Short-Circuit Current Reduction in Dual Three-Phase Permanent-Magnet Machine by Asymmetric Pitch for High-Reliability Applications

This paper proposes a short-circuit current (SCC) reduction method for dual three-phase (DTP) permanent-magnet machines by asymmetric pitch technique. The conventional DTP winding configuration with symmetric pitch is used as a benchmark. The above two windings are named as asymmetric and symmetric configurations, respectively. Firstly, the asymmetric configuration with physical isolation is introduced and distinguished based on the spatial distribution. Secondly, the stator magnetomotive forces generated by different configurations are analyzed, and the effects of asymmetric configuration on harmonic order and content are studied with emphasis. Afterwards, the SCC and braking torque of different configurations are analyzed and compared under fault condition. The asymmetric configuration has great significance to reduce the SCC and braking torque. Moreover, it exhibits comparable torque ripple compared to the symmetric counterpart, although with a reduction slightly in average torque. Finally, the 48-slot/8-pole DTP permanent-magnet machines with different configurations are manufactured. The experiments are conducted and compared to validate theoretical analysis and reliability improvement design.