Advanced Monitoring of Rotor Broken Bar in Double Squirrel Cage Induction Machines Based on Wavelet Analysis

The diagnosis of induction machine faults is commonly realized through Motor Current Signature Analysis (MCSA), i.e. by classical spectrum analysis of the input currents. In case of large or double cage induction motors, rotor broken bars fault detection based on sideband current components may fail due to the presence of inter bar currents that reduce the degree of rotor asymmetry, leading to reduced relevance of these spectral components. But inter bar currents produce core vibrations in the axial direction, which can be detected using vibration analysis techniques, in order to overcome the limits of the classical MCSA for these purposes. In this paper, an advanced use of the Discrete wavelet Transform (DWT) is proposed to overcome the limitation of the classical approaches based Fourier Analysis (FA). The developed approach is best suited for automotive or high power traction systems, in which safe-operating and availability are mandatory. Experimental results show the validity of the developed technique, leading to an effective diagnosis procedure for broken bars in induction machines.