System for transferring power between a rotating element and a fixed element

Abstract

A system for transferring current between a rotating element and a fixed element, comprising—a support in the general shape of a sheet (10) comprising a conductive portion (11) electrically connected to the fixed element, —a brush holder (20) mounted on the support (10) and supporting a brush (30) that is pushed into contact against the rotating element, —electrical connection means (42) for connecting the conductive portion (11) of the support to a cable (40) that is joined to the brush (30), wherein a resistive element (12) is situated between the brush (30) and the conductive portion (11) of the support (10) and prevents current from flowing directly between the conductive portion and the brush.

Claims

1. A current transfer system between a rotating element and a fixed element, the rotating element being moved with a movement of rotation with respect to the fixed element, said transfer system comprising a support having an overall shape of a plate on the periphery of the axis of rotation of the rotating element, comprising a conductive portion electrically connected to one out of the fixed element and the rotating element, at least one brush-holder mounted on and supported by, or integrated into, the support, and shaped to hold at least one conductive sliding contact element, the conductive sliding contact element, supported by the brush-holder and configured to be pushed into contact against the other out of the fixed element and the rotating element, a resistance element located between this conductive sliding contact element and the conductive portion of the support when the conductive sliding contact element is pushed into contact, to limit the passage of current directly between the conductive portion and the conductive sliding contact element, means for electric connection of the conductive portion of the support to a flexible rigidly connected to the conductive sliding contact element for the transfer of current between this conductive portion and the conductive sliding contact element.

2. The system according to claim 1, wherein the resistance element comprises an insulating element located between this conductive sliding contact element and the conductive portion of the support, when the conductive sliding contact element is supported by the brush-holder and pushed into contact, and the system is shaped so that the insulating element thus prevents the passage of current directly between the conductive portion and the conductive sliding contact element.

3. The system according to claim 1, further comprising at least one sensor capable of measuring a parameter value characterizing the operation of the conductive sliding contact element.

4. The system according to claim 3, further comprising at least two conductive linear elements electrically connecting the sensor to processing means in order to exchange measurements or controls, wherein these conductive linear elements are at least partly embedded in resistant or insulating material.

5. The system according to claim 3, further comprising processing means in communication with a ventilation device and with the sensor(s), wherein said processing means are arranged to control ventilation according to the measured values coming from the sensor(s).

6. The system according to claim 1, wherein the conductive portion comprises a conductive plate of the busbar type.

7. The system according to claim 6, wherein the resistance element is obtained by applying onto the conductive plate a resistant material having a resistivity of at least 0.1 ohm-meters.

8. The system according to claim 7, wherein the brush-holder defines at least one lug extending from a wall of the brush-holder towards the outside of the brush-holder, in a plane closer to the support than the location of the carbon brush, said location being defined by the walls of the brush-holder, and wherein said lug is laminated in the resistant or insulating material.

9. The system according to claim 7, wherein the resistance element is obtained by coating and/or overmolding the conductive plate with the resistant material.

10. The system according to claim 1, wherein at least a part of the brush-holder is fastened in a non-removable manner onto the support.

11. The system according to claim 1, wherein the brush-holder is made from a single metal sheet.

12. An assembly comprising a rotating element, a fixed element, and the transfer system according to claim 1.

13. A method of transferring electric current in rotating electrical machine used in industry or in the wind power industry, comprising operating the assembly according to claim 12.

14. A method for manufacturing a current transfer system between a rotating element and a fixed element, the rotating element being moved with a movement of rotation with respect to the fixed element, the method comprising providing a support having an overall shape of a plate, configured to be located on the periphery of the axis of rotation of the rotating element, comprising a conductive portion, the conductive portion being configured to be electrically connected to one out of the fixed element and the rotating element, providing at least one brush-holder installed on or integrated into the support, shaped to hold a conductive sliding contact element, installing the conductive sliding contact element in the brush-holder, this element being configured to be pushed into contact against the other out of the fixed element or the rotating element, providing a resistance element located between the conductive sliding contact element when pushed into contact and the conductive portion of the support, providing means for electric connection of the conductive portion to a flexible rigidly connected to the conductive sliding contact element for the transfer of current between the conductive plate and the conductive sliding contact element.

15. The method according to claim 14, further comprising applying a resistant material onto the conductive portion and/or onto the brush-holder in such a way as to form the resistance element.

Description

(1) The invention will be better described in reference to the following drawings, which show non-limiting embodiments given as examples.

(2) FIG. 1 schematically shows a wind turbine according to an embodiment of the invention.

(3) FIG. 2 shows an example of a transfer system of the type known from the prior art.

(4) FIG. 3A is a cross-sectional and schematic view of an example of a transfer system according to an embodiment of the invention, in which the insulating layer is relatively localized and the brush-holder is screwed onto the insulating layer, in a reversible manner.

(5) FIG. 3B is a cross-sectional and schematic view of another example of a transfer system according to an embodiment of the invention.

(6) FIG. 3C is a perspective and schematic view of yet another example of a transfer system according to an embodiment of the invention.

(7) FIG. 4 is a perspective view of an example of a transfer system according to an embodiment of the invention, in which the insulating layer covers the entirety of the conductive plate and the brush-holder laminated in the insulating layer, the insulating layer not being shown in this drawing.

(8) FIG. 5 is a cross-sectional and schematic view of an example of an assembly according to yet another embodiment of the invention.

(9) FIGS. 6A, 6B and 6C illustrate alternative embodiments, in which sensors and processing means are provided on the conductive plate.

(10) Identical references can designate elements that are identical or similar, in their form or their function, from one drawing to another.

(11) In reference to FIG. 1, a wind turbine 100 comprises a tower 101, a nacelle 112 and blades 102 rigidly connected to a “low-speed” shaft 103.

(12) A multiplier 104 allows to convert the movement of rotation of the low-speed shaft 103 into a faster movement of a “high-speed” shaft 105.

(13) A generator 115 allows to generate current from the movement of this high-speed shaft 105.

(14) This generator 115 is a rotating electric machine comprising a rotor, a stator and carbon brushes. It will be described in more detail in reference to FIG. 3.

(15) FIG. 2 illustrates an example of a generator of the type known from the prior art.

(16) In reference to this drawing, conductive plates 201 in the shape of a circle arc are disposed around an axis of rotation (D). These conductive plates are rigidly connected to a stator not shown.

(17) Brush-holders 202 are fastened onto the conductive plates 201. Each brush-holder defines a cage to receive a carbon brush 230 as well as a spring means 203 for pushing this carbon brush into contact against rings of the rotating element 204 of the generator. The shaft of the rotor is not shown in this FIG. 2.

(18) Flexibles 205 fastened to the carbon brush by one end have their other end connected to connections 206 in electric contact with the plate element 201.

(19) However, the brush-holders 202 are themselves conductive so that the current produced can circulate from a carbon brush towards the corresponding plate 201 via the corresponding brush-holder, without passing through the flexibles 205.

(20) A rupture of a flexible 205 thus may not be detected. Also, an imbalance in the collection of current from one carbon brush to another may not be detected.

(21) In reference to FIG. 3A, a support is provided having the overall shape of a plate 10, here seen in a cross-section. This support 10 comprises a conductive plate 11, of the busbar type, and over a part of which a layer of insulating material 12 has been applied.

(22) A brush-holder 20 has been fastened onto the layer 12, here with screws 21.

(23) This brush-holder 20 is made from a metal sheet. This sheet is folded or drawn in such a way as to define with the insulating layer 12 a housing to receive a carbon brush 30.

(24) A spring not shown allows to push the carbon brush 30 in a direction normal to the plane of the sheet, towards for example a ring.

(25) In a manner known per se, the carbon brush is connected to a flexible 40.

(26) This flexible 40 is itself connected to a terminal 41 which is fastened by a threaded rod-nut system 42 into the conductive plate 11.

(27) It can be noted that the screws 21 used to fasten the brush-holder 20 to the insulating layer 12 are received in an orifice 18 passing through the conductive portion 11. An insert 17 made of insulating material covers the walls of the orifice 18: the carbon brush 30 is only in contact with the conductive plate 11 via the flexible 40.

(28) In the case of screws sufficiently long for a part to protrude from the side opposite to the brush-holder side, it is possible to cover the ends of the screws with an insulant of the washer, plug, or other type.

(29) Alternatively or in addition, the screws themselves could be made from an insulating material or covered with insulating material. PTFE (polytetrafluoroethylene) or other can for example be used.

(30) The insulating material of the insert 17 can for example be a composite of epoxy resin reinforced with glass fibers. The same material can be chosen for the insulating layer 12, or not.

(31) The current collected by the carbon brush 30 thus arrives in the conductive plate 11 via the flexible 40.

(32) In this example, the insulating layer can be made for example from a composite of epoxy resin reinforced with glass fibers.

(33) In an alternative embodiment not shown, instead of the insulating layer 12, a resistant layer can be provided, for example obtained by applying a paint onto a part of the surface of the plate 11.

(34) In this example, the insulating layer 12 extends over only a part of the surface of the conductive plate 11, this part corresponding to the location of the brush-holder 20.

(35) In the example of FIG. 3B, insulating material 12 has been applied onto the entire surface of the conductive plate 11, with the exception of the contacts stud 42′.

(36) The brush-holder 20 defines a cage with four sides, and comprises two lugs 29 in a plane offset with respect to the location of the carbon brush and embedded in the insulating material 12, these lugs not being in direct electric contact with the conductive plate 11.

(37) The insulating layer 12 is thus located between the graphite carbon brush 30 and the conductive plate 11, and is shaped to prevent any passage of current between the carbon brush 30 and the conductive plate 11 other than via the flexible 40 connected to the contact stud 42′.

(38) In this FIG. 3B, the spring means for pushing the carbon brush towards the rotating element have not been shown either.

(39) In reference to FIG. 3C, the spring means are not shown either, but on the contrary, it can be seen how the flexible 40 is fastened to the carbon brush 30.

(40) In this embodiment the support 10 comprises a conductive plate 11 in the shape of a circle arc, adjoining a part of the insulating portion 12. The insulating material has been applied against an edge 13 of the conductive plate 11, forming an insulating part 12.

(41) In this example, the brush-holder has been obtained by drawing a sheet and by fastening lugs 29 onto the insulating portion 12 by any suitable means, for example by lamination, by gluing or other.

(42) The carbon brush 30 is in contact with the insulating material 12, which prevents any transfer of current between the carbon brush 30 and the conductive plate 11 other than via a flexible not shown.

(43) In an embodiment that is not shown, the support can comprise an insulating plate and a conductive portion consisting of a track made of metal mounted on this insulating plate or embedded in the material of this insulating plate.

(44) In the embodiment of FIG. 4, a support 410 having an overall shape of a plate comprising a metal plate 411 of the busbar type, at least one face of which (that visible in FIG. 4) is entirely covered with insulating material not shown in this FIG. 4, is provided.

(45) This support 401 is concave on the side of the rotor 404, in such a way as to partly surround the rotor.

(46) A mounting rod 450 allows to fasten the support 410 onto a fixed part not shown.

(47) An electric connection bar 451 allows to electrically connect the support 411 to power-transfer flexibles (not shown) installed on a fixed part of the nacelle.

(48) Two brush-holders 420 are fastened in a non-removable manner onto the support 410. These brush-holders 420 each define a cage for receiving a carbon brush 430 and further comprise a pressure system 450 for receiving a spring not shown, this spring allowing to push the corresponding carbon brush against the rotor 404.

(49) Each brush-holder 420 comprises two lugs 422 each extending from a wall 423 of the brush-holder towards the outside of the brush-holder, in a plane offset with respect to the location of the carbon brush.

(50) Each lug 422 has been laminated in the insulating layer not shown, thus allowing to fasten the brush-holders 420 in a non-removable manner onto the support 410. The lamination is carried out while taking care to avoid any contact between the lugs and the busbar 411, thus avoiding creating a path for the passage of the current collected from the rotor 404 other than that passing through the flexibles 440.

(51) Alternatively, in an embodiment not shown, the orifices of the lugs 422 could for example be used to fasten these lugs by screwing against inserts covering the walls of corresponding orifices, like in the embodiment of FIG. 3A.

(52) A connection means, for example an electric connection rod 441, passing through the insulating layer not shown and in contact with the conductive plate 411 allows to ensure the passage of the current from the flexible 440 towards the conductive plate 411.

(53) The electric connection rod 441 can have a shape known per se. For example, this rod can comprise a threaded rod, a nut not shown and optionally a support 442: a terminal of the end of the flexible 440 can be inserted around the rod and compressed between the nut and the support 442 (or between the nut and the insulating layer).

(54) A current sensor 460 is installed near the rod 441.

(55) This current sensor can be embedded in the layer of insulating material not shown.

(56) This sensor can measure the intensity of the current passing through the flexible or the rod 441, that is to say because of the insulation of the carbon brush carried out, the totality of the current collected by this carbon brush.

(57) In the embodiment of FIG. 5, a support having an overall shape of a plate 610 comprises a busbar 611 coated with an insulating layer 612.

(58) A carbon brush 630 is received in a brush-holder 620 comprising spring means not shown for pushing the carbon brush 630 into contact against a rotating element 604.

(59) Several rotating elements are provided, even though only one 604 is shown here, the rotating elements being separated from each other by insulating discs, one of which 680 is shown.

(60) In this embodiment, the brush-holder 620 is made in two parts 621, 622 that can be assembled to one another in a reversible manner.

(61) More precisely, the brush-holder 620 comprises a removable part 621 comprising the cage intended to receive the carbon brush 630, and an adapter part 622 fastened in a non-removable manner onto the support 610.

(62) For example, the removable part can comprise the spring means exerting a pressure to push the carbon brush 630 into contact against the rotating element 604.

(63) For example, the connection of the flexible not shown, one end of which is in contact with the carbon brush 630, to the conductive plate can be carried out by a connection means mounted on the brush-holder.

(64) This connection means not shown, for example a rod system, can be mounted on the adapter part 622 and pass through the insulating layer 612 until contact with the busbar 611.

(65) The connection means can for example be screwed, clipped, or other onto the adapter part 622.

(66) Advantageously, a plug-set (or “plug-set” in English) system allowing to connect/disconnect the carbon brushes while the machine is under load, in particular in the case of a use in the synchronous generators of hydroelectric power plants, can be provided.

(67) In reference to FIGS. 6A, 6B and 6C, supports 710, 710′, 710″ are shown seen from the side opposite to the side corresponding to the face on which the brush-holders are mounted. The brush-holders are not therefore visible in these figures.

(68) The supports 710, 710′, 710″ can define orifices 763, 763′, 763″, the edges and the inner walls of which can be covered with insulating material, for the passage of wires connected to sensors installed on the face of the support on which the brush-holders are mounted. A washer made of insulating material received in an orifice can for example be provided.

(69) It is also possible to arrange flexible passages directly in insulating material.

(70) These sensors on the brush-holder side can for example comprise temperature sensors, for example sensors measuring the temperature in the layer of insulating material coating the busbar.

(71) It is possible to estimate the temperature in the brush-holder according to the values measured by these sensors and according to thermal conductivity values stored in a database.

(72) The references 761, 761′, 761″ designate sensors mounted on the face opposite to the face supporting the brush-holders, thus visible in these drawings, for example current sensors mounted around connection rods ensuring the transfer of the current collected.

(73) It is advantageous to thus install sensors on the face opposite to the face supporting the brush-holders, relatively uncluttered, which can facilitate maintenance.

(74) Conductive linear elements 762, 762′, 762″, here flexible, for example of the ribbon type (762, 762′), are connected to the sensors 761, 761′, 761″ and to the sensors on the non-visible face, while thus passing through the orifices 763, 763′, 763″.

(75) The conductive linear elements 762, 762′, 762″ can be embedded in the insulating material coating the busbar.

(76) In the embodiment of FIG. 6A, processing means in the form of a flexible printed circuit 764 or PCB (for Printed Circuit Board) laminated in the insulating material coating the two faces of the busbar is provided.

(77) It is advantageous to provide at least one sensor on the same face as at least one processing element (processor or other), thus allowing to avoid piercing the conductive plate.

(78) This can allow to obtain better distributed field lines, which limits heating. Moreover, this can allow to have a better creepage (“creepage” in English) distance.

(79) The components are thus embedded in the insulating material, for example PEN.

(80) In the embodiment of FIG. 6B, processing means in the form of a PCB of the card type, rigid, received in a housing 764′ welded or screwed to the busbar, is provided.

(81) The conductive linear elements 762′ are flexible (ribbon).

(82) In the embodiment of FIG. 6C, the conductive linear elements are conventional electric wires or flexibles, also embedded in the insulating material. Grooves can be provided in the support to receive these wires 762″.

(83) These wires 762″ are connected to a printed circuit (processing means) received in a housing 765 mounted on the insulating layer, for example via screws.

(84) In all cases, a connection of the CAN (for “Controller Area Network”) bus type can further be provided.