Woodward 9907-345 Electronic Overspeed Trip Device

Product Overview

The Woodward 9907-345 is an electronic overspeed trip device from the ProTech 203 Overspeed Protection System. It is designed to protect critical rotating equipment — including diesel engines, gas turbines, steam turbines, and other prime movers — from catastrophic overspeed conditions. This model features a de-energize-to-trip configuration with three independent magnetic pickup units (MPUs) and a two-out-of-three (2oo3) voting relay architecture, providing fault-tolerant protection with high reliability.

Key Technical Specifications

• Product Type: Electronic Overspeed Trip Device
• Series: Woodward ProTech 203
• Identical Part Number: 8200-201
• Trip Type: De-energize-to-Trip (low voltage DC)
• Input Voltage: 24 V DC
• Voltage Range: 18–32 VDC
• Speed-Sensing Frequency Range: 100 Hz – 32 kHz (250 Hz – 25 kHz per some sources)
• MPU Failed Timeout Range: 100 – 25,000 rpm
• Operating Temperature: -25°C to +60°C
• Dimensions: 19" W × 12.244" H × 5.62" D
• Weight: Less than 14 lbs (6.35 kg)
• Enclosure Rating: IP54, NEMA 4/4X
• Manual Number: 85205
• Origin: USA

System Architecture

• Three Independent MPU Units (A, B, C) — each with dedicated CPU and speed-sensing circuitry
• Two-Out-of-Three (2oo3) Voting Relays — each unit controls 2 voter relays (6 total)
• Separate Operator Interface per speed-sensing unit
• Independent 24V DC Power Supply per unit
• Individual CPU Status LEDs for each subsystem

Key Features

• Hot Replacement Capability: Subsystems can be replaced without tripping the prime mover (when supply power is disconnected first)
• Built-in Self-Test: Automatic diagnostic testing of all protection functions
• Remote Reset: Enables remote acknowledgment and reset of trip conditions
• Key Lock: Prevents unauthorized parameter changes
• Multiple Alarm Outputs: Visual and audible alarms with LCD/LED error messages
• CPU Failure Indication: Dedicated failure detection for each processing unit

Applications

• Gas and steam turbine overspeed protection
• Diesel engine overspeed protection
• Compressor and pump drive protection
• Marine propulsion systems
• Power generation prime mover safety

Installation Guide

1. Mount in NEMA 4/4X rated panel or enclosure
2. Connect 24V DC power supply (18–32 VDC range)
3. Install three magnetic pickup sensors (MPUs) on prime mover shaft
4. Wire MPU signals to corresponding A, B, and C input terminals
5. Connect trip relay outputs to fuel valve or steam valve trip solenoids
6. Configure overspeed setpoint and timeout parameters via operator interface
7. Perform self-test and verify all three units show normal status

FAQ

Q: What is the difference between de-energize-to-trip and energize-to-trip?
A: De-energize-to-trip removes power to trip the prime mover (failsafe). This configuration cannot be changed after purchase — verify your system requirements before ordering.

Q: Can I replace a failed subsystem without shutting down?
A: Yes, if you disconnect the supply power to that subsystem first. The remaining two units maintain protection.

Q: How many voter relays does each unit control?
A: Each of the three speed-sensing units controls 2 voter relays, for a total of 6 relays.

Q: What enclosure rating is required?
A: The unit is rated for IP54 / NEMA 4/4X environments. Ensure your installation meets these requirements.

Model Selection Tips

• 9907-345 = De-energize-to-Trip / 24V DC / 2oo3 Voting / NEMA 4/4X
• Verify your prime mover requires de-energize-to-trip (failsafe) vs. energize-to-trip
• Confirm 24V DC control power availability (18–32 VDC range)
• Check MPU mounting location and cable routing for all three sensors
• For alternative trip configurations, consult Woodward ProTech 203 ordering guide