TECHNICAL FIELD
[0001] The present disclosure relates to a brush device in an electrical machine for an
electrical connection or signal connection.
[0002] 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
[0003] 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
[0004] 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.
[0005] 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.
[0006] Further examples of the invention are described in the dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] 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
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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
[0017]
- 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
1. 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.
2. 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.
3. 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).
4. 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.
5. 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.
6. 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.
7. Brush device (1) according to claim 1, characterized in that the interwoven filaments (2) are assembled at the rotary side being rotatable in
operation.
8. 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).
9. 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.
10. 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).
11. 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.
12. 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).
13. 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).
14. 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.
15. Brush device (1) according to claim 14, characterized in that the data is transmitted via the world wide web.
16. Use of interwoven filaments (2) in a brush device (1) according to claim 1.