Classifications

• • 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
  • H02K15/02—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies
  • H02K15/024—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines of stator or rotor bodies with slots
• • 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

Definitions

• the present invention relates to a method for manufacturing a stator for a rotating electric machine for high voltage in accordance with the preamble to claim 1, a stator manufactured in accordance with the method defined in claim 2 and a device for prestressmg and securing tightening means in accordance with the preamble to claim 11.
• the invention also relates to a use of said device in accordance with claim 26, yet a method for manufacturing a stator in accordance with the preamble to claim 27 and a stator in accordance with the preamble to claim 28.
• the invention is particularly suitable for use with rotating electric machines for high voltages including a stator, a rotor and at least one winding, in which bolts of preferably glass fibre are used to hold together segments, preferably of electrical sheet, forming the stator of the machine .
• the present invention therefore also relates to a rotating electric machine in accordance with the preamble to claim 29.
• the rotating electric machines referred to in this context include synchronous machines, principally used as generators for connection to distribution ana transmission networks, generally termed power networks.
• the synchronous machines are also used as motors and for phase compensation and voltage control, in that case as open-circuited machines.
• This technical area also includes normal asynchronous machines, double-fed machines, alternating current machines, asynchronous static current converter cascades, external pole machines and synchronous flux machines . These machines are intended for use at high voltages, by which is meant here electric voltages in excess of 10 kV.
• a typical operating range for such a rotating machine may be 36 to 800 kV, preferably 72.5 - 800 kV .
• Rotating electric machines have conventionally been designed for voltages in the range 6-30 kV, and 30 kV has normally been considered to be an upper limit. This generally means that a generator must be connected to the power network via a transformer which steps up the voltage to the level of the network, i.e. in the range of approximately 130-400 kV.
• stator frame In conventional types of rotating electric machines the stator frame often consists of a welded steel plate construction.
• stator core also known as the laminated core
• the laminated core is normally made of so called elec- trical sheet, preferably 0.35-0.50 mm, divided into stacks having an axial length of approximately 50 mm, separated from each other by spacers forming ventilation ducts 5 to 15 mm wide.
• each laminated stack is formed by adding sheet segments, punched to a suitable size, together to form a first layer. The sheet segments in each subsequent layer are placed with overlap on the segments in the preceding layer.
• the laminated part of a stator core has been formed when all the layers, possibly with ventilation ducts between them, have been placed.
• the parts and spacers are held together with existing axial clamping means in the form of pressure brackets pressed by means of pressure de- vices against pressure rings, fingers or segments.
• the device is a tighten- ing means including axially running bolts which have preferably been electrically insulated or are provided with an insulating material, which are drawn through axial holes through the stator teeth and possibly through the stator yoke.
• the bolts run in the stator teeth or in the stator yoke along the entire axial length of the stator, and are provided with locking devices .
• the locking device may consist of a nut at one end and the head of the bolt at the other end.
• the tightening means is made in the form of a rod at least partially threaded internally and/or externally, in which case the locking devices may consist of nuts at both ends, for instance. It is also possible for the rod to be hollow, in which case it may also be used as a combined cooling duct.
• the object of the present invention is to solve the problems mentioned above. This object is achieved by means of the method according to the preamble of claim 1 with the features defined in the characterizing part of the claim. The object is also achieved with a stator in accordance with claim 2 which is characterized in that it is manufactured in accordance with the metnod defined in claim 1. The method is thus characterized in that
• a tightening means in the form of an at least partially threaded rod, is placed in a recess, preferably through-running, intended therefor m the stator core and in that a nut pertaining to the tightening means is screwed loosely onto the threaded end of the rod, which end protrudes out of the stator core,
• the tightening means is prestressed by the tension means acting upon the threaded ro ⁇ with a predetermined tensile force with the aid of a prestressing means
• the winding is achieved with an electric conductor including at least one current-carrying conductor, and also including a first layer with semiconducting properties surrounding the current-carrying conductor, a solid insulating layer surrounding said first layer, and a second layer with semiconducting properties surrounding the insulating layer.
• the method described has the advantage that it solves the problem of prestressing the glass fibre bolts, thus enabling their use in the present context.
• the windings, in the method and stator according to the invention are preferably of a type corresponding to cables having solid, extruded insulation, of a type now used for power distribution, such as XLPE- cables or cables with EPR-msulation .
• a cable comprises an inner conductor composed of one or more strand parts, an inner semiconducting layer surrounding the conductor, a solid insulating layer surrounding this and an outer semiconducting layer surrounding the insulating layer.
• Such cables are flexible, which is an important property in this context since the technology for the method and stator according to the invention is based primarily on winding systems in which the winding is formed from cable which is bent during assembly.
• the flexibility of an XLPE-cable normally 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.
• the term "flexible" is used to indicate that the winding is flexible down to a radius of curvature in the order of four times the cable diameter, preferably eight to twelve times the cable diameter .
• the winding should be constructed to retain its properties even when it is bent and when it is subjected to thermal or mechanical stress during operation. It is vital that the layers retain their adhesion to each other in this context.
• the material properties of the layers are decisive here, particularly their elasticity and relative coefficients of thermal expansion.
• the insulating layer consists of cross-linked, low-density polyethylene
• the semiconducting layers consist of polyethylene with soot and metal particles mixed in.
• the insulating layer may consist, for example, of a solid thermoplastic material such as low-density polyethyl- ene (LDPE), high-density polyethylene (HDPE), polypropylene (PP) , polybutylene (PB), polymethyl pentene (“TPX”), cross- linked materials such as cross-linked polyethylene (XLPE) , or rubber such as ethylene propylene rubber (EPR) or silicon rubber.
• LDPE low-density polyethyl- ene
• HDPE high-density polyethylene
• PP polypropylene
• PB polybutylene
• TPX polymethyl pentene
• XLPE cross- linked materials
• XLPE cross-linked polyethylene
• EPR ethylene propylene rubber
• the first, inner, and the second, outer, semiconducting layers may be of the same basic material but with particles of conducting material such as soot or metal powder mixed in.
• the mechanical properties of these materials, particularly their coefficients of thermal expansion, are affected relatively little by whether soot or metal powder is mixed in or not - at least in the proportions required to achieve the conductivity necessary according to the mven- tion.
• the insulating layer and the semiconducting layers thus have substantially the same coefficients of thermal expansion .
• EVA/NBR Ethylene-vmyl-acetate copolymers/nitrile rubber
• EBA ethylene-butyl-acrylate copolymers
• EBA ethylene-ethyl-acrylate copolymers
• ESA EAA may also constitute suitable polymers for the semiconducting layers .
• the materials listed above have relatively good elasticity, with an E-modulus of E ⁇ 500 MPa, preferably ⁇ 200 MPa.
• the elasticity is sufficient for any minor differences between the coefficients of thermal expansion for the materials in the layers to be absorbed in the radial direction of the elasticity so that no cracks appear, or any other damage, and so that the layers are not released from each other.
• the material in the layers is elastic, and the adhesion between the layers is at least of the same magnitude as in the weakest of the materials.
• 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 sufficiently high to enclose the electrical field within the cable, but sufficiently low not to give rise to significant losses due to currents induced in the longitudinal direction of the layer.
• each of the two semiconducting layers essentially constitutes one equipotential surface, and these layers will substantially enclose the electrical field between them.
• Another object of the present invention is therefore to reduce the time required for prestressing and securing said bolts in the stator of a rotating electric machine. This object is achieved with a device for prestressing and securing tightening means as described m the preamble of claim 11, with the addition of the advantageous features defined m the characterizing part of the claim.
• a tension means with a tension rod which is screwed onto a tightening means in the form of a rod, provided at least partially with threading and with a nut screwed on, and also including rotating means to impart a rotary movement to the tension rod in order to screw on or unscrew the tension rod from the tightening means and subsequently transfer a rotary movement to the nut, means for connecting said rotating means with the tension means, means for prestressing the tightening means by affecting the tension rod to a pre-set position, and means for tightening the nut in the prestressed position of the tightening means, the method described above can be performed mechanically in an extremely efficient manner.
• This device is thus not limited to any particular area of application but can be used in any context demanding prestressing of tightening means, preferably in the form of bolts.
• tightening means is used in the claims and this may refer to a bolt, for instance, but similar means such as a threaded pin are also possible as mentioned previously. Neither is the device in any way limited to the prestressing of glass fibre bolts. Any other type of bolt is possible. However, it is particularly advantageous for pre- stressing bolts of various types of materials that are difficult to prestress, of which glass fibre may be mentioned as an example. Other examples may be non-magnetic polymer materials or carbon fibre.
• the high-voltage electric conductor may be manufactured in several advantageous ways.
• the insulated conductor is a cable, prefera- bly a high-voltage cable.
• the conductor or cable is flexible. It is important for the cable to flexible or bendable if it is to be used as a winding.
• the first semiconducting layer is at substan- tially the same potential as the current-carrying conductor.
• the second semiconducting layer is preferably arranged so that it constitutes a substantially equipotential surface surrounding the current-carrying conductor (s) and the insulating layer. It is also connected to a predetermined poten- tial, preferably earth potential.
• at least two adjacent layers have substantially equally large coefficients of thermal expansion and the current-carrying conductor may include a number of strand parts, only a few of the strand parts not being msu- lated from each other.
• each of the three layers i.e. the two semiconducting layers and the insulating layer, may be firmly joined to the adjacent layer along substantially its entire contact surface.
• the layers are arranged to adhere to each other even when the insulated conductor or cable is bent.
• it preferably has a diameter within the range 20-250 mm and a conducting area in the range 80-3000 mm 2 .
• the rotation means include a rotatable holder means and drive means for rotation of the holder means.
• the rotatable holder means is preferably formed as a sleeve, generally in the form of a chuck, but other forms, known per se, for the holder means are also conceivable.
• the drive means preferably include a drive motor, preferably electric, for instance in the form of a drilling machine, suitably hand-held, and a transmission means, where the transmission means may include a cogged belt transmission.
• other types of transmission means may also be suitable, e.g. V- belt or chain transmission.
• the means for connecting the rotating means with the tension means constitutes a rotatable sleeve provided with splines, termed a connecting sleeve.
• the sleeve is provided internally with splines for cooperation with corresponding external splines arranged on the tension rod.
• the sleeve is also provided externally with splines for cooperation with corresponding internal splines on the holder means.
• Other types of rotatable connecting means are feasible.
• the means for prestressing include a hydraulic cylinder and a hydraulic pump, the hydraulic cylinder being designed to influence the tension rod with a tensile force so that the tension rod and the bolt joined thereto are tightened to a pre-set, or in some way predetermined, position.
• Other prestressing means are naturally also feasible, e.g. equivalent pneumatic means, a linear motor, or any other means able to execute a linear movement.
• the device is also characterized in that the means for tightening the nut include the holder means and means for detachable connection of the holder means with the nut, preferably in the form of a carrier means.
• the device includes a stand on which the rotating means are supported.
• This stand is in turn sup- ported on at least one, preferably two, pillars and is able to move axially along the pillars in resilient manner.
• the arrangement with the stand and pillars improves the stability of the device and facilitates exactitude when fitting the tension rod over the bolt, thereby enabling the work of prestressing and securing to be performed more quickly.
• the pillars may also be provided with a cross piece on which the tension means, spline sleeve and prestressing means are supported. To further improve stability the pillars may be attached on one or more support rails bearing onto the gen- erator or any other arrangement where the device is being used .
• the objects of the present invention stated above can also be achieved by the use of a device in accordance with any of the claims relating to a device, when manufac- turing a stator in accordance with any of the claims relating to a stator. They can also be achieved by a method characterized in that the stator is manufactured with the aid of said device or by a stator characterized in that it is manufactured by means of said device, and also by a rotating electric machine characterized in that it includes a stator as defined in any of the claims relating to a stator.
• Figure 1 shows a device in accordance with the present invention, in a front view and partly in section along the line A-A in Figure 4, in a first position
• Figure 2 illustrates a device in accordance with the present invention, in a side view and partly in section along the line A-A n Figure 4, in a second position
• Figure 3 illustrates a device in accordance with the present invention, m a front view and partly in section along the line A-A in Figure 4, in a third position
• Figure 4 shows the device in accordance with the present invention schematically, seen from above and partly in section, immediately above the wheels in the transmission means
• Figure 5 shows a sector of a stator with the bolts outlined in accordance with the invention
• Figure 6 shows a section through an insulated electric conductor suitable for use as winding.
• the device illustrated in Figure 1 is an embodiment by way of example of a device in accordance with the present invention, which is particularly suitable for prestressing and securing bolts used to hold together the electrical sheet segments in the stator of a generator.
• the bolt 2 is here a threaded rod 3 provided with a nut 4.
• the bolt pref- erably made of glass fibre, is loosely fitted in the stator 47 and is provided with a nut screwed on.
• the nut is preferably screwed on with the aid of a drilling machine with a special sleeve to fit these nuts.
• the device includes a tension means 1 with a tension rod 6 provided externally with splines 7. An actuator means 33 is provi ⁇ ed at its upper end. The tension rod is provided at its lower end, facing the bolt, with an internally threaded recess 8.
• the device also includes prestressing means 30 including a hydraulic cylinder 31 provided with a hollow shaft 32 and a hydraulic pump (not shown) .
• the hydraulic pump is preferably electrically operated at constant pressure, e.g. a wing pump.
• the tension rod 6 is arranged in the hollow shaft 32.
• the device also includes rotating means 9 to impart a rotary movement to the tension rod.
• the rotating means include drive means in the form of a drive motor 22 and preferably also a transmission means 24, as well as a rotatable holder means 10 applied on the tension rod.
• the transmission means is a cogged belt transmission means, which is described in more detail with . reference to Figure 4.
• the holder means consists of a rotatable sleeve in the form of a chuck.
• the drive motor may also consist of a drilling machine.
• the tension rod 6 and chuck 10 are joined together by means of a rotatable connecting means 15.
• this connecting means 15 consists of a sleeve 16, said connecting sleeve being provided internally with splines 17 and externally with splines 18.
• the internal splines 17 cooperate with corresponding external splines 7 on the tension rod 6.
• Said external splines 18 cooperate with corresponding internal splines 11 (only illustrated in Figure 4) on the chuck 10.
• Other types of rotatable connecting means are of course possible.
• the device also includes means 35 for tightening the nut after the prestressing operation has been performed.
• the chuck 10 is thus provided with slots 12 which include screw- driver slots in the embodiment shown.
• a carrier means 36 is arranged on the bolt 2, the carrier means having a central aperture which is fitted over the bolt, and with slots, e.g. in the form of screw-driver slots, in the end facing the nut, for cooperation with corresponding slots arranged in the nut.
• the carrier means is also provided with slots, preferably screw-driver slots 38, corresponding to the slots in the chuck, for cooperation therewith. Also other means for connecting the chuck to the carrier means are feasible.
• the carrier means in which case the chuck 10 is instead provided at its lower end facing the bolt, with means for cooperating di- rectly with the nut 4 on the bolt.
• the reason a carrier means is required in the case illustrated is that the nut shall be screwed down into the stator 47 and there is not sufficient space for the chuck.
• the drive motor, transmission means and chuck are supported on a stand 40.
• This stand is axially movable, spring-supported and runs on two pillars 43, 44 with the aid of ball bushings or the like. These pillars 43, 44 are connected by a cross piece 45, on which the hydraulic cylinder 31 is mounted.
• the splined sleeve 16 is fitted onto the underside of the cross piece. It is fitted with ball bearings 19 so that the sleeve can rotate but is simultaneously fixed axially to the cross piece.
• the chuck 10 is supported on the stand by means of ball bearings 13.
• the device is advantageously provided with two sup- port rails 46 with the aid of which the device is supported against the generator.
• the pillars 43, 44 are arranged on these rails.
• FIG. 1 shows the two support rails 46 and the pillars 43, 44 .
• This figure also shows the cogged belt transmission 24 with two wheels 26, 27, and the cogged belt 25.
• the rotary movement is transmitted from the drive motor 22 with the aid of the cogged belt transmission, the wheel 26 being arranged on the outgoing shaft of the motor, via the cogged belt 25 to the wheel 27, the latter being ar- ranged on and driving the chuck 10.
• Figure 4 also shows the internal splines 11 on the chuck 10 cooperating with the external splines 18 of the sleeve 16, as well as the internal splines 17 cooperating with the external splines 7 of the tension rod 6.
• Figure 5 shows a sector 50 of a stator in accordance with the invention.
• the stator sector includes six stator teeth 51, four of which are provided respectively with a pressure finger 52 in the example illustrated.
• the winding 53 is arranged in the space 54 shaped like a bicycle chain.
• the bolts 57 are arranged in the stator teeth 51 and also in the stator yoke 58. Cooling ducts 59 are also shown in the figure.
• FIG. 6 finally, shows a cross section through a cable which is particularly suitable for use as winding m the stator in accordance with the present invention.
• the cable 60 includes at least one current-carrying conductor 61, surrounded by a first semiconducting layer 62.
• An insulating layer 63 is arranged surrounding this first semiconducting layer and a second semiconducting layer 64 is arranged surrounding the insulating layer.
• the electric conductor 61 may consist of a number of strand parts 65.
• the three layers are made so that they adhere to each other even when the cable is bent.
• the cable shown is flexible and this property is retained throughout its service life.
• the cable illustrated also differs from conventional high-voltage cable in that the outer mechanically protective sheath and the metal screen normally surrounding such a cable do not have to be included.
• the function of the device will now be described with reference to Figure 1, Figure 2 and Figure 3 in which various stages of the working operation are illustrated.
• the glass fibre bolts are presumed to be loosely mounted in the stator with the nuts screwed on.
• the nuts may be screwed on, for instance, using a drilling machine with a special sleeve to fit these nuts.
• the device in accordance with the invention is placed so that the tension means 1 with the tension rod 6 is situated exactly over a glass fibre bolt 2, as illustrated in Figure 1. In this position the tension rod is lowered with the aid of the actuator 33 arranged at the upper end of the tension rod, and the drive motor is started.
• the tension rod is provided with a recess 8 with internal threading at the end facing the bolt, this will engage with the threaded rod 3 of the bolt 2.
• the bolt may have a recess with internal threading and the tension rod have corresponding external threading for cooperation.
• the rotary movement from the rotating chuck is transmitted to the tension rod by means of the splined sleeve 16 and corresponding splines in chuck and tension rod.
• the drive motor is stopped.
• Prestressing of the glass fibre bolt is now effected by the hydraulic pump pressing out the hydraulic cylinder 31, thereby influencing the tension rod 6 and the bolt 2 (the threaded rod 3) connected thereto, with a predetermined tensile force.
• the hydraulic pump retains its pressure until the nut has been finally tightened.

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

Applications Claiming Priority (3)

Publications (1)

Family

ID=20408586

Family Applications (1)

Country Status (6)

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Family Cites Families (3)

• 1997
  • 1997-10-13 SE SE9703720A patent/SE512915C2/sv not_active IP Right Cessation
• 1998
  • 1998-10-12 EP EP98950561A patent/EP1023761A1/de not_active Withdrawn
  • 1998-10-12 JP JP2000516424A patent/JP2001520497A/ja active Pending
  • 1998-10-12 WO PCT/SE1998/001834 patent/WO1999019970A1/en not_active Application Discontinuation
  • 1998-10-12 AU AU96569/98A patent/AU9656998A/en not_active Abandoned
  • 1998-10-13 ZA ZA989330A patent/ZA989330B/xx unknown

Non-Patent Citations (1)

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