Reducing detent force and three-phase magnetic paths unbalance of PM linear synchronous motor using modular primary iron-core structure

The Detent force and unbalance of the three-phase inductances are the major obstacle for permanent magnet linear synchronous motors (PMLSM) obtaining higher positioning accuracy. They both can be attributed to the longitudinal end-effect that, however, is an inherent characteristic for PMLSMs. To overcome these drawbacks, this paper utilizes a reverse perspective: increasing the number of ends. Thus, a modular primary iron-core PM linear synchronous motor (MPI-PMLSM) is investigated. Unlike for conventional linear synchronous motors, the MPI-PMLSM´s primary iron-cores are dispersed. This structure allows the MPI-PMLSM very small detent force, and moreover, it almost eliminates the inductances unbalance. The effectiveness is proved by both finite element analysis and experiment.