ПІДВИЩЕННЯ НАДІЙНОСТІ ТА ЕФЕКТИВНОСТІ ЕКСПЛУАТАЦІЇ ТУРБОГЕНЕРАТОРІВ ЕЛЕКТРИЧ-НИХ СТАНЦІЙ
Authors:   International Science Group, Хвалін Денис 
Published: June 2021

Khvalin D.I. Increase of the reliability and operation efficiency of turbogenera-tors power plants. – Monograph. In the book a crucial scientific problem is solved – the development and scien-tific substantiation of the method for a stator core end packets internal shielding for improvement of the reliability and loading capacity of powerful turbogenerators by reducing the axial magnetic flux magnitude and maximum concentration of eddy cur-rents in a core end packets. Based on the complex research of the electromagnetic and heating processes using mathematical and physical simulation, the efficiency of developed constructive solution of a stator core end zone is proved. To increase the accuracy of obtained re-sults a correspondence principle of models and real object to the same generator, namely the serial turbogenerator type TGV-500, is applied. The advantages of the mathematical models construction in the software COM-SOL Multiphysics are shown. The most significant advantage is the ability to solve multiphysical problems that allows creating the complex (interrelated) models. Also an important advantage is the simplicity of interface in a coefficient form, that enables to simulate physical processes without focusing directly on the solution of differential equations, while paying attention to variation calculations (experiments) for solving set tasks. Three-dimensional models have not found wide application due to the com-plexity of the end zone design of powerful generators as well as significant computa-tional efforts which even with the use of modern computer technology needs a series of simplifications, and also since the formation of informative and sufficiently de-tailed conclusions concerning parameters and characteristics of the object requires a large number of variation calculations. Therefore an approach for the analysis of heat processes in a stator core end zone of turbogenerator is used with the help of a con-secutive logic transition from a simple model of electromagnetic field in machine ac-tive part to more difficult models of end zone using the previous results in the next that allows obtaining a solution for determination of temperature distribution in diffi-cult areas. The use of specialized software allowed elaborating sufficiently flexible mathematical model in terms of modification of its individual components that allows us to concentrate on achievement of set goal, rather than solving utilitarian problems. The algorithm, detailed mathematical description and solution of a quasi-three-dimensional task for determination of electromagnetic field and temperature distribu-tion in a stator core end zone of a powerful turbogenerator using a numerical method were presented by the author. A mathematical model differs from those used and known today, by more complete account of the physical and technical factors and the accuracy of calculation results in conditions of a simplicity of software realization. In particular, a method for calculating end zone turbogenerator electromagnetic field is developed, which allows description of the currents for stator winding frontal part considering geometric shape of frontal connections and, most importantly, the load condition of a turbogenerator. For the first time works of modern scientists who develop quasi-three-dimensional models are analyzed. By means of consecutive logic reasoning it was shown that the difficulty of calculating problem of powerful turbogenerators end zone makes us to use a series of simplifications in the task formulation, suitable in some cases and unsuitable for others, as a result obtained solutions often too approx-imately describe the conformity to natural laws of electromagnetic field distribution. For the first time a mathematical model section of generator active part is sub-stantiated with the help of which while simulation a logic transition to the end zone model is realized, and also advantages and disadvantages for an existing sections of similar models are considered. The universality and independence of a constructed mathematical model is shown. A mathematical model allows carrying out electromagnetic and heat calcula-tions and, accordingly, investigating any load condition of machine. Calculated study of electromagnetic field and temperature distribution in the structural elements of a turbogenerator stator end zone under load conditions at a different power factor in-cluding the conditions of reactive power consumption is conducted. A new constructive solution of a stator core end zone of alternating current electrical machine is proposed on the basis of the application of internal shielding of a stator core end packets for increasing the efficiency of shield with high technologi-cality at its manufacturing and, as a result, improving the safety, reliability, loading capacity and operation efficiency of a powerful machines, in particular turbogenera-tors of nuclear power station unit, and also expanding their functional ability. With the help of theoretical researches on a mathematical model, it is shown that the proposed design of a stator core end packet reduces the maximum tempera-ture of end packet under load conditions of a turbogenerator with reactive power con-sumption under nominal load condition of machine. This allows us to refuse the per-formance of longitudinal cuts in end packets teeth and reduce the size of deep cham-fer for end packets teeth that increases the mechanical stiffness of a stator core, as well as the coefficient of magnetic connection between windings, improves the technology of manufacturing and assembly, reduces the labor costs. For the first time using a numerical method based on a complex calculation of electromagnetic and heating processes the efficiency of a turbogenerator end zone constructive variants, that are widely used in operating machines for reducing the heating of a stator core end packets was investigated. According to the criterion of decreasing the maximum and average temperature in the structural elements, a com-parative analysis of the variants efficiency with proposed constructive solution of a stator core is made. A complex of experimental researches of tooth-slot configuration shields effi-ciency on a scale physical model is made. It is shown on the basis of axial component dependence of magnetic flux density on the shielding systems constructive parameters of a tooth-slot segments and their location within a stator core, that such shields pro-tects not only the yoke of a stator core, but also the most heated zone of a stator core end packets of a turbogenerator – the teeth. The idea of the structural shielding is sub-stantiated; the optimum effect design of shield and its location in an end packet area are explored. The researches results of stator core shields efficiency by means of a scale physical model allowed us to obtain more specific information for developed mathe-matical model of a turbogenerator end zone and get the database necessary for numer-ical calculation of electromagnetic field and temperature distribution with internal shielding of a stator core end packets. Based on theoretical and experimental researches recommendations for the ap-plication of the method for a stator core internal shielding were developed, which re-duces the axial magnetic flux magnitude and the unevenness of eddy currents distri-bution at the radial direction in a stator core end packets of a powerful generator and, consequently, their heating. In order to increase the accuracy of experimental data obtained with the help of a scale physical model, as well as testing of constructed mathematical model, using the latest one «adjusted» to a physical model, the numerous experimental researches of tooth-slot configuration shields effectiveness were carried out. The small difference of magnetic flux density values obtained using mathematical simulation from the ex-perimental ones allows us to draw a conclusion about the accuracy of result. In addi-tion, the heat calculation for rated load condition of a turbogenerator with the help of a mathematical model as well as comparison of these results with experimental data for a real generator analogous type and power are made. The differences of calculated and experimental values not exceed 7 %. All data obtained using both simulation and natural experiment are corresponded to the same turbogenerator that in total makes results of mathematical simulation accuracy, which cannot be obtained in a real object by various reasons of objective and subjective nature.