Design and Parametric Analysis of a Long Stroke Magnetic-geared Flat Linear Machine with Low Material Costs

The magnetic-geared flat linear machine (MGFLM) has the advantage of low material costs for long stroke applications, due to the expensive coils and permanent magnet are now located in the two short stators and the long mover is only composed of ferromagnetic blocks and non-magnetic material. Different pole-pair combinations of the MGFLM are first compared, and two MGFLMs with pole-pair combination of 4-15-19 and 4-17-21 showing good thrust characteristics are selected for further study. For the MGFLM 4-15-19 and 4-17-21, the total harmonic distortion (THD) of the back electromotive force (EMF) is calculated, and the design parameters such as dimensions of the armature core and the steel poles are analyzed by using finite element method (FEM). The results show that the MGFLM 4-15-19 has a 90% reduction in THD of the back EMF, a 46% reduction in thrust ripple and a 4% increase in average thrust compared with a traditional permanent magnet linear synchronous motor (PMLSM). Under the same conditions, the MGFLM 4-17-21 has a 92.7% reduction in THD of the back EMF, a 47% reduction in thrust ripple and almost keeps the same average thrust compared with the PMLSM. The MGFLM is believed to be suitable for long stroke application as it shows advantage in material costs over the moving-coil PMLSM and the moving-magnet PMLSM when the stroke exceeds 150mm.