The zero-sequence current spectrum as an on-line static eccentricity diagnostic mean in Δ-connected PSH-induction motors

It has been reported that the only-static and only-dynamic eccentricity cannot be reliably detected in induction motors which produce Principal Slot Harmonics (PSH) with the use of the traditional MCSA method. Most work was focused in the detection of dynamic and mixed, rather than static eccentricity. In this paper, the detection of the only-static eccentricity fault in Δ-connected induction motors with the use of the zero-sequence current spectrum is thoroughly investigated. The frequency spectrum of the zero-sequence current is studied with the application of the Fast Fourier Transform in a PSH-induction motor operating under different constant speed cases and for different fault levels. The work is carried out with transient FEM simulations. The results will show that the proposed method succeeds in the only static eccentricity diagnosis and its severity, while the MCSA proves to be unreliable.