DE102012021114B4 - Electric generator for power generation in power plants - Google Patents

Abstract

Method for refurbishing conductors (5) for a rotor (2) of a gas-cooled electric generator for power generation in power stations, wherein a rotor (2) has a shaft (1) on which a field winding (3) is arranged, the field winding (3) consist of several turns (4) and the turns (4) each consist of a plurality of conductors (5) and wherein the turns (4) each consist of two C-shaped half-turns (4 '), which at its two corresponding electrically and mechanically interconnected free ends, comprising the steps of providing the conductors (5) as flat solid profiles, bending the solid profiles in C-shape, the conductors (5) of the turns (4) having an axial conductor portion and a circumferential direction of the rotor (2) guided arcuate tangential section, - in the axial conductor sections of the conductors (5) of the windings (4) boring of slot-shaped cooling channels (7) extending radially to the longitudinal axis de s rotor (2) extend, - in the arcuate tangential sections of the conductors (5) in the circumferential direction of the rotor (2) on the radially outwardly facing flat side of the conductors (5) milling open channels in a U-shape, wherein the channels with interposition of the insulator (9) define closed cooling channels (8) in the tangential section, and - stacking the conductors (5) with their flat side interposing a laminar insulator (9) in a direction radial to a longitudinal axis of the rotor (2), each flat side extending extends in the longitudinal direction of the generator.

Description

The invention relates to a method for refurbishing conductors for a rotor of a gas-cooled electric generator.

Electric generators for power generation in power plants have a rotor. This rotor initially has a shaft. On this shaft, the two poles of the rotor are arranged. These each have a winding of several coils, each coil in turn consists of several turns. These windings are formed by electrical conductors made of copper, which are embedded in grooves. The conductors between the two winding heads extend parallel to the shaft. In addition to these axial conductors, there are still the circular arc-shaped, tangential conductor, in which the axis of the shaft defines the center of the circle.

During operation of the generator, an electric current flows through the conductors. These electrical currents are comparatively high and cause a correspondingly high heating. This reduces the life and the mileage. For this reason, the conductors in the rotor are cooled. From the DE 11 45 266 A a turbogenerator is known whose conductors are cooled directly in the rotor winding with liquid. The ladder are to consistently tubular or have in their interior tubular cooling channels.

Specifically, the excitation winding of generator rotors is cooled with air or hydrogen to dissipate the heat generated by the excitation current loss heat and to avoid overheating of the insulation components. From the publication of H. Sequence "Production of Windings of Electrical Machines" (ISBN 3-211-81068-4, 1973) various cooling principles and designs for conductors are known. There are 3 important cooling principles, which are usually used (the following sequence corresponds to the increasing effectiveness of the cooling and thus the achievable power densities of the generator):
Variant 1 is an indirect cooling by passing the cooling gas past the narrow sides of the conductors of the winding.

Variant 2 is direct cooling with flow of the cooling gas across the conductor through corresponding radial bores.

Variant 3 is also a direct cooling with flow of the cooling gas along the conductor.

For variants 1 and 2, full copper profiles are used for the conductors of the windings. For variant 2, the conductors are additionally provided with radial bores for flowing through the cooling gas. For variant 3 mostly single or double hollow profiles are used.

From the prior art further examples of the mentioned variants are known: So shows US Pat. No. 3,098,941 Example of variant 1, a rotor winding for an air-cooled generator. The conductors are interleaved in the axial direction and spaced apart in the winding head area with spacers, so that air can pass through the distances between the conductors.

From the WO 97/39513 A1 is known a rotor winding for an electric machine, the variant 3 realized, wherein in the axial region of the conductor are radially extending channels. In the tangential area, tubular cooling channels are continuously introduced into the conductor pieces.

Preferably, rotor windings are cooled either according to variant 1 or according to variant 2 or according to a combination of variants 1 and 2. Alternatively, the rotor winding is cooled according to variant 3. This allows the use of only one profile type (solid or waveguide) and thus a minimum number of solder joints in the winding, since no different profile types must be connected together. A minimal number of solder joints is advantageous because solder joints are a mechanical weak point.

However, there are also generator rotors in which the straight, axial part of the conductor of a winding is designed as a solid profile and is mainly cooled according to variant 1 or according to variant 2 or according to a combination of these variants. The curved, tangential part of the conductor, however, is designed as a waveguide, using a cooling according to the variant 3. The two profile types can also have different widths. However, this concept requires a total of 4 solder joints per turn, namely 2 on the drive and non-drive side of the rotor to connect each 2 hollow and solid sections together to form a turn. Due to their geometric position at the transition between axial and tangential conductors, these solder joints are exposed to very high mechanical and thermally induced forces and therefore form a particular weak point.

On this basis, the invention has for its object to provide a method for refurbishing conductors for the rotor of a gas-cooled electric generator for power generation in power plants, wherein the cooling capacity is improved in the ladders.

The technical solution is characterized by the features of claim 1.

A method for refurbishing conductors for the rotor of a gas-cooled electric generator for power generation in power plants provides:
A rotor has a shaft on which an excitation winding is arranged, wherein the excitation winding consist of several turns and the windings each consist of a plurality of conductors. The turns each consist of two C-shaped half-turns, which are electrically and mechanically connected to each other at its two corresponding free ends. In a first step, the ladders are provided as flat solid sections. This is followed by bending of the solid profiles in C-shape, wherein the conductors of the turns have an axial conductor section and a circular arc-shaped tangential section guided in the circumferential direction of the rotor.

Slot-shaped cooling channels are drilled in the axial conductor sections of the conductors of the turns, which extend radially to the longitudinal axis of the rotor. In the arcuate tangential sections of the conductors open channels are milled in the U-shape in the circumferential direction of the rotor at the radially outwardly facing flat side of the conductor, the channels define closed cooling channels in tangential section with the interposition of the insulator.

Furthermore, a stacking of the conductors with their flat side takes place with the interposition of a planar insulator in a direction radial to a longitudinal axis of the rotor, wherein each flat side extends in the longitudinal direction of the generator.

Thus, it is possible to rehabilitate existing electric generators for power generation in power plants, namely their conductors by replacing the old, previously described conductors with new conductors or windings.

This creates an electric generator for power generation in power plants, in which the conductors of the windings have only 2 solder joints. The cooling capacity of the cooling gas is in no way limited. The basic idea is that the turns or conductors consist of 2 half-turns or 2 half-conductors, which are connected to each other both mechanically and electrically. The generator thus has a generator rotor winding, which can be cooled in accordance with the above-described variants 1 and / or 2 in combination with variant 3. It will be used two different conductor profiles per turn, but which can be made from only one conductor profile type. By the windings are formed as half-turns, as stated, the number of solder joints per turn can be reduced to two solder joints. These two solder joints can be placed in a position with low load.

Preferably, the ends of the two half-turns or the two half-conductors are soldered together. This method of mechanical and electrical connection has proven itself.

It is proposed that the two half-turns are C-shaped. The interface with their solder joints lies between the two C-shaped half-turns in the longitudinal center plane of the rotor, d. H. on the apex of the circular tangential ladder.

The conductors of the windings have transversely extending cooling channels. This concerns the axial conductors in which the cooling channels extend in bores with respect to the radial direction as bores. This passage of the cooling gas across the conductor in these axial conductor sections provides optimum cooling performance. In addition, the holes for flowing through the cooling gas are easy to introduce into the ladder.

Further, for a direct cooling, a flow of the cooling gas along the conductor is proposed. These cooling channels are intended for the circular arc tangential conductor.

A preferred structural solution can be that it is assumed that a solid profile for the conductor. In this solid profile initially open channels are milled, for example in U-shape. In this case, one or more of these channels can be provided. These channels are closed by applying a so-called intermediate insulation on the conductors upwards, so that thereby a cooling gas flow is realized longitudinally through the conductor. This is similar to the previous waveguide. As a result, a running in the longitudinal direction of the conductor cooling channel is created in a technically very simple manner, without having to use a special hollow profile. Because the cooling channels are created by milling out of the flat top of the ladder.

For producing a conductor for the rotor of an electric generator for power generation in power plants can be provided:
The basis is a ladder full profile, which in the initial state has the same cross-sectional profile over the entire length. It is thus assumed that a solid profile with the length of half a turn and with the cross-sectional dimensions of the largest necessary profile cross-section for the head. This is the wider profile of the previously commonly used profile (usually the hollow profile). The solid profile according to the invention is in the range in which a narrower profile is required (the former narrower profile), reduced accordingly by machining in the width. There is thus an adaptation to the desired profile or cross-sectional profile by removing material. At the point where the solder joint between the two different profiles used to form a right angle, the conductor is now transformed by suitable methods into a 90 ° arc. The cooling according to the above-described variant 3 in the region of the tangential conductor is - as stated - realized by milling one or more, open at the top channels along the Volleiters. As a result, overall a tangential conductor is created, more or less in the manner of a waveguide, which starts from a standard conductor full profile.

An embodiment of an electric generator for power generation in power plants will be described below with reference to the drawings. In these shows:

1 a perspective view of the electric generator (but without the end caps);

2 a detail from the end of the generator in 1 but with only a single turn;

3a a side view of a half-conductor of the half-turn;

3b a plan view of the half-conductor of the half-turn in 3a ;

4a a perspective view of the winding consisting of two half-turns before soldering these half-turns;

4b the situation in 4a after soldering the two half-turns together;

5 a schematic sectional view through the winding.

The electric generator for power generation in power plants, as in 1 is shown has a shaft 1 with rotor on it 2 on. This rotor 2 is through a field winding 3 formed, which define the two poles. The excitation winding 3 consists of several turns 4 , these turns 4 each of several electrical conductors 5 consist.

The ladder 5 the turns 4 are as C-shaped half-ladder 5 ' educated ( 3a and 3b ). These two half-conductors 5 ' are to the overall leader 5 joined together and thereby end over a solder joint 6 connected with each other. The interface between the two half-conductors 5 ' of the leader 5 lies on the median longitudinal plane of the shaft 1 , The interface can also be elsewhere. The half-ladder 5 ' in their entirety form the half-turns 4 ' which then turn to the full turn 4 are connected.

The special feature is the training of the ladder 5 or half conductor 5 ' for the turns 4 :
The starting point is the production of the conductors 5 or half conductor 5 ' from a solid profile of copper, in particular with a flat, rectangular cross-section. This solid profile is bent by appropriate mechanical measures to a C-shape, as in the 3a and 3b is shown.

The half-ladder 5 ' have in the straight axial region cooling channels 7 on. These are introduced through slot-like holes in the material.

A second type of cooling channels 8th is in the arcuate tangent of the half-ladder 5 ' intended. The basic principle here is that in the top-side flat side of the half-conductor 5 ' Channels are milled in U-shape, for example. In this case, one or more of these channels can be provided. These milled channels define the cooling channels 8th , Specifically, these are cooling channels 8th Realized that the flat sides of the ladder 5 with intermediate arrangement of a flat insulator 9 be stacked. However, this means that through the intervening insulator 9 the milled channels are closed at the top, so that a cooling gas flow longitudinally through the conductor 5 in the form of a cooling channel 8th is realized.

As stated, is used in the manufacture of the conductor 5 or half-conductor 5 ' assumed a solid profile, which has a same cross section in the initial state over the entire length. In the areas in which this cross section is too large, there is a corresponding removal of material, so that the desired cross section or the desired profile is created.

LIST OF REFERENCE NUMBERS

1

wave

2

rotor

3

excitation winding

4

convolution

4 '

Half-turn

5

ladder

5 '

Semiconductor

6

soldered point

7

cooling channel

8th

cooling channel

9

insulator

Claims (2)

Method for rehabilitating ladders ( 5 ) for a rotor ( 2 ) of a gas-cooled electric generator for power generation in power plants, wherein a rotor ( 2 ) a wave ( 1 ), on which a field winding ( 3 ), wherein the exciter winding ( 3 ) of several turns ( 4 ) and the turns ( 4 ) each of several conductors ( 5 ) and where the turns ( 4 ) each of two C-shaped half-turns ( 4 ' ), which are electrically and mechanically interconnected at their two free ends, comprising the steps of - providing the conductors ( 5 ) as flat solid profiles, - bending the solid profiles in C-shape, whereby the conductors ( 5 ) of turns ( 4 ) an axial conductor portion and a circumferential direction of the rotor ( 2 ) guided circular arc tangential section, - in the axial conductor sections of the ladder ( 5 ) of turns ( 4 ) Drilling of slot-shaped cooling channels ( 7 ) extending radially to the longitudinal axis of the rotor ( 2 ), - into the arcuate tangential sections of the conductors ( 5 ) in the circumferential direction of the rotor ( 2 ) on the radially outwardly facing flat side of the conductors ( 5 ) Milling of open channels in U-shape, the channels with the interposition of the insulator ( 9 ) closed cooling channels ( 8th ) in the tangential section, and - stacking the ladder ( 5 ) with its flat side with intermediate arrangement of a flat insulator ( 9 ) in a direction radial to a longitudinal axis of the rotor ( 2 ), each flat side extending in the longitudinal direction of the generator. Method according to claim 1, characterized in that the ends of the two half turns ( 4 ' ) are soldered together.

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