CZ9902677A3 - Rotating electric machine and process for producing thereof - Google Patents

Abstract

The rotary electric machine comprises a stator (1) with a winding drawn through the slots (5) in the stator (1). The winding consists of a high voltage cable (6), wherein at least one of said slots (5) near the end surface of the stator (1) is provided with a sleeve (13, 16) disposed between the cable (6) in the housing the slot (5) and the wall of the slot (5). In the production method such rotary electrical machines are cuffs applied to the slot (5) near the end plane of the stator (1). And then the cable (6) passes through them.

Description

Rotary electric machine and method of its production

Technical field

According to a first aspect, the present invention relates to a rotary electrical machine comprising a stator with a winding extending through slots in a stator, such as a synchronous machine and a normal asynchronous machine, as well as a dual-powered machine. field and synchronous flow machines.

According to a second aspect of the invention, the present invention relates to a method of manufacturing a rotary electric machine comprising a stator with a winding extending through slots in the stator.

In this application, the terms "radial," axial, and "circumferential" refer to the direction defined with respect to the stator of the machine, unless explicitly stated otherwise. The term "cable extension" in this application refers to each individual cable length extending through the slot.

The machine is designed primarily as a generator for power plants for electricity production. The machine is also designed for high voltage applications. As used herein, "high voltage" means a voltage exceeding 10 kV. The typical operating range of this machine can be 36 to 800 kV.

BACKGROUND OF THE INVENTION

Similar machines were conventionally designed for voltage

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9 99 99 99 99 in the range of 6 → 30 kV and 30 kV was normally considered the upper limit. This generally means that the generator must be connected to the grid through a transformer that increases the voltage to the value used in the grid, ie in the range of 100 to 400 kV.

Although the predominant technology for supplying power to high-voltage transmission and distribution networks is to insert a transformer between the generator and the grid, as mentioned in the introduction, efforts are already being made to eliminate the use of the transformer by generating electricity directly at the voltage used in the grid . Such a current generator is described in US-4429244, US-4164672 and US-3743867.

According to patent application US-5036165, a conductor is known in which the insulation is provided with an inner and an outer layer of semiconducting pyrolyzed glass fiber. It is also known to use conductors in dynamoelectric machines with insulation as described, for example, in US5066881, where a layer of semiconducting pyrolyzed glass fiber is contacted with two parallel conductor rods and the insulation in the stator slots is surrounded by an outer layer of semiconductive pyrolyzed glass fiber . This semiconducting pyrolyzed material is said to be suitable because it maintains its resistance also after impregnation.

By using a high-voltage insulated electrical conductor, in the following cable only terminology, with rigid insulation similar to that used for stator winding power cables (such as XLPE cables), the machine voltage can be increased to such a level that the machine can be connected Directly to the power grid • 0 0 • 000 * »0» · · · 0 ·

0 * 0 ·· 00 0 * without intermediate transformer.

The concept usually requires the slots in which the cables are located in the stator to be deeper than conventional technologies (stronger insulation due to higher voltage and more windings in the winding). This results in new problems relating to cooling, vibration and natural frequencies in the region of the winding thread end, toothing and winding.

Securing the cable in the slot is also a problem the cable must be inserted into the slot without damaging its outer layer. The cable is exposed to currents with a frequency of 100 Hz, which causes a tendency to vibrate and, in addition to manufacturing tolerances with respect to the outside diameter, its dimension will also vary with changes in temperature (i.e., load variations).

The present invention relates to the above problems associated with avoiding damage to the outer layer of the cable during insertion into the stator slots and avoiding surface wear caused by vibrations during operation. There is a particular risk of damage at the insertion point where the cable may be damaged by the edge between the slot and the end of the stator surface. The cable may also be damaged in the slot if it is inserted obliquely or eccentrically into the slot. Also during operation, there is a risk of damage where the cable passes through the end of the stator surface. Especially if an angular error or centering error occurs, said edge may rub against the outer semiconductive layer of the cable, due to its relatively high rigidity and thereby damage it.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention to eliminate or at least reduce the risk of damage. tata of the cable where it at the end leaves the stator surface in a rotary electric machine capable of working in the high voltage range.

According to a first object of the present invention, this is accomplished by a rotary electric machine comprising a stator with a winding extending through slots in the stator, characterized in that the winding consists of a high voltage cable and further that at least one of the slots on at least one end surface of the stator is provided by a sleeve positioned between the cable and the slot, the sleeve extends axially over a short distance into the slot.

Said sleeve reduces the risk of damage if the cable winds, since the sleeve prevents the outer semiconductive layer from coming into contact with the edge of the slit wall as it is inserted, and also ensures that the cable is centered and aligned into the slit. The risk of damage during operation is also reduced since the sleeve can be made of a softer material than the stator is made and therefore acts as a pressure equalizer.

In one preferred embodiment of the invention, the sleeve is extended in the radial direction on a plurality of elongated cables, preferably all elongated cables in the slot, and has a profile corresponding to the slot profile. This provides stable and reliable securing.

The advantages of the present invention are particularly pronounced when the slots have alternating wide and narrow portions, therefore their profiles resemble a bicycle chain because the slot wall surrounds a relatively large portion of each elongated cable. A machine having such a slot profile constitutes a preferred embodiment of the invention.

It is preferred to make the cuffs of a resilient material. It should be free of oil and preferably it can be silicone • 4 4 • 4 4 * 44 4 »· 4« 4

4 4 4 rubber. The flexibility of the material greatly facilitates cable routing and utilizes the possibility of achieving pressure equalization at the outlets of the slot.

In another preferred embodiment of the invention, the sleeve is provided at the inner end of the collar projecting into the recess in the slot. This offers a simple and economical way of applying the cuff and achieves reliable hold of the cuff in the slot.

In order to facilitate cable insertion, the inner profile of the sleeve is slightly widened towards the end plane of the stator. This also contributes to the easy exit of the cable and therefore further reduces the risk of damage during operation,

In another preferred embodiment of the invention, the sleeve is arranged to seal both the cable and the wall of the slot. The sealed space is thus formed within the slot, and can be filled with a support mixture injected into the slot, which solidifies therein. In some cases, this can be an excellent way to secure the cable in the slot.

The present invention is primarily intended for use with a high voltage cable of the type consisting of a core having a plurality of braided strands, an inner semiconducting layer, an insulating layer surrounding the semiconducting layer, and finally an outer semiconducting layer surrounding the insulating layer, and whose advantages are disclosed herein. In particular, the invention relates to a cable having a diameter in the range of 20 to 200 millimeters and a conductive surface having a cross-section in the range of 80 to 3000 millimeters square.

In an embodiment of the present invention, the winding is preferably of a type that corresponds to cables with rigid extruded insulation, such as those used today for power distribution, for example XLPE cables or cables

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9 ·· 4 9 * 94 * 49 ·· 99 99 with EPR insulation. Such a cable comprises an inner conductor composed of one or more strands, an inner semiconducting layer surrounding the conductor, a solid insulating layer surrounding the above semiconductive layer, and finally an outer semiconductive layer surrounding the insulating layer. Such cables are flexible, which is an important feature since the technology for the device of the present invention is based primarily on a winding system where the winding is formed from a cable that bends during assembly. The elasticity of the XLPE cable typically corresponds to a radius of curvature of approximately 20 cm for a cable with a diameter of 30 mm, and a radius of curvature of approximately 65 cm for a cable with a diameter of 80 mm. In this application, the term "resilient" is used to refer to a condition in which the winding is resilient so that the radius of curvature is of the order of four times the cable diameter, but preferably eight to twelve times the cable diameter value.

The winding should preferably be designed to retain its properties even when bent and when subjected to thermal stresses during operation. It is important that the layers retain their adhesion to each other in this regard. The material properties of the layers are crucial here, in particular their elasticity and the relative coefficients of thermal expansion. For example, an XLPE cable consists of a low density polyethylene transverse bonding layer and a semiconducting layer consists of polyethylene mixed with carbon black and metal particles. Volume changes due to temperature fluctuations are completely absorbed as changes in cable radius, and due to comparatively small differences between the coefficients of thermal expansion of the layers due to the elasticity of these materials, radial expansion can occur without loss of adhesion between the layers.

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The combinations of materials as mentioned above should be considered as examples only. Other combinations meeting the conditions specified and also the condition of semiconductivity, ie necessity to have a resistance in the range of 10 ” ^1- ø 10 ⁶ Q.cm ¹ , for example 1-í-500

O.cm ¹ , or 10 - 200 Q.cm ^-1 , naturally also fall within the scope of the invention.

The insulating layers may consist, for example, of a rigid thermoplastic material such as low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP), polybutylene (PB), polymethyl pentene (PMP), a cross-linking such as cross-linked polyethylene (XLPE) or a rubber, such as ethylene propylene rubber (EPR) or silicone rubber.

The inner and outer semiconductive layers may be of the same material, but with particles of a conductive material such as carbon black or metal powder incorporated therein.

The mechanical properties of these materials, in particular their coefficients of thermal expansion, are influenced relatively little by whether or not the carbon black or metal powder is incorporated into them - at least to the extent required to achieve the conductivity required by the present invention. The insulating layer and semiconducting layers thus have substantially identical coefficients of thermal expansion.

Suitable polymeric materials for semiconducting layers may also be ethylene-vinyl acetate / nitrile rubber, butyl-grafted polyethylene, ethylene-butyl acrylate copolyners, and ethylene-ethyl acrylate copolymers.

Also, when different types of material are used as a basis for different layers, it is desirable for their coefficients of thermal expansion to be substantially identical. This is the case with a combination of the materials listed above.

The above materials have a relatively good elasticity, with a Young's modulus of E < 500 MPa, preferably E &lt; 200 MPa. The elasticity is sufficient for any minor differences between the coefficients of thermal expansion of the materials in the individual layers so that they can absorb the thermal expansion in the radial direction of elasticity and thus prevent any cracking or other damage and hence the possible separation of the individual layers. The material in the layers is resilient and the adhesion between the layers is at least the same size as the weakest material.

The conductivity of the two semiconducting layers is sufficient to substantially equalize the potential along each layer. The conductivity of the outer semiconducting layer is large enough to hold the electric field in the cable, but at the same time low enough to avoid significant losses due to the current induced in the longitudinal direction of the layer.

Therefore, preferably each of the two semiconducting layers essentially constitutes one equipotential surface and the winding with these layers will substantially enclose the electric field into that equipotential surface.

Of course, there is nothing to prevent one or more additional semiconductive layers from being placed in the insulating layer.

The use of such cables constitutes a preferred embodiment of the invention.

These and other preferred embodiments of the machine according to the invention are defined in the dependent claims of claim 1.

A second object of the present invention is achieved by a method of manufacturing a rotary electric machine comprising a stator with a winding extending through slots in a stator, the

The essence is that the machine winds up with a high-voltage cable and slips the sleeves into at least one of said slots on at least one end surface of the stator so that the sleeves The internal dimensions of the sleeve allow the cable to pass through, then the cable is slid into the slot through the sleeve.

According to a preferred embodiment of the method, the sleeve is lubricated with a lubricant that facilitates the passage of the cable through the sleeve and also reduces the risk of damage to the sleeve during operation.

Cuffs in accordance with a preferred embodiment of the machine are used in another preferred embodiment of the method of the invention.

List of figures in drawings

The invention will now be described in more detail with reference to the following description of a preferred embodiment, with reference to the accompanying drawings in which:

Fig. 1 shows a schematic view of a stator portion of a machine according to an embodiment of the present invention;

Fig. 2 shows a cross-section through a cable used in a machine according to the invention;

Giant. 3 shows a partial section along line III-III in FIG. 2; and

Fig. 4 shows a partial section along line IV-IV in Fig. 3.

DETAILED DESCRIPTION OF THE INVENTION

In the schematic axial view seen in FIG. 1 through a portion of the stator 1 of the machine, its rotor is

4 4 * • 4 and • 4 4 • 444 dies (extension dies can be indicated by position 2. The stator JL is usually conventionally composed of a laminated core of core plates. The figure shows a machine section corresponding to one field. externally and therefrom a plurality of teeth 4 extending radially inwardly toward the rotor, these teeth 4 are separated by slots 5 in which the stator winding 11 is located The winding cables 6 are high voltage cables and may be of the same type as the high voltage cables used. The only difference is that the outer, mechanical protective layer and the metal sheath are omitted, so the cable consists only of a conductor, an inner semiconductor layer, an insulating layer and an outer semiconductor layer. the side of the cable, which is sensitive to mechanical damage, is thus exposed.

In the figure, the cables 6 are shown schematically, only the central conductive part of the cable or winding thread is drawn. As can be seen, each slot 5 has a variable cross-section with alternately wide portions 7 ^and narrow portions 8. The broad portions 7 are substantially circular and surround the cable extending, the narrow portions EJ being intermediate portions between the broad portions 7. The narrow portions 8. serves for radial positioning of each cable extension. The cross-sections of the slit as a whole also taper radially inwards, towards the center. This is because the tension in the cable elongation is lower, the closer the cable elongations are located radially to the center as close to the stator as possible. Thus, a slim cable cable can be used here, while a thicker cable can be used further. Cables of three different dimensions are used in the illustrated example, located in three parts of the IQ NPP and 11 of the slot 5 dimensioned so that they are dimensioned such that Fe feels to fit into it.

Fig. 2 shows a cross-section through the high voltage cable 6 used according to the present invention. The high voltage cable 6 comprises a plurality of strands 31 made, for example, of copper (Cu) having a circular cross section. These strands 31 are located in the center of the cable 6. Around these strands 31 is a first semiconductor layer 32. Around this first semiconductor layer 32 is a wound insulating layer 33, made, for example, of XLPE insulation, and a second semiconducting layer 34 is wound around this insulating layer 33. Therefore, the concept of a "high voltage cable according to this application need not include a metal sheath and an outer sheath that normally surround such a cable intended for a power grid.

Giant. 3 shows a cross-section through a collar in an embodiment of the invention. The cross-section is taken along line III-III in FIG. 1 and extends briefly in the direction of one end surface of the stator 6. The outer shape 15 of the cuff corresponds to that of the slot 5, i.e. it is similar to a bicycle chain where the cut extends longitudinally through one of the wide parts of the bicycle chain, as shown in Figure 4, where the cut position in Figure 3 is also indicated . The cuff is arranged near one end surface 19 of the stator 1 and a similar cuff is located at the opposite end of the stator 6. The sleeve extends radially along the entire slot 5 and each slot is provided with such a sleeve. The axial extension of the cuff is approximately 4 cm and normally lies within an interval of 2-6 cm. The laminated core of the stator 8 is indicated by position 18 and the end plate 12 of fibrous material is located at its ends. The collar is included in the end plate 12. The recess 17 is disposed in this portion of the slot 5 extending through the end plate 12. The recess 17 extends in the wall of the slot along the entire radial length of the slot 5.

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The collar is provided with a collar 16 inserted into this recess 17. The collar lining 13 extends from the collar lining 13 towards the end surface 19 of the stator and terminates in the immediate vicinity thereof. Alternatively, the sleeve may terminate flush with the end surface of the stator, or extend briefly therefrom. The sleeve lining 13 firmly abuts the slot wall along its entire length.

The cuff interior 14 extends slightly toward the end surface 19 of the stator 11, at an angle of several degrees. The inside of the sleeve is thus slightly conical in the region around the cable extension. Where cable 6 is inserted into the sleeve, its smallest inner diameter near the collar may correspond approximately to the outer diameter of the cable 11, or may be slightly smaller to ensure good sealing and sufficient support. The cuff is made of a flexible material, suitably silicone rubber. It is important that the material does not contain any residual oil, as it could diffuse towards the outer semiconducting layer 34 of the cable and could attack and damage it. The material should also be thermally stable.

Between the placement of the cable, i.e. in the narrower portions, the sleeve has a narrower portion 20 (see FIG. 4) which fills the slot at these locations and ensures complete sealing thereof.

When the cuffs are fastened, which is done prior to winding the stator, they are pressed together and pushed axially into the slot 5 until the collar 16 of the cuff engages in a recess 17 in the slot and is thus locked in place. When the cuffs are applied, the cable can be wound and the cuffs act as a guide. The cable is thus correctly routed and is prevented from coming into contact with the edge between the slot and the end surface of the stator, thereby eliminating the risk of damage. It may be advantageous to lubricate the inside of the sleeve and to facilitate the insertion of the cable. The grease should be selected that does not damage the outer semiconducting layer of the cable. Suitable lubricants are talc and boron nitride.

The collar described above extends in a radial direction along the entire slot. Alternatively, the sleeve may be used for each cable extension and in this case cylindrical. The invention does not in any way exclude other alternatives for securing the cuff than with the collar described. For example, the sleeves may be glued to the slot, or may be fixed only by friction.

Claims (21)

PATENT CLAIMS Rotary electric machine, comprising a stator (1) with a winding extending through slots (5) in the stator (1), characterized in that the winding consists of a high voltage cable (6) and in that at least one of said slots ( 5) is provided on at least one end surface of the stator (1) with a sleeve (13, 16) positioned between the cable (6) and the slot (5), which sleeve extends axially for a short distance into the slot. Rotary electric machine according to claim 1, characterized in that said sleeve (13, 16) consists of a sleeve extending radially towards a plurality of cable extensions, preferably all cable extensions, and having a radial section corresponding to the profile slits. The rotary electrical machine of claim 1 or claim 2, wherein said sleeve comprises a plurality of sleeves, circular in radial section, each sleeve surrounding a cable extension. Rotary electric machine according to any one of claims 1 to 3, characterized in that the slot has a profile which has a radial section having wider portions (7) and narrower portions (8). Rotary electric machine according to any one of claims 1 to 4, characterized in that the sleeve (13, 16) is made of a resilient material. Rotary electric machine according to claim 5, characterized in that said material is de-oiled and is preferably a silicone rubber. · Ftft ftft ftft ftft ftft ftft ftftft ftftft ftft ·· · ftft ftft ftft ftft A rotary electrical machine according to any one of claims 1 to 6, characterized in that the sleeve (13, 16) has an axial extension of 2 + 6 cm and its axially most outer end is located immediately inside the end surface (19) of the stator. A rotary electrical machine according to any claim Claims 1 to 7, characterized in that the collar (13, 16) is provided at its axially most internal end with a collar (16) projecting into a recess (17) which extends in a radial plane in the walls of the slot. A rotary electrical machine according to any claim Claims 1 to 8, characterized in that the sleeve (13, 16) around each cable extension has an inner profile (14) with at least a diameter that corresponds to the outer diameter of the cable (6) and extends conically towards the end plane ( 19) stator. A rotary electric machine according to any one of claims 1 to 9, characterized in that the sleeve (13, 16) is positioned so as to abut and seal the space relative to the slot wall (5) and the cable (6). Rotary electric machine according to any one of claims 1 to 10, characterized in that the cable (6) is of the type consisting of a core comprising a plurality of strands (31), an inner semiconductive layer (32) surrounding the core further comprising an insulating layer (33) surrounding said semiconducting layer (32) and finally an outer semiconducting layer (34) surrounding the insulating layer (33). A rotary electrical machine according to any one of claims 1 to 11, characterized in that the high voltage cable (6) has a diameter in the range of 20 to 200 millimeters and a conductive surface with a cross-section in the range of 80 to 3000 millimeters square. tt · · · · Tt tttttt tt tt tttttt tt ttt ttt tttt tttt The rotary electrical machine of claim 11 or claim 12, wherein the winding is resilient and further wherein said layers are in contact with each other. 14. The rotary electrical machine of claim 13, wherein said layers are comprised of a material with such elasticity and such a relationship between its coefficients of thermal expansion of the materials that changes in layer volume caused by temperature changes during operation are absorbed by the elasticity of the materials. The layers retain their original adhesion to each other during temperature changes occurring during operation. Rotary electrical machine according to claim 13 or claim 14, characterized in that the materials in said layers have a high elasticity, preferably with a Young's modulus of E <500 MPa, even more preferably with E <200 MPa. A rotary electrical machine according to any one of claims 13 to 15, characterized in that the coefficients of thermal expansion of the materials in said layers are of the same size. A rotary electrical machine according to any one of claims 13 to 16, characterized in that the adhesion between the layers is at least the same size as the weakest of the materials. The rotary electrical machine of any one of claims 13 to 17, wherein each of the semiconducting layers forms one equivalential surface. 19. A method of manufacturing a rotary electric machine comprising a stator with a winding extending through slots in a stator, characterized in that the machine is equipped with a winding through the slots in the stator. 00 0 Μ · 00 00 00 wind the high voltage cable and insert the sleeves into at least one of said slots on at least one end surface of the stator so that the sleeves extend a short distance into the slot, the inner dimensions of the sleeve allow the cable to pass slips into the slot through said cuff. A method of manufacturing a rotary electric machine according to claim 19, wherein the sleeve is lubricated with a lubricant before the cable is passed through it. A method of manufacturing a rotary electric machine according to claim 19 or claim 20, wherein the applied cuff is in accordance with an embodiment defined in any one of claims 1 to 10.