Research On Tubular Flux-switching Permanent-magnet Linear Machine

With the advantages of high power density and high efficiency, tubular permanent-magnet linear machine is widely used in Free-piston Stirling power generator system. However, it’s difficult to balance its robust mover structure and fast dynamic response characteristic under high frequency oscillation, and easy to cause irreversible demagnetization of PMs. To solve above problems, this paper describes a novel tubular flux-switching permanent-magnet linear machine(TFSPMLM), which has a simple, strong and light mover, good heat radiation of external primary, and easy control of single-phase winding.Firstly, the working principle and the establishment of the mathematical model of the machine are proposed in this paper, including electromagnetic model, equivalent circuit model and simple harmonic motion model. A 300 W TFSPMLM model is designed and its 2D-FEM is established. Some basic electromagnetic characteristics are discussed by finite element analysis(FEA) including inductance, flux leakage, air gap flux density, flux linkage and back electromotive force(back-EMF), and so is the effect of motion states on its electromagnetic performance, which consists of back-EMF,power, losses and load characteristics.Secondly, the effect of structural adjustment on its performances is analyzed,including magnet shape, stator/mover tooth width and mover yoke inner/outer diameter,by observing indexes of back-EMF, power, power density, losses, efficiency, thrust, etc.In optimization process, power density is taken into the first consideration, with a further one of high efficiency and thrust.Furthermore, sources of detent force and its reducing methods are discussed in this paper. The impact of detent force on thrust is analyzed by FEA. By comparison, a reducing method of appropriate ratios of structural parameters is proposed, which consists of the fit of stator tooth width and magnet thickness, and that of stator and mover tooth width.Finally, with the consideration of its closed chassis structure and doubly salient secondary, thermal field distribution of the particularity of structure is analysed.TFSPMLM 3D physical model is established, and the main thermal field calculation parameters are also confirmed. Steady-state temperature field distribution is analyzed by FEA, and the influence of different cooling conditions on thermal field distribution is given.