In many systems and machines in the higher performance range, variable displacement pumps are used in order to transform the installed motor power as required, e.g. in fast forward movements or in powerful pressing processes. In this connection, the variable displacement pump takes over the function of a gear. DFEn are variable-speed system in which the energy-saving variable displacement pumps are combined with a variable-speed drive.
For classic hydraulics, constant pressure is produced, and the speed of the cylinders is limited with orifices or flow control valves so that the pressure in the system does not drop. However, this limitation causes high power losses. p/Q control systems are a better solution since the pump generates only the pressure and flow which is required for the process. This helps to realize much more energy efficient systems, but it requires a sequential procedure of the machine. Bosch Rexroth offers two Sytronix systems which are optimized for these cases of application: SvP 5020, SvP 7020 and SY(H)DFEn.
Sytronix type SvP (servo-variable pump drive) drive systems consist of a synchronous servo motor with permanent magnet and an easy-to-operate frequency converter. The systems are particularly quiet thanks to the use of internal gear pumps.