Woodward VariStroke-I User manual

Product Manual 26727
(Revision F, 8/2015)
Original Instructions
VariStroke-I (VS-I)
Electro-hydraulic Actuator
Installation and Operation Manual

General
Precautions
Read this entire manual and all other publications pertaining to the work to be
performed before installing, operating, or servicing this equipment.
Practice all plant and safety instructions and precautions.
Failure to follow instructions can cause personal injury and/or property damage.
Revisions
This publication may have been revised or updated since this copy was produced.
To verify that you have the latest revision, check manual
26455 , Customer
Publication Cross Reference and Revision Status & Distribution Restrictions, on
the publications page of the Woodward website:
www.woodward.com/publications
The latest version of most publications is available on the publications page. If
your publication is not there, please contact your customer service representative
to get the latest copy.
Proper Use
Any unauthorized modifications to or use of this equipment outside its specified
mechanical, electrical, or other operating limits may cause personal injury and/or
property damage, including damage to the equipment. Any such unauthorized
modifications: (i) constitute "misuse" and/or "negligence" within the meaning of
the product warranty thereby excluding warranty coverage for any resulting
damage, and (ii) invalidate product certifications or listings.
Translated
Publications
If the cover of this publication states "Translation of the Original Instructions"
please note:
The original source of this publication may have been updated since this
translation was made. Be sure to check manual
26455 , Customer Publication
Cross Reference and Revision Status & Distribution Restrictions, to verify whether
this translation is up to date. Out-of-date translations are marked with . Always
compare with the original for technical specifications and for proper and safe
installation and operation procedures.
Revisions—Changes in this publication since the last revision are indicated by a black line
alongside the text.
Woodward reserves the right to update any portion of this publication at any time. Information provided by Woodward is
believed to be correct and reliable. However, no responsibility is assumed by Woodward unless otherwise expressly
undertaken.
Manual 26727
Copyright © Woodward 2013–2015
All Rights Reserved

Manual 26727 VariStroke-I (VS-I) Electro-hydraulic Actuator
Woodward i
Contents
WARNINGS AND NOTICES............................................................................V
ELECTROSTATIC DISCHARGE AWARENESS ................................................. VI
REGULATORY COMPLIANCE .......................................................................VII
CHAPTER 1. GENERAL INFORMATION...........................................................1
Introduction.............................................................................................................1
VS-I Integrated and Remote Construction .............................................................3
VS-I Remote Servo Only Construction...................................................................9
CHAPTER 2. SPECIFICATIONS ....................................................................13
Physical and Performance Specifications ............................................................13
Environmental Specifications ...............................................................................14
Electrical Specifications........................................................................................14
Cylinder Position Sensor Requirements (Remote Servo Only)...........................15
Hydraulic Specifications .......................................................................................15
Special Ambient Temperature Specifications / Allowances .................................17
Stability Specifications..........................................................................................18
Diagrams ..............................................................................................................20
CHAPTER 3. INSTALLATION........................................................................24
Receiving Instructions ..........................................................................................24
Unpacking Instructions .........................................................................................24
Installation Instructions .........................................................................................25
CHAPTER 4. SERVICE TOOL INSTALLATION................................................46
Setup ....................................................................................................................46
Installing the VariStroke-I Service Tool ................................................................47
Connecting to the VariStroke-I .............................................................................49
CHAPTER 5. CALIBRATION AND MONITORING.............................................51
Introduction...........................................................................................................51
System Information...............................................................................................51
System Information Page .....................................................................................53
Configuration and Calibration...............................................................................54
Cylinder Configuration ..........................................................................................56
Manual Operation .................................................................................................62
CHAPTER 6. CONFIGURATION....................................................................63
Input Configuration ...............................................................................................63
Output Configuration ............................................................................................65
Advanced Configuration .......................................................................................67
Linearization .........................................................................................................68
Alarms/ Shutdown ................................................................................................68
Saving and Loading Settings................................................................................70
CHAPTER 7. REPAIR AND TROUBLESHOOTING ...........................................71
General.................................................................................................................71
Servo Valve / Hydraulic Cylinder Replacement....................................................71
Troubleshooting....................................................................................................72
Maintenance .........................................................................................................79
CHAPTER 8. PRODUCT SUPPORT AND SERVICE OPTIONS...........................80
Product Support Options ......................................................................................80
Product Service Options.......................................................................................80
Returning Equipment for Repair...........................................................................81
Replacement Parts ...............................................................................................82
Engineering Services............................................................................................82

VariStroke-I (VS-I) Electro-hydraulic Actuator Manual 26727
ii Woodward
Contacting Woodward’s Support Organization ....................................................82
Technical Assistance............................................................................................83
CHAPTER 9. ASSET MANAGEMENT AND REFURBISHMENT SCHEDULING
PERIOD .....................................................................................................84
CHAPTER 10. LONG-TERM STORAGE REQUIREMENTS ................................84
APPENDICES OUTLINE DRAWINGS AND INSTALLATION FEATURES...............85
Appendix A – V25 Servo, 4-inch (100mm) Bore Integrated Servo-Cylinder
(V25TD-10XX) ......................................................................................................86
Appendix B – V25 Servo, 6-inch (150mm) Bore Integrated Servo-Cylinder
(V25TD-15XX) ......................................................................................................88
Appendix C – V45 Servo, 6-inch (150mm) Bore Integrated Servo-Cylinder
(V45TD-15XX) ......................................................................................................90
Appendix D – V45 Servo, 8-inch (200mm) Bore Integrated Servo-Cylinder
(V45TD-20XX) ......................................................................................................92
Appendix E – V45 Servo, 10-inch (250mm) Bore Integrated Servo-Cylinder
(V45TD-25XX) ......................................................................................................94
Appendix F – V45 Servo, 8-inch (200mm) Bore 3-inch (75mm) Stroke Integrated
Spring Assist Servo-Cylinder (V45TT-2007-MUE) ...............................................96
Appendix G – V25 Servo, 4-inch (100mm) Bore Remote Servo-Cylinder (V25RD-
10XX)....................................................................................................................98
Appendix H – V25 Servo, 6-inch (150mm) Bore Remote Servo-Cylinder (V25RD-
15XX)..................................................................................................................101
Appendix I – V45 Servo, 6-inch (150mm) Bore Remote Servo-Cylinder (V45RD-
15XX)..................................................................................................................104
Appendix J – V45 Servo, 8-inch (200mm) Bore Remote Servo-Cylinder (V45RD-
20XX)..................................................................................................................107
Appendix K – V45 Servo, 10-inch (250mm) Bore Remote Servo-Cylinder
(V45RD-25XX)....................................................................................................110
Appendix L – V45 Servo, 8-inch (200mm) Bore 3-inch (75mm) Stroke Remote
Spring Assist Servo-Cylinder (V45RT-2007-MUE).............................................113
Appendix M – Remote Servo Version ................................................................116
REVISION HISTORY ..................................................................................118
DECLARATIONS .......................................................................................119

Manual 26727 VariStroke-I (VS-I) Electro-hydraulic Actuator
Woodward iii
Illustrations and Tables
Figure 1-1. VariStroke-I, Key Features...................................................................3
Figure 1-2. VariStroke-I Remote, Key Features.....................................................4
Figure 1-3. Hydraulic Power Cylinder. Stroke Adjustment Options .......................5
Figure 1-4. Application Example ............................................................................7
Figure 1-5. VariStroke-I Remote Servo, Key Features ..........................................9
Figure 1-6. Application Example ..........................................................................10
Figure 1-7. Nomenclature and Ordering Number Encoder ..................................12
Figure 2-1. Basic Device Block Diagram without Trip Function ...........................20
Figure 2-2. VS-I Integrated Hydraulic Schematic.................................................20
Figure 2-3. VS-I Remote Hydraulic Schematic.....................................................21
Figure 2-4. VS-I Remote Servo Hydraulic Schematic ..........................................21
Figure 2-5. VS-I Spring Assist Integrated Hydraulic Schematic...........................22
Figure 2-6. VS-I Spring Assist Remote Hydraulic Schematic ..............................22
Figure 3-1a. VS-I Integrated Product Installation Interface—Bolting Pattern and
Installation Features ........................................................................25
Figure 3-1b. VS-I Integrated Product Installation Interface—Bolting Pattern and
Installation Features ........................................................................26
Figure 3-2a. VS-I Remote. Product Installation Interface—Bolting Pattern and
Installation Features ........................................................................27
Figure 3-2b. VS-I Remote. Product Installation Interface—Bolting Pattern and
Installation Features ........................................................................28
Figure 3-3. VS-I Remote Servo. Product Installation Interface—Bolting Pattern.29
Figure 3-5. VS-I Lifting Positions..........................................................................30
Figure 3-5. Incorrect Lifting Method .....................................................................31
Figure 3-6. Suggested Configuration ...................................................................33
Figure 3-7. Electrical Wiring Diagram...................................................................34
Figure 3-8. Power Supply Input Connections.......................................................35
Figure 3-9. Correct Wiring to Power Supply Input................................................36
Figure 3-10. Example of Incorrect Wiring to Power Supply Input ........................36
Figure 3-11. Recommended Wiring Strain Relief.................................................37
Figure 3-12. Analog Input Connections................................................................38
Figure 3-13. Final Cylinder Position Feedback Analog Input Connections..........39
Figure 3-14. Cylinder Position Sensor wiring diagram when using VS-1 internal
power ...............................................................................................39
Figure 3-15. Cylinder Position Sensor wiring diagram when using External Power
Supply..............................................................................................40
Figure 3-16. Example of Incorrect Cylinder Position Sensor connection when
using External Power Supply...........................................................40
Figure 3-17. Cylinder Position Connectors...........................................................40
Figure 3-18. Cylinder Position Sensor Connection Scheme with MTS Sensor ...40
Figure 3-19. Analog Output Connection...............................................................41
Figure 3-20. Discrete Inputs Connections ............................................................42
Figure 3-21. Discrete Output Connections ...........................................................43
Figure 3-22. CAN Ports Connections ...................................................................44
Figure 4-1. Service Port Connections ..................................................................46
Figure 4-2. Home Screen .....................................................................................49
Figure 5-1. System Information Page...................................................................53
Figure 5-2. Configuration/Calibration Page ..........................................................54
Figure A-1a. V25TD-10XX Integrated Installation Dimensions ............................86
Figure A-1b. V25TD-10XX Integrated Installation Dimensions ............................87
Figure A-2a. V25TD-15XX Integrated Installation Dimensions ............................88
Figure A-2b. V25TD-15XX Integrated Installation Dimensions ............................89
Figure A-3a. V45TD-15XX Integrated Installation Dimensions ............................90
Figure A-3b. V45TD-15XX Integrated Installation Dimensions ............................91
Figure A-4a. V45TD-20XX Integrated Installation Dimensions ............................92
Figure A-4b. V45TD-20XX Integrated Installation Dimensions ............................93

VariStroke-I (VS-I) Electro-hydraulic Actuator Manual 26727
iv Woodward
Figure A-5a. V45TD-25XX Integrated Installation Dimensions ............................94
Figure A-5b. V45TD-25XX Integrated Installation Dimensions ............................95
Figure A-6a. V45TT-2007-MUE Integrated Spring Assist Installation
Dimensions ......................................................................................96
Figure A-6b. V45TT-2007-MUE Integrated Spring Assist Installation
Dimensions ......................................................................................97
Figure A-7a. VS-I Remote Maximum Allowable Distance between Actuator and
Servo................................................................................................98
Figure A-7b. V25RD-10XX Remote Installation Dimensions ...............................99
Figure A-7c. V25RD-10XX Remote Installation Dimensions .............................100
Figure A-8a. VS-I Remote Maximum Allowable Distance between Actuator and
Servo..............................................................................................101
Figure A-8b. V25RD-15XX Remote Installation Dimensions .............................102
Figure A-8c. V25RD-15XX Remote Installation Dimensions .............................103
Figure A-9a. VS-I Remote Maximum Allowable Distance between Actuator and
Servo..............................................................................................104
Figure A-9b. V45RD-15XX Remote Installation Dimensions .............................105
Figure A-9c. V45RD-15XX Remote Installation Dimensions .............................106
Figure A-10a. VS-I Remote Maximum Allowable Distance between Actuator and
Servo..............................................................................................107
Figure A-10b. V45RD-20XX Remote Installation Dimensions ...........................108
Figure A-10c. V45RD-20XX Remote Installation Dimensions ...........................109
Figure A-11a. VS-I Remote Maximum Allowable Distance between Actuator and
Servo..............................................................................................110
Figure A-11b. V45RD-25XX Remote Installation Dimensions ...........................111
Figure A-11c. V45RD-25XX Remote Installation Dimensions ...........................112
Figure A-12a. VS-I Remote Maximum Allowable Distance between Actuator and
Servo..............................................................................................113
Figure A-12b. V45RT-2007-MUE Remote Spring Assis Installation
Dimensions ....................................................................................114
Figure A-12c. V45RT-2007-MUE Remote Spring Assis Installation
Dimensions ....................................................................................115
Figure A-13a. Typical VS-I Remote Servo Installation Dimensions ...................116
Figure A-13b. Typical VS-I Remote Servo Installation Dimensions ...................117
Table 2-1. VS-I Installation Drawings ...................................................................23
Table 3-1. VS-I Installation Bolts and Bolting Torques Recommendation ...........28
Table 7-1. VS-I General Troubleshooting Guide ..................................................73
Table 7-2. VS-I Demand Faults Guide .................................................................74
Table 7-3. VS-I Power Supply Faults ...................................................................75
Table 7-4. VS-I Feedback Faults..........................................................................76
Table 7-5. VS-I Temperature Faults.....................................................................77
Table 7-6. Performance Faults .............................................................................78
Table 7-6. Performance Faults (continued)..........................................................79
Table 7-7. Internal Faults......................................................................................79

Manual 26727 VariStroke-I (VS-I) Electro-hydraulic Actuator
Woodward v
Warnings and Notices
Important Definitions
This is the safety alert symbol. It is used to alert you to potential
personal injury hazards. Obey all safety messages that follow this
symbol to avoid possible injury or death.
DANGER—Indicates a hazardous situation which, if not avoided, will result
in death or serious injury.
WARNING—Indicates a hazardous situation which, if not avoided, could
result in death or serious injury.
CAUTION—Indicates a hazardous situation which, if not avoided, could
result in minor or moderate injury.
NOTICE—Indicates a hazard that could result in property damage only
(including damage to the control).
IMPORTANT—Designates an operating tip or maintenance suggestion.
Overspeed /
Overtemperature /
Overpressure
The engine, turbine, or other type of prime mover should be
equipped with an overspeed shutdown device to protect against
runaway or damage to the prime mover with possible personal injury,
loss of life, or property damage.
The overspeed shutdown device must be totally independent of the
prime mover control system. An overtemperature or overpressure
shutdown device may also be needed for safety, as appropriate.
Personal Protective
Equipment
The products described in this publication may present risks that
could lead to personal injury, loss of life, or property damage. Always
wear the appropriate personal protective equipment (PPE) for the job
at hand. Equipment that should be considered includes but is not
limited to:
Eye Protection
Hearing Protection
Hard Hat
Gloves
Safety Boots
Respirator
Always read the proper Material Safety Data Sheet (MSDS) for any
working fluid(s) and comply with recommended safety equipment.
Start-up
Be prepared to make an emergency shutdown when starting the
engine, turbine, or other type of prime mover, to protect against
runaway or overspeed with possible personal injury, loss of life, or
property damage.
Automotive
Applications
On- and off-highway Mobile Applications: Unless Woodward's control
functions as the supervisory control, customer should install a
system totally independent of the prime mover control system that
monitors for supervisory control of engine (and takes appropriate
action if supervisory control is lost) to protect against loss of engine
control with possible personal injury, loss of life, or property damage.

VariStroke-I (VS-I) Electro-hydraulic Actuator Manual 26727
vi Woodward
Battery Charging
Device
To prevent damage to a control system that uses an alternator or
battery-charging device, make sure the charging device is turned off
before disconnecting the battery from the system.
Electrostatic Discharge Awareness
Electrostatic
Precautions
Electronic controls contain static-sensitive parts. Observe the
following precautions to prevent damage to these parts:
Discharge body static before handling the control (with power to
the control turned off, contact a grounded surface and maintain
contact while handling the control).
Avoid all plastic, vinyl, and Styrofoam (except antistatic versions)
around printed circuit boards.
Do not touch the components or conductors on a printed circuit
board with your hands or with conductive devices.
To prevent damage to electronic components caused by improper
handling, read and observe the precautions in Woodward manual
82715 , Guide for Handling and Protection of Electronic Controls,
Printed Circuit Boards, and Modules.
Follow these precautions when working with or near the control.
1. Avoid the build-up of static electricity on your body by not wearing clothing
made of synthetic materials. Wear cotton or cotton-blend materials as much
as possible because these do not store static electric charges as much as
synthetics.
2. Do not remove the printed circuit board (PCB) from the control cabinet
unless absolutely necessary. If you must remove the PCB from the control
cabinet, follow these precautions:
Do not touch any part of the PCB except the edges.
Do not touch the electrical conductors, the connectors, or the
components with conductive devices or with your hands.
When replacing a PCB, keep the new PCB in the plastic antistatic
protective bag it comes in until you are ready to install it. Immediately
after removing the old PCB from the control cabinet, place it in the
antistatic protective bag.

Manual 26727 VariStroke-I (VS-I) Electro-hydraulic Actuator
Woodward vii
Regulatory Compliance
Product Compliance Code: Product certifications are dictated by the product
model number, and traceable per the product serial number. For information on
which hazardous locations any particular VariStroke is rated for, refer to the
Model Number and Model Number information below. The Model Number can be
found on the nameplate of the VariStroke.
European Compliance for CE Marking
EMC Directive: Declared to 2004/108/EC COUNCIL DIRECTIVE of
15 December 2004 on the approximation of the laws
of the Member States relating to electromagnetic
compatibility.
ATEX – Potentially Declared to 94/9/EC Council Directive of 23 May 1997
Explosive Atmospheres on the Approximation of the Law of the Member
Directive: States concerning equipment and protective
systems intended for use in potentially explosive
atmospheres.
Zone 2, Category 3, Group IIG, Ex nA IIC T4 Gc
Certificate: Sira 14ATEX5029X
Zone 1, Category 2, Group IIG, Ex d IIB T4 Gb
Certificate: Sira 14ATEX1028X
North American Compliance:
CSA: CSA Certified for Class I, Div. 1, Groups C & D
Class I, Division 2, Groups A, B, C, & D, T4 at 85 °C
For use in Canada and the United States
Other European and International Compliance:
IECEx: Certified for use in hazardous locations
Zone 1, Category 2, Group IIG, Ex d IIB T4 Gb
Zone 2, Category 3, Group IIG, Ex nA IIC T4 Gc
Certificate: IECEx CSA 13.0041
Machinery Directive: Compliant as partly completed machinery with
Directive 2006/42/EC of the European Parliament
and the Council of 17 May 2006 on machinery.

VariStroke-I (VS-I) Electro-hydraulic Actuator Manual 26727
viii Woodward
Pressure Equipment Compliant as “SEP” per Article 3.3 to Pressure
Directive: Equipment Directive 97/23/EC of 29 May 1997 on
the approximation of the laws of the Member States
concerning pressure equipment.
Ingress Protection Rating:Product meets the IEC/EN 60529 Ingress Protection
rating of IP66.
Special Conditions for Safe Use
Wiring must be in accordance with North American, European, or other
International wiring methods as applicable, and in accordance with the authority
having jurisdiction.
For Zone 1 / Division 1: Conduit seals must be installed within 18 inches
(457 mm) of the conduit entry when used in zone 1 / Division 1 hazardous
locations.
Field wiring must be suitable for at least +85 °C and 10 °C above the maximum
fluid and ambient temperatures.
The maximum hydraulic oil temperature is 70 °C continuous.
The VS-I actuator must be used in ambient temperature range from –40 °C to
+85 °C.
The following have a maximum constructional gap (ic) less than that required by
Tables 1 and 2 of EN 60079-1 and hence are as detailed below:
Linear Electro-Hydraulic Actuator, Model VariStroke-I
Flame Path Max Gap, ic (mm)
Comment
Min. width of joint L
(mm) Comment
Spool to Spacer 0.079 13.46
Sleeve to Spacer 0.079 12.85
Sleeve to Sleeve 0.048 14.76
Sleeve to Housing 0.076 15.85
Sensor to Plate 0.08 36.25
Plate to Housing 0.10 22.91
Plate to Housing 0.10 20.22
Plate to Plate 0.10 22.91
Connect external safety ground terminal to earth ground.
Compliance with the Machinery Directive 2006/42/EC noise measurement and
mitigation requirements is the responsibility of the manufacturer of the machinery
into which this product is incorporated.
The risk of electrostatic discharge is reduced by permanent installation of the
valve, proper connection of the equipotential ground lugs, and care when
cleaning. That valve should not be cleaned unless the area is known to be
non-hazardous.

Manual 26727 VariStroke-I (VS-I) Electro-hydraulic Actuator
Woodward ix
Under certain extreme circumstances, the non-metallic parts incorporated in the
enclosure of this equipment may generate an ignition-capable level of
electrostatic charge. Therefore the equipment shall not be installed in a location
where the external conditions are conducive to the build-up of electrostatic
charge on such surfaces. This is particularly important if the equipment is
installed in a Zone 0 location. In addition, the equipment shall only be cleaned
with a damp cloth.
Transient protection for the VariStroke-I is to be provided externally by the end
user. The transient protection device is to be set at a level not exceeding 140%
of the peak rated voltage.
The installation of the VariStroke-I shall only be within a Pollution Degree 2
environment as defined in IEC 60664-1.
EXPLOSION HAZARD—Do not connect or disconnect while circuits
are live unless area is known to be non-hazardous.
Substitution of components may impair suitability for Zone 2
applications.
The external ground lugs shown on the installation drawing must be
properly connected to ensure equipotential bonding. This will reduce
the risk of electrostatic discharge in an explosive atmosphere.

Manual 26727 VariStroke-I (VS-I) Electro-hydraulic Actuator
Woodward 1
Chapter 1.
General Information
Introduction
The VariStroke-I is a linear electro-hydraulic actuator that utilizes a double-acting
or spring-assist power cylinder with integrated electronic driver module, servo
valve, and redundant MLDTs (Magnetostrictive Linear Displacement Transducer)
– based position feedback sensors to precisely control steam turbine valves. The
actuator’s driver module accepts one or two (redundant) 4–20 mA demand
setpoints and compares these setpoints to the sensed actuator shaft position to
accurately control output shaft position.
The actuator’s output shaft position is controlled by a digital controller with an
internal rotary servo valve that ports supply oil to and from its power cylinder
piston. This actuator’s digital controller architecture allows it to perform stable
position control during normal conditions, and also respond quickly to desired
valve step changes during system or plant transients. The actuator output force
is generated only by oil pressure for double-acting power cylinder. For the spring
assist actuator output force is a combination of force from hydraulic pressure and
spring. Spring assist cylinder is still working as double acting actuator but it has a
spring installed inside the cylinder. Spring can be mounted either on the piston or
rod side and it generates force toward the fail safe position. There are 3 different
spring force categories for each cylinder diameter, except for 8” and 10” cylinder
bores which need 4 spring force categories to cover application needs. The
springs are rated at about ~1.5%, ~2.5%, ~5.5% and ~10.5% of stall force at 500
psi supply pressure.
As a means of protecting the turbine, an internal servo valve-return spring forces
the actuator to a failsafe position to safely close turbine control valves upon any
internal unit failure (electrical input power failure, position sensor failure,
processor failure, etc.). Additionally for the spring assist power cylinder the
actuator spring assists in closing the valve in the event of the loss of oil pressure
and helps to maintain fail safe position.
The VariStroke-I actuator is a product family with many different models available
for purchase depending on the force, stroke, and redundancy required. Two, V25
and V45 servo sizes are available. Smaller servo – V25 (flow 68-169 l/min) works
with 4 and 6 inch actuators while servo V45 (flow 212-530l/min) works with 6, 8
and 10 inch actuators. Cylinders are available with standard bore diameters and
standard stroke ranges. The VariStroke’s unique “variable stroke” capability also
allows users to customize/set the actuator’s exact maximum stop position in the
field to meet their requirement. The VariStroke-I is available as an integrated unit,
or as a Remote Servo kit where the cylinder can be mounted up to 3 meters
(approx. 10 feet) away from the servo. Both servos are available as Servo Only
option for users who wish to use their own hydraulic cylinder.
The VariStroke-I is factory and/or field configurable via a computer-based service
tool. The actuator’s PCI Service Tool uses a simple user-friendly format to allow
users to easily configure, calibrate, and adjust all internal functions and response
settings. The VariStroke-I also includes a 4–20 mA output channel to indicate
output shaft (control valve) position, and unit alarm and shut down relay outputs
for use as unit health and status indications.
The total installed cost for this fully integrated actuator is low because it has been
completely assembled and tested at the factory. This greatly reduces OEM and
end-user fabrication time, testing time, and site assembly time.

VariStroke-I (VS-I) Electro-hydraulic Actuator Manual 26727
2 Woodward
The VariStroke Actuator offers the following benefits to the user in comparison to
other electro-hydraulic actuators:
Dirt Tolerance—The VariStroke-I actuator is specifically designed for steam
turbine applications where turbine lube oil is also used to power the hydraulic
turbine control valve actuator(s). Steam turbine applications can be extremely
challenging for hydraulic control valve actuators as dirt, metal shavings, water,
and other contaminants (babbitt, ammonia, etc.) are common in such oil
systems. Also due to the high temperatures at which steam turbines operate,
turbine oil breakdown is common, resulting in the creation of a sludge-type
substance and the varnishing of internal system components. However, the
VariStroke-I actuator is designed to operate reliably within such challenging
applications. Its corrosion-resistant materials, single moving rotary valve, 222 N
(50 lbf) of chip shear force, and self-cleaning port design allow it to operate in
such applications without experiencing undesirable sticking or dragging.
Valve Rack Linearization—Since flow-through single and staged inlet steam
valves tend to be non-linear throughout their flow range, turbine controls must be
de-tuned to compensate for instability or sluggish control points throughout this
range. As a way of allowing turbine control optimization, the VariStroke-I includes
an 11-point linearization table to allow turbine OEMs or users to compensate for
poor valve linearization by digitally linearizing the control-to-valve flow
relationship.
Side Load Capability—A common problem with turbine actuators is oil leaking
from their output shaft due to connection to valve rack linkages which have an
arc-type of motion. This motion results in side loading of the actuator shaft, and
after long periods may result in shaft-seal wear and resultant oil leakage.
Designed for a continuous side load of up to 10% of actuator output, the
VariStroke-I actuator incorporates a high-force precision bearing and triple-seal
technology on its output shaft to solve this typical application problem.

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VS-I Integrated and Remote Construction
The VariStroke-I is made up of the following major components (Figure 1-1):
1. Hydraulic Power Cylinder
2. Rotary Servo Valve
3. Feedback Sensors: MLDT (Magnetostrictive Linear Displacement
Transducer) – for power cylinder position controlling
4. Integrated electronic driver module (PCB)
Figure 1-1. VariStroke-I, Key Features
Hydraulic Power Cylinder
with Integrated MLDT
Position Sensor(s)
Electronic Driver Module
Enclosure
Rotary Servo Valve
with Integrated
Position Sensor

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The VariStroke-I Remote Servo Kit (Figure 1-2) contains the same primary
components as Integrated version, This kit allows the Hydraulic Power Cylinder
to be mounted separately from the servo in applications where space is
constrained.
Figure 1-2. VariStroke-I Remote, Key Features
Hydraulic Power Cylinder
with Integrated MLDT
Position Sensor(s)
Rotary Servo Valve
with Integrated
Position Sensor
Electronic Driver Module Enclosure

Manual 26727 VariStroke-I (VS-I) Electro-hydraulic Actuator
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Hydraulic Power Cylinder
The simple and robust design of VS-I hydraulic cylinder (Figure 1-3) is capable of
consistent performance for extended periods in challenging environments.
Hydraulic cylinder is designed to operate in wide range of hydraulic pressures
and with high oil contamination. The actuation stroke range can be adjusted
precisely using PC service tool allowing the same actuator to accommodate a
variety of strokes.
The hydraulic power cylinder is designed to be field replaceable in turbine shut
down condition.
Figure 1-3. Hydraulic Power Cylinder. Stroke Adjustment Options

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Rotary Servo Valve
The servo valve has four ports: Supply, two Control Ports, and Drain/Tank. With
the hydraulic valve in its middle position, all ports are blocked. As the valve
rotates, the supply is connected to a control port while simultaneously connecting
the drain to the other control port. The combined action of the servo position
controller and cylinder position controller modulate the power cylinder position as
necessary to match the input demand.
Additionally, the Remote Servo has an OVBD (Over Board Drain) port which is
permanently connected to drain. This port can (optionally) be connected to the
OVBD connection on Hydraulic Power Cylinder to drain any leakage pass the
primary rod seal.
A unique function of the software is a periodic, symmetrically opposed impulse
which flushes silt and debris from the servo valve without causing undue wear
called “Silt Buster”. At the interval and amplitude selected by the user, this
function provides a very rapid motion of the hydraulic valve allowing any silt to be
flushed to the drain passage. This motion is followed immediately by a step of
equal amplitude in the opposite direction. The opposing symmetry of the impulse
results in no net change in fluid volume to the controlled servo valve, and thus
does not interrupt the control of the turbine. This unique function provides a
higher degree of stability, reliability, and silt resistance.
If the unit detects any diagnostic shut down condition, or if the detected
diagnostic condition prevents reliable control, or if a loss of power occurs, the
servo valve return spring forces the valve to connect the appropriate control
pressure to drain causing the cylinder to move to the fail-safe position.
Servo Valve Actuator
The VS-I uses a rotary limited angle torque (LAT) actuator. The permanent
magnet rotor is directly coupled to the servo valve.
The position of the rotor is measured by a solid state integrated circuit on the
PCB which detects the orientation of the sensing magnet on the shaft. The
H-bridge drive is regulated by the microprocessor to precisely control the servo
valve position and maintain the cylinder stroke position demand.
Electronic Driver Module (PCB)
The printed circuit board (PCB) is mounted on top of the housing. The PCB
performs the following tasks:
Power Supply
Isolated Input and Outputs
Dual Redundant Demand inputs
Dual Redundant inputs for Final Cylinder Feedback
Microprocessor based control
Actuator H-Bridge Drive
Current Limiting for Thermal Protection
Advanced Diagnostics
Discrete Outputs for Fault, Alarm and Shutdown Enunciation

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Figure 1-4. Application Example
The shield connections for the Analog Output (terminal #20), CAN1 (terminal
#23) and CAN2 (terminal #29) are through capacitors only as indicated in the
wiring section of this manual.
The power supply section performs the EMI filtering on the (18 to 32) V (dc) input
voltage and generates controlled voltages for several electronics sub-systems.
The power supply system is monitored for proper operation. If input voltage or
internal power systems are detected outside of allowable operating ranges, a
diagnostic alarm will be enunciated.
Calibration and configuration of alarms and shut down and redundancy operation
are configurable via the PC Service Tool.
The primary demand and redundant demand / feedback input signals are
designed for a (4 to 20) mA control signal. Each input signal is EMC protected.
Discrete outputs are provided for alarm and shut down enunciation. An internal
LED also is illuminated when a fault condition is detected. Cover needs to be
removed to see this LED. The configurable discrete output can be customized to
output a variety of enunciations using the PC Service Tool. All of the discrete
outputs are configurable for normally-open or normally-closed action using the
PC Service Tool.

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Cylinder Position Control
The cylinder position controller adjusts the hydraulic power cylinder position to
match the feedback signal to the demand.
Both the servo position controller and cylinder position controller are monitored to
ensure accurate tracking.
The position controller regulates a pulse width modulated (PWM) drive signal to
the actuator. The drive current to the actuator is regulated, transiently allowing up
to 10 Amps to be provided to move the actuator at its maximum speed and
torque. A steady state current limit becomes active after a period of a few
seconds to protect the actuator and electronics.