Feature Investigation of a Segmented PM Quasi- Halbach Tubular-Linear Synchronous Machine

The paper is aimed at an investigation of the featuresof a tubular-linear synchronous quasi-Halbach machine (T-LSM)where the radially-magnetized PMs are substituted by four equalsegments with parallel magnetization. This substitution is donein an attempt to improve the machine cost-effectiveness whichmakes it a viable candidate to equip free-piston engine-basedseries hybrid propulsion systems. The study is initiated by ananalytical formulation of the air gap flux density considering (i)the case of the conventional quasi-Halbach T-LSM and (ii) thecase of the segmented pole one. The comparison between thetwo T-LSMs is extended to a 3D finite element analysis (FEA)-based investigation of their no- and on-load features. Followingthe prototyping of the quasi-Halbach T-LSM with segmentedpoles, selected features predicted by 3D FEA are experimentallyvalidated.It is shown that while the PM segmentation slightlyaffects the machine back-EMF and cogging force, it has aremarkable fallout on its force production capability which makesit necessary the assessment of the cost-performance trade-off.