Patent Description:
An electrical generator, such as an electric generator installed in a wind turbine, typically comprises a rotor which rotates relative to a stator.

The stator normally comprises a frame body longitudinally extending along a longitudinal axis and including a stator yoke and a plurality of teeth protruding according to a radial direction from the stator yoke to respective tooth radial ends. Each tooth extends also longitudinally between a first tooth longitudinal end and a second tooth longitudinal end. In the stator a plurality of slots are also defined, each slot being delimited circumferentially by two adjacent teeth and radially extending between the stator yoke and the respective tooth radial ends. Each slot houses a respective winding and a wedge. The wedges are provided at the tooth radial ends for protecting and keeping in place the respective windings.

End plates are provided at the teeth longitudinal ends for mechanically supporting the stator lamination and in particular the teeth. Such end plates have a typical finger shape for following the shape of the stator teeth.

Main inconveniences of the above described design are:.

The prior art (for example <CIT>) discloses wedges having main wings for respectively abutting against at least a first tooth and a second tooth, i.e. wedges having a T-shape at their longitudinal ends. Such solution may be improved in terms of coupling between the wedges and the teeth.

Therefore, there is still a need to provide an improved design for a stator of an electrical generator, which in particular permits to avoid the use of the finger end plates and at the same time to provide the necessary mechanical support for the teeth of the stator.

This need may be met by the subject matter according to the independent claim.

According to the present invention a wedge for a stator comprises a plurality of teeth and comprises at least a first portion and a second portion transversally protruding from the first portion, the first portion and the second portion being shaped and dimensioned in such a way that, when the wedge is attached to one of the tooth radial ends, the first portion extends longitudinally from one of the first tooth longitudinal end and the second tooth longitudinal end towards the other of the first tooth longitudinal end and the second tooth longitudinal end and the second portion abuts against said one of the first tooth longitudinal end and the second tooth longitudinal end. The first portion is dimensioned in order to circumferentially extend from a first tooth of the plurality of teeth to a second tooth of the plurality of teeth, the first tooth and the second tooth being circumferentially adjacent, and the second portion being dimensioned in order to longitudinally abut against both the first tooth and the second tooth. The second portion comprises two main wings for respectively abutting against the first tooth and the second tooth, the second portion comprising two further wings, respectively attached to each of the main wings, for respectively abutting against the first tooth and the second tooth.

Furthermore, it is provided a stator for an electrical generator comprising:.

The above described electric generator including the stator of the present invention may be advantageously integrated in a wind turbine.

Advantageously, the proposed wedge of the stator, by providing mechanical support to the stator teeth at their radial ends, efficiently avoid the use of any finger end plate. In particular eddy-current losses in the finger plate are removed. A gain of about <NUM>% in the AEP has been estimated. Further, as a result of finger end plates, the stator obtained with present invention is characterized by lower costs and lower weight.

Advantageously, the wedge of the stator according to the present invention are formed in the shape of a "T".

According to a particular embodiment of the invention, the second portion is dimensioned in order to longitudinally abut against the first tooth, second tooth and a further third tooth, the third tooth being circumferentially adjacent to the first tooth or the second tooth. Advantageously, according to such embodiment, the wedge may be dimensioned in order to cover two adjacent slots.

According to further embodiments of the invention, the first portion is dimensioned in order to longitudinally extend from one to the other of the first tooth longitudinal end and the second tooth longitudinal end. Particularly, each wedge comprises at least a third portion transversally protruding from the first portion, the first portion and the third portion respectively abutting against the first tooth longitudinal end and the second tooth longitudinal end when the wedge is attached to one of the tooth radial ends.

With reference to <FIG>, a stator for an electrical generator <NUM> comprises a frame body <NUM> longitudinally extending along a longitudinal axis Y of the stator <NUM>. The terms axial (or longitudinal) radial and circumferential in the following are made with reference to the longitudinal axis Y of the stator <NUM>.

The electrical generator <NUM> further includes a rotor <NUM>, radially external with respect the stator <NUM> and rotatable about the longitudinal axis Y. A permanent magnet <NUM> is attached to the rotor <NUM>, radially interposed between the rotor <NUM> and the stator <NUM>. The rotor <NUM> and the permanent magnet <NUM> are conventional and therefore not described in further detail.

The rotor <NUM> and the permanent magnet <NUM> are also not a specific part of the present invention. The present invention can be therefore adapted to electrical generators with or without permanent magnet or with a radially internal rotor.

The stator <NUM> has a conventional lamination structure including a stator yoke <NUM> and a plurality of teeth <NUM> protruding according to a radial direction orthogonal to the longitudinal axis Y from the stator yoke <NUM>, up to respective tooth radial ends <NUM>.

Each tooth <NUM> is delimited by two respective lateral surfaces <NUM>, radially oriented, and by a respective circumferential surface 38a, at the respective tooth radial end <NUM>, circumferentially connecting the two respective lateral surfaces <NUM>.

Each tooth <NUM> extends longitudinally between a first tooth longitudinal end 21a and a second tooth longitudinal end 21b. With specific reference to <FIG>, the first tooth longitudinal end 21a and/or the second tooth longitudinal end 21b may be aligned along a radial direction with corresponding axial ends of the permanent magnet <NUM> and of the rotor <NUM> or, as shown in <FIG>, the stator <NUM> may include an axial lamination appendix 20a, axially extending with respect to the permanent magnet <NUM> and of the rotor <NUM>.

The plurality of lateral surfaces <NUM> comprises, at respective tooth radial end <NUM>, a plurality notch <NUM> for respectively attaching a plurality of wedges 40a-f of the stator <NUM>, according to the different embodiment of the present invention, as specified in the following.

Optionally, vacuum pressure resin impregnation technique can be implemented to ensure that the wedges 40a-f are held rigidly in place in the respective notches <NUM>.

The stator <NUM> further includes a plurality of slots <NUM>, each slots being circumferential delimited by a pair of circumferentially adjacent teeth <NUM> and radially extending from the stator yoke <NUM> to a respective tooth radial end <NUM> and to at least one respective wedge 40a-f, as detailed in the following. Each slot <NUM> houses a respective winding <NUM>. Each wedge <NUM> protects and keeps in place at least a respective winding <NUM>.

According to other embodiments of the present invention (not shown) the wedges 40a-f are added in every other slot <NUM> or in any other order. According to further embodiments of the present invention (not shown) a combination of the wedges 40a-f of the present invention and of traditional wedges may be used.

According to all the embodiments of the present invention, each wedge 40a-f comprises at least a first portion <NUM> and a second portion 42a-f transversally protruding from the first portion <NUM>. The first portion <NUM> and the second portion 42a-f are shaped and dimensioned in such a way that, when the wedge 40a-f is attached to one of the tooth radial ends <NUM>, in particular at one or more wedge slots <NUM>, the first portion <NUM> extends longitudinally from one of the first tooth longitudinal end 21a and the second tooth longitudinal end 21b towards the other of the first tooth longitudinal end 21a and the second tooth longitudinal end 21b and the second portion 42a-f abuts against said one of the first tooth longitudinal end 21a and the second tooth longitudinal end 21b.

In other words, the first portion <NUM> may extend longitudinally from the first tooth longitudinal end 21a towards the second tooth longitudinal end 21b and in this case the second portion 42a-f abuts against the first tooth longitudinal end 21a. Alternatively, the first portion <NUM> may extend longitudinally from the second tooth longitudinal end 21b towards the first tooth longitudinal end 21a and in this case the second portion 42a-f abuts against the second tooth longitudinal end 21b.

In embodiments where the axial lamination appendix 20a is present, the second portion 42a-f abuts in particular against axial lamination appendix 20a.

In other embodiments (not shown in the attached figures) the second portion 42a-f abuts against said one of the first tooth longitudinal end 21a and the second tooth longitudinal end 21b while one other one of the first tooth longitudinal end 21a and the second tooth longitudinal end 21b the stator <NUM> comprises a finger end plate.

With specific reference to <FIG>, the first portion <NUM> of the wedge 40a is dimensioned in order to circumferentially extend from a first tooth 33a of the plurality of teeth <NUM> to a second tooth 33b, circumferentially adjacent to the first tooth 33a. When coupled to the frame body <NUM>, the first portion <NUM> is attached to two notches <NUM> of two respective lateral surfaces <NUM>, respectively belonging to the first tooth 33a and the second tooth 33b.

The second portion 42a of the wedge 40a comprises two lateral wings <NUM>, orthogonally protruding from the first portion <NUM> of the wedge 40a. When the wedge 40a is coupled to the frame body <NUM>, the second portion 42a and the wings <NUM> are circumferentially oriented, in order that the wings <NUM> longitudinally abut against the first tooth longitudinal end 21a of the first tooth 33a and of the second tooth 33b, respectively.

With specific reference to <FIG>, the wedge 40b comprises two parallel first portions <NUM>, respectively dimensioned in order to circumferentially extend from a first tooth 33a to a second tooth 33b, circumferentially adjacent to the first tooth 33a, and from the second tooth 33b to a third tooth 33c, circumferentially adjacent to the second tooth 33b. The second portion 42b is dimensioned in order to transversally connect the two parallel first portions <NUM> and to longitudinally abut against the first tooth longitudinal end 21a of the first tooth 33a, of the second tooth 33b and of a further third tooth 33c. The wedge 40b of the present second embodiment is equivalent to two wedges 40a of the <FIG>. According to other embodiments of the present invention (not shown) the second portion 42b is dimensioned in order to transversally connect the two parallel first portions <NUM> and to longitudinally abut against more than three teeth <NUM>, for example four teeth <NUM> or five teeth <NUM> or more.

With specific reference to the three further embodiments of <FIG>, in a respective embodiment the wedge 40c, 40d, 40e (at the left side, at the center and at the right side of <FIG>) has an analogous structure of the wedges 40a of the first embodiment, where the respective second portion 42c, 42d, 42e further includes two further wings <NUM>, respectively attached to each of the main wings <NUM>, also abutting against the first tooth longitudinal end 21a of the first tooth 33a and of the second tooth 33b. The presence of the two further wings <NUM> increases the surface of contact between the respective second portion 42c, 42d, 42e and the coupling between the first tooth longitudinal end 21a of the first tooth 33a and of the second tooth 33b. In an embodiment, the wedge 40c includes two further wings <NUM>, which are coplanar and inclined with respect to the main wings <NUM> of the respective second portion 42c. In a further embodiment, the wedge 40d includes two further wings <NUM>, which are coplanar and orthogonally inclined with respect to the main wings <NUM> of the respective second portion 42d. In the further the embodiment the two further wings <NUM> are therefore radially oriented. In a further embodiment, the wedge 40e includes two further wings <NUM>, which in the axial view of <FIG> have a circular profile.

Claim 1:
Wedge (40a-f) for a stator (<NUM>) comprising a plurality of teeth (<NUM>) of an electrical generator comprising at least a first portion (<NUM>) and a second portion (42a-f) transversally protruding from the first portion (<NUM>), the first portion (<NUM>) and the second portion (42a-f) being shaped and dimensioned in such a way that, when the wedge (40a-f) is attached to a tooth radial end (<NUM>) of the stator (<NUM>), the first portion (<NUM>) extends longitudinally from one of a first tooth longitudinal end (21a) and a second tooth longitudinal end (21b) towards the other of the first tooth longitudinal end (21a) and the second tooth longitudinal end (21b) and the second portion (42a-f) abuts against said one of a first tooth longitudinal end (21a) and a second tooth longitudinal end (21b), the first portion (<NUM>) being dimensioned in order to circumferentially extend from a first tooth (33a) of the plurality of teeth (<NUM>) to a second tooth (33b) of the plurality of teeth (<NUM>), the first tooth (33a) and the second tooth (33b) being circumferentially adjacent, and the second portion (42a) being dimensioned in order to longitudinally abut against both the first tooth (33a) and the second tooth (33b),
characterized in that the second portion (42a-e) comprises two main wings (<NUM>) for respectively abutting against the first tooth (33a) and the second tooth (33b), and the second portion (42a-e) comprises two further wings (<NUM>), respectively attached to each of the main wings (<NUM>), for respectively abutting against the first tooth (33a) and the second tooth (33b).