Induction Motor Low Frequency Torque Oscillation Diagnostics Through Circuit Breaker Acquisitions

Insights on the diagnostics of load oscillations in induction motors are presented in this work, where the torque
anomalies are detected analyzing both current and voltage signals acquired through a smart circuit breaker meant for protection purposes. Featuring high sampling frequency and enough acquisition time, the spectra obtained from the protection device measurements is accurate enough to highlight the characteristic harmonics occurring in load condition. The Low Frequency Oscillation Torque (LFTO) anomaly is then
investigated at different frequencies and shapes, and the resulting spectra are examined seeking for specific patterns. Considering the voltage spectrum, a characteristic pattern is identified when LFTOs take place. This finding proves the promising diagnostic capability of the circuit breakers' latest generation.