Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/28—Coils; Windings; Conductive connections
  • H01F27/288—Shielding
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K3/00—Details of windings
  • H02K3/46—Fastening of windings on the stator or rotor structure
  • H02K3/48—Fastening of windings on the stator or rotor structure in slots
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K15/00—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K3/00—Details of windings
  • H02K3/04—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors
  • H02K3/28—Layout of windings or of connections between windings
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K2203/00—Specific aspects not provided for in the other groups of this subclass relating to the windings
  • H02K2203/15—Machines characterised by cable windings, e.g. high-voltage cables, ribbon cables
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K3/00—Details of windings
  • H02K3/32—Windings characterised by the shape, form or construction of the insulation
  • H02K3/40—Windings characterised by the shape, form or construction of the insulation for high voltage, e.g. affording protection against corona discharges

Definitions

• the present invention relates in a first aspect to a rotating electric machine of the type described in the preamble to claim 1, e.g. synchronous machines, normal synchronous machines as well as dual-fed machines, applications in asynchronous static current converter cascades, outerpole machines and synchronous flow machines.
• a second aspect of the invention relates to a method of the type described in the preamble to claim 18.
• the machine is intended primarily as a generator in a power station for generating electric power.
• the machine is intended to be used at high voltages.
• High voltages shall be understood here to mean electric voltages in excess of 10 kV.
• a typical operating range for the machine according to the invention may be 36 to 800 kV.
• XLPE Cross-linked polyethylene .
• Securing the cable in the slot is also a problem - the cable is to inserted into the slot without its outer layer being damaged.
• the cable is subjected to currents having a frequency of 100 Hz which cause a tendency to vibration and, besides manufacturing tolerances with regard to the outer diameter, its dimensions will also vary with variations in temperature (i.e. load variations) .
• the water-and-oil-cooled synchronous machine described in J. Elektrotechnika is intended for voltages up to 20 kV.
• the article describes a new insulation system consisting of oil/paper insulation which enables the stator to be completely immersed in oil .
• the oil can then be used as coolant at the same time as constituting insulation.
• a dielectric oil-separating ring is provided at the internal surface of the core to prevent oil in the stator from leaking out towards the rotor.
• the stator winding is manufactured from conductors having oval, hollow shape, provided with oil and paper insulation. The coil sides with the insulation are retained in the slots with rectangular cross section by means of wedges. Oil is used as coolant both in the hollow conductors and in cavities in the stator walls.
• Such cooling systems necessitate a large number of connections for both oil and electricity at the coil ends.
• the thick insulation also results in increased radius of curvature of the conductors which in turn causes increased size of the coil overhang.
• the above-mentioned US patent relates to the stator part of a synchronous machine comprising a magnetic core of laminated plate with trapezoid slots for the stator winding.
• the slots are stepped since the need for insulation of the stator winding is less in towards the rotor where the part of the winding located closest to the neutral point is situated.
• the stator part also includes a dielectric oil-separating cylinder nearest to the inner surface of the core. This part could increase the excitation requirements in comparison with a machine lacking this ring.
• the stator winding is manufactured from oil-saturated cables having the same diameter for each layer of the coil . The layers are separated from each other by means of spacers in the slots and secured with wedges.
• Characteristic of the winding is that it consists of two "half-windings" connected in series. One of the two half-windings is situated centrally inside an insulating sheath. The conductors of the stator winding are cooled by surrounding oil. A drawback with so much oil in the system is the risk of leakage and the extensive cleaning-up process resulting from a faulty condition.
• the parts of the insulating sheath located outside the slots have a cylindrical part and a conical screening electrode whose task it is to direct the electrical field strength in the area where the cable leaves the plate.
• the oil-cooled stator winding consists of a conductor with insulation for medium-high voltage, having the same dimension for all layers.
• the conductor is placed in stator slots which are in the shape of circular, radially situated openings corresponding to the cross-sectional area of the conductor and necessary space required for fixation and cooling.
• the various radially located layers of the winding are surrounded and fixed in insulating tubes . Insulating spacer elements fix the tubes in the stator slot.
• an inner dielectric ring is also required here to seal the oil coolant from the inner air gap.
• the illustrated construction shows no stepping of either insulation or stator slots.
• the construction shows an extremely narrow, radial waist between the various stator slots, entailing a large slot leakage flow which greatly affects the excitation requirements of the machine.
• the present invention is related to the above-mentioned problems associated with avoiding damage to the surface of the cable upon its insertion into the stator slots and avoiding wear against the surface caused by vibration during operation.
• the slot through which the cable is inserted is relatively uneven or rough since in practice it is extremely difficult to control the position of the laminated plates sufficiently exactly to obtain a perfectly uniform surface.
• the rough surface has sharp edges which may shave off parts of the semiconductor layer surrounding the cable . This leads to corona and break-through at operating voltage.
• the cable is also subjected to thermal loading so that the XLPE material expands.
• the diameter of a 145 kV XLPE cable increases by about 1.5 mm at an increase in temperature from 20 to 70°.
• the cable must be given the necessary Space due to thermal expansion.
• the object of the present invention is to solve the problems associated with achieving a machine of the type under consideration so that the cable is not subjected to mechanical damage during winding as a result of vibrations, and which permits thermal expansion of the cable. Achieving this would enable the use of cables that do not have a mechanically protecting outer layer. In such a case the outer layer of the cable would consist of a thin semiconductor material which is sensitive to mechanical damage .
• At least one semiconducting layer has a coefficient of thermal expansion equivalent to that of the intermediate solid insulation. Defects, cracks and the like are thus avoided upon thermal movement in the conductor.
• the invention is primarily intended for use with, and its advantages become particularly apparent in connection with, a high-voltage cable built up of an inner core having a plurality of strand parts, an inner semiconducting layer, an insulating layer surrounding this and an outer semiconducting layer surrounding the latter, a cable in particular having a diameter of 20-200 mm and a conducting area of 40-3000 mm ⁇ .
• the resilient bodies are arranged beside and close to respective cable lead-throughs.
• each resilient body is arranged to abut onto two adjacent cable lead-throughs, thereby reducing the number of bodies required.
• the advantages of the invention are of particular interest when the slots are provided with alternately wide and narrow parts. Such a design ensures stable fixing of the cable and enables optimum utilization of the space for the stator laminations.
• the space at the other slot wall may then be wider and provide space for the resilient bodies.
• the other slot wall in the corresponding area to be flat and constitute a tangent to adjacent wide parts.
• the bodies are suitably of silicon rubber. This is suitable in view of its elasticity and also because it lacks process oil which might otherwise diffuse out and attack the outer semiconducting layer of the cable.
• each resilient body has a convex profile in axial section. This offers less friction resistance when the bodies are inserted into the slot .
• the bodies are designed as support members arranged around the cable and surrounding it .
• the support members facilitate insertion of the cable into the slot when the stator is being wound.
• the cable is then drawn through these, each support body contributing to centring the cable in the slot as it is being drawn towards the next.
• the cable is in this case relatively rigid so that it may be guided towards the next support member and may be threaded through it.
• the rigidity of the cable ensures that there is no risk of it touching the slot walls during insertion. The risk of the laminations in the wall scratching the sensitive outer surface of the cable, resulting in damage, is therefore eliminated.
• the support members are arranged in annular recesses in the slot wall.
• Each support member is suitably in the form of a rubber ring and it is advantageous for these to be glued into the slot wall.
• Inserting resilient bodies in this way produces a machine with supports for the cable lead-throughs in the slots so that vibration damage is avoided.
• the bodies are inserted after the stator has been wound, in a space formed between the adjacent cable lead-through and the slot wall .
• the bodies are hereby caused to expand after they have been inserted into their places. This enables them to be inserted without being hindered by friction against cable and slot wall during the insertion process.
• the body is expanded only through axial compression or by being pre-compressed in this direction upon insertion and then relieved of this pre- compression.
• each body inserted has a cavity running axially through it and the cable is threaded through after the bodies have been applied. It is thus threaded through these cavities. .
• Figure 1 shows schematically an end view of a sector of the stator in a machine according to the invention
• Figure 2 shows a cross-section through a cable used in the machine according to the invention
• Figure 3 shows a radial partial section through a stator slot according to the invention
• Figure 4 shows an extracted perspective view of details in Figure 3 .
• Figure 5 shows a perspective view of a detail according to the invention
• Figure 6 shows a circle section through a detail according to the invention
• Figures 7-9 show sections taken along the line VII-VII in Figure 3, illustrating a first embodiment of the method according to the invention
• Figure 10 is an axial section through an auxiliary means according to a second embodiment of the method according to the invention.
• Figure 11 is a section taken along the line VII-VII in Figure 3, illustrating a second embodiment of the method according to the invention
• Figure 12 is a section like that in Figure 11, illustrating a third embodiment of the method according to the invention.
• Figures 13-18 are axial sections through details in Figure 8 according to two alternative embodiments of the method according to the invention
• Figure 19 is a basic diagram showing the cable arranged in the stator, according to one alternative embodiment
• Figure 20 is a detail of Figure 19 when the machine is at rest
• Figure 21 is a detail corresponding to Figure 20 but when the machine is in operation
• Figures 22 and 23 are alternative embodiments of the detail in Figure 20.
• the stator is composed in conventional manner of a laminated core of sheet steel .
• the figure shows a sector of the machine, corresponding to one pole division. From a yoke portion 3 of the core situated radially outermost, a number of teeth 4 extend radially in towards the rotor 2 and are separated by slots 5 in which the stator winding is arranged.
• the cables 6 in the windings are high- voltage cables which may be of substantially the same type as high-voltage cables used for power distribution, so-called XLPE cables.
• One difference is that the outer mechanically protective sheath and the metal screen that normally surround such a cable have been eliminated.
• the cable thus comprises only the conductor, an inner semiconducting layer, an insulating layer and an outer semiconducting layer. The semiconducting layer, sensitive to mechanical damage, is thus exposed on the surface of the cable .
• each slot 5 has varying cross section with alternating wide parts 7 and narrow parts 8.
• the wide parts 7 are substantially circular and surround cable lead-throughs, and the waist parts between these form narrow parts 8.
• the waist parts serve to radially position each cable lead-through.
• the cross section of the slot as a whole also becomes slightly narrower in radial direction inwards. This is because the voltage in the cable lead-throughs is lower the closer they are situated to the radially inner part of the stator. Slimmer cable lead-throughs can therefore be used here, whereas increasingly coarser cable lead-throughs are required further out.
• cables of three different dimensions are used, arranged in three correspondingly dimensioned sections 9. 10, 11 of the slots 5.
• FIG. 2 shows a cross-sectional view of a high-voltage cable 6 according to the present invention.
• the high- voltage cable 6 comprises a number of strand parts 31 made of copper (Cu) , for instance, and having circular cross section. These strand parts 31 are arranged in the middle of the high-voltage cable 6.
• a first semiconducting layer 32 Around the strand parts 31 is a first semiconducting layer 32.
• an insulating layer 33 e.g. XLPE insulation.
• Around the insulating layer 33 is a second semiconducting layer 34.
• the concept "high-voltage cable" in the present application thus need not include the metal screen and the outer protective sheath that normally surround such a cable for power distribution.
• Figure 3 illustrates on a larger scale a slot 5 with alternating narrow parts 7 and wide parts 8 as in Figure 1, but differing somewhat from those shown in
• Figure 5 in that the narrow parts 7 are formed by an indentation in the slot wall on only one side of each narrow part 7.
• a space which can be described as roughly triangular is formed in the section of the opposite slot wall facing the indentation, and in each such space a number of resilient bodies 12, 13, 14 are arranged.
• Each resilient body is in pressure contact with the slot wall and also with two adjacent cable lead-throughs 6, the latter thus being clamped by the resilient bodies.
• the resilient bodies are made of a type of rubber that does not contain remnants of process oil, e.g. silicon rubber.
• FIG. 4 shows two cable lead- throughs and how the resilient bodies 13a, 13b, etc. are arranged axially along the cable lead-throughs along the whole length of the stator.
• the bodies 13a, 13b shown in Figure 4 are in the form of circular cylinders but may advantageously be somewhat cambered so that they acquire a barrel-like shape as illustrated in Figure 5.
• the cross-section of the bodies perpendicular to the axial direction need not be circular but, as illustrated in Figure 6, have a shape more suited to the available space.
• FIGS 7-12 all of which are sections taken along the line VII-VII in Figure 3, reveal two alternative methods of inserting the resilient bodies.
• Figures 7-9 show three stages of the insertion according to a first alternative.
• a rod 15 with a plate 16 at one end is inserted in the "triangular" space between two cable lead-throughs 6 (only one of which is visible in the figures) and the stack of laminations in the stator 1.
• the first body 13a is threaded onto the other end of the rod.
• Each body has a cavity 17 running axially through it, substantially corresponding to the diameter of the rod 15.
• the first body 13a is inserted into the slot 5, sliding along the rod 15.
• the cross-sectional shape of the body is such that it can be freely inserted through the slot in this way but with little clearance.
• Figure 8 shows how an axial pressure A is applied to the body 13a when it is in place, thereby compressing the body axially so that it simultaneously expands in transverse direction.
• This expansion and the unloaded dimensions of the body are selected such that in this position it will be in contact with both the slot wall and the two cable lead-throughs.
• a locking device 18a is applied which is pushed axially along the rod to abutment with the body 13a, thereby locking it in this expanded state.
• the next body 13b is then pushed axially along the rod until it is in contact with the locking device 18a, after which it is compressed axially and locked in place with a second locking device 18b in the same way as the first body 13a.
• the following bodies 13c, 13d, etc. are then applied one after the other in corresponding manner until the slot has been filled.
• Figures 13 and 14 show a first example of how the locking device 18 may be shaped.
• the rod 15 here is provided with serrations 19 with inclined surfaces 20 and perpendicular surfaces 21, respectively, in relation to the longitudinal axis of the rod, the inclined surfaces facing the threading end of the rod.
• the locking device itself is shown in Figure 14 and consists of a plastic sleeve, e.g. of nylon, having a first part with an inner diameter di corresponding to the outer diameter of the rod, and a second part with an inner diameter d2 which is slightly larger.
• a thin, inclined flange 22 is formed leaving an opening with a diameter d3 which is smaller than the outer diameter of the rod, suitably corresponding to the diameter at the bottom of the serrations.
• the flange is sufficiently thin to be able to resilient snap over the serrations 19 when the sleeve 18 is passed over the serrated rod in the direction of the arrow B and which can snap into a groove formed by two serrations and is thus prevented from moving in the opposite direction.
• FIG. 15-18 Another example of how the locking device may be designed is shown in Figures 15-18.
• Figures 15 and 16 show the rod with screw threading on only two opposite segments 23 and flat on the other two opposite sides 24.
• the locking device in Figures 17 and 18 is in the form of a sleeve 18 ' having internal threading 25 on two opposite segments and a hole diameter down to the bottom of the thread between. This enables the sleeve 18', in a position where its threaded segments 25 are turned 90° in relation to the threaded segment 23 of the rod, to be threaded over the rod. When the sleeve 18' has been moved in this way to its locking position, it is turned to engagement between the threaded segments 23 and 25 and firmly locked in this position. A notch 26 is provided at one end of the sleeve 18 ' in order to turn it .
• the sleeve 18, 18' in the locking devices described above has an axial length to suit the desired distance between the bodies 13a, 13b, etc. and thus also acts as spacer.
• FIG. 10-12 An alternative method of inserting the resilient bodies 13 is illustrated in Figures 10-12 showing the various stages for insertion and application of a body 13.
• a tube 27 is inserted axially into the space between the slot wall and the adjacent cable lead-throughs 6.
• the tube 27 has a cross-sectional shape to enable its insertion into the space with slight clearance.
• the tube 27 is provided at its outer end with a funnel-like section 28. This expands to dimensions wider than the available space in the slot and therefore does not reach into the slot upon application of the bodies 13.
• a resilient body is inserted in uncompressed state into the funnel-like section 28 and, on passing this section 28, it will be compressed at right angles to the axial direction and thus become somewhat longer.
• the body 13 is then pressed through the tube to its opposite end, e.g. by a rod 29 with a pressure plate 30 at its end.
• the rod 29 is then locked in this position and the tube 27 is pulled out a short distance, i.e. in the direction of the arrow C ( Figure 11) .
• the body 13 is prevented by the pressure plate 30 from accompanying the movement of the rod , and will consequently be fed out of the tube 27 when this is withdrawn. It is then free to expand transversely to the axial direction, as can be seen in Figure 11 where the body 13 is partially pressed out .
• the tube can be withdrawn sufficiently to allow the whole resilient body 13 to exit from the tube and expand. In expanded state it presses against both the slot wall and the adjacent cable lead-throughs 6 as shown in Figures 3 and 4. The same procedure is then repeated with the next and following resilient bodies, with the tube drawn further and further out of the slot .
• Figure 12 illustrating the same position as Figure 11, shows an alternative method of pressing the resilient bodies through.
• a pressurized fluid e.g. compressed air
• the body 13 When the body 13 has been inserted into its position the outer end of the tube is sealed with a tight lid 32 through which a compressed air conduit 33 communicates with the interior of the tube.
• a compressed air conduit 33 When the valve 34 is opened the air forces the body 13 into its position, after which the tube 27 is withdrawn as described above.
• the tubes 13 may be suitable to lubricate them with talcum or boron nitride, for instance.
• the inside of the tube may be lubricated.
• Figure 19 shows a lead- through of the cable 6 through one of the stator slots 1, the figure showing its axial extension.
• Support members 112 for the cable are arranged at regular intervals. The distance between support members is chosen so that vibrations, particularly in the frequency range 100 Hz, are suppressed, resulting in about 2 - 4 support elements per metre of cable .
• Figure 20 shows such a support member 112 on an enlarged scale when the machine is at rest .
• the support member 112 is deformable, suitably resilient, and is preferably made of rubber.
• rubber includes other materials having rubber-like properties.
• the rubber element 112 is annular and is applied in an annular recess 113, about 5 mm deep, in the wall of the slot 5.
• the rubber ring 112 is glued to the bottom of the recess 113.
• the rubber ring has an inner diameter approximately corresponding to the cold diameter of the cable 6, or somewhat larger.
• the outer diameter corresponds to the diameter of the recess 113 and its length is about 10-15 mm.
• the cable 6 When the stator is wound the cable 6 is inserted axially into a slot .
• the slot has a width greater than the diameter of the cable to permit expansion thereof when it becomes hot during operation.
• the cable is drawn through the aperture in each rubber ring 112 so that it is centred in the slot .
• the cable is thus prevented from coming into direct contact with the walls of the slot 5 and there is therefore no risk of the laminations damaging the outer sheath of the cable.
• a high-voltage cable of the type under consideration is relatively rigid so that it is guided in its central position as it passes from one rubber ring to the next .
• the cable is lubricated during winding to facilitate its passage through the rubber rings.
• the rubber rings may also be slightly bevelled at the side of the hole where the cable enters, or the tip of the cable may be slightly bevelled so that it is slightly conical.
• the cable 6 When the machine is in operation the cable 6 will expand due to heat in the copper core .
• the rubber ring is then compressed as shown in Figure 5.
• the width of the slot 5 is selected so that during operation the cable will expand until it abuts lightly onthe slot wall .
• the rubber ring 112 is then compressed in the recess 113, which has sufficient depth to permit this.
• the inner diameter of the rubber ring 112 will then be approximately the same as the slot width. In this position the cable is firmly clamped at 2 - 4 places per metre, but lies relatively loosely against the slot wall in between.
• the rubber element 112 in Figure 20 need not necessarily have triangular cross-section.
• Figures 20 and 23 show two alternative embodiments of the rubber element.
• the element 112a has an equilateral triangular part formed by two inclined surfaces 114 facing the cable 6 so that the contact is at points (along a circular line) at the tip 115.
• the inclined surfaces 114 facilitate insertion of the cable.
• the element 112b has a correspondingly triangular part in cross-section but with only one inclined surface 114b facing the direction from which the cable is inserted. Contact is then obtained at the tip 115b on the one side of the element.
• contact will occur with a surface having a certain lateral extension also.
• this has a trapezium-shaped part with the shorter side facing the cable, or is shaped with a convex surface towards the cable.
• the rubber rings 112 according to the invention enable the cable to be drawn easily during winding, without risk of damage to the outer semiconducting layer of the cable, and avoid damaging vibrations in the cable during operation.

Landscapes

• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Insulation, Fastening Of Motor, Generator Windings (AREA)
• Manufacture Of Motors, Generators (AREA)

Applications Claiming Priority (7)

Publications (1)

Family

ID=27355824

Family Applications (1)

Country Status (8)

Families Citing this family (4)

Family Cites Families (9)

• 1997
  • 1997-05-27 CN CN97195039.3A patent/CN1220046A/zh active Pending
  • 1997-05-27 PL PL97330194A patent/PL330194A1/xx unknown
  • 1997-05-27 WO PCT/SE1997/000907 patent/WO1997045932A1/en not_active Application Discontinuation
  • 1997-05-27 EP EP97924481A patent/EP1016188A1/en not_active Withdrawn
  • 1997-05-27 JP JP54222197A patent/JP2001507918A/ja active Pending
  • 1997-05-27 AU AU29894/97A patent/AU2989497A/en not_active Abandoned
  • 1997-05-27 BR BR9709376-9A patent/BR9709376A/pt not_active Application Discontinuation
  • 1997-05-27 CA CA002255720A patent/CA2255720A1/en not_active Abandoned

Non-Patent Citations (1)

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