Reliable detection of rotor bar failures in induction motors operating in petrochemical plants

Reliable Detection of Rotor Winding Asymmetries in Wound Rotor Induction Motors via Integral Current Analysis

“…Note the clear presence of the V-pattern caused by the LS in the startup current [8,23] for the faulty cases; in healthy condition, the pattern is much less evident since the LS has lower amplitude. This is ratified when computing the quantification indicator based on the DWT [12,15] (evidence 4); Table I shows the values of the indicator  DWT for different cases tested. Note the value of the fault indicator sensibly decreases when the level of asymmetry increases showing variations of more than 20 dB between healthy condition and medium asymmetry level.…”

“…Nonetheless, in past works, it was proven that the two previous evidences were not enough to confirm the presence of rotor failures in cage induction motors; this was due to the fact that there are some situations where other harmonics that are not related to the fault can be misinterpreted as fault components; these situations can lead to false positive indications [7][8][9][10][14][15]. In other cases, although the fault is present, the amplitudes of the previous components may be low or they may not be easily assessable, a fact that can lead to eventual false negative indications [8,11,13].…”

“…For instance, some works propose the startup analysis and the identification of this pattern to discriminate between load effects and rotor damages in cage motors [8,28]. On the other hand, the fourth evidence is based on the computation of the fault severity indicator based on the DWT of the startup current [12,15]. This indicator ( DWT ) is given by expression (3) and relates the energy of the total current signal (i) with that of the wavelet signal containing most of the fault component evolution (d).…”

“…motor startup current) has been proposed. This new approach was conceived to avoid some drawbacks of MCSA, such as its eventual false diagnostic indications (either false positives or negatives) that may rise for certain motor constructive characteristics (presence of rotor cooling ducts, motors with double cage rotors, anisotropic rotor cores…) or operating conditions (load torque oscillations, no-load conditions, …) as well as its unsuitable application under varying speed conditions [7][8][9][10][11][12][13][14][15][16].…”

Comparison of different wavelet families for broken bar detection in induction motors

“…This approach enables avoiding some drawbacks of the classical Motor Current Signature Analysis (MCSA) that is the most widespread technique in industry for the evaluation of the rotor condition [4]. For instance, this novel diagnosis trend avoids some frequent erroneous diagnostics provided by the classical MCSA, as the eventual appearance of false positive or false negative indications [5][6][7]15]. Within this transient-based methodology, the analysis of the start-up current has drawn a considerable interest.…”