Diagnosis of eccentricity based on the Hilbert transform of the startup transient current

The Hilbert Transform (HT) can improve the resolution of motor current signature analysis (MCSA), especially at very low slip, because it converts the supply frequency into a continuous component, which can be easily removed to better detect fault harmonics. This paper proposes its application also during speed transients, with two key advantages: first, it allows an easy filtering of the transient current component corresponding to the supply frequency, and, second, the HT allows for the generation of the Hilbert Spectrum, as a replacement of the Fourier Spectrum in the case of non-stationary signals, like those that appear in a transient regime. The performance of the proposed method is compared with other methods as the Discrete Wavelet Transform (DWT), and is validated through simulation with a mathematical model and experimental analysis of a 1.1 kW three-phase squirrel-cage commercial induction motor with eccentricity.