Stator Imbalance in Asymmetrical Six-Phase Synchronous Motor Drives: High-Resistance Connections and Mismanufactured Winding

An electric drive can experience a wide variety of faults. Some of them, such as short circuits, can significantly harm the structural integrity of the drive. Others, such as poor connections or manufacturing asymmetries in the stator winding, might not affect the drive integrity but distort the electrical quantities (voltages and currents), causing overheating and imbalances. Improper connections could lead to resistance imbalance, while bad manufacturing may result in some phases having fewer or more turns than expected at the design stage. An analytical approach based on the Vector-Space Decomposition (VSD) is proposed in this paper to model the imbalance resulting from High-Resistance Connections (HRCs) or Manufacturing Defects (MDs) due to a variation in the number of turns.The study is carried out for a six-phase surface-mounted permanent magnet (SMPM) brushless motor, but it may be extended to any multi-three-phase drive. Finite-element simulations are used to build a realistic model of the electrical machine and confirm the theoretical outcomes.