Influence of misalignment of connection of electrical machine shafts on the nature of electric power of the induction motor

Purpose. To identify the vibration power components caused by misalignment of electrical machine shafts in the instantaneous power of the induction motor. Methodology. The power components of the induction motor are analytically determined taking into account the power caused by torque vibrations on the shaft. Based on this, using the methods of mathematical modelling in the visual programming environment, the known model of a three-phase induction motor with a short-circuited rotor has been made. In addition, elements and connections are introduced which realize the formation of the moment caused by the imbalance of rotating masses. Using Fourier transform of the electric power of the induction motor, we determine its discrete spectrum. Experimental research is conducted on the electric power of the induction motor with a short-circuited rotor, in similar model conditions, on laboratory equipment. With the use of a virtual device synthesized in the LabVIEW package, the wavelet analysis of stator electric power of the motor of laboratory electrotechnical complex is performed. Findings. Differential equations of the induction motor with a short-circuited rotor in abc coordinate system are obtained, which reflect the distribution of instantaneous power in the machine taking into account the vibration moment. As a result of modelling according to the specified equations of the induction machine, in the conditions of full symmetry of parameters of the scheme and the mode with eccentricity of rotating masses, low-frequency vibrations of electric power of a stator with frequency of 25 Hz have been found. Similar results were obtained as a result of wavelet analysis of the electric power of an induction motor of a laboratory electrotechnical complex. Originality. Rationality of use of instantaneous electrical power of induction motor stator for detection of vibration caused by misalignment between its shaft and the shaft of another machine has been substantiated, which allows detecting vibration without complex methods of measuring vibration displacement and its derivatives. Practical value. Detecting vibration by measuring the electrical parameters of the stator circuit of the induction motor and determining the vibrations of its instantaneous power without the use of specialized equipment significantly simplify the procedure of vibration diagnostics at its early stages.