Description

Woodward 9907-147

1. Basic Information

Woodward 9907-147 is a triple redundant overspeed protection module of the Woodward ProTech series, specially designed for prime movers such as steam turbines, gas turbines and internal combustion engines. Adopting a 2-out-of-3 (2/3) voting redundant architecture with three independent magnetic pickup speed measurement channels, it eliminates mis-trip and fail-to-trip risks caused by single-channel faults, serving as the final safety barrier for prime mover overspeed faults.

Designed with a fail-safe power-off trip mechanism, the relay is normally energized and will disconnect to trigger shutdown under power loss, signal failure or overspeed conditions, fully complying with industrial rotating machinery safety standards. It features high-precision speed monitoring, programmable overspeed threshold, millisecond-level rapid response, channel self-diagnosis and fault lock memory. Widely applied in land-based generator sets, industrial drive turbines and reciprocating power equipment, it is commonly used for new unit matching, old protection system upgrading and safety redundant renovation.

2. Technical Specifications

2.1 Core Speed Monitoring Specifications

Operation Architecture: 3-channel independent speed acquisition + 2/3 redundant voting logic, no single-point failure
Speed Detection Mode: Compatible with magnetic pickup (MPU) sensors, 3 independent input channels, single-channel impedance 2kΩ
Frequency Monitoring Range: 100Hz～32kHz, corresponding speed 100rpm～20000rpm, covering most industrial prime mover operating conditions
Overspeed Trip Range: 250Hz～25kHz, programmable threshold via operator interface with synchronous calibration for three channels
Response Time: ＜20ms ultra-fast response to ensure emergency shutdown before equipment damage
Measurement Accuracy: High-frequency high-precision sampling, no misjudgment caused by speed jitter, excellent long-term stability

2.2 Electrical Power Specifications

Power Supply: 24VDC industrial power supply, adaptive range 18VDC～32VDC
Power Consumption: Rated 5.12W, low heat generation for long-term cabinet operation
Safety Mechanism: Fail-safe power-off trip design, safe shutdown triggered by power loss, signal loss, module fault and overspeed
Protection Circuit: Built-in over-voltage, over-current, reverse polarity and surge protection for complex industrial power environments

2.3 Communication & Output Specifications

Communication Interface: RS232/RS485 serial port, supporting Modbus RTU protocol for upper system connection
Analog Output: 4-20mA speed analog signal output for real-time speed transmission to DCS/PLC
Trip Output: Passive relay dry contact output, directly connected to unit interlock shutdown loop
Status Feedback: Real-time output of module operation, channel fault, alarm and trip status

2.4 Diagnosis & Functional Specifications

Power-on Self-test: Full self-inspection of three channels, chips, communication and power circuits after power-on
Real-time Channel Diagnosis: Continuously monitors MPU disconnection, insufficient signal amplitude and channel abnormality
Fault Lock & Memory: Automatically locks trip status and saves fault records after overspeed action, requiring manual reset
Delay Configuration: Programmable overspeed trip delay to adapt to different process protection logics
Status Indication: Onboard LED indicators for operation, fault, overspeed and trip status visualization

2.5 Environmental & Physical Specifications

Operating Temperature: -20℃～+70℃, suitable for long-term closed cabinet operation
Storage Temperature: -40℃～+85℃, excellent temperature shock resistance
Humidity Range: 5%～95%RH (non-condensing), dust-proof and moisture-proof
EMC Performance: High-standard industrial anti-interference design against frequency conversion and electromagnetic interference
Dimensions: 184mm×133mm×64mm, standard rack-mounted structure
Weight: Approx. 2.5kg, vibration-resistant and stable for long-term operation

3. Working Principle

Power-on Initialization & Self-test: After 24VDC power-on, the module completes hardware self-inspection, three-channel initialization, protocol loading and parameter verification. The relay energizes and enters normal monitoring standby state after passing self-test.
Three-channel Independent Speed Acquisition: Three independent MPU channels synchronously collect prime mover gear pulse signals, convert mechanical speed into high-frequency electrical signals, and complete signal denoising and shaping for accurate sampling.
2/3 Redundant Voting Logic: The module compares real-time speed data of three channels and adopts 2-out-of-3 voting logic. An overspeed fault is confirmed when no less than two channels detect over-limit speed, avoiding mis-operation caused by single-channel failure.
Fail-safe Trip Output: Once overspeed is confirmed, the internal safety relay disconnects instantly to output trip signal and trigger unit emergency shutdown. Meanwhile, the fault status is locked with trip data recorded.
Real-time Data Upload & Status Monitoring: Real-time speed value and module health status are uploaded to the upper DCS system via analog and serial ports, with panel LED status updated synchronously for local and remote monitoring.
Fault Tolerance & Status Lock: Single-channel abnormality only triggers alarm without shutdown to ensure continuous unit operation. Overspeed and critical faults lock the system permanently, requiring manual reset to avoid fault re-investment risks.

4. Application Scenarios

4.1 Steam & Gas Turbine Overspeed Safety Protection

As the core ultimate safety protection unit for generator sets and industrial turbines, it prevents major accidents such as unit runaway, shaft damage and equipment explosion, serving as a mandatory safety component for power unit safety supervision.

4.2 Internal Combustion Engine & Reciprocating Power Unit Protection

Suitable for speed monitoring and overspeed protection of large diesel generator sets, biogas generator sets and reciprocating driving equipment. Its wide speed range, fast response and redundant logic ensure stable operation of power equipment.

4.3 High-reliability Redundant Safety Control System

With 2/3 redundant architecture and fail-safe design, it adapts to key continuous production units in petroleum, chemical and power industries, eliminating single-point faults in speed monitoring and protection loops and meeting high-level equipment safety certification requirements.

4.4 Old Unit Protection System Upgrading

Compatible with old single/dual-channel overspeed protection devices, upgrading to triple redundant safety architecture. It matches original MPU sensors and shutdown loops, realizing low-cost and high-reliability system renovation.

4.5 Power Equipment Condition Monitoring System

It outputs high-precision real-time speed analog signals to provide accurate data support for unit vibration analysis, load regulation, fault diagnosis and efficiency evaluation, integrating safety protection and equipment operation monitoring functions.