Woodward VariStroke-I, Product Manual, Page: 24 / 88

Manual 26727 VariStroke-I (VS-I) Electro-hydraulic Actuator
Woodward 22
The formulas above are valid for double acting cylinders. For spring-assist actuators, additional spring
force and its direction has to be taken in to account.
Extending Slew Rate: Configurable
Retracting Slew Rate: Configurable
Note : Slew Rates for Remote Servo Applications may be 10–15% slower due to pressure drop on
servo-cylinder piping.
It is highly recommended that inlet supply pressure not decrease by
more than 10% of nominal value during slew/step.
Position Accuracy: ±1% of full stroke
Position Repeatability: ±0.5% of full stroke
MLDT Temperature Drift: 0.04% /°C
Failsafe Operation: Internal return spring on servo valve spool force the hydraulic power cylinder
to extend or retract (part number depended) in case of electrical signal loss.
Additionally for spring-assist power cylinder internal spring installed in the
cylinder generates force toward the fail save position.
Make sure that the VS-I hydraulic connections are installed correctly.
Equipment damage is possible if the hydraulic connections are
attached incorrectly (backwards). Reversed hydraulic connects will
cause the actuator to operate backwards, making the fail-safe position
opposite of where the user expects it to be.
Overspeed /
Overpressure
Never close the drain line when supply pressure is present on the VS-I
unit, otherwise the control output pressure can increase suddenly and
cannot be controlled by the input setpoint. This could cause the
turbine to overspeed.
Table 2-3. Environmental Specifications
Ambient Temperature: (–40 to +85) °C / (–40 to +185) °F
Vibration Resistance: MIL-STD 810F, M514.5A, Cat. 4
(0.015 G ² /Hz, 1.04 Grms)
Shock Resistance: US MIL-STD-810C method 516.2, procedure 1
(10 G Peak, 11 ms duration, saw tooth)
Corrosion resistance: Two part epoxy paint coating. Designed for outdoor conditions
Ingress Protection
(IEC 60529, IEC 60079-0):
IP66
Table 2-4. Electrical Specifications
Supply Voltage: (18 to 32) V (dc), 24 V (dc) nominal (use cable at least 1.5 mm ² / 16
AWG)
Hold-up time: 7 ms @ 2 A (dc) LAT current
Current Consumption: 2.3 A (MAX) at steady state @ 24 V
10 A transient (100 ms maximum)
Demand Signals #1, 2: (4 to 20) mA into 200
Ω
. >70 dB CMRR. Common Mode Voltage
Range ±50 V (dc), Accuracy 0.1% of full scale @ 25 °C
Released