Woodward 9905-970

Description

Technical Specifications

Functional Features

• Dual independent servo drive channels (CH1 and CH2) — supports main valve plus control valve, or dual-actuator parallel operation from a single unit
• High-current servo amplifier — delivers ±250 mA continuous to the actuator torque motor, sufficient for Woodward 9907 and 9903 series actuators up to 10,000 lbf thrust
• Integrated LVDT/RVDT signal conditioning — accepts ±10 VAC or 4-20 mA position feedback, provides automatic excitation for LVDT sensors at 2.5 kHz or 10 kHz
• Digital PID position control with adaptive auto-tuning — onboard digital PID controller regulates valve position based on command signal and feedback, eliminates need for separate analog positioner
• Built-in servo amplifier — no external servo amplifier required, reduces wiring and installation complexity
• Position ramp generator — programmable valve opening and closing ramp rates for smooth startup and shutdown
• Anti-windup PID algorithm — prevents integral windup during actuator saturation, ensures fast recovery from large disturbances
• Current limiting — programmable per-channel current limit protects actuator torque motor from overcurrent damage
• Position deviation alarm — configurable alarm relay activates if valve position deviates from command by more than preset threshold
• Trip relay output — 1 Form C trip relay de-energizes turbine trip solenoid on position fault or communication loss
• Auxiliary relay outputs — 3 programmable Form C auxiliary relays for status indication, alarm, or interlock functions
• Analog output — 1 configurable 4-20 mA output for real-time valve position transmission to DCS/SCADA
• Event logging — onboard non-volatile memory stores up to 500 time-stamped events including position faults and trip history
• Self-diagnostics — continuous monitoring of servo current, position feedback signal quality, internal CPU health, and relay status
• Modbus RTU/TCP and EtherNet/IP communication — receives valve position command from governor or DCS and transmits position feedback and status
• Web-based configuration — full parameter programming via Woodward GMT (Governor Management Tool) software over Ethernet or USB
• Redundant configuration support — dual power input terminals for redundant 24 VDC supplies in SIL 3 applications
• Built-in LVDT excitation — provides 2.5 kHz or 10 kHz AC excitation for LVDT sensors, eliminates external LVDT power supply
• Communication with Woodward 505/5437 governors — native integration for speed-to-position control loop closure

Performance Parameters

Material Composition

Structural Features

• Compact DIN-rail mountable enclosure — fits standard 35mm top-hat rail or panel-mount with rear bracket
• Modular I/O architecture — removable terminal blocks for servo output, position feedback, power, and communication
• Front-accessible LED indicators — status LEDs for power, run, alarm, trip, servo channel 1, servo channel 2, and communication activity
• Sealed front panel — IP54 protection rating (dust and splash resistant)
• Rear cable entry — 6 cable glands (2× PG11 for position feedback, 2× PG16 for servo output, 2× PG11 for power/comm) with knockouts
• Vibration-damped mounting — internal rubber grommets isolate PCB from enclosure vibration
• EMC shielding — full metal enclosure with grounded shielding gasket between front and rear sections
• Service access — hinged front bezel allows terminal access without full panel removal
• Heat dissipation — internal heatsink fins on servo amplifier module, forced air cooling via brushless DC fan (24 VDC)
• Redundant configuration support — dual power input terminals for redundant 24 VDC supplies
• Test button — front-panel push button for trip relay verification test
• Position feedback terminals — dedicated LVDT/RVDT input terminals with automatic excitation selection (2.5 kHz or 10 kHz)
• Servo output terminals — heavy-gauge terminals rated for 10A continuous to actuator torque motor
• Fuse protection — internal 2A fast-blow fuse per servo channel for overcurrent protection
• USB configuration port — front-panel USB Type-B port for direct PC connection to Woodward GMT software
• Ethernet port — rear-panel RJ-45 connector for Modbus TCP and EtherNet/IP
• RS-485 port — rear-panel DB-9 connector for Modbus RTU
• Calibration adjustment screw — accessible from outside housing for field recalibration without disassembly

Working Principle

The Woodward 9905-970 operates as a digital closed-loop valve position controller with integrated servo amplifier. The microprocessor receives a valve position command signal (4-20 mA or ±50 mA) from the host governor (such as a Woodward 505, 5437, or 8440) or from a DCS/PLC via the command input. Simultaneously, the unit receives valve position feedback from an LVDT or RVDT sensor mounted on the actuator or valve stem. The LVDT signal is conditioned by the internal signal conditioning circuit, which provides automatic AC excitation at 2.5 kHz or 10 kHz and converts the AC position signal to a DC voltage proportional to valve stroke. The microprocessor compares the commanded position against the actual position feedback and calculates the position error. The onboard digital PID controller with adaptive auto-tuning processes this error and generates a corrective current output sent to the IGBT servo amplifier stage. The servo amplifier delivers a ±250 mA current to the actuator torque motor, which generates a force proportional to the current. This force drives the hydraulic spool valve inside the servo actuator, which directs high-pressure hydraulic oil to one side of the actuator piston, moving the turbine valve to the commanded position. The LVDT continuously reports the new position back to the 9905-970, closing the loop. The unit also monitors servo current for overcurrent faults, position deviation for stuck valve detection, and communication status for governor signal loss. If any fault is detected, the trip relay de-energizes within 50 ms, sending a trip signal to the turbine trip solenoid. All events are time-stamped and stored in non-volatile flash memory and transmitted via Modbus RTU/TCP or EtherNet/IP to the plant DCS or SCADA.

Advantages and Highlights

• Integrated servo amplifier — eliminates separate servo amplifier cabinet, reduces wiring by 60%, saves panel space
• Dual independent channels — supports main valve plus control valve from a single unit
• High output current ±250 mA — drives Woodward 9907/9903 actuators up to 10,000 lbf thrust without external amplification
• Built-in LVDT excitation — no external LVDT power supply required, auto-detects LVDT type and excitation frequency
• Digital PID with adaptive auto-tuning — eliminates manual PID tuning, provides tunable and repeatable valve control
• Drop-in replacement for Woodward 9907-010/9907-011 and 505F positioner — same footprint, same I/O wiring, same connector pinout
• SIL 2 certified (SIL 3 with redundancy) — meets functional safety requirements per IEC 61508
• Non-volatile event memory — retains 500 events through power loss, supports post-trip analysis
• Web-based configuration (GMT software) — full programming via standard Ethernet USB or Ethernet, no proprietary hardware tools
• Wide temperature range — operates from -20°C to +70°C, suitable for outdoor and harsh industrial environments
• Low power consumption — < 10 Watts, compatible with 24 VDC uninterruptible power supplies (UPS)
• Modbus RTU/TCP, EtherNet/IP dual protocol — integrates with any DCS, PLC, or SCADA platform
• Front-panel relay test button — allows periodic trip relay verification without system shutdown
• Anti-windup PID — prevents integral windup during actuator saturation, ensures fast disturbance recovery
• Built-in position ramp generator — programmable valve opening and closing rates protect actuator from water hammer
• Native integration with Woodward governors — seamless speed-to-position control loop with 505, 5437, and 8440 series

Applicable Industries

Model Series Comparison (Woodward 9900 / 9905 Family)

Installation Requirements

• Mounting Location: Install in a clean, dry, vibration-controlled environment within 0°C to +50°C ambient temperature
• Mounting Orientation: Vertical or horizontal DIN-rail mount; maintain minimum 2 inches (50 mm) clearance above and below unit for airflow
• Vibration Isolation: Use rubber vibration isolators if mounting surface vibration exceeds 2g RMS
• Power Wiring: Use shielded twisted-pair cable, 18 AWG minimum, for 24 VDC power input; connect positive and negative to designated terminals
• Command Input Wiring: Use shielded twisted-pair cable, 22 AWG minimum, from governor command output to 9905-970 input; maintain minimum 6 inches (150 mm) separation from power cables
• Position Feedback Wiring: Use shielded twisted-pair cable, 22 AWG minimum, from LVDT/RVDT to 9905-970 input; do not exceed 100 feet (30 m) without signal boosting
• Servo Output Wiring: Use shielded cable, 16 AWG minimum, from 9905-970 servo output to actuator torque motor; do not exceed 50 feet (15 m) without signal boosting
• Grounding: Connect chassis ground to plant equipment ground bus using green/yellow wire, minimum 14 AWG
• Cable Gland Torque: Tighten cable glands to 15 to 20 in-lbs (1.7 to 2.3 Nm) per manufacturer specification
• Communication Wiring (Modbus RTU): Use shielded twisted-pair, 22 AWG to 24 AWG, maximum 4,000 feet (1,200 m) at 9600 baud; for EtherNet/IP, use Cat5e or Cat6 shielded Ethernet cable, maximum 100 meters (328 feet) per segment
• Redundant Power: For SIL 2/SIL 3 applications, connect dual 24 VDC power supplies to redundant power terminals
• Trip Relay Wiring: Use 14 AWG minimum wire for trip relay contacts; wire to turbine trip solenoid per OEM specifications
• LVDT Wiring: Use shielded twisted-pair cable, 22 AWG minimum; do not mix LVDT wires with power cables in the same conduit
• Environmental Sealing: Install IP66-rated cable glands if unit is exposed to moisture or dust
• Clearance: Maintain minimum 6 inches (150 mm) clearance from high-voltage cables (> 600 VAC)
• Actuator Compatibility: Verify actuator model is Woodward 9907, 9903, 9907A, or 9903A before connecting servo output
• LVDT Compatibility: Verify LVDT type is ±10 VAC or 4-20 mA; do not connect 0-10 VDC LVDTs without signal converter

Usage Precautions and Notes

• Never apply power to the 9905-970 without all I/O connections properly terminated — open position feedback loops cause false position readings and unstable valve control
• Verify LVDT polarity before energizing — incorrect polarity causes erratic position display and unstable control
• Do not exceed ±250 mA on servo output channels — overcurrent damages the IGBT output stage and actuator torque motor
• Do not exceed 15 VAC on LVDT input channels — overvoltage damages the LVDT signal conditioning circuit
• Replace the 24 VDC power supply filter capacitor every 5 years — electrolytic capacitors degrade over time and cause power supply ripple
• Perform a full functional test including position deviation alarm every 12 months per API 670 and NFPA 85 requirements
• Do not modify firmware without Woodward-authorized service personnel — unauthorized firmware changes void SIL certification
• Lock the front panel after configuration using the provided security screws to prevent unauthorized parameter changes
• Record all configuration changes in the plant maintenance log — include date, technician name, and parameter values changed
• Do not operate the 9905-970 with the front bezel removed — exposure to live terminals creates electrical hazard
• Verify communication settings (baud rate, node address, protocol) match the governor configuration before connecting to the network
• In the event of a position feedback signal loss, the 9905-970 will trip on position deviation — this is a failsafe design, not a fault condition
• Do not use the 9905-970 for safety-instrumented functions without SIL certification verification — confirm SIL rating matches the application safety integrity level
• Battery backup for 24 VDC power is mandatory for SIL 2/SIL 3 installations — power loss must not cause uncontrolled turbine shutdown
• Store spare units in a climate-controlled environment, 10°C to 35°C, with desiccant packs — moisture ingress damages PCB conformal coating
• Calibrate LVDT sensors annually — LVDT drift causes position control inaccuracy over time
• All installation and commissioning must be performed by a certified Woodward service technician or authorized third-party integrator per Woodward installation manual WM-0025
• When using the 9905-970 with a Woodward 505 governor, verify the governor command output is configured for 4-20 mA or ±50 mA — mismatch causes governor fault
• Do not connect the 9905-970 analog output to a DCS input with a different signal range — 4-20 mA to 4-20 mA only; do not connect to 0-10 VDC inputs without a signal converter
• The 9905-970 provides LVDT excitation; do not apply external LVDT power to the same sensor — dual power sources damage the LVDT
• Servo output cables must be routed separately from control signal cables — electromagnetic interference from servo cables corrupts LVDT feedback signals
• Verify actuator torque motor resistance matches the 9905-970 output rating — connecting an actuator with resistance outside the specified range causes overheating or insufficient drive current
• Do not bypass the internal fuse on any servo channel — the fuse protects the IGBT output stage from catastrophic failure
• Perform a position deviation alarm test during commissioning — simulate position feedback loss and verify alarm relay activates within 50 ms
• Verify all relay outputs are wired to the correct turbine protection circuits — incorrect wiring causes failure to shut down on trip condition
• All torque wrenching and bolting operations on mounting hardware must follow ASME PCC-1 — use calibrated tools and correct torque values