Siemens SINAMICS S120 - Hydraulic; Servo Solenoid Valves; General; A.3 Hydraulic

Appendix
A.3 Hydraulic
Hydraulic Drive
System Manual, 04/2015, 6SL3097-4BA00-0BP1
235
A.3
Hydraulic
A.3.1
Servo solenoid valves
A.3.1.1
General
The servo solenoid valve is the final control element in an electro-hydraulic control loop. It
converts the electrical manipulated variable U=-10...+10 V into the hydraulic variables
pressure p and flow rate Q, and thus into a cylinder movement.
Sliding spool principle
These valves are of the sliding-spool type. A valve spool with 4 control edges moves inside a
steel sleeve, the control bore of which is connected to the 4 ports in the valve casing.
The main stages of precontrolled valves do not typically have the steel sleeve, in which case
the control geometry is represented directly by the valve casing.
The individual ports in the valve casing are:
● P: Pressure port (inlet)
● T: Tank port (return)
● A and B: Operating ports (cylinder)
The valve spool slides steplessly through 3 switching positions (continuous valve).
Figure A-1 Sliding spool principle