Investigating Direct Torque Control of Six-Phase Induction Machines Under Open Phase Fault Conditions

This paper presents analysis and evaluation of classical direct torque control (DTC), for controlling a symmetrical six phase induction motor (SPIM) under open phase fault conditions. The machine has two three-phase windings spatially shifted by 60 electrical degrees. The strategy of the proposed method consists of choosing the switching modes according to the configuration of living phases in such a way that it generates vectors that have higher amplitude in α-β plane while their projections on z axis give zero or near zero amplitude vectors. The goal is reducing parasitic currents and torque ripples of SPIM under faulty mode. Based on the theoretical analysis, it will be shown that in the open phase fault conditions, the only non-pulsating operation is obtained by opening the fault three-phase winding. Experimental test results are provided o support theoretical analysis in open phase fault conditions for SPIM.