Electromagnetic Performance Analysis of Novel HTS Doubly Fed Flux-Modulated Machines

The flux-modulated machine is designed based on a promising low-speed direct-drive concept for applications such as wind turbines, due to its inherent magnetic gearing effect. In this paper, a novel doubly fed flux-modulated machine using high-temperature superconducting (HTS) bulks is proposed. Compared with previous permanent-magnet (PM) flux-modulated machines, the beauty of the proposed machine is that electric excitation, instead of PMs, is exploited to improve its flux controllability with reduced cost. Unlike conventional electric-excited synchronous machines, neither slip rings nor brushes are needed in this novel machine because both the field windings and the armature windings are housed in the stator. In other words, the proposed machine combines the merits of a flux-modulated machine and an electric-excited machine. To alleviate the end effect in flux-modulated machines, HTS bulks are used for flux modulation. The performance of the machine is analyzed using finite-element method.