Analysis and optimization of Ironless permanent magnet linear motor for improving thrust

Abstract

As is known, improving launcher thrust is the target that the mankind is pursuing. There is no saturation phenomenon in the Ironless permanent magnet linear motor(IPMLM), so the thrust of IPMLM has a linear relationship with current through windings to provide larger thrust. The topology of IPMLM determines thrust fluctuation is smaller than Iron-PMLM. In this paper, the model of airgap magnetic field is established by magnetic charge method and image method for global optimization of IPMLM thrust. All dimensions of IPMLM are described by motor thickness and three ratio coefficients(α, β and γ). The cooling power of cooling system under different temperature gradients, which determines current density of winding, is calculated by Comsol software. When α, β and γ are different means each dimension of IPMLM is different, the current density in different winding could be determined by constraint condition, p cu ≤ Q. So we can obtain the surface of current density and dimension, and the surface of thrust and dimension. For obtaining maximum thrust in the same volume, the size ratio among magnetic structure, winding structure and cooling structure is derived by the thrust analytical expression. The distribution of IPMLM thermal field is analyzed by 3-D finite element method, and this optimization method of IPMLM thrust density is proved by experiment.