Abstract:
A system and method to measure a characteristic of a component of an electric machine. The system includes an optical fiber disposed proximate to the component, at least one sensor, disposed along the optical fiber, to detect the temperature of the component, and a data acquisition system operably coupled to the sensor via the optical fiber to generate real-time data in accordance with the detected temperature of the component during an operation of the electric machines.

Description:
BACKGROUND 
       [0001]    The subject invention relates to electric machines and, more particularly, the subject invention relates to the monitoring of temperature in electric machines. 
         [0002]    Electric machines may be, for example, turbine-generators, hydro-generators, motors, and wind-generators. Typically, the electric machines include various components, such as core iron, stator bars and a stator flange. The core iron, which comprises thousands of laminations, the stator bars and the stator flange, may themselves support copper windings, which are threaded through the components and along which electric currents flow when the electric machines are operated. While this current does not normally cause temperatures of the various components to rise significantly, local overheating, particularly with respect to the laminations, has been observed when the copper windings or some other feature within the electric machines malfunction. In this case, if the overheating is excessive (i.e., if the laminations are heated to a temperature above the melting point of their respective materials), damage to the electric machine may ensue. 
         [0003]    Currently, various methods and systems, such as resistance temperature detection (RTD) and temperature coefficient (TC) monitoring systems, are used to evaluate, e.g., core iron temperatures. These methods and systems, however, rely upon components that are sensitive to electro-magnetic interference similar to that which is caused by the electric machines and, thus, the electric machines must be off-line to perform the necessary measurements. Additionally, the current methods and systems tend to be operator sensitive and subject to an operator&#39;s interpretation of the results. Further, the electrical machines must be at least partially disassembled to allow the measurements to be performed. The disassembly of the machines increases machine downtime and associated costs. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    In accordance with an aspect of the invention, a system to measure a temperature of a component of an electric machine is provided and includes an optical fiber disposed proximate to the component, at least one sensor, disposed along the optical fiber, to detect the temperature of the component, and a data acquisition system operably coupled to the sensor via the optical fiber to generate real-time data in accordance with the detected temperature of the component during an operation of the electric machine. 
         [0005]    In accordance with another aspect of the invention, a system to measure temperatures of components of an electric machine is provided and includes a first set of sensors, disposed along optical fibers and dispersed from one another at a first interval in a predetermined direction relative to the components, to each detect a temperature of corresponding local portions of the components, a second set of sensors, disposed along optical fibers proximate to a hot-spot of the components and dispersed from one another at a second interval in the predetermined direction, to each detect a temperature of corresponding local portions of the components, and a data acquisition system operably coupled to each of the first and second set of the sensors via the optical fibers to generate real-time temperature data in accordance with the detected temperatures. 
         [0006]    In accordance with another aspect of the invention, a method of operating an electric machine by monitoring temperatures of components thereof is provided and includes installing a set of optical fibers, including sensors configured to detect temperatures of the components, at various positions proximate to the components, and interrogating each of the sensors so as to generate real-time temperature data of the components, while the electric machine is in operation, in accordance with the detected temperatures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    These and/or other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
           [0008]      FIG. 1  is a perspective view of components of an electric machine; 
           [0009]      FIG. 2  is a magnified perspective view of components of an electric machine; and 
           [0010]      FIG. 3  is a schematic view of an optical fiber and a data acquisition 
           [0011]    system. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Referring to  FIGS. 1 and 2 , an electric machine  1  includes components, such as core iron  10 , which itself includes a lamination stack  11  and stator bars  12 , which are disposed at distal ends of the lamination stack  11 , field windings (not shown), stator endwinding components, stator electrical components and bus work. The lamination stack  11  comprises stacked laminations  13  that are organized into lamination packages  14  of various sizes. Band gaps  15 , through which ventilation gas is allowed to flow, are defined between some of the lamination packages  14 . 
         [0013]    With reference to  FIG. 1 , each lamination  13  includes a body  20  having opposing annular faces  21  and  22  and an aperture  23  extending through the body  20  from one face  21  to the other  22 . The body  20  includes an exterior surface  24  and an interior surface  25 . The interior surface  25  includes annularly arranged teeth  26  that form an inner border of the body  20  and an outer border of the aperture  23 . When the laminations  13  are assembled together to form the lamination stack  11 , the lamination stack  11  includes a through-hole  27  defined therein along an axis thereof. 
         [0014]    With reference to  FIG. 2 , the laminations  13  at distal ends of the lamination stack  11  form stepwise lamination packages  14 , in which the corresponding apertures  23  of the local laminations  13  have slightly larger diameters than those of other laminations  13 . Thus, when these local laminations  13  are assembled, relatively rounded distal edges  28  of the through-hole  27  are formed. Further, when the lamination stack  11  is assembled, the teeth  26  form an annular series of axially extending core slots  29 . 
         [0015]    With reference back to  FIG. 1 , the core iron  10  is at least partially encased by a frame  30  that seals the core iron  10  and which is penetrated by a gas tight gland  40  through which the ventilation gas is injected and through which at least one optical fiber sensor  50  is drawn toward the core iron  10 . A rail  60  supports the optical fiber sensor  50  at any one of various positions around the core iron  30 . In various embodiments, the optical fiber sensor  50  is plural in number with each of the optical fiber sensors  50  being simultaneously supported at various circumferential positions around the core iron  10 . 
         [0016]    In accordance with embodiments of the invention, the optical fiber sensors  50  may be bonded to an interior of the core iron  10  along the laminations  13 , the stator bars  12  or any other components to which the optical fiber sensors  50  are to be attached. The bonding may be accomplished by the use of epoxy or other similar adhesives. In another embodiment, the optical fiber sensors  50  may be embedded into the laminations  13 , the stator bars  12  or any other components to which the optical fiber sensors  50  are to be attached during manufacturing processes thereof. 
         [0017]    With reference now to  FIG. 3 , the optical fiber sensors  50  each comprise a fiber optic cable  51  along which a plurality of sensors  52  are distributed at a predetermined spatial interval, which may be, e.g., about 1 cm. The sensors  52  may comprise Bragg grating sensors or any other similar sensor. The optical fiber sensors  50  are operably coupled to a data acquisition system  70 . The optical fiber sensors  50  and the data acquisition system  70  may be obtained, for example, from Luna Innovations which provides such under its marketing name, “Distributed Sensing System.” 
         [0018]    In an embodiment, the data acquisition system  70  is configured to interrogate the sensors  52  by transmitting a signal to each of the sensors  52  along the fiber optic cables  51  with each of the sensors  52  then reflecting a signal back to the data acquisition system  70 . Each of the reflected signals is indicative of temperatures of components that are local to and/or proximate to the corresponding sensor  52 . In a further embodiment, the reflected signal from each of the sensors  52  may be modulated by a unique frequency. This allows the data acquisition system  70  to apply filtering operations to the reflected signals to thereby retrieve and identify data of the particular reflected signal of each of the sensors  52 . 
         [0019]    Since the data acquisition system  70  interrogates the sensors  52 , which are provided at a predetermined spatial interval, the data acquisition system  70  is configured to generate a distributed temperature profile of the core iron  10  and the stator bars  12  and any other component to which the optical fiber sensors  50  are attached. Moreover, the predetermined spatial interval between the sensors  52  or the orientation of the fiber optic cables may be varied. That is, the predetermined spatial interval between the sensors  52  or the orientation of the fiber optic cables  51  may be chosen such that at least one or more sensors  52  is/are located in a known hot-spot of the core iron  10 , such as along certain laminations  13  or proximate to the stator bars  12 , in order to provide detailed temperature measurements at areas of likely temperature increases. Such hot-spots can be identified by sensors  52  dispersed at spatial intervals of 1 cm from one another, and then monitored by modifying increasing the number of sensors  52  proximate to the hot-spot. 
         [0020]    For example, the relatively rounded distal edges  28  of the through-hole  27  of the core iron  10  may be subject to axial electromagnetic flux that tends to cause increased temperatures. As such, in an embodiment of the invention, the fiber optic cables  51  may be disposed to traverse the rounded distal edges  28  at an oblique angle such that a dispersion of the corresponding sensors  52  is increased proximate to the rounded distal edges  28 . As alternate embodiments, the fiber optic cables  51  may be arranged near the relatively rounded distal edges  28  in oscillating patterns or staggered with respect to one another such that a number of corresponding sensors  52  is increased. 
         [0021]    During an operation of the electric machine  1 , the components of the electric machine  1 , such as the laminations  13  or the stator bars  12 , may experience temperature changes that can be tracked by the optical fiber sensors  50 . That is, an exemplary temperature change may involve a temperature increase of an individual lamination  13  that is either directly observable by a local sensor  52  or which results in measurements of tension/compression in the local sensor  52 . The data acquisition system  70  measures the observed temperature increase or the positive/negative strain and interprets the measurement as indicative of the temperature increase. 
         [0022]    As the components of the electric machine  1  experience temperature changes during operations thereof, increases in the measured temperatures may reflect a need for service or replacements. For example, where the measured temperature of a lamination  13  exceeds a melting point of the materials used in the construction of the lamination  13 , the lamination  13  and its neighboring laminations  13  may be identified as being in need of replacement. However, since a utilization of the optical fiber sensors  50  allows for real-time measurements of temperatures of the components of the electric machine  1  consistently during operations thereof, consistent monitoring of the measurements is made possible. As such, issues relating to increased temperatures of the components may be resolved before the measured temperatures exceed damage causing levels. 
         [0023]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.