Study On Permanent Magnet Flux-Swiching Linear Machines

Permanent magnet flux-switching linear machines (PMFSLM), which combine the merits of both linear machines and PMFS rotary machines, possess advantages such as simple and robust structures, and high thrust density. It is particularly cost-effective since the expensive magnets and coils are both set on the short mover while the long stator is made of cheap laminations only. The savings in manufacture costs can be a great benefit for applications with long strikes, for instance, for the rail transportation propulsion. Therefore, PMFSLM is a special linear machine with potentially wide application ranges, and deserves deep investigations.This dissertation will introduce the developments of permanent magnet (PM) linear machines briefly and doubly salient permanent magnet (DSPM) machines more detailedly, and then review methodically the literatures presented by both domestic and overseas researchers. Related research work on PMFSLM will be summarized in this dissertation.Moreover, following research work by the author will be presented. Firstly, the influence of slots/poles combination is discussed since it is a key issue for primary design of PMFSLM. The mathematic model in the dq-frame is established. Then, comparative studies on PMFSLM and conventional PM linear machines for applications of rail transportation propulsions are carried out as an example, and the performance is analyzed in detail for a6/7-pole PMFSLM.Then, a new method that comprehensive assistant end teeth are employed on PMFSLM ends to reduce detent force is proposed. This method is similar to those methods modifying a suitable mover core length to minimize detent force. Compared with independent assistant teeth, which can only reduce the detent force, the comprehensive assistant teeth can not only reduce the detent force, but also improve other performance by enhancing the end coils’ output.Subsequently, in order to analyze the detent forces better, a new simple method to segregate detent force components based on rotary machine models is performed. The rotary model converts the linear machines into complete slotted rotary machines without any ends. Therefore, the slot force can be calculated individually, thus, the detent force is segregated successfully. The segregation of detent force provides enhanced reference for further investigation of detent force in PMFSLMs.After that, a modular PMFSLM with high fault tolerant capability is developed. Compared with conventional PMFSLMs, half amount of magnets is taken away in the proposed PMFSLMs. Furthermore, alternative teeth wound and modular design are adopted, which result in many new merits such as a more effective usage of magnets, higher fault tolerance as well as low manufacturing cost for mass producing. Generally speaking, the proposed modular PMFSLM with fault tolerant capability is a competitive PM linear machine for applications in a wide range.