Optimization Design Of Double-side Permanent Magnet Synchronous Linear Motor Adopting Staggering Primaries Structure

The double-side permanent magnet synchronous linear motor(DS-PMSLM)is a typical structure of the permanent magnet linear motor with the advantages of small normal force and high volume utilization.However,the DS-PMSLM adopting the short primary and the moverable armature has the drawbacks of large end effect and big thrust ripple because of the open short primary iron core.If the motion stroke is large,the amount of permanent magnets in the secondary will alse be large.It causes high cost and low thrust density.Hence,for the sake of decreasing the thrust ripple and improving the thrust density,the optimization design of the DS-PMSLM is carried out.The optimization designs of the armature structure on double sides and the secondary structure in the DS-PMSLM are carried out,which are described as follows.The air-gap magnetic densies,magnetic field harmonics,and the thrusts of the DS-PMSLM which employed different slot-pole combinations are analyzed.The layered and orthogonal optimization methods are combined and employed to design the pole structure.This method can save the calculation time effectively.The detent force is suppressed by adopting staggering primaries structure.A DS-PMSLM prototype and its test platform are manufactured and tested.A novel staggering primaries structure of DS-PMSLM is proposed to overcome the drawbacks of the conventional staggering primaryies.The both primaries are staggered by the electrical angle of 60°or 120°,and the windings in the primaries are re-arranged and adjusted accordingly.This structure can suppress the detent force without reducing the voltage and the average thrust and be verified by finite element method(FEM)calculations.A scheme of modular primary is combined with the novel staggering primaries structure to inhibit the detent force and the ripple thrust,as well as improve the average thrust.The influence of different modularized distance on the output performance is obtained.The large consumption of the permanent magnets in conventional DS-PMSLM is considered,and the consequent-pole structure is applied to the DS-PMSLM.The magnetic field distribution of the consequent pole is analyzed and verified through tests.The thrust,thrust ripple and thrust density characteristics of the PMSLMs with conventional N-S pole and consequent pole are compared in detail.In order to overcome the disvantage that the even-order harmonics in the back EMF of the consequent-pole motor is much larger,a consequent-pole DS-PMSLM with phase compensation structure is proposed to inhibit the even-order harmonics.Corresponding FEM simulation is carried out to verify that the compensation structure can suppress the thrust ripple that is caused by voltage harmonics.