Abstract
Linear flux-switching permanent magnetic (LFSPM) machines are good choices for long stroke applications. These machines deliver high thrust force density in addition to the machine structure where permanent magnetics (PMs) and windings are all on the short mover. For LFSPM machines, their performance is always affected by big thrust force ripple. In this paper, for two C-core LFSPM machines of high thrust force capability, including a 6/13 C-core LFSPM (6/13LFSPM-C) machine and a sandwiched C-core LFSPM (SLFSPM-C) machine, and a thrust force ripple reduction method is proposed. The proposed method is developed by reducing the slot effect component of the cogging force based on staggered stator tooth, and suppressing the thrust force ripple caused by unbalanced three phase back-electromagnetic forces (EMFs) based on two end PMs. Based on finite element analysis (FEA) results, both C-core LFSPM machines can achieve small thrust force ripples as well as high sinusoidal back-EMFs, and at the same time, maintain high thrust force capability with the proposed method. It was also found that, the improved SLFSPM-C machine exhibited the same thrust force capability as the improved 6/13LFSPM-C machine, but with a much smaller thrust force ripple.
Highlights
Linear machines are capable of providing faster dynamic performance, higher precision, lower noise, lower maintenance, and lower pollution when compared with rotary machines as gear boxes, chains, and ball screws can be eliminated in linear motion, making these machines better choices in many industrial applications such as transportation, aerospace and other linear motion systems [1,2,3]
Linear flux-switching permanent magnet (LFSPM) machines, which inherit the advantages of high thrust density of the rotary flux-switching permanent magnetic (FSPM) machines, have attracted interest from researchers
The results show that when the skewing step displacement is τ s /9, that is, displacement is τs/9, that is, 1 mm, the SLFSPM-CS machine has the smallest proportion of p-p
Summary
Linear machines are capable of providing faster dynamic performance, higher precision, lower noise, lower maintenance, and lower pollution when compared with rotary machines as gear boxes, chains, and ball screws can be eliminated in linear motion, making these machines better choices in many industrial applications such as transportation, aerospace and other linear motion systems [1,2,3]. Linear flux-switching permanent magnet (LFSPM) machines, which inherit the advantages of high thrust density of the rotary flux-switching permanent magnetic (FSPM) machines, have attracted interest from researchers. For applications such as urban rail transit (URT) which always adopt linear machines with a long stator and short mover, the LFSPM machines, having the magnets and armature windings all on the mover, in addition to a simple and robust stator structure, are very suitable due to their high reliability, low expenses, and easy road maintenance [4,5]. Due to the double salient structure of both the mover and stator, as well as the end effect, there exists considerable cogging forces in the LFSPM machines These forces result in periodic ripples in thrust force, and worsen the performance of the LFSPM machines [6,7,8]. A method where assistant iron teeth are fixed on the mover
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