The IS200VCRCH1B is a high-performance discrete (digital) input/output board and a critical component of the GE Mark VI turbine control system. It is a single-slot optimized version of the classic dual-slot VCCC board, offering complete functional equivalence while occupying only a single standard VME slot through innovative compact design, significantly improving cabinet space utilization. The IS200VCRCH1B is specifically designed for high-reliability switch status monitoring and relay driving applications in industrial control, widely used in gas turbines, steam turbines, and other critical industrial equipment for sequence control, protective interlocking, and status monitoring systems.
The core capability of IS200VCRCH1B lies in processing 48 discrete inputs and controlling 24 relay outputs. It connects to field devices (such as limit switches, pressure switches, pushbuttons, solenoids, contactors, etc.) via terminal boards (TBCI for inputs, TRLY for outputs), enabling reliable, isolated digital signal interaction between the control system and the physical world. The board supports Triple Modular Redundancy (TMR) architecture and provides high-precision Sequence of Events (SOE) recording functionality, making it an ideal choice for building highly available and safe control systems.
II. Architecture and Design Highlights
1. Single-Slot Compact Design
Core Advantage: The most significant design highlight of IS200VCRCH1B is its single-slot width (1.99 cm). Compared to the dual-slot VCCC (3.98 cm), it saves 50% of rack space while providing equivalent functionality. This is crucial for applications with dense I/O points and limited cabinet space.
Integrated Structure: IS200VCRCH1B does not require the daughterboard used by VCCC. To achieve the single-slot design, the dry contact input interfaces originally located on the daughterboard have been moved to the front panel of the board, receiving cables from TBCI terminal boards via two dedicated front connectors (J33 and J44).
Consistent Output Connection: The connection method for relay outputs (TRLY) remains completely consistent with VCCC, continuing to use the standard J3 and J4 connectors at the bottom of the VME rack. This ensures compatibility with existing wiring and terminal boards, simplifying the upgrade process.
2. Functional Equivalence with VCCC and Selection Guide
IS200VCRCH1B is identical to VCCC in terms of electrical performance, software functionality, configuration parameters, and diagnostic characteristics. The choice between them is primarily based on physical installation requirements:
Choose IS200VCRCH1B: When the project has strict requirements for rack space utilization and can accept input cables being connected from the front panel of the board.
Choose VCCC: When it is desirable for all I/O cables to be routed uniformly from the bottom of the VME rack to maintain neat and uniform cabinet wiring, or when the system needs to use the TICI Contact Voltage Sensing Board (VCRC does not support TICI).
III. Detailed Core Functions and Working Principles
1. Discrete Input Function (48 Dry Contacts)
Signal Acquisition: IS200VCRCH1B accepts dry contact (passive contact) signals from the field, such as the opening and closing of switches. Each TBCI terminal board handles 24 inputs, therefore two TBCI boards are required to support all 48 inputs.
Excitation Power: Provides operating voltage for the dry contacts. Supports two specifications of floating DC power, implemented by selecting different TBCI terminal board models:
TBCIH1: Provides 125 V DC excitation (range 100-145 V DC), suitable for long-distance transmission and environments requiring strong noise immunity.
TBCIH2: Provides 24 V DC excitation (range 18.5-32 V DC), a more common industrial standard.
Signal Conditioning and Isolation:
Optical Isolation: Input signals first pass through opto-isolators, providing up to 1500 V electrical isolation between the field side and the control side. This effectively prevents damage to core control system components from ground potential differences, surges, and high-voltage intrusion.
Hardware Filtering: Each input is equipped with a 4-millisecond hardware filter. This filter effectively suppresses high-frequency noise, contact bounce (debounce), and transient surges, ensuring signal stability and reliability.
AC Rejection: With 125V DC excitation, it possesses strong power frequency AC rejection capability (60 V RMS @ 50/60 Hz), preventing false triggering caused by induced AC voltages in the field.
High-Speed Scanning and SOE Recording:
Control Scanning: Input status is sampled at the system frame rate (determined by the controller) for routine logic control.
SOE Scanning: To accurately record the sequence of fault events, VCRC can sample all inputs at an extremely high speed of 1 millisecond (1000 Hz). Any opening or closing change of a contact is time-stamped with precision (1ms resolution) and recorded for reporting. The system can reliably detect and report pulses or contact chatter as short as 6 milliseconds, providing precise timing clues for incident analysis.
2. Relay Output Function (24 Channels)
Output Structure: Each TRLYH1B terminal board houses 12 plug-in magnetic relays. Therefore, controlling all 24 outputs requires two TRLY boards.
Contact Form and Configuration:
Dry Contact Output: Pure, isolated Form-C (Normally Open, Normally Closed, Common) contacts for controlling external circuits.
Drive External Solenoids: The board can provide power for field solenoids. The power type (125 V DC / 115 V AC or optional 24 V DC), fuses, and on-board suppression circuits can be selected via jumpers.
First 6 Relays (1-6): Can be flexibly configured via jumpers as either:
Relays 7-11: Provide 5 channels of isolated, unpowered Form-C dry contacts.
Relay 12: A special isolated Form-C contact, typically used for demanding loads like ignition transformers.
Driving and Monitoring: IS200VCRCH1B sends relay coil drive commands to the TRLY board via cables. Simultaneously, the cables also return relay contact voltage feedback signals, enabling VCRC to monitor the actual physical state of the contacts (whether they are truly energized or de-energized).
Fail-Safe Design:
Cable Disconnect Protection: If the cable connecting VCRC and TRLY is accidentally disconnected, the system detects the communication loss and automatically de-energizes all affected relays, ensuring the equipment enters a safe state.
Communication Loss Protection: If communication is lost between the VCRC board and the superior controller (VCMI), it similarly triggers relay de-energization.
State Disagreement Diagnostics: VCRC continuously compares the output command with the coil current/contact feedback status. Any disagreement (e.g., command to close but contact not closed) immediately generates a diagnostic alarm.
3. Triple Modular Redundancy (TMR) Support
IS200VCRCH1B can be seamlessly integrated into TMR control systems, providing the highest level of availability:
Input Redundancy: In a TMR system, the same set of dry contact signals from the field are "fanned out" via the JR1, JS1, JT1 connectors on the TBCI terminal board to three VCRC boards located in separate R, S, T VME racks.
Signal Voting: The three VCRC boards independently sample and process the input signals. The processed results are sent via the VME backplane to the VCMI board in each rack, where the three controllers perform 2-out-of-3 median voting to eliminate sporadic errors from any single path.
Output Redundancy and Fault Tolerance: For relay outputs, the three sets of controllers generate consistent control commands through voting and send them to the VCRC in their respective racks. The relay status driven by VCRC is similarly monitored and compared. Any fault in a single channel (e.g., board, cable failure) can be identified and isolated by the system, ensuring the correctness of output actions.
IV. System Integration, Diagnostics, and Configuration
1. System Connection Diagram
Simplex System: Input signals from the two TBCI terminal boards are connected to VCRC via front connectors J33 and J44. Control signals for the two TRLY terminal boards are connected via the standard J3 and J4 connectors at the bottom of the VME rack. VCRC processes all signals and communicates with the VCMI/controller via the VME backplane.
TMR System: Input signals are fanned out from the JR1, JS1, JT1 connectors of the TBCI terminal boards to the VCRC boards in the three racks. The JA1 connector is left open. On the output side, VCRC boards in the three racks control their respective TRLY boards, and the system ensures final action consistency through logical voting.
2. Comprehensive Diagnostics and Monitoring
VCRC features multi-level diagnostic capabilities:
Board-Level Status LEDs: RUN/FAIL/STAT indicators provide quick health status judgment.
Composite Diagnostic Alarm: Any channel fault triggers an L3DIAG_VCCCx alarm, with specific details viewable in the Toolbox.
Input Diagnostics: Monitors whether the input excitation power is normal and can force-check the responsiveness of each input channel in "Test Mode."
Output Diagnostics: Monitors relay coil drive status, coil current, contact feedback voltage, and solenoid power fuse status in real-time. Any command-feedback mismatch, fuse blow, or communication interruption is immediately detected.
Hardware Identification (ID): All terminal board cable connectors have built-in read-only ID chips. VCRC verifies ID information (serial number, board type, revision, location) during startup and operation, preventing incorrect hardware combinations and ensuring system compatibility.
3. Flexible Software Configuration
The Mark VI Toolbox allows fine-grained configuration of VCRC. Key parameters include:
System Settings: Enable/disable system limit checking.
Relay Channel Configuration: Define whether each relay is enabled, its associated feedback point, whether fuse diagnostics are enabled, etc.
Input Channel Configuration:
Define whether each input point is enabled.
Signal Inversion: Define "contact closed" as logic "true" or "false" as needed.
Software Filtering: In addition to hardware filtering, additional software filter time constants of 0, 10, 20, 50 ms can be selected.
SOE Enable: Specify which critical input points participate in the 1ms high-speed SOE recording.
Connection Status Declaration: Declare the terminal board type and connection status for J3, J4, J3A(J33), J4A(J44).
4. Typical Fault Codes (Examples)
Fault 22/23: Front input connector (J33/J44 or their corresponding locations) ID chip failure or cable problem.
Fault 33-56, 65-88: Specific input channel(s) not responding in Test Mode, possibly due to board issue, missing TBCI reference voltage, or cable fault.
Fault 129-140, 145-156: Specific relay coil state does not match command, possibly due to missing relay board, relay itself fault, or being out-voted by the other two paths in a TMR system.
Fault 240/241: TBCI input excitation voltage invalid, all related input points unreliable. Possible causes: terminal board not powered, cable unplugged, or voltage too low.
