Patent Description:
Generator is a component that converts mechanical power to electrical power in power generation industry. Generator typically includes a stator and a rotor each comprised of a plurality of electrical conductors, such as winding coils. During generator operation, the generator stator end winding coils are subjected to a variety of loading conditions that may adversely affect performance of the generator stator end wing coils and may lead to a premature failure. These loading conditions include thermo-mechanical forces, electro-mechanical forces causing steady state vibration, transient operating conditions and abnormal operating conditions such as three phase short circuits or out of phase synchronizations. These loading conditions lead to sever performance risks due to continued pressures of cost reduction and performance improvement.

Many of these loading conditions, however, conflict with each other. For example, increasing stiffness may help reduce steady state vibration magnitudes, but may also increase strain due to thermo-mechanical loads. Generator stators having design features that improve performance under one load condition may decrease performance under another load condition. Finding a right balance between these loading conditions and finding design features to achieve design and performance requirements is a challenge and valuable for generator stator design. Generator stators according to the state of the art are disclosed in documents <CIT> and <CIT>.

Briefly described, aspects of the present invention relate to a generator stator, an assembly and a method for supporting generator stator end winding coils.

An aspect of the invention is an end winding coil support assembly according to claim <NUM>.

An aspect of the invention is a method for supporting end winding coils of a generator stator according to claim <NUM>.

An aspect of the invention is a generator stator according to claim <NUM>.

Exemplary embodiments of the application are explained in further detail with respect to the accompanying drawings. In the drawings:.

A detailed description related to aspects of the present invention is described hereafter with respect to the accompanying figures.

<FIG> illustrates a schematic perspective partial view of a generator stator <NUM> having an end winding coil support assembly <NUM> according to an embodiment of the invention. The generator stator <NUM> has a stator core <NUM> and a core flange plate <NUM>. The core flange plate <NUM> is mounted at each axial end of the stator core <NUM>. The generator stator <NUM> has a plurality of end winding coils <NUM> extending outwardly from the core flange plate <NUM>. The stator core <NUM> and the end winding coils <NUM> circumferentially form a bore <NUM> for accepting a rotor (not shown). The end winding coils <NUM> are circumferentially enclosed by an inner support ring <NUM> and an outer support ring <NUM> which are axially spaced apart from each other. The outer support ring <NUM> is axially disposed outwardly from the inner support ring <NUM>. Outer braces <NUM> are axially disposed between the inner support ring <NUM> and outer support ring <NUM>. The outer braces <NUM> may be circumferentially spaced apart from each other around the end winding coils <NUM>. A plurality of holes <NUM> may be circumferentially disposed on the inner support ring <NUM> and the outer support ring <NUM> and axially disposed on the outer braces <NUM>. Bandages (not shown) may pass through the holes <NUM> and the end winding coils <NUM> for consolidating the end winding coils <NUM>.

The generator stator <NUM> includes a plurality of end winding coil support assemblies <NUM>. As shown in the exemplary embodiment of <FIG>, the end winding coil support assemblies <NUM> may be secured to the core flange plate <NUM>. The end winding coil support assemblies <NUM> may be circumferentially disposed along an outer peripheral surface of the core flange plate <NUM> and spaced apart from each other. The end winding coil support assemblies <NUM> extend axially outwardly from the core flange plate <NUM>. The end winding coil support assemblies <NUM> are attached to the inner support ring <NUM> for supporting the inner support ring <NUM>. The end winding coil support assemblies <NUM> may include holes <NUM>. Bandages (not shown) may pass through the holes <NUM> in the end winding coil support assemblies <NUM> and the holes <NUM> in the inner support ring <NUM> for further connection of the end winding coil support assemblies <NUM> to the inner support ring <NUM>. A total number of the end winding coil support assemblies <NUM> are determined to provide optimum performance of the generator stator <NUM>. For example, a total number of <NUM>, <NUM> or <NUM> end winding coil support assemblies <NUM> may be circumferentially disposed along the outer peripheral surface of the core flange plate <NUM> and the inner support ring <NUM>. Other total number of end winding coil support assemblies <NUM> may also be used. The end winding coil support assemblies <NUM> may also be attached to the outer support ring <NUM>. The end winding coil support assemblies <NUM> may also be attached to the end winding coils <NUM>.

The end winding coil support assembly <NUM> is described in detail with the following figures. <FIG> illustrates a schematic perspective view of a generator stator end winding support assembly <NUM> according to an embodiment of the invention. <FIG> illustrates a schematic exploded view of the generator stator end winding support assembly <NUM> as shown in <FIG>. <FIG> illustrates a schematic front view of the generator stator end winding support assembly <NUM> as shown in <FIG>. <FIG> illustrates a schematic side view of a generator stator end winding support assembly <NUM> as shown in <FIG>.

According to the exemplary embodiment shown in <FIG>, the end winding coil support assembly <NUM> includes a bracket <NUM>. The bracket <NUM> includes a first bracket plate <NUM> for securing the end winding coil support assembly <NUM> to the core flange plate <NUM> by fasteners <NUM>, such as bolts. The first bracket plate <NUM> may be secured to the core flange plate <NUM> by other means, such as by welding, or by dovetail joint. The first bracket plate <NUM> may be rigidly secured to the core flange plate <NUM>. The bracket <NUM> includes a second bracket plate <NUM> extending axially outwardly from the first bracket plate <NUM>. The second bracket plate <NUM> may be attached to the first bracket plate <NUM> as an integral piece, such as by welding. The second bracket plate <NUM> may be perpendicular to the first bracket plate <NUM>. The second bracket plate <NUM> may have an L-shape having a radial plate 214a extending radially and a tangential plate 214b extending tangentially. The bracket <NUM> may be made from austenitic steel.

The end winding coil support assembly <NUM> also includes a backup plate <NUM>. The backup plate <NUM> is arranged in parallel to the radial plate 214a of the L-shaped second bracket plate <NUM> forming a U-shaped space with an opening downward to the inner support ring <NUM>. A brace <NUM> is disposed between the backup plate <NUM> and the L-shaped second bracket plate <NUM> radially extending therethrough the U-shaped space downwardly. Lower section of the brace <NUM> may be L-shaped and interfaces with the inner support ring <NUM> in both axial and radial directions. The brace <NUM> may be connected to the inner support ring <NUM> by resin impregnated conformable layer that is placed in notches (not shown) in the inner support ring <NUM>. The lower section of the brace <NUM> may have hole <NUM> for additionally connection to the inner support ring <NUM> by bandages. Mat (not shown) may be disposed between the brace <NUM> and the inner support ring <NUM>. Resin impregnated conformable material may be used for this purpose. The brace <NUM> may be made from insulation materials so that no free floating potential occurs. The insulation materials may include glass-fabric material.

An elastic layer <NUM> is disposed around the brace <NUM> at interfaces between the brace <NUM> and the second bracket plate <NUM> and between the brace <NUM> and the backup plate <NUM>. The elastic layer <NUM> may be made from a material that has a compliant compression characteristic to a stress such that the elastic layer <NUM> is able to accommodate vibrations and damping of the generator stator <NUM> during operation. The elastic layer <NUM> may be made from materials, such as elastomers, viscoelastic, rubbers, silicon, Viton®, nitrile, or spring materials such as metals, composites, etc. The elastic layer <NUM> may be adhesively attached to the brace <NUM>, such as by glue. The elastic layer <NUM> may be bonded to the brace <NUM>.

At least one stud <NUM> extends through the radial plate 214a of the second bracket plate <NUM>, the backup plate <NUM>, the brace <NUM> and the elastic layer <NUM> for clamping said components together. The brace <NUM> includes an aperture <NUM> for the stud <NUM> extending therethrough. The aperture <NUM> is larger than a diameter of the stud <NUM> so that the brace <NUM> may be movable relative to the bracket <NUM> rigidly secured to the core flange plate <NUM> and thus the inner support ring <NUM> is movable relative to the bracket <NUM> secured to the core flange plate <NUM>. A plurality of studs <NUM> may be used for clamping the components together. A plurality of apertures <NUM> are arranged in the brace <NUM> for the studs <NUM> extending therethrough. The apertures <NUM> may be arranged in the brace <NUM> in a way to maximize distance between the apertures <NUM> for a strength consideration of the brace <NUM>. In the exemplary embodiment illustrated in <FIG>, the end winding coil support assembly <NUM> has three studs <NUM> extending therethrough the radial plate 214a of the second bracket plate <NUM>, the backup plate <NUM>, the brace <NUM> and the elastic layer <NUM>.

With reference to the front and side views of the embodiment of the end winding coil support assembly <NUM> as illustrated in <FIG>, a sleeve <NUM> is disposed in the aperture <NUM>. The sleeve <NUM> encloses the stud <NUM> extending therethrough the aperture <NUM>. The sleeve <NUM> is held between the radial plate 214a of the second bracket plate <NUM> and the backup plate <NUM> by a clamping force of the stud <NUM>. The sleeve <NUM> sets up a gap <NUM> at interfaces between the brace <NUM> and the radial plate 214a and between the brace <NUM> and the backup plate <NUM> in which the elastic layer <NUM> is disposed. The gap <NUM> defines a compression of the elastic layer <NUM> under stress induced in operation of the generator stator <NUM> such that the elastic layer <NUM> may accommodate vibrations and damping of the generator stator <NUM> during operation. Compression of the elastic layer <NUM> enables the brace <NUM> to move relative to the bracket <NUM> rigidly secured to the core flange plate <NUM> during operation. The inner support ring <NUM> connected to the brace <NUM> may move with the brace <NUM>. The end winding coil support assembly <NUM> may thus flexibly support the end winding coils <NUM>. The sleeve <NUM> may be made from materials which do not deform by the clamping force of the stud <NUM>.

During operation of the generator stator <NUM>, a plurality of different load conditions may be applied. Different load conditions require the end winging coil support assembly <NUM> to provide different flexibility and stiffness support. For example, flexibility is required to reduce variables, such as forces and resulting strains due to thermal expansion, while stiffness is required to control magnitudes of steady state vibration and to control variables, such as natural frequency of the end winging coil support assembly <NUM>. The end winding coil support assembly <NUM> uses a nonlinear nature of the elastic layer <NUM> to control these variables. The flexibility and stiffness of the support may be controlled by amount of compression of the elastic layer <NUM>. According to an embodiment, a clamping force of the stud <NUM> may be adjustable so that the sleeve <NUM> may set up a gap <NUM> for defining a compression of the elastic layer <NUM> based on load condition requirements. According to an embodiment, the elastic layer <NUM> may be selected to have a desired compression characteristic for controlling flexibility and stiffness support based on load condition requirements. According to an embodiment, thickness of the elastic layer <NUM> may be defined based on load condition requirements. For example, the elastic layer <NUM> may be a sheet of rubber. Thickness of the elastic layer <NUM> may be about <NUM>. Compression of the elastic layer <NUM> may also control strains due to abnormal operating conditions such as three phase circuits and control amount of damping of the end winging coil support assembly <NUM> for dynamic response.

An enlarged view of the aperture <NUM> is illustrated in <FIG>. The aperture <NUM> has a shape of two semi circles <NUM> axially oriented opposite to each other. The two semi circles <NUM> are connected by an axial section <NUM>. Each semi circle <NUM> has a radius that is larger than a radius of the sleeve <NUM>. The radius of the sleeve <NUM> is larger than a radius of the stud <NUM> extending therethrough. The larger dimension of the aperture <NUM> and the elastic layer <NUM> disposed around the brace <NUM> enable the brace <NUM> to be movable relative to the bracket <NUM> secured to the core flange plate <NUM> during operation. A gap <NUM> is arranged between an axial inboard end of the brace <NUM> and the first bracket plate <NUM> secured to the core flange plate <NUM> for tolerance of an axial movement of the brace <NUM>. Dimensions of the aperture <NUM>, the stud <NUM> and the sleeve <NUM> are determined based on load condition requirements. For example, a diameter of the stud <NUM> may be around <NUM>. A diameter of the sleeve <NUM> may be around <NUM>. A radius of each semi circle <NUM> may be around <NUM>. Length of the axial section <NUM> connecting the two semi circles <NUM> may be around <NUM>.

According to an aspect, the proposed generator stator end winding coil support assembly <NUM> may provide a balance between desired flexibility and stiffness support to the end winding coils <NUM> in different load conditions. The balance may be achieved by adjusting a clamping force of the stud <NUM> so that the sleeve <NUM> may set up a desired gap <NUM> to define a compression of the elastic layer <NUM>. The balance may be achieved by selecting the elastic layer <NUM> having a desired compression characteristic. The balance may be achieved by a desired thickness of the elastic layer <NUM>.

Claim 1:
An end winding coil support assembly (<NUM>) for supporting end winding coils (<NUM>) of a generator stator (<NUM>) comprising a stator core (<NUM>), a core flange plate (<NUM>) mounted at an axial end of the stator core (<NUM>) and an inner support ring (<NUM>) circumferentially enclosing the end winding coils (<NUM>) extending axially outwardly from the core flange plate (<NUM>),
the end winding coil support assembly assembly (<NUM>) comprising:
a bracket (<NUM>) rigidly secured to the core flange plate (<NUM>);
a backup plate (<NUM>);
a brace (<NUM>) disposed between the bracket (<NUM>) and the backup plate (<NUM>) and extending radially inwardly connected to the inner support ring (<NUM>); and
an elastic layer (<NUM>) disposed around the brace (<NUM>) at an interface between the bracket (<NUM>) and the backup plate (<NUM>),
wherein at least one stud (<NUM>) extends through the bracket (<NUM>), the brace (<NUM>), the elastic layer (<NUM>) and the backup plate (<NUM>) for clamping said components together,
wherein the brace (<NUM>) comprises an aperture (<NUM>) that is larger than a diameter of the stud (<NUM>) extending therethrough,
wherein a sleeve (<NUM>) is disposed in the aperture (<NUM>) and encloses the stud (<NUM>), wherein the aperture (<NUM>) of the brace (<NUM>) is larger than an outer diameter of the sleeve (<NUM>), wherein the aperture (<NUM>) comprises two semi circles (<NUM>) axially orientated opposite to each other and connected by an axial section (<NUM>), wherein radius of the semi circles (<NUM>) is larger than the outer radius of the sleeve (<NUM>),
wherein the sleeve (<NUM>) sets up a gap (<NUM>) at interfaces between the brace (<NUM>) and the bracket (<NUM>) and between the brace (<NUM>) and the backup plate (<NUM>) that defines a compression of the elastic layer (<NUM>) for accommodating vibration and damping during operation of the generator stator (<NUM>),
wherein the compression of the elastic layer (<NUM>) enables the brace (<NUM>) to be movable relative to the bracket (<NUM>) rigidly secured to the core flange plate (<NUM>) for flexibly supporting the end winding coils (<NUM>).