Zero-sequence flux analysis aiming for reliable detection of broken rotor bars in induction motors

Rotor electrical faults may appear in induction motors. Typically, this fault evolves at a slow rate, thus making it prominent for early detection. However, it has been shown that multiple breakages at non-adjacent positions may not create signatures when the MCSA is applied. Although the analysis of the stator current during the start-up transient can reveal this fault reliably, there are several industrial applications where the motors do not experience frequent start-ups making such methods obsolete. This paper addresses this need, that of detecting the fault reliably at steady state. The authors have utilised the zero-sequence stray flux and show that this methodology can identify the fault independently from the stator winding connection to the supply or the size and geometry of the motor.