Analysis of Dual 3-Phase Fractional-Slot Concentrated Winding PM Synchronous Machines with Different Angle Displacements

In this paper, the non-conventional angle displacement between two sets of 3-phase windings will be analyzed and compared for the dual 3-phase fractional-slot PM machines with non-overlapping windings. Firstly, all feasible angle displacements between two sets of 3-phase windings are discussed in general for various slot/pole number combinations. Then, a dual 3-phase 24-slot/22-pole PM machine with different angle displacements (i.e. 0/15/30 deg.) is selected as an example for further in-depth investigations. It shows that under healthy condition, the electromagnetic performances of the 15 deg. angle displacement are comparable to those of the conventional counterparts. Furthermore, under 3-phase open-circuit (OC) condition, the 15 deg. angle displacement suffers less from the cross-coupling saturation effects, and thus better over-rating capability than the conventional angle displacements. Moreover, it is also found that the proposed 15 deg. angle displacement has better PM irreversible demagnetization withstand capability under 3-phase OC condition. All the theoretical analyses are verified by FE analyses on a dual 3-phase 24-slot/22-pole surface-mounted PM (SPM) machine.