Design and Optimization of a Halbach Consequent-Pole Permanent Magnet Machine for Rim-Driven Thruster

In this paper, a three-segment Halbach consequent-pole permanent magnet rim driven machine (HCPM-RDM) with unequal pole arc lengths is proposed to address the issue of low utilization of permanent magnet (PM) in rim driven thruster (RDT) operating under large air gap requirements. The key focus is on the strategic combination of the Halbach array's PM pole arc coefficient, internal pole ratio, and magnetization angle to enhance the flux focusing effect, thereby suppressing flux leakage and utilizing its self-shielding capabilities. In addition, the impact of the key rotor parameters on the air gap magnetic field is analyzed through finite element analysis (FEA). To improve the efficiency of the design process, a multi-objective stratified optimization strategy is employed, wherein the four optimization objectives, namely output torque, loss, torque ripple, and cogging torque, are categorized into two levels for optimization. Through combining different optimization methods, the objective functions of the two levels are optimized. Comparative analysis between the proposed machine and conventional machine is conducted using FEA. The results indicate that the proposed HCPM-RDM exhibits higher torque output, efficiency, and lower torque ripple.