Patent Publication Number: US-11050205-B2

Title: Brush wear and vibration monitoring

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of U.S. patent application Ser. No. 15/168,607, filed May 31, 2016, which claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 62/169,222, filed Jun. 1, 2015, the entire disclosures of which are herein incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The disclosure generally relates to monitoring systems for monitoring one or more components of an electrical device, such as an electrical generator. More specifically, the disclosure relates to monitoring apparatus, assemblies, systems and methods of monitoring one or more components of an electrical device, such as monitoring the condition of a brush of a brush holder assembly of a dynamo-electric machine. 
     BACKGROUND 
     A purpose of a brush in an electrical device is to pass electrical current from a stationary contact to a moving contact surface, or vice versa. Brushes and brush holders may be used in electrical devices such as electrical generators, electrical motors, and/or slip ring assemblies, or sliding connection applications, for example, slip ring assemblies on a rotating machine such as a rotating crane or a linear sliding connection on a monorail. Brushes in many electrical devices are blocks or other structures made of conductive material, such as graphite, carbon graphite, electrographite, metal graphite, or the like, that are adapted for contact with a conductive surface or surfaces to pass electrical current. 
     In some designs, a brush box type brush holder, or other type of brush holder, may be used to support a brush in contact with a moving contact surface of an electrical device during operation. The brush and brush box may be designed such that the brush can slide within the brush box to provide for continuing contact between the brush and the moving contact surface contacted by the brush. During operation an anomalous and/or threshold condition may occur, which may be indicative that one or more components of the electrical device may need to be replaced, one or more components of the electrical device may require inspection or attention, and/or maintenance may need to be performed. For example, an anomalous and/or threshold condition may indicate that one or more of a brush, brush holder, spring, shunt, commutator, collector ring, and/or other component may need to be replaced, one or more of a brush, brush holder, spring, shunt, commutator, collector ring, and/or other component may need to be inspected, and/or maintenance may need to be performed. It would be advantageous to monitor one or more components of an electrical device in order to observe the occurrence of an anomalous and/or threshold condition. Furthermore, it would be advantageous to alert an operator and/or technician of the occurrence of an anomalous and/or threshold condition and/or schedule technician intervention. 
     SUMMARY 
     Some embodiments relate to an apparatus, assemblies, systems and/or methods for monitoring one or more components of an electrical device and/or detecting an anomalous and/or threshold condition of a brush holder assembly. 
     Accordingly, one exemplary embodiment relates to a brush holder assembly for use in an electrical generator including a moving conductive surface. The brush holder assembly includes a brush holder that is configured to be removably mounted to a mounting element on the electrical generator. A carbon brush is slidingly disposed within the brush holder and is configured to be positioned in sliding contact with the moving conductive surface. The brush holder assembly includes a handle that is moveable between an unlocked position in which the brush holder is moveable relative to the mounting element and a locked position in which the brush holder is secured relative to the mounting element. A sensor is disposed within the handle that is configured to detect an anomalous or threshold condition of the brush holder assembly. In some instances, the sensor may be included with a circuit board disposed within the handle. 
     Another illustrative embodiment is a system for detecting an anomalous or threshold condition of each of a plurality of brush holder assemblies. The system includes a plurality of brush holder assemblies and a central monitoring station that is wirelessly coupled to each of the plurality of brush holder assemblies. Each of the brush holder assemblies includes a brush holder that is configured to be removably mounted to a mounting element on the electrical generator and a carbon brush slidingly disposed with the brush holder. A handle is coupled to the brush holder and a circuit board is disposed within the handle, the circuit board including a sensor that is configured to detect an anomalous or threshold condition of the brush holder assembly. Each of the brush holder assemblies includes a wireless communications module operably coupled to the sensor. The system also includes a central monitoring system that is wirelessly coupled to each of the wireless communication modules within each of the plurality of brush holder assemblies. 
     An illustrative method for detecting an anomalous or threshold condition of each of a plurality of brush holder assemblies may include providing each of a plurality of brush holder assemblies with a circuit board including a sensor that is configured to detect a developing anomalous or threshold condition of the brush holder assembly. The method includes receiving a signal from each of the plurality of brush holder assemblies, the signal providing an indication of predicting an anomalous or threshold condition of the brush or other component associated with the particular one of the plurality of brush holder assemblies at a future time. An alert may be sent out if one of the brushes has an indication justifying replacement of the brush. 
     The above summary of some example embodiments is not intended to describe each disclosed embodiment or every implementation of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying drawings, in which: 
         FIG. 1  is an illustrative schematic view of an exemplary brush monitoring system; 
         FIG. 2  is an illustrative schematic view of an exemplary brush holder assembly; 
         FIG. 3  is an illustrative side view of an exemplary brush holder assembly in a locked position, relative to a moving conductive surface; 
         FIG. 4  is an illustrative side view of the brush holder assembly of  FIG. 3 , shown in an unlocked position; 
         FIG. 5  is an illustrative perspective view of the brush holder of  FIG. 4 , with part of the handle shown in phantom to illustrate components within the handle; 
         FIG. 6  is an illustrative perspective view of the brush holder of  FIG. 4 , with part of the handle shown in phantom to illustrate components within the handle; 
         FIG. 7  is an illustrative perspective view of the brush holder assembly of  FIG. 3 , schematically illustrating possible sensor placement; 
         FIG. 8  is an illustrative perspective view of the brush holder assembly of  FIG. 3 , schematically illustrating possible sensor placement; and 
         FIG. 9  is an illustrative perspective view of the brush holder assembly of  FIG. 3 , showing an upper surface of the carbon brush. 
     
    
    
     While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit aspects of the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. 
     DETAILED DESCRIPTION 
     For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification. 
     All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the term “about” may be indicative as including numbers that are rounded to the nearest significant figure. 
     The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). 
     As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. 
     The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The detailed description and the drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention. The illustrative embodiments depicted are intended only as exemplary. Selected features of any illustrative embodiment may be incorporated into an additional embodiment unless clearly stated to the contrary. 
     Now referring to  FIG. 1 , an illustrative system for monitoring a component of an electrical device and/or monitoring the condition of a brush of a brush holder assembly is shown. As schematically illustrated in  FIG. 1 , a monitoring system  10  may include a local monitoring component  12  and a remote monitoring site  14 . While a single local component  12  is shown, it will be appreciated that in some instances a plurality of local components  12  may be in communication with and reporting brush conditions and/or the condition of one or more other components of the brush holder assembly back to the remote monitoring site  14 . The local component  12 , which may for example represent a single electrical generator, or perhaps a single installation having several distinct electrical generators, includes a site monitor  16  and a plurality of brush holder assemblies  18 . While a total of three brush holder assemblies  18  are schematically illustrated, it will be appreciated that this is merely for ease of illustration. In some instances, for example, a single electrical generator may include 12, 24, 36, 48 or more separate brush holder assemblies  18  arranged around a moving conductive surface (e.g., commutator). 
     As can be seen, each of the brush holder assemblies  18  may be configured to communicate wirelessly with the site monitor  16 . Any suitable wireless communications protocol may be used, including but not limited to WiFi, RFID, Bluetooth and the like. Optionally, the communication between each of the brush holder assemblies  18  and the site monitor  16  may be via wired communication. In some cases, each of the brush holder assemblies  18  may be configured to monitor some aspect or feature of the brush holder assembly  18 . For example, in some cases, each of the brush holder assemblies  18  or at least some of the brush holder assemblies  18  may be configured to monitor for anomalous or threshold conditions of the brush associated with (e.g., disposed within) the brush holder assembly. Each brush holder assembly  18  may, for example, periodically transmit information to the site monitor  16  pertaining to whether any anomalous or threshold conditions have been detected. In some cases, each brush holder assembly  18  may transmit in accordance with a predetermined or user-selectable time frame. For example, periodic transmissions may be periodically transmitted every hour, once a day, etc. In some instances, each brush holder assembly  18  may only transmit information if the information has changed since the last time it was transmitted. This may, for example, reduce the power consumption of the brush holder assembly  18 . 
     As noted, the local component  12  may be a single electrical generator or a group of several electrical generators. Each of several different electrical generators may report brush condition information, including any detected anomalous or threshold conditions, to the site monitor  16 . In turn, the site monitor  16  may transmit information regarding the condition of one or more components of the brush holder assembly  18 , such as brush condition information, as well as other information if desired, to the remote monitoring site  14 . In some cases, for example, several electrical generators, each representing a local component  12 , may be located within a building. Each local component  12 , having its own site monitor  16 , may transmit information to the remote monitoring site  14 , which may in this case represent a monitoring system for the building. In some cases, the local component  12  may represent a plurality of electrical generators in a building, and the remote monitoring site  14  may receive information from a plurality of different buildings. The remote monitoring site  14  may, for example, receive monitoring information from a number of local components  12  within a particular geographic region. 
     Thus, as currently disclosed the monitoring system  10  may monitor the condition of a brush or a plurality of brushes within a brush holder assembly and/or one or more other components of an electricity generating facility, for example. In some embodiments, the monitoring system  10  may remotely and/or wirelessly monitor the condition of a brush, a plurality of brushes and/or other components over a period of time, and thus may detect a developing problem or condition and/or predict an anomalous or threshold condition of a brush, a plurality of brushes and/or other components at a future time. A processing or control center, such as a central control center, may receive data from multiple facilities in order to monitor performance, such as brush performance (e.g., brush wear) at each of the multiple facilities. The control center may be located remote from one or more electrical facilities (e.g., in a different building, facility, city, county, state, country, etc.). 
     A processing unit, which may be located at the control center, may use a software program and/or a monitor to analyze and/or monitor the performance of the brushes and/or other components in operation at the facilities, such as the current state of each brush in operation and/or an anomalous and/or threshold condition of the brushes. The software program or monitor may alert an operator, technician and/or other personnel that a brush at one of the remote electrical facilities is sufficiently worn and/or needs to be replaced, a brush at one of the remote electrical facilities is damaged, failure has occurred or is imminent, or other maintenance may need to be performed. In some embodiments, the software program, or a technician at the control center, may schedule maintenance for one of the remote electrical facilities, send personnel to perform maintenance at one of the remote electrical facilities, order and/or schedule distribution/delivery of a replacement brush or other part to one of the remote electrical facilities, route maintenance personnel and/or product delivery to a specified location, such as one of the remote electrical facilities, or arrange for other notification and/or scheduling tasks be performed at one of the remote electrical facilities or another location. Thus, the monitoring system  10  may continuously monitor the state of brushes and/or other components at a plurality of remote locations with or without direct human observation in order to alleviate the need of monitoring personnel at each remote location until it is determined that human intervention is necessary to attend to an identified problem or matter. 
     Turning to  FIG. 2 , features of the brush holder assembly  18  are schematically illustrated. The brush holder assembly  18  includes a number of mechanical parts and elements that are not illustrated in  FIG. 2 . The brush holder assembly  18  includes a circuit board  20  that may be physically located within a handle (discussed with respect to subsequent Figures) of the brush holder assembly  18  or at a different location and/or in a different component, if desired. The circuit board  20  includes a sensor  22  that may be configured to detect an anomalous or threshold condition of a brush within the brush holder assembly  18 . 
     A variety of different sensors  22  are possible, as will be discussed. A wireless communications module  24  is operably coupled with the sensor  22  such that the wireless communications module  24  may output a signal received from the sensor  22  that is indicative of the condition of the brush and/or other components of the brush holder assembly  18 . The circuit board  20  includes a power source  26  that is operably coupled to and powering the sensor  22  and the wireless communications module  24 . In some cases, the power source  26  may be a battery. In some instances, the power source  26  may be an energy harvesting element such as a Hall sensor, and may include a battery that is kept charged via the energy harvesting element. For example, illustrative energy harvesting technologies may include a kinetic (e.g., vibrational) energy harvester (e.g., a piezoelectric vibration energy harvester, a magneto-inductive vibration energy harvester, etc.), a photovoltaic energy harvester capable of harvesting energy indoors and/or outdoors, a piezoelectric energy harvester, a thermal energy harvester, a wind energy (e.g., microturbine) harvester, and/or an ambient radiation (e.g. radio frequency) energy harvester. 
     In some cases, in addition to or instead of the power source  26 , the brush holder assembly  18  may include one or more connectors and/or terminals capable of receiving power from a separate source. In such cases, the brush holder assembly  18  may be configured to receive power from an external power source when the brush holder assembly  18  is installed. For example, an electrical circuit may be completed when the brush holder assembly  18  is coupled to the mounting block  34  such that electrical power may pass from a power source through the mounting block  34 . 
     The circuit board  20  also includes a processor or controller  21 . The controller  21  is powered by the power source  26 , and is operably coupled to the sensor  22  and the wireless communications module  24 . The controller  21  may be configured to control operation of the sensor  22 , as well as to interpret the information provided by the sensor  22  to determine the condition of the brush of the brush holder assembly  18 . For example, if the sensor  22  is a photo cell that is configured to detect arcing, the controller  21  may analyze a signal obtained from the photo cell, in order to determine whether arcing is occurring. If the sensor  22  is a microphone, the controller  21  may be configured to analyze an electrical signal from the microphone and determine if there are sounds present that indicate arcing and/or abnormal vibration. If the sensor  22  is a light source, for example, the controller  21  may be configured to analyze a time-of-flight for light to leave the light source and be reflected back to a light-sensitive receiver, and determine a distance to the brush and thus an indication of brush wear. The distance the light must travel will vary as the brush wears, and thus the top surface of the brush will move further from the light source as the brush wears, resulting in a longer distance and travel time for the light. Similarly, if the sensor  22  is an ultrasound transducer, the controller  21  may be configured to analyze the time-of-flight for sound to travel from the ultrasound transducer and be reflected back to an ultrasound sensor in order to determine a distance to the brush and thus an indication of brush wear. The distance the sound must travel will vary as the brush wears, and thus the top surface of the brush will move further from the ultrasound transducer as the brush wears, resulting in a longer distance and travel time for the sound. If the sensor  22  is a magnetic sensor, with a permanent magnet mounted relative to the brush, the controller  21  may be configured to analyze a detected magnetic field strength in order to determine a distance to the brush and thus an indication of brush wear as the magnet moves away from the magnetic sensor. 
     Further features of the brush holder assembly  18  may be seen in  FIGS. 3 and 4 .  FIG. 3  shows the brush holder assembly  18  in its locked position while  FIG. 4  shows the brush holder assembly  18  in its unlocked position. The brush holder assembly  18 , for example, may include a brush holder  30  such as a brush box surrounding a brush  32  on several sides and including a plurality of guiding surfaces for guiding linear or longitudinal movement of the brush  32 . In some embodiments, the brush holder  30  may not take on the form of a box, but may include one or a plurality of guiding surfaces, such as channels, posts or columns, abutting and/or encompassing one or more sides of the brush  32  and/or extending into or through the brush  32 , or a portion thereof, for guiding linear or longitudinal movement of the brush  32 . 
     The brush holder  30  may be secured to a mounting beam  34  configured and adapted to be mounted to another structure, such as a mounting block  42 . The brush holder assembly  18  is configured to place the brush  32  in contact with a moving contact surface  40 , such as a conductive surface of a commutator or a collector ring, and conduct current therefrom. The brush  32  may extend from the lower edge of the brush holder  30  such that a wear surface of the brush  32  engages the moving contact surface  40 . The mounting beam  34  may include an over-center engagement mechanism, a slotted or channeled engagement mechanism for sliding engagement, or other mechanism for easily engaging and disengaging the brush  32  from a moving contact surface  40 , such as the conductive surface of a commutator or a collector ring without stopping the electrical generator. In other embodiments, the brush holder assembly may include a brush holder rigidly mounted to another structure holding the brush holder stationary, or mounted to another structure in any desired arrangement. For example, in some embodiments the brush holder may be bolted or welded to a stationary structure. Some such brush holders are disclosed in U.S. Pat. Nos. 6,731,042; 5,753,992; 5,621,262; 5,463,264; 5,397,952; and 5,256,925; which are incorporated herein by reference. 
     As shown in  FIG. 3 , the mounting beam  34  may include an upper beam member  36  and a lower beam member  38  hingedly or pivotedly coupled to one another. When the upper beam member  36  and the lower beam member  38  are aligned with one another (e.g., the longitudinal axis of the upper beam member  36  is parallel with the longitudinal axis of the lower beam member  28 ), the brush holder  18  may be considered to be in an engaged, or locked, position such that the brush  32  may be contiguous with or in contact with the moving contact surface  40 . When the upper beam member  36  is tilted from the lower beam member  38  (e.g., the longitudinal axis of the upper beam member  36  is oblique to the longitudinal axis of the lower beam member  38 ), the brush holder  18  may be considered to be in a disengaged, or unlocked, position such that the brush  32  may be non-contiguous with, spaced from, or otherwise not in direct electrical contact with the moving contact surface  40 . The mounting beam  34  may be removably coupled to the mounting block  42  during operation. In some embodiments, the mounting beam  34  may slidably engage with, interlock with, or otherwise be removably coupled to the mounting block  42 . The mounting block  42  may be coupled to, secured to, or otherwise extend from another structure which maintains the mounting block  42  stationary with respect to the moving contact surface  40 , for example. 
     In some embodiments, a handle  44  may be attached to the brush holder  30  to facilitate engagement and disengagement of the brush  32  from the moving contact surface  40  without stopping the electrical generator. For example, the handle  44  may be attached to the upper beam member  36  such that movement of the handle  44  actuates (e.g., pivots, slides, releases) the upper beam member  36  relative to the lower beam member  38 . In some cases, as illustrated, the handle  44  may be considered as including a lower portion  46 , an upper portion  48  that is at least substantially transverse to the lower portion  46 , and an intervening finger ring  50  that is configured to facilitate movement of the handle  44 . Other handle designs are contemplated. 
     Also illustrated in  FIG. 3  is a brush spring  52 , such as a constant force spring, which provides tension to the brush  32  to bias the brush  32  toward and in contact with the moving contact surface  40 . The spring  52  may be attached to a portion of the brush holder  30  or the mounting beam  34  of the brush holder assembly  18 , for example. In some embodiments, the spring  52  may extend along one side surface of the brush  32  between the brush  32  and the brush box and/or mounting beam  34  of the brush holder assembly  18 . Electrical leads  54  (one is visible in this view) extend from the brush  32  and are guided at least in part by a lead guide  56  that is disposed above the brush  32  and in some cases moves vertically with the brush  32  as the brush  32  moves in accordance with wear. The brush  32  is biased to move towards the moving contact surface  40  by the spring  52 . 
     In some embodiments, at least some features of the brush holder assembly  18  may substantially resemble a brush holder assembly as described in U.S. patent application Ser. No. 10/322,957, entitled “Brush Holder Apparatus, Brush Assembly, and Method”, which is herein incorporated by reference in its entirety. However, the illustrative monitoring system  10  may be amenable to any of various electrical devices and/or brush holder assembly configurations of an electrical device, such as an industrial electrical generator. For example, the disclosed monitoring system  10  may be used with brush holder assemblies, brush holders and/or brushes disclosed in U.S. Pat. Nos. 6,731,042; 5,753,992; 5,621,262; 5,463,264; 5,397,952; and 5,256,925; each of which is incorporated herein by reference. 
     As schematically shown in  FIG. 2 , the brush holder assembly  18  may include a circuit board  20  including one or more of a controller  21 , a sensor  22 , a wireless communications module  24  and a power source  26 . The circuit board  20  may be disposed at any desired or practical location on or within the brush holder assembly  18 . In some embodiments, the circuit board  20  may be disposed within the handle  44 .  FIGS. 5 and 6  are views of the brush holder assembly  18  in which outer portions of the handle  44  have been removed or otherwise made invisible such that a first circuit board  60  may be seen as being disposed within the lower portion  46  of the handle  44  and a second circuit board  62  may be seen as being disposed within the upper portion  48  of the handle  44 . In some cases, the first circuit board  60  and the second circuit board  62  are electrically coupled to each other. In some cases, the brush holder assembly  18  may include only one of the first circuit board  60  and the second circuit board  62 . It will be appreciated that in some cases, the sensor  22  may be disposed on the first circuit board  60 . 
     Turning to  FIG. 7 , in some embodiments the brush holder assembly  18  may be considered as including an optical device  64 , such as a photo cell or digital camera. The optical device  64  may be operably coupled to the first circuit board  60  and/or the second circuit board  62 , and may in some cases be aimed at a location just forward of the brush box  30 , such as a location within 5 inches, within 4 inches, within 3 inches, within 2 inches, or within 1 inch of the brush box  30  and/or brush  32 , such that the optical device  64  can see the moving contact surface  40  ( FIG. 3 ). In some cases, the controller  21  ( FIG. 2 ) may analyze a signal provided by the optical device  64  to look for indications of arcing or other potentially destructive processes. 
     In some instances the optical device  64  may be an imaging device configured to capture an analog and/or digital image of one or more components of the electrical device. For instance, the imaging device may capture an image of the moving contact surface  40  (e.g., the commutator or collector ring) of the electrical device and/or a brush  32  of a brush holder assembly  18 , or another component of the electrical device. In some embodiments, at a temporal occasion the imaging device may capture images of the moving contact surface  40  at about one-half inch increments, about 1 inch increments, about 2 inch increments, about 3 inch increments, or about 4 inch increments around the circumference of the moving contact surface  40 , for example. The image may be a black-and-white image, a gray scale image, a color image, or a thermograph (e.g., an image depicting levels of emitted radiation), for example. 
     In one embodiment, the imaging device, which may detect energy in the visible light spectrum, may generate a data signal which may be processed and/or may be converted into an image. With such an imaging device, evaluation of the coloration (e.g., discoloration) of the moving contact surface  40 , or other component of the electrical device may be performed in order to determine a condition of a brush  32  of a brush holder assembly  18 , a collector ring or commutator, or other component of an electrical device. For instance, the imaging device may be used to identify abnormal coloration of the moving contact surface  40 . 
     During normal operating conditions the moving contact surface  40  may exhibit normal coloration. In many applications, normal coloration of the moving contact surface  40  may be a shade of gray, for example. During operation, the coloration of the moving contact surface  40  may change, which may be indicative of a threshold and/or anomalous condition of the brush  32  of the brush holder assembly  18 . Such a threshold and/or anomalous condition of the brush  32  may include incidents of irregular wear, binding, arcing, burning, etching, or the like. Thus, processing and/or evaluation of a signal generated by the imaging device may be used to determine whether a threshold and/or anomalous condition of the brush  32  or other component has occurred. 
     Thus, initially, the moving contact surface  40  may be identified as having a first color, shade or intensity of coloration. At a subsequent time, the moving contact surface may be identified as having a second color, shade or intensity of coloration different from the first color, shade or intensity of coloration. In some circumstances, the second color, shade or intensity of coloration may be less than the first color, shade or intensity of coloration. However, in other circumstances, the second color, shade or intensity of coloration may be greater than the first color, shade or intensity of coloration. For instance, lightening in color, shade or intensity of coloration of the moving contact surface  40  may be an indication of arcing, causing burning and/or etching of the moving contact surface  40 . For example, in applications where normal coloration of the moving contact surface  40  may be a shade of gray, a threshold or anomalous condition may be identified when the coloration of the moving contact surface  40  changes to another shade of gray, such as a lighter or darker shade of gray. 
     In another embodiment, the imaging device, which may detect energy in the infrared spectrum, may generate a data signal which may be processed and/or may be converted into a thermal image. All objects emit radiation and the level of radiation emitted by an object increases with temperature. Therefore, an infrared camera or other thermal imaging device may be used in order to detect variations and/or changes in temperature of a component of an electrical device, such as the moving contact surface  40  of an electrical device and/or the brush  32  of a brush holder assembly  18 . 
     During normal operating conditions, the moving contact surface  40  and/or the brush  32  of the brush holder assembly  18  may emit a given level of radiation, which may be described as a normal level of radiation. The level of emitted radiation may be depicted with a thermograph (e.g. a thermal image) through color, shade or intensity of the illustrated component. During operation, the level of radiation emitted by the moving contact surface  40  and/or the brush  32  of a brush holder assembly  18  may increase, indicating an increase in temperature of the moving contact surface  40  and/or the brush  32  of a brush holder assembly  18 . Increased temperature of the moving contact surface  40  and/or the brush  32  of a brush holder assembly  18  may be indicative of a threshold and/or anomalous condition of the brush  32  or other component of the brush holder assembly  18 . Such a threshold and/or anomalous condition of the brush  32  may include incidents of irregular wear, binding, arcing, vibration, burning, etching, or the like. Thus, processing and/or evaluation of a signal generated by the imaging device  64  may be used to determine whether a threshold and/or anomalous condition of the brush  32  or other component has occurred. 
     For instance, during normal operating conditions, the moving contact surface  40  and/or the brush  32  of a brush holder assembly  18  may typically have a surface temperature in the range of about 150° F. to about 250° F., or in the range of about 180° F. to about 200° F. Thus, a thermal image of the moving contact surface  40  and/or the brush  32  of a brush holder assembly  18  may visually depict the temperature (i.e. the level of emitted radiation) of a component of the electrical device with color, shade or intensity. As the temperature of the moving contact surface  40  and/or the brush  32  of a brush holder assembly  18  increases, the color, shade or intensity illustrative of the temperature changes accordingly. Thus, variations in the level of emitted radiation corresponding to increased or decreased temperature of a component of the electrical device may be identified through evaluation of successive thermal images showing varying levels of color, shade or intensity of a component of an electrical device, such as the moving contact surface  40  and/or the brush  32  of a brush holder assembly  18 . For instance, one level of color, shade or intensity gradation of a thermal image may represent a temperature variation of about 1° F., about 2° F., about 5° F., about 10° F., or about 20° F. of the monitored component. Thus, the temperature of a monitored component may be determined through evaluation of a thermal image where the temperature associated with a given level of color, shade or intensity is known or approximated. 
     Processing and/or evaluation of the signal by the controller  21  may include an image analysis technique, such as a pixel-by-pixel comparison or visual observation, for example. However, other techniques may be used in processing and/or evaluation of data acquired. Pixel-by-pixel comparison involves comparing a first digital image with a second, or subsequent, digital image. It is noted that in using the terms “first” and “second”, the terms are intended to denote the relative temporal relationship of the images only. An algorithm, for example, may be used to systematically compare data denoting pixels of one digital image with data denoting pixels of a second digital image. A pixel is the smallest independent part of a digital image and may have the properties of color, shade and/or intensity. The resolution of the digital image is determined by the quantity of pixels creating the digital image (e.g., the greater the number of pixels, the greater the resolution of the digital image). A digital image is characterized as an array of pixels. The digital image may be divided into any sized array and may be dictated by the quality of imaging equipment and/or memory available. For example, the digital image may be an 800×600, 1024×768, or 1600×1200 array of pixels. Each pixel is identified by an integer denoting the value (e.g., color, shade and/or intensity) of the individual pixel. For example, each pixel may be specified by a “0” or a “1” denoting black or white respectively; or an integer between 0 and 255 denoting 256 shades of grey; or three integers between 0 and 255 each denoting a red, blue and green component, respectively with  256  levels for each component; or an integer between 0 and 1023 denoting 1024 infra-red levels, or other identifiable values. Thus, the color, shade and/or intensity of each pixel may be denoted by a representative integer. It may be understood that the digital identification of each pixel may be determined by the number of bits available for data regarding each pixel. 
     The controller  21  may be able to evaluate the pixels of the digital images acquired to determine if an anomalous and/or threshold condition exists. In some embodiments, the controller  21  recognizes the known value of pixels representing the normal coloration or the normal level of emitted radiation of a component of the electrical device. Thus, evaluation of the digital images may involve assessing the value of pixels of the digital images at a given time with known values corresponding to normal coloration or level emitted radiation of a component of the electrical device. If discoloration or abnormal coloring or increased levels of emitted radiation is determined, proper notification may be performed. 
     In some embodiments, the optical device  64  may be configured to detect wavelengths of light that are indicative of arcing, and to not see other wavelengths of light. If the optical device  64  is blind to wavelengths of light that are not indicative of arcing, any light registered by the optical device  64  is presumably indicative of arcing, and thus the optical device  64  may be able to provide a simple binary response of yes, arcing; or no, no arcing based simply on whether any light incident on the optical device  64  triggers the optical device  64 . 
     In some embodiments, the optical device  64  may instead be aimed at a point on an upper surface of the brush  32 , or perhaps a point on the lead guide  56  or other component moving with the brush  32 . As noted above, the lead guide  56  may be operably coupled to the brush  32 , and thus may move vertically downward with the brush  32  (and thus toward the moving conductive surface  40 ) as the brush  32  moves downward with increasing brush wear as a result of the biasing force applied by the spring  52 . In some cases, the optical device  64  may be tightly focused on a small point, providing an image with a limited number of pixels. If the distance between the optical device  64  and the focal point increases, the number of pixels within the tightly focused region will actually decrease. Thus, a change in the number of visible pixels may indicate an increase in distance. Since the brush  32  moves downward (in the illustrated orientation) in response to brush wear, an increasing distance (indicated by a reduction in visible pixels) may provide an indication of brush wear. 
     In some instances, such as illustrated in  FIG. 8 , the sensor  22  may actually include a source element  66  and a receiver element  68 . For example, the source element  66  may be a laser beam or other light source, and the receiver element  68  may be photosensitive. A light beam (such as a laser beam) may be provided by the source element  66 , which may be positioned such the light contacts and is reflected by either a top surface of the brush  32 , or perhaps the lead guide  56  or other component moving with the brush  32 , and is then detected by the receiver element  68 . By a simple calculation of distance equals rate times time, and given that the speed of transmission (of light, in this case) is known, and constant, the controller  21  can determine a distance to the brush  32  based upon the time-of-flight of the light beam. 
     In some cases, the source element  66  may be an ultrasonic transducer, and the receiver element  68  may be an ultrasonic receiver. A sound wave (such as an ultrasonic sound wave) may be provided by the source element  66 , which may be positioned such the sound wave contacts and is reflected by either a top surface of the brush  32 , or perhaps the lead guide  56  or other component moving with the brush  32 , and is then detected by the receiver element  68 . By a simple calculation of distance equals rate times time, and given that the speed of transmission (of sound, in this case) is known, and substantially constant at a given altitude and temperature, the controller  21  can determine a distance to the brush  32  based upon the time-of-flight of the sound wave. 
     In some embodiments, the sensor  22  may be a magnetic sensor, with a permanent magnet secured relative to the brush  32  or the lead guide  56 .  FIG. 9  illustrates a permanent magnet  70  that has been secured to a top surface of the brush  32 . In some cases, the permanent magnet  70  may, for example, be adhesively secured to the brush  32 , or perhaps the lead guide  56  or other component moving with the brush  32 . It will be appreciated that changes in distance between the magnetic sensor  22  and the permanent magnet  70  will be reflected in the relative strength of the detected magnetic field. Accordingly, if the detected magnetic field decreases in strength, the controller  21  may determine that the distance to the brush  32  has increased as a result of brush wear. 
     In some cases, the brush holder assembly  18  may include a user interface  72 , which is schematically illustrated in  FIG. 9 . For example, the user interface  72  may be a light such as an LED that can have a first appearance indicating that no problems have been detected by the controller  21  (e.g., the brush holder assembly  18  is functioning in a normal state) and a second appearance different from the first appearance that indicates that a problem has been detected (e.g., the brush holder assembly  18  is functioning in an abnormal state and/or a threshold or anomalous condition has been detected). In some embodiments, green may indicate an absence of problems, yellow may indicate an approaching problem, and red may indicate a serious or immediate problem. In some instances, particularly if power consumption is a concern, an unlit or dark light may indicate an absence of problems, and a lit light (of whatever color) may be an indication that a problem has been detected. In some cases, the user interface  72  may instead provide an auditory signal, particularly if a serious or immediate problem has been detected by the controller  21 . 
     In some cases, the brush holder assembly  18  may include a thermal sensor  74 . The thermal sensor  74  may be disposed at any convenient location on the brush holder assembly  18 , but in some cases as schematically illustrated the thermal sensor  74  may be disposed on the mounting beam  34 . The thermal sensor  74  may be any suitable temperature sensor, including but not limited to a thermistor or a bimetal temperature sensor. The thermal sensor  74  may be operably coupled to the controller  21  ( FIG. 2 ), and may provide an electrical signal indicative of a temperature of a component of the brush holder assembly  18 . It will be appreciated that the temperature of the component of the brush holder assembly  18  may be considered to be at least somewhat proportional to the power levels being captured by the brush  32 . If the component of a particular brush holder assembly  18  has a temperature that is significantly different from that of a like component of one or more neighboring brush holder assemblies  18 , the controller  21  will recognize that a problem potentially exists. 
     In some instances, each of a plurality of brush holder assemblies  18  may include a thermal sensor  74  such that an indication of temperature of a component of each of the plurality of brush holder assemblies  18  may be obtained simultaneously. For instance, each brush holder assembly  18  of a plurality of brush holder assemblies  18  mounted on an electrical generator or other dynamo-electric machine may include a temperature sensor for measuring a temperature of the brush, a lead extending from the brush, a terminal, or other component of the brush holder assembly  18 . Accordingly, the thermal sensors of each of the brush holder assemblies  18  may simultaneously measure the temperature of the component (e.g., the brush, a lead extending from the brush, a terminal, etc.) of the associated brush holder assembly  18  which can be compared with one another. At any particular point in time, the power levels passing through each of the brushes  32  will generally be about the same. If one of the brushes  32  indicates a significant difference in power level passing through the brush  32 , as indicated by a temperature difference between the like component of other brush holder assemblies  18  being monitored, this may be an indication that a problem exists. 
     In some cases, an amperage meter may be operably coupled to a component of each of the plurality of brush holder assemblies  18  in order to obtain a more direct indication of relative power levels between adjacent brushes  32 . For instance, each brush holder assembly  18  of a plurality of brush holder assemblies  18  mounted on an electrical generator or other dynamo-electric machine may include an amperage meter for measuring an electrical current passing through the brush, a lead extending from the brush, a terminal, or other component of the brush holder assembly  18 . Accordingly, the amperage meter of each of the brush holder assemblies  18  may simultaneously measure the current passing through the component (e.g., the brush, a lead extending from the brush, a terminal, etc.) of the associated brush holder assembly  18  which can be compared with one another. At any particular point in time, the power levels passing through each of the brushes  32  will generally be about the same. If one of the brushes  32  indicates a significant difference in power level passing through the brush  32 , as indicated by an amperage difference between the like component of other brush holder assemblies  18  being monitored, this may be an indication that a problem exists. 
     In some instances, a brush  32  having a relatively lower temperature, or a reduced amperage flowing through the brush  32 , may indicate for example that the brush  32  is making poor contact with the moving contact surface  40 . In some cases, a brush  32  having a relatively higher temperature may be indicative of a threshold and/or anomalous condition of the brush  32  or other component of the brush holder assembly  18 , including but not limited to irregular wear, binding, arcing, vibration, burning, etching, or the like. In some cases, a temperature between a portion of the brush  32 , such as the brush contact face frictionally contacting the moving conductive surface  40  of the associated brush holder assembly  18  can be compared with the temperature between a portion of a brush of one or more additional brush holder assemblies  18 , such as the brush contact face frictionally contacting the moving conductive surface  40 , and the temperature difference may be used to determine if a problem exists. Similarly, the temperature difference between the terminals of two or more brush holder assemblies  18  may be used to determine if a problem exists. The degree of temperature difference may indicate a potential threshold and/or anomalous condition of the brush  32  or other component of the brush holder assembly  18 . 
     Those skilled in the art will recognize that the present invention may be manifested in a variety of forms other than the specific embodiments described and contemplated herein. Accordingly, departure in form and detail may be made without departing from the scope and spirit of the present invention as described in the appended claims.