Torque production improvement of a five phase fractional-slot PM machine under faulty operation

The paper deals with several approach to recover the torque production capability of a five phase double-layer fractional-slot PM machine under faulty operation. The considered fault is an open-circuit coil in a given phase. The application of the star of slots approach has led to three locally grouped coils per phase, which represents a crucial benefit with respect to their re-arrangement in case of a failure. In a first step, the mean futures, such as the phase back-EMFs and the electromagnetic torque, are computed by FEA under healthy operation, and are taken as references. Then, they are investigated, under a faulty coil, for different approaches to recover the torque production capability. These concern (i) the re-arrangement of the armature winding, and (ii) the readjustment of the machine current supply. A comparison of the potentialities of the torque recovery approaches has clearly highlight the superiority of the one consisting in the re-adjustment of the current initial phases, in an attempt to equilibrate the resulting air gap MMF.