Offline Interturn Fault Diagnosis Method for Induction Motors by Impedance Analysis

In this paper, a new offline interturn fault (ITF) diagnosis method for induction motors is presented. The proposed method is based on impedance imbalance in the stationary d-q plane. First, to show the impedance imbalance, an induction motor model is presented with an ITF circuit loop and fault resistance. Then, six impedance components in the stationary d-q plane are defined, depending on the excited phase windings. With fast Fourier transform (FFT) filtering applied to the six impedance components in the d-q plane, the second-order impedance magnitudes are obtained. From the magnitude, the ITF and the faulty phase can easily be detected. Moreover, a specific faulty winding among the faulty phase windings can be identified. To verify the proposed method, finite-element analysis (FEA) and experimental results are presented for an induction motor having an ITF.