Fault tolerant three-phase ac motor drive topologies: a comparison of features, cost, and limitations

This paper compares the many fault tolerant three-phase ac motor drive topologies that have been proposed to provide output capacity for the inverter faults of switch short or open-circuits, phase-leg short-circuits, and single-phase open-circuits. Also included is a review of the respective control methods for fault tolerant inverters including two-phase and unipolar control methods. The output voltage and current space in terms of dq components is identified for each topology and fault. These quantities are then used to normalize the power capacity of each system during a fault to a standard inverter during normal operation. A silicon overrating cost factor is adopted as a metric to compare the relative switching device costs of the topologies compared to a standard three-phase inverter. Index Terms--Inverter faults, phase-leg short-circuits, silicon overrating cost factor (SOCF), single-phase open-circuits, three-phase inverter, three-phase ac motor drive topologies.