Thrust and Levitation Coupling and Fluctuation Analysis of Linear Doubly-Fed Induction Motors With Variable Air-Gap

Abstract

Within variable air-gap linear motors, such as those used in maglev trains, levitation and thrust forces are both realized through the common air-gap magnetic field, and thus they are intrinsically coupled. Additionally, nonidealities such as cogging, end effect, and saturation influence the thrust and levitation performance and result in force fluctuation. In this article, an accurate modeling method for a variable air-gap linear doubly-fed induction motor based on the magnetic coenergy reconstruction is proposed, where the effects of magnetic saturation, variable air-gap, and spatial harmonics are taken into consideration. This method uses a unified dataset to describe thrust, levitation, and their fluctuations. Furthermore, an adjustable air-gap linear motor prototype is designed and constructed. Bench tests are conducted to verify the proposed model.