Flux adjustable permanent magnet machines: A technology status review

Flux adjustable permanent magnet machines (FAPMMs) are a novel type of permanent magnet (PM) machines which are able to flexibly adjust the field excitation flux linkage and offer the distinctive advantages of high power density and high efficiency. They have attracted ever-increasing interests and are promising candidate machines for electric vehicle, machine-tool and aircraft applications. In this paper, the state-of-the-art of various FAPMMs are comprehensively reviewed according to three means of flux-adjustment, i.e. electrically adjusted by either auxiliary field windings or armature winding change, mechanically adjusted magnetic reluctances of flux paths, and memory machines by magnetizing/demagnetizing PMs. The corresponding flux-adjustable principles and electromagnetic characteristics are systematically elaborated and quantitatively compared. Their merits and demerits are highlighted, together with their recent developments.