Magnetization space harmonic analysis of TLPMGs allowing for magnetic saturation

The paper presents a FEM procedure for the performance evaluation of short-stroke tubular linear permanent magnet generators (TLPMGs), adopted in `free-piston' energy converters. In the hypothesis of magnetic linearity, the magnetic field can be calculated by the superposition of simplified models derived from the decomposition of the PM magnetization in two space distributions. However, an iterative procedure is set up to take into account the local saturation of the mover yoke - generally not negligible - by adjusting the model parameters. By this technique, a preliminary design of the TLPMG moving part can be carried out by comparing the effects of different magnetization schemes on the main electromagnetic quantities (flux linkage, axial force). The results related to a 3-poles PM configuration confirm the method straightforwardness and accuracy, enabling as well to choose the more suitable PM characteristics according to the TLPMG operation.