ELECTRIC-HYDROSTATIC DRIVE SYSTEMS AND THEIR APPLICATION IN INJECTION MOULDING MACHINES

Abstract

The aim of the research work was to reveal the potential advantages and challenges of the electric-hydrostatic drive system, a new direct pump control concept. Measurements of component efficiency have proved that hydraulic components have a very good efficiency compared with variable-speed electric motors. Therefore, the total efficiency of the electric-hydrostatic drive at high load cannot be expected to be noticeably better than that of the conventional drive system comprising an asynchronous electric motor and a variable displacement hydraulic pump. The major advantages of the new motor-pump concept are reduction of power losses and noise during part-load and during idling. Due to the high overload capability of rare-earth electric motors, the dynamic performance of the electric-hydrostatic drive can be compared to that of many standard variable displacement pumps. That was evaluated by performance tests of the clamp unit of a plastics injection moulding machine.The electric-hydrostatic drive system increases the number of direct pump control concepts which a hydraulic project engineer can apply to design competitive hydraulic systems for customer applications.