Detection of Broken Rotor Bars in Induction Machines through the Study of the Startup Transient via Wavelet Decomposition

Abstract

This paper introduces a new method
for the diagnosis of rotor bar breakages in
induction machines based on the application of the
Discrete Wavelet Transform (DWT) to the startup
stator current. Firstly, an explanation of the
physical basis of the phenomenon is given; It is
remarked the occurrence of a stator current
harmonic with a particular frequency variation
during the startup process, when a rotor bar
breakage has happened. Afterwards, it is
introduced a method for detecting this harmonic
by means of the DWT. This method is based on the
characteristic pattern produced by the harmonic
on the high-level wavelet signals resulting from the
startup current decomposition. This pattern is
illustrated using a numerical model of an induction
machine which allows the simulation of the startup
process of a machine in healthy and faulty
conditions. Finally, the proposed method is
experimentally tested using a laboratory machine
which easily allows the operation under different
fault conditions.