Optimal torque control of PMSMs with redundant stator coils in case of open circuit faults

A fault of the coils or the inverter of a permanent magnet synchronous machine (PMSM) can yield a potentially dangerous behavior. To allow for an operation even in this case, PMSM constructions with redundant stator coils and inverter legs have been proposed in literature. This paper describes a method to systematically determine optimal coil currents for the torque control in the case of an open circuit fault of stator coils or inverter legs. It is capable of systematically incorporating magnetic nonlinearity and non-fundamental wave behavior of the PMSM. It is further shown that this method can be extended to calculate optimal currents which are superposed to the torque generating currents and which allow for sensorless position estimation by signal injection at stand-still or low rotor speed.