Effect of Winding Phase-shifting on Low-space-harmonic Design in Six-phase Permanent-magnet Synchronous Machine

Fractional-slot concentrated windings (FSCWs) are widely utilized in six-phase fault-tolerant permanent-magnet synchronous machines (PMSMs). However, FSCWs cause abundant space harmonics of stator magnetomotive force (MMF) and increase the losses of the machine. In this article, in order to suppress the space harmonics of a six-phase PMSM, the six-phase winding is regarded as a combination of two sets of three-phase windings, and the effect of phase-shifting between two sets of three-phase windings on the MMF harmonic suppression is investigated. To achieve more effective suppression of the MMF harmonics, the low-space-harmonic oriented design is further extended to phase-shifting between double six-phase windings while the phase number is not doubled. A low-space-harmonic double-six-phase 15°-shifting winding is designed, in which both 1-pole-pair and 5-pole-pair MMF harmonics are suppressed, and its characteristics of losses, permanent-magnet (PM) torque, and reluctance torque are evaluated. A prototype of 24-slot/14-pole double-six-phase 15°-shifting PMSM is manufactured, and the experiments are ① carried out to verify the performance of the machine.