energies Article A Novel Triple-Permanent-Magnet-Excited Vernier Machine with Double-Stator Structure for Low-Speed and High-Torque Applications Xinbo Liu 1,2, Xu Zhong 2, Yi Du 1,* ID and Xun Chen 2 1 School of Electrical and Information Engineering, Jiangsu University, Zhenjiang 212013, China;
[email protected] 2 School of Electronics and Information, Jiangsu University of Science and Technology, Zhenjiang 212013, China;
[email protected] (X.Z.);
[email protected] (X.C.) * Correspondence:
[email protected]; Tel.: +86-139-1455-7920 Received: 23 May 2018; Accepted: 27 June 2018; Published: 1 July 2018 Abstract: In this paper, a novel triple-permanent-magnet-excited vernier (TPMEV) machine with double-stator (DS) is proposed, of which the power density and the torque density are effectively improved to satisfy the operating requirements of low speed and high torque density for direct drive systems. Three sets of permanent magnets (PMs) are placed on the two stators and the rotor, respectively, and the magnetic fields excited by these PMs are modulated to effective magnetic field harmonics with low pole-pair numbers and high speeds based on bi-directional field modulation effect of the non-uniform airgap permeance. Then two sets of armature windings respectively accommodated in two stators are designed according to the effective magnetic field harmonics, thus achieving the coupling between the PM magnetic fields produced by three sets of PMs and armature windings. Firstly, the topology of the TPMEV-DS machine is introduced. Secondly, the airgap flux density of the machine is analyzed based on the equivalent magnetic circuit method, which proves the improvement potentiality of power density and torque density due to the bi-directional field modulation effect.