Analysis of Electrical Faults and Mitigation Strategies for Double-star Induction Machines

Abstract

Double star electric machines are renowned for their robustness, reliability and torque quality. However, despite these advantages, they are prone to various mechanical and electrical faults. This research investigates the impact of electrical faults on double-star induction machines (DSIMs), encompassing phase-open and inter-turn short-circuit failures in both stator and rotor windings. A real abc framework is employed, considering both connected and unconnected neutral configurations, to accurately model the behavior of the machine under healthy and degraded conditions. Simulation results reveal that open-phase faults (OPF) lead to current imbalances, torque fluctuations, and speed variations, which can be mitigated through an intentional adjacent second-phase opening. Additionally inter-turn short-circuit faults (ITSCF) severity is found to be highly dependent on fault resistance, influencing current distortion and electromagnetic disturbances. The results demonstrate that the suitable configuration of the neutral depends on depends on the fault type: connecting the neutral (CN) generally reduces the severity of OPF issues, whereas disconnecting the neutral (UNC) is more effective for mitigating stator ITSCF. These strategies effectively reduce disturbances and minimize torque and speed ripples, thereby maintaining optimal machine performance. Furthermore, detailed spectral analysis of DSIM signatures is performed, highlighting the complexities involved in fault diagnosis and emphasizing the importance of accurate fault identification for ensuring system reliability. These findings offer valuable insights into fault-tolerant strategies and DSIM reliability enhancement. This guarantees service continuity while keeping the main loads connected.