Sytronix Rexroth Green Power System. A virtuous collaboration case study
The Sytronix Rexroth Green Power System for energy sustainability
The electric propulsion mechanism is one of the vital components of a motor-pump system consisting of an electric drive circuit, an energy storage system and a transmission body. Above all, when such a system requires high energy density for a rapid dynamic response, its design should be compatible to meet a series of requirements , such as optimal acceleration, high torque, efficient and adjustable speed and, last but not least, an energy efficiency.
In the general energy conversion efficiency of the electric propulsion, the systems currently available vary according to different parameters: machine power losses, harmonic distortions, torque pulsations, torque, etc.
There are numerous research projects that continue to improve the energy efficiency of hydraulic systems and beyond, with various solutions already available on the market.
With the advancement of technology, there are numerous approaches that can improve the energy efficiency of hydraulic systems, such as methods of recovering hybrid electro-hydraulic energy, load sensitivity mechanisms, multi-actuator hybrid hydraulic systems with controlled displacement (DC ), independent metering valves, bionic multistage power supply, pump controlled actuators, hydraulic transformers that include a hydraulic vane motor and an oscillating plate type pump.
The partnership among Bosch Rexroth, Tecno Fluid Service and an automotive sector Company
In this wake of innovation, the collaboration of Tecno Fluid Service with Bosch Rexroth continues to give great results. Sytronix Rexroth Green Power is the result of this collaboration and the case study treated here represents its synthesis. In fact, in collaboration with an important company operating in the automotive sector (which we will call Company A here), it has been possible to accelerate the development of an innovative technology capable of recording significant energy savings in the hydraulic motor-pump systems on plastic molding systems “Injection presses”.
The partnership used for Sytronix Rexroth Green Power among Rexroth, TFS and the Automotive Company has made it possible to combine and share knowledge of three different important basic fields: control, fluid mechanics and material technology.
The skills on control systems were necessary to characterize the dynamics of each component, to control the dynamic performance, position, pressure and other parameters of a specific component or circuit, where electronics play a decisive role in this field.
Fluid mechanics provided the tools to understand fluid behavior, the forces of static and dynamic fluids on components, phenomena such as water hammer and cavitation.
The choice of materials with adequate elasticity, hardness, friction properties etc. was a decisive factor in the design of power components.
The results of the collaboration have allowed us to overcome the limits of a normal circuit based on the use of an inverter, including:
– does not require replacement of the motor / pump unit
– the pump used has a fixed flow rate
– it does not provide any feedback because there are no feedback sensors
– the hydraulic circuit of the machine does not assume a lean conformation because the variation in pressure and flow will continue to be managed by the circuit components (limiting and proportional valves)
– absence of monitoring-government of the states of least use or “quiet” during the cyclogram operations, as the plant operates at constant power to allow pressure / flow variations by the logical valves.
The results obtained by the Sytronix Green Power System
Conversely, Sytronix Rexroth Green Power is based on the implementation of various innovative solutions, including:
– replacement of the motor-pump unit with brushless type for the motor and variable flow rate for the pump
– the pump switches from fixed displacement and displacement to fixed displacement and variable displacement pump
– the software with the drive and the system sensors guarantee constant feedback and modulation of the number of engine revolutions and pump flow adjustment to interact in real-time mode according to the hydraulic power required generated by the cycle cycle of the press
– the hydraulic part of the machine assumes one leaner shape according to the fact that the pressure / flow variation is managed by the Sytronix system instead of the pressure relief valves
– the state of least use or “quiet” during the cycle-gram operations with less use of pressure / flow allows a lower consumption of FEM generating greater savings.
The result obtained from the experimentation in the Sytronix Rexroth Green Power partnership on an injection molding press equipped with a traditional 55Kw asynchronous motor can be summarized as follows: energy consumption for one hour-work with a 61 sec cycle has gone from 19.84 Kw / h at 6.06 Kw / h, thus recording an energy saving of 69.56% (download results here).
Other advantages obtained with Sytronix Rexroth Green Power on the system are shown here:
1) qualitative performance: from open loop operation it has gone to closed loop operation
2) reduction of oil overheating: the consequence of operating the pump only when movement is required has allowed less heating of the oil and consequently a saving of energy in relation to the water cooling unit
3) fluid movement: although for a fraction of a second the time that Sytronix passes at 0 rpm per minute at the required number of revolutions, it has softened the movements without giving margin to the cycle time, obtaining considerable savings on maintenance cycles
4) lower operating noise of the hydraulic pump.