Prediction of the mass unbalance of a variable speed induction motor by stator current multiple approaches

Abstract

Generally, rotor mass unbalance is one of the most probable causes of the majority of degradations sufferedby electric drives in an industrial environment (current pumping, rolling problem, misalignment, etc.), especially thosewith high power and variable speed. This document is an experimental contribution to the reliable detection of massunbalance and changes in its severity if, by necessity of service, the system is subjected to a speed variation. Theimplementation of the technical orbits Park, strengthened by the application of the Fourier transforms (FFT, STFT) tothe Park vector of the stator current allowed the identification of the unbalance defect at low frequency. The sequenceof current analytical approaches favors the convergence towards an unambiguous reading of the mass unbalance defect.A comparative table has been drawn up in order to observe the evolution of the gravity of this mechanical defect in thecase of a speed variation of the induction motor. The results obtained by this multifaceted approach are very satisfyingand can contribute to a self-diagnostic with the assistance of a decision-making technique.