Detection of Rotor Faults in Squirrel-Cage Induction Motors using Adjustable Speed Drives

The need for detection of rotor faults at an earlier stage, so that maintenance can be planned ahead, has pushed the development of monitoring methods with increasing sensitivity and noise immunity. Addressing diagnostic techniques based on current signatures analysis (MCSA), the characteristic components introduced by specific faults in the current spectrum are investigated and a diagnosis procedure correlate the amplitudes of such components to the fault extent. In this paper, the impact of feedback control on asymmetric rotor cage induction machine behavior is analyzed. It is shown that the variables usually employed in diagnosis procedures assuming open-loop operation are no longer effective under closed-loop operation. Simulation results show that signals already present at the drive are suitable to effective diagnostic procedure. The utilization of the current regulator error signals and the influence of the regulators gains on their utilization in rotor failure detection are the aim of the present work. The use of a band-pass filter bank to detect the presence of sidebands is also proposed in the paper.