Analysis and Evaluation of Hybrid-Excited Doubly Salient Permanent Magnet Linear Machine With DC-Biased Armature Current

This article investigates a hybrid-excited doubly salient permanent magnet linear machine (HDSPMLM) with dc-biased armature current. With the adoption of integrated open winding, dc bias can be achieved by zero-sequence current, which helps to enhance the dc excitation and further highly improves the thrust force density. First, the machine topology and drive circuit are described. By injecting the dc currents into the armature windings with special arrangement, the dc field windings in conventional HDSPMLM can be eliminated, where the phase currents are dc-biased sinusoidal currents. Then, magnetomotive force-permeance model is built to analytically calculate the air gap hybrid-excited field harmonics, and further verified by finite element analysis. Moreover, the flux linkage, back-electromotive force, and static force-current characteristics between the proposed and conventional HDSPMLMs are comparatively studied. Thanks to the improved exciting field and armature magneto-motive force with integrated open winding, the thrust force capability can be significantly enhanced by 85.5% on the premise of rated power dissipation. The proposed machine is suitable for the operation of short-time large-thrust condition. Finally, the experiments on a prototype of the HDSPMLM are carried out for validation.