The proportional electro-hydraulic control systems allow the hydraulic parameters to be modulated on the basis of the electronic reference signals. They are the ideal interface between hydraulic and electronic systems and can be used in open or closed loop controls, to obtain rapid, gradual and precise movements required by modern installments and machinery.
The electro-hydraulic system represents a section of the entire automation architecture where information, controls and alarms can be transmitted "transparently" via fieldbus to the centralized electronic control unit and vice versa.
Proportional electro-hydraulics guarantees the following advantages over electromechanical systems:
The heart of the electro-hydraulic controls is the proportional valve which regulates the pressure P or the flow rate Q according to the input reference signal (usually ± 10 VDC). In particular, the proportional valve must be operated by an electronic regulator, which regulates the electric current to the valve solenoid according to the reference signal.
The solenoid converts the electric current into a mechanical force which drives the cursor against the contrast spring: the increase in current produces a corresponding increase in the thrust force and the consequent compression of the contrast spring, thus generating the movement of the cursor.
Proportional valves can be direct or pilot operated, with or without pressure/position transducer.
Proportional valves with transducer ensure better regulation accuracy. In the pilot operated versions, the proportional pilot valve regulates the flow rate and the pressure by acting on the main stage.
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