Analysis of Internal Short-Circuit Faults in the Stator Winding of a Nine-Phase Permanent Magnet Synchronous Machine Using Finite Element Analysis

Abstract

Safety-critical applications demand high levels of reliability and fault-tolerance from an electrical machine. In order to fulfill these requirements, the change from three-phase to multi-phase systems and the preferred use of permanent magnet synchronous machine is shown in ongoing research. In this paper, a comprehensive assessment of internal short-circuit faults is conducted on a nine-phase permanent magnet synchronous machine. A machine model including the considered short-circuit faults is implemented using finite element method to analyze the system behavior. Voltage, current, and torque characteristics are used for the analysis.In general, the assessment of different internal short-circuit faults shows that the impact of the fault rises with an increasing amount of shortened turns. The location of the short-circuit fault is also identified to have remarkable impact on the severity. Especially the currents in the affected phase exceed the nominal values, but increasing currents are also seen in the healthy phases. The star-connected (1x9)-phase machine has lower current peaks and torque ripples than the separately supplied (9x1)-phase machine. However, a major disadvantage of the (1x9)-phase machine is the electrical dependency among the phases. This leads to an imbalanced system once the short-circuit occurs. In contrast, the (9x1)-phase machine shows a lower impact of the fault on the remaining phases and a greater potential for future fault-tolerant control strategies.