Investigation of a Segmented Poles Quasi-Halbach T-LSM: a Viable Concept for Free Piston Engines

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. This 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 study is initiated by an

analytical formulation of the air gap flux density considering (i)

the case of the conventional quasi-Halbach T-LSM and (ii) the

case of the segmented pole one. The comparison between the

two T-LSMs is extended to a 3D finite element analysis (FEA)-

based investigation of their no- and on-load features. Following

the prototyping of the quasi-Halbach T-LSM with segmented

poles, selected features predicted by 3D FEA are experimentallyvalidated.

It is shown that while the PM segmentation slightly

affects the machine back-EMF and cogging force, it has a

remarkable fallout on its force production capability which makes

it necessary the assessment of the cost-performance trade-off.