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 in MATLAB, 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.