Diagnosis of Rotor Asymmetries in Inverter-fed Wound Rotor Induction Machines via PSH Analysis of Start-up Vibration

Wound Rotor Induction Machines (WRIMs) are widely utilized in industrial applications with high starting torque. The rotor health of such machines influences the machine efficiency and ultimately, the overall safety and reliability. The monitoring of the housing vibrations represent a highly available manner of holistic diagnosis. Nevertheless, the evaluation of rotor health through vibration signals primarily focuses on steady-state operation and has received limited investigation when compared with electrical signature analysis. The present paper introduces a novel technique to diagnose rotor winding asymmetries in WRIMs by analysing the transient evolutions of Principal Slot Harmonic (PSH) families. Particularly, an inverterfed start-up is analysed, which poses increased challenges for rotor defect diagnosis when compared to the line-fed scenario. The methodology exploits the resonance phenomena that arises from the interactions of time evolving forces and structural frequencies. The automatically extracted energy profile of the objective components provides adequate diagnosis and severity identification of three different asymmetry levels at rated load conditions.