Evaluation of Magnetomotive Force and Torque Ripples in Modular Type IPMSM With Multi Three-Phase Winding Configurations

Electrical machines having more than one independent three-phase unit are mostly proposed for applications that require the machine to operate continuously, even under one or more three-phase units fault. This paper discusses the concept of multi three-phase unit motor machine design in which the machine stator is divided into multiple three-phase units, with three stator slots and a rotor pole pair constituting a single independent three-phase unit motor. Firstly, an analytical method is presented to calculate the magnetomotive force (MMF), its harmonic spectrum and their impact on the machine torque ripples for the multi three-phase unit motor machine model. The proposed algorithm can be used to study the MMF and torque ripples behaviour of any multi three-phase unit motor machine operating under healthy and open-circuit fault operation. Moreover, different multi three-phase winding configurations including multi three-phase concentrated, multi three-phase distributed and multi three-phase mixed concentrated and distributed winding configuration are investigated for the modular type machine prototype. The analyzed multi three-phase winding configurations are fully studied to investigate the MMF harmonic components, the generated torque and torque ripples under healthy and open-circuit fault operations. The performance analysis of the prototype machine is investigated using detailed Finite Element Analysis (FEA) under the analyzed multi three-phase winding configurations, validating the effectiveness of the proposed multi three-phase unit motor machine windings configurations. This study presents useful conceptual hints for the multi three-phase unit motor machine design, while the analyzed three different types of winding configurations can help machine designers select the best multi three-phase winding design approach with lower generated torque ripples and lower unbalanced magnetic forces, particularly under different unit motors open-circuit fault operating conditions.