Analysis of the Fault Tolerance of a Switched Reluctance Machine with Distributed Inverter

This paper analyzes how distributed inverters can further increase the fault tolerance of switched reluctance traction drives. The drive under investigation is an outer-rotor direct-drive switched reluctance machines (SRM) for railway traction. The phases of SRMs are magnetically and to a certain extend electrically decoupled. Hence, in case of a fault inside a phase, the remaining phases can continue operation with reduced power. With the distributed inverter concept at hand, each coil of a phase is excited by its own modular inverter. This increases the redundancy, simplifies integration of machine and inverter, and enables a new degree of freedom regarding the control of the machine. Especially for electric drives used in railway traction or electric vehicles, redundancy avoids all the inconveniences of a standstill in case of a fault, enabling a so-called limp home capability. This paper shows, how open- and short-circuit faults of single coils or modules of the proposed drive influence average torque, torque ripple, and noise and vibration. Therewith, it will be shown that with the SRM and the distributed inverter it is possible to continue operation in case of the analyzed faults.