Modified attachment system for springs in a generator rotor

An assembly for use in a rotor of a turbine generator is provided that includes at least one creepage disposed on an upper load surface of copper windings. At least one slot spring is disposed on the creepage, and at least one amortisseur is disposed on the slot spring. A plurality of hollow locking members are disposed within apertures of the creepage, the slot spring, and the amortisseur. At least one slot wedge is disposed on the slot spring and the plurality of hollow locking members. At least one field retaining ring is disposed against one of the end portions of the rotor body and against the slot wedge.

FIELD

The present disclosure relates to electric generators and their rotors, and more specifically to mechanical attachment arrangements for components within a rotor of a turbine generator.

BACKGROUND

Within the structure of rotors for turbine generators, a number of components are secured within a longitudinal slot around and on top of the electrical windings. These components serve functions to insulate and secure the electrical windings within the rotor slot, interact with the rotating magnetic field, and also to provide for the passage of cooling gases through passageways in the components. Among the components within a rotor body or housing slot are electrical windings/coils (also referred to as “copper turns” in the industry), creepage members, amortisseurs, springs, and wedges. Generally, the creepage members provide electrical insulation or dielectric separation from the copper turns, the amortisseurs reduce or eliminate the possibility of axial current flow, and the springs provide a radial force to press the amortisseurs against the wedges, which hold the components within the slot.

Each of the components within the slot includes a series of openings or vent holes, which facilitate radial cooling by the flow of cooling gases. The openings in each of the components, when properly installed within the rotor slot, are aligned with each other in order to provide for an unobstructed and efficient flow of cooling gas. Often times, however, because of the heating and cooling cycles of the generator rotor, among other causes, the components within the rotor slot migrate outwardly over time, which causes the openings to be misaligned, thus blocking the flow of cooling gas. This blockage of the cooling passageways is undesirable for efficient and continuous operation of the rotor.

An exemplary rotor and the misalignment issue as described above are disclosed in U.S. Application No. 2013/0221797 titled “Amortisseur Assembly and Apparatus to Maintain Radial Venting Hole Alignment.” As shown inFIG. 1of this application, the rotor1includes slots2with vent holes opening to radial vent paths3. Also shown is a retaining ring4, which generally holds the components as described above within their respective longitudinal slots.

FIGS. 2A-2Dillustrate the issue of spring migration where a number of slot springs5have migrated outwardly from their nominal positions due to the heating and cooling cycles of the rotor during and between operation. Also shown in these figures are the electrical windings/coils6, the creepage members7, amortisseurs8, wedges9, vent holes10(which are misaligned as best shown inFIG. 2B), and the rotor body11containing the slots that house these components. The retaining ring as mentioned above is removed for clarity in these figures. Spring migration is undesirable because of the associated reduced operating output, vibration effects and down-time.

SUMMARY

In one form, an assembly for use in securing springs within a rotating generator rotor is provided that comprises a rotor defining an internal slot and opposed end portions, and copper windings disposed within the internal slot of the rotor body, wherein the copper windings defining internal gas passageways and an upper load surface. At least one creepage is disposed on the upper load surface of the copper windings, the creepage defining a plurality of apertures that are in alignment with the internal gas passageways of the copper windings. At least one slot spring is disposed on the creepage, the slot spring defining a plurality of apertures that are in alignment with the internal gas passageways of the copper windings, and at least one amortisseur is disposed on the slot spring, the at least one amortisseur defining a plurality of apertures that are in alignment with the internal gas passageways of the copper windings. A plurality of hollow locking members are disposed within apertures of the creepage, the slot spring, and the amortisseur, and the hollow locking members define upper flanges that are adapted to bear against the slot spring. At least one slot wedge is disposed on the slot spring and the plurality of hollow locking members, the slot wedge defining a plurality of apertures that are in alignment with the internal gas passageways of the copper windings. At least one field retaining ring is disposed against one of the end portions of the rotor body and against the slot wedge.

The teachings of the present disclosure also include a method of repairing a rotor of a turbine generator using the assembly as set forth above. It should also be understood that the present disclosure is not limited to the application of wind turbines and thus may be employed with electric generator rotors that experience similar misalignment of internal components while remaining within the scope of the present disclosure.

DETAILED DESCRIPTION

Referring toFIGS. 3A and 3B, an assembly for use in securing springs within a rotating generator of a turbine is illustrated and generally indicated by reference numeral20. The assembly20comprises a rotor body22(only half of which is shown), which defines an internal slot24and opposed end portions26and28. (It should be understood that only a portion of the length of the assembly20is illustrated for purposes of clarity due to the extensive length of the rotor). A number of components are disposed within the internal slot24of the rotor body22, which are also shown inFIGS. 5, 6A-C, and7A-C, and are now described in greater detail.

As shown, copper windings30are disposed within the internal slot24of the rotor body22. By passing DC current through the copper windings30, a magnetic field is generated during operation, which also generates a significant amount of heat, and thus the copper windings30define internal gas passageways32for cooling purposes. As further shown, the copper windings30also define an upper load surface34, on which additional components are disposed.

First, a creepage40is disposed on the upper load surface34of the copper windings30. The creepage40provides electrical insulation, or dielectric separation between the copper windings30other components within the rotor slot24. The creepage40in one form is a woven glass material. Like the copper windings30, the creepage40defines a plurality of apertures42that are in alignment with the internal gas passageways32of the copper windings42. As shown inFIG. 4, the creepage apertures42include a tapered or concave inlet44, which facilitates the flow of cooling gases and provides for additional cooling proximate the upper load surfaces34of the copper windings30. At least one creepage40is installed along the copper windings30, and in one form, seven (7) creepage elements40are included end-to-end along the entire length of the rotor body22.

Next, a slot spring50is disposed on the creepage40, which provides a biasing force to secure the components within the rotor slot24. The slot spring50also includes a plurality of apertures52that are in alignment with the internal gas passageways of the copper windings32, thus providing continuity for the flow of the cooling gases in a radial direction. At least one slot spring50is installed on the creepage40, and in one form, three (3) slot springs50are included end-to-end along the entire length of the rotor body22. The slot spring50in one form is a high-strength, corrosion resistant metal such as a Nickel Chromium alloy. It should be understood, however, that other materials may be employed that provide the requisite biasing force and tolerance to environmental conditions while remaining within the scope of the present disclosure.

An amortisseur60is disposed on the slot spring50, which generally dissipates eddy currents from the rotor body22and wedges30. Similar to other components, the amortisseur60defines a plurality of apertures62that are in alignment with the internal gas passageways of the copper windings32. The amortisseur60in one form is an Aluminum material but may also be other materials which function to dissipate the eddy currents. In one form, only one amortisseur60is employed, however, it should be understood that any number of amortisseur segments, disposed end-to-end along the length of the rotor body22, may be employed while remaining within the scope of the present disclosure.

In order to reduce the occurrence of spring migration as set forth above, a plurality of hollow locking members70are disposed within apertures of the creepage40, the slot spring50, and the amortisseur60. The hollow locking members70provide for the continuous flow of cooling gas through the internal components of the rotor body22, as shown by arrow A, while providing an additional securing mechanism to reduce spring migration. More specifically, each locking member70includes a central passageway72to accommodate the flow of gas and an upper flange74that abuts the slot spring50as shown. Similar to the creepage40, the locking members70define a chamfered inner bore76as shown in order to facilitate the flow of cooling gases.

The locking members70in one form are a woven glass material. In one form, two (2) hollow locking members70are adjacent each other in successive apertures along the creepage40, the slot spring50, and the amortisseur60, and there are two (2) hollow locking members70per slot spring50. It should be understood, however, that any number of hollow locking members70may be employed while remaining within the scope of the present disclosure. Additionally, the apertures of the creepage42, the slot spring52, and the amortisseur60through which the hollow locking members70are disposed are larger than adjacent apertures that do not include the hollow locking members70.

As further shown, a slot wedge80is disposed on the slot spring50and the hollow locking members70. The slot wedge80defines a dovetail shape (best shown inFIG. 5), and as such, functions to mechanically lock the components (e.g., copper windings30, creepage40, slot spring50, amortisseur60) within the rotor slot24. Similar to the other components, the slot wedge80defines a plurality of apertures82that are in alignment with the internal gas passageways of the copper windings32. The slot wedge80in various forms may be stainless steel or aluminum.

FIGS. 6A-Cand7A-C illustrate the assembly20in the running/operating position (6A-6C) and in the turning gear position (7A-7C).

Referring now toFIGS. 8A and 8Bat least one field retaining ring90is disposed against one of the end portions of the rotor body22and against the slot wedge80to secure the components along the axial direction of the rotor.