The brushless doubly－fed machine（BDFM）， with simple structure and favorable reliablity has gained renewed attention In adjustable－speed drived variable－speed constant－frequency generator applications. In recent years for it features adjustable power factor and high efficiency．In BDFM; since both power winding and control winding are mounted in Stator current is doubly fed Into the machine without electric brush and slip ring hence improving robustness and security can be achieved In this configuration． Up to now the domestic study on BDFM is just confined to laboratory and there is no practical system used In Industrial applications，so It is necessary to go deep into its research.
In this paper systemstic research on variable－frequency adjustable－speed drive based on BDFM Is carried out．Beginning with its historical development，The research In this paper has established a fundamental for the practical application of BDFM，and will promote the BDFM designing, modeling and controlling．
Key words： brushless doubly-fed machine; the system of variable－frequency adjustable－speed; the analyse of BDFM characters.
