On the Frequency Dependence of Harmonic Current Side-Band (HCSB) based Rotor Fault Indicators for Three-Phase Cage Machines

Inverter-fed cage induction motors can run at variable frequency and speed, and the diagnostic techniques to be applied for these motors must take in account frequency variations. Especially in variable frequency railway traction drives, bar breakage problems have been reported as a consequence of large sixth harmonic torques produced by the non-sinusoidal feeding. MCSA can be applied for motor diagnostics in these cases, but suitable indicators must be used for reliable fault severity assessment. Harmonic current side-band (HCSB) based Indicators (HCSBIs) for broken bars detection present a good rejection to frequency variations, as well as to motor load level, drive inertia, and motor parameters. In this paper, three industrial motors with broken bars have been tested for HCSBIs performance evaluation with different feeding frequencies, and the results have been reported and discussed.