Overview

The Triconex 3721N is a Nuclear-qualified Analog Input Module designed for use in Tricon V10 TMR (Triple Modular Redundant) safety systems. It provides high-density signal processing for a wide range of analog inputs, supporting both 0 to 5 VDC and -5 to +5 VDC input ranges. With a unique triplicated architecture, this module ensures unparalleled fault tolerance and system integrity, making it ideal for safety-critical applications in nuclear power plants.

In a TMR configuration, the 3721N utilizes three independent processing channels to handle each input signal. The module ensures that even in the case of a component failure, the system can continue to operate reliably through its self-diagnostic and voting mechanism.

Key Features & Functions

1. Triple Modular Redundant (TMR) Architecture

• Each input signal is processed independently by three channels. The Tricon system compares the outputs of all three channels, ensuring that any discrepancies are detected and isolated. If one channel provides faulty data, the system "votes out" the faulty branch and continues to function with the remaining healthy channels. This enhances system safety and availability, even in the event of a hardware failure.

2. Comprehensive Self-Diagnostics

• Reference Voltage Checks: Verifies the accuracy of the Analog-to-Digital Converters (A/D).

• Stuck-Bit Detection: Ensures that the A/D converters are dynamically producing valid digital data.

• Input Path Testing: Monitors the integrity of the wiring from the field terminal to the module’s internal components, helping to detect wiring issues.

• The 3721N is equipped with advanced diagnostic capabilities, including:

3. Nuclear Qualification (N-Series)

• Seismic Events: Rated for Category I seismic events to ensure reliable operation during earthquakes.

• Environmental Aging: Tested for long-term durability in harsh plant conditions, including exposure to high levels of radiation.

• Radiation Hardening: Engineered to handle radiation levels common in nuclear containment areas and auxiliary buildings.

• The 3721N is designed to meet the rigorous standards of the nuclear industry. It is qualified for 1E safety-related applications and is built to withstand:

4. High Input Accuracy

• With a 12-bit resolution and an accuracy of < 0.15% of FSR (Full Scale Range) from 0 to 60°C, the 3721N ensures high-precision data acquisition from external sensors.

5. User-Friendly Front Panel Indicators

• PASS: Green LED lights up when the module passes all internal power-up and runtime diagnostics.

• FAULT: Red LED indicates a failure within one of the internal channels.

• ACTIVE: Yellow LED shows the module is actively communicating with the main processors.

• The 3721N features a set of LED indicators for real-time status monitoring:

Technical Specifications

Applications

The Triconex 3721N is ideally suited for nuclear power plants, particularly in safety-critical systems requiring precise and reliable analog data acquisition. Its triplicated input channels and comprehensive diagnostics make it the perfect choice for high-availability systems in environments subject to harsh conditions, such as radiation and seismic activity.

Installation & Maintenance

• The 3721N is designed to fit seamlessly into the Tricon V10 safety system and can be installed in a standard chassis.

• The front panel provides real-time diagnostics, allowing engineers to monitor the system’s health and respond promptly to potential issues.

FAQ

Q1: How does the 3721N ensure fault tolerance?
A1: The 3721N uses a TMR architecture, where each input signal is processed by three independent channels. The system compares the results from all three and "votes out" any faulty channel, ensuring that only reliable data is used, even if one channel fails.

Q2: Is the 3721N suitable for nuclear applications?
A2: Yes, the 3721N is Nuclear-qualified, meeting all seismic, environmental, and radiation exposure requirements for 1E safety-related applications in nuclear power plants.

Q3: What input types does the 3721N support?
A3: The module supports analog differential input signals, offering a choice between 0 to 5 VDC or -5 to +5 VDC input ranges, suitable for a wide range of sensors.