Servovalve at rest – MTS Series 256 Servovalve User Manual

Page 15

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Series 256 Servovalve Product Information

Introduction

15

Functional Diagram

Servovalve at rest

The servovalve’s controlling element is the torque motor, which receives an
electrical input from the controller. A flapper is attached to the armature of the
torque motor. The flapper moves from side to side as the armature moves in
response to control signals from the controller. The flapper assembly is
mechanically attached to the armature. There are two nozzles, one on each side of
the flapper.

Because the nozzle-flapper valve is the first control point of hydraulic fluid, it is
called the first stage. As long as there is no command for actuator motion, the
flapper is centered between the two nozzles.

At the same time, pressurized hydraulic fluid entering the valve is applied
equally to both sides of the spool, which does not move. This is the second stage.

MP-G046H-2

Return

Pressure

Pilot

Pressure

Third

Stage

Second

Stage

First

Stage

Fixed Orifice

Feedback

Spring

Lower

Polepiece

Flapper

Core

Third (Main)

Stage Spool

LVDT

Transformer

Pilot

Return

Filter

Second (Pilot)

Stage Spool

Nozzle

Armature

Coil

Magnet

Upper Polepiece

Hydraulic

Actuator

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