Tubular unified magnetic‐field flux‐switching PMLM for free‐piston energy converter

Abstract

A tubular flux-switching permanent-magnet linear machine (PMLM), which features unified magnetic field between the mover and two stators, is investigated for free-piston energy converter. The topology evolution, topology, operating principle and design considerations of the machine are thoroughly analysed. With the sinusoidal speed characteristic of free-piston Stirling engine considered, a tubular unified magnetic-field flux-switching PMLM is designed by finite-element analysis. Several main structural parameters, which include the outer and inner radius of the mover, the mover tooth width, the magnet thickness, the tooth widths of both the outer and inner stators and the widths of both the outer and inner stator yokes are studied to achieve high-force and mass-power density. Finally, the proposed machine is compared with two typical flux-switching PMLMs. The comparison results show that the unified magnetic-field flux-switching PMLM is suitable for applications which require highpower density, light mover structure and fast dynamic.

A Plate Moving-Magnet Linear Generator Designed for Free-Piston Engines

“…Generating efficiency is an important performance indicator of generators. Nowadays, these strict requirements are the main problems for a suitable linear generator for FPEG to be developed [6], [7].…”

Modelling of axial‐flux eddy‐current couplers

“…2D and 3D finite‐element method (FEM) as employed for radial and axial‐flux machines [1–4], although precise, are very time‐consuming and not suitable for the preliminary designs, while analytical approaches provide fast, flexible and relatively accurate calculations, introducing a powerful tool for the design procedure. The second technique may be divided into two categories: first, subdomain methods which are on the basis of Laplace's and Poisson's equations as used for surface‐mounted PM machines [5, 6], switched reluctance machine [7], and flux switching machine [8]; second, flux‐tube models or magnetic equivalent circuit (MEC) approaches as used for salient pole [9], flux‐switching [10], Vernier [11], and switched reluctance [12] machines as well as magnetic bearings [13]. The former, albeit powerful, is usually sophisticated and unable to effectively account for the materials such as magnetic saturation of the iron elements, and it has essential problems with many geometries.…”