Design and Analysis of a Magnetless Linear Variable Reluctance Motor With Modular Mover Units for Electric Propulsion

This paper proposes a magnetless linear variable reluctance motor (MLVRM) with modular mover units (MMUs) for electric propulsion. The proposed MLVRM adopts a doubly-salient structure with two sets of windings on mover, namely the ac armature windings, the dc field windings. In space, the two sets of windings are naturally isolated from each other due to the iron-core structure of the mover. Consequently, the space conflicts between the two sets of windings can be eliminated. To improve the force production capability, high-temperature superconducting (HTS) windings injected with large current are employed in the dc windings. The focus of this paper is to elaborate the method to adopt MMUs with equal clearance to suppress force ripple without weakening the back electromotive force (EMF). This paper also introduces the structure, working principle and choice of key parameters for the proposed MLVRM in detail. Moreover, MLVRMs with different number of MMUs are compared to MLVRM with only one MMU by finite element method (FEM) to verify the proposed method to suppress force ripple. The results show that the force ripple decreases significantly from 24.75% to 12.59% when the MLVRM adopts two MMUs.