Transient envelope current analysis for inter-turn short-circuit detection in induction motor stator

Electrical machines are subject to faults which, depending on the type and importance of the plant, can cause material, economic and social damage. The reliability required for electric motors constantly grows due to the importance of their applications and technological advancement. One of these possible faults is an inter-turn short circuit of the stator winding. This is a very severe failure because its evolution to a worst fault is very fast. Thus, the initial detection of the inter-turn short circuit is of fundamental importance to avoid further damage to the motor. Steady-state analysis is not adequate when applied in some cases, such as unloaded machines, loads with oscillating torque and power with voltage fluctuations. The present work brings a new study of the transient current to analyze the beginning of inter-turn short circuits in the induction motor stator windings. The proposed methodology extracts the second component from the transient envelope of the motor starting current signals by principal component analysis. These components reflect the asymmetry caused by the initial short circuit and carry the desired fault information. By variance analysis it becomes possible to monitor the evolution of a short-circuit fault. Numerical and experimental signals are provided to validate the effectiveness of the novel technique.