No-load Features of T-LSMs With Quasi-Halbach Magnets: Application to Free Piston Engines

Abstract

The paper is devoted to the prediction followed by the enhancement of the no-load features of tubular linear synchronous machines (T-LSMs) with quasi- Halbach magnetized PMs in the mover. The study is initiated by the prediction of the spatial repartition of the no-load air gap flux density. Then, a formulation of the back-EMF and the cogging force, based on the predicted spatial repartition of the no-load air gap flux density, is developed, considering 1) the case of an infinite length machine and 2) the case of a finite length one. A case study, corresponding to an initial concept, is treated with the prediction of its no-load features. The study is extended to the enhancement of these features with emphasis on the effects of two influent sizing parameters, assuming an infinite length machine. This enables the identification of a preoptimized concept. The back-EMF and the cogging force of this latter are then predicted in the case of a finite length machine. A further enhancement of these features is gained, thanks to a quasicancellation of the end effect. The prediction of the back-EMF and the cogging force of the optimized T-LSM with quasi- Halbach magnetized PMs has clearly demonstrated the effectiveness of the proposed approach.