STATOR RING, GENERATOR AND WIND TURBINE EQUIPPED THEREWITH

A stator ring for an electric generator having a plurality of grooves for receiving the stator winding, and a magnetic yoke. A stator ring which has a plurality of cooling recesses through which cooling air can flow in the region of the magnetic yoke, wherein the stator ring has a plurality of stator plates which are stacked in succession in the axial direction of the stator ring, wherein the cooling recesses extend through all stator plates.

BACKGROUND

Technical Field

The present invention concerns a stator ring for an electric generator, in particular a synchronous generator or a ring generator of a wind turbine. The invention further concerns such a synchronous generator or ring generator. In addition the invention concerns a wind turbine having such a generator.

Description of the Related Art

Stator rings of the above-indicated kind are basically known. They usually have a large number of grooves for receiving the stator winding, in which electric power is induced by the rotor moving along the winding. The stator rings are typically of such a structure that they have a magnetic yoke adjacent to the portion which carries the grooves. In the case of stator rings for internal rotors the magnetic yoke is disposed radially outside the region in which the grooves are provided. In the case of stator rings for external rotors the situation is correspondingly reversed. Here the grooves are radially outside the magnetic yoke.

As a consequence of the induction of electrical power heat is generated in an electric generator of the above-indicated kind, in particular in the stator ring. In order to keep the power losses caused thereby as low as possible efficient heat dissipation is desirable.

Various approaches for also directly dissipating heat from the stator ring are known from the state of the art. For example citation EP 2 419 991 B1 discloses the use of tubes which extend through the stator ring and are hydraulically expanded to be applied firmly in the recesses, this being intended to provide for better heat transfer. While cooling in accordance with the procedure referred to by way of example hereinbefore is generally deemed to be operable in practice nonetheless the required apparatus expenditure and also the amount of time required for fitting the tubes and for expanding the tubes is found to be a disadvantage. In addition in the case of some types of generator there is the possibility of operating with air cooling instead of liquid cooling.

A principle involved in air cooling is known for example from WO 2010/040659 A2. It is proposed therein that a plurality of cooling passages which have a radial afflux flow are provided in an outer carrier structure of the stator ring, which cooling passages cooperate with a stator bell for providing a pressure chamber with an increased pressure or a reduced pressure to provide an air flow. The cooling concept set forth therein is deemed to be satisfactory in terms of its mode of operation. Nonetheless there is still a need to further improve the cooling efficiency aspects in a generator and a stator of the kind set forth in opening part of this specification.

BRIEF SUMMARY

Provided is a stator ring with an improved possibility of cooling.

In particular at least one embodiment of the stator ring has a plurality of grooves for receiving the stator winding, and a magnetic yoke adjacent to the grooves, wherein the stator ring in the region of the magnetic yoke has a plurality of cooling recesses through which cooling air can flow and wherein the stator ring has a plurality of stator plates which are stacked in succession in the axial direction of the stator ring, wherein the cooling recesses extend through all stator plates.

The magnetic yoke preferably has a first region directly adjacent to the grooves, and a radially further outwardly disposed second region which is referred to as an enlarged magnetic yoke. In a preferred configuration the cooling recesses are arranged in the enlarged magnetic yoke.

Heat dissipation is effected at its most efficient where it occurs.

The higher efficiency in terms of heat dissipation compensates for the power losses which are accepted due to the disturbances, which arise in particular out of the preferred developments of the invention.

An advantageous provides that cooling ribs for increasing the surface area are provided in one, more of all of the cooling recesses.

In a preferred embodiment the cooling recesses are in the form of slots. Preferably the long sides of the slots extend in the radial direction of the stator ring. The term slot is also used in accordance with the invention to mean those recesses, the ends of which are not of a semicircular configuration. Therefore recesses of a rectangular cross-section, possibly also with rounded corners, are also deemed to be slots.

Preferably at least two cooling recesses of the plurality of cooling recesses are separated from each other by a web, the highest thickness of which in the peripheral direction of the stator ring is preferably equal to or less than the internal width of the cooling recesses in the peripheral direction. The web which is dimensioned in that way therefore also functions as a cooling rib, in addition to its supporting function.

In a preferred embodiment the stator ring has a plurality of sets each comprising at least two cooling recesses separated from each other by a web. In preferred alternative embodiments there is preferably one set for each third groove or particularly preferably one set for each second groove or alternatively and particularly preferably one set for each groove.

The spacing between two sets of cooling recesses is preferably greater than the spacing between two cooling recesses which are adjacent within a set.

The highest thickness of the web between two cooling recesses within a set in the peripheral direction of the stator ring is preferably equal to or less than the internal width of the cooling recesses in the peripheral direction.

In a further preferred embodiment of the stator ring the cooling recesses are arranged displaced in the peripheral direction relative to the grooves. The displaced arrangement of the cooling recesses relative to the grooves provides for a very uniform flow of heat, when the cooling recess is of a sufficiently large size.

In a preferred embodiment of the stator ring the surface of the cooling recesses is contoured in such a way that the production of turbulence effects within the cooling recesses is promoted. The formation of a turbulent air flow within the cooling recesses provides for an increase in the heat transfer from the air to the surface of the cooling recesses. Preferably the contour in the configuration having a plurality of stator plates stacked in succession is produced by means of a displacement in a radial direction and/or in a peripheral direction of the cooling recesses between adjacent stator plates. By virtue of the displacement, the surface of the cooling recesses is roughened, when considered technically.

In a further aspect the invention concerns an electric generator, in particular a synchronous generator or ring generator of a wind turbine, having a rotor and a stator, wherein the stator has a stator ring. In accordance with that aspect the stator ring is designed in accordance with one of the above-described preferred embodiments.

In a first preferred embodiment of the generator the rotor is in the form of an internal rotor. In a second preferred embodiment the rotor of the generator is in the form of an external rotor.

In a further aspect the present invention concerns a wind turbine, in particular a gear-less wind turbine, having an electric generator, in particular a synchronous generator or ring generator. In the case of such a wind turbine the generator is designed in accordance with one of the embodiments described herein.

Preferably the wind turbine has at least one motor-driven, preferably electric motor-driven fan for producing a cooling air flow through the cooling recesses of the stator ring.

DETAILED DESCRIPTION

FIG. 1shows a wind turbine100having a tower102and a pod104. Arranged at the pod104is a rotor106having three rotor blades108and a spinner110. The rotor106is caused to rotate by the wind in operation and thereby drives a generator1(FIG. 2) in the pod104.

The pod104is shown inFIG. 2. The pod104is mounted rotatably to the tower102and connected in driven relationship in generally known manner by means of an azimuth drive7. In also generally known manner provided in the pod104is a machine carrier9which holds a synchronous generator1. The synchronous generator1is designed in accordance with the present invention and is in particular a slowly rotating, multi-pole synchronous ring generator. The synchronous generator1has a stator3and an internal rotor5, also referred to as the rotor member of the generator. The rotor or rotor member5is connected to a rotor hub13which transmits the rotational movement of the rotor blades108, caused by the wind, to the synchronous generator1.

FIG. 3shows the stator3on its own. The stator3has a stator ring16having an inner peripheral surface18. Provided in the inner peripheral surface18is a plurality of grooves17which are adapted to receive the stator winding in the form of conductor bundles.

As can be seen from the cross-sectional view inFIG. 4the stator ring16of the stator3has a stator winding in a first radial region W. The stator winding is disposed in the form of conductor bundles12in the grooves17which extend from the inner peripheral surface18. The magnetic yoke J is provided adjacent to the region W. In the case of the illustrated generator1with an internal rotor, indicated by a rotor5which moves in the peripheral direction U within the stator ring16, the magnetic yoke J is radially outside the region W having the stator winding. In an alternative generator which is also in accordance with the invention and having an external rotor (not shown), the rotor would rotate radially outside the stator and accordingly the magnetic yoke would be arranged radially within the region of the stator windings adjacent thereto. An additional view has been dispensed with at this juncture for the sake of clarity. An air gap S is provided between the stator3and the rotor5.

A plurality of sets15of cooling recesses19(seeFIGS. 5 and 6) are provided in the stator ring16in the region J of the magnetic yoke. A set15of cooling recesses can include one or more cooling recesses. A respective set of cooling recesses can be respectively provided for one, two, three, four or more than four grooves.

The diagrammatic partial view inFIG. 4ashows the division of the magnetic yoke J into a first region J1and a radially outwardly adjoining second region J2. The second region J2is interpreted as the enlarged magnetic yoke. The cooling recesses are preferably arranged in the second region J2. In the present embodiment by way of example a respective set15of cooling recesses is associated with three grooves.

FIGS. 5 and 6show various details of the invention in isolation from each other. It is assumed in accordance with the invention however that the individual features which are respectively shown only in one of the embodiments by way of example can also be combined with the features of the other embodiments.FIGS. 5 and 6do not show a curvature of the stator ring13. The illustrated details apply both to generators with an internal rotor and also with an external rotor.

FIG. 5firstly shows a set15comprising two cooling recesses19. The cooling recesses19are spaced from each other in the peripheral direction and are arranged in displaced relationship with the grooves17. Each of the recesses19shown inFIG. 5has a plurality of cooling ribs61.

FIG. 6shows in total three sets15respectively having two cooling recesses19, wherein each set15is associated with a groove17. The sets15with the cooling recesses19are not displaced relative to the grooves17respectively associated therewith.

The cooling recesses19within a respective set are spaced from each other by a thin web20. As its widest location the web20is of a thickness23which is less than a spacing25between the cooling recesses19of adjacent sets. Preferably the width23of a respective web is less than or equal to the width in the peripheral direction of one of the cooling recesses19.

FIG. 7shows a section along line A-A inFIG. 6. The stator plate packets16a,16b,16c,16d,16e,16f, . . .16nare displaced relative to each other in the radial direction in such a way that the inner surface of the cooling recess19is roughened. The displacement27can be slight. A displacement of a few millimeters already promotes heat exchange between the cooling air in the cooling recess19and the stator plates16a-16n. The stator plates overall do not have to be displaced relative to each other, for such a configuration. It is sufficient if the respective cooling recesses19a-19nwhich extend through the individual plates16a-16nare slightly displaced relative to each other.

As can be seen from the foregoing the cooling recesses19can be of a smooth-walled configuration as shown inFIG. 5. Equally the cooling recesses19could be provided with cooling ribs as shown inFIG. 6. More than two cooling recesses can be provided within a set15of cooling recesses, and a set15of cooling recesses19can be associated with a number of grooves17, differing fromFIGS. 5 and 6.