Siemens SINAMICS S120 System Manual page 246

Appendix
A.3 Hydraulic
Valve amplifier
The functions of the integral valve amplifier utilize analog electronics, and are illustrated in
the following block diagram.
The main functions include:
● Supply and evaluation of the position sensor (AC/DC converter)
● Comparison of the setpoint input signal with valve spool actual value
● Formation of manipulated variable via a PID controller for the output stage
● Clocked output stage with pulse length modulation
The amplifier is calibrated to match the valve at the factory. The zero point is adjusted at the
NC when the system is being commissioned.
Figure A-14 Valve amplifier: Block diagram of directly controlled servo solenoid valves
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System Manual, 04/2015, 6SL3097-4BA00-0BP1
Hydraulic Drive