METHODS AND MEANS FOR ASSESSING THE TECHNICAL CONDITION AND DIAGNOSING THE DAMAGES OF THE DESIGN OF ELECTRIC MACHINE
At the сhair of Electromechanics of NTUU "Kyiv Polytechnic Institute named I. Sikorsky" a series of researches and developments concerning creation of methods and means of reliable assessment of technical state and diagnostics of damages of electrical machinery (EM) design was performed.
The urgency of this direction of research is primarily due to the presence of a large number of EM, including powerful ones, which have worked out warranty periods of operation, but continue to work in the composition of technological systems. Reliable diagnostics of defects EM can promptly and reasonably lead them to repair on the basis of the results of evaluation of their actual technical state and to get rid of economic losses and environmental consequences of accidental stops of EM. Analysis of statistical data indicates that most of damaged nodes of these EM are: electrical isolation of the stator winding EM alternating current; short-closed rotor winding of asynchronous machines; isolation of sheets of magnetic core. Development of methods and means of diagnosing these injuries was carried out at the chairl of electromechanics NTUU "KPI".
1. Problems of functional diagnostics (in the process of operation of the machine) and test diagnostics (in the process of repair and manufacture of machines) of rotors of asynchronous machines with short-circuited winding were investigated by prof., D.Sc. Vaskovsky Y.M., Associate Professor, Ph.D. Kovalenko MA, Associate Professor, Ph.D. Geraskin O.A. The original mathematical models of electrical machines that have damaged construction are developed. Using the method of spectral analysis, a system of diagnostic features was proposed and substantiated, which allows to identify with a high probability different types of damage to the rotor of the asynchronous machine (cracking and breaking of the rods and short-circuiting rings of the rotor winding, eccentricity of the rotor, damage to the core of the rotor, etc.), including combined defects and small-developed defects at the initial stages of their development. Devices for testing of short-circuit winding of rotor have been developed and implemented.
The research was carried out jointly with the scientists of the Institute of Electrodynamics of the National Academy of Sciences of Ukraine. The results of research and development are reflected in two PhD theses, in a number of publications in professional editions, including in the scientific monograph.
2. Research on the problem of diagnostics of electrical insulation of windings of stators of electric machines of alternating current was headed by associate professor, Ph.D. Chumak VV.
Assoc. professor, Ph.D. Chumak V.V. and Associate Professor, Ph.D. Kovalenko M.A. developed and implemented "The system of non-destructive testing and diagnostics of the state of the charged core and electrical isolation of winding EM in the process of their manufacture, repair and operation".
The system includes the following developed devices:
1). Device SC (Steel Control). Allows you to control and predict the quality of the magnetic circuit (a package of sheets of electrical steel) at the stage of production and repair of electric machines. Detects mechanical defects formed during the production and assembly of a new steel package, as well as violation of the insulation properties of sheets of electrical steel after winding the winding when repairing an electric machine. Allows detection of packets with high vortex currents due to broken inter-loop insulation, which leads to increased losses and overheating (up to the fire in the iron).
2). The device СT (Control of turns). Allows to control and predict the quality of coils, sections and windings of electric machines in the process of production and repair. Detects defects in the isolation of coils, sections and windings in assembly, due to mechanical damage during assembly; and the low quality of insulation, varnishes, welded and soldered joints. Detects both metal locks and undeveloped defects of inter-circuit isolation. The control is carried out with the provision of a checking bending voltage from 10 V to the turn (for multidirectional coils) and up to 200 V per turn (for large high-voltage machines).
3). The device IC (Isolation control). Allows to control and predict the quality of the main and inter-circuit insulation of windings of electric machines during operation (without disassembly in place of installation).
Detects linear and nonlinear defects of isolation of windings of an electric machine in assembly. By detecting hidden defects the residual life of the electric machine is projected. The control is carried out at providing the test voltage:
U check = 1000 + 2 U nom. (at U rated to 3000 V), 2.5 U nom. (for more than 3000 V at U) Tests are carried out using a non-destructive method. The action energy at the weakened insulation site is not more than 0.01 J.
Tests conducted are practically safe for maintenance personnel. Portable devices with power from the lighting network. The results of research can be issued to the consumer in the form of: -digital signal processing, oscillograms, digital and light indication, -sound signals.
The system guarantees control over the quality of production of electric machines at all stages of the assembly:
- control of the quality of the collected charged magnetic core (CMC),
- subsequent winding of coils (or formation of sections) (CT),
- after laying the winding in the grooves (CT),
- after the formation of the frontal parts (CT),
- after assembly of stator and rotor (with enclosed windings) (CT),
- after impregnation (CT),
- output control of the car in the collection (IC).
The tasks of the consumer of electric cars, the operator are solved with the help of the instrument IC.
The IC device combines simultaneously with such properties as high level of test voltage, high sensitivity of the system to manifestation of both linear and nonlinear defects and, at the same time, minimizes the energy of a special test pulse, which allows measurement to be carried out regularly and without detriment to the investigated electric machine
3. At the chair of Electromechanics, an actual development was made: Scientific-methodical support for the establishment of vibration diagnostics and monitoring systems for turbine units of nuclear power plants ", which was commissioned by the organization" Ukrautomenergobud ". Researches were conducted by prof., D.Sc. Shumilov Yu.A., Professor, D.Sc. Vaskovsky Yu.M., Associate Professor, Ph.D. Gaydenko Yu.A., Associate Professor, Ph.D. Tsivinsky S.S. The monitoring of the technical state of turbine generators and the detection of acquired damage is extremely important for ensuring high reliability of operation of power plants, especially atomic power stations. Among the known methods of diagnostics of damage, the method of vibration diagnostics is of particular importance due to its versatility and high sensitivity. Were developed:
• principles of construction and structure of vibration diagnostics and monitoring systems of turbine units of nuclear power plants;
• specification of a complex of hardware and computer computing devices included in the system of vibration diagnostics and monitoring;
• mathematical models, computer algorithms and programs for measurement, registration, computer processing and intelligent analysis of diagnostic parameters;
• technical suggestions and recommendations on the practical construction of vibration monitoring systems and monitoring of turbine units of nuclear power plants.
The results of the development were transferred to the interested organizations for further implementation.
Literature: 1) Титко А.И., Васьковский Ю.Н. Научные основы, методы и средства диагностики асинхронных двигателей, Наш формат, Киев, 2015, 300 с. 2) Васьковский Ю.Н., Коваленко М.А, Исследование и оптимизация устройства диагностики дефектов обмотки ротора короткозамкнутого асинхронного электродвигателя // Електротехніка та електроенергетика, №2, 2012, с.12 – 17. 3) Васьковский Ю.Н., Гераскин А.А. Вибровозмущающие электромагнитные силы в короткозамкнутых асинхронных двигателях при наличии повреждения их конструкции // Технічна електродинаміка №5, 2010, с.31-38.4) Васьковський Ю.М., Шумілов Ю.А., Чумак В. В., Штогрин А.В.Вібродіагностика та моніторинг турбогенераторів атомних електростанцій // Гідроенергетика України, №1, 2009, с.15 – 21.