Specifications
Table Of Contents
- Electrohydraulic Valves...A Technical Look
- Electrohydraulic Valve Applications
- Electrohydraulic Valve Selection Guide
- How to select a Servo or Proportional Valve
- How toSelect, continued
- Electrohydraulic Technologies
- Types of Servo Systems
- General Terminology: Electric
- General Terminology: Hydraulic
- Hydraulic Characteristics
- Performance Characteristics
- Electrical Characteristics
- Electrical Characteristics
- Nozzle Flapper Servovalve Operation
- Servojet Servo-Proportional Valve Operation
- Direct Drive Servo-Proportional Valve Operation
- Practical Considerations when laying out EH Control Systems
- Practical Considerations, continued
- Routine Maintenance
- Routine Maintenance, continued
- Moog Worldwide
PERFORMANCE CHARACTERISTICS
Flow Gain: The no-load flow characteristics of Servo or
Proportional Valves can be plotted to show flow gain, symmetry
and linearity.Typical limits (excluding hysteresis effects) are shown
in Figure 4.
Linearity: The nonlinearity of control flow to input current will be
most severe in the null region due to variations in the spool null
cut.With standard production tolerances, valve flow gain about null
(within ±5% of rated current input) may range from 50 to 200% of
the normal flow gain.
Rated Flow Tolerance: ±10%
Symmetry: < 10%
Hysteresis: typically < 3% for servovalves, < .3% for proportional valves
Threshold: typically < .5% for servovalves, < .1% for proportional valves
Null Shift:
With temperature: 100˚F variation (56˚C) < ±2%
With acceleration: to 10 g < ±2%
With supply pressure: 1,000 psi change (70 bar) < ±2%
PERFORMANCE CHARACTERISTICS
20
40
60
80
-20
-40
-60
-80
20 40 60 80
-20-40-60-80
INPUT CURRENT–% RATED
CONTROL FLOW–% RATED
±10% LIMITS
200% SPECIFIED GAIN
50% SPECIFIED GAIN
-100
100
-100
100
20
-20
20
-20
50%
200%
FIGURE 4
Characteristics
Characteristics
Characteristics
11