Detection of rotor faults in torque controlled induction motor drives

In the supervision of electrical equipment, the task of diagnostic system is to detect an upcoming machine fault as soon as possible, in order to save expensive manufacturing processes or to replace fault parts. An important issue in such effort is the modelling of the induction machine (IM) including rotor bar and end-ring faults, with a minimum of computational complexity. In this paper, a simpler method is employed in the simulation of an induction motor with rotor asymmetries. Simulation of classical and dynamic space vector models, Finite Element Analysis and experimental results are presented to support the proposed model. The need for detection of rotor faults at an earlier stage 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 correlates the amplitudes of such components to the fault extent. The impact of feedback control on asymmetric rotor cage induction machine behavior is also 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 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.