Effect of PMSM sizing on the energy efficiency of an electro-hydraulic forklift

This paper investigates the effect of a permanent magnet synchronous machine (PMSM) drive on the efficiency of an electric energy recovery system of a hydraulic forklift. The control of the system is implemented directly with a permanent magnet AC servo motor drive without control valves. The paper provides accurate evaluation of the hydraulic system and the electric part of the working machine. An analysis of the theoretical model is made and the model is verified by practical results. Finally, possible improvements of the efficiency in the suggested system are estimated.