Design and Evaluation of Dual Excitation Permanent Magnet Linear Machine With Optimal Utilization of Extended Working Harmonics

This article proposes two types of dual excitation permanent magnet linear machine (DEPMLM) for long-distance application. By incorporating asymmetry in dual excitation, both the second-order harmonic magnetomotive force (MMF) in primary excitation (PE) and the second-order harmonic permeance in secondary excitation (SE) are effectively generated. The extended working harmonics generated on this basis can substantially enhance thrust force density. The article begins by describing the machine topology and operating principles under dual excitation. It then discusses the analytical modeling and thrust force generation mechanism based on multiple working harmonics, validated through finite element analysis (FEA). Next, it evaluates and compares the electromagnetic performance of DEPMLM with other PMLMs, followed by validation through a prototype. The results demonstrate that with dual excitation, the proposed DEPMLM achieves substantial increases in thrust force density—exceeding 98.1% and 79.1% compared to the existing asymmetric flux reversal PMLM and switched flux PMLM, respectively. Additionally, DEPMLM improves thrust force density by 40.6% while requiring only about 60% of the PMs used in conventional PMLMs with SE over a 10-m distance. DEPMLM thus emerges as a competitive and cost-effective solution for long-distance applications, outperforming existing PE-PMLMs and conventional PMLMs.