Coupling Calculation Of Temperature And Thermal Stress Of Stator In Large Hydro-Generator

With the rapid development of economic, the problem of global warmingand shortage of energy supply which affect human existence is becomingincreasingly prominent. Under the trend of energy saving and emissions reducingall over the world, the clean, green, renewable energy is liked by people. As oneof the the largest global renewable energy sources, hydropower has matureexploit technologies, and received more and more attentions. Working as thecritical energy generation device in hydropower plant, hydro-generator isdesigned to be with larger capacity, and the electromagnetic load and the thermalload in such machines are also increasing. Therefore, the studies onelectromagnetic theory, temperature distribution and thermal stress distribution inlarge hydro-generators are particularly important. The researches on heat transfer,cooling, thermal stress and failure detection in lager hydro-generator relate tovarious subjects and fields, such as electromagnetic field theory, fluid dynamics,structural mechanics, computational method. Thus these theoretical study work issuch a comprehensive one with significances both in academic and practice.First of all, a two-dimensional transient electromagnetic field calculationmodel of a250MW hydro-generator is established, transient electromagneticprocesses in the generator are calculated and analyzed by the time-stepping finiteelement method, and third harmonic content and distribution of the magneticfield in the tooth at the rated short circuit are studied; on this basis, the losses ofgenerator stator are calculated, including: the basic iron loss and additional ironloss no-load, additional loss in the stator caused by the third harmonic magneticfield at the rated current short-circuit state, the eddy current losses of the strands.Second, the distribution of heat source are calculated by the stator losses distribution in Chapter II, the three-dimensional calculation model of temperaturefield is established in the range of half tooth, half slot, half of the core section,and its boundary conditions are defined, three-dimensional temperaturedistribution of the hydro-generator stator is calculated and analyzed; the changesof the temperature distribution taking into account tooth additional loss caused bythree harmonic at the rated current short circuit are studied, stator temperaturedistribution are analyzed when the distribution coefficient of strands eddy currentloss are different, some useful conclusions are obtained.Finally, the calculation model for a polar distance and entire axial range inhydro-generators is established, the coupling calculation of three-dimensionaltemperature and thermal stress are done, the thermal stress distribution in thestator are got, stress analysis are carried out in the location of stressconcentration, and combined with the example generator operation failure ofhydro-generator, a prediction about operation failure may be caused by thetemperature and thermal stress is made, some useful conclusions are got, theyprovides a reference for future optimization design and failure detection of largehydro-generator.