On-Line System for Fault Detection in Induction Machines Based on Wavelet Convolution

Abstract

Motor Current Signature Analysis has been successfully used in induction machines for fault diagnosis. The method however does not always achieve good results when the load torque is not constant. For proper results temporal analysis on determined frequency harmonics is needed. This paper proposes an automatic system for fault analysis based on wavelet functions, which allows on-line fault detection on time domain achieving good experimental results on stationary and non stationary state.

Broken Bar Diagnosis for Squirrel Cage Induction Motors Using Frequency Analysis Based on MCSA and Continuous Wavelet Transform

“…In addition, the SNR should be high in the data acquisition process to avoid frequency distortion in the spectrum, allowing accurate harmonic component evaluation. However, the motor study when it is operating at low frequencies needs a high-resolution spectral analysis, which leads to signal acquisition over long time periods, increasing the fault diagnosis time [2,4,27] and requiring an improvement in the software and hardware used for signal acquisition.…”

“…Due to its similarity to the current signal, the Morlet mother wavelet is used to apply the CWT to the current signal, which generates greater accuracy in the analysis. The Morlet mother wavelet is shown in Figure 1 and it is computed as follows [25][26][27]:…”

“…Conversely to FFT transform, the wavelet transform can extract the signal characteristics in time and frequency domains [24]. Based on the wavelet properties, different types of mother wavelets can be used to perform the analysis [25][26][27]. The wavelet transform is considered a useful tool for applications where signal feature extraction is required (e.g., pattern recognition, machine learning, and classifiers) [19,20,[28][29][30][31].…”

“…Conversely, non-orthogonal wavelet analysis by means of Morlet-CWT, where an arbitrary scale set can be used to build complete spectral graphs. In this regard, the analysis of current signals through CWT generates detailed information in the time-frequency spectrum [27]. The Morlet-CWT signal processing technique applied for detection of broken bars in electric machines is used to represent time-domain motor current signals in the time-frequency spectrum.…”

“…The aforementioned techniques use the Motor Current Signal Analysis (MCSA) as a common method to acquire the current signals from the induction machine [2,27,34]. The MCSA is a widely used method for monitoring failures in induction motors [10,23,34] (e.g., rotor and winding faults [18,35,36]).…”