Design and Quantitative Analysis of Dual Permanent Magnet Linear Machine with Reduced Rare-Earth PM Usage

This paper proposes a dual permanent magnet linear machine (DPMLM) designed to minimize rare-earth PM usage for long-distance applications. By introducing asymmetry into the dual PM excitation, it effectively generates both the second-order harmonic magnetomotive force (MMF) in the primary excitation (PE) and the second-order harmonic permeance in the secondary excitation (SE). The resulting extended working harmonics significantly enhance thrust force density. The paper first outlines the machine topology and operating principles under dual PM excitation. It then presents an analytical model for multiple working harmonics, validated through finite element analysis (FEA). Subsequently, the electromagnetic performance of the DPMLM is evaluated and compared with other PMLM configurations. The proposed DPMLM demonstrates higher thrust force density than two types of primary-excited PMLMs (PE-PMLMs) while utilizing a smaller PM volume. Furthermore, it achieves approximately 80% of the thrust force density of conventional PMLMs while requiring only about 0.5% of the rare-earth PM material over a 10-meter distance.