Overview of flux-controllable machines: Electrically excited machines, hybrid excited machines and memory machines

Flux-controllable machines have attracted much attention in modern industry, especially in electric vehicle propulsion and wind power generation, as they can ensure a wide constant power speed range when working at motoring mode, while maintain constant induced voltage when working at generating mode. This paper reviews the current research work about flux-controllable machines, mainly focused on electrically excited machines, hybrid excited machines and memory machines. The latest novel machine concepts with the potential of good flux controllability are particularly investigated. The working principle, advantages and drawbacks, and future trends of different flux-controllable machines are discussed, compared and summarized in detail.