(51) Int Cl.: H02K 1/27 ( ) H02K 1/32 ( ) H02K 1/20 ( ) H02K 7/18 ( )

Transcription

1 (19) TEPZZ 4ZZ6 4B_T (11) EP B1 (12) EUROPEAN PATENT SPECIFICATION (4) Date of publication and mention of the grant of the patent: Bulletin 2013/40 (1) Int Cl.: H02K 1/27 ( ) H02K 1/32 ( ) H02K 1/20 ( ) H02K 7/18 ( ) (21) Application number: (22) Date of filing: (4) Generator, in particular for a wind turbine Generator, insbesondere für eine Windturbine Générateur, en particulier pour éolienne (84) Designated Contracting States: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK SM TR (43) Date of publication of application: Bulletin 2011/2 (73) Proprietor: Siemens Aktiengesellschaft München (DE) (72) Inventor: Kimiabeigi, Mohammad 7330, Brande (DK) (6) References cited: DE-A EP B1 Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). Printed by Jouve, 7001 PARIS (FR)

2 1 EP B1 2 Description [0001] The present invention relates to a generator, in particular for a wind turbine, comprising a stator comprising stator lamination packs; a rotor, rotatable around the stator, with at least one permanent magnet or a plurality of permanent magnets arranged in the circumferential direction, each one of said magnets consisting in the axial direction either of one single magnet or of a plurality of magnets; at least one airduct, for guiding an air flow to the stator, comprising radial portions positioned between said stator lamination packs; whereby the at least one permanent magnet is or the plurality of permanent magnets are provided with recesses positioned opposite a radial portion of the airduct. [0002] Such a generator of a wind turbine is known from DE A1. [0003] Wind turbines are provided with a rotor shaft which is part of an electrical generator producing electricity during movement of the rotor relative to a stator of the generator. The stator comprises a number of coils, the rotor comprises a number of permanent magnets so that an electric voltage is induced when the rotor is turned. [0004] In recent years a trend towards wind turbines with increased power can be observed which requires an efficient cooling system for the generator. In conventional wind turbines airducts are used which are connected to the cooling source in order to supply an air flow to the stator, windings of the stator and the magnets of the rotor. Due to the increasing size of the wind turbines the number and size of the permanent magnets is raising as well, which leads to higher costs for the generator. [000] It is therefore an object of the present invention to provide a generator with reduced manufacturing costs. [0006] According to the present invention this object is achieved in the above defined generator in that said recesses are shaped such that the magnet length at the side facing the stator is smaller than the magnet length at the side facing the rotor. [0007] The present invention is based on the idea that a portion of the permanent magnet is electromagnetically poorly used or even unused so that these portions can be taken away. In this way less magnet material is necessary so that a lower weight of the generator and lower manufacturing costs are achieved. Further the invention leads to lower material costs. It has been found out that those portions of the permanent magnets which are placed in front of the stator airducts do not efficiently contribute to the generation of torque due to the relatively high saturation of the stator laminations near the airduct. According to the invention the permanent magnets are provided with recesses so that these unused parts of the magnet are reduced or even eliminated. [0008] According to the invention the inventive generator is provided with recesses which are shaped such that the magnet length at the side facing the stator is smaller than the magnet length at the side facing the rotor. This means that the magnets radial thickness in those regions that face radial airducts is smaller than the magnets radial thickness in those regions that face the stator lamination pack. Basically the at least one permanent magnet or the plurality of permanent magnets is shaped in the axial direction so that the magnet is provided with a non-uniform shape. [0009] According to a first embodiment of the inventive generator the recesses can have a trapezoidal shape, whereby the longer edge of the parallel edges faces the stator. It is possible to use a plurality of permanent magnets which have a shape of a trapezoid, alternatively one permanent magnet block can be used which is provided with a plurality of trapezoidal recesses. [0010] According to another embodiment of the inventive generator the recesses may have a substantially triangular shape. Similar to the previous embodiment the generator may comprise a number of separate permanent magnets which have a triangular shape, as an alternative one magnet block can be used with a plurality of triangular recesses. [0011] Preferably the edges of the recesses which are of a substantially triangular shape can be formed convex or concave. [0012] In general the recesses simply may be formed concave which means that a permanent magnet block has concave recesses opposite to the stator. [0013] According to a further development of the invention the at least one permanent magnet or the plurality of permanent magnets is or are arranged on a base plate of the rotor or on a rotor yoke. [0014] According to a preferred embodiment of the invention the number of the permanent magnets in the axial direction and the number of stator lamination packs is the same. [001] However, according to a further development of the invention the number of permanent magnets in the axial direction is lower than the number of stator lamination packs. [0016] The invention and its underlaying principle will be better understood when consideration is given to the following detailed description of preferred embodiments. [0017] In the accompanying drawings: Fig. 1 Fig. 2 Fig. 3 Fig. 4 is a sectional view of a first embodiment of an inventive generator; is a sectional view of a second embodiment of an inventive generator; is a sectional view of a third embodiment of an inventive generator; and is a sectional view of a fourth embodiment of an inventive generator. [0018] Fig. 1 shows a portion of a generator 1 for a wind turbine in a radial sectional view. The generator 1 2

3 3 EP B1 4 comprises a stator 2 with a plurality of stator lamination packs 3 in which induction coils are mounted. A rotor 4 is rotatable around the stator 2, the rotor 4 comprises a rotor yoke with a base plate 6 and a number of permanent magnets 7, which are disposed on the base plate 6. [0019] The rotor 4 is connected to a hub, which is not shown in fig. 1, to which rotor blades are connected to. The stator 2 is disposed within a nacelle, which is mounted on top of a tower of the wind turbine. When the rotor 4 is rotated an electric current is induced in the induction coils of the stator 2. [0020] Between stator 2 and rotor 4 an axial gap 8 is disposed which is used as an airduct 9. An air flow is generated by a fan (not shown) and through the airduct 9 the air flow reaches the permanent magnets 7 and the stator lamination packs 3. Basically the airduct 9 comprises an axial portion which is defined by the permanent magnets 7 and the outer edge 10 of the stator lamination packs 3. Further the airduct 9 comprises radial portions 11 between neighboring stator lamination packs 3. The arrows in fig. 1 show the air flow through the airduct 9. The air flow is supplied such that endwindings 12, which are laterally protruding from the stator lamination packs 3, are cooled as well. The fan which supplies the air flow to the airduct 9 is connected to a cooling source 13. [0021] The permanent magnets 7 are provided with recesses 14 having a triangular shape which are disposed opposite to the stator 2. In the embodiment of fig. 1 a plurality of permanent magnets 7 is used which are disposed next to each other in the axial direction. In the sectional view of fig. 1 each permanent magnet 7 has a trapezoidal shape whereby the longer edge of the parallel edges faces the rotor 4. The recesses 14 are positioned opposite of the airducts 9 in the stator 2, in particular each of the recesses 14 is placed in front of a radial portion 11 of the airduct 9. In this area a permanent magnet cannot contribute to the generation of torque due to the high saturation of stator laminations. Therefore magnetic material is omitted which leads to the trapezoidal shape of the permanent magnets 7 as is depicted in fig. 1. The amount of the magnet material and the weight of the generator is lower compared to a conventional generator where permanent magnets with a uniform shape in axial direction are used. [0022] Another advantage is that due to the recesses 14 turbulences in the airflow are generated which lead to a better cooling of generator 1. [0023] Fig. 2 shows a second embodiment of a generator, where the same reference signs have been used for the same components. In general the generator of fig. 2 has the same structure as the generator 1 of fig. 1. In contrast to the first embodiment the permanent magnets 1 are provided with recesses with an arc-like or convex shape. The amount of the magnetic material of the generator as shown in fig. 2 is slightly higher compared to the amount of magnetic material of the embodiment of fig. 1. Consistently with the first embodiment the recesses 14 are provided opposite to the radial portions 11 of the airduct 9. [0024] Fig. 3 shows a third embodiment of a generator where the rotor 4 comprises one permanent magnet 16 in the form of a magnetic block which is provided with a plurality of recesses 17. The recesses 17 have a trapezoidal shape and the magnetic material is omitted opposite to radial portions 11 of the airduct 9. The recesses 17 are positioned opposite to radial portions 11 of the airduct 9. Due to the enlarged surface of the magnetic block a more efficient cooling of the magnetic block through the airflow is obtained. [002] Fig. 4 shows a fourth embodiment of a generator where the rotor 4 comprises a permanent magnet 18 with a plurality of recesses 19, which are arranged with a certain distance from each other. The recesses 19 are formed arc-like so that the permanent magnet 18 is smaller near the radial portion 11 of the airduct 9 and larger in between, opposite to the stator 3 of the stator 2. The recesses 19 are postioned opposite of radial portions 11 of the airducts 9. [0026] In the embodiments of fig. 1 to fig. 4 the number of the magnets 7, 1 or the number of the sections of the magnets 16, 18 in the axial direction and the number of stator lamination packs 3 is the same. Claims 1. Generator (1), in particular for a wind turbine, comprising: - a stator (2) comprising stator lamination packs (3); - a rotor (4), rotatable around the stator (2), with at least one permanent magnet or a plurality of permanent magnets (7, 1, 16, 18)) arranged in the circumferential direction, each one of said magnets (7, 1, 16, 18) consisting in the axial direction either of one single magnet (16, 18) or of a plurality of magnets (7, 1); - at least one airduct (9), for guiding an air flow to the stator (2), comprising radial portions (11) positioned between said stator lamination packs (3); whereby the at least one permanent magnet (16, 18) is or the plurality of permanent magnets (7, 1) are provided with recesses (14, 17, 19) positioned opposite a radial portion (11) of the airduct (9), characterised in that said recesses (14, 17, 19) are shaped such that the magnet length at the side facing the stator (2) is smaller than the magnet length at the side facing the rotor (4). 2. Generator according to claim 1, characterised in that the recesses (17) have a trapezoidal shape, whereby the longer edge of the parallel edges faces the stator (2). 3

4 EP B Generator according to claim 1, characterised in that the recesses (14) have a substantially triangular shape. 4. Generator according to claim 3, characterised in that the recesses (14) have a convex shape or a concave shape.. Generator according to claim 1, characterised in that the recesses (19) are formed concave. 6. Generator according to any of the preceding claims, characterised in that the at least one permanent magnet (16) is or the plurality of permanent magnets (7, 1) are arranged on a base plate (6) of the rotor (4). 7. Generator according to any of the preceding claims, characterised in that the number of the permanent magnets (7, 1) in the axial direction and the number of stator lamination packs (3) is the same. 8. Generator according to any of the preceding claims, characterised in that the number of permanent magnets (7, 1) in the axial direction is lower than the number of stator lamination packs (3). Patentansprüche 1. Generator (1), insbesondere für eine Windenergieanlage, welcher umfasst: - einen Stator (2), der Statorblechpakete (3) umfasst; - einen Rotor (4), der um den Stator (2) drehbar ist, mit mindestens einem Permanentmagneten oder einer Vielzahl von Permanentmagneten (7, 1, 16, 18), die in der Umfangsrichtung angeordnet sind, wobei jeder dieser Magnete (7, 1, 16, 18) in der axialen Richtung entweder aus einem einzigen Magneten (16, 18) oder aus einer Vielzahl von Magneten (7, 1) besteht; - mindestens einen Luftkanal (9) zum Leiten eines Luftstroms zu dem Stator (2), welcher radiale Abschnitte (11) umfasst, die zwischen den Statorblechpaketen (3) positioniert sind; wobei der mindestens eine Permanentmagnet (16, 18) oder die Vielzahl von Permanentmagneten (7, 1) mit Aussparungen (14, 17, 19) versehen ist/ sind, der/die gegenüber einem radialen Abschnitt (11) des Luftkanals (9) positioniert ist/ sind, dadurch gekennzeichnet, dass die Aussparungen (14, 17, 19) derart geformt sind, dass die Magnetlänge auf der dem Stator (2) zugewandten Seite kleiner als die Magnetlänge auf der dem Rotor (4) zugewandten Seite ist Generator nach Anspruch 1, dadurch gekennzeichnet, dass die Aussparungen (17) eine trapezförmige Gestalt aufweisen, wobei der längere Rand von den parallelen Rändern dem Stator (2) zugewandt ist. 3. Generator nach Anspruch 1, dadurch gekennzeichnet, dass die Aussparungen (14) eine im Wesentlichen dreieckige Form aufweisen. 4. Generator nach Anspruch 3, dadurch gekennzeichnet, dass die Aussparungen (14) eine konvexe Form oder eine konkave Form aufweisen.. Generator nach Anspruch 1, dadurch gekennzeichnet, dass die Aussparungen (19) konkav geformt sind. 6. Generator nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass der mindestens eine Permanentmagnet (16) oder die Vielzahl von Permanentmagneten (7, 1) auf einer Grundplatte (6) des Rotors (4) angeordnet ist/sind. 7. Generator nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die Anzahl der Permanentmagnete (7, 1) in der axialen Richtung und die Anzahl der Statorblechpakete (3) gleich sind. 8. Generator nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die Anzahl der Permanentmagnete (7, 1) in der axialen Richtung kleiner als die Anzahl der Statorblechpakete (3) ist. Revendications 1. Générateur (1), en particulier pour une éolienne, comprenant : - un stator (2) comprenant des groupes de stratification (3) de stator ; - un rotor (4), rotatif autour du stator (2), avec au moins un aimant permanent ou une pluralité d aimants permanents (7, 1, 16, 18) agencé(s) dans le sens circonférentiel, chacun desdits aimants (7, 1, 16, 18) consistant en, dans le sens axial, l un ou l autre parmi un aimant (16, 18) unique, ou une pluralité d aimants (7, 1) ; - au moins une conduite d air (9), pour guider un flux d air jusqu au stator (2), comprenant des parties radiales (11) positionnées entre lesdits groupes de stratification (3) de stator ; dans lequel l au moins un aimant permanent (16, 18) est, ou la pluralité d aimants permanents (7, 1) sont, prévu(s) avec des évidements (14, 17, 19) 4

5 7 EP B1 8 positionnés à l opposé d une partie radiale (11) de la conduite d air (9), caractérisé en ce que lesdits évidements (14, 17, 19) sont formés de telle manière que la longueur d aimant au niveau du côté faisant face au stator (2) est plus petite que la longueur d aimant au niveau du côté faisant face au rotor (4). 2. Générateur selon la revendication 1, caractérisé en ce que les évidements (17) ont une forme trapézoïdale, dans lequel le bord le plus long parmi les bords parallèles fait face au stator (2) Générateur selon la revendication 1, caractérisé en ce que les évidements (14) ont une forme sensiblement triangulaire Générateur selon la revendication 3, caractérisé en ce que les évidements (14) ont une forme convexe ou une forme concave. 20. Générateur selon la revendication 1, caractérisé en ce que les évidements (19) sont formés concaves. 6. Générateur selon l une quelconque des revendications précédentes, caractérisé en ce que l au moins un aimant permanent (16) est, ou la pluralité d aimants permanents (7, 1) sont, agencé(s) sur une plaque de base (6) du rotor (4). 7. Générateur selon l une quelconque des revendications précédentes, caractérisé en ce que le nombre des aimants permanents (7, 1) dans le sens axial et le nombre de groupes de stratification (3) de stator est le même Générateur selon l une quelconque des revendications précédentes, caractérisé en ce que le nombre des aimants permanents (7, 1) dans le sens axial est inférieur au nombre de groupes de stratification (3) de stator

6 EP B1 6

7 EP B1 7

8 EP B1 REFERENCES CITED IN THE DESCRIPTION This list of references cited by the applicant is for the reader s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard. Patent documents cited in the description DE A1 [0002] 8