BRUSH WEAR MONITORING ARRANGEMENT

Abstract

Provided is a brush wear monitoring arrangement including a carbon brush realized to transfer electric current between a stationary structure and a rotating structure, wherein a side face of the carbon brush is provided with a wear indicator; a brush holder realized to accommodate the carbon brush, which holder is provided with an aperture formed to expose a portion of the wear indicator when the carbon brush is arranged in the holder; and a monitoring means for observing the exposed portion of the wear indicator during usage of the carbon brush. Further provided is a method of monitoring wear on a carbon brush.

Claims

1. A brush wear monitoring arrangement comprising: a carbon brush configured to transfer electric current between a stationary structure and a rotating structure, wherein a side face of the carbon brush is provided with a wear indicator; a brush holder configured to accommodate the carbon brush, the brush holder including an aperture formed to expose a portion of the wear indicator when the carbon brush is arranged in the brush holder; and a monitoring means for observing the portion of the wear indicator during usage of the carbon brush.

2. The brush wear monitoring arrangement according to claim 1, wherein the wear indicator is provided as a sticker with an adhesive underside for adhering to the side face of the carbon brush.

3. The brush wear monitoring arrangement according to claim 2, wherein the wear indicator comprises a pattern printed onto the side face of the carbon brush.

4. The brush wear monitoring arrangement according to claim 1, wherein the wear indicator comprises a transition from an initial color to a final color.

5. The brush wear monitoring arrangement according to claim 1, wherein the wear indicator comprises a high contrast ratio between the initial color and the final color.

6. The brush wear monitoring arrangement according to claim 1, wherein the wear indicator comprises a transition from black to white.

7. The brush wear monitoring arrangement according to claim 1, wherein the wear indicator comprises a sequence of multiple colors.

8. The brush wear monitoring arrangement according to claim 1, wherein the monitoring means comprises an image sensor configured to capture images of the portion of the wear indicator during usage of the carbon brush.

9. The brush wear monitoring arrangement according to claim 8, wherein the monitoring means comprises an image analysis unit configured to detect differences in the images and to estimate a remaining lifetime of the carbon brush on a basis of the differences.

10. The brush wear monitoring arrangement according to claim 1, comprising a light guide extending between the aperture and the monitoring means.

11. The brush wear monitoring arrangement according to claim 1, comprising a light source arranged to illuminate the portion of the wear indicator exposed in the aperture.

12. The brush wear monitoring arrangement according to claim 9, comprising a communication interface configured to transmit the images to a control arrangement of the electrical machine.

13. A method of monitoring wear on a carbon brush, the method comprising: providing a wear indicator on a side surface of the carbon brush; arranging the carbon brush in a brush holder; providing an aperture in the brush holder, the aperture shaped to expose a portion of the wear indicator; and monitoring the portion of the wear indicator to estimate a remaining lifetime of the carbon brush.

14. The method according to claim 13, comprising a step of reporting the estimated remaining lifetime to a remote-control arrangement of the electrical machine.

15. A wind turbine comprising a generator with a stator and a rotor, a number of carbon brushes for transferring electric current between the rotor, and the stator, and wherein at least one carbon brush is part of the brush wear monitoring arrangement according to claim 1.

Description

BRIEF DESCRIPTION

[0025] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0026] FIG. 1 shows an embodiment of the inventive brush wear monitoring arrangement;

[0027] FIG. 2 shows a carbon brush for use in the brush wear monitoring arrangement of FIG. 1;

[0028] FIG. 3 shows a brush holder for use in the brush wear monitoring arrangement of FIG. 1;

[0029] FIG. 4 shows alternative wear indicators for application to a carbon brush in an embodiment of the inventive brush wear monitoring arrangement;

[0030] FIG. 5 shows a further embodiment of the inventive brush wear monitoring arrangement; and

[0031] FIG. 6 shows an electrical machine with an embodiment of the inventive brush wear monitoring arrangement.

DETAILED DESCRIPTION

[0032] FIG. 1 shows an embodiment of the inventive brush wear monitoring arrangement 1, with a brush holder 11 mounted to a stationary component 21 of an electrical machine 2. A carbon brush 10 is contained in the brush holder 11, which includes a spring 11S to apply pressure against the carbon brush 10, thereby pressing its contact face 10C against an electrically conducting surface of the rotating component 22 of the electrical machine 2. A wire 10W or cable extends from within the body of the carbon brush 10 and can be clamped or otherwise attached to the electrically conducting stationary component 21. In this way, the carbon brush 10 provides a path for lightning current I.sub.hi or leakage current to electrical ground.

[0033] The brush holder 11 has been formed to include an aperture 11A or “window” 11A on one side. Through this aperture, a portion W.sub.view of a wear indicator W can be seen. The wear indicator W has been attached to the corresponding side face of the carbon brush 10. In this exemplary embodiment, a camera 120 is arranged to have a line-of-sight to the aperture 11A as indicated by the dashed line, so that it can capture an image P of the exposed portion W.sub.view of the wear indicator W. The camera 120 can be configured to automatically capture images P at regular intervals, for example once a day, or might be controlled from a remote operator to capture images P at various times. The images P are processed in an image analysis unit 121. This can be local, and may receive the images P from the camera 120 over a suitable interface. Alternatively, the images P may be transmitted, for example over a (wireless) local area network or other suitable communications interface to a remote controller of the electrical machine. Although not shown in the diagram, the monitoring arrangement 1 may also include a flash or other light source to illuminate the exposed portion W.sub.view of the wear indicator W in the aperture 11A, so that consistently good-quality images P may be obtained, even if conditions in the electrical machine 2 are dark.

[0034] FIG. 2 shows a carbon brush 10 for use in the brush wear monitoring arrangement of FIG. 1. The diagram shows a wear indicator W applied to a side face 10S of the carbon brush 10. The wear indicator W could be printed directly onto the side face 10S of the carbon brush 10, or as shown here—printed onto a sticker which is then attached to the carbon brush 10. The wear indicator extends over the effective working length 10L of the carbon brush 10. Usually, a portion of a carbon brush (indicated here by the dotted line) cannot be used, and contains the embedded end of the connector wire 10W. In this exemplary embodiment, the wear indicator W has an initial or first color Ca at one end (the end nearest the contact face 10C of the carbon brush 10) and gradually transitions to a final or second color Cz with increasing distance towards the rear of the carbon brush 10. Here, the initial color Ca is black, and the final color Cz is white, with an essentially unlimited range of grey shades between the initial black color Ca and the final white color Cz. It shall be understood that the body of the carbon brush 10 is also black, although this is not shown in the drawing.

[0035] FIG. 3 shows a brush holder 11 for use in the brush wear monitoring arrangement of FIG. 1. A window 11A or aperture 11A in one side wall of the brush holder 11 allows a corresponding portion W.sub.view of the wear indicator W of FIG. 2 to be seen when the carbon brush 10 is inserted into the brush holder 11. The diagram also shows the rectangular cavity into which the carbon brush will be inserted, and through-holes through which fasteners can be inserted to mount the brush holder 11 to a component of an electrical machine. For simplicity, the diagram does not show the spring assembly that will apply pressure to a carbon brush inserted in the holder 11.

[0036] FIG. 4 shows alternative wear indicators W for application to a carbon brush in an embodiment of the inventive brush wear monitoring arrangement. In each embodiment, there is a transition from an initial color Ca or pattern at one end (for placement near the contact face) to a final color Cz or pattern at the other end. The colors and/or patterns are chosen so that these can easily be analysed by a simple image processing algorithm to determine the value of the exposed portion W.sub.view of the wear indicator W. Here, a value of 100% may correspond to the darkest region of the wear indicator W, while a value of 0% may correspond to the lightest region of the wear indicator W. The value of “grey” (i.e. a mixture of the darkest and lightest values) is relatively easy to establish using a suitable image processing technique, as will be known to the skilled person.

[0037] FIG. 5 shows a further embodiment of the inventive brush wear monitoring arrangement 1. Here, a light guide 122 extends from the aperture 11A to an camera housing of the monitoring arrangement 1. A flash LED light source 123 and image sensor chip 120 are arranged at the other end of the light guide 122. To capture an image P, the flash 123 can send a light pulse through the light guide 122. This is reflected from the exposed portion W.sub.view of the wear indicator W and detected by the image sensor 120. The advantage of this embodiment is that the image sensor 120 does not need a clear view of the aperture, but can be placed at any convenient location, and even very poor lighting conditions inside the generator will have no effect on the image quality.

[0038] FIG. 6 shows an electrical machine 2—in this case a direct-drive wind turbine generator 2—with an embodiment of the inventive brush wear monitoring arrangement 1. Several carbon brushes of the same type are arranged about the circumference of a stationary component, for example onto an end plate of the generator stator 2. During operation of the generator, the contact faces of the carbon brushes are pressed against a rotating surface, for example a brake plate that is mounted to the outer rotor. For clarity, these details are not shown here, and have already been explained with the previous diagrams. An image sensor 120 of the monitoring means 12 is provided for at least one carbon brush that has a wear indicator as explained above, and the camera is set up to capture images P of the exposed portion of that wear indicator. The images P collected by the image sensor 120 are transmitted to a control arrangement 3, for example a remote park controller 3, and processed. In this exemplary embodiment, modules of a monitoring means 12 are distributed over the wind turbine 2 and the park controller 3, for example with the image sensor 120 “on site” in the wind turbine, and the corresponding image analysis unit 121 in the remote park controller 3. The wind park can comprise any number of wind turbines, and the park controller 3 can implement a single image analysis unit 121 that processes images P from all wind turbines that are equipped with an embodiment of the inventive brush wear monitoring arrangement.

[0039] Since all carbon brushes are of the same type, are replaced simultaneously and exposed to the same conditions during their lifetime, it is sufficient to monitor a single carbon brush for wear. If the monitored brush is deemed to be approaching the end of it useful lifetime, a service procedure is scheduled by the park controller 3, and all carbon brushes are replaced at the same time.

[0040] The diagram also indicates that the park controller 3 may receive images P from other wind turbines 2 of the wind park, when each wind turbine is equipped with an embodiment of the inventive brush wear monitoring arrangement. By obtaining real-time data regarding brush wear from all wind turbines of the wind park, it is possible for the park controller 3 to identify any carbon brushes that need replacing, thereby avoiding the risk of LEMP damage through ineffective carbon brushes. Furthermore, by receiving such detailed real-time data from the brush wear monitoring arrangements, it is possible for the park controller 3 to schedule service routines with a favorably high degree of efficiency.

[0041] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0042] For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements. The mention of a “unit” or a “module” does not preclude the use of more than one unit or module.