Electric machines diagnosis techniques via transient current analysis

Induction motor condition monitoring has primarily relied on the analysis of currents during steady-state operation through the Fast Fourier Transform (FFT). Nonetheless, this conventional approach has many constraints, most of them related to the usual operation of most motors under situations differing from a pure stationary regime, or directly under transient conditions. Indeed, these situations are the most common in many industrial processes, a fact that reveals the necessity of developing techniques suited for the analysis of machine quantities during non-stationary operation. A vast work has been developed during these recent years in this area, raising many transient-based techniques being able to diagnose machines under transient conditions which furthermore overcome some of the drawbacks of conventional stationary analysis. Most of these techniques are based on the application of proper signal processing tools, especially adapted to analyze transient signals (time-frequency decomposition (TFD) tools). This paper carries out a review of the most significant techniques sustained on transient-analysis, grouping them in accordance to the nature of the TFD tool used in each case. The review intends to emphasize the most relevant contributions of each work and to serve as a useful reference to all authors involved in the area.