Detection of broken rotor bars in non-linear startups of inverter-fed induction motors

Fault detection in inverter-fed induction motors operating in non-stationary regimes it is still a challenge. In the case of rotor bar breakages, the fault-related harmonics evolve in the time-frequency plane very close to the fundamental component, and with much lower amplitudes than the fundamental. These two facts make their observation difficult. The Dragon Transform here presented is developed to solve this problem. In this paper, this transform is tested with non-linear standard inverter-fed startups, where, thanks to its high time-frequency resolution, is capable of detecting fault harmonics even with evolutions extremely close to the main component.