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A Permanent Magnet Linear Electric Machine for the Free-Piston Linear Generator System: Design and Experimental Verification

The free-piston linear generator can be employed as an auxiliary power unit in the hybrid electric vehicles due to the advantages of high efficiency and multi-fuel flexibility. This paper proposes a novel double-sided flat-type permanent magnet synchronous linear electric machine which is one of the key components of the free-piston linear generator. The flat-type mover is equipped with quasi-Halbach permanent magnet arrays on its double surfaces, and is sandwiched between two flat-type stators. Concentrated windings are inserted in the slots of the stators. The design considerations on the feasible slot and pole combinations are discussed. The major performance such as output power and efficiency are predicted via finite element method. A prototype is built up and the design has been verified through experiments. The results indicate that a high operation frequency can improve the output power, and efficiency can be optimized by regulating the loads.