Description
The Woodward 8525-971 is a digital driver board and electronic speed governor module designed for the precise control of prime movers, including industrial gas turbines, marine diesel engines, and locomotives. It serves as the critical interface between the system’s control electronics and the electro-hydraulic actuators (such as the UG MAS assembly), regulating mechanical speed and load sharing. It translates low-current control algorithms into specific milliamp (mA) driver signals required to position actuator valves under dynamic load conditions.
Commercial Availability & Terms
- Condition: New Original (Factory Sealed) or Refurbished (Fully Bench Tested) available based on current asset inventory.
- Warranty: 12-Month Functional Warranty from the date of shipment.
- Lead Time: Ships within 1 to 3 business days from central warehouse stock.
- Pricing Note: Listed price is indicative and changes with component availability. Contact our procurement team for a firm, formal quotation.
Technical Specifications
The following electrical and physical specifications outline the operational boundaries for the 8525-971 hardware module.
| Parameter | Value |
| Manufacturer | Woodward |
| Model / Part Number | 8525-971 |
| Product Type | UG MAS Driver Governor Board |
| Rated Input Voltage | 18 to 32 V DC (24 V DC Nominal) |
| Power Consumption | Less than 14 W |
| Actuator Driver Signal | 0 to 200 mA (for proportional or isochronous speed control) |
| Network / Signal Isolation | 1000 Vrms (0 to 60 Hz) |
| Response Time | Less than 5 ms |
| Operating Temperature | −10 to +55 °C (+14 to +131 °F) |
| Storage Temperature | −40 to +85 °C (−40 to +185 °F) |
| Dimensions | 30.0 cm × 20.0 cm × 25.0 cm (11.8 in × 7.9 in × 9.8 in) |
| Weight | Approximately 0.8 kg (1.76 lbs) |
Field Integration & Functional Diagnostics
1. Actuator Loop Calibration
The 8525-971 provides a 0 to 200 mA output loop to drive the electro-hydraulic actuator’s solenoid coils. During initial commissioning or replacement, the driver board’s null offset and gain adjustments must be matched to the specific mechanical travel of the governor valve. Field failure to calibrate these parameters can cause governor hunting, engine speed oscillation, or an overspeed trip during sudden load shedding.
2. Isolation and Noise Mitigation
The module features 1000 Vrms signal isolation to prevent ground loop currents from corrupting the milliamp speed-setting signal. When executing long cable runs from the main DCS or PLC rack to the engine-mounted governor housing, ensure that shielded twisted-pair cabling is used. Terminate the shield at the control panel chassis ground only to eliminate electromagnetic interference (EMI).
3. Built-In Fault Detection
The digital board monitors internal diagnostics for power bus stability. It features overvoltage, undervoltage, and overcurrent circuit protection. If the driver detects an open or short circuit on the actuator output loop, it drops the driver signal, signaling the mechanical governor to default to a fail-safe position.
Safety Warning: When integrating the driver into a gas turbine or diesel propulsion system, a separate, independent mechanical overspeed protection device must be installed. Do not rely solely on the electronic driver board to mitigate run-away overspeed events.
Frequently Asked Questions
What does the “UG MAS” designation mean?
The UG MAS designation refers to Universal Governor Milliamp Speed setting. This indicates that the driver is engineered to accept standard milliamp industrial inputs and drive specific electro-hydraulic governor links designed by Woodward for heavy-duty prime movers.
Can the 8525-971 operate in ambient marine engine room conditions?
The module is rated for operating temperatures up to +55 °C. If installed directly inside an engine room enclosure where ambient temperatures exceed this limit, forced-air cooling or panel ventilation is mandatory to prevent thermal drift in the analog driver circuitry.
What causes the driver board to output an unstable milliamp signal?
Unstable outputs are typically caused by input voltage fluctuations falling outside the 18 to 32 V DC window, or inductive noise leaking into the speed-setting loop. Verify input power cleanliness using an oscilloscope and ensure all high-voltage conduit runs are routed away from the driver signal lines.
