Analysis of Stray Flux Spectral Components in Induction Machines under Rotor Bar Breakages at Various Locations

Abstract

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On the broken rotor bar diagnosis using time–frequency analysis: ‘Is one spectral representation enough for the characterisation of monitored signals?’

“…Nevertheless, a machine operating under the existence of a fault is practically operating in time-varying conditions [51][52][53][54]. In the case of SFSA, these time-varying conditions' periodicity is designated according to the fault periodicity over the rotation of the rotor and the continuous induction of electromagnetic quantities from the stator to the rotor and vice-versa [28,[52][53][54]. Such periodicities are not always easy to track through the frequency spectra; therefore a time-frequency representation -where they are translated on a spectrogram as modulations, as demonstrated in Figs.…”

“…Such periodicities are not always easy to track through the frequency spectra; therefore a time-frequency representation -where they are translated on a spectrogram as modulations, as demonstrated in Figs. 4 and 5 -provides clearer indications for the fault condition on the pipeline for a diagnostic decision, in cases where using the classical FFT like the MCSA might fail to do so due to loss of diagnostic information, as explained in [53][54][55].…”

“…On the other hand, a t-f representation without system oriented fine tuning of parameters -which in this case relate to the slip and sampling frequency -might also result in information loss. It should also be noted that the approach of this system oriented parameter tuning can be used for t-f process like the ones described in [32][33][34] or [53][54][55][56][57] as an initialisation pre-setting and finetuning; it is also eligible to define the two extreme limits where these methods or similar types of analyses can be tested, when aiming to extract different pieces of information in two stages. At one of these extremes shown in Fig.…”

“…Nevertheless, a machine operating under the existence of a fault is practically operating in time‐varying conditions [51–54]. In the case of SFSA, these time‐varying conditions’ periodicity is designated according to the fault periodicity over the rotation of the rotor and the continuous induction of electromagnetic quantities from the stator to the rotor and vice‐versa [28, 52–54].…”

Rotor Fault Detection in Induction Motors Based on Time-Frequency Analysis Using the Bispectrum and the Autocovariance of Stray Flux Signals

“…Stray flux analysis is adequate to avoid occasional false indications appearing when other techniques are applied to rotor fault detection [10]. Moreover, the suitability of stray flux analysis for non-adjacent bar breakage detection has been explored in [11,12]. Regarding statistical analysis using stray flux signals, an algorithm has been proposed in [13] that relies on the use of the mean value and the standard deviation of the spectral components.…”