Modeling and Optimization of a Tubular Permanent Magnet Linear Motor Using Transverse-Flux Flux-Reversal Topology

In this paper, a novel tubular transverse-flux flux-reversal linear motor for long stroke applications is proposed. The proposed motor not only has the low-cost advantage of the existing flux-reversal permanent magnet (PM) linear motor (PMLM) by combining both PMs and armature winding in short primary, but also address the problem of complicated structure in conventional tubular PMLM by using the manufacturing process of the rotary motor. First, in order to reduce circumferential magnetic flux leakage and improve the utilization ratio of PM, the motor structure with the alternating distribution of double N poles and double S poles in the circumferential direction is designed, and the operating principle of the motor is presented. Then, the equivalent magnetic circuit model of the unit motor is established to derive the expressions of the back electromotive force (EMF) and the electromagnetic thrust. Third, the equivalent two-dimensional (2-D) finite-element method (FEM) is used to optimize the structural dimensions and analyze the static characteristics including the back EMF, the detent force, and the thrust. Meanwhile, the three-dimensional FEM verify the validity of the equivalent 2-D FEM. Finally, the experimental results verify the validity and the correctness of the topology structure and the design method of the motor.