Key Technical Specifications
- Product Model: 9907-147
- Manufacturer: Woodward
- Application System: ProTech 203 turbine / rotating machinery overspeed protection
- Power Input: 18–32 VDC, nominal 24 VDC
- Speed Input: Passive or active magnetic pickup (MPU) sensors
- Frequency Range: 100 Hz to 32 kHz
- Speed Accuracy: ±(0.05% × Trip Point in Hz + 2 Hz)
- Trip Logic: 2-out-of-3 voting, de-energize-to-trip relay design
- Communication: Modbus RTU over RS485
- Operating Temperature: -25 °C to +60 °C
- Front Interface: Three 2-line, 16-character LCDs with keypad and status LEDs
- Form Factor: Panel mount metal enclosure with key lock for configuration access
- Safety Compliance: SIL 3 capable per IEC 61508
Product Introduction
This Woodward 9907-147 ProTech 203 unit monitors prime mover speed via three magnetic pickups for independent overspeed protection. It operates separately from the main governor control loop. Single-channel protection creates single-point failure risk. This unit uses 2oo3 voting logic, with typical trip response under 40 ms, to reduce false trips while maintaining reliable overspeed shutdown.
Installation & Configuration Guide
Preparation (10 min) Gather ESD wrist strap, MPU probe cables, 24 VDC power supply, multimeter. Confirm machine lockout. Photograph existing wiring before disconnection. Removal (5–10 min) Lock out all DC power. Label MPU, relay trip, and communication wiring. Remove panel mounting fasteners. Pull connectors straight; do not tug individual wires. Installation (10 min) Fit replacement unit into panel cutout. Secure mounting hardware. Wire MPU probes, trip relays, 24 VDC supply and Modbus terminals. Torque terminals to OEM recommended value. Power-On & Test (10 min) Restore 24 VDC supply. Verify front-panel power LEDs. Use keypad to set trip speed. Perform simulated speed injection test to validate 2oo3 trip sequence.
Troubleshooting Quick Reference
| Symptom | Likely Cause | Check Action |
|---|---|---|
| All three channels no speed reading | No MPU excitation or open MPU wiring | Measure MPU signal at terminal block; check for broken pickup cable |
| One channel speed reading erratic | Damaged MPU or loose sensor wiring | Swap MPU between channels to isolate sensor vs. unit fault |
| Trip occurs with no overspeed | Mismatched trip setpoint or faulty voting channel | Compare trip values across three modules; run internal self-test |
| Modbus RTU cannot connect | Wrong baud rate, parity or bus termination | Verify Modbus address and line termination resistor |
| Front panel LED dim or intermittent | Degraded 24 VDC supply or loose power terminal | Measure DC input voltage under load; retighten power wiring |
Dimensions, Mounting & Wiring Notes
- H×W×D: 310.4 mm × 482.6 mm × 142.7 mm
- Mounting method: Panel mount, cutout installation for control cabinet front face
- Terminal notes: Separate MPU signal cables from high-current power cables. Use shielded twisted pair for MPU and Modbus wiring. Ground shield at one end only.
FAQ
Q: Can this overspeed system work with a single magnetic pickup? A: No. The ProTech 203 2oo3 voting design requires three independent MPU inputs for full safety function. Q: What happens if one of the three internal modules fails? A: The remaining two channels continue 2oo3 protection. A fault alarm activates on the front panel and via Modbus. Q: Is this unit factory new sealed? A: Woodward discontinued the 9907-147. Available stock is surplus or fully refurbished. Q: I have a steam turbine with existing ProTech 203. Can I directly swap this unit? A: Yes. Confirm trip setpoints, MPU type and Modbus parameters before replacement. Plan work during machine outage. Q: What is the main risk during MPU wiring work? A: Induced noise can create false speed signals. Run MPU cables away from variable frequency drive and high-current wiring. Q: How long does your pre-shipment functional test run? A: 24-hour continuous powered burn-in plus discrete speed injection testing for all three channels. Q: Can I use this system as the primary governor for turbine speed control? A: No. This is dedicated overspeed protection. It does not replace the main governor for normal speed regulation.
