Abstract de la publi numéro 10830

This paper deals with mechanical fault diagnosis in induction machines from stator current measurements. Mechanical faults lead to amplitude or phase modulations on stator currents that induce different time-frequency signatures. However, the time-frequency representations apply on complex signals for a univocal phase and modulus definition. When modulation frequencies are lower than the carrier frequency, this complex signal is the analytic signal obtained through the Hilbert transform of the real measured signal. However, bearing faults, for instance, may produce high frequency modulations. An alternative is to obtain the complex signal through the Concordia transform that takes advantage of the additional information available using two of the three phases of an electrical machine. However, Concordia Transform requires the previous validation of a particular stator current model in three phase machine in case of mechanical faults. This paper uses a variable phase Fourier Transform for this model validation. Using the Hilbert and Concordia transforms of the proposed model, the Wigner-Ville distribution of low and frequency modulated signal is expressed. Finally, this paper applies the two transforms on simulated and experimental signals and provides a diagnosis of amplitude or phase modulation in various conditions.