Woodward 9905-971

Description

Product Category
Digital Engine Governor / Speed Controller / Load Sharing Controller / Actuator Driver

Key Functions

• Engine Speed Control — Maintains setpoint speed under varying load conditions with digital PID regulation
• Isochronous Speed Control — Holds exact setpoint speed (0% droop) for single-generator or grid-connected applications
• Droop Speed Control — Programmable droop from 1% to 10% for parallel generator load sharing
• Load Sharing — Distributes real power (kW) equally among parallel generators using droop characteristic
• Fuel Limiting — Restricts maximum fuel delivery to prevent engine overload and protect turbocharger
• Starting Control — Manages crank and run fuel quantities during engine start sequences
• Overspeed Protection — Automatic fuel shutoff on engine overspeed with configurable trip point and delay
• Underspeed Protection — Alarm and shutdown on low engine speed
• Reverse Power Protection — Detects reverse power flow (motoring) and alarms or trips
• Governor Alarm Outputs — Provides relay contacts for alarm and shutdown signaling
• Local/Remote Mode Selection — Supports both local manual override and remote automatic control
• Fail-Safe Positioning — Drives actuator to safe position (fuel cut or full fuel) on signal loss

Technical Specifications

Actuator Output Specifications

Communication Interfaces

Protection Features

• Overspeed Trip — Configurable trip point 102% to 115% of setpoint, adjustable delay 0 to 30 seconds
• Underspeed Trip — Configurable trip point 85% to 98% of setpoint, adjustable delay 0 to 30 seconds
• ESD Actuation — Fuel cutoff within 100 ms of ESD signal activation
• Actuator Coil Open Circuit Detection — Immediate fault alarm, actuator drives to safe position
• Actuator Coil Short Circuit Detection — Immediate fault alarm, output current limited to 2 A
• Position Sensor Failure Detection — Loss of feedback triggers safe shutdown
• Overtemperature Protection — Internal thermal shutdown at +105°C junction temperature
• Supply Voltage Monitor — Low voltage alarm at <18 VDC, high voltage alarm at >32 VDC
• CAN Bus Timeout — Actuator drives to safe position within 200 ms of CAN communication loss
• Reverse Polarity Protection — Internal fuse blows on reverse polarity connection (fuse rating: 2 A fast-blow)

Control Modes

Material Composition

Structural Features

• DIN rail mountable on 35 mm top-hat rail (EN 60715)
• Front-accessible terminal blocks for all wiring connections
• Membrane keypad with 2-line LCD display for local configuration
• 3 LED status indicators: Power (green), Run (green), Alarm (amber)
• DIP switches on PCB for mode selection and fail-safe configuration
• Conformal-coated PCB for moisture, dust, and chemical resistance
• Integrated EMC filter on power and signal inputs
• Compact footprint — fits in standard DIN rail enclosures

Working Principle

The 9905-971 receives a frequency signal from a magnetic pickup sensor mounted on the engine flywheel or gear. The internal 16-bit microcontroller converts the frequency to engine RPM and compares it to the setpoint speed. The error signal is processed through a PID (Proportional-Integral-Derivative) control algorithm with feed-forward compensation. The controller outputs a 125 Hz PWM signal to the fuel actuator, adjusting fuel rack position to minimize the speed error. For load sharing, the controller adjusts the speed setpoint based on the load reference input, creating a controlled droop characteristic. All position data, diagnostic status, and alarm conditions are transmitted back to the engine controller via CAN bus in real time at 500 kbps.

Advantages and Highlights

• Fully Digital Architecture — No mechanical linkages, no wear parts in the controller
• High Precision — Speed regulation within ±0.1% of setpoint
• Fast Response — <100 ms transient response
• Remote Configuration — Full parameter set via CAN bus or Modbus RTU
• Wide Input Compatibility — Supports MPU, variable reluctance, and Hall-effect speed sensors
• Redundant Protection — Multiple independent overspeed and underspeed protection channels
• Compact Footprint — 130 mm x 90 mm x 55 mm, fits in standard DIN rail enclosures
• Long Service Life — No mechanical fatigue, MTBF exceeds 50,000 hours
• Dual Input Redundancy — CAN bus and analog input provide command redundancy
• Fail-Safe Operation — Drives actuator to safe position on loss of speed signal or CAN communication

Applicable Industries

• Power Generation — Diesel and gas generator sets (standby, prime, continuous)
• Marine Propulsion — Auxiliary and main engine governors
• Oil and Gas — Compressor drivers, pump drivers, wellhead power units
• Mining — Diesel generator sets for underground and surface operations
• Rail — Auxiliary power units (APUs)
• Industrial — Any diesel/gas engine requiring electronic speed control
• Telecommunications — Backup power generator sets
• Data Centers — Standby and prime power generation

Compatible Engine Controllers

Compatible Actuator Models (Woodward)

Model Series Cross-Reference

Certifications and Compliance

Part Number Breakdown

Installation Requirements

• Mount on 35 mm DIN rail (EN 60715) or directly on the fuel actuator using the supplied bracket
• Maintain minimum 50 mm clearance on all sides for ventilation
• Route speed sensor cable away from high-current power cables (minimum 150 mm separation)
• Use shielded twisted-pair cable for speed signal (minimum 0.5 mm² cross-section)
• Ground the controller chassis to the engine block ground point using minimum 6 AWG copper wire
• Supply voltage must be 24 VDC regulated with less than 5% ripple
• Torque all terminal connections to 1.2 Nm (10.6 in-lbs)
• Verify speed sensor air gap is within 0.3 mm to 1.5 mm (0.012″ to 0.060″) before startup
• Perform a no-load speed calibration after initial installation
• Do not operate the unit in environments exceeding +85°C ambient temperature
• Verify CAN bus termination resistors (120 Ω) are installed at both ends of the bus

Usage Precautions

• Do not exceed the maximum supply voltage of 32 VDC — permanent damage to internal components will occur
• Do not reverse the polarity of the power supply — internal 2 A fast-blow fuse will open
• Do not operate the unit in environments exceeding +85°C ambient temperature
• Do not expose the PCB to chemical solvents — conformal coating will degrade
• Perform a no-load position calibration after initial installation and after any actuator replacement
• Perform a functional test of all protection relays every 6 months
• Do not modify the firmware using unauthorized tools — this voids the warranty immediately
• The unit contains no user-serviceable components — contact Woodward for all repairs
• Replace the silicone rubber grommets if the DIN rail mounting is compromised
• Verify CAN bus termination resistors (120 Ω) are installed at both ends of the bus at all times
• Do not connect or disconnect the terminal blocks while the unit is powered
• Store the unit in a dry environment with relative humidity below 85%

Warranty

• Standard Warranty: 24 months from date of shipment
• Extended Warranty: Available up to 60 months (Woodward Protect program)
• Warranty Exclusions: Damage caused by reverse polarity, overvoltage, physical impact, unauthorized firmware modification, or operation outside specified environmental limits

Document Reference Numbers