A Method for Incipient Interturn Fault Detection and Severity Estimation of Induction Motors Under Inherent Asymmetry and Voltage Imbalance

Electrical machines are essential parts of transportation systems. The reliability and availability of transportation systems can be significantly improved by the installation of diagnosis systems for these components. A critical challenge with the diagnosis process of electrical machines is to detect the incipient fault under the effects of inherent asymmetry and voltage imbalance. This paper addresses this problem, under the situation of stator winding interturn fault, by proposing a novel model-based approach. First, a model of asymmetric machines under fault is developed. The model analytically discriminates the effect of voltage imbalance, inherent asymmetry, and fault. Second, exploiting the developed model, a new diagnostic method, compensating the effects of both inherent asymmetry and voltage imbalance, thereby aiding in achieving incipient fault detection, is proposed. Third, as a result of the diagnostic method, a fault-dependent quantity, estimated using the measurements of only stator voltages and currents, is obtained. This quantity is a function of fault parameters, and hence, the method provides a solution to quantify the fault severity under the practical situation of unmeasurable fault parameters. In addition, a method has been envisaged for faulty phase identification. The theoretical development is supported by experimental results, where various fault severity levels and different load and voltage imbalance conditions are taken into account.