Comparing the Performance of Parallel Multi-Phase Brushless DC Motors: A Comprehensive Analysis

Parallel multi-phase brushless dc motors (BLDCMs) are a strong candidate for use in aviation due to their high reliability and fault tolerance. We analyze and compare two types of parallel multi-phase BLDCMs—symmetric and asymmetric winding parallel multi-phase BLDCMs. First, this article proposes a structure and design method for the parallel multi-phase BLDCM with symmetric winding, which can expand the number of winding phases according to the application requirements and increase the torque density and system efficiency of the motor within the finite control complexity. Second, under the constraint conditions of equal copper consumption or equal phase current amplitude, the average torque of parallel multi-phase BLDCMs with symmetric and asymmetric winding under different conduction modes is analyzed. The system efficiency of the two types of motors at the same speed and load torque is compared. This article provides an evaluation criterion for the control system selection of parallel multi-phase BLDCMs. In addition, it also offers essential theoretical support for the current reconstruction and torque recovery index after the open-circuit fault. Finally, the nine-phase BLDCM and the triple three-phase BLDCM are used as prototypes in the experiment to verify the correctness of the theoretical analysis and the effectiveness of the method.