DYNAMIC PERFORMANCE OF A HYDRAULIC SYSTEM DRIVEN BY A VARIABLE SPEED AC ELECTRIC MOTOR WITH ELECTRO-HYDRAULIC LOAD SENSING

Abstract: Hydraulic systems, transforming the mechanic energy into hydraulic energy to transfer it to a different mechanic system, are one of the most important R&D fields regarding energy saving. Many studies are carried out regarding energy saving in hydraulic systems, thus relatively more efficient system designs are improved step by step. In this study, a hydraulic test rig is used to simulate a 500 kN press brake metal forming machine driven by a variable speed with the aim of energy saving. In the drive system of the press brake machine, variable speed-controlled AC electric motor is used to drive a constant displacement a gear pump. By means of an electro-hydraulic load sensing method, the load pressure and flow rate under the specific operation condition are measured and send to this information to the control system for varying speed of the electric motor. Thus, the gear pump can provide the system requirements not more. This method can reduce to energy consumption. However, the dynamic performance of this drive system must be analyzed and compared to that of a proportional valve controlled conventional constant speed drive system to recognize the dynamic capability of the proposed variable speed drive method in the press brake machine. For this aim, the cycle phases of the press brake machine are simulated in experimental test rig to compare the dynamic performances of both drive options under different part load conditions. According to obtained results, prospective suggestions are presented.