Lamination stack for an electrical machine stator

An electrical machine stator is disclosed that includes a stack of laminations configured to be assembled together so as to define at least one stator tooth. The stack of laminations may include a plurality of nesting laminations and a plurality of shim laminations. Each nesting lamination may include a first edge section, a second edge section and a middle section extending between the first and second edge sections. At least one of the first edge section and the second edge section of each nesting lamination may be configured to be engaged against at least one of the first edge section and the second edge section of an adjacent nesting lamination when the stack of laminations is assembled together. Additionally, at least one shim lamination may be disposed between each pair of adjacent nesting laminations.

FIELD OF THE INVENTION

The present subject matter relates generally to electrical machines and, more particularly, to a lamination stack for an electrical machine stator that includes a plurality of laminations configured to increase the torque and/or shear carrying capability of the lamination stack.

BACKGROUND OF THE INVENTION

An electrical machine, such as a generator or motor, generally includes a stator and a rotor configured to convert mechanical power to electrical power or vice versa. The stator typically includes a plurality of stator teeth configured to receive coils or windings wrapped around the outer perimeter thereof. The rotor may generally be configured to be rotated such that one or more magnets attached to and/or forming part of the rotor rotate relative to the fixed windings. The relative rotation between the magnet(s) and the windings creates a rotating magnetic field, thereby inducing an electromotive force within the stator.

As is generally understood, the stator of an electrical machine is typically formed from a plurality of laminations of a material having good electromagnetic properties (e.g., silicon steel). The laminations are stacked axially together to form the stator and may often be bolted together. Typically, each lamination is configured as a flat, planar sheet. Thus, when the laminations are stacked together, the amount of torque and/or shear that can be transferred through the lamination stack is limited. Specifically, during operation of an electrical machine, a significant amount of torque and/or shear is transmitted between the rotor and stator. However, due to the flat or planar configuration of conventional laminations, such laminations often slide or move relative to one another when torque and/or shear is applied through the stator. This relative sliding can impact the electromagnetic performance of the electrical machine and can also result in damage to the stator.

Accordingly, a lamination stack with improved structural stiffness that allows for an increased amount of torque and/or shear to be transferred through the stack would be welcomed in the technology.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, the present subject matter discloses an electrical machine stator. The stator may generally include a stack of laminations configured to be assembled together so as to define at least one stator tooth. The stack of laminations may include a plurality of nesting laminations and a plurality of shim laminations. Each nesting lamination may include a first edge section, a second edge section and a middle section extending between the first and second edge sections. At least one of the first edge section and the second edge section of each nesting lamination may be configured to be engaged against at least one of the first edge section and the second edge section of an adjacent nesting lamination when the stack of laminations is assembled together. Additionally, at least one shim lamination may be disposed between each pair of adjacent nesting laminations.

In another aspect, the present subject matter discloses a generator for a wind turbine. The generator may generally include a stack of laminations configured to be assembled together so as to define at least one stator tooth. The stack of laminations may include a plurality of nesting laminations and a plurality of shim laminations. Each nesting lamination may include a first edge section, a second edge section and a middle section extending between the first and second edge sections. At least one of the first edge section and the second edge section of each nesting lamination may be configured to be engaged against at least one of the first edge section and the second edge section of an adjacent nesting lamination when the stack of laminations is assembled together. Additionally, at least one shim lamination may be disposed between each pair of adjacent nesting laminations.

In a further aspect, the present subject matter discloses a wind turbine including a tower and a nacelle mounted on top of the tower. The wind turbine may also include a rotor hub coupled to the nacelle. The rotor hub may include a plurality of rotor blades extending therefrom. Additionally the wind turbine may include a generator housed within the nacelle. The generator may generally include a stack of laminations configured to be assembled together so as to define at least one stator tooth. The stack of laminations may include a plurality of nesting laminations and a plurality of shim laminations. Each nesting lamination may include a first edge section, a second edge section and a middle section extending between the first and second edge sections. At least one of the first edge section and the second edge section of each nesting lamination may be configured to be engaged against at least one of the first edge section and the second edge section of an adjacent nesting lamination when the stack of laminations is assembled together. Additionally, at least one shim lamination may be disposed between each pair of adjacent nesting laminations.

DETAILED DESCRIPTION OF THE INVENTION

The present subject matter is generally directed to a stator for an electrical machine, such as a generator. In particular, the present subject matter is directed to a plurality of laminations having nesting features configured such that the nesting features of adjacent laminations are engaged against one another when the laminations are stacked axially together to form the stator. By designing the laminations to include such nesting features, the torque and/or shear carrying capability of the lamination stack may be significantly increased. For example, the nesting features of the laminations may be designed so that adjacent laminations are radially and/or circumferentially engaged with one another, thereby increasing the radial and/or circumferential stiffness of the lamination stack and increasing the amount of torque and/or shear that can be transferred through the lamination stack.

In several embodiments, it should be appreciated the present subject matter may be advantageously utilized with compact generators having laminations that must be capable of resisting large, electromagnetic or structural loads. For example, as will be described below, the disclosed laminations may be advantageously used to form the stator of a wind turbine generator, such as a yokeless wind turbine generator (e.g., a double-sided wind turbine generator) that does not have a separate frame providing structural support to the laminations. Specifically, the laminations of such generators must be capable of resisting substantial electro-magnetic and structural loads (e.g., wind-induced loads). Thus, the nesting features of the disclosed laminations may permit the overall stiffness of the lamination stack to be increased, thereby improving the ability of the laminations to carry such loads. However, it should be appreciated that application of the present subject matter need not be limited to compact generators or generators for wind turbines. Rather, the disclosed laminations may be utilized with electrical machines in any suitable application to increase the torque and/or shear carrying capability of the lamination stack.

Referring now to the drawings,FIG. 1illustrates an axial, front view of one embodiment of an electrical machine10. As shown, the electrical machine10is configured as a double-sided, permanent magnet (PM) generator and, thus, includes a rotor12having an outer rotor portion14and an inner rotor portion16. A plurality of outer magnets18may extend radially inwardly from the outer rotor portion14. Similarly, a plurality of inner magnets20may extend radially outwardly from the inner rotor portion16. As is generally understood, the rotor12may be coupled to a rotational input source (not shown) configured to rotate the inner and outer rotor portions14,16. For example, in embodiments in which the electrical machine10is configured as a generator for a wind turbine, the rotor12may be coupled to the rotor hub and, thus, the rotor blades of the wind turbine via a rotor shaft.

By increasing the torque and/or shear carrying capability of a lamination stack, numerous advantages may be provided to an electrical machine stator. For example, an increased torque and/or shear carrying capability may reduce the amount of radial and circumferential (or tangential) deflection of the lamination stack due to electromagnetic loads. Moreover, an increased torque and/or shear carrying capability may also prevent adjacent laminations from slipping and/or sliding relative to one another when the lamination stack is subject to electromagnetic loads. Specifically, the disclosed nesting features may serve to radially and/or circumferentially lock adjacent laminations together, thereby reducing the need to support all the electromagnetic loads within the lamination stack by friction only. As a result, the axial bolts used to preload the laminations in order to hold the stack together in compression may be reduced in size and/or strength, which may, in turn, reduce the overall cost of the lamination stack and/or allow for a reduction in the overall stack size.

Additionally, the electrical machine10may include a stator22fixed in position relative to the rotor12. For example, the stator22may be coupled to a stationary frame (not shown) of the electrical machine10. As shown in the illustrated embodiment, the stator22is configured as a double-sided stator and includes a plurality of teeth24,26extending radially inwardly and radially outwardly from an annular, bridge portion28. Specifically, a plurality of outer teeth24may extend radially outwardly from the bridge portion28, with each outer tooth24being configured to receive an outer stator coil or winding30, such as by wrapping each outer stator winding30around each outer tooth24. Similarly, a plurality of inner teeth26may extend radially inwardly from the bridge portion28, with each inner tooth26being configured to receive an inner stator coil or winding32, such as by wrapping each inner stator winding32around each inner tooth26. For purposes of illustrating the stator teeth30,32, the outer and inner stator windings30,32are only shown as being received on the inner and outer stator teeth30,32around a portion of the circumference of the stator22.

The stator22may generally be disposed concentrically between the inner and outer rotor portions14,16. As such, at least two concentric air gaps34,36may be defined between the stator22and the inner and outer rotor portions14,16. For example, an inner air gap34may be defined between the inner rotor portion16and an inner edge38of each inner tooth26and an outer air gap36may be defined between the outer rotor portion14and an outer edge40of each outer tooth24.

Additionally, as shown in the illustrated embodiment, the stator22is configured as a yokeless stator. Thus, in several embodiments, an axial end (not shown) of the stator22may be mounted to a stationary frame of the electrical machine10. For example, the stator22may be mounted to the stationary frame using one or more bolts42extending axially through the bridge portion28of the stator22. Moreover, as will be described below, the bridge portion22, the inner teeth26and the outer teeth24of the stator22may generally be formed from a lamination stack comprising a plurality of laminations stacked axially together. Thus, in addition to mounting to the stator22to the stationary frame, the bolts42may also provide uniform compression of the lamination stack in the axial direction.

During operation of the electrical machine10, the rotor12is rotated such that the magnets18,20extending from the outer and inner rotor portions14,16rotate relative to the stator windings30,32received on the outer and inner stator teeth24,26. As is generally understood, such rotation of the rotor12may create a rotating magnetic field which induces an electromotive force within the stator22.

It should be appreciated that the electrical machine10shown inFIG. 1is simply provided for illustrative purposes to place the present subject matter within an exemplary field of use. Thus, the electrical machine10need not be configured as a double-sided, PM generator, but, rather, may generally be configured as any suitable electrical machine. Specifically, in alternative embodiments, the electrical machine10may comprise any single-sided electrical machine, any double-sided electrical machine, any non-PM electrical machine (e.g., wound field synchronous machines and switched or synchronous reluctance machines) and any other electrical machine known in the art.

Similarly, it should be appreciated that the disclosed stator22need not be limited to the double-sided, yokeless stator shown inFIG. 1. Rather, the configuration of the stator22may generally vary depending on the configuration of the electrical machine10. For example, in embodiments in which the electrical machine10is configured as a single-sided electrical machine, the stator22may be configured as a single-sided stator and, thus, may only comprise stator teeth24,26extending radially inwardly or radially outwardly from the annular bridge portion28. Additionally, in such embodiments, the stator22may include a conventional yoke (not shown) configured to carry the circumferential component of the magnetic flux linking the stator teeth24,26. For instance, in one embodiment, the annular bridge portion28of the stator22may be configured as the stator yoke. In other embodiments, the stator22need not be formed from a single, annular shaped lamination stack, but may be formed from a plurality of separate lamination stacks. For instance, in a particular embodiment, the stator22may comprise a plurality of separate tooth modules mounted in an annular array about a stator frame or plate. Suitable examples of stators formed from separate lamination stacks are provided in U.S. Pat. No. 7,692,357 (Qu et al) and U.S. Pat. No. 7,839,049 (Jansen et al), assigned to the General Electric Company.

Referring now toFIGS. 2 and 3, there is illustrated one embodiment of a lamination stack100having a plurality of laminations102that may be stacked axially or otherwise assembled together to form at least a portion of an electrical machine stator22(FIG. 1). In particular,FIG. 2illustrates a partial, perspective view of the lamination stack100. Additionally,FIG. 3illustrates a cross-sectional view of the lamination stack100shown inFIG. 2taken along line3-3, particularly illustrating adjacent, nesting laminations102of the lamination stack100.

As shown, each lamination102is generally configured such that, when the laminations102are assembled together into the lamination stack100, a doubled-sided stator is formed. Thus, similar to that described above, the lamination stack102may generally include an annular bridge portion104(only a portion of which is shown) and a plurality of inner and outer stator teeth106,108extending radially inwardly and radially outwardly from the bridge portion104, respectively, (four of which are shown). As is generally understood, the bride portion104and teeth106,108of the lamination stack10may be partially defined/formed by corresponding features of each lamination102. For instance, as shown inFIG. 2, each individual lamination102may include an annular connecting portion110(only a portion of which is shown) corresponding to the bride portion104and a plurality of inner and outer projections112,114corresponding to the inner and outer stator teeth106,108. In general, each inner projection112may include an inner edge116and first and second side edges118,120extending radially between the inner edge116and the connecting portion110so as to define an axial portion of each inner stator tooth106. Similarly, each outer projection114may include an outer edge122and first and second side edges124,126extending radially between the outer edge122and the connecting portion110so as to define an axial portion of each outer stator tooth108.

Additionally, in accordance with aspects of the present subject matter, each lamination102may include a nesting feature128defined and/or extending between its first and second side edges118,120,124,126. In general, the nesting feature128of each lamination102may be configured to be engaged with the nesting features128of adjacent laminations102when the laminations102are assembled axially to form the lamination stack100. As such, adjacent laminations102of the lamination stack100may be radially and/or circumferentially engaged with one another, thereby increasing the radial and/or circumferential stiffness of the lamination stack100and, thus, increasing the torque and/or shear carrying capability of the lamination stack100.

As shown inFIGS. 2 and 3, in several embodiments, the nesting feature128may be configured as a curved profile128extending between the first and second side edges118,120,124,126of each lamination102. Specifically, at least a portion of each lamination102may be curved or arced such that the lamination102extends or projects outwardly in the axial direction (indicated by line130inFIGS. 2 and 3) between its first and second side edges118,120,124,126. For example, as shown in the illustrated embodiment, the inner and outer projections112,114, as well as the sections of the connecting portion110extending radially directly between the inner and outer projections112,114, may be curved or arced outwardly so as to define a continuous curved profile128between the first and second side edges118,120,124,126that extends radially between the inner and outer edges116,122of each lamination102. In such an embodiment, as particularly shown inFIG. 3, the sections of the connecting portion110not extending radially directly between the inner and outer projections112,114may be configured to define a generally flat or planar profile. However, it should be appreciated that, in other embodiments, the sections of the connecting portion110not extending directly between the inner and outer projections112,114may also be arced or curved (e.g., by being curved outwardly in the opposite axial direction130as the curved profile128defined in the inner and outer projections112,114) so that each lamination102defines a continuous curved profile around its entire circumference.

Regardless, each lamination102may be designed such that it nests together with and/or is otherwise radially and/or circumferentially engaged against an adjacent lamination102when the lamination stack100is assembled. For instance, as shown inFIG. 3, the curved profile128of each lamination102may be configured to mate with the curved profile128of adjacent laminations102, with each curved profile128defining an axial projection132on one side of the lamination102and an axial recess134on the opposing side of the lamination102. As such, the axial projection132of each lamination102may be configured to extend axially into the axial recess134of an adjacent lamination102when the laminations102are stacked axially together. Accordingly, adjacent laminations102of the lamination stack100may be radially and/or circumferentially engaged against one another, thereby increasing the radial and/or circumferential stiffness of the lamination stack100.

As particularly shown inFIG. 3, in one embodiment, the curved profile128of each lamination102may define a constant radius of curvature136between the first and second side edges118,120,124,126. In other embodiments, the radius of curvature136may vary between the first and second side edges118,120,124,126. For instance, as will be described below with reference toFIG. 4, the radius of curvature136may vary continuously between the first and second side edges118,120,124,126such that the curved profile128of each lamination102is wavy or undulating.

It should be appreciated that, as shown in the illustrated embodiment, the center of the curved profile128of each lamination102is generally oriented in the radial direction. As such, the adjacent laminations102may generally be circumferentially engaged with one another. However, in alternative embodiments, the center of the curved profile128of each lamination102may be oriented in the circumferential direction (so that adjacent laminations102may generally be radially engaged with one another) and/or may be angled relative to the circumferential and radial directions (so that adjacent laminations102may generally be both circumferentially and radially engaged with one another).

Moreover, as shown inFIG. 2, a plurality of bolt holes138may be defined through each lamination102. For example, in the illustrated embodiment, the bolt holes138are defined through the connecting portion110at locations between each inner and outer projection112,114. However, in alternative embodiments, the bolt holes138may be defined through each lamination102at any other suitable location. As is generally understood, the bolt holes138may be configured to receive an axially extending bolt or other suitable fastening mechanism (not shown) for mounting the lamination stack100to a stationary frame (not shown) of the electrical machine10.

It should be appreciated that, although the laminations102shown inFIGS. 2 and 3are configured to be assembled together to form a double-sided stator, the disclosed nesting feature128may generally be utilized in laminations configured to be assembled together to form any other suitable stator configuration, such as a single-sided stator or a stator comprising a plurality of separate lamination stacks. For instance,FIG. 4illustrates a perspective view of a plurality of laminations202that may be stacked axially or otherwise assembled together to form one of a plurality separate lamination stacks200of an electrical machine stator22(FIG. 1).

As shown inFIG. 4, the lamination stack200may generally comprise a stand-alone tooth module of an electrical machine stator22(FIG. 1) and, thus, may define a single stator tooth206configured to receive a suitable stator winding30,32(FIG. 1). Thus, each lamination202may generally include an inner edge216, an outer edge222and first and second side edges218,220extending radially between the inner and outer edges216,218, with the stator tooth206of the lamination stack200being partially defined between the first and second side edges218,220of each lamination202. Additionally, similar to the embodiment described above with reference toFIGS. 2 and 3, the laminations102may include corresponding nesting features228(i.e., curved profiles228) defined and/or extending between their first and second side edges218,220so that the curved profile228of each lamination202projects axially into and/or is axially received by the curved profile228of adjacent laminations202. As such, adjacent laminations202may be radially and/or circumferentially engaged with one another, thereby increasing the radial and/or circumferential stiffness of the lamination stack202.

However, unlike the curved profiles128described above, the radius of curvature236of each lamination202generally varies between the first and second side edges218,220. Specifically, as shown, the radius of curvature236may be varied such that a portion of each lamination202projects and/or extends in both the positive and negative axial directions (indicated by the opposed arrows of line130) between the first and second side edges218,220. As a result, each lamination may generally define a wavy or undulating, curved profile228between its side edges218,220.

Additionally, as shown inFIG. 4, one or more bolt holes238may be defined through each lamination202for receiving a bolt or other suitable fastening mechanism (not shown). For example, in the illustrated embodiment, each lamination202includes four bolt holes238, with each bolt hole238being defined thorough a side tab240projecting outwardly from the first or second side edge218,220at and/or adjacent to the outer or inner edge216,222of each lamination202. However, in other embodiments, any other suitable number of bolt holes238may be defined through each lamination202at any other suitable location.

Referring now toFIGS. 5 and 6, there is illustrated another embodiment of a lamination stack300having a plurality of laminations302that may be stacked axially or otherwise assembled together to form at least a portion of an electrical machine stator22(FIG. 1). In particular,FIG. 5illustrates a partial, perspective view of the lamination stack300. Additionally,FIG. 6illustrates a cross-sectional view of the lamination stack300shown inFIG. 5taken along line6-6, particularly illustrating adjacent, nesting laminations302of the lamination stack300.

In general, the lamination stack300may be configured the same as or similar to the lamination stack100described above with reference toFIGS. 2 and 3. For example the lamination stack300may generally include an annular bridge portion304(only a portion of which is shown) and a plurality of inner and outer stator teeth306,308extending radially inwardly and radially outwardly from the bridge portion304, respectively, (four of which are shown), with such features of the lamination stack300being partially defined or formed by corresponding features of each lamination302. Specifically, as shown in the illustrated embodiment, each individual lamination302may include an annular connecting portion310(only a portion of which is shown) corresponding to the bride portion304and a plurality of inner and outer projections312,314corresponding to the inner and outer stator teeth306,308. In general, each inner projection312may include an inner edge316and first and second side edges318,320extending radially between the inner edge316and the connecting portion210so as to define an axial portion of each inner stator tooth306. Similarly, each outer projection314may include an outer edge322and first and second side edges324,326extending radially between the outer edge320and the connecting portion310so as to define an axial portion of each outer stator tooth308.

Additionally, each lamination302may include a nesting feature328defined and/or extending between its first and second side edges318,320,324,326such that adjacent laminations320may be engaged with one another when the laminations302are assembled together to form the lamination stack300. However, unlike the nesting features128,228described above (i.e., the curved profiles), the nesting feature328may comprise one or more channels328extending lengthwise at least partially between the inner and outer edges316,322of each lamination302, with each channel328being spaced apart from the first and second side edges318,320,324,326. For instance, in the illustrated embodiment, each lamination302defines three channels328extending between its inner and outer edges316,322and being spaced apart from the first and second side edges318,320,324,326. However, in alternative embodiments, each lamination302may define any other suitable number of channels328, such as less than three channels328or greater than three channels328.

As shown inFIG. 5, one embodiment, the channels328may be configured to extend radially between the inner and outer edges316,322, such as by extending lengthwise substantially perpendicular to the inner and outer edges316,322and/or substantially parallel to the first and second side edges318,320,324,326. However, in alternative embodiments, the channels328may extend lengthwise at an angle relative to the inner and outer edges316,322and/or the first and second side edges318,320,324,326and/or the channels328may extend circumferentially between the first and second side edges318,320,324,326, such as by extending lengthwise substantially perpendicular to the first and second side edges318,320,324,326and/or substantially parallel to the inner and outer edges316,322. Additionally, as shown in the illustrated embodiment, the channels328may be configured to extend along an entire radial height342of each inner and outer projection312,314(e.g., the entire radial height342of each stator tooth306,308), such as by extending radially along the distance defined between the inner and outer edges316,322of each lamination302. In other embodiments, the channels328may only be configured to extend along a portion of the radial height342of each inner and outer projection312,314.

As particularly shown inFIG. 6, each channel328formed may be configured to project or extend outwardly in the axial direction (indicated by line130). As such, each channel328may be designed so that it nests together with or is otherwise engaged against a corresponding channel328of an adjacent lamination302when the lamination stack302is assembled. For instance, as shown in the illustrated embodiment, each channel328may define an axial projection332on one side of each lamination302and an axial recess334in the opposing side of the lamination302. As such, the axial projection332of each channel328may be configured to extend axially into the axial recess334of an adjacent channel328when the laminations302are stacked axially together. Accordingly, adjacent laminations302of the lamination stack300may be radially and/or circumferentially engaged against one another, thereby increasing the radial and/or circumferential stiffness of the lamination stack300.

It should be appreciated that, although the laminations302shown inFIGS. 5 and 6are configured to be assembled together to form a double-sided stator, the disclosed nesting features328(e.g., the channels328) may generally be utilized in laminations configured to be assembled together to form any other suitable stator configuration, such as a single-sided stator or a stator comprising a plurality of separate lamination stacks. For instance, referring back toFIG. 4, as an alternative to the curved profile, one or more channels328may be formed in each lamination202, such as by forming channels328in each lamination202that extend radially between the lamination's inner and outer edges216,222.

Referring now toFIGS. 7 and 8, there is illustrated another embodiment of a lamination stack400having a plurality of laminations402that may be stacked axially or otherwise assembled together to form at least a portion of an electrical machine stator22(FIG. 1). In particular,FIG. 7illustrates a partial, perspective view of the lamination stack400. Additionally,FIG. 8illustrates a cross-sectional view of the lamination stack400shown inFIG. 7taken along line8-8, particularly illustrating adjacent, nesting laminations402of the lamination stack400.

In general, the lamination stack400may be configured the same as or similar to the lamination stacks100,300described above with reference toFIGS. 2,3,5and6. For example the lamination stack400may generally include an annular bridge portion404(only a portion of which is shown) and a plurality of inner and outer stator teeth406,408extending radially inwardly and radially outwardly from the bridge portion404, respectively, (four of which are shown), with such features of the lamination stack400being partially defined or formed by corresponding features of each lamination402. Specifically, as shown in the illustrated embodiment, each individual lamination402may include an annular connecting portion410(only a portion of which is shown) corresponding to the bride portion404and a plurality of inner and outer projections412,414corresponding to the inner and outer stator teeth406,408. In general, each inner projection412may include an inner edge416and first and second side edges418,420extending radially between the inner edge416and the connecting portion410so as to define an axial portion of each inner stator tooth406. Similarly, each outer projection414may include an outer edge422and first and second side edges424,426extending radially between the outer edge422and the connecting portion410so as to define an axial portion of each outer stator tooth408.

Additionally, each lamination402may include a nesting feature428defined and/or extending between its first and second side edges418,420,424,426such that adjacent laminations402may be engaged with one another when the laminations402are assembled together to form the lamination stack400. However, unlike the nesting features128,228,328described above, the nesting feature428may comprise one or more dimples428formed in each lamination402. For instance, as shown inFIG. 7, a plurality of dimples428may be spaced apart between the inner and outer edges416,422and the first and second side edges418,420,424,426of each lamination402. In several embodiments, the dimples428may be formed in each lamination402so as to define a pattern, such as by being aligned in rows or columns extending radially and/or circumferentially between the first and second side edges418,420,424,426of each lamination402. However, in alternative embodiments, the dimples428may be randomly formed in each lamination402.

In general, each dimple428may be configured to project or extend outwardly in the axial direction (indicated by line130). As such, each dimple428may be designed so that it nests together with or is otherwise engaged against a corresponding dimple428of an adjacent lamination402when the lamination stack400is assembled. For instance, as shown in the illustrated embodiment, each dimple428may define an axial projection432on one side of each lamination402and an axial recess434in the opposing side of the lamination402. As such, the axial projection432of each dimple428may be configured to extend axially into the axial recess334of an adjacent dimple428when the laminations402are stacked axially together. Accordingly, adjacent laminations402of the lamination stack400may be radially and/or circumferentially engaged against one another, thereby increasing the radial and/or circumferential stiffness of the lamination stack400.

It should be appreciated that the dimples428may generally be formed in each lamination402so as to define any suitable shape. For example, as shown in the illustrated embodiment, each dimple428generally defines a circular shape. However, in alternative embodiments, the dimples428may define any other suitable shape, such as a rectangular or a triangular shape. Moreover, each dimple428may generally have any suitable dimensions, such as by defining any suitable circumferential width444and any suitable radial height446.

Additionally, it should be appreciated that, although the laminations402shown inFIGS. 7 and 8are configured to be assembled together to form a double-sided stator, the disclosed nesting features428(e.g., the dimples428) may generally be utilized in laminations configured to be assembled together to form any other suitable stator configuration, such as a single-sided stator or a stator comprising a plurality of separate lamination stacks. For instance, referring back toFIG. 4, as an alternative to the curved profile, one or more dimples428may be formed in each lamination202, such as by spacing apart a plurality of dimples428between the first and second side edges218,220of each lamination202.

Referring now toFIGS. 9 and 10, there is illustrated yet another embodiment of a lamination stack500having a plurality of laminations502that may be stacked axially or otherwise assembled together to form at least a portion of an electrical machine stator22(FIG. 1). In particular,FIG. 9illustrates a perspective view of the lamination stack500. Additionally,FIG. 10illustrates a cross-sectional view of the lamination stack500shown inFIG. 9taken along line10-10, particularly illustrating several adjacent, nesting laminations502of the lamination stack500.

As shown, the lamination stack500may generally be configured the same as or similar to the lamination stack200described above with reference toFIG. 4. For example, the lamination stack500may generally comprise a stand-alone tooth module of an electrical machine stator22(FIG. 1) and, thus, may define a single stator tooth506configured to receive a suitable stator winding30,32(FIG. 1). Thus, each lamination502may generally include an inner edge516, an outer edge522and first and second side edges518,520extending radially between the inner and outer edges516,522, with the stator tooth506of the lamination stack500being partially defined between the first and second side edges518,520of each lamination502.

In addition, each lamination502may include a nesting feature528defined between its first and second side edges518,520such that adjacent laminations502may be engaged with one another when the laminations502are assembled together to form the lamination stack500. However, unlike the nesting features128,228,328,328described above, the nesting feature528may comprise an axially projecting bend528extending between the first and second side edges518,520. For example, as shown inFIG. 10, each lamination502may be formed so that the bend528is spaced axially apart from the inner and/or outer edges516,522, such as by being spaced apart from both edges516,522by an axial distance550. As such, the axial projecting bend528of each lamination502may be configured to be received within and/or received by the corresponding axially projecting bends528of adjacent laminations502. Accordingly, adjacent laminations502may be radially and/or circumferentially engaged against one another, thereby increasing the radial and/or circumferential stiffness of the lamination stack500.

It should be appreciated that the bend528formed in each lamination502may generally be configured to define any suitable angle552. For example, as shown inFIG. 10, in one embodiment, the angle552may be equal to about 90 degrees. However, in other embodiments, the angle552may be less than 90 degrees or greater than 90 degrees. Additionally, as shown inFIG. 9, in one embodiment, the bend528may be defined in each lamination so as to extend substantially perpendicularly between the first and second side edges518,520. In other embodiments, the bend528may extend at any other suitable angle between the first and second side edges518,520.

Moreover, as shown in the illustrated embodiment, the bend528is defined in each lamination502at a location generally equidistant from the inner and outer edges516,522. However, in alternative embodiments, the bend528may be spaced apart from the inner and outer edges516,522at varying distances, such as by being defined in each lamination502at a location closer to the inner edge516or at a location closer to the outer edge522.

Additionally, it should be appreciated that, although the laminations502shown inFIGS. 9 and 10are configured to be assembled together to form a stand-alone tooth module, the disclosed nesting feature528(e.g., the axially projecting bend528) may be utilized with laminations502configured to form any other suitable stator, such as a single- or double-sided stator. For instance, referring back toFIGS. 2 and 3, as an alternative to the curved profile, an axially projecting bend528may be formed in each lamination102that extends between the first and second side edges118,120,124,126.

Referring now toFIGS. 11 and 12, there is illustrated a further embodiment of a lamination stack600having a plurality of laminations602that may be stacked axially or otherwise assembled together to form at least a portion of an electrical machine stator22(FIG. 2). In particular,FIG. 11illustrates a perspective view of the lamination stack600. Additionally,FIG. 12illustrates a cross-sectional view of the lamination stack600shown inFIG. 11taken along line12-12, particularly illustrating several adjacent, nesting laminations602of the lamination stack600.

As shown, the lamination stack600may generally be configured the same as or similar to the lamination stacks200,500described above with reference toFIGS. 4,9and10. For example, the lamination stack600may generally comprise a stand-alone tooth module of an electrical machine stator22(FIG. 1) and, thus, may define a single stator tooth606configured to receive a suitable stator winding30,32(FIG. 1). Thus, each lamination602may generally include an inner edge616, an outer edge622and first and second side edges618,620extending radially between the inner and outer edges616,622, with the stator tooth606of the lamination stack600being partially defined between the first and second side edges618,620of each lamination602.

In addition, each lamination602may include a nesting feature628defined between its first and second side edges618,620such that adjacent laminations602may be engaged with one another when the laminations602are assembled together to form the lamination stack602. However, unlike the nesting feature528described above, the nesting feature628may comprise an axially projecting bend628extending between the inner and outer edges616,622. For example, as shown inFIG. 12, the bend628formed in each lamination602may extend between the inner and outer edges616,622so as to be spaced axially apart from the first and second side edges618,620, such as by being spaced apart from the side edges618,620by an axial distance650. As such, the axial projecting bend628of each lamination602may be configured to be received within and/or received by the corresponding axially projecting bends628of adjacent laminations602. Accordingly, adjacent laminations602may be radially and/or circumferentially engaged against one another, thereby increasing the radial and/or circumferential stiffness of the lamination stack600.

It should be appreciated that the bend628formed in each lamination602may generally define any suitable angle652. For example, as shown inFIG. 12, in one embodiment, the angle652may be equal to about 90 degrees. However, in other embodiments, the angle652may be less than 90 degrees or greater than 90 degrees. Additionally, as shown inFIG. 11, in one embodiment, the bend628may be defined in each lamination602so as to extend substantially perpendicularly between the inner and outer edges616,622. In other embodiments, the bend628may extend at any other suitable angle between the inner and outer edges616,622.

Moreover, as shown in the illustrated embodiment, the bend628is defined in each lamination602at a location generally equidistant from the first and second side edges618,620. However, in alternative embodiments, the bend628may be spaced apart from the first and second side edges618,620at varying distances, such as by being defined in each lamination602at a location closer to the first side edge618or at a location closer to the second side edge620.

Additionally, it should be appreciated that, although the laminations602shown inFIGS. 11 and 12are configured to be assembled together to form a stand-alone tooth module, the disclosed nesting feature628(e.g., the axially projecting bend628) may be utilized with laminations602configured to form any other suitable stator, such as a single- or double-sided stator. For instance, referring back toFIGS. 2 and 3, as an alternative to the curved profile, an axially projecting bend628may be formed in each lamination102that extends between inner and outer edges116,122and that is spaced apart between the first and second side edges118,120,124,126.

Referring now toFIGS. 13 and 14, there is illustrated yet another embodiment of a lamination stack700having a plurality of laminations702,703that may be stacked axially or otherwise assembled together to form at least a portion of an electrical machine stator22(FIG. 1). In particular,FIG. 13illustrates a perspective view of the lamination stack700. Additionally,FIG. 14illustrates a cross-sectional view of the lamination stack700shown inFIG. 13taken along line14-14, particularly illustrating several adjacent laminations702,703of the lamination stack700.

As shown, the lamination stack700may generally be configured the same as or similar to the lamination stacks200,500,600described above with reference to FIGS.4and9-12. For example, the lamination stack700may be configured as a stand-alone tooth module of an electrical machine stator22(FIG. 1) and, thus, may define a single stator tooth706configured to receive a suitable stator winding30,32(FIG. 1). However, unlike the embodiments described above, the lamination stack700is formed from laminations702,703having differing configurations. Specifically, as shown in the illustrated embodiment, the lamination stack700may include a plurality of nesting laminations702configured to be at least partially engaged with one another, with each nesting lamination702including a radially inner edge716, a radially outer edge722, a first radially extending edge section760, a second radially extending edge section762and a middle section764extending circumferentially (e,g., in the circumferential direction indicated by arrow780inFIG. 13) between the first and second edge sections760,762. Additionally, the lamination stack700may include a plurality of shim laminations703, with one or more of the shim laminations703being disposed between each pair of adjacent nesting laminations702. For example, as particularly shown inFIG. 14, a single shim lamination703may be disposed between the middle sections764of each pair of adjacent nesting laminations702such that the middle sections764are spaced apart by an axial distance766. However, in alternative embodiments, two or more shim laminations703may be disposed between the middle sections764of each pair of adjacent nesting laminations702. It should be appreciated that, in embodiments in which a single shim lamination703is disposed between adjacent nesting laminations702, the axial distance766may generally correspond to the thickness766of each shim lamination703.

In general, the first and/or second edge sections760,762of each nesting lamination702may be configured to be engaged against the first and/or second edge sections760,762of adjacent nesting laminations702when the laminations702,703are assembled together to form the lamination stack700. Thus, in several embodiments, the first and second edge sections760762may be configured to project or extend outwardly relative to the middle section760(e.g., by being bent relative to the middle section760) such that at least a portion of each edge section760,762extends across the axial distance766and overlaps a corresponding edge section760,762of an adjacent nesting lamination702. For example, as shown inFIG. 14, the first and second edge sections760,762may be oriented relative to the middle section764at an angle768such that at least a portion an inner surface710of each edge section760,762is engaged against and overlaps at least a portion of an outer surface710of the corresponding edge sections760,762of the adjacent nesting lamination702. As a result, each nesting lamination702may be radially (e.g., in the radial direction indicated by arrow782inFIG. 13) and/or circumferentially engaged against adjacent nesting laminations702, thereby increasing the radial and/or circumferential stiffness of the lamination stack700.

It should be appreciated that the angle768at which each edge section760,762must bent relative to the middle section764such that the edge sections760,762of adjacent nesting lamination702engage one another may generally vary depending on the axial distance766defined between the middle sections764of adjacent nesting laminations702and a thickness774of each nesting lamination702. For example, when the ratio of the axial distance766to the nesting lamination thickness774is equal to about 0.33:1, the angle768defined at each edge section760,762may generally be equal to about 40 degrees. Similarly, when the ratio of the axial distance766to the nesting lamination thickness774is equal to about 1:1, the angle768defined at each edge section760,762may generally be equal to about 60 degrees. As another example, when the ratio of the axial distance766to the nesting lamination thickness774is equal to about 2:1, the angle768defined at each edge section760,762may generally be equal to about 70 degrees and when the ratio is equal to about 5:1, the angle768defined at each edge section760,762may generally be equal to about 80 degrees. Thus, in several embodiments, the angle768defined at each edge section760,762may generally range from about 40 degrees to about 80 degrees (corresponding to a ratio of the axial distance766to the nesting lamination thickness774ranging from about 0.33:1 to about 5:1), such as from about 45 degrees to about 75 degrees or from about 60 degrees to about 70 degrees and all other subranges therebetween. However, in alternative embodiments, the angle768defined at each edge section760,762may be less than about 40 degrees or greater than about 80 degrees.

Additionally, it should be appreciated that, in several embodiments, the thickness (reference character766in the illustrated embodiment) of each shim lamination703may be equal to the thickness774of each nesting lamination702. In such embodiments, the axial distance to nesting lamination thickness ratio may be incrementally varied (e.g., from 1:1 to 2:1 or from 1:1 to 3:1) by varying the number of shim laminations703disposed between adjacent nesting laminations702(e.g., by varying the number from one shim lamination703to two shim laminations703or from one shim lamination703to three shim laminations703). However, in other embodiments, the thickness of each shim lamination703may vary from the thickness of each nesting lamination702.

Referring still toFIGS. 13 and 14, in several embodiments, each shim lamination703and the middle section764of each nesting lamination702may generally define a substantially flat or planar configuration. As such, the shim laminations703and middle sections764of the nesting laminations702may be positioned flush against one another when the laminations702,702are stacked together axially. Additionally, as particularly shown inFIG. 14, in one embodiment, a side edge776of each shim lamination703may have a beveled or tapered configuration so as to generally correspond to the orientation or angle768of the inner surfaces770of the edge sections760,762, thereby creating a flush interface between the side edges776and the inner surfaces770. However, in alternative embodiments, the side edges776may have any other suitable configuration and, thus, need not be designed so as to correspond to the orientation or angle768of the inner surfaces700of the edge sections760,762

Moreover, it should be appreciated that, although the transition defined between each side section760,762and the middle section764of each nesting lamination702is shown inFIGS. 13 and 14as being a sharp fold or bend (i.e. defining a sharp edge), a curved transition may also be defined between each side section760,762and the middle section764of each nesting lamination702. Additionally, it should be appreciated that, although the nesting and shim laminations702,703shown inFIGS. 13 and 14are configured to be assembled together to form a stand-alone tooth module, the laminations702,703may also be configured to form any other suitable stator, such as a single- or double-sided stator.

It should be appreciated that the disclosed nesting features128,228,328,428,528,628and/or edge sections760,762may generally be formed in each lamination102,202,302,402,502,602,702using any suitable manufacturing process. For example, in one embodiment, the nesting features and/or edge sections may be formed using a stamping or rolling process.

Referring now toFIGS. 15 and 16, there is illustrated one example of an electrical machine (i.e., a wind turbine generator) in which the disclosed laminations may be advantageously used. In particular,FIG. 15illustrates a partial, cross-sectional view of one embodiment of a wind turbine800having a generator802installed therein. Additionally,FIG. 16illustrates an enlarged, cross-sectional view of a portion of the wind turbine800shown inFIG. 15, particularly illustrating various components of the generator802.

As shown, the wind turbine800generally includes a nacelle804mounted on top of a tower806(only a portion of which is shown). In several embodiments, the nacelle804may include a nacelle frame808and a nacelle cover810. The nacelle frame808may generally be configured to be mounted to a portion of the tower806, such as through a conventional yaw bearing and gear drive system (not shown). The nacelle cover810may generally be configured to encompass the wind turbine components contained within the nacelle804, thereby protecting such components from the outside environment.

Additionally, the wind turbine800may include rotor hub812having a plurality of rotor blades814(only a portion of which is shown) extending therefrom. For example, in one embodiment, the wind turbine800may include three rotor blades814extending outwardly from the rotor hub812. However, in alternative embodiments, the wind turbine800may include less than three rotor blades814or greater than three rotor blades814. Moreover, in one embodiment, the rotor hub812may include a hub cover816configured to encompass various other rotor components of the wind turbine800(e.g., pitch drive assemblies and the like).

Further, the wind turbine800may also include a generator802mounted to the nacelle frame808via a main shaft and bearing assembly818. As shown in the illustrated embodiment, the generator802may be configured as a direct drive, double-sided permanent magnet (PM) generator. Thus, as particularly shown inFIG. 2, the generator802may include a rotor820having an outer rotor portion822and an inner rotor portion822. A plurality of outer magnets826may extend radially inwardly from the outer rotor portion822. Similarly, a plurality of inner magnets828may extend radially outwardly from the inner rotor portion825.

Additionally, the generator802may include a stator830fixed in position relative to the rotor820. For example, the stator830may be coupled to a stationary frame832of the generator802. As shown in the illustrated embodiment, the stator830is configured as a double-sided stator and, thus, includes an outer stator portion834and an inner stator portion836. The outer stator portion834may generally include a plurality of radially outwardly extending stator teeth (not shown), with each outer stator tooth being configured to receive an outer stator winding838. Similarly, the inner stator portion836may include a plurality of radially inwardly extending stator teeth (not shown), with each outer stator tooth being configured to receive an inner stator winding840.

It should be appreciated that the stator830may generally be concentrically disposed relative to the rotor820, such as by being concentrically disposed between the outer and inner rotor portions822,824. As such, at least two concentric air gaps842,844may be defined between the stator830and the inner and outer rotor portions822,824. For example, an inner air gap842may be defined between the inner rotor portion824and the inner stator portion836and an outer air gap844may be defined between the outer rotor portion822and the outer stator portion834.

During operation of the generator802, power output from the stator830may be controlled by a power converter unit (not shown) capable of full power conversion. A rotor shaft846may be coupled to the rotor820via a rotating frame848at one end and to a hub flange850at the other end, which may be coupled to the rotor hub812. As a result, rotation of the rotor blades814and, thus, the rotor hub812may rotate the rotor shaft846, thereby rotating the rotor820relative to the stator830. As is generally understood, such rotation of the rotor820may create a rotating magnetic field which induces an electromotive force within the stator830.

Additionally, as is generally understood, the stator820may be formed from a lamination stack852having a plurality of laminations (not shown) stacked axially together. As shown inFIG. 2, in one embodiment, the lamination stack852may be mounted to the stationary frame832using a plurality of bolts854extending axially through the lamination stack852. End plates856disposed at the axial ends of the lamination stack852, together with the heads of the bolts854, may be configured to provide uniform compression of the lamination stack852.

It should be appreciated that, in accordance with several embodiments of the present subject matter, the lamination stack852shown inFIG. 16may generally be configured the same as or similar to any of the lamination stacks100,200,300,400,500,600,700described above. Accordingly, the lamination stack852may include suitable nesting features128,228,328,428,528,628and/or suitable nesting laminations702configured to increase the radial and/or circumferential stiffness of the lamination stack852, thereby improving the torque and/or shear carrying capability of the lamination stack852.

It should also be appreciated that, although the illustrated wind turbine10is shown inFIGS. 15 and 16as including a direct drive, double-sided PM generator800, the wind turbine10may generally include any other suitable wind turbine generator known in the art, such as any suitable single-sided generator, any suitable non-PM generator (e.g., wound field synchronous machines and switched or synchronous reluctance machines) or any other suitable wind turbine generator (e.g., an indirectly driven generator). In such embodiments, the disclosed lamination stacks100,200,300,400,500,600,700may be utilized within such generator to form a stator having an increased torque and/or shear carrying capability.