Required Flow is normally given, Qreq Nominal valve drop ?p = 10 bar (145 psi) You must estimate pressure drops, To find a spool, solve…
Author: Jack
“Nominal Flow” for proportional spools is rated at ?p = 10 bar (145 psi) total, 5 bar per land Example 4WRA “Nominal Flow” is 7…
Proportional spools slide in cast body – No sleeve, in main stage (unlike a servo valve) – Robust construction similar to on/off directional valves –…
LVDT position feedback improves performance – Increased flow capacity – Higher Power Limit – Better Response Sensitivity – Better Hysteresis < 0.3%
Adding LVDT position feedback greatly improves resolution 0.2% Hysteresis
Improve accuracy and performance with position feedback on solenoid LVDT – Linear Variable Displacement Transformer Position transducer – short stroke High resolution Non-contacting Robust
Solenoid force vs. spring force positions spool Select one solenoid to control direction and flow 40% input Sol-a => 15% flow P-to-B 80% input Sol-b…
Solenoid force opposed by spring force = rate x displacement Spool position is constant, when forces are balanced Input (coil current) is directly proportional to…
Solenoid force opposed by pressure P x A (area seat 3) Input to amplifier changes solenoid current (output Force) 20% input => 20% pressure 80%…