On the stator magnetic circuit design of tubular-linear PM synchronous machines: A comparison between three topologies

This paper is aimed at the design of tabular-linear PM synchronous machines (T-LPMSMs) with emphasis on the stator magnetic circuit. Three topologies are investigated, such that: (i) an initial concept where the stator pole pitch is equal to the mover one, (ii) a modular concept where the stator is made up of magnetic units separated by a flux barrier, and (iii) a concept characterized by fractional slot per pole and per phase. A magnetic equivalent circuit (MEC) is build in order to select suitable geometrical parameters of the second topology that minimize the end effect; the ones of the first and third topologies have been treated in a previous work. The phase flux linkages and back-EMFs are investigated by FEA. It has been found that the second topology exhibits almost balanced back-EMFs. While, these have the lowest harmonic content in the third topology.