel, wherein the cover includes at least a top side and two lateral sides, a magnetic permeability of the top side being higher than a magnetic permeability of the two lateral sides, the two lateral sides being respectively attached to a first edge and a second edge of the top side, the two lateral sides being angled with respect to the top side; and attaching the cover to the permanent magnet; wherein the top side includes at least a first stainless-steel phase and the two lateral sides include at least a second stainless-steel phase.

2. The method according to claim 1, wherein the manufacturing the cover comprises: manufacturing a first sheet comprising the first stainless-steel and having two main longitudinal edges, manufacturing a second sheet and a third sheet comprising the second stainless-steel, attaching the second sheet and the third sheet to the two main longitudinal edges, respectively, to obtain an assembly sheet, cutting at least a semifinished product from the assembly sheet, the semifinished product including a portion of the first sheet, a portion of the second sheet and a portion of the third sheet, bending the portion of the second sheet and the portion of the third sheet with respect to the portion of the first sheet for deriving the cover from the semifinished product so that the portion of the first sheet corresponds to the top side and the portions of the second sheet and the third sheet respectively correspond to the lateral sides.

3. The method according to claim 2, wherein the second sheet and the third sheet are attached to the two main longitudinal edges by welding.

4. The method according to claim 1, wherein the manufacturing the cover comprises: manufacturing a semifinished sheet comprising the second stainless steel, deforming locally the semifinished sheet along a deformation direction for transforming the second stainless steel into the first stainless steel to obtain an assembly sheet having a first sheet comprising the first stainless-steel and a second sheet and a third sheet comprising the second stainless-steel, the second sheet and the third sheet being provided along two respective main longitudinal edges of the first sheet, cutting at least a semifinished product from the assembly sheet, the semifinished product including a portion of the first sheet a portion of the second sheet and a portion of the third sheet, bending the portion of the second sheet and the portion of the third sheet with respect to the portion of the first sheet for deriving the cover from the semifinished product so that the portion of the first sheet corresponds to the top side and the portions of the second sheet and the third sheet correspond to the lateral sides.

5. The method according to claim 2, wherein deforming locally the semifinished sheet comprises an operation of deep rolling or burnishing or hammer peening.

6. The method according to claim 1, wherein the manufacturing the cover comprises additive manufacturing.

7. The method according to claim 1, wherein the first stainless-steel is a magnetic stainless-steel.

8. The method according to claim 7, wherein the first stainless-steel is ferritic or martensitic.

9. The method according to claim 1, wherein the second stainless-steel is a non-magnetic stainless-steel.

10. The method according to claim 9, wherein the second stainless-steel is an austenitic stainless steel.

11. The method according to claim 1, wherein the first and the second stainless-steel are non-magnetic stainless-steels and the top side is thinner than the two lateral sides.

12. The method according to claim 1, wherein the first stainless-steel and the second stain-less-steel are magnetic stainless-steels and the top side is thicker than the two lateral sides.

Description

BRIEF DESCRIPTION

[0038] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0039] FIG. 1 shows a schematic section of a wind turbine;

[0040] FIG. 2 shows a cross-sectional view of a permanent magnet machine including a plurality of permanent magnet modules;

[0041] FIG. 3 shows a frontal circumferential view of a cover for a permanent magnet module manufactured according to the present invention;

[0042] FIG. 4 shows a frontal circumferential view of a permanent magnet module including the cover of FIG. 3;

[0043] FIG. 5 shows steps of a first embodiment of a method for manufacturing the cover of FIG. 3;

[0044] FIG. 6 shows steps of a second embodiment of a method for manufacturing the cover of FIG. 3;

[0045] FIG. 7 is a block diagram showing steps of the first embodiment of the method; and

[0046] FIG. 8 is a block diagram showing steps of the second embodiment of the method.

DETAILED DESCRIPTION

[0047] The illustrations in the drawings are schematically. It is noted that in different figures, sim-ilar or identical elements are provided with the same reference signs.

[0048] FIG. 1 shows a partial cross-sectional view of a wind turbine 1 comprising a tower 2 which is mounted on the ground at one end and a nacelle 3 which is mounted at the opposite end of the tower 2. The nacelle 3 is rotatably mounted over the tower 2. The nacelle 3 accommodates a permanent magnet machine 10, i.e. an electrical generator, which includes a permanent magnet module according to embodiments of the invention. Furthermore, the wind turbine 10 comprises a hub 5 which is rotatable about a rotor axis Y. When not dif-ferently specified, the terms axial, radial and circumferential in the following are made with reference to the rotor axis Y. The wind turbine 1 further comprises at least one blade 4 (in the embodiment of FIG. 1, the wind rotor comprises three blades 4, of which only two blades 4 are visible) mounted on the hub 5. The blades 4 extend substantially radially with respect to the rotational axis Y. The permanent magnet machine 10 includes a stator 11 and a rotor 12. The rotor 12 is rotatable with respect to the stator 11 about a longitudinal axis of the permanent magnet machine 10. The terms axial, radial and circumferential in the following are to be intended with reference to the longitudinal axis Y of rotation of the permanent magnet machine 10. In the embodiment of FIG. 1, the rotor 12 is radially exter-nal with respect the stator 11 and rotatable about the longitudinal axis Y. A circumferential air gap 15 is provided between the stator 11 and the rotor 12.

[0049] According to other possible embodiments of the present invention (not represented in the attached figures), embodiments of the present invention may be applied to any type of permanent magnet electric machines, e.g. radial, axial, etc. Embodiments of the present invention may be applied also to integral-slot electric permanent magnet machine.

[0050] A plurality of permanent magnets modules (not visible in FIG. 1) is attached to the rotor 12 by means of respective baseplates, as detailed in the following. According to other possible embodiments of the present invention (not represented in the attached figures), a plurality of permanent magnets modules may be attached to the stator of a permanent magnet machine.

[0051] FIG. 2 shows a partial cross-sectional view of the permanent magnet machine 10 including a plurality of permanent magnet modules 101 attached to the rotor 12. The permanent magnet modules 101 are attached to a side of the rotor 12 which faces the stator 11. Each permanent magnet module 101 comprises a permanent magnet 200 and a baseplate 301. According to other embodiment of the present invention (not shown), each permanent magnet module 101 may comprise more than one permanent magnet 200 and more than one baseplate 301. Each of the permanent magnets 200 is attached to a rotor body 130 of the rotor 12 by means of the respective base plate 301. Each base plate 301 of each permanent magnet module 101 is connected to a respective recess 131 provided in the rotor body 130. Each permanent magnets module 101 comprises a respective cover for covering the permanent magnet 200, as detailed in the following.

[0052] FIG. 3 shows a cover 601 for covering the permanent magnet 200. The cover 601 includes a top side 602 and two lateral sides 603, 604. The magnetic permeability of the top side 602 is higher than the magnetic permeability of the lateral sides 603, 604. The lateral sides 603, 604 are respectively attached to a first and a second edge 604, 605 of the top side 602. The first and the second edge 604, 605 may have any shape or form, including round and squared. The lateral sides 603, 604 are angled with respect to the top side 602 according to an angle α, comprised between 45 degrees and 135 degrees. The top side 602 includes at least a first stainless-steel phase and the two lateral sides 603, 604 include at least a second stainless-steel phase, which may be different from the first stainless-steel phase.

[0053] The first stainless-steel may be a magnetic stainless-steel phase, for example ferrite or martensite. The second stainless-steel phase may be a non-magnetic stainless-steel phase, for example a austenite.

[0054] The first and the second stainless-steel phases may be both non-magnetic phases. In such embodiments the top side 602 is thinner than the lateral sides 603, 604.

[0055] The first and the second stainless-steel phases may be both magnetic phases. In such embodiments the top side 602 is thicker than the lateral sides 603, 604.

[0056] FIG. 4 shows a circumferential sectional view of a permanent magnet module 101 including a permanent magnet 200 and a respective baseplate 301 attached to the permanent magnet 200. The permanent magnet 200 includes a bottom surface 201 facing the baseplate 301. The bottom surface 201 may be attached to the baseplate 301, for example by gluing. The permanent magnet module 101 further includes the cover 601 covering the permanent magnet 200. The baseplate 301 may comprise the first and/or the second stainless-steel phases. The cover 601 may be welded to the baseplate 301. According to other embodiments of the present invention, the cover 601 may be attached to the baseplate 301 by other means. The permanent magnet 200 includes a top surface 202 opposite to the bottom surface 201 and two lateral surface 203, 204 connecting the bottom surface 201 with the top surface 202. The top side 602 of the cover 601 covers the top surface 202. The two lateral sides 603, 604 of the cover 601 respectively cover the two lateral surfaces 203, 204.

[0057] FIGS. 5 and 7 illustrate a first embodiment 1001 of a method for manufacturing the cover 601 and the permanent magnet module 101. The first embodiment of the method comprises a first step 1010 of providing one or more permanent magnets 200, a second step 1020 of manufacturing the cover 601 and a third step 1030 of attaching the cover 601 to the permanent magnet 200.

[0058] The second step 1020 comprises: [0059] a first sub-step 1021 of manufacturing a first sheet 401 comprising the first stainless-steel phases and having two main longitudinal edges 404, 405; [0060] a second sub-step 1022 of manufacturing a second and a third sheet 402, 403 comprising the second stainless-steel phases; [0061] a third sub-step 1023 of attaching the second and the third sheet 402, 403 to the two main longitudinal edges 404, 405, respectively, to obtain an assembly sheet 410. The second and the third sheet 402, 403 may be joined to the two main longitudinal edges 404, 405 by a welding 415. The welding 415 may be performed through a seam-welding process, for example TIG or laser welding; [0062] a fourth sub-step 1024 of cutting at least a semifinished product 420 from the assembly sheet 410, the semifinished product 420 including a portion of the first sheet 401, a portion of the second sheet 402 and a portion of the third sheet 403, [0063] a fifth sub-step 1025 of bending the portion of the second sheet 402 and the portion of the third sheet 403 with respect to the portion of the first sheet 401 for deriving the cover 601 from the semifinished product 420 so that the portion of the first sheet 401 corresponds to the top side 602 and the portions of the second sheet 402 and the third sheet 403 respectively correspond to the lateral sides 603, 604. The bending in performed according to the angle α.

[0064] A further optional step may be performed to add further portions of the cover at the axial ends (parallel to the circumferential section of FIG. 4) of the semifinished product 420. These portions may have, for example, the same composition of the second and third sheets 402, 403 and may be joined to the semi-finished product 420 by the same welding process.

[0065] As a variant of the above describe first embodiment of the method, the first sheet 401, the second sheet 402 and the third sheet 403 may comprise the same stainless-steel phase and may have different thicknesses. The first sheet 401 is thinner than the second and the third sheet 402, 403 if a non-magnetic stainless-steel phase is used. The first sheet 401 is thicker than the second and the third sheet 402, 403 if a magnetic stainless-steel phase is used.

[0066] FIGS. 6 and 8 illustrate a second embodiment 1101 of a method for manufacturing the cover 601 and the permanent magnet module 101. The second embodiment of the method comprises a first step 1110 of providing one or more permanent magnets 200, a second step 1120 of manufacturing the cover 601 and a third step 1130 of attaching the cover 601 to the permanent magnet 200.

[0067] The step of manufacturing the cover 601 comprises: [0068] a first sub-step 1121 of manufacturing a semifinished sheet 450 comprising the second stainless steel, [0069] a second sub-step 1122 of deforming locally the semifinished sheet 450 along a deformation direction Y for transforming the second stainless steel into the first stainless steel to obtain an assembly sheet 410 having a first sheet 401 comprising the first stainless-steel and a second and a third sheet 402, 403 comprising the second stainless-steel, the second and the third sheet 402, 403 being provided along two respective main longitudinal edges 404, 405 of the first sheet 401. Deforming may be performed through an operation of deep rolling or burnishing or hammer peening; [0070] a third sub-step 1123 of cutting at least a semifinished product 420 from the assembly sheet 410, the semifinished product 420 including a portion of the first sheet 401 a portion of the second sheet 402 and a portion of the third sheet 403, [0071] a fourth sub-step 1124 of bending the portion of the second sheet 402 and the portion of the third sheet 403 with respect to the portion of the first sheet 401 for deriving the cover 601 from the semifinished product 420 so that the portion of the first sheet 401 corresponds to the top side 602 and the portions of the second sheet 402 and the third sheet 403 correspond to the lateral sides 603, 604. The bending in performed according to the angle α.

[0072] Alternatively to the above described sequence of sub-steps 1121, 1122, 1123, 1124, deforming locally the cover 601 may be performed after forming the top side 602 and the lateral sides 603, 604 from the semifinished sheet 450, for example through bending.

[0073] As a variant of the above describe second embodiment of the method, deforming locally the semifinished sheet 450 does not transform the second stainless steel, the second stain-less steel being a non-magnetic stainless-steel. The result is semifinished sheet 450 having a first sheet 401 thinner than the second and the third sheet 402, 403.

[0074] According to a third embodiment (not shown) of the invention, the step of manufacturing the cover comprises one or more operations of additive manufacturing. Different powder materials can used to fabricate the top side 602 and the lateral sides 603, 604. The additive manufacturing may be made directly on the magnet 200, so eliminating extra manufacturing steps.

[0075] According to other embodiments (not shown) of the invention, manufacturing the cover may comprise one or more operations of stamping or die press forming.

[0076] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0077] For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.