GB2503480A - Wedging arrangement for electrical machine - Google Patents

Wedging arrangement for electrical machine Download PDF

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Publication number
GB2503480A
GB2503480A GB201211463A GB201211463A GB2503480A GB 2503480 A GB2503480 A GB 2503480A GB 201211463 A GB201211463 A GB 201211463A GB 201211463 A GB201211463 A GB 201211463A GB 2503480 A GB2503480 A GB 2503480A
Authority
GB
United Kingdom
Prior art keywords
component according
teeth
wedge
slots
component
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB201211463A
Other versions
GB201211463D0 (en
Inventor
Nan Qu
Christophe Perrin
Andreas Kellerer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Cummins Generator Technologies Ltd
Original Assignee
Cummins Generator Technologies Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cummins Generator Technologies Ltd filed Critical Cummins Generator Technologies Ltd
Priority to GB201211463A priority Critical patent/GB2503480A/en
Publication of GB201211463D0 publication Critical patent/GB201211463D0/en
Publication of GB2503480A publication Critical patent/GB2503480A/en
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K3/00—Details of windings
    • H02K3/46—Fastening of windings on the stator or rotor structure
    • H02K3/48—Fastening of windings on the stator or rotor structure in slots
    • H02K3/487—Slot-closing devices

Abstract

A wedging arrangement for a rotating electrical machine is disclosed. The machine comprises a plurality of teeth 16, the teeth defining a plurality of slots 18 for accommodating windings 20. The wedging arrangement includes a wedge 28 for closing the slots. The geometry of the wedge 28 is designed to interact with the teeth 16 to counteract a force which pushes adjacent teeth apart.

Description

WEDGING ARRANGEMENT FOR ELECTRICAL MACHINE
The present invention relates to a wedging arrangement for an electrical machine, and in particular a wedging arrangement for closing a slot in a stator or a rotor of a rotating electrical machine.
Rotating electrical machines generally comprise a rotor and a stator with an air gap betvveen the two. The rotor is provided with rotor windings or permanent magnets in order to develop a magnetic flux in the air gap. The stator is provided with stator windings which intersect the magnetic flux. In the case of a generator, when the rotor is rotated by a prime mover, the rotating magnetic Odd results in an electrical current flowing in the stator windings, thereby generating the electrical output. In the case of a motor, an electrical current is supplied to the stator windings and the thus generated magnetic field causes the rotor to rotate.
Stators for rotating electrical machines typically comprise a cylindrical back iron with a number of teeth extending radially inwards, the teeth defining a plurality of slots for accommodating the stator windings. During manufacture, the stator vvindings may be wound into the slots in situ, or else pre-forrned coils may be slid onto the teeth. Once the stator windings are in place, the slots maybe closed by means of wedges. WO 2006/082143 discloses wedges which may be used for this purpose. The wedges help to retain the windings within the slots, and may also be used to tailor the magnetic flux in the air gap.
In order to facilitate the manufacturing process, it has been proposed to divide the stator ofan electrical machine into a number of segments. For example, WO 01/95459 discloses a stator comprising a series of connected segments that are rotatable relative to one another. During assembly, the segments are opened up to allow coils to be fitted. The segments are then closed to form an annular stator. This can allow the coils to be fit:ed more easily.
The rotor of an electrical machine may also comprise a number of teeth which define slots for accommodating rotor windings or permanent magnets. A wedging arrangement, such as that disclosed in WO 2006/082143, may be used to close the slots in the rotor.
The teeth in the stator and/or rotor may be subject to various stresses due to the manufactu.ring process and/or operation of the electrical machine. For example, the process of inserting the vvindings and/or subsequently impregnating the vvindings may tend to push the windings against the teeth. Furthermore, in operation, the windings may be subject to thermal expansion, which may also tend to force the teeth apart. In addition, known wedging arrangements tend to push against the teeth, thereby exacerbating the problem.
It is usually desirable for the ends of the teeth to be relatively narrow in order to maximise the nLmber of windings and provide slots with parallel sides. However, this can make the teeth vulnerable to stresses which are applied to them. If the stator is divided into segments, this may cause further weakness, in particular if the divisions occur through the teeth. As a consequence, the stresses which are applied to the teeth could potentially cause damage. If fragments of the teeth should become loose, this could also damage other parts of the machine.
In order to overcome the above problem the teeth could be made thicker. Hovvever this might limit the amount of magnetic flux vvhich could be produced by the vvindings, thereby reducing the efficiency of the machine.
According to a first aspect of the present invention there is provided a rotating electrical machine comprising a plurality of teeth, the teeth defining a plurality of slots, and a wedging arrangement for closing the slots, wherein the wedging arrangement is arranged to counteract a force which pushes adjacent teeth apart.
By providing a wedging arrangement which is arranged to counteract a force which pushes adjacent teeth apart, the teeth can be made more stable thereby reducing the chance of damage or allowing the slots to be wider than vvould othervvise be the case.
Preferably the component further comprises vvindings in the slots, and the wedging arrangement is arranged to retain the windings in the slots. This can help to prevent migration of the windings out of the slots. The windings may be stator windings or rotor windings. Afternatively, the wedge may be used to help retain permanent magnets, for example in the rotor of a permanent magnet machine.
Preferably the vvedging arrangement comprises a wedge vvhich spans two adjacent teeth.
Preferably the wedge is arranged such that a force which pushes adjacent teeth apart is counteracted through tension in the wedge. The wedge may comprise a non-magnetic material, such as plastic or a non-magnetic metal, in order not to influence the magnetic flux in the air gap. Alternatively, the wedge may at least partially consist of a magnetic material, for example as described in WO 2006/082143.
Preferably the teeth comprise recesses which interlock with the wedge. This can allow the wedge to counteract a force which pushes adjacent teeth apart through tension in the wedge.
The teeth may comprise lips which partially close the recesses. For example, the lips may have a hook-shaped cross-section (which may be an axial cross-section). Preferably the lips present a surface inside the recesses which face away from the slots. This can allow the wedge to interlock with the recesses in such a way that a force which pushes adjacent teeth apart can be counteracted through tension in the vvedge.
The recesses are preferably located at the open end of the teeth, and preferably open into the slots. Preferably the recesses run in an axial direction through the teeth. This can allow a vvedge to be slid into the recesses in an axial direction once the windings are in place.
Alternatively, the wedge could be arranged to be clipped into place in a radial direction.
Preferably the vvedge comprises a lip at either side (e.g. in a circumferential direction), each of which interlocks with a recess in a tooth. For example, the lips may have a hook-shaped cross-section to enable them to interlock with the recesses. Preferably the lips present a surface vvhich faces tovvards the slots. This can allow the vvedge to interlock with the recesses in such a way that a force which pushes adjacent teeth apart can be counteracted through tension in the wedge.
It is generally desirable for the aft gap between the stator and the rotor to have a substantially constant width. In order to achieve this, the vvedge may comprise a truck which is thicker than the lips. The truck is preferably the part of the wedge which is located between the adjacent teeth. This can allow the wedge to have a surface which lies substantially in the same curved plane as an end surface ofa tooth. Por example, the surface of the wedge and the end surface of the tooth may both lie substantially on he surface ofa notional cylinder with its centre at the axis of the machine. The surface of the wedge and the end surface of the tooth may themselves be flat or curved.
In a conventional wedging arrangement, if the wedge is deformed by a radial force, such as through pressure from the windings, this will tend to force the teeth apart, thereby exacerbating the stresses on the teeth. However, in an embodiment of the present invention, the wedging arrangement is arranged such that deformation of the wedge by a radial force causes the teeth to be pulled together. This may be achieved through interaction of the recesses in the teeth and the lips on the wedge.
In one embodiment the corn ponent is a stator of the rotating electrical machine. The stator may be divided into segments, in order to facilitate its manufacture. In another err bodiment the component is a rotor of the rotating electrical machine.
According to another aspect of the invention there is provided a rotating electrical machine comprising a component in any of the forms described above.
According to another aspect of the invention there is provided a method of assembling a component for a rotating electrical machine, the component comprising a plurality of teeth defining a plurality of slots, the method comprising inserting windings into the slots, and closing the slots with a wedging arrangement, wherein the wedging arrangement counteracts a force which pushes adjacent teeth apart.
Features of one aspect of the invention may be applied to any other aspect. Any of the apparatus features may be provided as method features and vice versa.
Preferred embodiments of the invention will now be described, purely by way of example, with reference to the accompanying drawings, in which: Figure 1 is an axia cross-section through part ofa stator for an eectrica rriachine, showing known vvedging arrangement; Figure 2 is an axia cross-section tHrough part ofa stator with a wedging arrangement in an embodiment of the present invention; S Figure 3 sHows the wedging arrangement of Figure 2 in more detaiL and Figure 4 shows diagrammaticaHy a sef-Iocking mechanism of the wedging arrangement of Figure 3.
Figure 1 is an axia cross-section tHrougH part ofa stator for an eectrica macHine, sHowing a known vvedging arrangement. Referring to Figure 1, the stator comprises a back iron 2, with a puraUty of teetH 4 extending radiaUy inwards. THe teetH 4 define a pHraUty ofsots 6 for accommodating stator windings 8. The stator back iron and teeth are typicaHy formed from a number of stacked aminations.
n the arrangement of Figure 1, the radiaHy innermost ends of the teeth 4 have V-shaped grooves loon either side. THe grooves run in an axia direction tHrougH tHe machine.
During manufacture, the stator windings Bare inserted into the slots 6 from the inside of the stator. Once the windings 8 have been inserted into the sots, the sots are dosed by means of wedges 12. The wedges 12 Have tapered ends, wHicH allow tHem to be slid in an axia direction into the grooves 10 of two adjacent teeth. The wedges 12 hep to retain the windings 8 within the sots 6 during operation of the macHine.
n known electrica machine designs, the teeth may be subject to a variety of different cads. For exarrpe, the windings may press against the teetH, causing two adjacent teeth to be pushed apart. fthe windings are su.bsequenty impregnated with a resin, this may aso tend to force the teeth apart. FurtHermore, during operation of the machine tHe windings usuaUy Heat up, and thermal expansion of the windings may aso cause a force to be appUed to the teeth.
n some electrica machine designs, the stator of tHe electrical macHine is divided into segments. The division may be through the teeth, or through the sots. The geometry of tHe amination sHeets in sucH a design may be probernatic, because tHe ends of tHe teeth Have a widtH which is smaU in comparison to their length. These could resuft in the tooth
S
being broken and causing damage to other components. H practice, this may mean making the teeth thicker than desired, leaving less space for the windings and reducing the arnou.nt of magnetic flux that can be produced.
S Wedging arrangements may also be used in rotors of rotating eectrical machines. In a rotor, in addition to other stresses, centrifuga force may result in a high force being appNed indirecty to the teeth.
Figure 2 is an axia cross-section througH part ofa stator with a wedging arrangement in an embodiment oldie present invention. Referring to Figure 2, tHe stator comprises a back iron 14, with a pluraUty of teeth 16 extending radiaHy inwards. The stator back iron 14 and teeth 16 are formed from a number of stacked aminations. The teeth 16 define a pluraNty of sots 18 for accommodating stator windings 20. A wedging arrangement is used to dose the sot once the windings are in pace. The wedging arrangement comprises a wedge 28 which spans two adjacent teeth 16. The wedge is formed from a non-magnetic rnateria such as plastic, or a non-magnetic metaL Figure 3 shovvs the wedging arrangement of Figure 2 in more detaiL Referring to Figure 3, each tooth 16 has a recess 22 on either side. The recesses 22 run axiaHy through the machine (into the plane of the paper in Figure 3). The recesses are located towards the open ends of the teeth, and open into the sot 18. The teeth 16 have curved Ups 24, which curl around so as to present a surface 26 inside the recess which faces away frorri the inside of the slot 18.
As shown in Figure 3, a wedge 28 spans two adjacent teeth 16 in order to close the slot 18.
The wedge 28 has a curved Up 30 on either side. Each Up 30 curs around into a corresonding recess 22 in the tooth, so as to inteHock wit the recess in a "yin yang" arrangement. The truck of the wedge is thicker than the Ups, in order to aUow the vvedge to present a surface to the air gap which is substantiaHy coHinear with end surfaces of the teeth.
n the arrangement of Figures 2 and 3, if the teeth are subjected to a force which tends to push them apart, this will be countered by tension in the wedge. Thus the wedging arrangement of Figures 2 and 3 NW counteract forces which push the teeth apart.
Furthermore, if the wedge 28is subjected to a radial force from inside the slot then deformation of thewedge will lead to the teeth being pulled together, thereby providing a self-locking mechanism.
S Figure 4 shows diagrammatically the self-locking mechanism of the wedging arrangement of Figure 3. As shown in Figure 4, the wedge 28 may be subject to a radial force F vvhich pushes out of the slot and against the vvedge. The force may come, for example, through expansion of the windings or, in the case of a rotor, through centrifugal force. As shovvn in Figure 4, the outward force will tend to deform the wedge. However, deformation of the wedge vvill tend to pull the teeth together, due to the geometry of the wedging a rra ngement.
Thus the wedging arrangement of the present embodiment will tend to lock the teeth when forces are applied to the teeth and/or wedge due to operation of the machine. The shape of the wedge is such that, when such forces are applied, it creates a force on the teeth in opposite direction. A part of this force may already be created when adding an expandable material below the wedge and/or when impregnating the vvindings witn resin. Thus the total forces applied to the teeth may be reduced. This can reduce the likelihood of damage to the teeth, and/or allow teeth with a smaller vvidth to be used.
Although embodiments of the invention have been described with reference to specific examples, it will be appreciated That alternative arrangements may be provided. For example, the recesses could be provided on the outer surface of the teeth, rather than inside the slots, and this may allow a greater slot density to be achieved, possibly at the expense of less resilience to radial forces. Furthermore, the yin yang" arrangement of the lips on the teeth and vvedge may be in the opposite sense. Other arrangements vvill be apparent to the skilled person. Although a wedging arrangement has been described with reference the stator of a rotating electrical machine, the vvedging arrangement could also be used vvith a rotor.

Claims (25)

  1. CLAIMS1. A component for a rotatng electrica machine, the component comprising a pluraUty of teeth, the teeth defining a pkiraUty of slots, and a wedging arrangerrient for dosing the slots, wherein the wedging arrangement is arranged to counteract a force which pushes adjacent teeth apart.
  2. 2. A component according to caim 1, further comprising windings in the sots, wherein the wedging arrangement is arranged to retain the windings in the slots.
  3. 3. A component according to caim 1 or 2, wherein the wedging arrangement comprises a wedge which spans two adjacent teeth.
  4. 4. A component according to dairn 3, wHerein the wedge is arranged sucH that a force which pushes adjacent teeth apart is counteracted througH tension in the wedge.
  5. 5. A component according to dairn 3 or 4, wherein the wedge comprises a non-magnetic material.
  6. 6. A component according to any of claims 3 to 5, wherein the teeth comprise recesses vvhich interock with the wedge.
  7. 7. A component according to cairr 6, wherein the teeth comprise Ups which partiaHy dose the recesses.
  8. 8. A component according to daim 7, wherein the lips have a hook-shaped cross-section.
  9. 9. A component according to cairr 7 orS, wherein the Ups present a surface inside tHe recesses wHicH faces away from the sot.
  10. 10. A component according to any of claims 6 to 9, wherein the recesses are ocated at the open end of the teetH.
  11. 11. A component according to any of claims 6 to 10, wherein the recesses open into the slots.
  12. 12. A component according to any of claims 6 to 11, wherein the recesses run in an axial direction through the teeth.
  13. 13. A component according to any of claims 3 to 12, wherein the wedge comprises a lip at either side, each ofvvhich interlocks vvitb a recess in a tooth.
  14. 14. A component according to claim 13, wherein the lips have a hook-shaped cross-section.
  15. 15. A component according to claim 13 or 14, wherein the lips present a surface which faces towards the slots.
  16. 16. A component according to any of claims 13 to 15, wherein the wedge comprises a truck which is thicker than the lips.
  17. 17. A component according to any of claims 3 to 16, wherein the wedge comprises a surface which lies substantially in the same curved plane as an end surface ofa tooth.
  18. 18. A component according to any of the preceding claims, wherein the wedging arrangement is arranged such that deformation of the wedge by a radial force causes the teeth to be pulled together.
  19. 19. A component according to any of the preceding claims, wherein the component is a stator of the rotating electrical machine.
  20. 20. A component according to claim 19, wherein the stator is divided into segments.
  21. 21. A component according to any of claims 1 to 18, wherein the component is a rotor of the rotating electrical machine. a
  22. 22. A rotating electrical machine comprising a component according to any of the preceding claims.
  23. 23. A method of assembling a component for a rotating electrical machine, the S component comprising a plurality of teeth defining a plurality of slots, the method comprising inserting windings into the slots, and closing the slots with a wedging arrangement, wherein the wedging arrangement counteracts a force which pushes adjacent teeth apart.
  24. 24. A wedging arrangement for a rotating electrical machine substantially as described herein with reference to and as illustrated in Figures 2 to 4 of the accompanying drawings.
  25. 25. A method of assembling a component fora rotating electrical machine substantially as described herein with reference to the accompanying drawings.
GB201211463A 2012-06-28 2012-06-28 Wedging arrangement for electrical machine Withdrawn GB2503480A (en)

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GB201211463A GB2503480A (en) 2012-06-28 2012-06-28 Wedging arrangement for electrical machine

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Application Number Priority Date Filing Date Title
GB201211463A GB2503480A (en) 2012-06-28 2012-06-28 Wedging arrangement for electrical machine

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GB201211463D0 GB201211463D0 (en) 2012-08-08
GB2503480A true GB2503480A (en) 2014-01-01

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014158316A (en) * 2013-02-14 2014-08-28 Toshiba Mitsubishi-Electric Industrial System Corp Stator of rotary electric machine
DE102017118792A1 (en) * 2017-08-17 2019-02-21 Wobben Properties Gmbh Wind turbine generator as well as slot wedge for it and wind turbine with it
DE102019111336A1 (en) * 2019-05-02 2020-11-05 Festool Gmbh Drive motor with a slot cover
US11489395B2 (en) 2018-02-13 2022-11-01 Rolls-Royce Deutschland Ltd & Co Kg Electric machine having a plurality of closing devices for closing respective intermediate spaces in relation to an air gap, and production method
US11489396B2 (en) 2018-11-15 2022-11-01 Black 7 Decker Inc. Winding retention insert for a brushless motor
DE102022107828A1 (en) 2022-04-01 2023-10-05 Bayerische Motoren Werke Aktiengesellschaft Rotor body with cover slide to cover a rotor groove

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1377038A (en) * 1973-05-31 1974-12-11 Goblin Ltd B V C Wedge assembly for retaining in position the electrical windings of a rotor
JPS5752338A (en) * 1980-09-16 1982-03-27 Toshiba Corp Rotary electrodynamic machine
GB2386259A (en) * 2002-03-08 2003-09-10 Rolls Royce Plc A liner for a fluid-cooled stator
DE102010039381A1 (en) * 2010-08-17 2012-02-23 Siemens Aktiengesellschaft Electric machine e.g. direct-driven wind generator, for use in ore mill, has active component whose full depth teeth and half depth teeth are mechanically connected with each other by anchor element

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1377038A (en) * 1973-05-31 1974-12-11 Goblin Ltd B V C Wedge assembly for retaining in position the electrical windings of a rotor
JPS5752338A (en) * 1980-09-16 1982-03-27 Toshiba Corp Rotary electrodynamic machine
GB2386259A (en) * 2002-03-08 2003-09-10 Rolls Royce Plc A liner for a fluid-cooled stator
DE102010039381A1 (en) * 2010-08-17 2012-02-23 Siemens Aktiengesellschaft Electric machine e.g. direct-driven wind generator, for use in ore mill, has active component whose full depth teeth and half depth teeth are mechanically connected with each other by anchor element

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014158316A (en) * 2013-02-14 2014-08-28 Toshiba Mitsubishi-Electric Industrial System Corp Stator of rotary electric machine
DE102017118792A1 (en) * 2017-08-17 2019-02-21 Wobben Properties Gmbh Wind turbine generator as well as slot wedge for it and wind turbine with it
US11489395B2 (en) 2018-02-13 2022-11-01 Rolls-Royce Deutschland Ltd & Co Kg Electric machine having a plurality of closing devices for closing respective intermediate spaces in relation to an air gap, and production method
US11489396B2 (en) 2018-11-15 2022-11-01 Black 7 Decker Inc. Winding retention insert for a brushless motor
DE102019111336A1 (en) * 2019-05-02 2020-11-05 Festool Gmbh Drive motor with a slot cover
US11894747B2 (en) 2019-05-02 2024-02-06 Festool Gmbh Drive motor with a groove cover
DE102022107828A1 (en) 2022-04-01 2023-10-05 Bayerische Motoren Werke Aktiengesellschaft Rotor body with cover slide to cover a rotor groove

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