EP3010094A1

EP3010094A1 - A brush device for an electrical connection

Info

Publication number: EP3010094A1
Application number: EP14189393.3A
Authority: EP
Inventors: Immanuel Safari-Zadeh
Original assignee: Alstom Renewable Technologies Wind BV
Current assignee: GE Renewable Technologies Wind BV
Priority date: 2014-10-17
Filing date: 2014-10-17
Publication date: 2016-04-20

Abstract

The invention relates to a brush device (1) in an electrical machine for an electrical connection or signal connection. Disclosed is a brush device (1) for an electrical connection of an electric machine or rotary transformer, whereby the brush device (1) comprises interwoven filaments (2) for current and/or signal transmission between at least a rotary side and a stationary side.

Description

TECHNICAL FIELD

The present disclosure relates to a brush device in an electrical machine for an electrical connection or signal connection.
The electric machine is in particular a rotating electric machine such as a synchronous generator to be connected to a gas, wind or steam turbine (turbogenerator) or a synchronous generator to be connected to a hydro turbine (hydro generator) or an asynchronous generator or a synchronous or asynchronous electric motor or also other types of electric machines.

BACKGROUND

The high voltages generated in electric machines for power supply are transferred from the rotating rotor to the fixed stator by brushes in a stationary configuration. This means a transmission between a stationary side and a rotary side is performed. The brushes are fabricated from sintered graphite as a block and are commonly installed with a mounting at the fixed stator. The threads of the brush are commonly arranged in rows next to each other. There are several issues with common brushes, as the mechanical and the electrical wear, electrical conductivity, and failure by cracks in the brushes.

SUMMARY

It is an object of the invention to provide a compact and cost-efficient brush device with extended life cycle to transmit electric current or signals.
This object is achieved with the features according to the independent claims. Disclosed is a brush device for an electrical connection in an electric machine or rotary transformer and the use of interwoven filaments in a brush device.
Further examples of the invention are described in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages will be more apparent from the description of a preferred but non-exclusive embodiment of the brush device, illustrated by way of non-limiting example in the accompanying drawings, in which:

Fig. 1: shows a perspective view of a cut part of an exemplary brush from interwoven filaments for use in a brush device according to an example of the invention,
Fig. 2: shows a schematic cross-sectional side view of a brush device with a rotary side at the left with a first rotating part, a second rotating part, and a conducting part, and a fixed stationary side at the right with a housing with a cooling duct encompassing interwoven filaments, and with two cooling connectors and one humidity connector connected to the housing,
Fig. 3: shows a schematic cross-sectional side view of a further example of the stationary side of a brush device with an electric connection, a lifting device for lifting and pushing the brush from interwoven filaments to the rotary side, and two cooling connectors for cooling the interwoven filaments,
Fig. 4: shows a schematic cross-sectional side view of the stationary side of a brush device similar to Fig. 3 with a different structure,
Fig. 5: shows a schematic cross-sectional side view of a further example of a brush device with a rotary side rotating in operation at the right and left, and a fixed stationary side in the middle,
Fig. 6: shows a schematic top view of a rotatable ring, a rotary part, in the middle, a stationary ring around housing interwoven filaments, the stationary ring being divided in three segments, and several lifting devices equipped with positioning sensors and pressure sensors, whereby each of the three segments is movable outwards by the lifting devices.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

With reference to the figures, these show a bar from interwoven filaments and brush devices according to examples of the invention, wherein like reference numerals designate identical or corresponding parts throughout the several views.
Fig. 1 shows a perspective view of a cut part of a brush from interwoven filaments 2 to be applied to a brush device 1 according to the invention. The brush is made from filaments, cords, threads, yarns or fibres out of carbon entirely or in-part. In the disclosure the term filaments is used for this structure of filaments, cords, threads, yarns or fibres throughout. A multitude of filaments is woven or interwoven to an essentially rectangular bar. The high number of filaments is interwoven to a plurality of strings, which strings are woven to the bar, referred to as interwoven filaments 2 here. The manufacturing method of the interwoven filaments 2 from graphite, polytetrafluorethylene, carbon nano-tubes, or graphene may be explained as woven, twisted, and/or loomed leading to a configuration of the filaments as shown in Fig. 1. Nevertheless, for the sake of ease the material used is referred to as interwoven filaments 2 throughout the disclosure. The interwoven filaments 2 have properties as a low friction with a high electrical and thermal conductance.
Fig. 2 shows a schematic cross-section of a brush device 1 according to an example of the invention. The brush device 1 comprises the components as described in the following. Main components are the woven flexible filaments 2 as described above which are on the stationary side of the electric machine at the right in this example and as such not rotatable. The interwoven filaments 2 are housed in a housing 18 which encompasses the interwoven filaments 2 at three sides in this example. The housing 18 is fabricated from metal and has a cavity inside which captures a substantial volume of the housing 18. The cavity inside the housing 18 is a cooling duct 19 which is designed for the flow through of a cooling means. Fixtures 22 are arranged between the housing 18 and the interwoven filaments 2 to hold these together. The fixtures 22 can be connecting pins, screws, or other connecting means or even be replaced by adhesives. The cooling duct 19 is fed with cooling means by two cooling connectors 4 here. The cooling connectors 4 comprise ducts or hoses for the flow through of the cooling means, for example a cooling fluid, as water or oil. The ducts or hoses reach through the housing 18 into the cooling duct 19. One cooling connector 4 serves hereby as the inlet, the other cooling connector serves as the outlet, the inlets and outlets can also be designed as coaxial (not shown here) or have one or a multitude of spiral paths for including the fluid. In the middle of Fig. 2 a humidity connector 5 reaches through the walls of the housing 18 and also through the cooling duct 19. The walls of the duct or hose of this humidity connector 5 are tight so no cooling means leaks into the humidity connector 5 from there. The humidity connector 5 projects into the interwoven filaments 2 and dispenses a fluid to the interwoven filaments 2, for example water or water with additives. The additives used in the fluid can contain graphene and/or carbon nano-tube lubricants or additives for example. The injection of fluid into the interwoven filaments 2 can be done in different ways. The humidity connector 5 can eject drops of fluids, a flow of fluid within a short period, impulsive or constantly, or evaporated fluid. The vaporization of the fluid can be done by a cold vaporization. The fluid to be ejected into the interwoven filaments 2 can be charged with nano-materials as lubricants and/or replacement of dispensed brush material of the interwoven filaments 2. The effect of this dispensing by the humidity connector 5 is that a wished humidity within the interwoven filaments 2 can be adjusted and the friction coefficient is diminished. The humidity connector 5 is equipped with a controlled valve to dispense a specific mass of liquid in a specific time to this end. The humidity of the interwoven filaments 2 plays an essential role in its properties, the electrical conductivity and in particular in avoiding wear and aging of the material. The cooling connectors 4 and the humidity connector 5 are connected to a controller 7 or computer which comprises a microcontroller to steer the release of cooling fluid and of water or additives added to water, respectively. The signal connections are depicted in a schematic way by dashed lines. Dependent on the cooling need at the interwoven filaments 2 the controller 7 controls the mass of cooling fluid through the cooling connectors 4. The cooling connectors 4 and/or the humidity connector 5 can also be designed as stand-alone systems not steered by the controller 7. As stand-alone systems the cooling connectors 4 and/or the humidity connector 5 dispense a specific amount per time of cooling fluid or water for moistening the interwoven filaments 2, respectively. In operation the rotor at the rotary side rotates with high velocities, correspondingly the heat generation at the material near the surface is high. The interwoven filaments 2 touching the rotating rotor parts are affected by this heating. The cooling fluid or water provided by the cooling connectors 4 reduces the temperature at the interwoven filaments 2. Similarly, dependent on the humidity present in the interwoven filaments 2 and the humidity difference to an optimum value stored in the controller 7 the controller 7 prompts a valve at the humidity connector 5 or the humidity connectors 5 to open and dispense a specific mass of water or water with additives to the interwoven filaments 2. The thus dispensed cooling means distributes within the interwoven filaments 2 and the humidity of the interwoven filaments 2 is adjusted to a certain optimum level regarding the application.
At the open side of the interwoven filaments 2 not encompassed by the housing 18 the interwoven filaments 2 abut a conducting part 16 which is fabricated from a metal, e.g. copper or brass. The abrasion or material removed by erosion and friction from the interwoven filaments 2 and the conducting part 16 is absorbed by a suction device (not shown). The conducting part 16 is a ring, in this example having a rectangular cross-section with or without a corrugated, zigzag, curved, concave, or convex shape to increase the contact surface area at the face directed to the conducting part 16. The surface shaped in such a manner serves for enhancing the current densities to be transmitted. The conducting part 16 is at the rotary side of the electric machine which means it is rotated in operation of the machine. The ring of the conducting part 16 is changeable in maintenance mode. The replacement is necessary as result of unavoidable wear at the conducting part 16 at which the interwoven filaments 2 slides and current transfer occurs along in operation. The metal rotary parts on the rotary side can possess cooling ducts or channels (not depicted here) in order to reduce the friction caused dissipation heat. The interwoven filaments 2 thus fulfil the function of common brushes in the stationary configuration of electric machines. The conducting part 16 is connected to a second rotating part 14, hereby connected by means of screw projecting axially through the second rotating part 14 and the conducting part 16. The fixation can be designed heat-shrunk, dove-tailed, or by a rack and pinion connection. The smaller down side of the second rotating part 14 is welded to a first rotating part 11. The first rotating part 11 is a part of the rotor which projects perpendicular to the second rotating part 14 and the conducting part 16. The first rotating part 11 abuts a protective wall 21 along its length. The protective wall 21 projects horizontally along the brush device 1 and is also rotatable. The brush device 1 can comprise a sensor device 30 which takes different measured values. In this example the sensor device 30 is accommodated in the housing 18 enclosed by the interwoven filaments 2. Further, the sensor device 30 can comprise a temperature sensor for measuring the temperature at the interwoven filaments 2. The temperature sensor can be optical, e.g. infrared, and be positioned anywhere outside of the cavity. Further, the sensor device 30 comprises a moisture meter for measuring the moisture or humidity at the interwoven filaments 2. A displacement sensor is connected to the lifting device 6 outside of the housing 18. The positioning data of the displacement sensor is relevant for the performance assessment of the brush device 1. A second sensor device 30 is shown in Fig. 2 attached to the outside of the housing 18. This second sensor device 30 can also comprise a temperature sensor and further a displacement sensor. The displacement sensor measures the acceleration from which the vibrations at this position can be deduced. Thereby the operator can observe the grade of the mechanical connection of the brush device 1 with the data available at the controller 7. The measurement data is transmitted to the controller 7 or computer and analysed there. The measurement data is compared to stored data, whereas a specific difference between measured and stored data lets the controller 7 take effect on the corresponding quantity. Correspondingly, the data can be transmitted remotely to any place, for example via the world wide web. When the moisture measurement results in a low humidity of the interwoven filaments 2 the controller 7 acts on the humidity connector 5 to inject a specific amount of liquid to the interwoven filaments 2. When the temperature measurement results in a high temperature of the interwoven filaments 2 the controller 7 acts on the cooling connector 4 to enhance the amount of cooling liquid to stream into the cooling duct 19. Controlling these quantities leads to a humidity and temperature at the interwoven filaments 2 near to the optimum values. The measuring of pressure, passing current amplitude, velocity of the rotary part, temperature, and cooling rate provides the exact data for calculation of loss of the brush device 1 for any operating condition. The loss referred to consists of friction losses and conducting losses within the interwoven filaments 2 and at the interfaces or contact surfaces. An optimum matched operating condition can be obtained, which may guarantee an extended life cycle. The controller 7 controls the variables comprising the temperature, humidity, and contact surface pressure in a way to minimize the total loss by means of interaction and controlling the sensors 30, cooling connector 4, humidity connector 5, and lifting device 6 as described. This measure makes the planning of maintenance of the brush device 1 easier and more foreseeable. Next to the current transmission the brush device 1 performs a low current signal transmission between the rotary side and the stationary side. The signal transmission can be performed solely without a high power transmission. Thereby the brush device 1 with interwoven filaments 2 is applicable as a signal transmission. Moreover, the brush device 1 can provide a connection for earthing or grounding functions.
Fig. 3 shows a schematic side view of a different configuration of a part of the brush device 1. Here, again the left side is the rotary side with protection walls 21 to shield the separate components from each other. The same function is fulfilled by the intermediate parts 23 which serve as an stationary extension of the rotary protection walls 21 but which are arranged on the stationary side of the electrical machine. In Fig. 3 the interwoven filaments 2 are on the rotary side rotating in operation of the machine in the contrary to the example of Fig. 1. The interwoven filaments 2 are fixed to conductive parts 16 each, which are thus also at the rotary side. In this example the interwoven filaments 2 are not housed. Instead, at the top and at the bottom of the interwoven filaments 2 bearings 26 are arranged. In particular, the interwoven filaments 2 are pressed between the bearings 28 with a high pressure to reduce the cross-section. A compression of the interwoven filaments 2 by 2-20% of the volume can be reached. This measure has also the advantage that the density of the interwoven filaments 2 is enhanced leading to a higher electrical and thermal conductivity of the interwoven filaments 2. The bearings 28 are fixed to the protection walls 21 and to the conducting parts 16. At the right side which is again the stationary side of the electrical machine a brush connector 20 is arranged at each of the three components, an electrical connector 3, the lifting device 6, and the cooling connector 4. The electrical connector 3, the lifting device 6, and the cooling connector 4 have a data connection with the controller 7, shown schematically by dashed lines, and exchange data with the controller 7. The brush connector 20 below has a cavity similar to the housing 18 in the example of Fig. 1. This cavity serves as a cooling duct 19 for cooling the interwoven filaments 2 via the walls of the brush connector 20 as described above. Accordingly, the brush connector 20 has two cooling connectors 4 as inlet and outlet of a cooling means or fluid to the cooling duct 19. The component in the middle of Fig. 3 has also a stationary brush connector 20 which is connected to the lifting device 6. The lifting device 6 is designed to lift or press the brush connector 20 to the interwoven filaments 2. In one mode the lifting device 6 can lift or remove the brush connector 20 such that no contact exists between these parts. In the perspective of Fig. 3 the movement of the lifting device 6 is from left to right and vice versa. The removal is relevant for maintenance of the electric machine, for example for replacing the interwoven filaments 2. In another mode the lifting device 6 adjusts the pressure exerted by the brush connector 20 to the interwoven filaments 2. A brush connector 20 transmits the current via the interwoven filaments 2 to the stator. An electrical connector 3 is fixed to the brush connector 20. This component complies with the common function of transmission of energy from the rotary to the stationary side. By means of attaching the sensor devices 30 to the lifting devices 6, hereby the sensor device 30 contains several displacement sensors, the wear rate of each segment of the interwoven filaments 2 can be measured and any unexpected out-phasing be avoided. This provides an enhanced maintenance and serviceability of the brush device 1. The wear rate of the interwoven filaments 2 is recorded in a memory of the controller 7. The records of the wear of the interwoven filaments 2 in operation in the course of time can be accessed by an operator or by a software in the controller 7 or computer.
Fig. 4 shows essential parts of a brush device 1 similar to Fig. 3. The data connection to the controller 7 is not shown here. In Fig. 4 the structure is different compared to Fig. 3. Nevertheless, the functions of the three components shown are the same. The rotation of the rotary part at the left and below occurs again in the direction into the image plane. The three components described above are arranged at the top and constitute the stator part or stationary side of the electric machine. The protection walls 21 between the three components, electrical connector 3, cooling connector 4, humidity connector 5, are rotatable as under Fig. 3, which are here bended upright.
Fig. 5 shows a schematic view in cross-section of essential parts of an example of the invention. Here, at the rotary side the rotary parts are a shaft 29 at the left and the interwoven filaments 2 fixed to the conducting part 16 at the right. The stationary parts on the stationary side are the brush connector 20 which encloses a cooling duct 19. The stationary cooling connector 4 projects through the wall of the brush connector 20. The cooling connector 4 fills in and fills out a cooling liquid into and from the cooling duct 19 to cool the interwoven filaments 2 via the walls of the brush connector 20. Also shown is a coupler 17 adjacent to the shaft 29 and the brush connector 20.
Fig. 6 shows a schematic top view of a stationary ring 25 which is composed of segments, at least two segments. In this example the ring 25 is composed of three segments 26, 36, 46. A different configuration is the ring 25 in one part with a slit in the ring 25 dividing the ring 25 when extended. The ring 25 fulfils the function of the housing 18 to house the interwoven filaments 2. In operation a rotary part 27 within the stationary ring 25 rotates. In this example the rotary part 27 in the middle constitutes the rotary side. Here, nine lifting devices 6 are arranged around the ring 25 of the electric machine, each three lifting devices 6 per segment 26, 36, 46. Each of the three segments 26, 36, 46 can be lifted, i.e. moved away from the centre of the ring 25, by the lifting devices 6. By lifting away one of the segments 26, 36, 46, machine maintenance is facilitated as the electric machine can still be operated with the remaining two segments 26, 36, 46. Each of the lifting devices 6 is controlled independently by the controller 7 to adjust the appropriate pressure to the ring 25. The invention may enhance life cycle, is cost-effective, immune to damages by vibration, arcing or mechanical caused crack. Further, the semi-permeable structure of the design of the interwoven filaments 2 allows adjusting of the humidity control. A different design than described above is the interwoven filaments 2 being rotatable between the adjacent parts. The interwoven filaments 2 are not fixed to the rotary side or the stationary side but only held in place to rotate freely between the rotary side and the stationary part.
While the invention has been described in detail with reference to exemplary embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention. The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. The entirety of each of the aforementioned documents is incorporated by reference herein.

REFERENCE NUMBERS

1: brush device
2: interwoven filaments
3: electric connector
4: cooling connector
5: humidity connector
6: lifting device
7: controller
11: first rotating part
12: insulation
14: second rotating part
16: conducting part
17: coupler
18: housing
19: cooling duct
20: brush connector
21: protection wall
22: fixtures
23: intermediate part
25: stationary ring
26: first segment
27: rotary part
28: bearings
29: shaft
30: sensor device
36: second segment
46: third segment

Claims

Brush device (1) for an electrical connection of an electric machine or rotary transformer, whereby the brush device (1) comprises interwoven filaments (2) for current and/or signal transmission between at least a rotary side and a stationary side.
Brush device (1) according to claim 1, whereby the material of the filaments (2) is graphite, graphite mixed with polytetrafluorethylene (PTFE), carbon nanotubes, or graphene.
Brush device (1) according to claim 1, characterized in that a housing (18) houses at least parts of the filaments (2) and a humidity connector (5) projects through the housing (18) to feed a liquid to the interwoven filaments (2) steered by a controller (7).
Brush device (1) according to claim 3, characterized in that a cooling duct (19) is designed in the housing (18) which at least partly surrounds the filaments (2), or in a brush connector (20), whereas at least a cooling connector (4) projects through the housing (18) or through the brush connector (20) to feed the cooling duct (19) with a cooling means.
Brush device (1) according to claim 4, characterized in that the cooling means comprises water, graphene lubricants or additives, and/or carbon nano-tube based lubricants or additives.
Brush device (1) according to claim 1, characterized in that at the rotary side a conducting part (16) is arranged, and the interwoven filaments (2) are assembled at the stationary side, whereby the conducting part (16) is slidable along the interwoven filaments (2) in operation.
Brush device (1) according to claim 1, characterized in that the interwoven filaments (2) are assembled at the rotary side being rotatable in operation.
Brush device (1) according to claim 1, characterized in that a lifting device (6) is arranged perpendicular to the interwoven filaments (2) to lift or press the interwoven filaments (2) to the conducting part (16), whereby the controller (7) steers the pressure of the interwoven filaments (2) onto the conducting part (16).
Brush device (1) according to claim 1, characterized in that the stationary part is designed as a rotating ring (25) arranged around a rotary part (27) and divided into two, three or more segments (26, 36, 46), whereby the segments (26, 36, 46) are liftable or removable independently from each other.
Brush device (1) according to claim 1, characterized in that the brush device (1) comprises sensor devices (30) for measuring the temperature, the humidity of the interwoven filaments (2), and/or the displacement and pressure exerted from a lifting device (6) to the interwoven filaments (2).
Brush device (1) according to claim 10, characterized in that the measuring data of the sensor devices (30) is compared to stored data in the controller (7) and the controller (7) steers the temperature, the humidity, the injection rate of fluid by the humidity connector (5), the displacement of the lifting device (6) from the interwoven filaments (2) and the pressure of the interwoven filaments (2) onto the conducting part (16) on basis of the comparison.
Brush device (1) according to claim 11, characterized in that the controller (7) determines the wear rate of the interwoven filaments (2) on basis of the data received from the sensor device (30) relating to temperature, humidity, pressure exerted onto the conducting part (16), and the absolute positioning of the lifting device (6).
Brush device (1) according to claim 12, characterized in that the controller (7) minimizes total losses of the brush device (1) by controlling the variables of temperature, humidity, and pressure exerted onto the conducting part (16).
Brush device (1) according to claim 12, characterized in that the controller (7) comprises a memory to record the calculated wear rate of the interwoven filaments (2) over time to be read out by an operator or transmitted to another electronic device.
Brush device (1) according to claim 14, characterized in that the data is transmitted via the world wide web.
Use of interwoven filaments (2) in a brush device (1) according to claim 1.