Design and performance of linear Vernier generators—The state of the art and case study

Abstract

Summary Although Vernier machines have been introduced a long ago, their description, applications, and design improvement have been recently proposed. This paper reviews different types of linear Vernier machine. Their description and theoretical base of the performance are presented. The performance of the motor is improved by reducing the cogging force, increasing the power factor, and enhancing force density. Stator and translator structures, the arrangement of magnets, and the type of coils of permanent magnet (PM) Vernier machines are reviewed and classified. Then, the electromagnetic performance prediction and energy conversion process in the machine is described. The magnetic field distribution and air gap permeance analysis indicate that such analysis is very complicated than that of other PM machines. Impacts of variations of dimensions in the machine such as the number of modulators on the modulus width and thickness of the mover PMs on the load characteristics (cogging torque and Back‐EMF) are addressed. Besides, principles of operation of flux modulation machines are presented and the shape and dimensions of the modulators are optimized. Finally, a 150 W linear PM Vernier generator is designed and prototyped to the energy harvested by the ocean wave.

Performance analysis of linear permanent magnet Vernier machine using mixed subdomain and magnetic equivalent circuit techniques including end‐effect

“…In the LPMVM, the magnetic field of mover three‐phase winding and the modulation magnetic field of PMs (with stator slots permeance) produce two travelling magnetic fields (static in respect to each other); interaction between these two fields generates a continuous electromagnetic force. Based on the operation principles of the Vernier machines, a continuous thrust force is generated if the following is held [42, 43]: $$${P}_{s}=\vert {z}_{1}{N}_{1}\pm {z}_{3}{N}_{3}\vert $$$ where N 1 and N 3 are the mover PM number and stator teeth number beneath and z 1 and z 3 are integers. The highest amplitude of the harmonics is produced if z 1 = z 3 = 1, leading to the highest gearing ratio.…”

“…In the LPMVM, the magnetic field of mover three-phase winding and the modulation magnetic field of PMs (with stator slots permeance) produce two travelling magnetic fields (static in respect to each other); interaction between these two fields generates a continuous electromagnetic force. Based on the operation principles of the Vernier machines, a continuous thrust force is generated if the following is held [42,43]:…”

“…Based on the previous findings on the optimal structure of linear Vernier machines, it has been shown that consequent PMs with Halbach array, toothed-poles, and three-phase concentrated winding have useful effects on the thrust force, EMF, and efficiency [42][43][44][45][46]. Figure 1 shows the proposed structure of the linear permanent magnet Vernier machine (LPMVM) with no Halbach array of PMs for magnetic field calculation.…”

Asymmetric air gap fault detection in linear permanent magnet Vernier machines

“…A frequency index is introduced and used by Faiz et al (2020) to detect the AAGF fault in LIM. This method uses the frequency analysis of the primary current signal of the machine to detect asymmetric fault.…”

“…This type of renewable energy has many advantages, including high predictability, stability, high energy density and low speed. These characteristics make wave energy conversion a promising renewable energy source for the future (Zhao et al, 2019;Faiz et al, 2021). Previously, energy conversion at low wave speeds relied on linear induction generators, which required more mechanical interface and this increases the weight and leads to a more complicated system.…”