Abstract
Rotor electrical faults are an issue frequently encountered when applying condition monitoring and fault diagnosis on induction machines. The detection via the analysis of the stator current becomes challenging when the rotor cage suffers from multiple breakages at non-adjacent positions. In that case, electromagnetic asymmetries induced by the broken bars can be masked in such a way, that the diagnostic ability is highly likely to be obscured, thus leading to misinterpretation of the monitored signals' signatures. A new approach is proposed in this work to overcome this problem while the motor is at steady state. In this study, an industrial 6.6 kV, 1.1 MW induction motor is simulated with finite element analysis (FEM) and its electromagnetic variables are analysed and studied under healthy state and several faulty conditions. The analysis of the stator current and stray flux waveforms is executed in both the transient and the steady state and aims to diagnose the challenging cases where the rotor breakages are non-consecutive with regard to their spatial location. The results show the potential of flux analysis to fault severity regardless of the spatial position of the broken bars.
Highlights
Broken rotor bars do not always lead to direct failure of the induction machine, they can cause severe damage after longterm operation in industrial environments or EV applications, where motors undergo excessive load cycles [1,2,3,4,5,6,7]
Highly likely to be followed by a double breakage and/or broken end ring, broken bars are frequently compromised with misdiagnosis
The timevarying behaviour that is likely to be caused by the broken bar fault – and can be indicated by the corresponding time responses of the signals – are likely to appear in the spectral content with the help of a time-frequency method
Summary
Broken rotor bars do not always lead to direct failure of the induction machine, they can cause severe damage after longterm operation in industrial environments or EV applications, where motors undergo excessive load cycles [1,2,3,4,5,6,7]. One of the typical cases where misdiagnosis during a condition monitoring process becomes likely is at the presence of broken bars or end ring breakages at non-adjacent positions [2]. The phenomena that alter the behaviour of the machine during transient – where the FFT method fails to provide accurate information even on healthy machines – appear on the steady state In this case, the timevarying behaviour that is likely to be caused by the broken bar fault – and can be indicated by the corresponding time responses of the signals – are likely to appear in the spectral content with the help of a time-frequency method.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
