Perspectives on Component Downsizing in Electro-Hydraulic Variable-Speed Drive Networks

The field of electro-hydraulic variable-speed drive technology is expanding, and application areas are increasing across both stationary and mobile industry segments. Developments have mainly concerned standalone drives, and the effective compensation of asymmetric volume variation in cylinders, fully closed circuit functionalities and so forth. In multi-cylinder systems, conventional valve-controlled drives supplied by centralized power units, provide for flexible power distribution among cylinders but generally suffer from poor efficiencies. On the contrary, standalone electro-hydraulic variable-speed drives provide much improved efficiency in comparison, but suffer from inflexible power distribution necessitating maximum cylinder power to be installed for each actuator, hence resulting in potentially high cost levels. Component downsizing potentials of electro-hydraulic variable-speed drive systems with multiple cylinders have only been considered to a minor extend at this point. In this area, recently introduced electro-hydraulic variable-speed drive networks allow for a more flexible distribution of hydraulic power compared to standalone drives, while providing efficiencies on a similar level. Furthermore, such drive networks may eliminate the necessity for various auxiliary valves and potentially allow to reduce the number of variable-speed drives to be installed compared to standalone solutions. The study presented aims to demonstrate that components in electro-hydraulic variable-speed drive networks may be substantially reduced compared to standalone drive systems, via considerations on the dimensioning load cycles for a given application. A case study on a crane application is used to exemplify the downsizing potential, and results here demonstrate a reduction in the required installed power of up to 25% compared to standalone solutions.