Patent Application
20090232183
The subject invention relates to electric machines and, more particularly, the subject invention relates to the monitoring of temperature in electric machines.
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.
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'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.
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.
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.
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.
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:
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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.
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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.
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.
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.
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.
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.
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.
