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.

A novel double-sided yokeless multitooth linear switched-flux permanent magnet (DYMLSFPM) motor is proposed to improve the electromagnetic performance of conventional double-sided linear switched-flux PM (DLSFPM) motor in terms of force ripple and cogging force. Its feature of structure is the multitooth primary without yoke. First, an analytical method of permeance model is developed for determining the optimal combination of primary slots and secondary poles. For DYMLSFPM motor with six primary slots, there are four available different secondary poles 16/17/19/20, respectively. By comparing the results of four combinations, it shows that the DYMLSFPM motor with 19 secondary poles can have better thrust force performance, which is also verified by the finite-element analysis. After all these four structures are optimized first by single-variable optimization and then by global optimization with genetic algorithm for further analysis, 6-slots/19-poles (6s/19p) combination can have the second highest average thrust force and the lowest thrust ripple. Moreover, it requires significantly smaller volume of PMs and exhibits much lower cogging force than conventional 6s/7p DLSFPM motor. Finally, a prototype of 6s/19p DYMLSFPM motor is manufactured and tested to validate the predicted results.

An effective analytical model of permanent magnet linear synchronous machine (PMLSM) is proposed in this paper, which considers the end effect by adding virtual slots and the slotting effect by adopting relative air-gap permeance. To employ this model, the open-circuit air-gap flux density of a slotless PMLSM with virtual slots is firstly predicted by Subdomain (SD) method, and then the complex relative air-gap permeance is introduced based on conformal mapping. By multiplying these two quantities, the open-circuit air-gap flux density of actual slotted PMLSM can be obtained. The phase flux linkage, back-EMF and detent force can be predicted accordingly. Moreover, the detent force is more easily depressed by optimizing the end teeth and slots via the proposed method. The predicted results are validated by 2-D nonlinear finite-element (FE) and prototype measurements.

This article proposes two kinds of asymmetric flux reversal permanent magnet linear machine (AFR-PMLM) for long excursion application. By utilizing asymmetric permanent magnet excitation, the AFR-PMLM can effectively generate and fully exploit the second-order harmonic magnetomotive force (MMF), leading to a significant enhancement in thrust force density. First, the machine topology and operation principle are introduced. Then, the thrust force generation mechanism under multi MMFs is analytically calculated based on an improved MMF-permeance model, and further verified by finite element analysis. Various electromagnetic performances, including open-circuit characteristics, thrust force performances, and power factor, are comparatively studied. It shows that the proposed AFR-PMLM with consequent pole structure can provide 40.1% higher average force than conventional FR-PMLM under rated condition. In addition, it consumes only about 39.5% of the PMs volume while providing approximately 90.4% of the thrust force compared with switched flux PMLM. More importantly, the AFR-PMLM consumes only 1/80 PMs volume while achieving 75.0% of the thrust force density compared with conventional PMLM for a long excursion with 10 m. Finally, two prototypes of AFR-PMLM are manufactured for experimental validation.

An improved superposition method accounting for both permanent magnet (PM) and armature field is proposed to predict the unbalanced magnetic force (UMF) of PM machines having static/dynamic eccentricity. It virtually divides the original eccentric machine into a number of sections along the circumferential direction. Then, a series of concentric machine models are established with equivalent air‐gap lengths corresponding to those air‐gap sections. From the electromagnetic field of each concentric machine predicted by subdomain method, the air‐gap field of the original eccentric machine can be synthesised. Finally, the UMF can be easily obtained by the integral of force density along the air‐gap circumference. The effectiveness of the proposed method is validated on both rotating asymmetric and symmetrical PM machines by direct finite‐element analysis and experiment, with particular emphasis of rotor eccentricity influence on the UMF of later one.

A novel partitioned-primary hybrid-excited flux-switching linear machine with dual-PM excitation (DP-PPHEFSLM) is proposed and investigated in this paper. Unlike conventional single-primary hybrid-excited topologies, this proposed topology separates armature windings and field windings into two different parts of the partitioned-primary, with each part also having sandwiched or buried PMs. Due to greatly increased armature and field slot areas, it thus solves the problem of a crowded primary, which is typically encountered with conventional structures. Besides, the thrust density is further increased by skillfully positioning PMs on both primary parts. In this paper, firstly, the topology, operation principles and viable primary/secondary pole-number combinations of the proposed machine are elaborately addressed. Based on 2D finite-element method (FEM), the proposed machines are globally optimized using genetic algorithms (GA) and their electromagnetic performances further investigated. Moreover, the proposed machine is compared with conventional topologies in terms of electromagnetic performances, which shows that the proposed machine exhibits multiple merits such as higher thrust density, improved space utilization and more flexible flux control capability. Finally, a 6/7 DP-PPHEFSLM prototype machine is manufactured and tested to validate the 2D FEM-predicted results.