EP1062719A1

EP1062719A1 - Ventilation system for the excitation winding of large salient-pole machines

Info

Publication number: EP1062719A1
Application number: EP99916787A
Authority: EP
Inventors: Heinz-Dieter Eberhardt
Original assignee: Siemens AG
Current assignee: Voith Hydro Holding GmbH and Co KG
Priority date: 1998-03-12
Filing date: 1999-03-12
Publication date: 2000-12-27
Also published as: WO1999046846A1; CA2322422A1; DE19810628A1; BR9909244A; JP2002507109A

Abstract

According to the invention, to improve the cooling of the excitation windings of a large salient-pole machine, especially for hydraulic energy, flow paths (2) are integrated into the winding layers (4) of the excitation windings (21) which in addition to the pole gaps (1) feed coolant radially to the outside.

Description

description

Ventilation system for the excitation winding of large salient pole machines

The invention relates to a ventilation system for a star-shaped excitation system of a salient pole machine, wherein a gaseous cooling medium forces the cooling of the excitation winding. Such salient pole machines are generally used as generators, in particular hydropower generators.

The principle of a salient pole machine is shown in FIG. 6: on the cylindrical inner surface of a stator part 30 there is a winding 31, e.g. Coils inserted in grooves are arranged around the excitation system rotating about the rotor axis 32. This excitation system consists of legs extending in a star shape from the rotor axis 32, which are magnetized in the radial direction and have an alternating polarity. In the illustrated case, four pairs of such magnetic poles are provided, that is to say eight legs which are separated from one another in the tangential direction by pole gaps 1, which thus each widen in pie-pie form to form a winding head space 33 and are connected to one another via these winding head spaces. Each leg is magnetized in each case by an excitation winding 21 running around a pole shaft 20, as a rule flat copper conductors or similar conduction bands, which form individual winding layers, each separated by insulating layers. To guide the magnetic field generated, the pole shafts each carry a pole piece 10, which is arranged in the winding head space 33 at the head of the excitation winding. The other end of each pole shaft 20 merges into a rotor yoke 12.

Large salient pole machines, as are required, for example, in the megawatt range, allow the rotor axis 32 to be designed as a hollow axis in order to introduce a cooling medium into the pole gaps via the cavity 34, which then 2 can be discharged from the winding head spaces via corresponding outlets in the stator part.

The losses occurring in the field windings must be dissipated to limit the temperature and require intensive cooling of the field system. The cooling is carried out by means of a cooling gas stream which is passed through the cylindrical interior of the stand part, for which two variants are common:

First: The rotor's own rotation acts as a pressure source for the ventilation system without additional fans. The prior art is represented by DE-OS 195 15 260.

The gaseous cooling medium emerges from slots in the barrel yoke and flows radially into the pole gap. The heat flow from the flat copper conductors (winding layers) to the pole shaft is low due to the large heat resistance due to the electrical insulation between the field winding and the pole shaft. The main part of the heat flow is therefore released on the side of the excitation winding facing away from the pole shaft to the cooling air in the pole gap and in the winding head space.

The effective speed for cooling in the winding head space on the end faces of the field winding is much higher than in the pole gap. This means that the cooling here is also more intensive and the conductor temperature is therefore lower.

To enlarge the cooling surface, there are cooling fins on the flat copper conductors on the side facing away from the pole shaft. These run axially in the pole gap and in the circumferential direction in the end region. Since the cooling fins, which are axially arranged in the pole gap, are perpendicular to the radial direction of the coolant flow, there is a transverse flow against the fins. The heat transfer of such fin arrangements is 3 not very intense. This is a major disadvantage of this ventilation system in terms of cooling the field winding.

Secondly, two fans, which are axially offset from the poles, are used as the pressure source and force the cooling medium to flow axially into the pole gap. The excitation winding is cooled here by this axial flow of the cooling medium, which then flows radially into the stator cooling channels. To intensify the cooling of the field winding, measures for back ventilation between the field winding and the pole shaft can be provided. This results in additional heat dissipation from the area between the field winding and the pole shaft. The prior art of such measures for rear ventilation can be seen from EP 0 415 057 AI. The disadvantage of this cooling solution is the high level of construction and technology involved.

In large full-pole machines that are used as turbogenerators, the field winding is housed in slots. To ensure intensive cooling, there are radial slots in the middle of the conductor within the slot area. The gaseous cooling medium flows through the slots and cools the excitation windings. Such an arrangement of the conductors for full-pole machines is the subject of WO 92/20140. This cooling solution is not suitable for salient pole machines.

The object of the invention is to create a highly effective cooling technology solution for the field development of large salient pole machines, in which the cooling surface is enlarged and high heat transfer coefficients are achieved by simple design measures.

According to the invention, the object is achieved in that openings are provided in the winding layers which form flow paths in which the cooling medium is also radially outward. 4 leads, as in the pole gaps, but which lead along the side of the excitation winding facing away from the pole shaft through the interior of the windings. These flow paths open directly into the winding head space or into the part of the pole gap that merges into the winding head space. These window-like openings in the winding layers of the excitation winding significantly increase the cooling surface, especially in the area of the head.

Due to the cross-sections of the openings, which can have any contours, the cooling air flows almost radially with almost the same flow speed as in the pole gap.

The flow paths can be straight, but they can also have bends. The cooling medium is led radially outwards, as in the pole gaps, so it is a "parallel connection of additional cooling medium flows". These "parallel" flow paths result from the fact that the window-like openings made in the winding layers (eg flat copper conductors) are not covered by the insulating layers arranged between the winding layers, and the openings worked into the winding layers lie one above the other, although the insulating material is slightly in the window-like openings can protrude. In order to avoid flashovers between the winding layers ("short turns"), the edges of these window-like openings must not have any burrs.

As a rule, the flow paths start from inlet openings which are formed by corresponding windows in the lowest winding position of the excitation winding, the edges of these inlet openings advantageously being rounded off or beveled.

The flow is not obstructed by detailed design solutions when exiting the head or the uppermost winding layers and the pole piece. 5 These and further advantageous embodiments of the invention are specified in the subclaims.

The cooling of the field winding is significantly intensified by the solution according to the invention. The possible development reserve can vary, e.g. to lower the temperature of the excitation winding or to increase the electromagnetic utilization. The field winding of large salient pole machines can be realized in a material and space-saving manner. This also opens up ways of improving efficiency, in particular by reducing ventilation losses due to the intensification of cooling.

The advantage of the invention can also be seen in the fact that it can be used both for new designs and for retrofitting existing machines.

The invention including advantageous embodiments will be described below with reference to the figures. Show it:

1 shows a schematic cross section of a sector A in FIG. 14, FIG. 2 shows a plan view of the outer edge region of a winding layer and the window-like openings for forming the flow paths, FIG. 3 shows a schematic section through several winding layers with insulating layers lying between them and continuous flow paths,

4 shows a section through winding layers with cooling surfaces on the outer edges, FIG. 5 shows a section like FIG. 3 with an outer edge region of lower height of the winding layers, FIG. 6 shows a section as in FIG. 1 with a displacement body in the pole gap, 6 shows a section as in FIG. 1 with a guide device in the pole gap, FIG. 8 shows a section as in FIG. 6 with a hollow displacement body, FIG. 9 shows a section through a winding head,

10 shows a section through a base of an excitation winding, FIG. 11 shows a section like FIG. 3 with lateral openings on the flow paths, FIG. 12 shows a section like FIG. 4 with winding layers, the openings of which differ in an alternating sequence

13 have a section as in FIG. 6 with a displacement body supported on adjacent excitation windings, FIG. 14 shows a section as in FIG. 6 with a displacement body overlapped by the pole piece, FIG. 15 shows the top view of a leg with a pole piece and the excitation winding underneath, FIG 16 the diagram of a salient pole machine already described.

Components with the same function have the same reference symbols.

FIG. 1 shows the guidance of the cooling medium in the area of the pole gap 1 and through the “parallel” flow paths 2 in the area of the head 3 of one or more flat copper conductors 4, which form the winding layers of the excitation winding 21. The winding layers are each insulated from one another by an insulating layer 5. In the space 13 between the rotor yoke 12 and the excitation winding 21, the arrangement (already without additional guide devices) forces the flow to be divided once through the pole gap 1 and secondly through the parallel flow paths 2 in the outer edge region 3 of the flat copper conductor 4. 7 In the space 13 between the excitation winding 21 and the yoke 12, additional guide devices for dividing and guiding the flow of the cooling medium can be arranged.

Figure 2 shows an embodiment for rectangular openings 14 in the outer edge regions 3 of the flat copper conductor 4 and the insulating layers 5. The view of a winding head according to Figure 15 shows that the flow paths with the openings 14 also have a circular or any other cross section and can open into the winding head space in the radial direction on a part 35 of the winding head which projects beyond the pole shoe 10. The flow paths preferably lead in an approximately radial direction along those outer surfaces 36 of the excitation winding that face away from the pole shaft and point toward pole gap 1, that is to say the surface pieces 36 that lie between two legs, while between the pole shoe and the outer surfaces 37 that limit the field winding in the axial direction, no flow paths and openings need to be provided.

With flat copper conductors 4 lying one above the other, which are separated by insulating layers 5, FIG. 3 shows how the openings 14 in the outer edge regions 3 of the winding layers 4 and insulating layers 5 form the flow paths 2 to the area in the pole gap 1 or to the winding head space. The openings 14 of all flat copper conductors 4 and insulating layers 5 are the same here, the insulating layers 5 reaching as far as the edge of the openings or so slightly beyond that they practically do not impair the flow.

FIG. 4 shows an arrangement corresponding to FIG. 3. In order to improve the heat transfer in the area of pole gap 1 and the winding head space, cooling surfaces 14 are additionally arranged on the outer edges 3 of the flat copper conductors 4, for example external axial or radial or interrupted or interrupted at the foot or turned needle-shaped cooling fins 15. FIG. 5 shows a schematic sectional illustration of a section of the field winding 21 with a reduced height of the winding layers in the outer edge region 3 of the flat copper conductor 4. The insulating layers 5 are only arranged in the region with a non-reduced height. They can also protrude slightly into the area of reduced height. In the area with reduced height there is an open connection (breakthrough) between the pole gap 1 and the flow paths 2 in the edge area. This embodiment has the advantage that the edges of the openings 14 in the flat copper conductor 4 are not deburred and the flow can be exchanged between the area of the pole gap 1 and the parallel flow paths 2.

In the section of FIG. 6, an elongated displacement body 16 can be seen in the pole gap 1 for a salient pole machine, the cooling medium of which is supplied via slots 11 in the rotor yoke 12. The displacement body 16 is aligned in the axial direction (approximately parallel to the rotor axis). It extends over the greater part of the axial length of the

Leg. This makes it possible to increase the coolant speed in the pole gap 1 and the flow paths 2.

FIG. 7 shows the schematic sectional illustration of an exemplary embodiment with additional cooling fins on the outer side edges of the flat copper conductors 4 and guide devices 17 of a salient pole machine, in which the coolant flow likewise emerges from slots 11 in the rotor yoke 12. The guide devices 17 extend in the axial direction over the greater part of the axial length of the legs in the pole gap 1. Each guide device 17 consists of a fastening part 23 and one or more guide vanes 22. The guide vanes 22 protrude obliquely from the fastening body 23 into the radial one Flow (angle of attack α preferably less than 90 °) and are straight or curved in the further course. The expansion of the guide vanes 22 in the direction parallel to the rotor axis preferably corresponds approximately to the expansion 9 expansion of the slots 11 in this axial direction. The number of guide vanes is preferably not greater than the number of slots. For the cooling medium flowing in the radial direction, the pole gap has a flow cross section which is considerably larger than the cross section occupied by the guide devices.

For better flow guidance, the guide vanes 22 can have additional limits in the axial direction and can be arranged obliquely with respect to the direction tangential to the rotor axis. As a result of the arrangement of the guide devices 17 in the pole gap 1, high flow velocities occur in the area of the guide devices 17 and the flow preferably receives an axial component on the cooling surfaces of the field winding in the pole gap.

FIG. 8 schematically shows another exemplary embodiment for salient pole machines, in which the coolant flow exits from slots 11 of the rotor yoke 12, hollow displacement bodies 18 with outlet nozzles 19 being provided toward the excitation winding. The hollow displacement bodies 18 are arranged in the axial direction over the greater part of the pole length in the pole gap 1. The hollow displacement body 18 is open to the space 13 between the excitation winding 21 and the rotor yoke 12, so that the coolant flow can flow directly into the hollow bodies from the slots 11 of the rotor yoke 12. The axial length of a hollow body 18 is preferably greater or approximately corresponds to the axial length of a slot 11 of the rotor yoke 12 and its number is preferably not greater than the number of slots 11 of the rotor yoke 12. The nozzle-like outlet 19 can be straight or rotated, one of which additional deflection takes place so that the flow receives an axial component. Additional guide devices can be arranged within the hollow body 18.

In FIG. 9, the winding head including the side edges is covered by the pole shoe 10, that is to say that over the pole shaft 10 20 protruding length of the pole piece 10 is equal to the width of the flat copper conductor 4. In this embodiment, the upper or the upper flat copper conductor 9 have openings 8 to the outside.

The base of an excitation winding can be formed with inlet openings 6 in the lower flat copper conductor 7, as shown in FIG. 10. To reduce the entry losses, the edges of the entry openings 6 are rounded.

As in FIG. 5, according to the schematic illustration in FIG. 11, in another exemplary embodiment, the outer edge region 3 of the winding layers can have a smaller height (extension in the radial direction) than the region of the winding layers between the pole shaft 20 and this outer edge region 3 the insulating layers only over this intermediate area, ie they do not extend, or only slightly, into the edge region 3 with the reduced height. The openings forming the flow paths in the winding layers are preferably located in this edge region with a reduced height, the gaps between the winding layers of the reduced height leaving openings that connect the flow paths with the pole gap. Such breakthroughs to the pole gap can contribute to effective cooling of the field winding. In contrast to FIG. 5, broken lines in FIG. 11 indicate that window-like openings 14 in the winding layers, which are completely surrounded by the material of the winding layers, do not always have to be required to form the flow paths 2; rather, the winding layers themselves

Have openings which connect the flow paths 2 or openings 4 completely in the edge region of the winding layers with the pole gap 1. The edge area 3 of the winding layers then acts in this area as an additional cooling fin of each winding layer. These openings can be provided on the outermost flow paths in each individual winding layer. 11 hen, but preferably only individual openings and / or individual winding layers carry such openings.

Furthermore, the broken lines in FIG. 11 already indicate that the openings 14 in the individual

Winding layers do not necessarily have to be the same size and the edges of these openings do not necessarily have to be aligned with one another. This is shown even more clearly in FIG. 12, where the cross section of the openings 14 is selected to be smaller and larger in an alternating sequence.

The exemplary embodiment according to FIG. 13 contains a displacement body 16 which, like the example in FIG. 6, is arranged in the pole gap between two adjacent legs. The displacement body 16 of FIG. 13, however, has side surfaces 26 on which it is supported on the excitation windings of the two adjacent legs. These supporting side surfaces 26 preferably extend practically over the entire length of the side edges of the winding layers, that is to say practically over the entire axial length of the two adjacent excitation windings. He can e.g. be made of a light material, solid or have a cavity to reduce its mass. To improve the cooling, such a cavity can also be flowed through by the cooling medium. In Figure 13 it is shown that in the displacement body (more precisely: in the area which is adjacent to the supporting outer surfaces 26) to improve the cooling further flow paths 25 are incorporated, which connect the surroundings of the pole foot with the winding head space and improve the cooling of the winding layers .

In addition, the supporting outer surfaces 26 of the displacement body 16 are advantageously formed by one or more elastic intermediate layers 24, which compensate for the manufacturing tolerances of the field winding and of the displacement body. 12 Such a displacement body, which bridges the entire distance between two adjacent field windings (ie pole gap 1), supports the pole windings against each other so that deformations of the field system are avoided. At the same time, the coolant flow can be divided and guided in an optimal manner.

The best mechanical hold would be provided by a filling compound which practically fills the entire pole gap between the field windings up to the rotor yoke and only leaves out suitable access channels to flow paths 2 and to further flow paths 25. However, since the supply of the cooling medium through a hollow rotor axis and corresponding outlet slots in the rotor axis requires a large construction, the pouring out of the correspondingly large pole gaps is difficult to carry out in terms of production technology. It is therefore more favorable to use a prefabricated displacement body - possibly with the elastic intermediate layers 24 mentioned - which is then attached (e.g. with a potting compound) to the excitation windings. A further possibility of mechanical mounting is shown in FIG. 14, the pole piece of which covers the outer edge region 3 and projects beyond the outer side edges of the winding layers so that it overlaps the displacement body 16. The overlapped part and the supporting side surfaces of the displacement body 16 then represent a practically form-fitting mounting of the displacement body. The flow paths 2 formed by the openings in the winding layers and the further flow paths 25 can thereby pass through outlet openings in the pole piece or - as in FIG. 14 is shown - to be guided around the overlapping part of the pole piece.

The features specified in the subclaims and the descriptions of the individual figures can advantageously be combined with one another to form further exemplary embodiments.

Claims

13 claims

1. Ventilation system for a star-shaped excitation system of a salient pole machine with legs (34) extending radially outward from a rotor axis, which are separated in the tangential direction from one another by pole gaps (1) each passing into a winding head space and a pole shaft (20), one around the Pole shaft (20) encircling excitation winding (21), in particular at least one flat copper conductor (4), with a plurality of winding layers (7, 9) and insulating layers (5) arranged between the winding layers, and having a pole piece (10) arranged on a head of the excitation winding, characterized in that openings (14) in the winding layers (4, 5, 7, 9) form flow paths (2) which run along the side (36) of the excitation winding facing away from the pole shaft and directly or at least via the pole gap (1) into the Winding head space open.

2. Ventilation system according to claim 1, d a d u r c h g e k e n n z e i c h n e t that additional guide devices (17, 22, 18, 19) are introduced in the space (13) between the excitation winding (21) and a rotor yoke (12) formed by a foot of the leg.

3. Ventilation system according to claim 1 or 2, d a d u r c h g e k e n n z e i c h n e t that on the outside of the excitation winding (21) cooling surfaces, e.g. axial or radial cooling ribs (15) which are continuous or interrupted on the outside or which are twisted or needle-shaped at their base.

4. Ventilation system according to one of claims 1 to 3, characterized in that the flow paths (2) are formed only along the outer surface (36) of the excitation winding pointing towards the pole gap (1). 14

5. Ventilation system according to one of claims 1 to 4, d a d u r c h g e k e n n z e i c h n e t that the flow paths over several lateral openings with the pole gap

(1) are connected.

6. Ventilation system according to one of claims 1 to 5, characterized in that an outer edge region (3) of each winding layer has a lower height than the area of the winding layers between the pole piece (20) and the outer edge region (3), and that the insulating layers (5) extend at most slightly into the edge area (3).

7. Ventilation system according to one of claims 1 to 6, that the pole shoe (10) practically completely covers the head of the field winding and the flow channels on the outside of the field winding open laterally via the openings (14) into the pole gap (1).

8. Ventilation system according to one of claims 1 to 7, d a d u r c h g e k e n n z e i c h n e t that the flow channels on a lower winding layer (7) from openings (6) with a rounded or beveled edge.

9. Ventilation system according to one of claims 1 to 8, so that the openings (14) of the successive flat copper conductors (4) have different flow cross-sections in an alternating sequence.

10. Ventilation system according to claim 1, d a d u r c h g e k e n n z e i c h n e t that an elongated displacement body (16), the longitudinal direction of which is practically parallel to the rotor axis, is arranged in the pole gap (1).

15 11. Ventilation system according to one of claims 1 to 10, characterized in that in the pole gap (1) a guide device (17) with a fastening part (23) and guide vanes (22) are arranged, the guide vanes (22) preferably in the The direction parallel to the rotor axis has approximately the same extent as slots (17) through which the cooling medium can be introduced radially into the pole gap.

12. Ventilation system according to one of claims 1 to 11, characterized in that in the pole gap (1) extends at least one elongated hollow displacement body (18) in the direction of the rotor axis, which has outlet nozzles towards the excitation winding (21), the hollow one Displacement body (18) to the space (13) between the field winding (21) and a rotor yoke (12) arranged at the lower end of the pole shaft is open.

13. Ventilation system according to one of claims 1 to 12, so that the pole gap (1) between two adjacent excitation windings (21) contains a displacement body (16) with side faces which are supported on these two excitation windings (21).

14. Ventilation system according to claim 13, so that the supported side surfaces of the displacement body (16) are each formed by at least one elastic intermediate layer.

15. Ventilation system according to claim 13 or 14, characterized in that the displacement body (16) is supported on the excitation windings practically over the entire axial length of the legs. 16

16. Ventilation system according to one of claims 13 to 15, so that further flow paths (25) lead in the radial direction through the displacement body (16) in the region of each supported outer surface (26).

17. Ventilation system according to one of claims 13 to 16, so that the pole piece (10) overlaps the displacement body (16) at the top.

18. Ventilation system according to one of claims 1 to 17, d a d u r c h g e k e n n z e i c h n e t that all flow paths are fluidically connected to a cavity in the rotor axis.