Detection of Broken Shafts in Induction Motors Using Inrush Current Analysis

Induction motors play a vital role in industrial applications, but their reliability is often affected by shaft failures, leading to unstable torque and altered current waveforms during startup. This study analyzes 42 industrial slurry mixer motors (187 kW, 743 rpm), identifying broken shafts in 17% of cases, with others showing wear, discoloration, or cracks. Motors with shaft failures exhibited a distinct triple V-line pattern in the inrush current, while rotor faults showed a single V-line. Torque and vibration spectrum analysis further validated shaft defects, revealing characteristic peaks at 100 Hz and 112 Hz. Post-repair analysis confirmed a reduction to a single V-line in re-machined shafts, demonstrating the method’s sensitivity to mechanical integrity. These findings establish the V-line technique as an effective tool for early fault detection, enhancing predictive maintenance and improving overall motor reliability.