Analysis of torque characteristics in dual three-phase PMSMs with asymmetric IPM rotors

In this paper, the effects of asymmetric interior permanent magnet (AIPM) rotors on the torque characteristics in dual three-phase (DTP) permanent magnet synchronous machines (PMSMs) are investigated. The electromagnetic performances of DTP PMSMs with symmetrical and asymmetric IPM rotors are compared, including air-gap flux density, back EMF, cogging torque, torque, loss, and efficiency. It is found that in DTP PMSMs, the AIPM rotor can achieve significant torque improvement under both healthy and single three-phase open-circuit conditions. It is also found that performance enhancement in AIPM DTP machines is more remarkable across the constant torque region, particularly at high-load conditions, than in the constant power region, compared with the symmetrical IPM counterpart. A prototype is fabricated and tested to verify theoretical analyses.