An energy-saving method to reduce the installed power of hydraulic press machines

Hydraulic press machines (HPMs) are often preferred in metal processing for their high power-to-mass ratio, stiffness, and load capacity. Unfortunately, they are also known for their high energy consumption and low energy efficiency. The mismatch between installed and demanded power is the primary cause of low energy efficiency among HPMs. This paper proposes an energy-saving hydraulic drive system based on the flywheel energy storage system (FESS) to reduce the installed power and improve the energy efficiency. The FESS is used to store redundant energy when the demanded power is less than the installed power. During pressing with slow falling, the stored energy is recycled in combination with an AC motor to work against the heavy load. Furthermore, unlike traditional FESS's, the variable frequency drive (VFD) and specific control algorithm are adopted to improve the energy storage capacity of the FESS, as well as the operation and lifetime of the hydraulic drive system. The proposed method presents the first integration of both VFD and FESS into a hydraulic drive system. Using this method, the low energy efficiency caused by high installed power can be significantly improved, and the negative effects caused by mismatches between the installed and demanded power can be largely mitigated. Finally, a test platform is set up to verify the effectiveness of the proposed hydraulic drive system. The results show that the installed power and energy consumption are reduced by approximately 30% and 40%, respectively, based on the working characteristics of a traditional drive system. (C) 2019 Elsevier Ltd. All rights reserved.