Abstract: As for the fixed hydraulic-secondary-control-system, a project of only using three-phrase induction machine to drive the secondary system is presented, so that the restriction of recycling energy within the hydraulic-secondary-control-system is broken through. This project is simple and excellent, which can put electric network-hydraulic-secondary-control-system into running reversibly, and widen the range of recycling energy from mechanical-hydraulic-system to electric-hydraulic-me- chanical-system, so that the advantage of saving energy of secondary control system is made the most of. The stability and security of system, especially the question of induction machine- constant pressure variable pump/motor running reversibly in second quadrant is analyzed. The feasibility of this project is proved.

Key words: Running reversibly Recycling energy, Secondary control, Three-phrase induction machine