Modeling of Three-Phase Induction Machines Under Combined Inter-Turn Fault and Mechanical Eccentricity

Fault modeling in induction motors is suitable for analyzing operational characteristics, enabling simulation of transient and steady-state phenomena, and facilitating the development of control systems that can extend their operational life. Therefore, this work presents a hybrid model of a three-phase induction machine simultaneously subjected to an inter-turn short-circuit fault in one of the stator phases and to mechanical eccentricity. The mathematical formulation is developed in the dq reference frame, encompassing the electromagnetic and mechanical equations, with parameters derived from finite element analysis. The developed equations were simulated inMATLAB, considering direct-on-line starting and step-load application, and the torque was validated using the finite element software FEMM. Even for small eccentricities (20% static, 10% dynamic) and a few shorted turns (2.08%), the three-phase currents became unbalanced in both amplitude and phase. The fault current clearly indicates potential for damage and rapid propagation of the inter-turn fault. A pulsating torque component at nearly twice the supply frequency was also observed, attributed to the negative-sequence current.