Diagnostics of Induction Motor Broken Rotor Bars on the Basis of the Electromotive Force Analysis

Under the conditions of increased energy resources consumption, the researchers around the world face the problem of rational energy use. One of the ways to solve this problem consists of introducing energy saving technologies into the operation of electrotechnical and electromechanical devices. The operation of electric machines (EM) is very often accompanied by the occurrence of various damages. It results in increased energy consumption, untimely failure of electromechanical systems and, consequently, growth of material expenditure. Operation efficiency of electric equipment can be improved due to timely diagnostics of EM damages at early stages of their development. It is for this reason that research in diagnostics of EMs containing induction motors (IM) is of special interest nowadays. Researchers succeeded in searching for efficient methods of IM diagnostics that are mostly suitable for particular conditions and modes of equipment operation. There are different methods for diagnostics of induction motor broken rotor bars. However, the analysis of conventional diagnostics methods revealed that most of them require the removal of the induction motor from the operation process and its disassembling. Presently, such methods of IM broken rotor bars diagnostics in operation modes such as methods of currents spectral analysis, the analysis of zero-phase sequence voltages, and the analysis of external magnetic field parameters are known. Nevertheless, these methods do not provide satisfactory results during diagnostics under a no-load condition and do not take into account that low-quality voltage of the supply network and the fluctuation of load level influence the diagnostic results. Besides, the results of the Fourier transform of current signals does not allow for unambiguous identification of the number and relative position of IM broken rotor bars. Hence, the development of the method for diagnostics of IM broken rotor bars is a topical scientific and applied problem. A method for diagnostics of IM broken rotor bars on the basis of the analysis of electromotive force (EMF) in the stator windings is presented in the monograph. To research IM as a diagnostics object, the circuit mathematical models and those related to the final element method have been developed. The efficiency of the use of the wavelet analysis of the EMF signal in the stator windings under IM self-running-out condition has been demonstrated. A method for EMF signal decomposition with the use reverse z-transform theory has been proposed to improve the reliability of damaged diagnostics. The presented monograph contains theoretical and experimental research that made it possible to solve the topical scientific problem of improving the efficiency of IM broken rotor bars with the use of the signal of electromotive force wavelet analysis in the stator windings under the motor self-running-out condition.