Research On A Dual-three-phase Fault-tolerant Permanent Magnet Synchronous Motor

Compared with other multiphase machines, dual three-phase machines areable to take advantage of off-the-shelf three-phase inverters. Though the outputtorque decreases under post-fault conditions, the post-fault control strategies ofthem are simple, and their post-fault performance is steady. Therefore, the marketof dual three-phase machines is promising in the future. In this paper, the designprinciple, operating characteristics, saturated inductance characteristics andthermal behavior of the dual three-phase machine are investigated.Firstly, the winding arrangement and slot-pole combination of the dualthree-phase machine is analyzed. The performance of different schemes iscompared, and the optimal scheme of winding arrangement and slot-polecombination for the dual three-phase machine is proposed. Moreover, the machineadopting the proposed scheme is designed.Secondly, particular effort has been made to analyze the inductancecharacteristics when partial saturation occurs. The power density of the machinedesigned in this paper is relatively high, thus it is possible that partial saturationoccurs in the machine during operation. An accurate and conventional calculationmethod of the saturated inductance is provided in this paper based on the freezingpermeability method and FEA software Flux.Thirdly, operating characteristics of the dual three-phase machine underhealthy conditions is analyzed. The possible fault terms of the machine issummarized. The analytical expressions of the transient processes of the dualthree-phase machine are deduced when encountering short-circuit faults Theexpressions of current and output torque are derived. Comparing with conventionalconstant magnetomotive force, the advantage of the dual three-phase machine issignificant.Finally, the inner heat exchange theory of the dual three-phase machine iselaborated, and the thermal behavior of it in steady state is analyzed. The prototypemachine is tested, and the errors between the experimental results and simulati onresults are rather small, which rank within the tolerant scope. The effectiveness ofthe theoretical analysis and simulations is validated by the comparison.