Abstract: The reasons of motor speed loss in variable-speed pump-control-motor governing system are analyzed. It is pointed out that motor speed loss caused by system leakage, electromotor characteristic and oil compressibility due to system pressure change. The control diagram of motor speed loss compensation is given based on system pressure feedback. The speed loss compensation coefficient caused by system leakage and electromotor characteristic and the speed loss compensation coefficient caused by oil compressibility are derived. For the variable-speed pump-control-motor governing system, the measurement and control programs are built in LabVIEW. On this basis, the experiment studies are respectively carried out under constant load, variable load and variable-speed. The speed loss compensation method under different conditions is obtained based on theoretical analysis and experimental study, and it is achieved that the system can compensate motor speed loss under different conditions.

Key words: Oil compressibility compensation coefficient, Pump-control-motor, Sectionalization linear compensation, Speed loss