Feature Investigation of a Segmented PM Quasi- Halbach T-LSM: Cost-Performance Trade-off

The paper is aimed at an investigation of the features of a tubular-linear synchronous quasi-Halbach machine (T-LSM) where the radially-magnetized PMs are substituted by four equal segments with parallel magnetization. Such a substitution is done in an attempt to improve the machine cost-effectiveness which makes it a viable candidate to equip free-piston engine-based series

hybrid propulsion systems. The investigation is initiated using a 3D analytical model of the flux density spatial repartition considering (i) the case of the conventional quasi-Halbach T-LSM and (ii) the case of the segmented parallel-magnetized PM one. The comparison between the two linear machines is extended to a 3D finite element analysis of their no- and on-load features. Following the prototyping of the quasi-Halbach T-LSM with segmented parallel-magnetized PMs, selected features predicted by 3D FEA are experimentally-validated. It is shown that while the PM segmentation slightly affects the back-EMFs and cogging force, it has a remarkable fallout on the machine force production capability which makes necessary the assessment of the cost-performance trade-off.