MXPA01009914A

MXPA01009914A - Improvements in electrical machines.

Info

Publication number: MXPA01009914A
Application number: MXPA01009914A
Authority: MX
Inventors: Charles Neville Glew
Original assignee: Alstom Uk Ltd
Priority date: 1999-04-01
Filing date: 2000-03-31
Publication date: 2002-08-20
Also published as: AU3565000A; GB9907527D0; CA2368557A1; ZA200108545B; NO20014766D0; WO2000060721A1; GB0007946D0; EP1171941A1; GB2351851A; NO20014766L

Abstract

A composite conductor (30) comprises strands (31) of conductor material forming a conductor bundle (32) of generally rectangular shape, the strands being insulated from each other within the bundle. An insulating sleeve (36) of homogeneous polymeric material surrounds the conductor bundle (32); the insulating sleeve also having a rectangular shape. The polymeric material of the sleeve is filled with at least one insulating filler material which conducts heat more efficiently than the polymer alone, and a coating of conductive material (38) forms a corona shield on the inner and outer surfaces of the insulating sleeve. By virtue of its construction and the materials it uses, the composite conductor (30) provides a high efficiency winding (46) for the stator (40) of an electrical machine. The invention also includes a stator having a winding comprising the composite conductor and manufacturing methods for the composite conductor and the stator.

Description

IMPROVEMENTS IN ELECTRICAL MACHINES Field of the Invention The present invention relates to electrical machines and in particular to insulated electrical conductors suitable for use as excitation windings in the stators of high voltage electrical machines such as, for example, machines operating at voltages greater than 3KV.

BACKGROUND OF THE INVENTION The known types of excitation winding for the stators of said machines, generally comprise solid rectangular copper conductors which are electrically isolated from each other and from a laminated steel core connected to ground in which they are wound. The materials used to insulate the conductors are selected to have properties, such as thickness, thermal conductivity, dioelectric resistance, and permissiveness - which are appropriate for the size of the machine, the applied voltage and the temperature increase. The energy output of a rotary electric machine (either a motor or a generator) is a function of the properties of the laminated magnetic steel core, the excitation windings, and its operating temperatures, "a coefficient of outputs" or "speci fi c torsion coefficients" of said machines are generally emphasized as useful means for comparing the energy outputs of machines of different designs. The units are volume twists per unit and may be derived, dividing the energy output of the machine by the stator volume within the separation periphery. Having been the subject of industrial manufacturing for more than 100 years, rotating electrical machines are considered as a mature product using mature technologies. During the century of production, the materials and processes used in its construction have evolved slowly resulting in a stable increase in the output coefficient (approximately 3.0% per year) for the most popular machines. Recently, their evolutionary progress has diminished and reached a maximum, suggesting that additional developments are either unlikely or would be very slow. It is necessary to externally isolate the windings of the extractor of said machines from each other and the core of the stator. It is also necessary to isolate the windings internally, isolating the conductors of each one of them. inside the winding. Currently insulating materials perform the function of insulation and have only a limited capacity to withstand high temperatures, with modest properties of electrical resistance and generally poor thermal conductivity. In addition, during the operation of the machines, the heat generated due to the electrical losses in the winding conductors, but the poor thermal conductivity of the I 10 insulation materials results in a poor heat transfer, and this in turn inhibits the production coefficients of the machines in which the insulating materials are used. As there are only small differences between the insulation systems of the stator winding currently used by the main manufacturers of the machines, the thermal and dioelectric operation of said system is similar. Generally, all use combinations of mica, film polyester and woven glass materials impregnated with synthetic resin. The mica is used in the form of a "paper" which is supported either by the polyester film, or the woven glass and is wound around the conductors to insulate them from external contact.

To complete the isolation process, they are • » ** impregnated by vacuum pressure, with the synthetic resin (for example, an epoxy resin) as the last process after placing the winding inside the stator.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the coefficients of production of electric machines and, therefore, to reduce their capital costs by production 10 in KW of electric power by increasing the capacity of • heat transfer from its stator conductive windings. This is achieved in the present invention by means of a novel type of composite conductor. In accordance with the present invention, a composite conductor 15 for use as a winding of a high-voltage electrical machine comprises: a plurality of wires of conductive material that ^ J? they form a conductive beam which in its cross section is of a generally rectangular shape, the wires being isolated from one another within the bundle. an insulating sleeve of a substantially homogeneous polymeric material surrounds the driver's beam; the elastic sleeve also having a generally rectangular shape in its cross section, and the polymeric material being filled with at least one « electrically insulating filler material, which conducts heat more efficiently than polymer alone, and a conductive material that forms a corona protection coating on the inner and outer surfaces of the insulating sleeve. The conductive beam is impregnated with an insulating material that can be cured, resistant to high temperatures, such as a synthetic resin or a f 10 polymer material, by means of which the cured composite conductor becomes strong and rigid enough to make possible its use in the windings of electrical machines. It should be understood that the term "Rectangular" as used in the present description includes shapes which are square (having four sides and all of substantially equal dimensions) and rectangles and squares having rounded corners. A composite conductor according to the present invention, by virtue of its construction and the materials it uses, provides a high efficiency winding for the stator of an electrical machine. Due to its filling materials, the insulating sleeve does not only has dioelectric resistance properties Superiors which allow the operation in μ? - ^ - ^ * Reduced thickness of the cuff wall, and / or increased electrical stress, but also have a much higher thermal conductivity and thermal capacity Tff (resistance to temperature) than the known windings. The higher thermal conductivity allows a considerable increase in the heat transfer capacity of the composite conductor inside the stator core, which can be cooled by a heat exchanger with air jets. Furthermore, in the isolation of the wires of the conductor, one of the others substantially reduces the losses of high-frequency eddy currents in the stator winding, and the coating of the The conductive surface in the insulating sleeve contributes to making safe operation possible at higher electrical stresses on the surface of the sleeve. A net result of the above is that the production coefficient is substantially increased and hence the The cost of capital of the energy supplied is diminished in a substantial manner. Preferably, the corners of the rectangular shape of the beam are curved to minimize the electrical stress concentrations. The dimension of the curve can be up to 5mm, preferably It is preferred that the corners of the insulating sleeve be substantially rectilinear, having a curve that is not greater than about Im. 9F 5 Preferably, the threads of the conductive material are collectively twisted around the longitudinal centerline of the conductive bundle in a similar manner in which the threads of a mantle are twisted around the longitudinal centerline of the mantle.

This angular / spatial transposition of the wires of the ^ Longitudinal conductive material of the beam due to its twisting, inherently cancel the eddy currents as they originate, reducing or eliminating in a substantial way the losses associated. Preferably the use of at least one insulating filler material in the polymer insulator sleeve is a metal oxide and / or a metal nitride. The material of the polymeric sleeve comprises Preferably a high temperature polymer, for example, a polymer selected from the groups comprising fluoropolymers and aromatic polymers, and the conductive coating material to reduce variations in electrical stress on the surfaces of the composite conductor may comprise a graphite or silicone-based material, preferably a temperature-resistant polymer or a paint material which has a sufficient amount of the conductive material incorporated therein to produce ^^ 5 its conductivity. Preferably, the wires of the conductive material comprise copper, but other materials, such as aluminum or silver, can also be used. In any material that the conductor threads are made, it is They prefer that they be isolated from each other by means of a coating of a synthetic resin or high temperature polymer material in each yarn. This can be achieved either by impregnation of the conductive beam, with a resin or a precursor polymer material in its uncured condition, or perhaps in a more convenient and reliable way, using conductor wires that have been previously manufactured with a ^ W |! F insulating coating before being incorporated into the conductive beam. Both of these coating techniques of the driver are well known in the art. The present invention further provides a process for making the above composite conductor, which comprises the steps of: gathering a plurality of threads of the material conductor to form a conductive beam. * and impregnate the conductive beam with an insulating material that can be cured resistant to high temperatures, impregnation occurring in a way • simultaneous with the process for gathering the threads and subsequent thereto, applying a coating of the conductive material to the outside of the twisted conductive bundle to form a first inner crown protector, extruding the insulating sleeve of homogeneous polymeric material 10 onto the coating of the conductive material in the conductive bundle, the conductive material having been previously filled with at least one insulating filler material which conducts the heat more efficiently than the polymer alone, and applying a coating of the conductive material to the outer surface of the conductive material. insulating sleeve to form a second external crown protection, wherein each of the wires of the conductive material is provided with an insulating coating by at least one coating of the yarns before forming the conductive bundle, and coating the yarns during the impregnation step. It is preferred that the conductive bundle be formed of a generally rectangular shape during the process of the formation of the beam or subsequent to it. In addition, after the process of forming the conductive bundle, the yarns thereof are twisted around a longitudinal central line of the bundle to form a twisted conductive bundle. As is known, impregnated Insulation wrappers of the conductive rod windings with a synthetic resin after they have been assembled in the stator, and then cure the resin partially or completely, it is anticipated that in the present invention, the impregnation occurs before the composite material is wound on the stator, the composite material then being wound on the stator while the resin or the precursor polymer material is not yet cured or is only partially cured. This does easier the impregnation process and allows easy handling of the composite conductor during the stator winding process before the resin is fully cured. The present invention also includes a stator for a rotary electric machine comprising a rolled steel core provided with a plurality of radically oriented slots extending longitudinally of the stator, a winding comprising each slot housing either a plurality of turns of a single length of the conductor above compound, or a plurality of turns comprising a plurality of lengths of the previous composite conductor, the successive turns of the composite conductor being in contact, and a radial register, with each other. The winding is retained in its groove, preferably by means of high thermal conductivity retaining the electrically fixed insulation, at the outer end of the groove in a radial manner. Preferably, the retention means is the composition of the filled polymer having a relatively high thermal conductivity compared to the polymer in its unfilled state. The retaining means comprise an extrusion which is forced into the end of the slot. It should be understood that the materials mentioned herein, in connection with the composite conductors according to the present invention, are considered the best of any likely suitable material.

BRIEF DESCRIPTION OF THE DRAWINGS The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which: FIG. 1 is a perspective view of a part of the interior of a stator of a rotary electric machine provided with a conventional winding; Figure 2 is a cross section of a composite conductor according to the present invention; Figure 3 is a cross section of an alternative composite conductor according to the present invention; Figure 4 is a radial section through the part of a stator according to the present invention, showing a stator groove containing a winding comprising six turns of the composite conductor illustrated in Figure 2; Figure 5 is a diagrammatic representation of a process for manufacturing a composite conductor in accordance with the present invention.

Detailed Description of the Invention With reference to Figure 1, the inner circumference of one end of a stator 10 of an electrical machine of C.A. The stator is intended to surround the rotor (not shown) of the machine electric. As is conventional, the stator body < It is composed of a large number of steel laminations and is formed with a large number of radially oriented slots 12 which extend # longitudinally of the stator body. Each of the grooves 12 houses an excitation winding 14, the successive "turns" 14A, 14B which make contact with each other and are in radial register within their groove. The windings are retained in their grooves by the wedges 16 J ^ 10 made of a suitable polymer insulating material such as filled epoxy resin. During the manufacture of the stator, the wedges 16 are forced into position within the mouths of the slots 12. The loops or "turns" of the windings each comprise solid rectangular copper conductor bars 14A, 14B which are preformed to the correct form to be possible its installation inside the stator slots. The conductor bars are electrically isolated from one another and from the steel core connected to ground by wrapping mica paper on a polymer film support, the wraps being impregnated by pressure with epoxy resin and subsequently cured. To be possible the construction of the winding of stator 14 from pre-formed lengths '1f & of the conductive bar, each of the turns of the winding consists of a plurality of lengths of the conductive bar whose ends 15 projecting from the stator core are bent at angles ^^^ 5 compounds as illustrated, being welded, or otherwise securely connected in electrical contact (not shown) to complete the turn. The ends of the radially adjacent conductor bars 14A, 14B are bent in directions opposite. As illustrated in Figure 1, where the ends of the conductor bars 14A, 14B, etc. project from the ends of the slots 12, the packing blocks 18, 20 are inserted between the adjacent conductor bars, the packing blocks 18 being adjacent to the end of the stator core and the packing blocks 20 being spaced apart from the stator core. Several of the packing blocks 18, 20 and the bent portions of some of the bars conductors 14A, 14B have been removed in the lower left part of figure 1 to show the construction in a clearer manner. The packaging blocks are molded to form them, being made of bags of glass material containing pieces of laminated filling of glass material and impregnated with epoxy resin. The packing blocks 20 are linked to the adjacent conductor bars by means of a strip of glass fiber 22. After assembly of the stator winding and the insertion of the packing blocks, the stator assembly is completed, tying the bent potions 15 of the conductor bars 14A, 14B to the support rings 24, 26 using a fiberglass rope 28. The packing blocks and support rings provide support to the ends of the conductor bars and prevent vibration during the service. Finally, the stator assembly is subjected to heat treatment at an appropriate cure temperature for its resin impregnated portions, this temperature being lower than one which will cause a deterioration of the polymer film component of the conductor shells. With reference to Figure 2, the composite conductor 30 is illustrated in cross-section and is intended to be used as the stator winding of a high-voltage electrical machine thereby replacing the wrapped solid conductor bars, 14A, 14B of figure 1. However, unlike the solid conductor bars, the core of the composite conductor 30 comprises a large number of wires 31 of the conductive material forming the conductive bundle 32. Preferably, the wires 31 **: • - * of the material conductor comprise copper, but you can also use other materials, such as aluminum (which is cheaper, but not an electrical material 'conductor as good as copper) or silver (expensive, 5 but that is a better electrical conductor). A typical dimension for an individual thread of a conductive material is likely to be of the order of O.lmm, so that it will be appreciated that the number of wires 31 necessary to form a conductive beam 32 is probably much more large than the number indicated in the diagram of the • Figure 2, and its cross sections will consequently appear smaller in relation to the total cross section of the conductor, composite 30. The conductive beam 32, although it is generally of rectangular shape, has rounded corners 34 to minimize the concentrations of electrical stress during the operation of the electric machine. The radius dimensions R of the corners of the conductive beam are in a range of 0.5 to 5mm; being the optimum of 2-3mm. To reduce the high-frequency eddy current losses in the stator winding, the copper wire bundle 32 is wrapped around the longitudinal centerline C of the material of the body. composite conductor 30 in a similar manner in which ^ * ^ The fibers are wrapped in a mantle around a longitudinal central line of the mantle. It should be understood that the transposition of the thread space 4B of the conductive material longitudinally within the bundle due to its twisted inherently cancels the parasitic currents as they originate. An insulating sleeve 36 of a high temperature polymer material (e.g., a fluoropolymer or aromatic polymer) surrounds the conductive bundle. Agree With the invention, the polymer is filled homogeneously into an insulating material which conducts heat more efficiently than the polymer alone. This will be applied in more detail below. The insulating sleeve has a rectangular shape in its cross section, but unlike the shape adopted by the conductive beam, it is preferred that the corners of the insulating sleeve are not substantially rounded, for example, with long and short sides of the insulating sleeve found substantially at right angles. However, there may be a small curve present, say up to about 1 mm, due to the manufacturing process and the need to apply a corona protection coating in a uniform manner to the surface of the insulating sleeve. The total width W and the height H of the insulating sleeve 36 is substantially uniform in the lateral and longitudinal directions of the composite conductor. The thickness of the wall of the sleeve TI is also uniform, except in the course of the adjacent regions 5 of the rounded corners 34 of the conducting beam 32. The thickness TI would ideally be as small as possible, consistent with the properties of suitable electrical insulation, because a thin wall for the sleeve 36, allows faster heat conduction away from the wires 32 and also allows a larger conductor beam to be included in the composite conductor for the same size general of the compound conductor. East The last point is illustrated with reference to Figure 3, which shows an alternative embodiment of the invention in which the thickness T2 of the sleeve is ^ H approximately twice the thickness TI of Figure 1. It should be noted that the number of wires 31 which can be included in the composite conductor is much smaller in Figure 3 than in Figure 2. The normal polymer sleeves for electric cables are extruded on the conductor or the conductive beam by means of an extrusion head through from the center of which runs the conductor for which the sleeve is applied. This is a well-known and understood process. A polymer sleeve having a wall thickness of about 0. lmm can be produced by known extrusion processes and it is preferred that the thickness of the polymer sleeve of the invention (excluding the corner regions) should be in a range between 0.4 to 2.00mm. For example, a typical value for TI could be about 0.5mm, preferably 0.65mm, and a typical value for T2 could be about 1mm. In order to allow the operation of the composite conductor 30 with an IT value as small as possible, the present invention provides that the polymeric material of which the sleeve 36 is made, is composed homogeneously with one or more pulverized materials, the which conduct the heat more efficiently than the polymer alone. These materials can be metal oxide, or metallic nitride fillers such as aluminum oxide or aluminum nitride. As a result, the insulating sleeve 33 not only has superior dioelectric resistance properties which allows operation at reduced thicknesses, but also has a much higher thermal conductivity and temperature resistance than known windings. The approximate *** "* volume ratio of polymer to filler material can be from 10% to 75% .To obtain eddy current losses low fH, and hence a good electrical efficiency of the composite conductor 30, in its role as a stator current winding in an electrical machine, the individual wires of conductor 31 in conductor bundle 32 are isolated from one another according to the present invention. As will be explained with more ^. In the following, this can be achieved by impregnation of the conductive bundle with a synthetic resin material such as an epoxy resin, and / or by using conductor wires that are previously provided with an insulating coating. These cables previously coated ones are routinely used in the production of windings for small electrical machines, being wound in a straight manner on the • rotor or stator. Before or during the application of a thin coating 20 to a conductive beam of the insulating sleeve the thin coating of the conductive material to the conductive beam of the insulating sleeve, for example, a graphite or silicone-based material, such as a carbon polymer filled in high temperatures, it is applied to form a corona protector in the "* •" y'f _ the inner surface of the extruded polymer, for example, at the interface between the insulating sleeve, and the conductive beam During or after the application of a thin coating of the same conductive material or a material similar to the beam The conductor of the insulating sleeve is applied to the outer surface of the insulating sleeve so that a crown protector is formed therein The outer coating is indicated by the dotted line 38 surrounding the sleeve 36 in Figure 2 (the protector inner crown is not shown.) The purpose of the conductive coating material is to balance the electrical stresses on the surface of the composite conductor during the operation of the electrical machine, and thus to avoid localized breakage of the insulation supporting the insulating sleeve 36. We have discovered that both the inner surface and the outer surface of the insulating sleeve must be provided with a cover or conductor corona protector to provide a good balance of electrical stresses on the surface of the composite conductor. A suitable thickness for the inner and outer crown coatings is in the range of approximately 0.1 to 0.3mm, preferably at the lower end of this range. As mentioned above, the polymer film of this thickness is known to be extruded and therefore the inner and outer crown protectors can be applied by means of extrusion, as will be described below. Alternatively, the inner crown protector can be applied by winding a thin ribbon of conductive material over the conductive beam before the insulating sleeve is applied thereto, and the outer crown protector • * 10 can be applied by winding a thin tape over the outside of the insulating sleeve after the insulating sleeve has been applied to the conductive bundle. Still as an additional alternative, the crown protections can be applied as a layer of paint, for example, before the application of the insulating sleeve to the conductive beam, and the latter can pass through a bath of corona protection material held in the form of a suspension or solution in a suitable liquid and after that he insulating sleeve has been applied can be passed in a similar manner through said bath. However, in said process it will be necessary to ensure that the inner crown protector has been dried or cured in a suitable manner to form a coating flexible resistant to high temperatures before The application of the insulating sleeve to the conductive bundle will occur, similarly, the outer corona protective coating must have been dried or H > cured to form a flexible coating resistant to high temperatures before it occurs. the additional handling of the composite conductor, such as the winding inside the slots of the electric machine, to facilitate the impregnation process although easy handling of the composite conductor is allowed # 10 During the process to produce the winding in the stator core, the composite conductor is impregnated before it is wound in the stator and fully cured only after it has been wound in the stator. As will be explained below, the impregnation can occur at the moment when the individual wires of the conductive material are gathered and consolidated in a conductive beam, before the application • of the insulating sleeve. Then it is preferred to cure the resin in a partial way so that the driver The composite is still flexible enough to be wound directly on the stator, with optional storage in a drum for later use. The finished stator is subjected to thermal treatment at a temperature lower than the temperature in which may deteriorate the polymer sleeve * "Filling and the crown protector, therefore completely curing the resin to make the final winding of the stator rigid." -HK With reference to figure 4, the shape is shown that the composite conductor 30 of FIG. 2 can be used to form a complete stator winding. The stator 40 of the rotary electric machine comprises a laminated steel core 42 provided with radially oriented slots extending from : fc? 10 longitudinal way of the stator. In a separate sectional view, only one of the slots 44 is illustrated. It houses a winding 46 comprising a plurality of turns or loops of the composite conductor 30. Each of the turns conveniently comprises a single length of the composite conductor, or alternatively, two or more shorter lengths of the composite conductor • can be divided to finish a round. As can be seen, the successive turns 30A, 30B, etc. of the composite conductor are in contact and radial registration with each other. It should be noted that the rectangular shape of the composite conductor minimizes the air gaps in the finished winding, making possible a geometrically accurate production of the winding without a prior formation of rigid bar conductors, such as was necessary in the prior art. The winding is #? retained in its slot 44 by a high thermal conductivity, electrically insulating the retaining wedge 46 fixed at the outer end of the slot radially. The wedge may be an extrusion comprising a filled polymer material, such as an epoxy resin, and may be conducted into the groove from the end face of the stator. A In relation to the rectangular shape of the conductive beam and the conductive sleeve, it should be noted in particular that in addition to the better packing characteristics of the composite conductor and the grooves of the machine, the extra thickness T3 -TI (figure 2) of the insulation at the corner of the conducting beam effectively reduces the electrical stress in the corner to approximately the same value as that of the flat sides of the conductor beam. Said reduction in the peak electric forces in the windings contribute to a capacity of the machine to operate at higher loads.

During the production of the stator, the inherent flexibility provided by the polymer insulating sleeve, the thin crown protector coatings, the thin conductor wires and the uncured or partly cured resin of the conductor wires allow for easy placement of the conductor in the grooves of the stator core to form a winding.

However, after the heat treatment to cure the resin (the curing being at a temperature below the temperature at which the insulating sleeve filler polymer and the corona protection coatings begin to deteriorate), the stiffness provided by the resin completely cured in the wires of the conductor 31 makes it possible for the finished winding of the stator to withstand the operating forces. It can be seen that where the conductor winding Compound 30 is not within the slots 44, it can be supported by the support rings and the packing blocks as illustrated for the distributions known in Figure 1. A possible process will be described next. to make the composite conductor by referring to Figure 5. On the left side of Figure 5, many pre-insulated wire strands 31 of the copper material are taken together with another conductive material from the storage reels (not shown) and are past through a beam forming head I to produce a conductive beam 32. Inside the head I are means well known in the cable manufacturing art, by means of which the wires 31 come together, and form a beam and the beam is twisted bodily around the center line of the beam. At the same time a. »it1 that as the wires 31 are forming a bundle, the bundle is impregnated with an epoxy resin, or a similar bond and a reinforcing agent resistant to T¡m high temperatures; alternatively, this impregnation process can be a pressure impregnation process, as is known, pressure impregnation being performed immediately after the conductive bundle has been formed either inside the head I or after it. The final process within The head I (which can be realized in practice in a separate head, not shown) is to finally form and consolidate the conductive bundle in the required rectangular shape of the present invention, passing it through a die with a suitable shape. The head I is heated so that it partially cures the resin as the conductive beam passes therethrough, thereby producing a conductive beam which has a good cohesion, yet still flexible enough to be wound in a large diameter storage drum SI, for later use. Alternatively, the partially cured beam passes directly, as indicated through a center of an annular die in the extrusion, of the head II, by means of which, the polymer film filled conductor is extruded on the outside of the bundle conductor 32, to form a first interior crown protection. Subsequently, the coated conductive beam passes through the center of another annular die in the extrusion head III, by means of which the polymer-filled insulating sleeve is extruded on the outside of the first corona coating. In an effective manner, this first crown coating thus forms a conductive coating on the inner surface of the insulating sleeve. Finally, by a process similar to that described for the head II, a second external crown protection is applied to the insulating sleeve in the extrusion head IV, thereby ending the formation of a composite conductor 30. The composite conductor 30 then it is wound on a large diameter storage drum S2 for later use. Alternatively, as indicated by the dotted arrow line, it goes directly into the additional manufacturing process to produce the windings for the electrical machines. As mentioned above, the final cure of the conductive bundles is carried out by heating, after the composite conductor has been fixed within the grooves of the winding of an electric machine, as illustrated in Figure 4.

It has been said above, that the wire strands 31 are previously insulated, meaning that within their manufacture they have been provided with a thin coating of a suitable epoxy resin, or a polymer resistant to high temperatures, as it is. known. However, as an alternative to the use of pre-insulated wire strands, it may be possible to rely on the resin impregnation process which occurs at the head I to isolate the 10 strands 31 from one another within the finished conductor bundle. This will be a matter of determination through routine experimentation. Although Figure 5 illustrates the yarns joined in a beam in a one-step process, in the In practice, due to the large number of wires required to urinate a conductive beam, the first part of the process may require a number of parallel steps in which a number of sub-beams are produced in the heads and production of corresponding beams, having been impregnated each of the bundles with the resin therein as described above, the sub-aces that are being brought together to form the final twisted ectangular conductive bundle 32. It will be evident that the previous process can be used to produce conductors compounds having transverse shapes other than rectangular, for example circular. ^ B

Claims

NOVELTY OF THE INVENTION. Having described the present invention, it is considered as a novelty and, therefore, the content of the following is claimed as property: 5 CLAIMS. 1. - A composite conductor to be used as a winding of a high voltage electrical machine, which comprises: a plurality of wires of conductive material forming a conductive beam which in its cross section is of a generally rectangular shape, being isolating the strands one from the other from the bundle, an insulating sleeve of a substantially homogeneous polymeric material surrounding the conductive bundle; The insulating sleeve also having a generally rectangular shape in its cross-section, and the polymeric material being filled with at least one electrically insulating filler material which conducts heat more efficiently than the polymer alone, and a conductive material which forms a corona protection coating on the inner and outer surface of the insulating sleeve X 2. - A composite conductor according to claim 1, wherein the shape of the corners V of the conductor bundle are substantially rectangular, having a curved shape to minimize the concentrations of electrical stress. ^^ WF ^ 3. - A composite conductor according to claim 2, wherein the dimensions of the curve of the corners of the conductor bundle are up to about 5 mm. 4. - A composite conductor according to claim 3, wherein the dimensions of the 10 curves are from 2 to 3mm. 5. - A composite conductor according to any of the preceding claims, wherein the corners of the insulating sleeve are substantially rectilinear. 6. A composite conductor according to claim 5, wherein the corners of the insulating sleeve have a curve no greater than about ^ flW? r lmm. 7. - A conductor composed in accordance with Any one of the preceding claims, in which the strands of the conductive material bundle are being twisted collectively around a longitudinal centerline of the conductive bundle, to thereby reduce parasitic eddy current losses. 25 winding. 8. - A composite conductor according to any of the preceding claims, wherein at least one insulating filler material in the sleeve ^ HB polymeric insulator is a metal oxide and / or a metal nitride. 9. A composite conductor according to any of the preceding claims, wherein the polymeric material of the magritum comprises a polymer resistant to high temperatures. 10. A composite conductor according to claim 9, wherein the polymeric material of the sleeve comprises a fluoropolymer or an aromatic polymer. 11. A composite conductor according to any of the preceding claims, wherein the conductive coating material comprises a graphite or silicone-based material. ^ B ^ 12. - A composite conductor according to claim 12, wherein the material of The conductive coating comprises a high temperature resistant polymer or paint material which has a sufficient amount of conductive material incorporated therein to produce its conductivity. 13. - A composite conductor according to claim 11 or claim 12, wherein the conductive coating material is an extruded film. 14. - A composite conductor according to any of the preceding claims, wherein the conducting wires are isolated from each other by means of an insulating coating resistant to the high temperatures applied to each wire during the manufacture of the wires before its incorporation in the conductive beam. 15. A composite conductor according to any of claims 1 to 13, wherein the conductive wires are isolated from one another by means of impregnation of the conductive bundle with an insulating material that can be cured resistant to high temperatures. 15 during the incorporation of the wires inside the conductive beam. 16.- A process to manufacture a driver ^ Composite W, which comprises the steps of: gathering a plurality of yarns of material 20 conductor in a conductive beam, and twist the threads assembled bodily around a longitudinal center line of the beam to form a twisted conductive beam, impregnate the conductive beam, with a material 25 insulation that can be cured resistant to high temperatures, impregnation occurs simultaneously with the bonding and twisting process and subsequent to it, apply a coating of conductive material to the outside of the twisted conductive bundle to form a first inner crown protection, extruding an insulating sleeve of a homogeneous polymeric material in the coating of the conductive material, having filled the polymeric material with at least one insulating filler material which conducts the heat more efficiently than the polymer alone, and apply a coating of conductive material to the outer surface of the insulating sleeve to form a second outer corona shield, wherein each wire of conductive material is provided with an insulating coating covering at least the wires prior to beam formation conductor, and coating the threads during the impregnation step. A process according to claim 16, wherein after twisting the bundle, the bundle is formed in a predetermined cross-sectional shape. 18. - A process according to claim 17, in which the previously determined cross-sectional shape is rectangular. flp 19.- A process of compliance with any 5 of claims 16 to 18, in which the impregnated conductive bundle is partially cured before the coating of conductive material is applied to the exterior of the conductive bundle. 20.- A stator for an electric machine Rotary, comprising a rolled steel core provided with a plurality of radially oriented grooves extending longitudinally from the stator, each of the grooves accommodating a winding comprising a plurality of turns of a 15 single length of the composite conductor formed in accordance with claim 1, the successive turns of material ß "being composed with one another in contact and in radial register. 21.- A stator for an electric machine Rotary, which comprises a rolled steel core provided with a plurality of radially oriented grooves extending longitudinally from the stator, each groove housing a winding comprising a plurality of turns comprising a 25 plurality of lengths of the composite conductor * • - constituted in accordance with claim 1, and wherein the successive turns of the composite conductor that are in contact and in radial registration with each other. 22. - A stator according to claim 20 and claim 21, wherein the winding is retained in its groove by high thermal conductivity, and electrically insulating retaining means fixed to the outer end of the groove in a radial manner . 23. A method for manufacturing a stator constituted in accordance with claim 21 or claim 22, wherein the conductive bundle has been impregnated with an insulating material that can be cured at high temperature, and is wound in the core of the core. stator While the insulating material can be cured at high temperature it is only partially cured, adhering support means to the composite conductor where it is supported by the stator slots, and subjecting to thermal treatment the finished stator to cure the 20 insulating material that can be cured at high temperature and produce a rigid stator winding.