DK201970741A1

DK201970741A1 - A magnet pole for an electric generator

Info

Publication number: DK201970741A1
Application number: DKPA201970741A
Authority: DK
Inventors: Xiangrong Guo; Jia Liu; Deng Heng; Semmer Silvio
Original assignee: Envision Energy (Jiangsu) Co. Ltd
Priority date: 2017-06-15
Filing date: 2019-12-02
Publication date: 2019-12-09
Also published as: CN110870167A; WO2018227479A1; DK180675B1; DK201970741A8

Abstract

A generator (2) comprises at least one stator (4) and at least one rotor (6). The generator (2) comprises a plurality of permanent magnetic poles (8). The rotor (6) rotates relative to the stator (4).The stator (4) or the rotor (6) comprises magnetic coils (12). The rotation of the rotor (6) generates electric current in the magnetic coils (12). The permanent magnetic poles (8) are fastened to the back iron of the rotor (6) or the stator (4). The permanent magnetic poles (8) are held in place at the back iron by a nonmagnetic cover (14), which is fastened to the back iron by press bars (16), which are fixed to the back iron by fastening means (18). Hereby, a highly effective fastening of the permanent magnetic poles (8) towards the back iron can be achieved. The generator (2) has a perfect operation for a long period of time which is necessary if the generator (2) is to be used in a wind turbine.

Description

A magnet pole for an electric generator

Field of the Invention

The present invention relates to generators comprising at least one stator and at least one rotor, which generator comprises a plurality of permanent magnetic poles placed at the rotor or stator, which permanent magnetic poles are fixed to a rotor or stator back iron, which rotor is rotated in relation to a stator, which stator or rotor comprises magnetic coils, in which magnetic coils the permanent magnetic poles by rotation of the rotor generate electric current in the coils.

Object of the Invention

It is the object of the present patent application to fasten the permanent magnets to the back iron of a rotor or a stator of a generator.

Description of the Invention

The object can be fulfilled with a generator as disclosed in the preamble of claim 1 and modified so that the magnetic poles are held in place at the back iron by a nonmagnetic cover, which cover is fastened to the back iron by press bars, which press bars are fixed to the back iron by fastening means.

Hereby, a highly effective fastening of the permanent magnetic poles can be achieved towards the back iron in generators. Depending on the type of generator, the permanent magnets can be placed at an outer rotor where these magnets are cooperating with a stator that comprises windings, with which windings and rotation of the magnets the magnetic field through the coils will change in size and direction and hereby generate electric current in the coils. In order to have a perfect operating generator for a very long period of time which is necessary if the generator is to be used in a wind turbine, it is very important that the permanent magnets are fixed in a highly effective manner towards the back iron. This can be achieved if the permanent magnets are held in place by a cover formed of a nonmagnetic material such as stainless steel. Other materials which have nonmagnetic properties can be used instead of stainless steel, but

DK 2019 70741 A1 stainless steel is sufficient strong as material and it performs a nearly perfect fixation of a magnet. The cover has, of course, to be fixed towards the back iron and, here, press bars are used, which cover can be fixed towards the back iron with fastening means such as traditional bolts for screwing. Other fastening methods could also be used such as rivets.

In a preferred embodiment of the present patent application, the magnetic poles can be glued towards the back iron. Hereby, it can be achieved that by especially a rotor which also during the production has to be rotated, each of the magnets can be fixed to the back iron with a gluing process before shield and press bars are to be mounted. Without gluing it will be a bit difficult to handle the magnets during the process of mounting the cover and the press bars. Therefore, the gluing is only meant for a temporary mounting of the magnets which has only limited effect when the rotor is mounted with cover and press bars.

In a further preferred embodiment of the present patent application, the grooves of the press bars can fasten the hook shaped form of the cover to the back iron. Hereby, it can be achieved that there is a highly effective fastening and fixation of the magnets simply because there is performed a mechanical fastening of the cover towards the press bars. Each of the covers is designed with the hook shaped form and, thereby, performing an edge which is passing into the grooves of the press bars. Hereby, it is achieved that fastening is not only performed by the cover pressed towards the magnets, but there is a fixation until the cover is directing mechanical forces by the press bars.

In a further preferred embodiment of the present patent application, the press bars can be double sided for fastening a first and a second cover. Hereby, it can be achieved that each press bar has double grooves placed at both sides of the bolts for fastening. In that way, each press bar can perform a fastening of two different covers, and hereby it can be achieved that forces acting under press bars from one of the covers probably will act in the opposite direction from the second cover. Hereby, the forces that are to be sent through the bolts from the press bar to the back iron will be partly reduced.

DK 2019 70741 A1

In a further preferred embodiment of the present patent application, the press bars can have an outer form that follows the cover, which cover has a form that follows the surface of the permanent magnetic pole. By having the same surface form as the surface of the magnets, it is possible that the cover is acting as a shield with direct contact to the surface of the magnet. In that way, a highly effective protection of the magnet is achieved. In normal operation, protection should not be necessary, but with a fast rotating outer rotor which is rotating with a very small air gap towards a stator, which is carrying magnets, there is a risk that dirt particles or liquid particles could hit the magnet. By placing the magnet below the cover, the magnet is protected.

In a further preferred embodiment of the present patent application, both edges of the cover can be pinched to a hook shaped form. Hereby, it can be achieved that the fastening of the covers can be highly effective in that both edges are pinched to the hook form so they pass into the grooves in the press bars.

In a further preferred embodiment of the present patent application, the edges of the cover can be pinched to a hook shaped form where part of the hook shaped edges is removed for forming one or more openings in the hook shaped form of the edges of the cover. Hereby, a much higher degree of fastening can be achieved in that the press bar has at least one section without any groove and where no edge of the cover is placed in the groove. In that way, the cover is fastened so that any sliding in the parallel direction to the surface of the cover and parallel to the press bar is more or less impossible. A partly fixation of the hook shaped edge from the cover is sufficient because the cover is probably made of stainless steel and, therefore, it is a very strong material.

In a further preferred embodiment of the present patent application, the press bars can comprise grooves, which grooves cooperate with the hook shaped edges of the cover. Hereby, it is achieved that the grooves of the press bar and the edge cooperate in a way where an assembly of press bar and cover will be perfect because otherwise assembling is not possible. Furthermore, it is achieved that any sliding in any direction of the cover is impossible.

DK 2019 70741 A1

In a further preferred embodiment of the present patent application, the press bars can be formed of one or more sections, which sections are formed in at least a first and a second section, where the first section comprises grooves and the second section is formed without grooves. By forming the press bars in different sections which is maybe mechanical and combined by mechanical connections, it should be possible to form one section with grooves and another section without grooves.

In a further preferred embodiment of the present patent application, the rotor can be placed outside the stator. By operating with an outside rotor and a stator placed inside the rotor, it is possible to let the permanent magnets generate current in still standing coils and where power can be transmitted from the coils in a highly effective manner, simply because of the fact that the power does not have to be sent to any rotating transmission systems.

In a further preferred embodiment of the present patent application, the rotor can be placed inside the stator. Hereby, it can be achieved that the inner rotor comprises the magnets and the coils are placed outside in the stator. Hereby, it is again achieved that the magnets are the rotating component and the coils are fixed so that changes in the magnetic field through the coils are generating electric power, which power can be sent further through a wiring or cable system towards maybe a converter. In the converter, there is probably performed a change in the frequency from the generated power of a generator into a grid frequency and maybe afterwards that a transformation to the correct grid voltage.

The magnet is fastened to the rotor of the generator by the press bar and bolts. The magnet is part of a pole of the generator, especially for the direct drive generator. The magnet pole has one stainless steel cover, at least one magnet piece, one press bar, and several bolts. The magnet piece bottom surface could be glued to the rotor house, and the cover is fastened to the rotor house by press bar. The cover is a magnetic nonconducting material, such as stainless steel. The cover has been pinched to a hook shape so that it can be fastened by a press bar groove.

Description of the Drawing

Fig. 1 shows a wind turbine.

DK 2019 70741 A1

Fig. 2 shows a section of a generator.

Fig. 3 shows a last a sectional view of a section of a generator.

Fig. 4 shows an assembling of a magnetic pole.

Fig. 5 shows an assembled magnetic pole.

Fig. 6 shows an alternative embodiment for a pole for a rotor of a generator.

Detailed Description of the Invention

Fig. 1 shows a wind turbine 100 with a nacelle 102 and with three blades 104 connected to a hub 105. The nacelle 102 is carried on a tower 106. The hub 105 is mechanically connected to a generator in order to let the rotor of the generator rotate in relation to a stator and in that way generate electric power.

Fig. 2 shows a sectional view of a generator 2, which generator 2 comprises a stator 4 and a rotor 6. The stator 4 comprises magnetic poles 8 formed of permanent magnets. The stator 4 comprises magnetic coils 12. At the stator 4 there is an indicated press bar 16 for fixation of the magnetic poles at the back iron, which is not shown at this figure.

Fig. 3 shows a sectional view of a generator 2, which generator 2 comprises a stator 4 and a rotor 6. Furthermore, magnetic poles 8 formed of permanent magnets are shown, the stator 4 comprises a plurality of coils 12 and, at the stator 4, press bars 16 are indicated which are used for fixing the permanent magnets at a not shown back iron.

If the rotor 6 comprises permanent magnetic poles 8 which are magnetised in the opposite direction, then rotation of the stator will generate a changing magnetic field in the coils 12. Change of the magnetic field will generate a current in the coils, which current from these coils can be sent to a converter, which can make a frequency and voltage conversion.

At fig. 4, a permanent magnetic pole 8 is indicated, which permanent magnetic pole 8 is to be fastened at the back iron of a rotor. Above, the permanent magnetic pole 8 is indicated as a nonmagnetic cover 14. This nonmagnetic cover 14 comprises an edge 15, which edge 15 is part of a hook shaped form 20. A press bar 16 is indicated, which

DK 2019 70741 A1 has to be fastened with bolts 18 towards the not indicated back iron. The press bars 16 comprise grooves 22 which are supposed to accommodate the edge of the cover 15.

At fig. 5, same components are indicated as in fig. 4. The difference is that the nonmagnetic cover 14 is now pressed against the permanent magnetic poles 8 by the nonmagnetic cover 14 and with the press bars 16, which are now screwed towards the not indicated back iron by bolts 18.

Fig. 6 shows an alternative embodiment, which indicates same components as in figs. 4 and 5. The only difference is that one of the press bars is divided into two sections; a first section 24 and a second section 26. Furthermore, it can be seen that the edge of the nonmagnetic cover 14 is divided into two sections where there is no edge in the middle. In that way, there will be a further fixation of the nonmagnetic cover since the grooves 22 are following the edge 15 so that there is a middle section of the press bars where the groove 22 does not exist. In that way, it is achieved that fixation of the nonmagnetic cover 14, also in the perpendicular direction to the radial direction of the rotor, is prevented, simply because there is an extra fixation against any sliding movement of the nonmagnetic cover 14.

The magnet is fastened to the rotor of the generator by the press bar and bolts.

The magnet is part of a pole of the generator, especially for the direct drive generator. The magnet pole has one stainless steel cover, at least one magnet piece, one press bar and several bolts. The magnet piece bottom surface could be glued to the rotor house, and the cover is fastened to the rotor house by the press bar. The cover is a magnetic non-conducting material, such as stainless steel. The cover has been pinched to a hook shape so that it is fastened by a groove in the press bar.

1. The magnet pole includes magnets, magnetic flux non-conducting stainless steel cover, press bar, and bolts.

2. The cover is fastened to the rotor house by the press bar.

3. The press bar is fastened by bolts.

DK 2019 70741 A1

4. The cover has a punched hook shaped edge, the press bar has a groove to match the hook.

Usually, there exist two methods to mount the magnet. One typical method is like the one used by Siemens. Here, they use an integrated module to seal the magnet, machining grooves in the rotor house, and then mount the module into the grooves. Another typical method is like the one used by Goldwind. Here, they fix magnets by press bar and glass fiber, and they use a lot of epoxy to protect magnets against anti-corrosion.

Details:

Our innovative points:

1. The method is cheaper than the method used by Siemens module.

2. The assembly is easier than Goldwind fiber glass method.

3. The stainless cover is more stable and provides reliable protection of the magnets against outer impact.

4. The cover has hoops and the press bar has grooves; this can easily be fulfilled and has more reliable fixture strength.

List of reference numbers generator (2) stator (4) rotor (6) permanent magnetic poles (8) magnetic coils (12) nonmagnetic cover (14) edge of cover(15) press bars (16) fastening means (18) hook shaped form (20) grooves (22)

DK 2019 70741 A1 press bar first section (24) press bar second section (26)

Claims

1. Generator (2) comprising at least one stator (4) and at least one rotor (6), which generator (2) comprises a plurality of permanent magnetic poles (8) placed at the rotor (6) or stator (4), which permanent magnetic poles (8) are fixed to a rotor or stator back iron, which rotor (6) is rotated in relation to a stator (4), which stator or rotor (4) comprises magnetic coils (12), in which magnetic coils (12) the permanent magnetic poles (8) by rotation of the rotor (6) generate electric current in the coils (12), characterised in that the magnetic poles (8) are held in place at the back iron by a nonmagnetic cover (14), which cover (14) is fastened to the back iron by press bars (16), which press bars (16) are fixed to the back iron by fastening means (18).

2. Generator (2) according to claim 1, characterised in that the magnetic poles (8) are glued towards the back iron.

3. Generator (2) according to claim 2, characterised in that the press bar grooves (22) are fastening the hook shaped form (20) of the cover (14) to the back iron.

4. Generator (2) according to claim 3, characterised in that the press bars (16) are double sided for fastening a first and a second cover (14).

5. Generator (2) according to claim 4, characterised in that the press bars (16) have an outer form that follows the cover (14), which cover (14) has a form that follows the surface of the permanent magnetic pole (8).

6. Generator (2) according to claim 5, characterised in that both edges (15) of the cover (14) are pinched to a hook shaped form (20).

7. Generator according to claim 6, characterised in that the edges of the cover (14) are pinched to a hook shaped form where part of the hook shaped edges (15) is removed for forming one or more openings in the hook shaped form of the edges of the cover (14).

DK 2019 70741 A1

8. Generator (2) according to claim 7, characterised in that the press bars (16) comprise grooves (22) which grooves (22) cooperate with the hook shaped edges (15) of the cover (14).

5

9. Generator according to claim 8, characterised in that the press bars (16) are formed of one or more sections (24,26), which sections (24,26) are formed in at least a first (24) and a second section (26) where the first section (24) comprises grooves (14) and the second section (26) is formed without grooves.

10 10. Generator (2) according to claim 9, characterised in that the rotor (6) is placed outside the stator (4).

11. Generator according to claim 9, characterised in that the rotor (6) is placed inside the stator (4).