## 1 Introduction
The different configurations analyzed, starting from a traditional hydraulic architecture with low energy efficiency, are characterized by the introduction of the regenerative technique and variations in the unit for converting electrical energy into hydraulic energy carried by the pressurized fluid. Five configurations, whose architecture is described below and summarized in Table 2, have been analyzed and compared. 1. Standard configuration: traditional architecture consisting of a round-case induction electric motor, a fixed-displacement vane pump, a pressure relief valve, and a standard directional control valve (DCV). 2. Regenerative configuration: standard configuration with DCV with regeneration A--hybrid. 3. High-low configuration: regenerative A--hybrid configuration in which the single fixed-displacement vane pump is replaced by two pumps of the same type, one with high flow rates and low maximum pressures, one with low flow rates and high maximum pressures. 4. VDP (variable-displacement pump) configuration: regenerative A--hybrid configuration in which the single fixed-displacement vane pump is replaced by a variable-displacement axial piston pump. 5. DCP (drive-controlled pump) configuration: regenerative A--hybrid configuration in which rotational speed of the asynchronous motor is continuously adjustable through an AC frequency converter. For a quantitative comparison of the energy efficiency of the studied configurations, it is necessary to perform an optimized dimensioning of the main components for each of them. For configurations 1 to 4, the sizing can be achieved by neglecting the angular acceleration or deceleration ramps that characterize the transition from one speed range to another, since for architectures that use an asynchronous motor fed directly from the grid, the inertial torques resulting from the acceleration or deceleration ramps can be neglected in a first approximation. On the other hand, the contribution of inertial torques becomes more relevant when the motor is fed by a frequency converter, since in this mode of operation the \begin{table}
\begin{tabular}{c c c c} \hline
**Configuration** & **Electric Drive** & **Pump** & **Directional Valve** \\ \hline Standard & Round-case induction electric motor & Fixed-displacement vane pump & Standard DCV \\ \hline Regenerative & Round-case induction electric motor & Fixed-displacement vane pump & DCV with regeneration A—hybrid \\ \hline High–low & Round-case induction electric motor & Two fixed-displacement & DCV with regeneration A—hybrid \\  & & vane pumps & DCV with regeneration A—hybrid \\ \hline VDP & Round-case induction electric motor & Variable-displacement axial & DCV with regeneration A—hybrid \\  & & piston pump & DCV with regeneration A—hybrid \\ \hline DCP & AC frequency converter + & Fixed-displacement vane pump & DCV with regeneration A—hybrid \\  & & vane induction electric motor & \\ \hline \end{tabular}
\end{table} 
Table 2: Considered and compared power drive architectures for a press for semi-finished brass products. motor is subjected to speed variations of very large amplitude, even in very short periods, which leads to non-negligible inertia torques. For architecture 5, both an approximate sizing, in which the inertial contribution was neglected, and a more accurate sizing, in which the inertial contribution, was also considered, were performed. The remainder of the paper is organized as follows. Section 2 is devoted to the description of the variable speed and force hydraulic blanking press, the selection of the hydraulic cylinder and fluid, the theoretical analysis of a valve-controlled hydraulic system, and the description of all architectural configurations considered. In Section 3, the results are presented, in terms of estimated absorbed power (active and reactive), mean active electric power on the working cycle, and hourly cost of energy absorbed by the electricity grid, for each configuration considered.