Design Criterion and Analysis of Hybrid-Excited Vernier Reluctance Linear Machine With Slot Halbach PM Arrays

This article proposes a hybrid-excited vernier reluctance linear machine (HEVRLM) with slot Halbach permanent magnet (PM) arrays. By utilizing Halbach PM arrays, leakage flux that exists in the consequent pole structure can be greatly reduced. Besides, the dc excitation can enhance both the flux regulation capability and the force density. First, the machine topology and working principle are introduced. Then, a magnetomotive force and permeance model is established to analytically calculate the air-gap flux density under hybrid excitation. Moreover, the flux regulation capability, thrust force characteristic, and PM demagnetization risk of the proposed machine are comparatively studied based on the finite-element method. It shows that Halbach PM arrays can effectively reduce the leakage flux and further significantly improve the thrust force density by more than 30%. In addition, hybrid excitation is a feasible approach to further improve the thrust force density by distributing the optimal dc and ac currents. Moreover, the proposed HEVRLM exhibits high thrust force density compared with the other three types of hybrid-excited linear machines. Finally, a prototype of HEVRLM is manufactured and tested for experimental validation.