Woodward 9907-147 ProTech 203 Two Out of Three Trip

The Woodward 9907-147 ProTech 203 Two Out of Three Trip is the 24 V DC de-energize-to-trip version of Woodward’s ProTech® 203 electronic two-out-of-three overspeed protection system. It senses prime-mover speed through three magnetic pickups (MPUs) using three identical, independent speed-sensing units whose trip relays are voted two-out-of-three, providing fail-safe overspeed shutdown fully independent of the prime-mover control system.

Key Features

• Digital overspeed trip device — three MPU speed inputs, three independent speed-sensing units
• Two-out-of-three (2oo3) voting of trip relays — single-unit failure does not compromise protection
• De-energize-to-trip design
• 24 V DC powered (all three units): 18–32 V DC, 5.12 W per unit
• Front-panel LEDs and digital displays: actual speed per probe, highest-speed signal, functional status
• On-line testing capability; modular design allows unit replacement while running
• Speed sampled every 5 ms; total response time 40 ms max
• Remote reset; built-in self-test frequency generator for on-line test of each unit

Technical Specifications

• Part Number: 9907-147
• Product Type: ProTech 203 Overspeed Protection System (digital, 2oo3 voting)
• Trip Configuration: De-energize-to-trip (loss of power trips — Woodward recommended)
• Supply (per unit): 24 V DC (18–32 V DC), 5.12 W per kernel
• Speed Inputs: 3 × magnetic pickups (MPUs)
• Voting: Two-out-of-three (2oo3) relay voting
• Sample Time: every 5 ms
• Total Response Time: 40 ms max
• Display: Front-panel digital displays + LEDs (speed per probe, highest speed, status)
• Testing: On-line testing of each unit with built-in frequency generator; remote reset supported
• Enclosure: NEMA Type 4 / 4X (North America); IP54 (Europe); per manual 85205
• Origin: United States (Woodward)

Installation Notes

1. Read Woodward manual 82715 (handling and protection of electronic controls) before installation, handling, or adjustment.
2. Connect each unit’s 24 V DC supply (18–32 V) with the correct polarity; note the de-energize-to-trip wiring (loss of supply energizes the trip path).
3. Configure trip speed setpoint and MPU parameters via each unit’s front-panel interface; verify with the on-line test function.
4. Perform a full trip test (2oo3 voting behavior, response ≤40 ms) before placing the prime mover in service; replace any failed unit online using the modular design.

Common Questions

What does “de-energize-to-trip” mean? The 9907-147 trips the prime mover on loss of power — the fail-safe configuration Woodward recommends, so a supply failure cannot leave the machine unprotected.

Why three units and two-out-of-three voting? Three independent speed-sensing units with 2oo3 voting ensure that a single failed unit (e.g., one MPU or circuit) cannot both miss a genuine overspeed and falsely trip the machine.

What power does each unit need? 24 V DC (18–32 V), 5.12 W per unit — the 9907-147 has three 24 V DC-powered kernels.

How fast does it respond? Speed is sampled every 5 ms, with a total response time of 40 ms maximum.