Portable device and method for restoring the circularity of a generator conductor

Abstract

The present invention relates to a portable device and method for restoring the cylindricity of a generator conductor. In particular, a method for restoring the cylindricity of a generator conductor, in particular a turbine generator conductor, wherein the conductor is a cylindrical conductor coupled to a first stator bar joint of a generator; the method comprising the steps of: a) providing a portable device provided with a turning tool; b) releasing the coupling between the first stator bar joint and the conductor; c) coupling the portable turning device to the conductor, wherein the conductor is still coupled to the generator; d) turning the conductor.

Description

[0001] Cross-references to related applications

[0002] This patent application claims priority to European Patent Application No. 19425056.9, filed on July 23, 2019, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to the technical field of generators (i.e., devices configured to convert introduced mechanical energy into electrical energy). Specifically, this invention relates to the field of generator maintenance, i.e., periodic inspection activities performed to verify the integrity of the components forming the generator, or repair activities performed to restore damaged components to the assembly. More specifically, maintenance activities related to this invention refer to operations performed to restore generator connections in the event of damage to the generator connection itself. For the term "generator connection," we consider it to refer to the connection (or coupling) between the stator bar end and a conductor configured to deliver current / voltage to the outside of the generator. Even though this invention is introduced as a maintenance activity performed to restore a damaged generator connection, the maintenance activities of this invention can also be performed before damage occurs to provide a new connection to the generator. In view of the above preliminary considerations related to the technical field of this invention, the following description will relate to portable devices and methods for restoring the cylindricity of generator conductors to improve / restore generator connections. In the following text, the generator mentioned above will be described as a turbine generator (i.e., a generator with a turbine assembly), because maintenance activities are very important and must be performed frequently in such machines. However, the present invention can also be applied to other types of generators. In other words, the specific embodiments of the present invention described in the field of turbine components do not limit the scope of protection of the present invention itself.

[0004] Description of the prior art

[0005] As is well known, a generator (also called an alternator) is a component configured to convert introduced energy into detached electrical energy. This invention specifically relates to a turbine generator, wherein the introduced energy is in the form of the mechanical energy of a rotating rotor driven by a turbine. It is well known that in the case of a gas turbine, the turbine is driven by an expanding hot gas flow generated in a gas turbine assembly, which includes a compressor unit, a burner unit, and the turbine itself; in the case of a steam turbine, the turbine is driven by expanding high-temperature and high-pressure steam in a turbine assembly, which typically consists of a high-pressure section, a medium-pressure section, and a low-pressure section. In view of the above, the generator includes: a rotating portion, which is in the form of a sleeve integrally formed with the rotating rotor; and a stator portion, which is a fixed structure arranged externally around the rotating portion. The stator portion is also formed as a sleeve, and an air gap exists between the internal rotating rotor portion and the external stator portion of the generator. Therefore, the stator portion is formed as a hollow cylindrical body, wherein the inner cylindrical surface faces the rotating rotor. The rotating portion supports a plurality of magnetic elements to generate a rotating magnetic field. The inner surface of the stator section (i.e., the surface facing the rotating part of the generator) is provided with a plurality of axial grooves (the term "axial" refers to the rotor axis), wherein each groove defines a recess for receiving a stator bar as a portion of the opposing electrical winding. According to Faraday's law, a rotating magnetic field generates an electromotive force in the electrical winding of the stator section. The front portion of the stator section is referred to as the generator end winding and includes a plurality of stator bar ends configured to connect with corresponding conductors to deliver the generated current / voltage. Specifically, the present invention relates to a generator connection in which each conductor is implemented in the form of a cylindrical body made of a conductor material (such as copper). Given this shape of the conductor, each stator bar end is currently provided with a connector (also made of conductor material) comprising a base connected to the stator bar end and a generally recessed head configured to connect with the outer surface of the cylindrical conductor. According to this prior art practice, the connection between the connector and the cylindrical conductor is performed according to the following steps. Initially, the cylindrical conductor is pressed against the recessed head of the connector, and then the connector is hard soldered to the conductor.

[0006] This existing technology of connection has some drawbacks. Specifically, it is prone to mechanical failure due to the fragility of the connector layout (or design).

[0007] To avoid this problem, the applicant has developed an alternative connector in which there is no space for mechanical stress that could cause damage. Specifically, this alternative connector includes a base in the form of two plates configured to connect to the ends of stator bars and a head in the form of a cylindrical seat configured to accommodate the ends of a cylindrical conductor. Thus, at the connection point, the cylindrical conductor is completely covered by the cylindrical seat.

[0008] To replace an old connector with a new one (in the event of damage or simply as part of an improvement maintenance activity), it is necessary to remove or release the existing connection and make a new connection using the alternative connector described above. Due to the cylindrical / prismatic connection between the alternative connector and the conductor, the outer surface of the conductor (at least the portion to be connected to the connector) must be machined to suit this connection. Specifically, due to the connection steps described above and performed for connecting the conductor to the recessed head of the old connector, there may be brazing material to be removed from the outer surface of the conductor (caused by the brazing steps). Furthermore, some portions of the outer surface of the conductor may be exposed with localized deformation (attributed to the steps of clamping the conductor to shape it so that it abuts against the recessed head of the old connector around the end winding at the phase break to reach the connector position). To restore the cylindricity of the conductor, it is necessary to remove some material from the outer surface of the conductor using a turning device.

[0009] According to existing technical practice, the simplest and most straightforward solution for those skilled in the art is to completely remove the conductor from the generator in order to prepare (turn) the conductor for the new connector, so that the conductor can be moved away from the generator to a machining station where the outer conductor surface can be machined using ordinary turning tools. However, standard turning equipment is too large to be used on generators. This solution is so expensive in terms of cost / time that it is generally preferred nowadays to replace the old conductor with a new one rather than to restore the old one.

[0010] The disclosure of this invention

[0011] Therefore, a primary object of the present invention is to provide a portable device configured for use in the field (“in situ”) and for preparing existing cylindrical conductors of generators (especially turbine generators) for coupling to a connector having a cylindrical base. By using the term “portable,” we mean a device that can be used between generator components without removing the conductor, i.e., a device with the smallest possible size. Specifically, the present invention relates to a portable turning apparatus configured for turning the outer surface of a cylindrical conductor to restore surface cylindricity due to pre-existing local deformation and for preparing the conductor for reception (and brazing) in a cylindrical connector base.

[0012] In addition to the main scope of the present invention described above, there are some additional specific problems that the present invention solves, namely:

[0013] - Very narrow processing space;

[0014] - The parts to be restored (machined) are attached to the generator and cannot be easily removed and installed unless an expensive and time-consuming disassembly is planned;

[0015] The recovery process requires some kind of power (pneumatic / electric / hydraulic) that cannot be transmitted by hand alone.

[0016] Before discussing the detailed mechanical description of the portable turning apparatus, the present invention can also be defined as an alternative method for restoring the cylindricity of generator conductors. In fact, prior art practice does not recommend performing such machining steps on-site and inside the generator to prepare the conductors to be housed and brazed in the cylindrical connector seat.

[0017] Therefore, the present invention also provides a method for restoring the cylindricity of a conductor in a generator, particularly a turbine generator, wherein the conductor is a cylindrical conductor connected to a first stator bar joint of the generator. This method includes the following steps:

[0018] a) Provide a portable turning device (as will be described below);

[0019] b) Release the connection between the first stator bar connector and the conductor; typically, the first stator bar connector includes a recessed conductor receiving seat, and the existing connection is achieved by brazing the connection when the conductor is slightly pressed against the seat;

[0020] c) Connecting a portable turning device to a conductor, wherein the portable turning device has a very small size so that the conductor can still be connected to a generator;

[0021] d) The conductor (i.e., the end portion of the conductor) is turned by starting the portable turning device.

[0022] Preferably, step b) is performed by induction heating.

[0023] Since the scope of this method is to place the conductor in a state suitable for containment and brazing in a new connector cylindrical base (smooth and cylindrical end outer surface), the method also includes the following steps:

[0024] e) Replace the first or existing stator bar connector with a second or new stator bar connector having a cylindrical seat configured to accommodate a machined portion of the conductor (i.e., having a suitable inner diameter).

[0025] f) Connect the machined conductor to the cylindrical seat of the second stator bar connector.

[0026] According to the invention, the conductor is fixed while the conductor is still connected to the generator (i.e., the downstream portion of the generator), and the portable turning device provides a turning tool that rotates and travels. Therefore, during step d), the conductor is fixed while the turning tool rotates around the conductor and travels along the conductor.

[0027] Therefore, the present invention relates to a reliable and efficient method for turning the cylindrical connector of a generator using a convenient (portable and stator-operable) rotary system. Note that in conventional turning processes, the part to be turned rotates while the tool is stationary. In contrast, in the present invention, the part to be machined is stationary, while the turning tool rotates around and travels along the cylindrical conductor.

[0028] As cited above, the applicant has developed a novel portable device suitable for carrying out the method of the present invention, namely, a device configured for turning conductors when they are fixed to a generator and configured for use on a stator. Therefore, the portable device according to the main definition of the present invention includes:

[0029] - A support element configured to connect the device to the end of a conductor;

[0030] - A turning tool (supported by a support) configured to rotate (and turn) around the end of the conductor while the conductor is fixed and supported by the support.

[0031] Preferably, the device includes a motor for at least driving the rotation of the turning tool. For example, an adjustable pneumatic motor.

[0032] Preferably, the turning tool is also configured to travel along the conductor. This travel motion can be motorized or performed by, for example, a drive screw.

[0033] Preferably, the device includes a first gearbox supporting a motor and a second gearbox supporting a turning tool, wherein the first gearbox is movable relative to the second gearbox. For example, the gearboxes may be connected by two flanges to allow angular adjustment of the first gearbox relative to the second gearbox fixed to a conductor.

[0034] Preferably, the connection between the first gearbox and the second gearbox can be a flexible connection configured to allow the first gearbox to move away from the second gearbox.

[0035] Preferably, the device includes a bowl-shaped structure that supports the turning tool and is configured to receive the end of the conductor to be turned. Preferably, such a bowl-shaped structure includes at least a window for discharging burrs of material removed from the conductor.

[0036] Preferably, the turning tool is adjustable (e.g., stepwise) relative to the conductor in the radial direction so as to gradually remove material from the conductor.

[0037] Preferably, the turning tool is removable to allow for the placement of new or different turning tools.

[0038] It should be understood that both the foregoing general description and the following detailed description are exemplary and intended to provide further explanation of the claimed invention. Other advantages and features of the invention will become apparent from the following description, drawings, and claims.

[0039] The features of the invention, which are considered novel, are set forth in detail in the appended claims. Attached Figure Description

[0040] Further beneficial effects and advantages of the present invention will become apparent after careful reading of the detailed description with appropriate reference to the accompanying drawings.

[0041] However, the invention itself can be best understood by referring to the following detailed description of the invention, which describes exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein:

[0042] - Figure 1 A schematic view of a gas turbine assembly used in power equipment;

[0043] - Figure 2 A schematic view of the stator section of the generator;

[0044] - Figure 3 for Figure 2 A schematic enlarged view of the section marked III shows the existing generator connections;

[0045] - Figure 4 This is a schematic view of an alternative generator connection, in which the existing conductors must be machined prior to connection;

[0046] - Figure 5 This is a schematic view of an embodiment of a portable turning device according to the present invention, which is suitable for turning conductors fixed to a generator;

[0047] - Figure 6 For connection with generator conductors Figure 5 A schematic view of a portable turning device. Detailed Implementation

[0048] The technical content and specific implementation of the present invention are described below with reference to the accompanying drawings and preferred embodiments, but are not intended to limit the scope of the invention. Any equivalent variations and modifications made according to the appended claims are covered by the claims asserted by the present invention.

[0049] The invention will now be described in detail with reference to the accompanying drawings.

[0050] See Figure 1 This is a schematic view of a gas turbine assembly for use in power equipment (hereinafter, only a gas turbine). In fact, the field of gas turbine generators is a non-limiting example of possible applications of the invention. Figure 1 A gas turbine 1 is disclosed, having a rotor 6 defining a shaft 2 and comprising, in series along the main flow M:

[0051] -Compressor Unit 3;

[0052] - Combustor unit 4, in which compressed air is mixed with at least fuel, and such mixture is burned to produce a hot gas stream;

[0053] - Turbine unit 5, in which hot air expands, thereby rotating and doing work on rotor 6.

[0054] according to Figure 1 Downstream of turbine 5, rotor 6 performs work to drive the rotating part of generator 7.

[0055] Now see Figure 2 This is a schematic view of the stator portion 8 of the generator 7 mentioned earlier. Specifically, Figure 2 A stator portion 8, which has a hollow cylindrical structure along axis 2, is disclosed. This stator portion is suitable for housing the rotating portion (in... Figure 2 (Not shown in the image). As described above, the rotor can be... Figure 1 The generator has a gas turbine rotor 6, and therefore the generator shaft can be aligned or misaligned relative to the gas turbine shaft. The stator portion 8 of the generator 7 includes an inner surface 9 facing the rotating portion, and an air gap is provided between the rotating portion and this inner surface 9. Figure 2 As disclosed, the inner surface 9 is provided with a plurality of axial grooves or slots 10, which are parallel to the axis 2 and circumferentially spaced from each other. Each groove 10 accommodates a stator bar defining an electrical winding. As is known (and according to Faraday's law), the rotating magnetic field generated by the rotating part produces an electromotive force (i.e., electrical energy) in the electrical winding of the stator part. In order to utilize this electrical energy, the front part of the stator part (also known as the generator end winding and...) Figure 2 (Ref. 11) includes multiple stator bar ends, which are connected by connectors to corresponding conductors that are sequentially fixed to the downstream portion of the generator.

[0056] Now see Figure 3 , its purpose is Figure 2 A schematic enlarged view of the generator end winding portion, marked with reference numeral III. Specifically, Figure 3 Existing connections in the generator prior to the start-up of this invention are disclosed. According to... Figure 3 In one example, the stator bar end 12 is connected to a first connector 13 (also made of conductor material), which includes a base connected to the stator bar end 12 and a generally recessed head configured to engage with the outer surface of a cylindrical conductor 14. As described in the Prior Art section, the connection between this connector 13 and the cylindrical conductor 14 is performed according to the following steps: Initially, the cylindrical conductor 14 is pressed slightly against the recessed head of the connector 13, and then the connector 13 is hard-braced to the conductor 14. This prior art connection has several disadvantages. Specifically, this connection is prone to mechanical failure due to the fragility of the connector layout. To avoid this problem, the applicant has developed an alternative connector in which there is no space for mechanical stresses that could cause damage.

[0057] Now see Figure 4 The invention discloses an alternative connector for connecting the ends of stator bars to conductors. Specifically, this alternative connector 15 includes: a base in the form of two plates 16 configured to engage with the ends 12 of the stator bars; and a head 17 including a cylindrical seat 18 configured to receive the ends of cylindrical conductors 14. (See also...) Figure 4 As disclosed, at the connection point, the cylindrical conductor 14 is completely surrounded by the cylindrical base 18 to obtain a pocket connector. This is for use with... Figure 4 The new connector 15 replaces the old connector 13. Figure 3 (In the event of damage to the existing connector 13 or simply as part of an improvement maintenance activity), it is necessary to remove or release the existing connection and make a new connection using the alternative connector 15 described above. Due to the cylindrical / prismatic connection between the alternative connector 15 and the conductor 14, the outer surface of the conductor 14 (at least the portion to be connected to the connector 15) must be machined to accommodate the connection. Due to the connection steps described above and performed for connecting the conductor 14 to the existing recessed head of the old connector 13, the outer surface of the conductor 14 exhibits some localized deformation (attributed to the clamping steps that shape the conductor to abut against the recessed head of the old connector around the end windings of the generator to the connector position). To restore the cylindricity of the conductor and remove some material from the outer surface of the conductor 14, the applicant has developed a new portable turning device configured for use on the generator end windings after the conductor has been released from the old connector 13 but is still secured to the downstream portion of the generator.

[0058] Now see Figure 5 This is an embodiment of the portable turning device of the present invention (conductor 14 is also included). Figure 5 (As shown in the image). This portable turning apparatus 19 includes a pneumatic motor 20, which is attached to a first gearbox 21 via a male-female shaft coupling 22. Gearbox 21 houses means for transmitting rotary motion to a splined shaft 23 supported by a second gearbox 24. Gearboxes 21 and 24 are connected by a flange 25, allowing the first gearbox 21 to rotate relative to the second gearbox 24. The splined shaft 23 is connected to an output shaft 26 supported by a bushing. The bushing carries a bowl-shaped vessel 27, which is supported on a turning tool (not shown) machined on the outer surface of a conductor 14. A feed screw 28 causes the bowl-shaped vessel 27 to travel from position 0 (when the distance between the bowl-shaped vessel 27 and the gearbox 24 is 0) and position 1 (when the bowl-shaped vessel 27 has traveled (e.g., 40 mm)). Furthermore, the disclosed device 19 includes a support frame 29, which is connected at one end to the second gearbox 24 and supports the conductor 14 at the opposite end to align the conductor axis with the axis of the bowl-shaped object. In another embodiment of the invention (not shown), to match the geometry in the end windings and accommodate spatial constraints, i.e., the layout of the transmission consisting of the pneumatic motor 20 and gearboxes 21 / 24, the pneumatic motor can be attached to the first gearbox 21 or directly to the second gearbox 24 via a flexible shaft for torque transmission.

[0059] at last, Figure 6 It was made public how to make Figure 5 The apparatus 19 is used to perform the method of the present invention. For example, in Figure 6 As disclosed, the device 19 has dimensions suitable for use on a stator without removing the conductor. In this figure, the first gearbox has been rotated due to the presence of the conductor 14 (connected to the new connector 15).

[0060] Although the invention has been explained with respect to its preferred embodiments (multiple) as mentioned above, it should be understood that many other possible modifications and variations can be made without departing from the scope of the invention. Therefore, it is contemplated that one or more of the appended claims will cover such modifications and variations that fall within the true scope of the invention.

Claims

1. A method for restoring the cylindricity of a generator conductor (14), wherein, The conductor (14) is a cylindrical conductor connected to the first stator bar connector (13) of the generator (7); the method includes the following steps: a) Provide a portable device (19) which is equipped with turning tools; b) Release the connection between the first stator bar connector (13) and the conductor (14); c) Connect the portable device (19) to the conductor (14), wherein the conductor is still connected to the generator (7); d) Turn the conductor (14).

2. The method according to claim 1, characterized in that, The existing connection between the conductor (14) and the first stator bar connector (13) is achieved by brazing; step b) is performed by induction heating.

3. The method according to claim 1 or 2, characterized in that, The method further includes the following steps: e) Replace the first stator bar connector (13) with a second stator bar connector (15), the second stator bar connector having a cylindrical seat (18) configured to connect with a machined portion of the conductor (14); f) Connect the machined conductor (14) to the cylindrical seat (18) of the second stator bar connector (15).

4. The method according to claim 3, characterized in that, The connection between the machined conductor and the second stator bar connector is achieved by brazing.

5. The method according to claim 1, characterized in that, The portable device (19) is provided with a rotary turning tool; during step d), the conductor (14) is fixed and the turning tool rotates around the conductor (14).

6. The method according to claim 1, characterized in that, The portable device (19) is provided with a traveling turning tool; during step d), the conductor (14) is fixed and the turning tool travels along the conductor (14).

7. A portable device (19) for restoring the cylindricity of a generator conductor (14), the device (19) having dimensions suitable for use on a generator (7) and comprising: - Support member (29), the support member being configured to connect the device (19) to the end of the conductor (14); - A turning tool configured to rotate about the end of the conductor (14) while the conductor is fixed; The device includes an adjustable pneumatic motor (20) for driving the turning tool, a first gearbox (21) supporting the motor (20) and a second gearbox (24) supporting the turning tool; the first gearbox (21) is movable relative to the second gearbox (24).

8. The apparatus according to claim 7, characterized in that, The turning tool is configured to travel along the end of the conductor (14).

9. The apparatus according to claim 7, characterized in that, The device includes a flexible connection between the first gearbox (21) and the second gearbox (24), the flexible connection being configured to move the first gearbox (21) away from the second gearbox (24).

10. The apparatus according to claim 7, characterized in that, The device includes a bowl (27) that supports the turning tool and receives the end of the conductor; the bowl (27) includes at least a window for discharging material removed from the conductor.

11. The apparatus according to claim 7, characterized in that, The turning tool is capable of moving radially relative to the conductor (14).

12. The apparatus according to claim 11, characterized in that, The turning tool is capable of moving gradually in the radial direction relative to the conductor (14).

13. The apparatus according to any one of claims 7 to 12, characterized in that, The turning tool is removable.

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