Assessment of Fault Harmonics in Squirrel Cage Induction Motor

Abstract

Squirrel Cage Induction Motor (SCIM) is a perceptive device as its failure has devastating effect due to loss in performance and reliability of power system. This makes constant supervising of SCIM imperative. Harmonics are responsible for many nuisances. Yet, it is one of the eminent parameter of fault recognition in stator current of IM. When motor condition deviates from healthy one, the behaviour of these harmonics changes significantly. Substantial variation is attained in frequency bands about fundamental frequency by presence of extra signature in the signal. The trait of harmonics in a current signal is different for different load conditions for particular motor circumstances. In this paper, Fourier transform technique is used for spectral estimation. It provides the frequency-amplitude representation of the signal which enlightened about the magnitude of each frequency present in signal. The normalised graphical analysis shows that harmonics during the fault has substantial variation from healthy conditions. The work achieved the purpose of understanding and identifying irregularities in harmonics and the conclusion drawn from the test validates that the behaviour of odd harmonics is largely irregular for different load conditions. Also some important deductions by analysis are taken for further fault detection analogies.